nfct-mnl-event.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <arpa/inet.h>

#include <libmnl/libmnl.h>
#include <libnetfilter_conntrack/libnetfilter_conntrack.h>

static int data_cb(const struct nlmsghdr *nlh, void *data)
{
        struct nf_conntrack *ct;
        uint32_t type = NFCT_T_UNKNOWN;
        char buf[4096];

        switch(nlh->nlmsg_type & 0xFF) {
        case IPCTNL_MSG_CT_NEW:
                if (nlh->nlmsg_flags & (NLM_F_CREATE|NLM_F_EXCL))
                        type = NFCT_T_NEW;
                else
                        type = NFCT_T_UPDATE;
                break;
        case IPCTNL_MSG_CT_DELETE:
                type = NFCT_T_DESTROY;
                break;
        }

        ct = nfct_new();
        if (ct == NULL)
                return MNL_CB_OK;

        nfct_nlmsg_parse(nlh, ct);

        nfct_snprintf(buf, sizeof(buf), ct,
                        type, NFCT_O_DEFAULT, 0);
        printf("%s\n", buf);

        nfct_destroy(ct);

        return MNL_CB_OK;
}

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

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

        if (mnl_socket_bind(nl, NF_NETLINK_CONNTRACK_NEW |
                                NF_NETLINK_CONNTRACK_UPDATE |
                                NF_NETLINK_CONNTRACK_DESTROY,
                                MNL_SOCKET_AUTOPID) < 0) {
                perror("mnl_socket_bind");
                exit(EXIT_FAILURE);
        }

        while (1) {
                ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
                if (ret == -1) {
                        perror("mnl_socket_recvfrom");
                        exit(EXIT_FAILURE);
                }

                ret = mnl_cb_run(buf, ret, 0, 0, data_cb, NULL);
                if (ret == -1) {
                        perror("mnl_cb_run");
                        exit(EXIT_FAILURE);
                }
        }

        mnl_socket_close(nl);

        return 0;
}