recvfrom_debug2

#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <net/if.h>
#include <pthread.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <linux/if_packet.h>
#include <netinet/if_ether.h>
#include <stdlib.h>
#include <sys/wait.h>

#define NBNS_NBSTATREQ_LEN 50

/**
 * @brief static NetBIOS NBSTAT request.
 *
 * RFC 1002, Paragraph 4.2.17
 */
uint8_t nbns_nbstat_request[NBNS_NBSTATREQ_LEN] = {
    0x82, 0x28, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x20, 0x43, 0x4B, 0x41, 0x41, 0x41, 0x41, 0x41,
    0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41,
    0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41,
    0x41, 0x41, 0x41, 0x41, 0x41, 0x00, 0x00, 0x21, 0x00, 0x01
};

char running = 1;
//pid_t receiver_pid;
long unsigned int total, bad;

void *sender(void *arg) {
  int sockfd;
  struct sockaddr_in addr;

  sockfd = socket(AF_INET, SOCK_DGRAM, 0);

  memset(&addr, 0, sizeof(addr));

  addr.sin_family = AF_INET;
  addr.sin_port = htons(137);
  addr.sin_addr.s_addr = htonl(0x0AA9A7FE); // 10.169.167.254

  connect(sockfd, (struct sockaddr *) &addr, sizeof(addr));

  while(running) {
    write(sockfd, nbns_nbstat_request, NBNS_NBSTATREQ_LEN);
    usleep(100);
  }

  sendto(sockfd, nbns_nbstat_request, NBNS_NBSTATREQ_LEN, 0, (struct sockaddr *) &addr, sizeof(addr));

  return NULL;
}

void stop(int signal) {
  running = 0;
}

static int
iface_get_id(const char *device)
{
  struct ifreq  ifr;
  int fd;

  // this is the main difference from pcap:
  // we use another socket for perform ioctl interrogations
  fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_IP);

  memset(&ifr, 0, sizeof(ifr));
  strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));

  if (ioctl(fd, SIOCGIFINDEX, &ifr) == -1) {
    fprintf(stderr, "SIOCGIFINDEX: %s\n", strerror(errno));
    close(fd);
    return -1;
  }
  close(fd);

  return ifr.ifr_ifindex;
}

void *receiver(void *arg) {
  int sockfd;
  int ifindex;
  struct sockaddr_ll  sll;
  int     err;
  socklen_t   errlen = sizeof(err);
  socklen_t   fromlen;
  size_t packet_len;
  char buffer[1514];

  /* pcap_open_live */

  sockfd = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));

  ifindex = iface_get_id((char *) arg);

  if(ifindex==-1) return NULL;

  memset(&sll, 0, sizeof(sll));
  sll.sll_family    = AF_PACKET;
  sll.sll_ifindex   = ifindex;
  sll.sll_protocol  = htons(ETH_P_ALL);

  if (bind(sockfd, (struct sockaddr *) &sll, sizeof(sll)) == -1) {
    fprintf(stderr, "bind: %s\n", strerror(errno));
    return NULL;
  }

  /* Any pending errors, e.g., network is down? */

  if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &err, &errlen) == -1) {
    fprintf(stderr, "getsockopt: %s\n", strerror(errno));
    return NULL;
  }

  if (err > 0) {
    fprintf(stderr, "bind: %s\n", strerror(err));
    return NULL;
  }

  /* pcap_open_live ends */

  /* pcap_loop */

  fromlen = sizeof(sll);

  while(running) {

    do {
      packet_len = recvfrom(sockfd, buffer, 1514, MSG_TRUNC,
                            (struct sockaddr *) &sll, &fromlen);
    } while(running && packet_len == -1 && (errno == EINTR || errno == EAGAIN));

    if(running && packet_len == -1) {
      fprintf(stderr, "recvfrom: %s\n", strerror(errno));
      return NULL;
    }

    if(packet_len > 14) {
      total++;

      fprintf(stderr, "sll: { sll_family=%d, sll_protocol=%d, sll_ifindex=%d, sll_hatype=%d, sll_pkttype=%d, sll_halen=%d, sll_addr=[%02hhX:%02hhX:%02hhX:%02hhX:%02hhX:%02hhX:%02hhX:%02hhX] }\n",
              sll.sll_family, sll.sll_protocol, sll.sll_ifindex, sll.sll_hatype,
              sll.sll_pkttype, sll.sll_halen, sll.sll_addr[0], sll.sll_addr[1],
              sll.sll_addr[2], sll.sll_addr[3], sll.sll_addr[4], sll.sll_addr[5],
              sll.sll_addr[6], sll.sll_addr[7]);


      fprintf(stderr, "%02hhX:%02hhX:%02hhX:%02hhX:%02hhX:%02hhX => %02hhX:%02hhX:%02hhX:%02hhX:%02hhX:%02hhX\n",
              buffer[6], buffer[7], buffer[8], buffer[9], buffer[10], buffer[11],
              buffer[0], buffer[1], buffer[2], buffer[3], buffer[4], buffer[5]);
      fflush(stderr);

      if(memcmp(buffer, sll.sll_addr, 6) && memcmp(buffer + 6, sll.sll_addr, 6)) {
        bad++;
      }
    }

  }

  /* pcap_loop ends */

  close(sockfd);

  return NULL;
}

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

  if(argc != 2) return 1;

  if(signal(SIGINT, stop) == SIG_ERR) return 2;

  bad = total = 0;

#ifdef SENDER
  sender((void *) argv[1]);
#else
  receiver((void *) argv[1]);
#endif

  running=0;

#ifndef SENDER
  fprintf(stderr, "total packets: %lu\nbad ones: %lu\n", total, bad);
#endif

  exit(0); // close all unclear stuff [ hey, is a test program ;) ]
}