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packet-q931.c

/* packet-q931.c
 * Routines for Q.931 frame disassembly
 * Guy Harris <guy@alum.mit.edu>
 *
 * $Id: packet-q931.c 19275 2006-09-21 19:39:42Z etxrab $
 *
 * Modified by Andreas Sikkema for possible use with H.323
 *
 * Wireshark - Network traffic analyzer
 * By Gerald Combs <gerald@wireshark.org>
 * Copyright 1998
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <stdio.h>
#include <glib.h>
#include <string.h>
#include <epan/packet.h>
#include <epan/tap.h>
#include <epan/strutil.h>
#include <epan/nlpid.h>
#include "packet-q931.h"
#include "packet-e164.h"
#include <epan/prefs.h>
#include <epan/reassemble.h>
#include <epan/emem.h>

#include <epan/lapd_sapi.h>
#include "packet-tpkt.h"

#ifndef min
#define min(a,b) (((a)<(b))?(a):(b))
#endif

/* Q.931 references:
 *
 * http://www.acacia-net.com/Clarinet/Protocol/q9313svn.htm
 * http://www.acacia-net.com/Clarinet/Protocol/q9311sc3.htm
 * http://www.acacia-net.com/Clarinet/Protocol/q9317oz7.htm
 * http://www.protocols.com/pbook/isdn.htm
 * http://freesoft.org/CIE/Topics/126.htm
 * http://noc.comstar.ru/miscdocs/ascend-faq-cause-codes.html
 * http://www.andrews-arnold.co.uk/isdn/q931cause.html
 * http://www.tulatelecom.ru/staff/german/DSSHelp/MessList/InfEl/InfElList.html
 */
static void reset_q931_packet_info(q931_packet_info *pi);
static gboolean have_valid_q931_pi=FALSE;
static q931_packet_info *q931_pi=NULL;
static int q931_tap = -1;

static int proto_q931                           = -1;
static int hf_q931_discriminator                = -1;
static int hf_q931_coding_standard              = -1;
static int hf_q931_information_transfer_capability    = -1;
static int hf_q931_transfer_mode                = -1;
static int hf_q931_information_transfer_rate          = -1;
static int hf_q931_uil1                         = -1;
static int hf_q931_call_ref_len                 = -1;
static int hf_q931_call_ref_flag                = -1;
static int hf_q931_call_ref                     = -1;
static int hf_q931_message_type                 = -1;
static int hf_q931_segment_type                 = -1;
static int hf_q931_cause_location               = -1;
static int hf_q931_cause_value                        = -1;
static int hf_q931_number_type                        = -1;
static int hf_q931_numbering_plan               = -1;
static int hf_q931_extension_ind                = -1;
static int hf_q931_calling_party_number         = -1;
static int hf_q931_called_party_number                = -1;
static int hf_q931_connected_number                   = -1;
static int hf_q931_redirecting_number                 = -1;
static int hf_q931_screening_ind                      = -1;
static int hf_q931_presentation_ind                   = -1;

/* fields for Channel Indentification IE */
static int hf_q931_channel_interface_explicit         = -1;
static int hf_q931_channel_interface_type       = -1;
static int hf_q931_channel_exclusive                  = -1;
static int hf_q931_channel_dchan                = -1;
static int hf_q931_channel_selection_bri        = -1;
static int hf_q931_channel_selection_pri        = -1;
static int hf_q931_channel_map                        = -1;
static int hf_q931_channel_element_type               = -1;
static int hf_q931_channel_number               = -1;


static int hf_q931_segments = -1;
static int hf_q931_segment = -1;
static int hf_q931_segment_overlap = -1;
static int hf_q931_segment_overlap_conflict = -1;
static int hf_q931_segment_multiple_tails = -1;
static int hf_q931_segment_too_long_segment = -1;
static int hf_q931_segment_error = -1;
static int hf_q931_reassembled_in = -1; 

static gint ett_q931                            = -1;
static gint ett_q931_ie                         = -1;

static gint ett_q931_segments = -1;
static gint ett_q931_segment = -1;

static const fragment_items q931_frag_items = {
      &ett_q931_segment,
      &ett_q931_segments,

      &hf_q931_segments,
      &hf_q931_segment,
      &hf_q931_segment_overlap,
      &hf_q931_segment_overlap_conflict,
      &hf_q931_segment_multiple_tails,
      &hf_q931_segment_too_long_segment,
      &hf_q931_segment_error,
      &hf_q931_reassembled_in,
      "segments"
};

/* Tables for reassembly of fragments. */
static GHashTable *q931_fragment_table = NULL;
static GHashTable *q931_reassembled_table = NULL;

/* Preferences */
static gboolean q931_reassembly = TRUE;

static dissector_table_t codeset_dissector_table;
static dissector_table_t ie_dissector_table;

/* desegmentation of Q.931 over TPKT over TCP */
static gboolean q931_desegment = TRUE;

static dissector_handle_t h225_handle;
static dissector_handle_t q931_tpkt_handle;
static dissector_handle_t q931_tpkt_pdu_handle;

static void
dissect_q931_IEs(tvbuff_t *tvb, packet_info *pinfo, proto_tree *root_tree,
    proto_tree *q931_tree, gboolean is_tpkt, int offset, int initial_codeset);

const value_string q931_message_type_vals[] = {
      { Q931_ESCAPE,                "ESCAPE" },
      { Q931_ALERTING,        "ALERTING" },
      { Q931_CALL_PROCEEDING,       "CALL PROCEEDING" },
      { Q931_CONNECT,               "CONNECT" },
      { Q931_CONNECT_ACK,           "CONNECT ACKNOWLEDGE" },
      { Q931_PROGRESS,        "PROGRESS" },
      { Q931_SETUP,                 "SETUP" },
      { Q931_SETUP_ACK,       "SETUP ACKNOWLEDGE" },
      { Q931_HOLD,                  "HOLD" },
      { Q931_HOLD_ACK,        "HOLD_ACKNOWLEDGE" },
      { Q931_HOLD_REJECT,           "HOLD_REJECT" },
      { Q931_RESUME,                "RESUME" },
      { Q931_RESUME_ACK,            "RESUME ACKNOWLEDGE" },
      { Q931_RESUME_REJECT,         "RESUME REJECT" },
      { Q931_RETRIEVE,        "RETRIEVE" },
      { Q931_RETRIEVE_ACK,          "RETRIEVE ACKNOWLEDGE" },
      { Q931_RETRIEVE_REJECT,       "RETRIEVE REJECT" },
      { Q931_SUSPEND,               "SUSPEND" },
      { Q931_SUSPEND_ACK,           "SUSPEND ACKNOWLEDGE" },
      { Q931_SUSPEND_REJECT,        "SUSPEND REJECT" },
      { Q931_USER_INFORMATION,      "USER INFORMATION" },
      { Q931_DISCONNECT,            "DISCONNECT" },
      { Q931_RELEASE,               "RELEASE" },
      { Q931_RELEASE_COMPLETE,      "RELEASE COMPLETE" },
      { Q931_RESTART,               "RESTART" },
      { Q931_RESTART_ACK,           "RESTART ACKNOWLEDGE" },
      { Q931_CONGESTION_CONTROL,    "CONGESTION CONTROL" },
      { Q931_FACILITY,        "FACILITY" },
      { Q931_INFORMATION,           "INFORMATION" },
      { Q931_NOTIFY,                "NOTIFY" },
      { Q931_REGISTER,        "REGISTER" },
      { Q931_SEGMENT,               "SEGMENT" },
      { Q931_STATUS,                "STATUS" },
      { Q931_STATUS_ENQUIRY,        "STATUS ENQUIRY" },
      { Q931_VERSION,               "VERSION" },
      { Q931_GROUIP_SERVICE,        "GROUP SERVICE" },
      { Q931_GROUIP_SERVICE_ACK,    "GROUP SERVICE ACK" },
      { Q931_RESYNC_REQ,            "RESYNC REQ" },
      { Q931_RESYNC_RESP,           "RESYNC RESP" },
      { 0,                    NULL }
};

/*
 * NOTE  For call reference flag (octet 2)
 * Bit8
 *    0 The message is sent from the side that originates the call reference
 *    1 The message is sent to the side that originates the call reference
 */
static const true_false_string tfs_call_ref_flag = {
      "Message sent to originating side",
      "Message sent from originating side"
};

static const true_false_string tfs_interface_type = {
    "Primary rate interface",
    "Basic rate interface"
};

static const true_false_string tfs_channel_exclusive = {
      "Exclusive; only the indicated channel is acceptable",
      "Indicated channel is preferred"
};

static const true_false_string tfs_channel_map = {
      "Channel indicated by slot map",
      "Channel indicated by number"
};

/*
 * Information elements.
 */

/* Shifted codeset values */
#define CS0 0x000
#define CS1 0x100
#define CS2 0x200
#define CS3 0x300
#define CS4 0x400
#define CS5 0x500
#define CS6 0x600
#define CS7 0x700

#define     Q931_IE_SO_MASK   0x80  /* single-octet/variable-length mask */
/*
 * Single-octet IEs.
 */
#define     Q931_IE_SO_IDENTIFIER_MASK    0xf0  /* IE identifier mask */
#define     Q931_IE_SO_IDENTIFIER_SHIFT   4     /* IE identifier shift */
#define     Q931_IE_SO_IE_MASK            0x0F  /* IE mask */

#define     Q931_IE_SHIFT                 0x90
#define     Q931_IE_SHIFT_NON_LOCKING     0x08  /* non-locking shift */
#define     Q931_IE_SHIFT_CODESET         0x07  /* codeset */

#define     Q931_IE_MORE_DATA_OR_SEND_COMP      0xA0  /* More Data or Sending Complete */
#define     Q931_IE_MORE_DATA       0xA0
#define     Q931_IE_SENDING_COMPLETE      0xA1

#define     Q931_IE_CONGESTION_LEVEL      0xB0
#define     Q931_IE_REPEAT_INDICATOR      0xD0

/*
 * Variable-length IEs.
 */
#define     Q931_IE_VL_EXTENSION          0x80  /* Extension flag */
/*    extension bit. The bit value "0" indicates that the octet continues through the           */
/*    next octet. The bit value "1" indicates that this octet is the last octet           */

static const true_false_string q931_extension_ind_value = {
  "last octet",
  "information continues through the next octet",

};


/*
 * Codeset 0 (default).
 */
#define     Q931_IE_SEGMENTED_MESSAGE     0x00
#define     Q931_IE_BEARER_CAPABILITY     0x04
#define     Q931_IE_CAUSE                 0x08
#define     Q931_IE_CALL_IDENTITY         0x10
#define     Q931_IE_CALL_STATE            0x14
#define     Q931_IE_CHANNEL_IDENTIFICATION      0x18
#define     Q931_IE_FACILITY        0x1C
#define     Q931_IE_PROGRESS_INDICATOR    0x1E
#define     Q931_IE_NETWORK_SPECIFIC_FACIL      0x20  /* Network Specific Facilities */
#define     Q931_IE_NOTIFICATION_INDICATOR      0x27
#define     Q931_IE_DISPLAY               0x28
#define     Q931_IE_DATE_TIME       0x29
#define     Q931_IE_KEYPAD_FACILITY       0x2C
#define     Q931_IE_INFORMATION_REQUEST   0x32
#define     Q931_IE_SIGNAL                0x34
#define     Q931_IE_SWITCHHOOK            0x36
#define     Q931_IE_FEATURE_ACTIVATION    0x38
#define     Q931_IE_FEATURE_INDICATION    0x39
#define     Q931_IE_ENDPOINT_IDENTIFIER   0x3B
#define     Q931_IE_SERVICE_PROFILE_ID    0x3A
#define     Q931_IE_INFORMATION_RATE      0x40
#define     Q931_IE_E2E_TRANSIT_DELAY     0x42  /* End-to-end Transit Delay */
#define     Q931_IE_TD_SELECTION_AND_INT  0x43  /* Transit Delay Selection and Indication */
#define     Q931_IE_PL_BINARY_PARAMETERS  0x44  /* Packet layer binary parameters */
#define     Q931_IE_PL_WINDOW_SIZE        0x45  /* Packet layer window size */
#define     Q931_IE_PACKET_SIZE           0x46  /* Packet size */
#define     Q931_IE_CUG             0x47  /* Closed user group */
#define     Q931_IE_REVERSE_CHARGE_IND    0x4A  /* Reverse charging indication */
#define     Q931_IE_CONNECTED_NUMBER_DEFAULT        0x4C    /* Connected Number */
#define     Q931_IE_INTERFACE_SERVICE     0x66  /* q931+ Interface Service */
#define     Q931_IE_CHANNEL_STATUS        0x67  /* q931+ Channel Status */
#define     Q931_IE_VERSION_INFO          0x68  /* q931+ Version Info */
#define     Q931_IE_CALLING_PARTY_NUMBER  0x6C  /* Calling Party Number */
#define     Q931_IE_CALLING_PARTY_SUBADDR 0x6D  /* Calling Party Subaddress */
#define     Q931_IE_CALLED_PARTY_NUMBER   0x70  /* Called Party Number */
#define     Q931_IE_CALLED_PARTY_SUBADDR  0x71  /* Called Party Subaddress */
#define     Q931_IE_REDIRECTING_NUMBER    0x74
#define     Q931_IE_REDIRECTION_NUMBER    0x76
#define     Q931_IE_TRANSIT_NETWORK_SEL   0x78  /* Transit Network Selection */
#define     Q931_IE_RESTART_INDICATOR     0x79
#define     Q931_IE_LOW_LAYER_COMPAT      0x7C  /* Low-Layer Compatibility */
#define     Q931_IE_HIGH_LAYER_COMPAT     0x7D  /* High-Layer Compatibility */
#define     Q931_IE_USER_USER       0x7E  /* User-User */
#define     Q931_IE_ESCAPE                0x7F  /* Escape for extension */

/*
 * Codeset 0 ETSI.
 */
#define     Q931_IE_CONNECTED_NUMBER      0x8C
#define     Q931_IE_CONNECTED_SUBADDR     0x8D

/*
 * Codeset 5 (National-specific) Belgium.
 */
#define     Q931_IE_CHARGING_ADVICE       0x1A

/*
 * Codeset 5 (National-specific) Bellcore National ISDN.
 */
#define     Q931_IE_OPERATOR_SYSTEM_ACCESS      0x1D

/*
 * Codeset 6 (Network-specific) Belgium.
 */
/* 0x1A is Charging Advice, as with Codeset 5 */
#define     Q931_IE_REDIRECTING_NUMBER    0x74

/*
 * Codeset 6 (Network-specific) FT-Numeris.
 */
/* 0x1D is User Capability */

/*
 * Codeset 6 (Network-specific) Bellcore National ISDN.
 */
#define     Q931_IE_REDIRECTING_SUBADDR   0x75  /* Redirecting Subaddress */
/* 0x76 is Redirection Number, but that's also Codeset 0 */
#define     Q931_IE_CALL_APPEARANCE       0x7B

