问网络流量上的软件中断

EN

/* compile with -lpcap */
/* run as root         */

#include <stdio.h>
#include <sys/poll.h>
#include <pcap.h>

int main(int argc, char *argv[])
{
    int color = 0;
    struct pollfd ufd;
    struct pcap_pkthdr h;
    char errbuf[PCAP_ERRBUF_SIZE];
    pcap_t *p = pcap_open_live(NULL, 0, 0, 0, errbuf);
    if (!p) return puts(errbuf), 1;

    ufd.fd = pcap_fileno(p);
    ufd.events = POLLIN;
    for (; ; )
        switch (poll(&ufd, 1, 100))
        {
        case -1:    perror("poll"); return 1;
        case  0:    if  (color) color = 0, puts("red"); break;
        default:    if (!color) color = 1, puts("green");
                    pcap_next(p, &h);
        }
}