xref: /external/tcpdump/netdissect.c

/*
 * Copyright (c) 1988-1997
 *	The Regents of the University of California.  All rights reserved.
 *
 * Copyright (c) 1998-2012  Michael Richardson <mcr@tcpdump.org>
 *      The TCPDUMP project
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that: (1) source code distributions
 * retain the above copyright notice and this paragraph in its entirety, (2)
 * distributions including binary code include the above copyright notice and
 * this paragraph in its entirety in the documentation or other materials
 * provided with the distribution, and (3) all advertising materials mentioning
 * features or use of this software display the following acknowledgement:
 * ``This product includes software developed by the University of California,
 * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
 * the University nor the names of its contributors may be used to endorse
 * or promote products derived from this software without specific prior
 * written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include "netdissect-stdinc.h"
#include "netdissect.h"
#include <string.h>
#include <stdio.h>
#include <stdlib.h>

#ifdef USE_LIBSMI
#include <smi.h>
#endif

/*
 * Initialize anything that must be initialized before dissecting
 * packets.
 *
 * This should be called at the beginning of the program; it does
 * not need to be called, and should not be called, for every
 * netdissect_options structure.
 */
int
nd_init(char *errbuf, size_t errbuf_size)
{
#ifdef _WIN32
	WORD wVersionRequested;
	WSADATA wsaData;
	int err;

	/*
	 * Request Winsock 2.2; we expect Winsock 2.
	 */
	wVersionRequested = MAKEWORD(2, 2);
	err = WSAStartup(wVersionRequested, &wsaData);
	if (err != 0) {
		strlcpy(errbuf, "Attempting to initialize Winsock failed",
		    errbuf_size);
		return (-1);
	}
#endif /* _WIN32 */

#ifdef USE_LIBSMI
	/*
	 * XXX - should we just fail if this fails?  Some of the
	 * libsmi calls may fail.
	 */
	smiInit("tcpdump");
#endif

	/*
	 * Clears the error buffer, and uses it so we don't get
	 * "unused argument" warnings at compile time.
	 */
	strlcpy(errbuf, "", errbuf_size);
	return (0);
}

/*
 * Clean up anything that ndo_init() did.
 */
void
nd_cleanup(void)
{
#ifdef USE_LIBSMI
	/*
	 * This appears, in libsmi 0.4.8, to do nothing if smiInit()
	 * wasn't done or failed, so we call it unconditionally.
	 */
	smiExit();
#endif

#ifdef _WIN32
	/*
	 * Undo the WSAStartup() call above.
	 */
	WSACleanup();
#endif
}

int
nd_have_smi_support(void)
{
#ifdef USE_LIBSMI
	return (1);
#else
	return (0);
#endif
}

/*
 * Indicates whether an SMI module has been loaded, so that we can use
 * libsmi to translate OIDs.
 */
int nd_smi_module_loaded;

int
nd_load_smi_module(const char *module, char *errbuf, size_t errbuf_size)
{
#ifdef USE_LIBSMI
	if (smiLoadModule(module) == 0) {
		snprintf(errbuf, errbuf_size, "could not load MIB module %s",
		    module);
		return (-1);
	}
	nd_smi_module_loaded = 1;
	return (0);
#else
	snprintf(errbuf, errbuf_size, "MIB module %s not loaded: no libsmi support",
	    module);
	return (-1);
#endif
}

const char *
nd_smi_version_string(void)
{
#ifdef USE_LIBSMI
	return (smi_version_string);
#else
	return (NULL);
#endif
}


int
nd_push_buffer(netdissect_options *ndo, u_char *new_buffer,
	       const u_char *new_packetp, const u_int newlen)
{
	struct netdissect_saved_packet_info *ndspi;

	ndspi = (struct netdissect_saved_packet_info *)malloc(sizeof(struct netdissect_saved_packet_info));
	if (ndspi == NULL)
		return (0);	/* fail */
	ndspi->ndspi_buffer = new_buffer;
	ndspi->ndspi_packetp = ndo->ndo_packetp;
	ndspi->ndspi_snapend = ndo->ndo_snapend;
	ndspi->ndspi_prev = ndo->ndo_packet_info_stack;

	ndo->ndo_packetp = new_packetp;
	ndo->ndo_snapend = new_packetp + newlen;
	ndo->ndo_packet_info_stack = ndspi;

