libpcap latency/break test

testpcap.c

#include <pcap.h>
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <unistd.h>
#include <signal.h>

pcap_t* pcap;

void* thread(void* arg) {
  (void)arg;
  sleep(2);
  kill(0, SIGALRM);
  return NULL;
}

void handle_signal(int sig) {
  pcap_breakloop(pcap);
  fprintf(stderr, "handle signal %d\n", sig);
}

int main(int argc, char** argv) {
  (void)argc;
  (void)argv;

  signal(SIGALRM, handle_signal);

  char errbuf[PCAP_ERRBUF_SIZE];
#if 0
  pcap = pcap_open_live("enp0s3", 1500, 1, 100, errbuf);
  if (pcap == NULL) {
    fprintf(stderr, "Failed to create pcap handle: %s\n", errbuf);
    return EXIT_FAILURE;
  }
#else
  pcap = pcap_create("enp0s3", errbuf);
  if (pcap == NULL) {
    fprintf(stderr, "Failed to create pcap handle: %s\n", errbuf);
    return EXIT_FAILURE;
  }
  pcap_set_immediate_mode(pcap, 1);
  pcap_set_timeout(pcap, 100);
  if (pcap_activate(pcap) != 0) {
    fprintf(stderr, "Failed to activate pcap: %s\n", pcap_geterr(pcap));
    pcap_close(pcap);
    return EXIT_FAILURE;
  }
#endif
  struct pcap_pkthdr* pkt_header = NULL;
  const u_char* pkt_data = NULL;

  pthread_t thr;
  pthread_create(&thr, NULL, &thread, NULL);

  while (1) {
    int res = pcap_next_ex(pcap, &pkt_header, &pkt_data);
    if (res == 1) {
      struct tm* tstm = gmtime(&pkt_header->ts.tv_sec);
      char tmbuf[128];
      strftime(tmbuf, sizeof tmbuf, "%Y-%m-%dT%H:%M:%S", tstm);
      printf("%s.%06ld ", tmbuf, pkt_header->ts.tv_usec);

      struct timeval nowtv;
      gettimeofday(&nowtv, NULL);
      tstm = gmtime(&nowtv.tv_sec);
      strftime(tmbuf, sizeof tmbuf, "%Y-%m-%dT%H:%M:%S", tstm);
      printf("%s.%06ld ", tmbuf, nowtv.tv_usec);

      long secDelta = nowtv.tv_sec - pkt_header->ts.tv_sec;
      long usecDelta = nowtv.tv_usec - pkt_header->ts.tv_usec;
      double delta = secDelta + usecDelta / 1000000.0;
      printf(" %.6f\n", delta);
    }
    else if (res == 0)
      printf("pcap_next_ex timeout\n");
    else if (res < 0) {
      fprintf(stderr, "Failed to read: %d, %s\n", res, pcap_geterr(pcap));
      pcap_close(pcap);
      return EXIT_FAILURE;
    } else {
      printf("pcap_next_ex returned %d\n", res);
    }
  }
  return 0;
}