source: test/test-mpls.c

#include "libtrace.h"
#include <stdio.h>
#include <stdlib.h>

void iferr(libtrace_t *trace)
{
        libtrace_err_t err = trace_get_err(trace);
        if (err.err_num==0)
                return;
        printf("Error: %s\n",err.problem);
        exit(1);
}


int main(int argc, char *argv[]) {

        libtrace_t *trace = NULL;
        libtrace_packet_t *packet = NULL;
        int i = 0;
        uint16_t mplslabel;
        uint8_t *mplsptr;
        uint32_t remaining;
        int error = 0;

        packet = trace_create_packet();

        trace = trace_create("pcapfile:traces/mpls.pcap");
        iferr(trace);

        trace_start(trace);
        iferr(trace);

        /* read a packet */
        trace_read_packet(trace, packet);
        /* first packet in this trace should have a vlan tag of 32 */
        mplslabel = trace_get_outermost_mpls(packet, &mplsptr, &remaining);
        if (mplslabel != 18) {
                printf("Failed to find correct outermost vlan tag\n");
                error = 1;
        }

        /* Second packet should not contain a MPLS label */
        trace_read_packet(trace, packet);
        mplslabel = trace_get_outermost_mpls(packet, &mplsptr, &remaining);
        if (mplslabel != MPLS_NOT_FOUND) {
                printf("Found MPLS label with none present\n");
                error = 1;
        }

        /* read a packet */
        trace_read_packet(trace, packet);
        mplslabel = trace_get_outermost_mpls(packet, &mplsptr, &remaining);
        if (mplslabel != 18) {
                printf("Failed to find correct outermost vlan tag\n");
                error = 1;
        }

        if (error == 0) {
                printf("success\n");
        } else {
                iferr(trace);
        }

        trace_destroy(trace);
        trace_destroy_packet(packet);

        return error;
}