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/* Trivial libtrace program that prints all the MPLS tags within a packet.
* Designed to demonstrate the use of trace_get_payload_from_mpls()
*/
#include "libtrace.h"
#include <stdio.h>
#include <inttypes.h>
#include <assert.h>
#include <getopt.h>
static void print_mpls_label(void *mpls, uint32_t remaining) {
uint32_t label = 0;
if (remaining < 4)
return;
/* Cast MPLS header into a 32 bit number */
label = *(uint32_t *)mpls;
/* Label number is in network byte order */
label = ntohl(label);
/* MPLS labels are comprise only 20 of the 32 bits in the header */
label = (label >> 12) & 0x000fffff;
printf("%u ", label);
}
static void per_packet(libtrace_packet_t *packet)
{
void *l2 = NULL;
void *l2_payload = NULL;
libtrace_linktype_t link_type;
uint16_t ethertype;
uint32_t remaining;
l2 = trace_get_layer2(packet, &link_type, &remaining);
/* No layer 2 header */
if (l2 == NULL)
return;
/* XXX We could check if link_type is ethernet here, but this won't
* affect our results in any way */
l2_payload = trace_get_payload_from_layer2(l2, link_type, ðertype,
&remaining);
/* Incomplete layer 2 header */
if (l2_payload == NULL)
return;
/* No actual payload after the layer 2 header */
if (remaining == 0)
return;
/* Only look for MPLS labels as long as we have payload available
* to look at! */
while (l2_payload != NULL && remaining > 0) {
/* 0x8847 is the ethertype for MPLS headers */
if (ethertype == 0x8847) {
print_mpls_label(l2_payload, remaining);
/* Move onto the next header */
l2_payload = trace_get_payload_from_mpls(l2_payload,
ðertype, &remaining);
} else
/* Stop as soon as we encounter a non-MPLS header */
break;
}
printf("\n");
}
static void libtrace_cleanup(libtrace_t *trace, libtrace_packet_t *packet) {
/* It's very important to ensure that we aren't trying to destroy
* a NULL structure, so each of the destroy calls will only occur
* if the structure exists */
if (trace)
trace_destroy(trace);
if (packet)
trace_destroy_packet(packet);
}
int main(int argc, char *argv[])
{
/* This is essentially the same main function from readdemo.c */
libtrace_t *trace = NULL;
libtrace_packet_t *packet = NULL;
/* Ensure we have at least one argument after the program name */
if (argc < 2) {
fprintf(stderr, "Usage: %s inputURI\n", argv[0]);
return 1;
}
packet = trace_create_packet();
if (packet == NULL) {
perror("Creating libtrace packet");
libtrace_cleanup(trace, packet);
return 1;
}
trace = trace_create(argv[1]);
if (trace_is_err(trace)) {
trace_perror(trace,"Opening trace file");
libtrace_cleanup(trace, packet);
return 1;
}
if (trace_start(trace) == -1) {
trace_perror(trace,"Starting trace");
libtrace_cleanup(trace, packet);
return 1;
}
while (trace_read_packet(trace,packet)>0) {
per_packet(packet);
}
if (trace_is_err(trace)) {
trace_perror(trace,"Reading packets");
libtrace_cleanup(trace, packet);
return 1;
}
libtrace_cleanup(trace, packet);
return 0;
}
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