rtnl-addr-dump.c

/* This example is placed in the public domain. */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <time.h>
#include <arpa/inet.h>

#include <libmnl/libmnl.h>
#include <linux/if.h>
#include <linux/if_link.h>
#include <linux/rtnetlink.h>

static int data_attr_cb(const struct nlattr *attr, void *data)
{
        const struct nlattr **tb = data;
        int type = mnl_attr_get_type(attr);

        /* skip unsupported attribute in user-space */
        if (mnl_attr_type_valid(attr, IFA_MAX) < 0)
                return MNL_CB_OK;

        switch(type) {
        case IFA_ADDRESS:
                if (mnl_attr_validate(attr, MNL_TYPE_BINARY) < 0) {
                        perror("mnl_attr_validate");
                        return MNL_CB_ERROR;
                }
                break;
        }
        tb[type] = attr;
        return MNL_CB_OK;
}

static int data_cb(const struct nlmsghdr *nlh, void *data)
{
        struct nlattr *tb[IFLA_MAX+1] = {};
        struct ifaddrmsg *ifa = mnl_nlmsg_get_payload(nlh);

        printf("index=%d family=%d ", ifa->ifa_index, ifa->ifa_family);

        mnl_attr_parse(nlh, sizeof(*ifa), data_attr_cb, tb);
        printf("addr=");
        if (tb[IFA_ADDRESS]) {
                void *addr = mnl_attr_get_payload(tb[IFA_ADDRESS]);
                char out[INET6_ADDRSTRLEN];

                if (inet_ntop(ifa->ifa_family, addr, out, sizeof(out)))
                        printf("%s ", out);
        }
        printf("scope=");
        switch(ifa->ifa_scope) {
        case 0:
                printf("global ");
                break;
        case 200:
                printf("site ");
                break;
        case 253:
                printf("link ");
                break;
        case 254:
                printf("host ");
                break;
        case 255:
                printf("nowhere ");
                break;
        default:
                printf("%d ", ifa->ifa_scope);
                break;
        }

        printf("\n");
        return MNL_CB_OK;
}

int main(int argc, char *argv[])
{
        struct mnl_socket *nl;
        char buf[MNL_SOCKET_BUFFER_SIZE];
        struct nlmsghdr *nlh;
        struct rtgenmsg *rt;
        int ret;
        unsigned int seq, portid;

        if (argc != 2) {
                fprintf(stderr, "Usage: %s <inet|inet6>\n", argv[0]);
                exit(EXIT_FAILURE);
        }

        nlh = mnl_nlmsg_put_header(buf);
        nlh->nlmsg_type = RTM_GETADDR;
        nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP;
        nlh->nlmsg_seq = seq = time(NULL);
        rt = mnl_nlmsg_put_extra_header(nlh, sizeof(struct rtgenmsg));
        if (strcmp(argv[1], "inet") == 0)
                rt->rtgen_family = AF_INET;
        else if (strcmp(argv[1], "inet6") == 0)
                rt->rtgen_family = AF_INET6;

        nl = mnl_socket_open(NETLINK_ROUTE);
        if (nl == NULL) {
                perror("mnl_socket_open");
                exit(EXIT_FAILURE);
        }

        if (mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID) < 0) {
                perror("mnl_socket_bind");
                exit(EXIT_FAILURE);
        }
        portid = mnl_socket_get_portid(nl);

        if (mnl_socket_sendto(nl, nlh, nlh->nlmsg_len) < 0) {
                perror("mnl_socket_sendto");
                exit(EXIT_FAILURE);
        }

        ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
        while (ret > 0) {
                ret = mnl_cb_run(buf, ret, seq, portid, data_cb, NULL);
                if (ret <= MNL_CB_STOP)
                        break;
                ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
        }
        if (ret == -1) {
                perror("error");
                exit(EXIT_FAILURE);
        }

        mnl_socket_close(nl);

        return 0;
}