/* Codeset 0 */
static const value_string q931_info_element_vals0[] = {
      { Q931_IE_SEGMENTED_MESSAGE,        "Segmented message" },
      { Q931_IE_BEARER_CAPABILITY,        "Bearer capability" },
      { Q931_IE_CAUSE,              "Cause" },
      { Q931_IE_CALL_IDENTITY,            "Call identity" },
      { Q931_IE_CALL_STATE,               "Call state" },
      { Q931_IE_CHANNEL_IDENTIFICATION,   "Channel identification" },
      { Q931_IE_FACILITY,                 "Facility" },
      { Q931_IE_PROGRESS_INDICATOR,       "Progress indicator" },
      { Q931_IE_NETWORK_SPECIFIC_FACIL,   "Network specific facilities" },
      { Q931_IE_NOTIFICATION_INDICATOR,   "Notification indicator" },
      { Q931_IE_DISPLAY,                  "Display" },
      { Q931_IE_DATE_TIME,                "Date/Time" },
      { Q931_IE_KEYPAD_FACILITY,          "Keypad facility" },
      { Q931_IE_INFORMATION_REQUEST,            "Information request" },
      { Q931_IE_SIGNAL,             "Signal" },
      { Q931_IE_SWITCHHOOK,               "Switchhook" },
      { Q931_IE_FEATURE_ACTIVATION,       "Feature activation" },
      { Q931_IE_FEATURE_INDICATION,       "Feature Indication" },
      { Q931_IE_ENDPOINT_IDENTIFIER,            "Endpoint identifier" },
      { Q931_IE_SERVICE_PROFILE_ID,       "Service profile ID" },
      { Q931_IE_INFORMATION_RATE,         "Information rate" },
      { Q931_IE_E2E_TRANSIT_DELAY,        "End-to-end transit delay" },
      { Q931_IE_TD_SELECTION_AND_INT,           "Transit delay selection and indication" },
      { Q931_IE_PL_BINARY_PARAMETERS,           "Packet layer binary parameters" },
      { Q931_IE_PL_WINDOW_SIZE,           "Packet layer window size" },
      { Q931_IE_PACKET_SIZE,              "Packet size" },
      { Q931_IE_CUG,                      "Closed user group" },
      { Q931_IE_REVERSE_CHARGE_IND,       "Reverse charging indication" },
      { Q931_IE_CONNECTED_NUMBER_DEFAULT,     "Connected number" },
      { Q931_IE_INTERFACE_SERVICE,        "Interface Service" },
      { Q931_IE_CHANNEL_STATUS,           "Channel Status" },
      { Q931_IE_VERSION_INFO,             "Version Info" },
      { Q931_IE_CALLING_PARTY_NUMBER,           "Calling party number" },
      { Q931_IE_CALLING_PARTY_SUBADDR,    "Calling party subaddress" },
      { Q931_IE_CALLED_PARTY_NUMBER,            "Called party number" },
      { Q931_IE_CALLED_PARTY_SUBADDR,           "Called party subaddress" },
      { Q931_IE_REDIRECTING_NUMBER,       "Redirecting number" },
      { Q931_IE_REDIRECTION_NUMBER,       "Redirection number" },
      { Q931_IE_TRANSIT_NETWORK_SEL,            "Transit network selection" },
      { Q931_IE_RESTART_INDICATOR,        "Restart indicator" },
      { Q931_IE_LOW_LAYER_COMPAT,         "Low-layer compatibility" },
      { Q931_IE_HIGH_LAYER_COMPAT,        "High-layer compatibility" },
      { Q931_IE_USER_USER,                "User-user" },
      { Q931_IE_ESCAPE,             "Escape" },
      { Q931_IE_CONNECTED_NUMBER,         "Connected number" },
      { Q931_IE_CONNECTED_SUBADDR,        "Connected subaddress" },
      { 0,                          NULL }
};
/* Codeset 1 */
static const value_string q931_info_element_vals1[] = {
      { 0,                          NULL }
};
/* Codeset 2 */
static const value_string q931_info_element_vals2[] = {
      { 0,                          NULL }
};
/* Codeset 3 */
static const value_string q931_info_element_vals3[] = {
      { 0,                          NULL }
};
/* Codeset 4 */
static const value_string q931_info_element_vals4[] = {
      { 0,                          NULL }
};
/* Codeset 5 */
static const value_string q931_info_element_vals5[] = {
      { Q931_IE_CHARGING_ADVICE,          "Charging advice" },
      { Q931_IE_OPERATOR_SYSTEM_ACCESS,   "Operator system access" },
      { 0,                          NULL }
};
/* Codeset 6 */
static const value_string q931_info_element_vals6[] = {
      { Q931_IE_REDIRECTING_NUMBER,       "Redirecting number" },
      { Q931_IE_REDIRECTING_SUBADDR,            "Redirecting subaddress" },
      { Q931_IE_CALL_APPEARANCE,          "Call appearance" },
      { 0,                          NULL }
};
/* Codeset 7 */
static const value_string q931_info_element_vals7[] = {
      { 0,                          NULL }
};

/* Codeset array */
#define NUM_INFO_ELEMENT_VALS (Q931_IE_SHIFT_CODESET+1)
static const value_string *q931_info_element_vals[NUM_INFO_ELEMENT_VALS] = {
  q931_info_element_vals0,
  q931_info_element_vals1,
  q931_info_element_vals2,
  q931_info_element_vals3,
  q931_info_element_vals4,
  q931_info_element_vals5,
  q931_info_element_vals6,
  q931_info_element_vals7,
};

static const value_string q931_congestion_level_vals[] = {
      { 0x0, "Receiver ready" },
      { 0xF, "Receiver not ready" },
      { 0,   NULL }
};

static const value_string q931_repeat_indication_vals[] = {
      { 0x2, "Prioritized list" },
      { 0,   NULL }
};

/*
 * ITU-standardized coding.
 */
#define     Q931_ITU_STANDARDIZED_CODING  0x00

/*
 * Dissect a Segmented message information element.
 */
static void
dissect_q931_segmented_message_ie(tvbuff_t *tvb, int offset, int len,
    proto_tree *tree)
{
      if (len != 2) {
            proto_tree_add_text(tree, tvb, offset, len,
                "Segmented message: length is %d, should be 2", len);
            return;
      }
      if (tvb_get_guint8(tvb, offset) & 0x80) {
            proto_tree_add_text(tree, tvb, offset, 1,
                "First segment: %u segments remaining",
                tvb_get_guint8(tvb, offset) & 0x7F);
      } else {
            proto_tree_add_text(tree, tvb, offset, 1,
                "Not first segment: %u segments remaining",
                tvb_get_guint8(tvb, offset) & 0x7F);
      }
      proto_tree_add_item(tree, hf_q931_segment_type, tvb, offset + 1, 1, FALSE);
}

/*
 * Dissect a Bearer capability or Low-layer compatibility information element.
 */
static const value_string q931_coding_standard_vals[] = {
      { 0x0, "ITU-T standardized coding" },
      { 0x1, "ISO/IEC standard" },
      { 0x2, "National standard" },
      { 0x3, "Standard defined for this particular network" },
      { 0,    NULL }
};

static const value_string q931_information_transfer_capability_vals[] = {
      { 0x00, "Speech" },
      { 0x08, "Unrestricted digital information" },
      { 0x09, "Restricted digital information" },
      { 0x10, "3.1 kHz audio" },
      { 0x11, "Unrestricted digital information with tones/announcements" },
      { 0x18, "Video" },
      { 0,    NULL }
};

static const value_string q931_transfer_mode_vals[] = {
      { 0x00, "Circuit mode" },
      { 0x02, "Packet mode" },
      { 0,    NULL }
};

#define     Q931_IT_RATE_MULTIRATE  0x18

static const value_string q931_information_transfer_rate_vals[] = {
      { 0x00,                       "Packet mode" },
      { 0x10,                       "64 kbit/s" },
      { 0x11,                       "2 x 64 kbit/s" },
      { 0x13,                       "384 kbit/s" },
      { 0x15,                       "1536 kbit/s" },
      { 0x17,                       "1920 kbit/s" },
      { Q931_IT_RATE_MULTIRATE,     "Multirate (64 kbit/s base rate)" },
      { 0,                    NULL }
};

static const value_string q931_uil1_vals[] = {
      { 0x01, "V.110/I.460/X.30 rate adaption" },
      { 0x02, "Recommendation G.711 u-law" },
      { 0x03, "Recommendation G.711 A-law" },
      { 0x04, "Recommendation G.721 32 kbit/s ADPCM and Recommendation I.460" },
      { 0x05, "Recommendation H.221 and H.242" },
      { 0x06, "Recommendation H.223 and H.245" },
      { 0x07, "Non-ITU-T-standardized rate adaption" },
      { 0x08, "V.120 rate adaption" },
      { 0x09, "X.31 HDLC flag stuffing" },
      { 0,    NULL }
};

static const value_string q931_l1_user_rate_vals[] = {
      { 0x00, "Rate indicated by E-bits" },
      { 0x01, "0.6 kbit/s" },
      { 0x02, "1.2 kbit/s" },
      { 0x03, "2.4 kbit/s" },
      { 0x04, "3.6 kbit/s" },
      { 0x05, "4.8 kbit/s" },
      { 0x06, "7.2 kbit/s" },
      { 0x07, "8 kbit/s" },
      { 0x08, "9.6 kbit/s" },
      { 0x09, "14.4 kbit/s" },
      { 0x0A, "16 kbit/s" },
      { 0x0B, "19.2 kbit/s" },
      { 0x0C, "32 kbit/s" },
      { 0x0E, "48 kbit/s" },
      { 0x0F, "56 kbit/s" },
      { 0x10, "64 kbit/s "},
      { 0x15, "0.1345 kbit/s" },
      { 0x16, "0.100 kbit/s" },
      { 0x17, "0.075/1.2 kbit/s" },
      { 0x18, "1.2/0.075 kbit/s" },
      { 0x19, "0.050 kbit/s" },
      { 0x1A, "0.075 kbit/s" },
      { 0x1B, "0.110 kbit/s" },
      { 0x1C, "0.150 kbit/s" },
      { 0x1D, "0.200 kbit/s" },
      { 0x1E, "0.300 kbit/s" },
      { 0x1F, "12 kbit/s" },
      { 0,    NULL }
};

static const value_string q931_l1_intermediate_rate_vals[] = {
      { 0x20, "8 kbit/s" },
      { 0x40, "16 kbit/s" },
      { 0x60, "32 kbit/s" },
      { 0,    NULL }
};

static const value_string q931_l1_stop_bits_vals[] = {
      { 0x20, "1" },
      { 0x40, "1.5" },
      { 0x60, "2" },
      { 0,    NULL }
};

static const value_string q931_l1_data_bits_vals[] = {
      { 0x08, "5" },
      { 0x10, "7" },
      { 0x18, "8" },
      { 0,    NULL }
};

static const value_string q931_l1_parity_vals[] = {
      { 0x00, "Odd" },
      { 0x02, "Even" },
      { 0x03, "None" },
      { 0x04, "Forced to 0" },
      { 0x05, "Forced to 1" },
      { 0,    NULL }
};

static const value_string q931_l1_modem_type_vals[] = {
      { 0x11, "V.21" },
      { 0x12, "V.22" },
      { 0x13, "V.22 bis" },
      { 0x14, "V.23" },
      { 0x15, "V.26" },
      { 0x16, "V.26 bis" },
      { 0x17, "V.26 ter" },
      { 0x18, "V.27" },
      { 0x19, "V.27 bis" },
      { 0x1A, "V.27 ter" },
      { 0x1B, "V.29" },
      { 0x1C, "V.32" },
      { 0x1E, "V.34" },
      { 0,    NULL }
};

#define     Q931_UIL2_USER_SPEC     0x10

static const value_string q931_uil2_vals[] = {
      { 0x01,                 "Basic mode ISO 1745" },
      { 0x02,                 "Q.921/I.441" },  /* LAPD */
      { 0x06,                 "X.25, link layer" },   /* LAPB */
      { 0x07,                 "X.25 multilink" },     /* or 0x0F? */
      { 0x08,                 "T.71 Extended LAPB" },
      { 0x09,                 "HDLC ARM" },
      { 0x0A,                 "HDLC NRM" },
      { 0x0B,                 "HDLC ABM" },
      { 0x0C,                 "ISO 8802/2 LLC" },
      { 0x0D,                 "X.75 Single Link Procedure" },
      { 0x0E,                 "Q.922" },
      { 0x0F,                 "Core aspects of Q.922" },
      { Q931_UIL2_USER_SPEC,  "User-specified" },
      { 0x11,                 "ISO 7776 DTE-DTE operation" },
      { 0,              NULL }
};

static const value_string q931_mode_vals[] = {
      { 0x20, "Normal mode" },
      { 0x40, "Extended mode" },
      { 0,    NULL }
};

#define     Q931_UIL3_X25_PL  0x06
#define     Q931_UIL3_ISO_8208      0x07  /* X.25-based */
#define     Q931_UIL3_X223          0x08  /* X.25-based */
#define     Q931_UIL3_TR_9577 0x0B
#define     Q931_UIL3_USER_SPEC     0x10

static const value_string q931_uil3_vals[] = {
      { 0x02,                 "Q.931/I.451" },
      { Q931_UIL3_X25_PL,     "X.25, packet layer" },
      { Q931_UIL3_ISO_8208,   "ISO/IEC 8208" },
      { Q931_UIL3_X223, "X.223/ISO 8878" },
      { 0x09,                 "ISO/IEC 8473" },
      { 0x0A,                 "T.70" },
      { Q931_UIL3_TR_9577,    "ISO/IEC TR 9577" },
      { Q931_UIL3_USER_SPEC,  "User-specified" },
      { 0,              NULL }
};

static void
dissect_q931_protocol_discriminator(tvbuff_t *tvb, int offset, proto_tree *tree)
{
      unsigned int discriminator = tvb_get_guint8(tvb, offset);

      if (discriminator == NLPID_Q_931) {
            proto_tree_add_uint_format(tree, hf_q931_discriminator,
                   tvb, offset, 1, discriminator,
                   "Protocol discriminator: Q.931");
      } else if (discriminator == NLPID_Q_2931) {
            proto_tree_add_uint_format(tree, hf_q931_discriminator,
                   tvb, offset, 1, discriminator,
                   "Protocol discriminator: Q.2931");
      } else if ((discriminator >= 16 && discriminator < 63)
          || ((discriminator >= 80) && (discriminator < 254))) {
            proto_tree_add_uint_format(tree, hf_q931_discriminator,
                tvb, offset, 1, discriminator,
                "Protocol discriminator: Network layer or layer 3 protocol (0x%02X)",
                discriminator);
      } else if (discriminator >= 64 && discriminator <= 79) {
            proto_tree_add_uint_format(tree, hf_q931_discriminator,
                tvb, offset, 1, discriminator,
                "Protocol discriminator: National use (0x%02X)",
                discriminator);
      } else {
            proto_tree_add_uint_format(tree, hf_q931_discriminator,
                tvb, offset, 1, discriminator,
                "Protocol discriminator: Reserved (0x%02X)",
                discriminator);
      }
}

void
dissect_q931_bearer_capability_ie(tvbuff_t *tvb, int offset, int len,
    proto_tree *tree)
{
      guint8 octet;
      guint8 coding_standard;
      guint8 it_rate;
      guint8 modem_type;
      guint8 uil2_protocol;
      guint8 uil3_protocol;
      guint8 add_l3_info;

      if (len == 0)
            return;
      octet = tvb_get_guint8(tvb, offset);
      coding_standard = octet & 0x60;
      if (coding_standard != Q931_ITU_STANDARDIZED_CODING) {
            /*
             * We don't know how the bearer capability is encoded,
             * so just dump it as data and be done with it.
             */
            proto_tree_add_text(tree, tvb, offset,
                len, "Data: %s",
                tvb_bytes_to_str(tvb, offset, len));
            proto_tree_add_boolean(tree, hf_q931_extension_ind, tvb, offset, 1, octet);
            proto_tree_add_uint(tree, hf_q931_coding_standard, tvb, offset, 1, octet);
            return;
      }
      proto_tree_add_boolean(tree, hf_q931_extension_ind, tvb, offset, 1, octet);
      proto_tree_add_uint(tree, hf_q931_coding_standard, tvb, offset, 1, octet);
      proto_tree_add_uint(tree, hf_q931_information_transfer_capability, tvb, offset, 1, octet);
      offset += 1;
      len -= 1;

