pcap/glibc bug?

first change "wlan0" on the source code with your interface, after
"gcc filename.c -lpcap"



#include <pcap.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <unistd.h>

pcap_t *pcap = NULL;
pcap_dumper_t *pdump;

void decode(u_char* param, const struct pcap_pkthdr *pkthdr, const u_char *pkt)
{
   pcap_dump((u_char*)param, pkthdr, pkt);
}

static void close_network()
{
   fprintf(stderr,"closing network \n");
   pcap_close(pcap);
   pcap_dump_close(pdump);
}

void disable_interface_offload(void)
{
   char *newargv[] = {"ethtool", "-K", "wlan0", "tso", "off", "gso", "off", "gro", "off", "lro", "off", NULL };
   int ret_val;

   switch(fork()) {
      case 0:
         execvp("ethtool", newargv);
         fprintf(stderr,"problem, ethtool not found!\n\n");
         exit(10); // this one causes the double header inclusion
         //_exit(10); // while this one does not
      default:
         wait(&ret_val);
   }
int main()
{
   char pcap_errbuf[PCAP_ERRBUF_SIZE];
   pcap = pcap_open_live("wlan0", UINT16_MAX, 1, 0, pcap_errbuf);
   if(pcap==NULL)
      printf("\n\nPCAP NULL\n\n");
   pdump = pcap_dump_open(pcap, "out.pcap");
   if(pcap==NULL)
      printf("\n\nPDUMP NULL\n\n");
   disable_interface_offload();
   pcap_loop(pcap, 2, decode, (unsigned char *)pdump);
   return 0;
}