偵測網路interface改變

#include <stdio.h>
#include <string.h>
#include <netinet/in.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <net/if.h>

int main(){
struct sockaddr_nl addr;
int sock, len;
char buffer[4096];
struct nlmsghdr *nlh;

if((sock = socket(PF_NETLINK, SOCK_RAW, NETLINK_ROUTE))== -1){
perror("couldn't open NETLINK_ROUTE socket");
return 1;
}

memset(&addr, 0, sizeof(addr));
addr.nl_family = AF_NETLINK;
addr.nl_groups = RTMGRP_IPV4_IFADDR;

if(bind(sock, (struct sockaddr *)&addr, sizeof(addr)) == -1){
perror("couldn't bind");
return 1;
}

nlh = (struct nlmsghdr *)buffer;
while((len=recv(sock, nlh, 4096, 0)) > 0){
while((NLMSG_OK(nlh, len)) && (nlh->nlmsg_type != NLMSG_DONE)){
if(nlh->nlmsg_type == RTM_NEWADDR){
struct ifaddrmsg *ifa = (struct ifaddrmsg *)NLMSG_DATA(nlh);
struct rtattr *rth = IFA_RTA(ifa);
int rtl = IFA_PAYLOAD(nlh);

while(rtl && RTA_OK(rth, rtl)){
if(rth->rta_type == IFA_LOCAL){
uint32_t ipaddr = htonl(*((uint32_t *)RTA_DATA(rth)));
char name[IFNAMSIZ];
if_indextoname(ifa->ifa_index, name);
printf("%s is now %d.%d.%d.%d\n", name, (ipaddr >> 24) & 0xff, (ipaddr >> 16) & 0xff, (ipaddr >> 8) & 0xff, ipaddr & 0xff);
}
rth = RTA_NEXT(rth, rtl);
}
}
nlh= NLMSG_NEXT(nlh, len);
}
}
return 0;
}