rtnl-route-add.c

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

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

int main(int argc, char *argv[])
{
        struct mnl_socket *nl;
        char buf[MNL_SOCKET_BUFFER_SIZE];
        struct nlmsghdr *nlh;
        struct rtmsg *rtm;
        uint32_t prefix, seq, portid;
        union {
                in_addr_t ip;
                struct in6_addr ip6;
        } dst;
        union {
                in_addr_t ip;
                struct in6_addr ip6;
        } gw;
        int iface, ret, family = AF_INET;

        if (argc <= 3) {
                printf("Usage: %s iface destination cidr [gateway]\n", argv[0]);
                printf("Example: %s eth0 10.0.1.12 32 10.0.1.11\n", argv[0]);
                printf("         %s eth0 ffff::10.0.1.12 128 fdff::1\n", argv[0]);
                exit(EXIT_FAILURE);
        }

        iface = if_nametoindex(argv[1]);
        if (iface == 0) {
                perror("if_nametoindex");
                exit(EXIT_FAILURE);
        }

        if (!inet_pton(AF_INET, argv[2], &dst)) {
                if (!inet_pton(AF_INET6, argv[2], &dst)) {
                        perror("inet_pton");
                        exit(EXIT_FAILURE);
                }
                family = AF_INET6;
        }

        if (sscanf(argv[3], "%u", &prefix) == 0) {
                perror("sscanf");
                exit(EXIT_FAILURE);
        }

        if (argc == 5 && !inet_pton(family, argv[4], &gw)) {
                perror("inet_pton");
                exit(EXIT_FAILURE);
        }

        nlh = mnl_nlmsg_put_header(buf);
        nlh->nlmsg_type = RTM_NEWROUTE;
        nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_CREATE | NLM_F_ACK;
        nlh->nlmsg_seq = seq = time(NULL);

        rtm = mnl_nlmsg_put_extra_header(nlh, sizeof(struct rtmsg));
        rtm->rtm_family = family;
        rtm->rtm_dst_len = prefix;
        rtm->rtm_src_len = 0;
        rtm->rtm_tos = 0;
        rtm->rtm_protocol = RTPROT_STATIC;
        rtm->rtm_table = RT_TABLE_MAIN;
        rtm->rtm_type = RTN_UNICAST;
        /* is there any gateway? */
        rtm->rtm_scope = (argc == 4) ? RT_SCOPE_LINK : RT_SCOPE_UNIVERSE;
        rtm->rtm_flags = 0;

        if (family == AF_INET)
                mnl_attr_put_u32(nlh, RTA_DST, dst.ip);
        else
                mnl_attr_put(nlh, RTA_DST, sizeof(struct in6_addr), &dst);

        mnl_attr_put_u32(nlh, RTA_OIF, iface);
        if (argc == 5) {
                if (family == AF_INET)
                        mnl_attr_put_u32(nlh, RTA_GATEWAY, gw.ip);
                else {
                        mnl_attr_put(nlh, RTA_GATEWAY, sizeof(struct in6_addr),
                                        &gw.ip6);
                }
        }

        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));
        if (ret < 0) {
                perror("mnl_socket_recvfrom");
                exit(EXIT_FAILURE);
        }

        ret = mnl_cb_run(buf, ret, seq, portid, NULL, NULL);
        if (ret < 0) {
                perror("mnl_cb_run");
                exit(EXIT_FAILURE);
        }

        mnl_socket_close(nl);

        return 0;
}