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
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 */

// #include <config.h>

#include <glib.h>

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

#include "frame_tvbuff.h"

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

struct tvb_frame {
	struct tvbuff tvb;

	Buffer *buf;         /* Packet data */

	const struct packet_provider_data *prov;	/* provider of packet information */
	gint64 file_off;     /**< File offset */

	guint offset;
};

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

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

static GPtrArray *buffer_cache = NULL;

static void
frame_cache(struct tvb_frame *frame_tvb)
{
	wtap_rec rec; /* Record metadata */

	wtap_rec_init(&rec);

	if (frame_tvb->buf == NULL) {
		if (G_UNLIKELY(!buffer_cache)) buffer_cache = g_ptr_array_sized_new(1024);

		if (buffer_cache->len > 0) {
			frame_tvb->buf = (struct Buffer *) g_ptr_array_remove_index(buffer_cache, buffer_cache->len - 1);
		} else {
			frame_tvb->buf = (struct Buffer *) g_malloc(sizeof(struct Buffer));
		}

		ws_buffer_init(frame_tvb->buf, frame_tvb->tvb.length + frame_tvb->offset);

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

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

	wtap_rec_cleanup(&rec);
}

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

	if (frame_tvb->buf) {
		ws_buffer_free(frame_tvb->buf);
		g_ptr_array_add(buffer_cache, 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 ws_mempbrk_pattern* pattern, guchar *found_needle)
{
	struct tvb_frame *frame_tvb = (struct tvb_frame *) tvb;

	frame_cache(frame_tvb);

	return tvb_ws_mempbrk_pattern_guint8(tvb, abs_offset, limit, pattern, 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 struct packet_provider_data *prov, 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->contained_length = tvb->reported_length;
	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 (prov->wth && prov->wth->random_fh) {
		frame_tvb->prov = prov;
		frame_tvb->file_off = fd->file_off;
		frame_tvb->offset = 0;
	} else
		frame_tvb->prov = NULL;

	frame_tvb->buf = NULL;

	return tvb;
}

tvbuff_t *
frame_tvbuff_new_buffer(const struct packet_provider_data *prov,
    const frame_data *fd, Buffer *buf)
{
	return frame_tvbuff_new(prov, fd, ws_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->prov)
		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->contained_length = cloned_tvb->reported_length;
	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->prov = frame_tvb->prov;
	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 struct packet_provider_data *prov, 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->contained_length = tvb->reported_length;
	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 (prov->wth && prov->wth->random_fh) {
		frame_tvb->prov = prov;
		frame_tvb->file_off = fd->file_off;
		frame_tvb->offset = 0;
	} else
		frame_tvb->prov = NULL;

	frame_tvb->buf = NULL;

	return tvb;
}

tvbuff_t *
file_tvbuff_new_buffer(const struct packet_provider_data *prov,
    const frame_data *fd, Buffer *buf)
{
	return frame_tvbuff_new(prov, fd, ws_buffer_start_ptr(buf));
}

/*
 * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 *
 * Local variables:
 * c-basic-offset: 8
 * tab-width: 8
 * indent-tabs-mode: t
 * End:
 *
 * vi: set shiftwidth=8 tabstop=8 noexpandtab:
 * :indentSize=8:tabSize=8:noTabs=false:
 */