c++ - How do I make libpcap/pcap_loop non-blocking? -

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i'm using libpcap sniff traffic in promiscuous mode 

int main()  {     // stuff     printf("opening device: %s\n", devname.c_str());      handle = pcap_open_live(devname.c_str(), 65536 , 1 , 0 , errbuf);      if (handle == null)     {         fprintf(stderr, "couldn't open device %s : %s..." , devname.c_str(), errbuf);         return 1;     }     printf(" done\n");      pcap_loop(handle , -1 , process_packet , null);     // here run thread stuff. however, pcap_loop blocking     return 0; }

i'd add external thread other stuff. how change code above make non-blocking?

when use non-blocking mode on libpcap have use pcap_dispatch, note, pcap_dispatch can work in blocking or in non-blocking mode, depends how set libpcap, set libpcap work in non-blocking have use function pcap_setnonblock:

int pcap_setnonblock(pcap_t *p, int nonblock, char *errbuf);

the difference between blocking , non-blocking not loop runs forever, in blocking function pcap_dispatch waits packet , returns when packet received, however, in non-blocking mode function returns , callback must process packet.

in "non-blocking" mode, attempt read capture descriptor pcap_dispatch() will, if no packets available read, return 0 rather blocking waiting packets arrive. pcap_loop() , pcap_next() not work in "non-blocking" mode.

http://www.tcpdump.org/manpages/pcap_setnonblock.3pcap.html


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