	return (1);	/* success */
}


/*
 * In a given netdissect_options structure:
 *
 *    push the current packet information onto the packet information
 *    stack;
 *
 *    given a pointer into the packet and a length past that point in
 *    the packet, calculate a new snapshot end that's at the lower
 *    of the current snapshot end and that point in the packet;
 *
 *    set the snapshot end to that new value.
 */
int
nd_push_snaplen(netdissect_options *ndo, const u_char *bp, const u_int newlen)
{
	struct netdissect_saved_packet_info *ndspi;
	u_int snaplen_remaining;

	ndspi = (struct netdissect_saved_packet_info *)malloc(sizeof(struct netdissect_saved_packet_info));
	if (ndspi == NULL)
		return (0);	/* fail */
	ndspi->ndspi_buffer = NULL;	/* no new buffer */
	ndspi->ndspi_packetp = ndo->ndo_packetp;
	ndspi->ndspi_snapend = ndo->ndo_snapend;
	ndspi->ndspi_prev = ndo->ndo_packet_info_stack;

	/*
	 * Push the saved previous data onto the stack.
	 */
	ndo->ndo_packet_info_stack = ndspi;

	/*
	 * Find out how many bytes remain after the current snapend.
	 *
	 * We're restricted to packets with at most UINT_MAX bytes;
	 * cast the result to u_int, so that we don't get truncation
	 * warnings on LP64 and LLP64 platforms.  (ptrdiff_t is
	 * signed and we want an unsigned difference; the pointer
	 * should at most be equal to snapend, and must *never*
	 * be past snapend.)
	 */
	snaplen_remaining = (u_int)(ndo->ndo_snapend - bp);

	/*
	 * If the new snapend is smaller than the one calculated
	 * above, set the snapend to that value, otherwise leave
	 * it unchanged.
	 */
	if (newlen <= snaplen_remaining) {
		/* Snapend isn't past the previous snapend */
		ndo->ndo_snapend = bp + newlen;
	}

	return (1);	/* success */
}

/*
 * In a given netdissect_options structure:
 *
 *    given a pointer into the packet and a length past that point in
 *    the packet, calculate a new snapshot end that's at the lower
 *    of the previous snapshot end - or, if there is no previous
 *    snapshot end, the current snapshot end - and that point in the
 *    packet;
 *
 *    set the snapshot end to that new value.
 *
 * This is to change the current snapshot end.  This may increase the
 * snapshot end, as it may be used, for example, for a Jumbo Payload
 * option in IPv6.  It must not increase it past the snapshot length
 * atop which the current one was pushed, however.
 */
void
nd_change_snaplen(netdissect_options *ndo, const u_char *bp, const u_int newlen)
{
	struct netdissect_saved_packet_info *ndspi;
	const u_char *previous_snapend;
	u_int snaplen_remaining;

	ndspi = ndo->ndo_packet_info_stack;
	if (ndspi->ndspi_prev != NULL)
		previous_snapend = ndspi->ndspi_prev->ndspi_snapend;
	else
		previous_snapend = ndo->ndo_snapend;

	/*
	 * Find out how many bytes remain after the previous
	 * snapend - or, if there is no previous snapend, after
	 * the current snapend.
	 *
	 * We're restricted to packets with at most UINT_MAX bytes;
	 * cast the result to u_int, so that we don't get truncation
	 * warnings on LP64 and LLP64 platforms.  (ptrdiff_t is
	 * signed and we want an unsigned difference; the pointer
	 * should at most be equal to snapend, and must *never*
	 * be past snapend.)
	 */
	snaplen_remaining = (u_int)(previous_snapend - bp);

	/*
	 * If the new snapend is smaller than the one calculated
	 * above, set the snapend to that value, otherwise leave
	 * it unchanged.
	 */
	if (newlen <= snaplen_remaining) {
		/* Snapend isn't past the previous snapend */
		ndo->ndo_snapend = bp + newlen;
	}
}

void
nd_pop_packet_info(netdissect_options *ndo)
{
	struct netdissect_saved_packet_info *ndspi;

	ndspi = ndo->ndo_packet_info_stack;
	ndo->ndo_packetp = ndspi->ndspi_packetp;
	ndo->ndo_snapend = ndspi->ndspi_snapend;
	ndo->ndo_packet_info_stack = ndspi->ndspi_prev;

	free(ndspi->ndspi_buffer);
	free(ndspi);
}

void
nd_pop_all_packet_info(netdissect_options *ndo)
{
	while (ndo->ndo_packet_info_stack != NULL)
		nd_pop_packet_info(ndo);
}