frame_tvbuff.c

/* frame_tvbuff.c
 * Implements a tvbuff for frame
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include "config.h"

#include <glib.h>

#include <epan/packet.h>
#include <epan/tvbuff-int.h>
#include <epan/tvbuff.h>

#include "frame_tvbuff.h"
#include "globals.h"

#include "wtap-int.h" /* for ->random_fh */

struct tvb_frame {
	struct tvbuff tvb;

	Buffer *buf;         /* Packet data */

	wtap *wth;           /**< Wiretap session */
	gint64 file_off;     /**< File offset */

	guint offset;
};

static gboolean
frame_read(struct tvb_frame *frame_tvb, struct wtap_pkthdr *phdr, Buffer *buf)
{
	int    err;
	gchar *err_info;

	/* sanity check, capture file was closed? */
	if (cfile.wth != frame_tvb->wth)
		return FALSE;

	/* XXX, what if phdr->caplen isn't equal to
	 * frame_tvb->tvb.length + frame_tvb->offset?
	 */
	if (!wtap_seek_read(frame_tvb->wth, frame_tvb->file_off, phdr, buf, &err, &err_info)) {
		switch (err) {
			case WTAP_ERR_UNSUPPORTED_ENCAP:
			case WTAP_ERR_BAD_FILE:
				g_free(err_info);
				break;
		}
		return FALSE;
	}
	return TRUE;
}

static void
frame_cache(struct tvb_frame *frame_tvb)
{
	struct wtap_pkthdr phdr; /* Packet header */

	memset(&phdr, 0, sizeof(struct wtap_pkthdr));

	if (frame_tvb->buf == NULL) {
		frame_tvb->buf = (struct Buffer *) g_malloc(sizeof(struct Buffer));

		/* XXX, register frame_tvb to some list which frees from time to time not used buffers :] */
		buffer_init(frame_tvb->buf, frame_tvb->tvb.length + frame_tvb->offset);

		if (!frame_read(frame_tvb, &phdr, frame_tvb->buf))
			{ /* TODO: THROW(???); */ }
	}

	frame_tvb->tvb.real_data = buffer_start_ptr(frame_tvb->buf) + frame_tvb->offset;
}

static void
frame_free(tvbuff_t *tvb)
{
	struct tvb_frame *frame_tvb = (struct tvb_frame *) tvb;

	if (frame_tvb->buf) {
		buffer_free(frame_tvb->buf);

		g_free(frame_tvb->buf);
	}
}

static const guint8 *
frame_get_ptr(tvbuff_t *tvb, guint abs_offset, guint abs_length _U_)
{
	struct tvb_frame *frame_tvb = (struct tvb_frame *) tvb;

	frame_cache(frame_tvb);

	return tvb->real_data + abs_offset;
}

static void *
frame_memcpy(tvbuff_t *tvb, void *target, guint abs_offset, guint abs_length)
{
	struct tvb_frame *frame_tvb = (struct tvb_frame *) tvb;

	frame_cache(frame_tvb);

	return memcpy(target, tvb->real_data + abs_offset, abs_length);
}

static gint
frame_find_guint8(tvbuff_t *tvb, guint abs_offset, guint limit, guint8 needle)
{
	struct tvb_frame *frame_tvb = (struct tvb_frame *) tvb;
	const guint8 *result;

	frame_cache(frame_tvb);

	result = (const guint8 *)memchr(tvb->real_data + abs_offset, needle, limit);
	if (result)
		return (gint) (result - tvb->real_data);
	else
		return -1;
}

static gint
frame_pbrk_guint8(tvbuff_t *tvb, guint abs_offset, guint limit, const guint8 *needles, guchar *found_needle)
{
	struct tvb_frame *frame_tvb = (struct tvb_frame *) tvb;

	frame_cache(frame_tvb);

	return tvb_pbrk_guint8(tvb, abs_offset, limit, needles, found_needle);
}

static guint
frame_offset(const tvbuff_t *tvb _U_, const guint counter)
{
	/* XXX: frame_tvb->offset */
	return counter;
}

static tvbuff_t *frame_clone(tvbuff_t *tvb, guint abs_offset, guint abs_length);

static const struct tvb_ops tvb_frame_ops = {
	sizeof(struct tvb_frame), /* size */

	frame_free,           /* free */
	frame_offset,         /* offset */
	frame_get_ptr,        /* get_ptr */
	frame_memcpy,         /* memcpy */
	frame_find_guint8,    /* find_guint8 */
	frame_pbrk_guint8,    /* pbrk_guint8 */
	frame_clone,          /* clone */
};

/* based on tvb_new_real_data() */
tvbuff_t *
frame_tvbuff_new(const frame_data *fd, const guint8 *buf)
{
	struct tvb_frame *frame_tvb;
	tvbuff_t *tvb;

	tvb = tvb_new(&tvb_frame_ops);

