suricata/src/decode-mpls.c

/* Copyright (C) 2014 Open Information Security Foundation
 *
 * You can copy, redistribute or modify this Program under the terms of
 * the GNU General Public License version 2 as published by the Free
 * Software Foundation.
 *
 * 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
 * version 2 along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */

/**
 * \file
 *
 * \author Jason Ish <jason.ish@emulex.com>
 *
 * MPLS decoder.
 */

#include "suricata-common.h"
#include "decode.h"

#define MPLS_HEADER_LEN         4
#define MPLS_PW_LEN             4
#define MPLS_MAX_RESERVED_LABEL 15
#define MPLS_LABEL_IPV4         0
#define MPLS_LABEL_IPV6         2
#define MPLS_LABEL(shim)        ntohl(shim) >> 12
#define MPLS_BOTTOM(shim)       ((ntohl(shim) >> 8) & 0x1)

/* Inner protocol guessing values. */
#define MPLS_PROTO_ETHERNET     0
#define MPLS_PROTO_IPV4         4
#define MPLS_PROTO_IPV6         6

int DecodeMPLS(ThreadVars *tv, DecodeThreadVars *dtv, Packet *p, uint8_t *pkt,
    uint16_t len, PacketQueue *pq)
{
    uint32_t shim;
    int label;

    SCPerfCounterIncr(dtv->counter_mpls, tv->sc_perf_pca);

    do {
        if (len < MPLS_HEADER_LEN) {
            return TM_ECODE_FAILED;
        }
        shim = *(uint32_t *)pkt;
        pkt += MPLS_HEADER_LEN;
        len -= MPLS_HEADER_LEN;
    } while (MPLS_BOTTOM(shim) == 0);

    label = MPLS_LABEL(shim);
    if (label == MPLS_LABEL_IPV4) {
        return DecodeIPV4(tv, dtv, p, pkt, len, pq);
    }
    else if (label == MPLS_LABEL_IPV6) {
        return DecodeIPV6(tv, dtv, p, pkt, len, pq);
    }
    else if (label < MPLS_MAX_RESERVED_LABEL) {
        return TM_ECODE_FAILED;
    }

    /* Best guess at inner packet. */
    switch (pkt[0] >> 4) {
    case MPLS_PROTO_IPV4:
        DecodeIPV4(tv, dtv, p, pkt, len, pq);
        break;
    case MPLS_PROTO_IPV6:
        DecodeIPV6(tv, dtv, p, pkt, len, pq);
        break;
    case MPLS_PROTO_ETHERNET:
        /* Looks like it could be an ethernet pseudowire. */
        DecodeEthernet(tv, dtv, p, pkt + MPLS_PW_LEN, len - MPLS_PW_LEN,
            pq);
        break;
    default:
        /* Attempt ethernet without PW. */
        DecodeEthernet(tv, dtv, p, pkt, len, pq);
        break;
    }

    return TM_ECODE_OK;
}