      /*
       * XXX - only in Low-layer compatibility information element.
       */
      if (!(octet & Q931_IE_VL_EXTENSION)) {
            if (len == 0)
                  return;
            octet = tvb_get_guint8(tvb, offset);
            proto_tree_add_text(tree, tvb, offset, 1,
                "Out-band negotiation %spossible",
                (octet & 0x40) ? "" : "not ");
            offset += 1;
            len -= 1;
      }

      if (len == 0)
            return;
      octet = tvb_get_guint8(tvb, offset);
      proto_tree_add_boolean(tree, hf_q931_extension_ind, tvb, offset, 1, octet);
      proto_tree_add_uint(tree, hf_q931_transfer_mode, tvb, offset, 1, octet);
      proto_tree_add_uint(tree, hf_q931_information_transfer_rate, tvb, offset, 1, octet);
      it_rate = octet & 0x1F;
      offset += 1;
      len -= 1;

      if (it_rate == Q931_IT_RATE_MULTIRATE) {
            if (len == 0)
                  return;
            proto_tree_add_text(tree, tvb, offset, 1, "Rate multiplier: %u", tvb_get_guint8(tvb, offset));
            offset += 1;
            len -= 1;
      }

      if (len == 0)
            return;
      octet = tvb_get_guint8(tvb, offset);
      if ((octet & 0x60) == 0x20) {
            /*
             * Layer 1 information.
             */
            proto_tree_add_boolean(tree, hf_q931_extension_ind, tvb, offset, 1, octet);
            proto_tree_add_uint(tree, hf_q931_uil1, tvb, offset, 1, octet);
            offset += 1;
            len -= 1;

            if (octet & Q931_IE_VL_EXTENSION)
                  goto l1_done;
            if (len == 0)
                  return;
            octet = tvb_get_guint8(tvb, offset);
            proto_tree_add_text(tree, tvb, offset, 1,
                "Layer 1 is %s",
                (octet & 0x40) ? "Asynchronous" : "Synchronous");
            proto_tree_add_text(tree, tvb, offset, 1,
                "Layer 1 in-band negotiation is %spossible",
                (octet & 0x20) ? "" : "not ");
            proto_tree_add_text(tree, tvb, offset, 1,
                "User rate: %s",
                val_to_str(octet & 0x1F, q931_l1_user_rate_vals,
                  "Unknown (0x%02X)"));
            offset += 1;
            len -= 1;

            if (octet & Q931_IE_VL_EXTENSION)
                  goto l1_done;
            if (len == 0)
                  return;
            octet = tvb_get_guint8(tvb, offset);
            proto_tree_add_text(tree, tvb, offset, 1,
                "Intermediate rate: %s",
                  val_to_str(octet & 0x60, q931_l1_intermediate_rate_vals,
                   "Unknown (0x%X)"));
            proto_tree_add_text(tree, tvb, offset, 1,
                "%s to send data with network independent clock",
                (octet & 0x10) ? "Required" : "Not required");
            proto_tree_add_text(tree, tvb, offset, 1,
                "%s accept data with network independent clock",
                (octet & 0x08) ? "Can" : "Cannot");
            proto_tree_add_text(tree, tvb, offset, 1,
                "%s to send data with flow control mechanism",
                (octet & 0x04) ? "Required" : "Not required");
            proto_tree_add_text(tree, tvb, offset, 1,
                "%s accept data with flow control mechanism",
                (octet & 0x02) ? "Can" : "Cannot");
            offset += 1;
            len -= 1;

            if (octet & Q931_IE_VL_EXTENSION)
                  goto l1_done;
            if (len == 0)
                  return;
            octet = tvb_get_guint8(tvb, offset);
            proto_tree_add_text(tree, tvb, offset, 1,
                "Rate adaption header %sincluded",
                (octet & 0x40) ? "" : "not ");
            proto_tree_add_text(tree, tvb, offset, 1,
                "Multiple frame establishment %ssupported",
                (octet & 0x20) ? "" : "not ");
            proto_tree_add_text(tree, tvb, offset, 1,
                "%s mode of operation",
                (octet & 0x10) ? "Protocol sensitive" : "Bit transparent");
            proto_tree_add_text(tree, tvb, offset, 1,
                (octet & 0x08) ?
                  "Full protocol negotiation" : "LLI = 256 only");
            proto_tree_add_text(tree, tvb, offset, 1,
                "Message originator is %s",
                (octet & 0x04) ? "Assignor only" : "Default assignee");
            proto_tree_add_text(tree, tvb, offset, 1,
                "Negotiation is done %s",
                (octet & 0x02) ? "in-band" : "out-of-band");
            offset += 1;
            len -= 1;

            if (octet & Q931_IE_VL_EXTENSION)
                  goto l1_done;
            if (len == 0)
                  return;
            octet = tvb_get_guint8(tvb, offset);
            proto_tree_add_text(tree, tvb, offset, 1,
                "Stop bits: %s",
                  val_to_str(octet & 0x60, q931_l1_stop_bits_vals,
                   "Unknown (0x%X)"));
            proto_tree_add_text(tree, tvb, offset, 1,
                "Data bits: %s",
                  val_to_str(octet & 0x18, q931_l1_data_bits_vals,
                   "Unknown (0x%X)"));
            proto_tree_add_text(tree, tvb, offset, 1,
                "Parity: %s",
                  val_to_str(octet & 0x07, q931_l1_parity_vals,
                   "Unknown (0x%X)"));

            if (octet & Q931_IE_VL_EXTENSION)
                  goto l1_done;
            if (len == 0)
                  return;
            octet = tvb_get_guint8(tvb, offset);
            proto_tree_add_text(tree, tvb, offset, 1,
                "%s duplex",
                (octet & 0x40) ? "Full" : "Half");
            modem_type = octet & 0x3F;
            if (modem_type <= 0x5 ||
                (modem_type >= 0x20 && modem_type <= 0x2F)) {
                  proto_tree_add_text(tree, tvb, offset, 1,
                      "Modem type: National use 0x%02X", modem_type);
            } else if (modem_type >= 0x30) {
                  proto_tree_add_text(tree, tvb, offset, 1,
                      "Modem type: User specified 0x%02X", modem_type);
            } else {
                  proto_tree_add_text(tree, tvb, offset, 1,
                      "Modem type: %s",
                        val_to_str(modem_type, q931_l1_modem_type_vals,
                        "Unknown (0x%02X)"));
            }
            offset += 1;
            len -= 1;
      }
l1_done:
      ;

      if (len == 0)
            return;
      octet = tvb_get_guint8(tvb, offset);
      if ((octet & 0x60) == 0x40) {
            /*
             * Layer 2 information.
             */
            uil2_protocol = octet & 0x1F;
            proto_tree_add_text(tree, tvb, offset, 1,
                "User information layer 2 protocol: %s",
                val_to_str(uil2_protocol, q931_uil2_vals,
                  "Unknown (0x%02X)"));
            offset += 1;
            len -= 1;

            /*
             * XXX - only in Low-layer compatibility information element.
             */
            if (octet & Q931_IE_VL_EXTENSION)
                  goto l2_done;
            if (len == 0)
                  return;
            octet = tvb_get_guint8(tvb, offset);
            if (uil2_protocol == Q931_UIL2_USER_SPEC) {
                  proto_tree_add_text(tree, tvb, offset, 1,
                      "User-specified layer 2 protocol information: 0x%02X",
                      octet & 0x7F);
            } else {
                  proto_tree_add_text(tree, tvb, offset, 1,
                      "Mode: %s",
                      val_to_str(octet & 0x60, q931_mode_vals,
                        "Unknown (0x%02X)"));
            }
            offset += 1;
            len -= 1;

            if (octet & Q931_IE_VL_EXTENSION)
                  goto l2_done;
            if (len == 0)
                  return;
            octet = tvb_get_guint8(tvb, offset);
            proto_tree_add_text(tree, tvb, offset, 1,
                "Window size: %u k", octet & 0x7F);
            offset += 1;
            len -= 1;
      }
l2_done:
      ;

      if (len == 0)
            return;
      octet = tvb_get_guint8(tvb, offset);
      if ((octet & 0x60) == 0x60) {
            /*
             * Layer 3 information.
             */
            uil3_protocol = octet & 0x1F;
            proto_tree_add_text(tree, tvb, offset, 1,
                "User information layer 3 protocol: %s",
                val_to_str(uil3_protocol, q931_uil3_vals,
                  "Unknown (0x%02X)"));
            offset += 1;
            len -= 1;


            /*
             * XXX - only in Low-layer compatibility information element.
             */
            if (octet & Q931_IE_VL_EXTENSION)
                  goto l3_done;
            if (len == 0)
                  return;
            octet = tvb_get_guint8(tvb, offset);
            switch (uil3_protocol) {

            case Q931_UIL3_X25_PL:
            case Q931_UIL3_ISO_8208:
            case Q931_UIL3_X223:
                  proto_tree_add_text(tree, tvb, offset, 1,
                      "Mode: %s",
                      val_to_str(octet & 0x60, q931_mode_vals,
                        "Unknown (0x%02X)"));
                  offset += 1;
                  len -= 1;

                  if (octet & Q931_IE_VL_EXTENSION)
                        goto l3_done;
                  if (len == 0)
                        return;
                  octet = tvb_get_guint8(tvb, offset);
                  proto_tree_add_text(tree, tvb, offset, 1,
                      "Default packet size: %u", octet & 0x0F);
                  offset += 1;
                  len -= 1;

                  if (octet & Q931_IE_VL_EXTENSION)
                        goto l3_done;
                  if (len == 0)
                        return;
                  octet = tvb_get_guint8(tvb, offset);
                  proto_tree_add_text(tree, tvb, offset, 1,
                      "Packet window size: %u", octet & 0x7F);
                  offset += 1;
                  len -= 1;
                  break;

            case Q931_UIL3_USER_SPEC:
                  proto_tree_add_text(tree, tvb, offset, 1,
                      "Default packet size: %u octets",
                      1 << (octet & 0x0F));
                  offset += 1;
                  len -= 1;
                  break;

            case Q931_UIL3_TR_9577:
                  add_l3_info = (octet & 0x0F) << 4;
                  if (octet & Q931_IE_VL_EXTENSION)
                        goto l3_done;
                  if (len == 0)
                        return;
                  octet = tvb_get_guint8(tvb, offset + 1);
                  add_l3_info |= (octet & 0x0F);
                  proto_tree_add_text(tree, tvb, offset, 2,
                      "Additional layer 3 protocol information: %s",
                      val_to_str(add_l3_info, nlpid_vals,
                        "Unknown (0x%02X)"));
                  offset += 2;
                  len -= 2;
                  break;
            }
      }
l3_done:
      ;
}

/*
 * Dissect a Cause information element.
 */


const value_string q931_cause_location_vals[] = {
      { 0x00, "User (U)" },
      { 0x01, "Private network serving the local user (LPN)" },
      { 0x02, "Public network serving the local user (LN)" },
      { 0x03, "Transit network (TN)" },
      { 0x04, "Public network serving the remote user (RLN)" },
      { 0x05, "Private network serving the remote user (RPN)" },
      { 0x07, "International network (INTL)" },
      { 0x0A, "Network beyond interworking point (BI)" },
      { 0,    NULL }
};

static const value_string q931_cause_recommendation_vals[] = {
      { 0x00, "Q.931" },
      { 0x03, "X.21" },
      { 0x04, "X.25" },
      { 0x05, "Q.1031/Q.1051" },
      { 0,    NULL }
};

/*
 * Cause codes for Cause.
 */
#define     Q931_CAUSE_UNALLOC_NUMBER     0x01
#define     Q931_CAUSE_NO_ROUTE_TO_DEST   0x03
#define     Q931_CAUSE_CALL_REJECTED      0x15
#define     Q931_CAUSE_NUMBER_CHANGED     0x16
#define     Q931_CAUSE_ACCESS_INFO_DISC   0x2B
#define     Q931_CAUSE_QOS_UNAVAILABLE    0x31
#define     Q931_CAUSE_CHAN_NONEXISTENT   0x52
#define     Q931_CAUSE_INCOMPATIBLE_DEST  0x58
#define     Q931_CAUSE_MAND_IE_MISSING    0x60
#define     Q931_CAUSE_MT_NONEX_OR_UNIMPL 0x61
#define     Q931_CAUSE_IE_NONEX_OR_UNIMPL 0x63
#define     Q931_CAUSE_INVALID_IE_CONTENTS      0x64
#define     Q931_CAUSE_MSG_INCOMPAT_W_CS  0x65
#define     Q931_CAUSE_REC_TIMER_EXP      0x66

const value_string q931_cause_code_vals[] = {
      { 0x00,                       "Valid cause code not yet received" },
      { Q931_CAUSE_UNALLOC_NUMBER,  "Unallocated (unassigned) number" },
      { 0x02,                       "No route to specified transit network" },
      { Q931_CAUSE_NO_ROUTE_TO_DEST,      "No route to destination" },
      { 0x04,                       "Send special information tone" },
      { 0x05,                       "Misdialled trunk prefix" },
      { 0x06,                       "Channel unacceptable" },
      { 0x07,                       "Call awarded and being delivered in an established channel" },
      { 0x08,                       "Prefix 0 dialed but not allowed" },
                              /* Q.850 - "Preemption" */
      { 0x09,                       "Prefix 1 dialed but not allowed" },
                              /* Q.850 - "Preemption - circuit reserved for reuse" */
      { 0x0A,                       "Prefix 1 dialed but not required" },
      { 0x0B,                       "More digits received than allowed, call is proceeding" },
      { 0x0E,                       "QoR: ported number" },
      { 0x10,                       "Normal call clearing" },
      { 0x11,                       "User busy" },
      { 0x12,                       "No user responding" },
      { 0x13,                       "No answer from user (user alerted)" },
      { 0x14,                       "Subscriber absent" },
      { Q931_CAUSE_CALL_REJECTED,   "Call rejected" },
      { Q931_CAUSE_NUMBER_CHANGED,  "Number changed" },
      { 0x17,                       "Reverse charging rejected" },
                              /* Q.850 - "Redirection to new destination" */
      { 0x18,                       "Call suspended" },
                              /* Q.850 Amendment 1 - "Call rejected due to feature at the destination" */
      { 0x19,                       "Call resumed" },
                              /* Q.850 - "Exchange routing error */
      { 0x1A,                       "Non-selected user clearing" },
      { 0x1B,                       "Destination out of order" },
      { 0x1C,                       "Invalid number format (incomplete number)" },
      { 0x1D,                       "Facility rejected" },
      { 0x1E,                       "Response to STATUS ENQUIRY" },
      { 0x1F,                       "Normal unspecified" },
      { 0x21,                       "Circuit out of order" },
      { 0x22,                       "No circuit/channel available" },
      { 0x23,                       "Destination unattainable" },
      { 0x25,                       "Degraded service" },
      { 0x26,                       "Network out of order" },
      { 0x27,                       "Transit delay range cannot be achieved" },
                              /* Q.850 - "Permanent frame mode connection out of service" */
      { 0x28,                       "Throughput range cannot be achieved" },
                              /* Q.850 - "Permanent frame mode connection operational" */
      { 0x29,                       "Temporary failure" },
      { 0x2A,                       "Switching equipment congestion" },
      { Q931_CAUSE_ACCESS_INFO_DISC,      "Access information discarded" },
      { 0x2C,                       "Requested circuit/channel not available" },
      { 0x2D,                       "Pre-empted" },
      { 0x2E,                       "Precedence call blocked" },
      { 0x2F,                       "Resources unavailable, unspecified" },
      { Q931_CAUSE_QOS_UNAVAILABLE, "Quality of service unavailable" },
      { 0x32,                       "Requested facility not subscribed" },
      { 0x33,                       "Reverse charging not allowed" },
      { 0x34,                       "Outgoing calls barred" },
      { 0x35,                       "Outgoing calls barred within CUG" },
      { 0x36,                       "Incoming calls barred" },
      { 0x37,                       "Incoming calls barred within CUG" },
      { 0x38,                       "Call waiting not subscribed" },
      { 0x39,                       "Bearer capability not authorized" },
      { 0x3A,                       "Bearer capability not presently available" },
      { 0x3E,                       "Inconsistency in designated outgoing access information and subscriber class" },
      { 0x3F,                       "Service or option not available, unspecified" },
      { 0x41,                       "Bearer capability not implemented" },
      { 0x42,                       "Channel type not implemented" },
      { 0x43,                       "Transit network selection not implemented" },
      { 0x44,                       "Message not implemented" },
      { 0x45,                       "Requested facility not implemented" },
      { 0x46,                       "Only restricted digital information bearer capability is available" },
      { 0x4F,                       "Service or option not implemented, unspecified" },
      { 0x51,                       "Invalid call reference value" },
      { Q931_CAUSE_CHAN_NONEXISTENT,      "Identified channel does not exist" },
      { 0x53,                       "Call identity does not exist for suspended call" },
      { 0x54,                       "Call identity in use" },
      { 0x55,                       "No call suspended" },
      { 0x56,                       "Call having the requested call identity has been cleared" },
      { 0x57,                       "Called user not member of CUG" },
      { Q931_CAUSE_INCOMPATIBLE_DEST,     "Incompatible destination" },
      { 0x59,                       "Non-existent abbreviated address entry" },
      { 0x5A,                       "Destination address missing, and direct call not subscribed" },
                              /* Q.850 - "Non-existent CUG" */
      { 0x5B,                       "Invalid transit network selection (national use)" },
      { 0x5C,                       "Invalid facility parameter" },
      { 0x5D,                       "Mandatory information element is missing" },
      { 0x5F,                       "Invalid message, unspecified" },
      { Q931_CAUSE_MAND_IE_MISSING, "Mandatory information element is missing" },
      { Q931_CAUSE_MT_NONEX_OR_UNIMPL,"Message type non-existent or not implemented" },
      { 0x62,                       "Message not compatible with call state or message type non-existent or not implemented" },
      { Q931_CAUSE_IE_NONEX_OR_UNIMPL,"Information element nonexistant or not implemented" },
      { Q931_CAUSE_INVALID_IE_CONTENTS,"Invalid information element contents" },
      { Q931_CAUSE_MSG_INCOMPAT_W_CS,     "Message not compatible with call state" },
      { Q931_CAUSE_REC_TIMER_EXP,   "Recovery on timer expiry" },
      { 0x67,                       "Parameter non-existent or not implemented - passed on" },
      { 0x6E,                       "Message with unrecognized parameter discarded" },
      { 0x6F,                       "Protocol error, unspecified" },
      { 0x7F,                       "Internetworking, unspecified" },
      { 0,                    NULL }
};

static const value_string q931_cause_condition_vals[] = {
      { 0x00, "Unknown" },
      { 0x01, "Permanent" },
      { 0x02, "Transient" },
      { 0x00, NULL }
};