	/*
	 * XXX - currently, the length arguments in
	 * tvbuff structure are signed, but the captured
	 * and reported length values are unsigned; this means
	 * that length values > 2^31 - 1 will appear as
	 * negative lengths
	 *
	 * Captured length values that large will already
	 * have been filtered out by the Wiretap modules
	 * (the file will be reported as corrupted), to
	 * avoid trying to allocate large chunks of data.
	 *
	 * Reported length values will not have been
	 * filtered out, and should not be filtered out,
	 * as those lengths are not necessarily invalid.
	 *
	 * For now, we clip the reported length at G_MAXINT
	 *
	 * (XXX, is this still a problem?) There was an exception when we call
	 * tvb_new_real_data() now there's no one
	 */

	tvb->real_data       = buf;
	tvb->length          = fd->cap_len;
	tvb->reported_length = fd->pkt_len > G_MAXINT ? G_MAXINT : fd->pkt_len;
	tvb->initialized     = TRUE;

	/*
	 * This is the top-level real tvbuff for this data source,
	 * so its data source tvbuff is itself.
	 */
	tvb->ds_tvb = tvb;

	frame_tvb = (struct tvb_frame *) tvb;

	/* XXX, wtap_can_seek() */
	if (cfile.wth && cfile.wth->random_fh
#ifdef WANT_PACKET_EDITOR
		&& fd->file_off != -1 /* generic clone for modified packets */
#endif
	) {
		frame_tvb->wth = cfile.wth;
		frame_tvb->file_off = fd->file_off;
		frame_tvb->offset = 0;
	} else
		frame_tvb->wth = NULL;

	frame_tvb->buf = NULL;

	return tvb;
}

tvbuff_t *
frame_tvbuff_new_buffer(const frame_data *fd, Buffer *buf)
{
	return frame_tvbuff_new(fd, buffer_start_ptr(buf));
}

static tvbuff_t *
frame_clone(tvbuff_t *tvb, guint abs_offset, guint abs_length)
{
	struct tvb_frame *frame_tvb = (struct tvb_frame *) tvb;

	tvbuff_t *cloned_tvb;
	struct tvb_frame *cloned_frame_tvb;

	/* file not seekable */
	if (!frame_tvb->wth)
		return NULL;

	abs_offset += frame_tvb->offset;

	cloned_tvb = tvb_new(&tvb_frame_ops);

	/* data will be read when needed */
	cloned_tvb->real_data       = NULL;
	cloned_tvb->length          = abs_length;
	cloned_tvb->reported_length = abs_length; /* XXX? */
	cloned_tvb->initialized     = TRUE;

	/*
	 * This is the top-level real tvbuff for this data source,
	 * so its data source tvbuff is itself.
	 */
	cloned_tvb->ds_tvb = cloned_tvb;

	cloned_frame_tvb = (struct tvb_frame *) cloned_tvb;
	cloned_frame_tvb->wth = frame_tvb->wth;
	cloned_frame_tvb->file_off = frame_tvb->file_off;
	cloned_frame_tvb->offset = abs_offset;
	cloned_frame_tvb->buf = NULL;

	return cloned_tvb;
}


/* based on tvb_new_real_data() */
tvbuff_t *
file_tvbuff_new(const frame_data *fd, const guint8 *buf)
{
	struct tvb_frame *frame_tvb;
	tvbuff_t *tvb;

	tvb = tvb_new(&tvb_frame_ops);

	/*
	 * XXX - currently, the length arguments in
	 * tvbuff structure are signed, but the captured
	 * and reported length values are unsigned; this means
	 * that length values > 2^31 - 1 will appear as
	 * negative lengths
	 *
	 * Captured length values that large will already
	 * have been filtered out by the Wiretap modules
	 * (the file will be reported as corrupted), to
	 * avoid trying to allocate large chunks of data.
	 *
	 * Reported length values will not have been
	 * filtered out, and should not be filtered out,
	 * as those lengths are not necessarily invalid.
	 *
	 * For now, we clip the reported length at G_MAXINT
	 *
	 * (XXX, is this still a problem?) There was an exception when we call
	 * tvb_new_real_data() now there's no one
	 */

	tvb->real_data       = buf;
	tvb->length          = fd->cap_len;
	tvb->reported_length = fd->pkt_len > G_MAXINT ? G_MAXINT : fd->pkt_len;
	tvb->initialized     = TRUE;

	/*
	 * This is the top-level real tvbuff for this data source,
	 * so its data source tvbuff is itself.
	 */
	tvb->ds_tvb = tvb;

	frame_tvb = (struct tvb_frame *) tvb;

	/* XXX, wtap_can_seek() */
	if (cfile.wth && cfile.wth->random_fh
#ifdef WANT_PACKET_EDITOR
		&& fd->file_off != -1 /* generic clone for modified packets */
#endif
	) {
		frame_tvb->wth = cfile.wth;
		frame_tvb->file_off = fd->file_off;
		frame_tvb->offset = 0;
	} else
		frame_tvb->wth = NULL;

	frame_tvb->buf = NULL;

	return tvb;
}

tvbuff_t *
file_tvbuff_new_buffer(const frame_data *fd, Buffer *buf)
{
	return frame_tvbuff_new(fd, buffer_start_ptr(buf));
}