/* * netifdebug.c -- change the IFF_DEBUG flag of an interface */#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <string.h>#include <errno.h>#include <sys/types.h>#include <sys/socket.h>#include <sys/ioctl.h>#include <net/if.h>#include <netinet/in.h>int main(int argc, char **argv){    int action = -1, sock;    struct ifreq req;    char *actname;    if (argc < 2) {        fprintf(stderr,"%s: usage is \"%s <ifname> [<on|off|tell>]\"\n",                argv[0],argv[0]);        exit(1);    }    if (argc==2)        actname="tell";    else        actname=argv[2];    /* a silly raw socket just for ioctl()ling it */    sock = socket(AF_INET, SOCK_RAW, IPPROTO_RAW);    if (sock < 0) {        fprintf(stderr, "%s: socket(): %s\n", argv[0],strerror(errno));        exit(1);    }    /* retrieve flags */    strcpy(req.ifr_name, argv[1]);    if ( ioctl(sock, SIOCGIFFLAGS, &req) < 0) {        fprintf(stderr, " %s: ioctl(SIOCGIFFLAGS): %s\n",                argv[0],strerror(errno));        exit(1);    }    if (!strcmp(actname,"on")        || !strcmp(actname,"+")        || !strcmp(actname,"1"))        action = IFF_DEBUG;    if (!strcmp(actname,"off")        || !strcmp(actname,"-")        || !strcmp(actname,"0"))        action = 0;    if (!strcmp(actname,"tell")        || actname[0]=='t') {        printf("%s: debug is %s\n", argv[1],               req.ifr_flags & IFF_DEBUG ? "on" : "off");        exit(0);    }    req.ifr_flags &= ~IFF_DEBUG;    req.ifr_flags |= action;    if ( ioctl(sock, SIOCSIFFLAGS, &req) < 0) {        fprintf(stderr, " %s: ioctl(SIOCSIFFLAGS): %s\n",                argv[0],strerror(errno));        exit(1);    }    exit(0);}