#define     Q931_REJ_USER_SPECIFIC        0x00
#define     Q931_REJ_IE_MISSING           0x04
#define     Q931_REJ_IE_INSUFFICIENT      0x08

static const value_string q931_rejection_reason_vals[] = {
      { 0x00, "User specific" },
      { 0x04, "Information element missing" },
      { 0x08, "Information element contents are not sufficient" },
      { 0x00, NULL }
};

void
dissect_q931_cause_ie(tvbuff_t *tvb, int offset, int len,
    proto_tree *tree, int hf_cause_value, guint8 *cause_value)
{
      guint8 octet;
      guint8 coding_standard;
      guint8 rejection_reason;

      if (len == 0)
            return;
      octet = tvb_get_guint8(tvb, offset);
      coding_standard = octet & 0x60;
      if (coding_standard != Q931_ITU_STANDARDIZED_CODING) {
            /*
             * We don't know how the cause is encoded,
             * so just dump it as data and be done with it.
             */
            proto_tree_add_uint(tree, hf_q931_coding_standard, tvb, offset, 1, octet);
            proto_tree_add_text(tree, tvb, offset,
                len, "Data: %s",
                tvb_bytes_to_str(tvb, offset, len));
            return;
      }
      proto_tree_add_uint(tree, hf_q931_cause_location, tvb, offset, 1, octet);
      proto_tree_add_uint(tree, hf_q931_coding_standard, tvb, offset, 1, octet);
      proto_tree_add_boolean(tree, hf_q931_extension_ind, tvb, offset, 1, octet);
      offset += 1;
      len -= 1;

      if (!(octet & Q931_IE_VL_EXTENSION)) {
            if (len == 0)
                  return;
            octet = tvb_get_guint8(tvb, offset);
            proto_tree_add_text(tree, tvb, offset, 1,
                "Recommendation: %s",
                val_to_str(octet & 0x7F, q931_cause_recommendation_vals,
                  "Unknown (0x%02X)"));
            proto_tree_add_boolean(tree, hf_q931_extension_ind, tvb, offset, 1, octet);
            offset += 1;
            len -= 1;
      }

      if (len == 0)
            return;
      octet = tvb_get_guint8(tvb, offset);
      *cause_value = octet & 0x7F;

      /* add cause value to packet info for use in tap */
      if(have_valid_q931_pi) {
            q931_pi->cause_value = *cause_value;
      }

      proto_tree_add_uint(tree, hf_cause_value, tvb, offset, 1, *cause_value);
      proto_tree_add_boolean(tree, hf_q931_extension_ind, tvb, offset, 1, octet);
      offset += 1;
      len -= 1;

      if (len == 0)
            return;
      switch (*cause_value) {

      case Q931_CAUSE_UNALLOC_NUMBER:
      case Q931_CAUSE_NO_ROUTE_TO_DEST:
      case Q931_CAUSE_QOS_UNAVAILABLE:
            octet = tvb_get_guint8(tvb, offset);
            proto_tree_add_text(tree, tvb, offset, 1,
                "Network service: %s",
                (octet & 0x80) ? "User" : "Provider");
            proto_tree_add_text(tree, tvb, offset, 1,
                "%s",
                (octet & 0x40) ? "Abnormal" : "Normal");
            proto_tree_add_text(tree, tvb, offset, 1,
                "Condition: %s",
                val_to_str(octet & 0x03, q931_cause_condition_vals,
                  "Unknown (0x%X)"));
            break;

      case Q931_CAUSE_CALL_REJECTED:
            rejection_reason = octet & 0x7C;
            proto_tree_add_text(tree, tvb, offset, 1,
                "Rejection reason: %s",
                val_to_str(octet & 0x7C, q931_rejection_reason_vals,
                  "Unknown (0x%X)"));
            proto_tree_add_text(tree, tvb, offset, 1,
                "Condition: %s",
                val_to_str(octet & 0x03, q931_cause_condition_vals,
                  "Unknown (0x%X)"));
            offset += 1;
            len -= 1;

            if (len == 0)
                  return;
            switch (rejection_reason) {

            case Q931_REJ_USER_SPECIFIC:
                  proto_tree_add_text(tree, tvb, offset, len,
                      "User specific diagnostic: %s",
                      tvb_bytes_to_str(tvb, offset, len));
                  break;

            case Q931_REJ_IE_MISSING:
                  proto_tree_add_text(tree, tvb, offset, 1,
                      "Missing information element: %s",
                      val_to_str(tvb_get_guint8(tvb, offset), q931_info_element_vals0,
                        "Unknown (0x%02X)"));
                  break;

            case Q931_REJ_IE_INSUFFICIENT:
                  proto_tree_add_text(tree, tvb, offset, 1,
                      "Insufficient information element: %s",
                      val_to_str(tvb_get_guint8(tvb, offset), q931_info_element_vals0,
                        "Unknown (0x%02X)"));
                  break;

            default:
                  proto_tree_add_text(tree, tvb, offset, len,
                      "Diagnostic: %s",
                      tvb_bytes_to_str(tvb, offset, len));
                  break;
            }
            break;

      case Q931_CAUSE_ACCESS_INFO_DISC:
      case Q931_CAUSE_INCOMPATIBLE_DEST:
      case Q931_CAUSE_MAND_IE_MISSING:
      case Q931_CAUSE_IE_NONEX_OR_UNIMPL:
      case Q931_CAUSE_INVALID_IE_CONTENTS:
            do {
                  proto_tree_add_text(tree, tvb, offset, 1,
                      "Information element: %s",
                      val_to_str(tvb_get_guint8(tvb, offset), q931_info_element_vals0,
                        "Unknown (0x%02X)"));
                  offset += 1;
                  len -= 1;
            } while (len != 0);
            break;

      case Q931_CAUSE_MT_NONEX_OR_UNIMPL:
      case Q931_CAUSE_MSG_INCOMPAT_W_CS:
            proto_tree_add_text(tree, tvb, offset, 1,
                "Message type: %s",
                val_to_str(tvb_get_guint8(tvb, offset), q931_message_type_vals,
                  "Unknown (0x%02X)"));
            break;

      case Q931_CAUSE_REC_TIMER_EXP:
            if (len < 3)
                  return;
            proto_tree_add_text(tree, tvb, offset, 3,
                "Timer: %.3s", tvb_get_ptr(tvb, offset, 3));
            break;

      default:
            proto_tree_add_text(tree, tvb, offset, len,
                "Diagnostics: %s",
                tvb_bytes_to_str(tvb, offset, len));
      }
}

/*
 * Dissect a Call state information element.
 */
static const value_string q931_call_state_vals[] = {
      { 0x00, "Null" },
      { 0x01, "Call initiated" },
      { 0x02, "Overlap sending" },
      { 0x03, "Outgoing call proceeding" },
      { 0x04, "Call delivered" },
      { 0x06, "Call present" },
      { 0x07, "Call received" },
      { 0x08, "Connect request" },
      { 0x09, "Incoming call proceeding" },
      { 0x0A, "Active" },
      { 0x0B, "Disconnect request" },
      { 0x0C, "Disconnect indication" },
      { 0x0F, "Suspend request" },
      { 0x12, "Resume request" },
      { 0x13, "Release request" },
      { 0x16, "Call abort"},
      { 0x19, "Overlap receiving" },
      { 0x3D, "Restart request" },
      { 0x3E, "Restart" },
      { 0,    NULL }
};

static void
dissect_q931_call_state_ie(tvbuff_t *tvb, int offset, int len,
    proto_tree *tree)
{
      guint8 octet;
      guint8 coding_standard;

      if (len == 0)
            return;
      octet = tvb_get_guint8(tvb, offset);
      coding_standard = octet & 0x60;
      proto_tree_add_uint(tree, hf_q931_coding_standard, tvb, offset, 1, octet);
      if (coding_standard != Q931_ITU_STANDARDIZED_CODING) {
            /*
             * We don't know how the call state is encoded,
             * so just dump it as data and be done with it.
             */
            proto_tree_add_text(tree, tvb, offset,
                len, "Data: %s",
                tvb_bytes_to_str(tvb, offset, len));
            return;
      }
      proto_tree_add_text(tree, tvb, offset, 1,
          "Call state: %s",
          val_to_str(octet & 0x3F, q931_call_state_vals,
            "Unknown (0x%02X)"));
}

/*
 * Dissect a Channel identification information element.
 */
#define     Q931_INTERFACE_IDENTIFIED     0x40
#define     Q931_NOT_BASIC_CHANNEL        0x20

static const value_string q931_basic_channel_selection_vals[] = {
      { 0x00, "No channel" },
      { 0x01, "B1 channel" },
      { 0x02, "B2 channel" },
      { 0x03, "Any channel" },
      { 0,    NULL }
};

static const value_string q931_not_basic_channel_selection_vals[] = {
      { 0x00, "No channel" },
      { 0x01, "Channel indicated in following octets" },
      { 0x03, "Any channel" },
      { 0,    NULL }
};

#define     Q931_IS_SLOT_MAP        0x10

static const value_string q931_element_type_vals[] = {
      { 0x03, "B-channel units" },
      { 0x06, "H0-channel units" },
      { 0x08, "H11-channel units" },
      { 0x09, "H12-channel units" },
      { 0,    NULL }
};

static void
dissect_q931_channel_identification_ie(tvbuff_t *tvb, int offset, int len,
    proto_tree *tree)
{
      guint8 octet;
      guint8 coding_standard;

      if (len == 0)
            return;
      octet = tvb_get_guint8(tvb, offset);

      proto_tree_add_item(tree, hf_q931_extension_ind, tvb, offset, 1, FALSE);
      proto_tree_add_item(tree, hf_q931_channel_interface_explicit, tvb, offset, 1, FALSE);
      proto_tree_add_item(tree, hf_q931_channel_interface_type, tvb, offset, 1, FALSE);
      proto_tree_add_item(tree, hf_q931_channel_exclusive, tvb, offset, 1, FALSE);
      proto_tree_add_item(tree, hf_q931_channel_dchan, tvb, offset, 1, FALSE);
      
      if (octet & Q931_NOT_BASIC_CHANNEL) {
            proto_tree_add_item(tree, hf_q931_channel_selection_pri, tvb, offset, 1, FALSE);
      } else {
            proto_tree_add_item(tree, hf_q931_channel_selection_bri, tvb, offset, 1, FALSE);
      }
      offset += 1;
      len -= 1;

      if (octet & Q931_INTERFACE_IDENTIFIED) {
            guint8 octet;
            int identifier_offset = offset;
            int identifier_len = 0;
            do {
                  if (len == 0)
                        break;
                  octet = tvb_get_guint8(tvb, offset);
                  offset += 1;
                  len -= 1;
                  identifier_len++;
            } while (!(octet & Q931_IE_VL_EXTENSION));

            /*
             * XXX - do we want to strip off the 8th bit on the
             * last octet of the interface identifier?
             */
            if (identifier_len != 0) {
                  proto_tree_add_text(tree, tvb, identifier_offset,
                      identifier_len, "Interface identifier: %s",
                      bytes_to_str(
                        tvb_get_ptr(tvb, identifier_offset, identifier_len),
                        identifier_len));
            }
      }

      if (octet & Q931_NOT_BASIC_CHANNEL) {
            if (len == 0)
                  return;
            octet = tvb_get_guint8(tvb, offset);
            coding_standard = octet & 0x60;
            proto_tree_add_item(tree, hf_q931_extension_ind, tvb, offset, 1, FALSE);
            proto_tree_add_uint(tree, hf_q931_coding_standard, tvb, offset, 1, octet);
            if (coding_standard != Q931_ITU_STANDARDIZED_CODING) {
                  /*
                   * We don't know how the channel identifier is
                   * encoded, so just dump it as data and be done
                   * with it.
                   */
                  proto_tree_add_text(tree, tvb, offset,
                      len, "Data: %s",
                      tvb_bytes_to_str(tvb, offset, len));
                  return;
            }
            proto_tree_add_item(tree, hf_q931_channel_map, tvb, offset, 1, FALSE);
            proto_tree_add_item(tree, hf_q931_channel_element_type, tvb, offset, 1, FALSE);
            
            offset += 1;
            len -= 1;

            if (octet & Q931_IS_SLOT_MAP) {
                  guint8 octet;
                  while (len) {
                        octet = tvb_get_guint8(tvb, offset);
                        proto_tree_add_text(tree, tvb, offset, 1,
                              "Slot map: 0x%02x", octet);
                        offset += 1;
                        len -= 1;
                  } 
            } else {
                  guint8 octet;
                  do {
                        if (len == 0)
                              break;
                        octet = tvb_get_guint8(tvb, offset);

                        proto_tree_add_item(tree, hf_q931_extension_ind, tvb, offset, 1, FALSE);
                        proto_tree_add_item(tree,hf_q931_channel_number,tvb,offset,1,FALSE);

                        offset += 1;
                        len -= 1;
                  } while (!(octet & Q931_IE_VL_EXTENSION));
            }
      }
}

/*
 * Dissect a Progress indicator information element.
 */
static const value_string q931_progress_description_vals[] = {
      { 0x01, "Call is not end-to-end ISDN - progress information available in-band" },
      { 0x02, "Destination address is non-ISDN" },
      { 0x03, "Origination address is non-ISDN" },
      { 0x04, "Call has returned to the ISDN" },
      { 0x05, "Interworking has occurred and has resulted in a telecommunications service change" },
      { 0x08, "In-band information or an appropriate pattern is now available" },
      { 0,    NULL }
};

void
dissect_q931_progress_indicator_ie(tvbuff_t *tvb, int offset, int len,
    proto_tree *tree)
{
      guint8 octet;
      guint8 coding_standard;

      if (len == 0)
            return;
      octet = tvb_get_guint8(tvb, offset);
      coding_standard = octet & 0x60;
      proto_tree_add_uint(tree, hf_q931_coding_standard, tvb, offset, 1, octet);
      if (coding_standard != Q931_ITU_STANDARDIZED_CODING) {
            /*
             * We don't know how the progress indicator is encoded,
             * so just dump it as data and be done with it.
             */
            proto_tree_add_text(tree, tvb, offset,
                len, "Data: %s",
                tvb_bytes_to_str(tvb, offset, len));
            return;
      }
      proto_tree_add_text(tree, tvb, offset, 1,
          "Location: %s",
          val_to_str(octet & 0x0F, q931_cause_location_vals,
            "Unknown (0x%X)"));
      offset += 1;
      len -= 1;

      if (len == 0)
            return;
      octet = tvb_get_guint8(tvb, offset);
      proto_tree_add_text(tree, tvb, offset, 1,
          "Progress description: %s",
          val_to_str(octet & 0x7F, q931_progress_description_vals,
            "Unknown (0x%02X)"));
}

