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ringbuffer.c
/* ringbuffer.c
 * Routines for packet capture windows
 *
 * $Id: ringbuffer.c 28155 2009-04-26 15:51:25Z tuexen $
 *
 * Wireshark - Network traffic analyzer
 * By Gerald Combs <gerald@wireshark.org>
 * Copyright 1998 Gerald Combs
 *
 * 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.
 */

/*
 * <laurent.deniel@free.fr>
 *
 * Almost completely rewritten in order to:
 *
 * - be able to use a unlimited number of ringbuffer files
 * - close the current file and open (truncating) the next file at switch
 * - set the final file name once open (or reopen)
 * - avoid the deletion of files that could not be truncated (can't arise now)
 *   and do not erase empty files
 *
 * The idea behind that is to remove the limitation of the maximum # of
 * ringbuffer files being less than the maximum # of open fd per process
 * and to be able to reduce the amount of virtual memory usage (having only
 * one file open at most) or the amount of file system usage (by truncating
 * the files at switch and not the capture stop, and by closing them which
 * makes possible their move or deletion after a switch).
 *
 */

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

#ifdef HAVE_LIBPCAP

#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#endif

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#include <stdio.h>
#include <string.h>
#include <time.h>
#include <errno.h>

#include <pcap.h>

#include <glib.h>

#include "pcapio.h"
#include "ringbuffer.h"
#include <wsutil/file_util.h>


/* Ringbuffer file structure */
typedef struct _rb_file {
  gchar           *name;
} rb_file;

/* Ringbuffer data structure */
typedef struct _ringbuf_data {
  rb_file      *files;
  guint         num_files;           /* Number of ringbuffer files (1 to ...) */
  guint         curr_file_num;       /* Number of the current file (ever increasing) */
  gchar        *fprefix;             /* Filename prefix */
  gchar        *fsuffix;             /* Filename suffix */
  gboolean      unlimited;           /* TRUE if unlimited number of files */

  int           fd;                /* Current ringbuffer file descriptor */
  FILE         *pdh;
} ringbuf_data;

static ringbuf_data rb_data;


/*
 * create the next filename and open a new binary file with that name
 */
static int ringbuf_open_file(rb_file *rfile, int *err)
{
  char    filenum[5+1];
  char    timestr[14+1];
  time_t  current_time;

  if (rfile->name != NULL) {
    if (rb_data.unlimited == FALSE) {
      /* remove old file (if any, so ignore error) */
      ws_unlink(rfile->name);
    }
    g_free(rfile->name);
  }

#ifdef _WIN32
  _tzset();
#endif
  current_time = time(NULL);

  g_snprintf(filenum, sizeof(filenum), "%05u", (rb_data.curr_file_num + 1) % 100000);
  strftime(timestr, sizeof(timestr), "%Y%m%d%H%M%S", localtime(&current_time));
  rfile->name = g_strconcat(rb_data.fprefix, "_", filenum, "_", timestr,
                      rb_data.fsuffix, NULL);

  if (rfile->name == NULL) {
    *err = ENOMEM;
    return -1;
  }

  rb_data.fd = ws_open(rfile->name, O_RDWR|O_BINARY|O_TRUNC|O_CREAT, 0600);

  if (rb_data.fd == -1 && err != NULL) {
    *err = errno;
  }

  return rb_data.fd;
}

/*
 * Initialize the ringbuffer data structures
 */
int
ringbuf_init(const char *capfile_name, guint num_files)
{
  unsigned int i;
  char        *pfx, *last_pathsep;
  gchar       *save_file;

  rb_data.files = NULL;
  rb_data.curr_file_num = 0;
  rb_data.fprefix = NULL;
  rb_data.fsuffix = NULL;
  rb_data.unlimited = FALSE;
  rb_data.fd = -1;
  rb_data.pdh = NULL;

  /* just to be sure ... */
  if (num_files <= RINGBUFFER_MAX_NUM_FILES) {
    rb_data.num_files = num_files;
  } else {
    rb_data.num_files = RINGBUFFER_MAX_NUM_FILES;
  }

  /* Check file name */
  if (capfile_name == NULL) {
    /* ringbuffer does not work with temporary files! */
    return -1;
  }

  /* set file name prefix/suffix */

  save_file = g_strdup(capfile_name);
  last_pathsep = strrchr(save_file, G_DIR_SEPARATOR);
  pfx = strrchr(save_file,'.');
  if (pfx != NULL && (last_pathsep == NULL || pfx > last_pathsep)) {
    /* The pathname has a "." in it, and it's in the last component
       of the pathname (because there is either only one component,
       i.e. last_pathsep is null as there are no path separators,
       or the "." is after the path separator before the last
       component.

