linux netlink实例

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>

#define BUFLEN 2048

void die(char *s) {
    perror(s);
    exit(1);
}

int main(void) {
    int fd, cnt;
    struct sockaddr_nl nladdr;
    struct nlmsghdr *nlh = NULL;
    struct iovec iov;
    int sock_buf_size;
    char buf[BUFLEN];

    fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
    if (fd < 0)
        die("socket");

    memset(&nladdr, 0, sizeof(nladdr));
    nladdr.nl_family = AF_NETLINK;
    nladdr.nl_pid = getpid();
    nladdr.nl_groups = RTMGRP_IPV4_ROUTE;

    if (bind(fd, (struct sockaddr*)&nladdr, sizeof(nladdr)) < 0)
        die("bind");

    iov.iov_base = (void *)buf;
    iov.iov_len = BUFLEN;
    nlh = (struct nlmsghdr *)buf;

    while ((cnt = recvmsg(fd, &iov, 0)) > 0) {
        for (; NLMSG_OK(nlh, cnt); nlh = NLMSG_NEXT(nlh, cnt)) {
            if (nlh->nlmsg_type == NLMSG_DONE)
                break;
            else if (nlh->nlmsg_type == RTM_NEWROUTE || nlh->nlmsg_type == RTM_DELROUTE) {
                // 处理路由消息
                printf("Route change detected!\n");
            }
        }
    }

    close(fd);
    return 0;
}