/*
 * Dissect a Network-specific facilities or Transit network selection
 * information element.
 */
static const value_string q931_netid_type_vals[] = {
      { 0x00, "User specified" },
      { 0x20, "National network identification" },
      { 0x30, "International network identification" },
      { 0,    NULL }
};

static const value_string q931_netid_plan_vals[] = {
      { 0x00, "Unknown" },
      { 0x01, "Carrier Identification Code" },
      { 0x03, "X.121 data network identification code" },
      { 0,    NULL }
};

static void
dissect_q931_ns_facilities_ie(tvbuff_t *tvb, int offset, int len,
    proto_tree *tree)
{
      guint8 octet;
      int netid_len;

      if (len == 0)
            return;
      octet = tvb_get_guint8(tvb, offset);
      netid_len = octet & 0x7F;
      proto_tree_add_text(tree, tvb, offset, 1,
          "Network identification length: %u",
          netid_len);
      offset += 1;
      len -= 1;
      if (netid_len != 0) {
            if (len == 0)
                  return;
            octet = tvb_get_guint8(tvb, offset);
            proto_tree_add_text(tree, tvb, offset, 1,
                "Type of network identification: %s",
                val_to_str(octet & 0x70, q931_netid_type_vals,
                  "Unknown (0x%02X)"));
            proto_tree_add_text(tree, tvb, offset, 1,
                "Network identification plan: %s",
                val_to_str(octet & 0x0F, q931_netid_plan_vals,
                  "Unknown (0x%02X)"));
            offset += 1;
            len -= 1;
            netid_len--;

            if (len == 0)
                  return;
            if (netid_len > len)
                  netid_len = len;
            if (netid_len != 0) {
                  proto_tree_add_text(tree, tvb, offset, netid_len,
                      "Network identification: %s",
                      tvb_format_text(tvb, offset, netid_len));
                  offset += netid_len;
                  len -= netid_len;
            }
      }

      /*
       * Whatever is left is the network-specific facility
       * specification.
       */
       if (len == 0)
            return;
      proto_tree_add_text(tree, tvb, offset,
          len, "Network-specific facility specification: %s",
          tvb_bytes_to_str(tvb, offset, len));
}

/*
 * Dissect a Notification indicator information element.
 */
static const value_string q931_notification_description_vals[] = {
      { 0x00, "User suspended" },
      { 0x01, "User resumed" },
      { 0x02, "Bearer service change" },
      { 0,    NULL }
};

static void
dissect_q931_notification_indicator_ie(tvbuff_t *tvb, int offset, int len,
    proto_tree *tree)
{
      guint8 octet;

      if (len == 0)
            return;
      octet = tvb_get_guint8(tvb, offset);
      proto_tree_add_text(tree, tvb, offset, 1,
          "Notification description: %s",
          val_to_str(octet & 0x7F, q931_notification_description_vals,
            "Unknown (0x%02X)"));
}

/*
 * Dissect a Date/time information element.
 */
static void
dissect_q931_date_time_ie(tvbuff_t *tvb, int offset, int len,
    proto_tree *tree)
{
      if (len == 6) {
            /*
             * XXX - what is "year" relative to?  Is "month" 0-origin or
             * 1-origin?  Q.931 doesn't say....
             */
            proto_tree_add_text(tree, tvb, offset, 6,
                "Date/time: %02u-%02u-%02u %02u:%02u:%02u",
                tvb_get_guint8(tvb, offset + 0), tvb_get_guint8(tvb, offset + 1), tvb_get_guint8(tvb, offset + 2),
                tvb_get_guint8(tvb, offset + 3), tvb_get_guint8(tvb, offset + 4), tvb_get_guint8(tvb, offset + 5));
      } else if (len == 5) {
            proto_tree_add_text(tree, tvb, offset, 5,
                "Date/time: %02u-%02u-%02u %02u:%02u:00",
                tvb_get_guint8(tvb, offset + 0), tvb_get_guint8(tvb, offset + 1), tvb_get_guint8(tvb, offset + 2),
                tvb_get_guint8(tvb, offset + 3), tvb_get_guint8(tvb, offset + 4));
      } else {
            proto_tree_add_text(tree, tvb, offset, len,
                "Date/time: length is %d, should be 5 or 6", len);
      }
}

/*
 * Dissect a Signal information element.
 */
static const value_string q931_signal_vals[] = {
      { 0x00, "Dial tone on" },
      { 0x01, "Ring tone on" },
      { 0x02, "Intercept tone on" },
      { 0x03, "Network congestion tone on" },   /* "fast busy" */
      { 0x04, "Busy tone on" },
      { 0x05, "Confirm tone on" },
      { 0x06, "Answer tone on" },
      { 0x07, "Call waiting tone on" },
      { 0x08, "Off-hook warning tone on" },
      { 0x09, "Preemption tone on" },
      { 0x3F, "Tones off" },
      { 0x40, "Alerting on - pattern 0" },
      { 0x41, "Alerting on - pattern 1" },
      { 0x42, "Alerting on - pattern 2" },
      { 0x43, "Alerting on - pattern 3" },
      { 0x44, "Alerting on - pattern 4" },
      { 0x45, "Alerting on - pattern 5" },
      { 0x46, "Alerting on - pattern 6" },
      { 0x47, "Alerting on - pattern 7" },
      { 0x4F, "Alerting off" },
      { 0,    NULL }
};

static void
dissect_q931_signal_ie(tvbuff_t *tvb, int offset, int len,
    proto_tree *tree)
{
      if (len != 1) {
            proto_tree_add_text(tree, tvb, offset, len,
                "Signal: length is %d, should be 1", len);
            return;
      }
      proto_tree_add_text(tree, tvb, offset, 1,
          "Signal: %s",
          val_to_str(tvb_get_guint8(tvb, offset), q931_signal_vals,
              "Unknown (0x%02X)"));
}

/*
 * Dissect an Information rate information element.
 */
static const value_string q931_throughput_class_vals[] = {
      { 0x03, "75 bit/s" },
      { 0x04, "150 bit/s" },
      { 0x05, "300 bit/s" },
      { 0x06, "600 bit/s" },
      { 0x07, "1200 bit/s" },
      { 0x08, "2400 bit/s" },
      { 0x09, "4800 bit/s" },
      { 0x0A, "9600 bit/s" },
      { 0x0B, "19200 bit/s" },
      { 0x0C, "48000 bit/s" },
      { 0x0D, "64000 bit/s" },
      { 0,    NULL }
};

static void
dissect_q931_information_rate_ie(tvbuff_t *tvb, int offset, int len,
    proto_tree *tree)
{
      if (len != 4) {
            proto_tree_add_text(tree, tvb, offset, len,
                "Information rate: length is %d, should be 4", len);
            return;
      }
      proto_tree_add_text(tree, tvb, offset + 0, 1,
          "Incoming information rate: %s",
          val_to_str(tvb_get_guint8(tvb, offset + 0) & 0x1F,
            q931_throughput_class_vals, "Unknown (0x%02X)"));
      proto_tree_add_text(tree, tvb, offset + 1, 1,
          "Outgoing information rate: %s",
          val_to_str(tvb_get_guint8(tvb, offset + 1) & 0x1F,
            q931_throughput_class_vals, "Unknown (0x%02X)"));
      proto_tree_add_text(tree, tvb, offset + 2, 1,
          "Minimum incoming information rate: %s",
          val_to_str(tvb_get_guint8(tvb, offset + 2) & 0x1F,
            q931_throughput_class_vals, "Unknown (0x%02X)"));
      proto_tree_add_text(tree, tvb, offset + 3, 1,
          "Minimum outgoing information rate: %s",
          val_to_str(tvb_get_guint8(tvb, offset + 3) & 0x1F,
            q931_throughput_class_vals, "Unknown (0x%02X)"));
}

static int
dissect_q931_guint16_value(tvbuff_t *tvb, int offset, int len,
    proto_tree *tree, const char *label)
{
      guint8 octet;
      guint16 value;
      int value_len;

      value_len = 0;

      octet = tvb_get_guint8(tvb, offset);
      if (octet & Q931_IE_VL_EXTENSION) {
            /*
             * Only one octet long - error.
             */
            goto bad_length;
      }
      value = (octet & 0x3) << 14;
      offset += 1;
      len -= 1;
      value_len++;

      if (len == 0) {
            /*
             * We've reached the end of the information element - error.
             */
            goto past_end;
      }
      octet = tvb_get_guint8(tvb, offset);
      if (octet & Q931_IE_VL_EXTENSION) {
            /*
             * Only two octets long - error.
             */
            goto bad_length;
      }
      value |= (octet & 0x7F) << 7;
      offset += 1;
      len -= 1;
      value_len++;

      if (len == 0) {
            /*
             * We've reached the end of the information element - error.
             */
            goto past_end;
      }
      octet = tvb_get_guint8(tvb, offset);
      if (!(octet & Q931_IE_VL_EXTENSION)) {
            /*
             * More than three octets long - error.
             */
            goto bad_length;
      }
      value |= (octet & 0x7F);
      offset += 1;
      len -= 1;
      value_len++;

      proto_tree_add_text(tree, tvb, offset, value_len, "%s: %u ms", label,
          value);
      return value_len;

past_end:
      proto_tree_add_text(tree, tvb, offset, len,
          "%s goes past end of information element", label);
      return -1;

bad_length:
      proto_tree_add_text(tree, tvb, offset, len, "%s isn't 3 octets long",
          label);
      return -1;
}

/*
 * Dissect an End-to-end transit delay information element.
 */
static void
dissect_q931_e2e_transit_delay_ie(tvbuff_t *tvb, int offset, int len,
    proto_tree *tree)
{
      int value_len;

      if (len == 0)
            return;
      value_len = dissect_q931_guint16_value(tvb, offset, len, tree,
          "Cumulative transit delay");
      if (value_len < 0)
            return;     /* error */
      offset += value_len;
      len -= value_len;

      if (len == 0)
            return;
      value_len = dissect_q931_guint16_value(tvb, offset, len, tree,
          "Requested end-to-end transit delay");
      if (value_len < 0)
            return;     /* error */
      offset += value_len;
      len -= value_len;

      if (len == 0)
            return;
      value_len = dissect_q931_guint16_value(tvb, offset, len, tree,
          "Maximum end-to-end transit delay");
}

/*
 * Dissect a Transit delay selection and indication information element.
 */
static void
dissect_q931_td_selection_and_int_ie(tvbuff_t *tvb, int offset, int len,
    proto_tree *tree)
{
      if (len == 0)
            return;
      dissect_q931_guint16_value(tvb, offset, len, tree,
          "Transit delay");
}

/*
 * Dissect a Packet layer binary parameters information element.
 */
static const value_string q931_fast_selected_vals[] = {
      { 0x00, "Fast select not requested" },
      { 0x08, "Fast select not requested" },
      { 0x10, "Fast select requested with no restriction of response" },
      { 0x18, "Fast select requested with restrictions of response" },
      { 0x00, NULL }
};

static void
dissect_q931_pl_binary_parameters_ie(tvbuff_t *tvb, int offset, int len,
    proto_tree *tree)
{
      guint8 octet;

      if (len == 0)
            return;
      octet = tvb_get_guint8(tvb, offset);
      proto_tree_add_text(tree, tvb, offset, 1,
          "Fast select: %s",
          val_to_str(octet & 0x18, q931_fast_selected_vals, "Unknown (0x%02X)"));
      proto_tree_add_text(tree, tvb, offset, 1,
          "%s",
          (octet & 0x04) ? "No request/request denied" :
                       "Request indicated/request accepted");
      proto_tree_add_text(tree, tvb, offset, 1,
          "%s confirmation",
          (octet & 0x02) ? "Link-by-link" : "End-to-end");
      proto_tree_add_text(tree, tvb, offset, 1,
          "Modulus %u sequencing",
          (octet & 0x01) ? 8 : 128);
}

/*
 * Dissect a Packet layer window size information element.
 */
static void
dissect_q931_pl_window_size_ie(tvbuff_t *tvb, int offset, int len,
    proto_tree *tree)
{
      if (len == 0)
            return;
      proto_tree_add_text(tree, tvb, offset, 1,
          "Forward value: %u", tvb_get_guint8(tvb, offset) & 0x7F);
      offset += 1;
      len -= 1;

      if (len == 0)
            return;
      proto_tree_add_text(tree, tvb, offset, 1,
          "Backward value: %u", tvb_get_guint8(tvb, offset) & 0x7F);
}

/*
 * Dissect a Packet size information element.
 */
static void
dissect_q931_packet_size_ie(tvbuff_t *tvb, int offset, int len,
    proto_tree *tree)
{
      if (len == 0)
            return;
      proto_tree_add_text(tree, tvb, offset, 1,
          "Forward value: %u", tvb_get_guint8(tvb, offset) & 0x7F);
      offset += 1;
      len -= 1;

      if (len == 0)
            return;
      proto_tree_add_text(tree, tvb, offset, 1,
          "Backward value: %u", tvb_get_guint8(tvb, offset) & 0x7F);
}

/*
 * Dissect a Closed user group information element.
 */
static const value_string q931_cug_indication_vals[] = {
      { 0x01, "Closed user group selection" },
      { 0x02, "Closed user group with outgoing access selection and indication" },
      { 0,    NULL }
};

static void
dissect_q931_cug_ie(tvbuff_t *tvb, int offset, int len, proto_tree *tree)
{
      if (len == 0)
            return;
      proto_tree_add_text(tree, tvb, offset, 1,
          "CUG indication: %s",
          val_to_str(tvb_get_guint8(tvb, offset) & 0x07,
            q931_cug_indication_vals, "Unknown (0x%02X)"));
      offset += 1;
      len -= 1;

      if (len == 0)
            return;
      proto_tree_add_text(tree, tvb, offset, len, "CUG index code: %s",
          tvb_format_text(tvb, offset, len));
}

/*
 * Dissect a Reverse charging indication information element.
 */
static const value_string q931_reverse_charging_indication_vals[] = {
      { 0x01, "Reverse charging requested" },
      { 0,    NULL }
};

static void
dissect_q931_reverse_charge_ind_ie(tvbuff_t *tvb, int offset, int len,
    proto_tree *tree)
{
      if (len == 0)
            return;
      proto_tree_add_text(tree, tvb, offset, 1,
          "Reverse charging indication: %s",
          val_to_str(tvb_get_guint8(tvb, offset) & 0x07,
            q931_reverse_charging_indication_vals, "Unknown (0x%02X)"));
}

/*
 * Dissect a (phone) number information element.
 */
static const value_string q931_number_type_vals[] = {
      { 0x0, "Unknown" },
      { 0x1, "International number" },
      { 0x2, "National number" },
      { 0x3, "Network specific number" },
      { 0x4, "Subscriber number" },
      { 0x6, "Abbreviated number" },
      { 0,    NULL }
};

static const value_string q931_numbering_plan_vals[] = {
      { 0x00, "Unknown" },
      { 0x01, "E.164 ISDN/telephony numbering" },
      { 0x03, "X.121 data numbering" },
      { 0x04, "F.69 Telex numbering" },
      { 0x08, "National standard numbering" },
      { 0x09, "Private numbering" },
      { 0,    NULL }
};

static const value_string q931_presentation_indicator_vals[] = {
      { 0x00, "Presentation allowed" },
      { 0x01, "Presentation restricted" },
      { 0x02, "Number not available due to interworking" },
      { 0,    NULL }
};

static const value_string q931_screening_indicator_vals[] = {
      { 0x00, "User-provided, not screened" },
      { 0x01, "User-provided, verified and passed" },
      { 0x02, "User-provided, verified and failed" },
      { 0x03, "Network-provided" },
      { 0,    NULL }
};

static const value_string q931_redirection_reason_vals[] = {
      { 0x00, "Unknown" },
      { 0x01, "Call forwarding busy or called DTE busy" },
      { 0x02, "Call forwarding no reply" },
      { 0x04, "Call deflection" },
      { 0x09, "Called DTE out of order" },
      { 0x0A, "Call forwarding by the called DTE" },
      { 0x0F, "Call forwarding unconditional or systematic call redirection" },
      { 0,    NULL }
};

static void
dissect_q931_number_ie(tvbuff_t *tvb, int offset, int len,
    proto_tree *tree, int hfindex, e164_info_t e164_info)
{
      guint8 octet;
      gint number_plan;

      if (len == 0)
            return;
      octet = tvb_get_guint8(tvb, offset);
      number_plan = octet & 0x0f;
      e164_info.nature_of_address = ( octet & 0x70 ) >> 4;
      proto_tree_add_uint(tree, hf_q931_numbering_plan, tvb, offset, 1, octet);
      proto_tree_add_uint(tree, hf_q931_number_type, tvb, offset, 1, octet);
      proto_tree_add_boolean(tree, hf_q931_extension_ind, tvb, offset, 1, octet);
      
      offset += 1;
      len -= 1;

      if (!(octet & Q931_IE_VL_EXTENSION)) {
            if (len == 0)
                  return;
            octet = tvb_get_guint8(tvb, offset);
            proto_tree_add_uint(tree, hf_q931_screening_ind, tvb, offset, 1, octet);
            proto_tree_add_uint(tree, hf_q931_presentation_ind, tvb, offset, 1, octet);
            proto_tree_add_boolean(tree, hf_q931_extension_ind, tvb, offset, 1, octet);
            offset += 1;
            len -= 1;
      }