       Treat it as a separator between the rest of the file name and
       the file name suffix, and arrange that the names given to the
       ring buffer files have the specified suffix, i.e. put the
       changing part of the name *before* the suffix. */
    pfx[0] = '\0';
    rb_data.fprefix = g_strdup(save_file);
    pfx[0] = '.'; /* restore capfile_name */
    rb_data.fsuffix = g_strdup(pfx);
  } else {
    /* Either there's no "." in the pathname, or it's in a directory
       component, so the last component has no suffix. */
    rb_data.fprefix = g_strdup(save_file);
    rb_data.fsuffix = NULL;
  }
  g_free(save_file);
  save_file = NULL;

  /* allocate rb_file structures (only one if unlimited since there is no
     need to save all file names in that case) */

  if (num_files == RINGBUFFER_UNLIMITED_FILES) {
    rb_data.unlimited = TRUE;
    rb_data.num_files = 1;
  }

  rb_data.files = g_malloc(rb_data.num_files * sizeof(rb_file));
  if (rb_data.files == NULL) {
    return -1;
  }

  for (i=0; i < rb_data.num_files; i++) {
    rb_data.files[i].name = NULL;
  }

  /* create the first file */
  if (ringbuf_open_file(&rb_data.files[0], NULL) == -1) {
    ringbuf_error_cleanup();
    return -1;
  }

  return rb_data.fd;
}


const gchar *ringbuf_current_filename(void)
{
  return rb_data.files[rb_data.curr_file_num % rb_data.num_files].name;
}

/*
 * Calls libpcap_fdopen() for the current ringbuffer file
 */
FILE *
ringbuf_init_libpcap_fdopen(int *err)
{
  rb_data.pdh = libpcap_fdopen(rb_data.fd, err);
  return rb_data.pdh;
}

/*
 * Switches to the next ringbuffer file
 */
gboolean
ringbuf_switch_file(FILE **pdh, gchar **save_file, int *save_file_fd, int *err)
{
  int     next_file_index;
  rb_file *next_rfile = NULL;

  /* close current file */

  if (!libpcap_dump_close(rb_data.pdh, err)) {
    ws_close(rb_data.fd);     /* XXX - the above should have closed this already */
    rb_data.pdh = NULL; /* it's still closed, we just got an error while closing */
    rb_data.fd = -1;
    return FALSE;
  }

  rb_data.pdh = NULL;
  rb_data.fd  = -1;

  /* get the next file number and open it */

  rb_data.curr_file_num++ /* = next_file_num*/;
  next_file_index = (rb_data.curr_file_num) % rb_data.num_files;
  next_rfile = &rb_data.files[next_file_index];

  if (ringbuf_open_file(next_rfile, err) == -1) {
    return FALSE;
  }

  if (ringbuf_init_libpcap_fdopen(err) == NULL) {
    return FALSE;
  }

  /* switch to the new file */
  *save_file = next_rfile->name;
  *save_file_fd = rb_data.fd;
  (*pdh) = rb_data.pdh;

  return TRUE;
}

/*
 * Calls libpcap_dump_close() for the current ringbuffer file
 */
gboolean
ringbuf_libpcap_dump_close(gchar **save_file, int *err)
{
  gboolean  ret_val = TRUE;

  /* close current file, if it's open */
  if (rb_data.pdh != NULL) {
    if (!libpcap_dump_close(rb_data.pdh, err)) {
      ws_close(rb_data.fd);
      ret_val = FALSE;
    }

    rb_data.pdh = NULL;
    rb_data.fd  = -1;
  }

  /* set the save file name to the current file */
  *save_file = rb_data.files[rb_data.curr_file_num % rb_data.num_files].name;
  return ret_val;
}

/*
 * Frees all memory allocated by the ringbuffer
 */
void
ringbuf_free()
{
  unsigned int i;

  if (rb_data.files != NULL) {
    for (i=0; i < rb_data.num_files; i++) {
      if (rb_data.files[i].name != NULL) {
      g_free(rb_data.files[i].name);
      rb_data.files[i].name = NULL;
      }
    }
    g_free(rb_data.files);
    rb_data.files = NULL;
  }
  if (rb_data.fprefix != NULL) {
    g_free(rb_data.fprefix);
    rb_data.fprefix = NULL;
  }
  if (rb_data.fsuffix != NULL) {
    g_free(rb_data.fsuffix);
    rb_data.fsuffix = NULL;
  }
}

/*
 * Frees all memory allocated by the ringbuffer
 */
void
ringbuf_error_cleanup(void)
{
  unsigned int i;

  /* try to close via wtap */
  if (rb_data.pdh != NULL) {
    if (libpcap_dump_close(rb_data.pdh, NULL)) {
      rb_data.fd = -1;
    }
    rb_data.pdh = NULL;
  }

  /* close directly if still open */
  /* XXX - it shouldn't still be open; "libpcap_dump_close()" should leave the
     file closed even if it fails */
  if (rb_data.fd != -1) {
    ws_close(rb_data.fd);
    rb_data.fd = -1;
  }

  if (rb_data.files != NULL) {
    for (i=0; i < rb_data.num_files; i++) {
      if (rb_data.files[i].name != NULL) {
        ws_unlink(rb_data.files[i].name);
      }
    }
  }
  /* free the memory */
  ringbuf_free();
}

#endif /* HAVE_LIBPCAP */

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