rtnl-link-dump.c

/* This example is placed in the public domain. */
#include <stdio.h>
#include <stdlib.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, IFLA_MAX) < 0)
                return MNL_CB_OK;

        switch(type) {
        case IFLA_ADDRESS:
                if (mnl_attr_validate(attr, MNL_TYPE_BINARY) < 0) {
                        perror("mnl_attr_validate");
                        return MNL_CB_ERROR;
                }
                break;
        case IFLA_MTU:
                if (mnl_attr_validate(attr, MNL_TYPE_U32) < 0) {
                        perror("mnl_attr_validate");
                        return MNL_CB_ERROR;
                }
                break;
        case IFLA_IFNAME:
                if (mnl_attr_validate(attr, MNL_TYPE_STRING) < 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 ifinfomsg *ifm = mnl_nlmsg_get_payload(nlh);

        printf("index=%d type=%d flags=%d family=%d ", 
                ifm->ifi_index, ifm->ifi_type,
                ifm->ifi_flags, ifm->ifi_family);

        if (ifm->ifi_flags & IFF_RUNNING)
                printf("[RUNNING] ");
        else
                printf("[NOT RUNNING] ");

        mnl_attr_parse(nlh, sizeof(*ifm), data_attr_cb, tb);
        if (tb[IFLA_MTU]) {
                printf("mtu=%d ", mnl_attr_get_u32(tb[IFLA_MTU]));
        }
        if (tb[IFLA_IFNAME]) {
                printf("name=%s ", mnl_attr_get_str(tb[IFLA_IFNAME]));
        }
        if (tb[IFLA_ADDRESS]) {
                uint8_t *hwaddr = mnl_attr_get_payload(tb[IFLA_ADDRESS]);
                int i;

                printf("hwaddr=");
                for (i=0; i<mnl_attr_get_payload_len(tb[IFLA_ADDRESS]); i++) {
                        printf("%.2x", hwaddr[i] & 0xff);
                        if (i+1 != mnl_attr_get_payload_len(tb[IFLA_ADDRESS]))
                                printf(":");
                }
        }
        printf("\n");
        return MNL_CB_OK;
}

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

        nlh = mnl_nlmsg_put_header(buf);
        nlh->nlmsg_type = RTM_GETLINK;
        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));
        rt->rtgen_family = AF_PACKET;

        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;
}