      /*
       * XXX - only in a Redirecting number information element.
       */
      if (!(octet & Q931_IE_VL_EXTENSION)) {
            if (len == 0)
                  return;
            octet = tvb_get_guint8(tvb, offset);
            proto_tree_add_text(tree, tvb, offset, 1,
                "Reason for redirection: %s",
                val_to_str(octet & 0x0F, q931_redirection_reason_vals,
                  "Unknown (0x%X)"));
            offset += 1;
            len -= 1;
      }

      if (len == 0)
            return;
      proto_tree_add_item(tree, hfindex, tvb, offset, len, FALSE);
      proto_item_append_text(proto_tree_get_parent(tree), ": '%s'", tvb_format_text(tvb, offset, len));

      if ( number_plan == 1 ) {
            if ( e164_info.e164_number_type != NONE ){

                  e164_info.E164_number_str = tvb_get_ephemeral_string(tvb, offset, len);
                  e164_info.E164_number_length = len;
                  dissect_e164_number(tvb, tree, offset, len, e164_info);
            }
      }

    /* Collect q931_packet_info */
    if ( e164_info.e164_number_type == CALLING_PARTY_NUMBER && have_valid_q931_pi)
          q931_pi->calling_number = tvb_get_ephemeral_string(tvb, offset, len);
    if ( e164_info.e164_number_type == CALLED_PARTY_NUMBER && have_valid_q931_pi)
          q931_pi->called_number = tvb_get_ephemeral_string(tvb, offset, len);
}

/*
 * Dissect a party subaddress information element.
 */
static const value_string q931_subaddress_type_vals[] = {
      { 0x00, "X.213/ISO 8348 Add.2 NSAP" },
      { 0x20, "User-specified" },
      { 0,    NULL }
};

static const value_string q931_odd_even_indicator_vals[] = {
      { 0x00, "Even number of address signals" },
      { 0x10, "Odd number of address signals" },
      { 0,    NULL }
};

static void
dissect_q931_party_subaddr_ie(tvbuff_t *tvb, int offset, int len,
    proto_tree *tree)
{
      guint8 octet;

      if (len == 0)
            return;
      octet = tvb_get_guint8(tvb, offset);
      proto_tree_add_text(tree, tvb, offset, 1,
          "Type of subaddress: %s",
          val_to_str(octet & 0x70, q931_subaddress_type_vals,
            "Unknown (0x%02X)"));
      proto_tree_add_text(tree, tvb, offset, 1,
          "Odd/even indicator: %s",
          val_to_str(octet & 0x10, q931_odd_even_indicator_vals,
            "Unknown (0x%02X)"));
      offset += 1;
      len -= 1;

      if (len == 0)
            return;
      proto_tree_add_text(tree, tvb, offset, len, "Subaddress: %s",
          tvb_bytes_to_str(tvb, offset, len));
}

/*
 * Dissect a Restart indicator information element.
 */
static const value_string q931_restart_indicator_class_vals[] = {
      { 0x00, "Indicated channels" },
      { 0x06, "Single interface" },
      { 0x07, "All interfaces" },
      { 0,    NULL }
};

static void
dissect_q931_restart_indicator_ie(tvbuff_t *tvb, int offset, int len,
    proto_tree *tree)
{
      if (len != 1) {
            proto_tree_add_text(tree, tvb, offset, len,
                "Restart indicator: length is %d, should be 1", len);
            return;
      }
      proto_tree_add_text(tree, tvb, offset, 1,
          "Restart indicator: %s",
          val_to_str(tvb_get_guint8(tvb, offset) & 0x07,
            q931_restart_indicator_class_vals, "Unknown (0x%02X)"));
}

/*
 * Dissect a High-layer compatibility information element.
 */
#define     Q931_AUDIOVISUAL  0x60
static const value_string q931_high_layer_characteristics_vals[] = {
      { 0x01,             "Telephony" },
      { 0x04,             "F.182 Facsimile Group 2/3" },
      { 0x21,             "F.184 Facsimile Group 4 Class I" },
      { 0x24,             "F.230 Teletex, basic and mixed mode, and F.184 Facsimile Group 4, Classes II and III" },
      { 0x28,             "F.220 Teletex, basic and processable mode" },
      { 0x31,             "F.200 Teletex, basic mode" },
      { 0x32,             "F.300 and T.102 syntax-based Videotex" },
      { 0x33,             "F.300 and T.101 international Videotex interworking" },
      { 0x35,             "F.60 Telex" },
      { 0x38,             "X.400 Message Handling Systems" },
      { 0x41,             "X.200 OSI application" },
      { 0x42,             "FTAM application" },
      { 0x5E,             "Reserved for maintenance" },
      { 0x5F,             "Reserved for management" },
      { Q931_AUDIOVISUAL, "F.720/F.821 and F.731 Profile 1a videotelephony" },
      { 0x61,             "F.702 and F.731 Profile 1b videoconferencing" },
      { 0x62,             "F.702 and F.731 audiographic conferencing" },
      { 0,                NULL }
};

static const value_string q931_audiovisual_characteristics_vals[] = {
      { 0x01, "Capability set of initial channel of H.221" },
      { 0x02, "Capability set of subsequent channel of H.221" },
      { 0x21, "Capability set of initial channel of an active 3.1kHz audio or speech call" },
      { 0x00, NULL }
};

void
dissect_q931_high_layer_compat_ie(tvbuff_t *tvb, int offset, int len,
    proto_tree *tree)
{
      guint8 octet;
      guint8 coding_standard;
      guint8 characteristics;

      if (len == 0)
            return;
      octet = tvb_get_guint8(tvb, offset);
      coding_standard = octet & 0x60;
      proto_tree_add_uint(tree, hf_q931_coding_standard, tvb, offset, 1, octet);
      offset += 1;
      len -= 1;
      if (coding_standard != Q931_ITU_STANDARDIZED_CODING) {
            /*
             * We don't know how the call state is encoded,
             * so just dump it as data and be done with it.
             */
            proto_tree_add_text(tree, tvb, offset,
                len, "Data: %s",
                tvb_bytes_to_str(tvb, offset, len));
            return;
      }

      if (len == 0)
            return;
      octet = tvb_get_guint8(tvb, offset);
      characteristics = octet & 0x7F;
      proto_tree_add_text(tree, tvb, offset, 1,
          "High layer characteristics identification: %s",
          val_to_str(characteristics, q931_high_layer_characteristics_vals,
           "Unknown (0x%02X)"));
      offset += 1;
      len -= 1;

      if (!(octet & Q931_IE_VL_EXTENSION)) {
            if (len == 0)
                  return;
            octet = tvb_get_guint8(tvb, offset);
            if (characteristics == Q931_AUDIOVISUAL) {
                  proto_tree_add_text(tree, tvb, offset, 1,
                      "Extended audiovisual characteristics identification: %s",
                      val_to_str(octet & 0x7F,
                        q931_audiovisual_characteristics_vals,
                        "Unknown (0x%02X)"));
            } else {
                  proto_tree_add_text(tree, tvb, offset, 1,
                      "Extended high layer characteristics identification: %s",
                      val_to_str(octet & 0x7F,
                        q931_high_layer_characteristics_vals,
                        "Unknown (0x%02X)"));
            }
      }
}


/*
 * Dissect a User-user information element.
 */
#define     Q931_PROTOCOL_DISCRIMINATOR_IA5           0x04
#define Q931_PROTOCOL_DISCRIMINATOR_ASN1  0x05

const value_string q931_protocol_discriminator_vals[] = {
      { 0x00,                             "User-specific protocol" },
      { 0x01,                             "OSI high layer protocols" },
      { 0x02,                             "X.244" },
      { Q931_PROTOCOL_DISCRIMINATOR_IA5,  "IA5 characters" },
      { Q931_PROTOCOL_DISCRIMINATOR_ASN1, "X.208 and X.209 coded user information" },
      { 0x07,                             "V.120 rate adaption" },
      { 0x08,                             "Q.931/I.451 user-network call control messages" },
      { 0,                          NULL }
};

void
dissect_q931_user_user_ie(tvbuff_t *tvb, int offset, int len,
    proto_tree *tree)
{
      guint8 octet;

      if (len == 0)
            return;
      octet = tvb_get_guint8(tvb, offset);
      proto_tree_add_text(tree, tvb, offset, 1,
          "Protocol discriminator: %s",
          val_to_str(octet, q931_protocol_discriminator_vals,
          "Unknown (0x%02x)"));
      offset += 1;
      len -= 1;

      if (len == 0)
            return;
      switch (octet) {

      case Q931_PROTOCOL_DISCRIMINATOR_IA5:
            proto_tree_add_text(tree, tvb, offset, len, "User information: %s",
                tvb_format_text(tvb, offset, len));
            break;

      default:
            proto_tree_add_text(tree, tvb, offset, len, "User information: %s",
                tvb_bytes_to_str(tvb, offset, len));
            break;
      }
}

/*
 * Dissect information elements consisting of ASCII^H^H^H^H^HIA5 text.
 */
static void
dissect_q931_ia5_ie(tvbuff_t *tvb, int offset, int len, proto_tree *tree,
    const char *label)
{
      if (len != 0) {
            proto_tree_add_text(tree, tvb, offset, len, "%s: %s", label,
                tvb_format_text(tvb, offset, len));
            proto_item_append_text(proto_tree_get_parent(tree), "  '%s'", tvb_format_text(tvb, offset, len));
      }
}

static void
dissect_q931_pdu(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
    gboolean is_tpkt)
{
      int         offset = 0;
      proto_tree  *q931_tree = NULL;
      proto_tree  *ie_tree = NULL;
      proto_item  *ti, *ti_ie;
      guint8            call_ref_len;
      guint8            call_ref[15];
      guint32           call_ref_val;
      guint8            message_type, segmented_message_type;
      guint8            info_element;
      guint16           info_element_len;
      gboolean    more_frags; 
      guint32           frag_len;
      fragment_data *fd_head;
      tvbuff_t *next_tvb = NULL;

      q931_pi=ep_alloc(sizeof(q931_packet_info));

      /* Init struct for collecting q931_packet_info */
      reset_q931_packet_info(q931_pi);
      have_valid_q931_pi=TRUE;

      if (check_col(pinfo->cinfo, COL_PROTOCOL))
            col_set_str(pinfo->cinfo, COL_PROTOCOL, "Q.931");

      if (tree) {
            ti = proto_tree_add_item(tree, proto_q931, tvb, offset, -1,
                FALSE);
            q931_tree = proto_item_add_subtree(ti, ett_q931);

            dissect_q931_protocol_discriminator(tvb, offset, q931_tree);
      }
      offset += 1;
      call_ref_len = tvb_get_guint8(tvb, offset) & 0xF;     /* XXX - do as a bit field? */
      if (q931_tree != NULL)
            proto_tree_add_uint(q931_tree, hf_q931_call_ref_len, tvb, offset, 1, call_ref_len);
      offset += 1;
      switch (call_ref_len) {
            case 0: call_ref_val = 0; break;
            case 1:     call_ref_val = tvb_get_guint8(tvb, offset);     break;
            case 2:     call_ref_val = tvb_get_ntohs(tvb, offset); break;
            case 3:     call_ref_val = tvb_get_ntoh24(tvb, offset); break;
            default: call_ref_val = tvb_get_ntohl(tvb, offset);
      } 
      if (call_ref_len != 0) {
            tvb_memcpy(tvb, call_ref, offset, call_ref_len);
            if (q931_tree != NULL) {
                  proto_tree_add_boolean(q931_tree, hf_q931_call_ref_flag,
                      tvb, offset, 1, (call_ref[0] & 0x80) != 0);
                  call_ref[0] &= 0x7F;
                  proto_tree_add_bytes(q931_tree, hf_q931_call_ref,
                      tvb, offset, call_ref_len, call_ref);
            } else
            {       /* info for the tap */
                  call_ref[0] &= 0x7F;
            }
            /* XXX - Should crv be something besides a guint32? */
            g_memmove(&(q931_pi->crv), call_ref, call_ref_len > sizeof(q931_pi->crv) ? sizeof(q931_pi->crv) : call_ref_len );
            offset += call_ref_len;
      }
      message_type = tvb_get_guint8(tvb, offset);
      if(have_valid_q931_pi) {
            q931_pi->message_type = message_type;
      }
      if (check_col(pinfo->cinfo, COL_INFO)) {
            col_add_str(pinfo->cinfo, COL_INFO,
                val_to_str(message_type, q931_message_type_vals,
                  "Unknown message type (0x%02X)"));
      }
      if (q931_tree != NULL)
            proto_tree_add_uint(q931_tree, hf_q931_message_type, tvb, offset, 1, message_type);
      offset += 1;

      /*
       * And now for the information elements....
       */
      if ((message_type != Q931_SEGMENT) || !q931_reassembly || 
                  (tvb_reported_length_remaining(tvb, offset) <= 4)) {
            dissect_q931_IEs(tvb, pinfo, tree, q931_tree, is_tpkt, offset, 0);
            return;
      }
      info_element = tvb_get_guint8(tvb, offset);
      info_element_len = tvb_get_guint8(tvb, offset + 1);
      if ((info_element != Q931_IE_SEGMENTED_MESSAGE) || (info_element_len < 2)) {
            dissect_q931_IEs(tvb, pinfo, tree, q931_tree, is_tpkt, offset, 0);
            return;
      }
      /* Segmented message IE */
      ti_ie = proto_tree_add_text(q931_tree, tvb, offset, 1+1+info_element_len, "%s",
                            val_to_str(info_element, q931_info_element_vals[0], "Unknown information element (0x%02X)"));
      ie_tree = proto_item_add_subtree(ti_ie, ett_q931_ie);
      proto_tree_add_text(ie_tree, tvb, offset, 1, "Information element: %s",
                            val_to_str(info_element, q931_info_element_vals[0], "Unknown (0x%02X)"));
      proto_tree_add_text(ie_tree, tvb, offset + 1, 1, "Length: %u", info_element_len);
      dissect_q931_segmented_message_ie(tvb, offset + 2, info_element_len, ie_tree);
      more_frags = (tvb_get_guint8(tvb, offset + 2) & 0x7F) != 0;
      segmented_message_type = tvb_get_guint8(tvb, offset + 3);
      if (check_col(pinfo->cinfo, COL_INFO)) {
            col_append_fstr(pinfo->cinfo, COL_INFO, " of %s",
                val_to_str(segmented_message_type, q931_message_type_vals, "Unknown message type (0x%02X)"));
      }
      offset += 1 + 1 + info_element_len;
      /* Reassembly */
      frag_len = tvb_length_remaining(tvb, offset);
      fd_head = fragment_add_seq_next(tvb, offset, pinfo, call_ref_val,
                                                      q931_fragment_table, q931_reassembled_table,
                                                      frag_len, more_frags);
      if (fd_head) {
            if (pinfo->fd->num == fd_head->reassembled_in) {  /* last fragment */
                  if (fd_head->next != NULL) {  /* 2 or more segments */
                        next_tvb = tvb_new_real_data(fd_head->data, fd_head->len, fd_head->len);
                        tvb_set_child_real_data_tvbuff(tvb, next_tvb);
                        add_new_data_source(pinfo, next_tvb, "Reassembled Q.931 IEs");
                        /* Show all fragments. */
                if (tree) {
                    proto_item *frag_tree_item;
                    show_fragment_seq_tree(fd_head, &q931_frag_items, q931_tree, pinfo, next_tvb, &frag_tree_item);
                }
                  } else {  /* only 1 segment */
                        next_tvb = tvb_new_subset(tvb, offset, -1, -1);
                  }
                  if (check_col(pinfo->cinfo, COL_INFO)) {
                        col_add_fstr(pinfo->cinfo, COL_INFO, "%s [reassembled]",
                            val_to_str(segmented_message_type, q931_message_type_vals, "Unknown message type (0x%02X)"));
                  }
            } else {
                  if (tree) proto_tree_add_uint(q931_tree, hf_q931_reassembled_in, tvb, offset, frag_len, fd_head->reassembled_in);
            }
      }
      if (next_tvb)
            dissect_q931_IEs(next_tvb, pinfo, tree, q931_tree, is_tpkt, 0, 0);
}

static const value_string q931_codeset_vals[] = {
      { 0x00, "Q.931 information elements" },
      { 0x04, "Information elements for ISO/IEC use" },
      { 0x05, "Information elements for national use" },
      { 0x06, "Information elements specific to the local network" },
      { 0x07, "User-specific information elements" },
      { 0x00, NULL },
};

static void
dissect_q931_IEs(tvbuff_t *tvb, packet_info *pinfo, proto_tree *root_tree,
    proto_tree *q931_tree, gboolean is_tpkt, int offset, int initial_codeset)
{
      proto_item  *ti;
      proto_tree  *ie_tree = NULL;
      guint8            info_element;
      guint8            dummy;
      guint16           info_element_len;
      int         codeset, locked_codeset;
      gboolean    non_locking_shift, first_segment;
      tvbuff_t    *h225_tvb, *next_tvb;
      e164_info_t e164_info;
      e164_info.e164_number_type = NONE;

      codeset = locked_codeset = initial_codeset;
      non_locking_shift = TRUE;
      first_segment = FALSE;
      while (tvb_reported_length_remaining(tvb, offset) > 0) {
            info_element = tvb_get_guint8(tvb, offset);

