linux 3 netlink

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>

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

int main() {
    int sockfd;
    struct sockaddr_nl src_addr, dest_addr;
    struct nlmsghdr *nlh = NULL;
    struct iovec iov;
    int ret;

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

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

    if (bind(sockfd, (struct sockaddr*)&src_addr, sizeof(src_addr)) < 0) die("bind");

    memset(&dest_addr, 0, sizeof(dest_addr));
    dest_addr.nl_family = AF_NETLINK;
    dest_addr.nl_pid = 0; // For Linux Kernel
    dest_addr.nl_groups = 0;

    nlh = (struct nlmsghdr *)malloc(NLMSG_SPACE(sizeof(struct rtmsg)));
    memset(nlh, 0, NLMSG_SPACE(sizeof(struct rtmsg)));
    nlh->nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg));
    nlh->nlmsg_pid = getpid();
    nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP;
    nlh->nlmsg_type = RTM_GETLINK;

    iov.iov_base = (void *)nlh;
    iov.iov_len = nlh->nlmsg_len;
    ret = sendto(sockfd, &iov, 2, 0, (struct sockaddr*)&dest_addr, sizeof(dest_addr));
    if (ret < 0) die("sendto");

    while (1) {
        ret = recvmsg(sockfd, &msg, 0);
        if (ret < 0) die("recvmsg");
        for (nlh = (struct nlmsghdr *)msg.msg_iov->iov_base; NLMSG_OK(nlh, ret); nlh = NLMSG_NEXT(nlh, ret)) {
            if (nlh->nlmsg_type == NLMSG_DONE) {
                return 0;
            }
            if (nlh->nlmsg_type == RTM_NEWLINK) {
                struct ifinfomsg *ifi = (struct ifinfomsg *)NLMSG_DATA(nlh);
                printf("Interface: %s\n", if_indextoname(ifi->ifi_index, ifi_name));
            }
        }
    }

    close(sockfd);
    return 0;
}