genl-group-events.c

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

#include <libmnl/libmnl.h>
#include <linux/genetlink.h>

static int group;

static int data_cb(const struct nlmsghdr *nlh, void *data)
{
        printf("received event type=%d from genetlink group %d\n",
                nlh->nlmsg_type, group);
        return MNL_CB_OK;
}

int main(int argc, char *argv[])
{
        struct mnl_socket *nl;
        char buf[MNL_SOCKET_BUFFER_SIZE];
        int ret;

        if (argc != 2) {
                printf("%s [group]\n", argv[0]);
                exit(EXIT_FAILURE);
        }
        group = atoi(argv[1]);

        nl = mnl_socket_open(NETLINK_GENERIC);
        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);
        }

        if (mnl_socket_setsockopt(nl, NETLINK_ADD_MEMBERSHIP, &group,
                                  sizeof(int)) < 0) {
                perror("mnl_socket_setsockopt");
                exit(EXIT_FAILURE);
        }

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

        mnl_socket_close(nl);

        return 0;
}