            /* Check for the codeset shift */
            if ((info_element & Q931_IE_SO_MASK) &&
                ((info_element & Q931_IE_SO_IDENTIFIER_MASK) == Q931_IE_SHIFT)) {
                  non_locking_shift = info_element & Q931_IE_SHIFT_NON_LOCKING;
                  codeset = info_element & Q931_IE_SHIFT_CODESET;
                  if (!non_locking_shift)
                        locked_codeset = codeset;
                  if (q931_tree != NULL) {
                        proto_tree_add_text(q931_tree, tvb, offset, 1,
                            "%s shift to codeset %u: %s",
                            (non_locking_shift ? "Non-locking" : "Locking"),
                            codeset,
                            val_to_str(codeset, q931_codeset_vals,
                              "Unknown (0x%02X)"));
                  }
                  offset += 1;
                  continue;
            }

            /*
             * Check for the single-octet IEs.
             */
            if (info_element & Q931_IE_SO_MASK) {
                  /*
                   * Check for subdissectors for this IE or
                   * for all IEs in this codeset.
                   */
                  if (dissector_get_port_handle(codeset_dissector_table, codeset) ||
                      dissector_get_port_handle(ie_dissector_table, (codeset << 8) | (info_element & Q931_IE_SO_IDENTIFIER_MASK))) {
                        next_tvb = tvb_new_subset (tvb, offset, 1, 1);
                        if (dissector_try_port(ie_dissector_table, (codeset << 8) | (info_element & Q931_IE_SO_IDENTIFIER_MASK), next_tvb, pinfo, q931_tree) ||
                            dissector_try_port(codeset_dissector_table, codeset, next_tvb, pinfo, q931_tree)) {
                              offset += 1;
                              codeset = locked_codeset;
                              continue;
                        }
                  }

                  switch ((codeset << 8) | (info_element & Q931_IE_SO_IDENTIFIER_MASK)) {

                  case CS0 | Q931_IE_MORE_DATA_OR_SEND_COMP:
                        switch (info_element) { 

                        case Q931_IE_MORE_DATA:
                              if (q931_tree != NULL) {
                                    proto_tree_add_text(q931_tree, tvb, offset, 1,
                                        "More data");
                              }
                              break;

                        case Q931_IE_SENDING_COMPLETE:
                              if (q931_tree != NULL) {
                                    proto_tree_add_text(q931_tree, tvb, offset, 1,
                                        "Sending complete");
                              }
                              break;

                        default:
                              if (q931_tree != NULL) {
                                    proto_tree_add_text(q931_tree, tvb, offset, 1,
                                        "Unknown information element (0x%02X)",
                                        info_element);
                              }
                              break;
                        }
                        break;

                  case CS0 | Q931_IE_CONGESTION_LEVEL:
                        if (q931_tree != NULL) {
                              proto_tree_add_text(q931_tree, tvb, offset, 1,
                                  "Congestion level: %s",
                                  val_to_str(info_element & Q931_IE_SO_IE_MASK,
                                    q931_congestion_level_vals,
                                    "Unknown (0x%X)"));
                        }
                        break;

                  case CS0 | Q931_IE_REPEAT_INDICATOR:
                        if (q931_tree != NULL) {
                              proto_tree_add_text(q931_tree, tvb, offset, 1,
                                  "Repeat indicator: %s",
                                  val_to_str(info_element & Q931_IE_SO_IE_MASK,
                                q931_repeat_indication_vals,
                                    "Unknown (0x%X)"));
                        }
                        break;

                  default:
                        if (q931_tree != NULL) {
                              proto_tree_add_text(q931_tree, tvb, offset, 1,
                                  "Unknown information element (0x%02X)",
                                  info_element);
                        }
                        break;
                  }
                  offset += 1;
                  codeset = locked_codeset;
                  continue;
            }

            /*
             * Variable-length IE.
             *
             * According to page 18 from Recommendation H.225.0 :
             * " Length of user-user contents contents
             * - Shall be 2 octets instead of 1 (as in Figure 4-36/Q.931)"
             *
             * We assume that if this is Q.931-over-TPKT, it might
             * be H.225 traffic, and check for the IE being a user-user
             * IE with ASN.1 encoding of the user information.
             */
            if (is_tpkt && tvb_bytes_exist(tvb, offset, 4) &&
                codeset == 0 && tvb_get_guint8(tvb, offset) == Q931_IE_USER_USER &&
                tvb_get_guint8(tvb, offset + 3) == Q931_PROTOCOL_DISCRIMINATOR_ASN1)  {
                  info_element_len = tvb_get_ntohs(tvb, offset + 1);
                  if (q931_tree != NULL) {
                        ti = proto_tree_add_text(q931_tree, tvb, offset,
                            1+2+info_element_len, "%s",
                            val_to_str(info_element,
                              q931_info_element_vals[codeset],
                              "Unknown information element (0x%02X)"));
                        ie_tree = proto_item_add_subtree(ti,
                            ett_q931_ie);
                        proto_tree_add_text(ie_tree, tvb, offset, 1,
                            "Information element: %s",
                            val_to_str(info_element,
                              q931_info_element_vals[codeset], "Unknown (0x%02X)"));
                        proto_tree_add_text(ie_tree, tvb, offset + 1,
                            2, "Length: %u", info_element_len);
                        proto_tree_add_text(ie_tree, tvb, offset + 3,
                            1, "Protocol discriminator: %s",
                            val_to_str(tvb_get_guint8(tvb, offset + 3),
                              q931_protocol_discriminator_vals,
                              "Unknown (0x%02x)"));
                  }

                  if (info_element_len > 1) {
                        /*
                         * If we don't desegment limit the length 
                         * to the actual size in the frame
                         */
                        if (!pinfo->can_desegment) {
                              info_element_len = min(info_element_len, tvb_length_remaining(tvb, offset + 3));
                        }
                        /*
                         * Do we have a handle for the H.225
                         * dissector?
                         */
                        if (h225_handle != NULL) {
                              /*
                               * Yes - call it, regardless of
                               * whether we're building a
                               * protocol tree or not.
                               */
                              h225_tvb = tvb_new_subset(tvb,
                                  offset + 4, info_element_len - 1,
                                  info_element_len - 1);
                              call_dissector(h225_handle, h225_tvb,
                                  pinfo, root_tree);
                        } else {
                              /*
                               * No - just show it as "User
                               * information" (if "ie_tree" is
                               * null, this won't add anything).
                               */
                              proto_tree_add_text(ie_tree, tvb,
                                  offset + 4, info_element_len - 1,
                                  "User information: %s",
                                  tvb_bytes_to_str(tvb, offset + 4,
                                    info_element_len - 1));
                        }
                  }
                  offset += 1 + 2 + info_element_len;
            } else {
                  info_element_len = tvb_get_guint8(tvb, offset + 1);

                  if (first_segment && (tvb_reported_length_remaining(tvb, offset + 2) < info_element_len)) {  /* incomplete IE at the end of the 1st segment */
                        proto_tree_add_text(q931_tree, tvb, offset, tvb_reported_length_remaining(tvb, offset), "Incomplete IE in the 1st segment");
                        break;
                  }

                  /*
                   * Check for subdissectors for this IE or
                   * for all IEs in this codeset.
                   */
                  if (dissector_get_port_handle(codeset_dissector_table, codeset) ||
                      dissector_get_port_handle(ie_dissector_table, (codeset << 8) | info_element)) {
                        next_tvb = tvb_new_subset (tvb, offset, info_element_len + 2, info_element_len + 2);
                        if (dissector_try_port(ie_dissector_table, (codeset << 8) | info_element, next_tvb, pinfo, q931_tree) ||
                            dissector_try_port(codeset_dissector_table, codeset, next_tvb, pinfo, q931_tree)) {
                              offset += 2 + info_element_len;
                              codeset = locked_codeset;
                              continue;
                        }
                  }

                  ti = proto_tree_add_text(q931_tree, tvb, offset, 1+1+info_element_len, "%s",
                            val_to_str(info_element, q931_info_element_vals[codeset], "Unknown information element (0x%02X)"));
                  ie_tree = proto_item_add_subtree(ti, ett_q931_ie);
                  proto_tree_add_text(ie_tree, tvb, offset, 1, "Information element: %s",
                            val_to_str(info_element, q931_info_element_vals[codeset], "Unknown (0x%02X)"));
                  proto_tree_add_text(ie_tree, tvb, offset + 1, 1, "Length: %u", info_element_len);

                  if (((codeset << 8) | info_element) == (CS0 | Q931_IE_SEGMENTED_MESSAGE)) {
                        dissect_q931_segmented_message_ie(tvb, offset + 2, info_element_len, ie_tree);
                        if (check_col(pinfo->cinfo, COL_INFO)) {
                              col_append_fstr(pinfo->cinfo, COL_INFO, " of %s",
                                  val_to_str(tvb_get_guint8(tvb, offset + 3), q931_message_type_vals, "Unknown message type (0x%02X)"));
                        }
                        if (tvb_get_guint8(tvb, offset + 2) & 0x80) {  /* the 1st segment */
                              first_segment = TRUE;
                        } else {  /* not the 1st segment */
                              proto_tree_add_text(q931_tree, tvb, offset + 4, tvb_reported_length_remaining(tvb, offset + 4), "Message segment");
                              info_element_len += tvb_reported_length_remaining(tvb, offset + 4);
                        }
                  } else {
                        /*
                         * For the calling number, called number,
                         * and release cause IEs, don't check
                         * for the tree being null, as
                         * the dissectors for those IEs also
                         * supply information for the tap used
                         * in VoIP calls.
                         */
                        switch ((codeset << 8) | info_element) {

                        case CS0 | Q931_IE_BEARER_CAPABILITY:
                        case CS0 | Q931_IE_LOW_LAYER_COMPAT:
                              if (q931_tree != NULL) {
                                    dissect_q931_bearer_capability_ie(tvb,
                                          offset + 2, info_element_len,
                                          ie_tree);
                              }
                              break;

                        case CS0 | Q931_IE_CAUSE:
                              dissect_q931_cause_ie(tvb,
                                    offset + 2, info_element_len,
                                    ie_tree,
                                    hf_q931_cause_value, &dummy);
                              break;

                        case CS0 | Q931_IE_CALL_STATE:
                              if (q931_tree != NULL) {
                                    dissect_q931_call_state_ie(tvb,
                                          offset + 2, info_element_len,
                                          ie_tree);
                              }
                              break;

                        case CS0 | Q931_IE_CHANNEL_IDENTIFICATION:
                              if (q931_tree != NULL) {
                                    dissect_q931_channel_identification_ie(
                                          tvb, offset + 2, info_element_len,
                                          ie_tree);
                              }
                              break;

                        case CS0 | Q931_IE_PROGRESS_INDICATOR:
                              if (q931_tree != NULL) {
                                    dissect_q931_progress_indicator_ie(tvb,
                                          offset + 2, info_element_len,
                                          ie_tree);
                              }
                              break;

                        case CS0 | Q931_IE_NETWORK_SPECIFIC_FACIL:
                        case CS0 | Q931_IE_TRANSIT_NETWORK_SEL:
                              if (q931_tree != NULL) {
                                    dissect_q931_ns_facilities_ie(tvb,
                                          offset + 2, info_element_len,
                                          ie_tree);
                              }
                              break;

                        case CS0 | Q931_IE_NOTIFICATION_INDICATOR:
                              if (q931_tree != NULL) {
                                    dissect_q931_notification_indicator_ie(
                                          tvb, offset + 2, info_element_len,
                                          ie_tree);
                              }
                              break;

                        case CS0 | Q931_IE_DISPLAY:
                              if (q931_tree != NULL) {
                                    dissect_q931_ia5_ie(tvb, offset + 2,
                                          info_element_len, ie_tree,
                                          "Display information");
                              }
                              break;

                        case CS0 | Q931_IE_DATE_TIME:
                              if (q931_tree != NULL) {
                                    dissect_q931_date_time_ie(tvb,
                                          offset + 2, info_element_len,
                                          ie_tree);
                              }
                              break;

                        case CS0 | Q931_IE_KEYPAD_FACILITY:
                              if (q931_tree != NULL) {
                                    dissect_q931_ia5_ie(tvb, offset + 2,
                                          info_element_len, ie_tree,
                                          "Keypad facility");
                              }
                              break;

                        case CS0 | Q931_IE_SIGNAL:
                              if (q931_tree != NULL) {
                                    dissect_q931_signal_ie(tvb,
                                          offset + 2, info_element_len,
                                          ie_tree);
                              }
                              break;

                        case CS0 | Q931_IE_INFORMATION_RATE:
                              if (q931_tree != NULL) {
                                    dissect_q931_information_rate_ie(tvb,
                                          offset + 2, info_element_len,
                                          ie_tree);
                              }
                              break;

                        case CS0 | Q931_IE_E2E_TRANSIT_DELAY:
                              if (q931_tree != NULL) {
                                    dissect_q931_e2e_transit_delay_ie(tvb,
                                          offset + 2, info_element_len,
                                          ie_tree);
                              }
                              break;

                        case CS0 | Q931_IE_TD_SELECTION_AND_INT:
                              if (q931_tree != NULL) {
                                    dissect_q931_td_selection_and_int_ie(
                                          tvb, offset + 2, info_element_len,
                                          ie_tree);
                              }
                              break;

                        case CS0 | Q931_IE_PL_BINARY_PARAMETERS:
                              if (q931_tree != NULL) {
                                    dissect_q931_pl_binary_parameters_ie(
                                          tvb, offset + 2, info_element_len,
                                          ie_tree);
                              }
                              break;

                        case CS0 | Q931_IE_PL_WINDOW_SIZE:
                              if (q931_tree != NULL) {
                                    dissect_q931_pl_window_size_ie(tvb,
                                          offset + 2, info_element_len,
                                          ie_tree);
                              }
                              break;

                        case CS0 | Q931_IE_PACKET_SIZE:
                              if (q931_tree != NULL) {
                                    dissect_q931_packet_size_ie(tvb,
                                          offset + 2, info_element_len,
                                          ie_tree);
                              }
                              break;

                        case CS0 | Q931_IE_CUG:
                              if (q931_tree != NULL) {
                                    dissect_q931_cug_ie(tvb,
                                          offset + 2, info_element_len,
                                          ie_tree);
                              }
                              break;

                        case CS0 | Q931_IE_REVERSE_CHARGE_IND:
                              if (q931_tree != NULL) {
                                    dissect_q931_reverse_charge_ind_ie(tvb,
                                          offset + 2, info_element_len,
                                          ie_tree);
                              }
                              break;

                        case CS0 | Q931_IE_CONNECTED_NUMBER_DEFAULT:
                              if (q931_tree != NULL) {
                                    dissect_q931_number_ie(tvb,
                                          offset + 2, info_element_len,
                                          ie_tree,
                                          hf_q931_connected_number, e164_info);
                              }
                              break;


                        case CS0 | Q931_IE_CALLING_PARTY_NUMBER:
                              e164_info.e164_number_type = CALLING_PARTY_NUMBER;
                              dissect_q931_number_ie(tvb,
                                    offset + 2, info_element_len,
                                    ie_tree,
                                    hf_q931_calling_party_number, e164_info);
                              break;

