On Apr 17, 2013, at 6:56 PM, wen lui <esolvepol...@gmail.com> wrote:
> handle = pcap_open_live(dev, BUFSIZ, 0, 0, errbuf);
> pcap_compile(handle, &fp, filter_exp, 0, mask) == -1
> pcap_setfilter(handle, &fp);
> struct pcap_pkthdr pcap_header; // The header that pcap gives us
> const u_char *pcap_packet; // The actual packet
>
> while(1){
>
> n=fork();
> if(n==0) { // child process
> fd_set rdfds;
> int pcap_fd = pcap_get_selectable_fd(pcap_handler);
> for(;;){
> FD_ZERO(&rdfds);
> FD_SET(pcap_fd, &rdfds);
> FD_SET(sd_proxy, &rdfds); // here is another fd
>
> select(pcap_fd>sd_proxy?pcap_fd+1:sd_proxy+1,&rdfds,
> NULL, NULL, NULL)
Yes, that's at least a start at writing the kind of code needed for
http://stackoverflow.com/questions/16067015/blocking-pcap-and-multiple-i-o-select
You should be checking the return value of select() for errors, and reporting
errors if they occur, just to be sure.
>From the
> struct pcap_pkthdr pcap_header; // The header that pcap gives us
> const u_char *pcap_packet; // The actual packet
I suspect you're using pcap_next() or pcap_next_ex().
If you're going to use them with select(), you have to use them in a very
specific way.
First of all, you need to put the pcap_t in non-blocking mode. After the
pcap_open_live() call, do:
if (pcap_setnonblock(handle, 1, errbuf) == -1) {
fprintf(stderr, "pcap_setnonblock failed: %s\n", errbuf);
exit(2);
}
Then, of course, you check rdfds; if the bit for pcap_fd is set, do:
for (;;) {
switch (pcap_next_ex(handle, &pcap_header,
&pcap_packet)) {
case -1:
/* Error */
fprintf(stderr, "pcap_next_ex failed: %s\n",
pcap_geterr(handle));
exit(2);
break;
case 0:
/* No more packets to read for now */
goto done;
case -2:
/* Somebody called pcap_breakloop() */
goto done;
default:
/* Process the packet */
do whatever you do with pcap_header and
pcap_packet;
break;
}
done:
;
The "case -2" case can be left out if you don't call pcap_breakloop() in your
program.
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