                        case CS0 | Q931_IE_CALLED_PARTY_NUMBER:
                              e164_info.e164_number_type = CALLED_PARTY_NUMBER;
                              dissect_q931_number_ie(tvb,
                                    offset + 2, info_element_len,
                                    ie_tree,
                                    hf_q931_called_party_number, e164_info);
                              break;

                        case CS0 | Q931_IE_CALLING_PARTY_SUBADDR:
                        case CS0 | Q931_IE_CALLED_PARTY_SUBADDR:
                              if (q931_tree != NULL) {
                                    dissect_q931_party_subaddr_ie(tvb,
                                          offset + 2, info_element_len,
                                          ie_tree);
                              }
                              break;

                        case CS0 | Q931_IE_REDIRECTING_NUMBER:
                              if (q931_tree != NULL) {
                                    dissect_q931_number_ie(tvb,
                                          offset + 2, info_element_len,
                                          ie_tree,
                                          hf_q931_redirecting_number, e164_info);
                              }
                              break;

                        case CS0 | Q931_IE_RESTART_INDICATOR:
                              if (q931_tree != NULL) {
                                    dissect_q931_restart_indicator_ie(tvb,
                                          offset + 2, info_element_len,
                                          ie_tree);
                              }
                              break;

                        case CS0 | Q931_IE_HIGH_LAYER_COMPAT:
                              if (q931_tree != NULL) {
                                    dissect_q931_high_layer_compat_ie(tvb,
                                          offset + 2, info_element_len,
                                          ie_tree);
                              }
                              break;

                        case CS0 | Q931_IE_USER_USER:
                              if (q931_tree != NULL) {
                                    dissect_q931_user_user_ie(tvb,
                                          offset + 2, info_element_len,
                                          ie_tree);
                              }
                              break;

                        default:
                              if (q931_tree != NULL) {
                                    proto_tree_add_text(ie_tree, tvb,
                                          offset + 2, info_element_len,
                                          "Data: %s",
                                          bytes_to_str(
                                            tvb_get_ptr(tvb, offset + 2,
                                                  info_element_len),
                                            info_element_len));
                              }
                              break;
                        }
                  }
                  offset += 1 + 1 + info_element_len;
            }
            codeset = locked_codeset;
      }
      if(have_valid_q931_pi) {
            tap_queue_packet(q931_tap, pinfo, q931_pi);
      }
      have_valid_q931_pi=FALSE;
}

/*
 * Q.931-over-TPKT-over-TCP.
 */
static gboolean
dissect_q931_tpkt_heur(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
      int lv_tpkt_len;

      /*
       * Check whether this looks like a TPKT-encapsulated
       * Q.931 packet.
       *
       * The minimum length of a Q.931 message is 3:
       * 1 byte for the protocol discriminator,
       * 1 for the call_reference length,
       * and one for the message type.
       */
      lv_tpkt_len = is_tpkt(tvb, 3);
      if (lv_tpkt_len == -1) {
            /*
             * It's not a TPKT packet; reject it.
             */
            return FALSE;
      }

      /*
       * If this segment is *exactly* the length of a TPKT header,
       * we assume that, as it looks like a TPKT header, it
       * is one, and that the code put a TPKT header in one
       * segment and the rest of the PDU in another.
       */
      if (tvb_length(tvb) == 4) {
            /*
             * It is - call the "dissect TPKT over a TCP stream"
             * routine.
             */
            dissect_tpkt_encap(tvb, pinfo, tree, q931_desegment,
                q931_tpkt_pdu_handle);
            return TRUE;
      }

      /*
       * Well, we have more data than just the TPKT header;
       * check whether it looks like the beginning of a
       * Q.931 message.
       *
       * The minimum length of a Q.931 message is 3, as per the
       * above.
       *
       * Check that we have that many bytes past the TPKT header in
       * the tvbuff; we already know that the TPKT header says we
       * have that many bytes (as we passed 3 as the "min_len" argument
       * to "is_tpkt()").
       */
      if (!tvb_bytes_exist(tvb, 4, 3))
            return FALSE;

      /* Check the protocol discriminator */
      if (tvb_get_guint8(tvb, 4) != NLPID_Q_931) {
            /* Doesn't look like Q.931 inside TPKT */
            return FALSE;
      }

      /*
       * OK, it looks like Q.931-over-TPKT.
       * Call the "dissect TPKT over a TCP stream" routine.
       */
      dissect_tpkt_encap(tvb, pinfo, tree, q931_desegment,
          q931_tpkt_pdu_handle);

      return TRUE;
}

static void
dissect_q931_tpkt(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
      dissect_q931_tpkt_heur(tvb, pinfo, tree);
}

static void
dissect_q931_tpkt_pdu(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
      dissect_q931_pdu(tvb, pinfo, tree, TRUE);
}

static void
dissect_q931(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
      dissect_q931_pdu(tvb, pinfo, tree, FALSE);
}

static void
dissect_q931_ie_cs0(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
      dissect_q931_IEs(tvb, pinfo, NULL, tree, FALSE, 0, 0);
}

static void
dissect_q931_ie_cs7(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
      dissect_q931_IEs(tvb, pinfo, NULL, tree, FALSE, 0, 7);
}

static void 
q931_init(void) {
      /* Initialize the fragment and reassembly tables */
      fragment_table_init(&q931_fragment_table);
      reassembled_table_init(&q931_reassembled_table);
}

void
proto_register_q931(void)
{
      static hf_register_info hf[] = {
            { &hf_q931_discriminator,
              { "Protocol discriminator", "q931.disc", FT_UINT8, BASE_HEX, NULL, 0x0,
                  "", HFILL }},

            { &hf_q931_call_ref_len,
              { "Call reference value length", "q931.call_ref_len", FT_UINT8, BASE_DEC, NULL, 0x0,
                  "", HFILL }},

            { &hf_q931_call_ref_flag,
              { "Call reference flag", "q931.call_ref_flag", FT_BOOLEAN, BASE_NONE, TFS(&tfs_call_ref_flag), 0x0,
                  "", HFILL }},

            { &hf_q931_call_ref,
              { "Call reference value", "q931.call_ref", FT_BYTES, BASE_HEX, NULL, 0x0,
                  "", HFILL }},

            { &hf_q931_message_type,
              { "Message type", "q931.message_type", FT_UINT8, BASE_HEX, VALS(q931_message_type_vals), 0x0,
                  "", HFILL }},

            { &hf_q931_segment_type,
              { "Segmented message type", "q931.segment_type", FT_UINT8, BASE_HEX, VALS(q931_message_type_vals), 0x0,
                  "", HFILL }},

            { &hf_q931_coding_standard,
              { "Coding standard", "q931.coding_standard", FT_UINT8, BASE_HEX,
                   VALS(q931_coding_standard_vals), 0x60,"", HFILL }},

            { &hf_q931_information_transfer_capability,
              { "Information transfer capability", "q931.information_transfer_capability", FT_UINT8, BASE_HEX,
                   VALS(q931_information_transfer_capability_vals), 0x1f,"", HFILL }},

            { &hf_q931_transfer_mode,
              { "Transfer mode", "q931.transfer_mode", FT_UINT8, BASE_HEX,
                   VALS(q931_transfer_mode_vals), 0x60,"", HFILL }},

            { &hf_q931_information_transfer_rate,
              { "Information transfer rate", "q931.information_transfer_rate", FT_UINT8, BASE_HEX,
                   VALS(q931_information_transfer_rate_vals), 0x1f,"", HFILL }},

            { &hf_q931_uil1,
              { "User information layer 1 protocol", "q931.uil1", FT_UINT8, BASE_HEX,
                   VALS(q931_uil1_vals), 0x1f,"", HFILL }},

            { &hf_q931_cause_location,
              { "Cause location", "q931.cause_location", FT_UINT8, BASE_DEC, VALS(q931_cause_location_vals), 0x0f,
                  "", HFILL }},

            { &hf_q931_cause_value,
              { "Cause value", "q931.cause_value", FT_UINT8, BASE_DEC, VALS(q931_cause_code_vals), 0x7f,
                  "", HFILL }},

            { &hf_q931_number_type,
              { "Number type", "q931.number_type", FT_UINT8, BASE_HEX, VALS(q931_number_type_vals), 0x70,
                  "", HFILL }},

            { &hf_q931_numbering_plan,
              { "Numbering plan", "q931.numbering_plan", FT_UINT8, BASE_HEX, VALS(q931_numbering_plan_vals), 0x0f,
                  "", HFILL }},

            { &hf_q931_screening_ind,
              { "Screening indicator", "q931.screening_ind", FT_UINT8, BASE_HEX, VALS(q931_screening_indicator_vals), 0x03,
                  "", HFILL }},

            { &hf_q931_presentation_ind,
              { "Presentation indicator", "q931.presentation_ind", FT_UINT8, BASE_HEX, VALS(q931_presentation_indicator_vals), 0x60,
                  "", HFILL }},

            { &hf_q931_extension_ind,
              { "Extension indicator",  "q931.extension_ind",
                  FT_BOOLEAN, 8, TFS(&q931_extension_ind_value), 0x80,
                  "", HFILL }},

            { &hf_q931_calling_party_number,
              { "Calling party number digits", "q931.calling_party_number.digits", FT_STRING, BASE_NONE, NULL, 0x0,
                  "", HFILL }},

            { &hf_q931_called_party_number,
              { "Called party number digits", "q931.called_party_number.digits", FT_STRING, BASE_NONE, NULL, 0x0,
                  "", HFILL }},

            { &hf_q931_connected_number,
              { "Connected party number digits", "q931.connected_number.digits", FT_STRING, BASE_NONE, NULL, 0x0,
                  "", HFILL }},

            { &hf_q931_redirecting_number,
              { "Redirecting party number digits", "q931.redirecting_number.digits", FT_STRING, BASE_NONE, NULL, 0x0,
                  "", HFILL }},

    /* fields for channel identification IE */
            /* 0x80 is the extension bit */

            { &hf_q931_channel_interface_explicit,
              { "Interface identifier present", "q931.channel.interface_id_present", FT_BOOLEAN, 8, NULL, 0x40,
                "True if the interface identifier is explicit in the following octets", HFILL }},

            { &hf_q931_channel_interface_type,
              { "Interface type", "q931.channel.interface_type", FT_BOOLEAN, 8, &tfs_interface_type, 0x20,
                "Identifies the ISDN interface type", HFILL }},

            /* 0x10 is spare */
                
            { &hf_q931_channel_exclusive,
              { "Indicated channel is exclusive", "q931.channel.exclusive", FT_BOOLEAN, 8, &tfs_channel_exclusive, 0x08,
                "True if only the indicated channel is acceptable", HFILL }},

            { &hf_q931_channel_dchan,
              { "D-channel indicator", "q931.channel.dchan", FT_BOOLEAN, 8, NULL, 0x04,
                "True if the identified channel is the D-Channel", HFILL }},

            { &hf_q931_channel_selection_bri,
              { "Information channel selection", "q931.channel.selection", FT_UINT8, BASE_HEX, q931_basic_channel_selection_vals, 0x03,
                "Identifies the information channel to be used", HFILL }},

            { &hf_q931_channel_selection_pri,
              { "Information channel selection", "q931.channel.selection", FT_UINT8, BASE_HEX, q931_not_basic_channel_selection_vals, 0x03,
                "Identifies the information channel to be used", HFILL }},

            { &hf_q931_channel_map,
              { "Number/map", "q931.channel.map", FT_BOOLEAN, 8, &tfs_channel_map, 0x10,
                "True if channel is indicates by channel map rather than number", HFILL }},
                
            { &hf_q931_channel_element_type,
              { "Element type", "q931.channel.element_type", FT_UINT8, BASE_HEX, q931_element_type_vals, 0xF,
                "Type of element in the channel number/slot map octets", HFILL }},

            { &hf_q931_channel_number,
              { "Channel number", "q931.channel.number", FT_UINT8, BASE_DEC, NULL, 0x7F,
                "Channel number", HFILL }},
               
    /* desegmentation fields */
            { &hf_q931_segment_overlap,
              { "Segment overlap", "q931.segment.overlap", FT_BOOLEAN, BASE_NONE, NULL, 0x0,
                  "Fragment overlaps with other fragments", HFILL }},

            { &hf_q931_segment_overlap_conflict,
              { "Conflicting data in fragment overlap", "q931.segment.overlap.conflict", FT_BOOLEAN, BASE_NONE, NULL, 0x0,
                  "Overlapping fragments contained conflicting data", HFILL }},

            { &hf_q931_segment_multiple_tails,
              { "Multiple tail fragments found", "q931.segment.multipletails", FT_BOOLEAN, BASE_NONE, NULL, 0x0,
                  "Several tails were found when defragmenting the packet", HFILL }},

            { &hf_q931_segment_too_long_segment,
              { "Segment too long", "q931.segment.toolongfragment", FT_BOOLEAN, BASE_NONE, NULL, 0x0,
                  "Segment contained data past end of packet", HFILL }},

            { &hf_q931_segment_error,
              { "Defragmentation error", "q931.segment.error", FT_FRAMENUM, BASE_NONE, NULL, 0x0,
                  "Defragmentation error due to illegal fragments", HFILL }},

            { &hf_q931_segment,
              { "Q.931 Segment", "q931.segment", FT_FRAMENUM, BASE_NONE, NULL, 0x0,
                  "Q.931 Segment", HFILL }},

            { &hf_q931_segments,
              { "Q.931 Segments", "q931.segments", FT_NONE, BASE_NONE, NULL, 0x0,
                  "Q.931 Segments", HFILL }},

            { &hf_q931_reassembled_in,
              { "Reassembled Q.931 in frame", "q931.reassembled_in", FT_FRAMENUM, BASE_NONE, NULL, 0x0,
                  "This Q.931 message is reassembled in this frame", HFILL}}, 
      };
      static gint *ett[] = {
            &ett_q931,
            &ett_q931_ie,
            &ett_q931_segments,
            &ett_q931_segment,
      };
      module_t *q931_module;

      proto_q931 = proto_register_protocol("Q.931", "Q.931", "q931");
      proto_register_field_array (proto_q931, hf, array_length(hf));
      proto_register_subtree_array(ett, array_length(ett));
      register_init_routine(q931_init);

      register_dissector("q931", dissect_q931, proto_q931);
      register_dissector("q931.tpkt", dissect_q931_tpkt, proto_q931);
      q931_tpkt_handle = find_dissector("q931.tpkt");
      q931_tpkt_pdu_handle = create_dissector_handle(dissect_q931_tpkt_pdu,
          proto_q931);
      register_dissector("q931.ie", dissect_q931_ie_cs0, proto_q931);
      register_dissector("q931.ie.cs7", dissect_q931_ie_cs7, proto_q931);

      /* subdissector code */ 
      codeset_dissector_table = register_dissector_table("q931.codeset", "Q.931 Codeset", FT_UINT8, BASE_HEX);
      ie_dissector_table = register_dissector_table("q931.ie", "Q.931 IE", FT_UINT16, BASE_HEX);

      q931_module = prefs_register_protocol(proto_q931, NULL);
      prefs_register_bool_preference(q931_module, "desegment_h323_messages",
          "Reassemble Q.931 messages spanning multiple TCP segments",
          "Whether the Q.931 dissector should reassemble messages spanning multiple TCP segments."
          " To use this option, you must also enable \"Allow subdissectors to reassemble TCP streams\" in the TCP protocol settings.",
          &q931_desegment);
      prefs_register_bool_preference(q931_module, "reassembly",
          "Reassemble segmented Q.931 messages",
          "Reassemble segmented Q.931 messages (Q.931 - Annex H)",
          &q931_reassembly);
       /* Register for tapping */
       q931_tap = register_tap("q931");
}

void
proto_reg_handoff_q931(void)
{
      dissector_handle_t q931_handle;

      q931_handle = find_dissector("q931");
      dissector_add("lapd.sapi", LAPD_SAPI_Q931, q931_handle);

      /*
       * Attempt to get a handle for the H.225 dissector.
       * If we can't, the handle we get is null, and we'll just
       * dissect putatively-H.255 Call Signaling stuff as User
       * Information.
       */
      h225_handle = find_dissector("h225");

      /*
       * For H.323.
       */
      heur_dissector_add("tcp", dissect_q931_tpkt_heur, proto_q931);
}

static void reset_q931_packet_info(q931_packet_info *pi)
{
    if(pi == NULL) {
        return;
    }

    pi->calling_number = NULL;
    pi->called_number = NULL;
    pi->cause_value = 0xFF;
    pi->crv = -1;
}

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