nfct-mnl-set-label.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

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

struct callback_args {
        struct mnl_socket *nl;
        unsigned int seq;
        int bit;
};

static void set_label(struct nf_conntrack *ct, struct callback_args *cbargs)
{
        struct nfct_bitmask *b = (void *) nfct_get_attr(ct, ATTR_CONNLABELS);
        int bit = cbargs->bit;
        char buf[MNL_SOCKET_BUFFER_SIZE];
        struct nlmsghdr *nlh;
        struct nfgenmsg *nfh;

        if (b) {
                if (bit < 0)
                        b = nfct_bitmask_new(0);
                else if (nfct_bitmask_test_bit(b, bit))
                        return;
        } else {
                b = nfct_bitmask_new(0);
        }

        if (!b)
                return;
        if (bit >= 0)
                nfct_bitmask_set_bit(b, bit);
        nfct_set_attr(ct, ATTR_CONNLABELS, b);

        if (bit >= 0) {
                b = nfct_bitmask_new(bit);
                if (b) {
                        nfct_bitmask_set_bit(b, bit);
                        nfct_set_attr(ct, ATTR_CONNLABELS_MASK, b);
                }
        }

        cbargs->seq++;

        nlh = mnl_nlmsg_put_header(buf);
        nlh->nlmsg_type = (NFNL_SUBSYS_CTNETLINK << 8) | IPCTNL_MSG_CT_NEW;
        nlh->nlmsg_flags = NLM_F_REQUEST|NLM_F_CREATE;
        nlh->nlmsg_seq = cbargs->seq;

        nfh = mnl_nlmsg_put_extra_header(nlh, sizeof(struct nfgenmsg));
        nfh->nfgen_family = nfct_get_attr_u8(ct, ATTR_L3PROTO);
        nfh->version = NFNETLINK_V0;
        nfh->res_id = 0;

        nfct_nlmsg_build(nlh, ct);

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

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

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

        nfct_nlmsg_parse(nlh, ct);

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

        set_label(ct, data);

        nfct_destroy(ct);

        return MNL_CB_OK;
}

static void show_labels(struct nfct_labelmap *l)
{
        unsigned int i = 0;
        const char *name;

        if (l) {
                fputs("usage: program label, configured labels are:\n", stderr);
                while ((name = nfct_labelmap_get_name(l, i))) {
                        if (*name)
                                fprintf(stderr, "%s -> bit %d\n", name, i);
                        i++;
                }
        } else {
                fputs("no labels configured, usage: program bit\n", stderr);
        }
        exit(1);
}

static struct mnl_socket *sock_nl_create(void)
{
        struct mnl_socket *nl;

        nl = mnl_socket_open(NETLINK_NETFILTER);
        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);
        }

        return nl;
}

int main(int argc, char *argv[])
{
        struct mnl_socket *nl;
        struct nlmsghdr *nlh;
        struct nfgenmsg *nfh;
        char buf[MNL_SOCKET_BUFFER_SIZE];
        unsigned int seq, portid;
        struct callback_args cbargs;
        int ret;
        struct nfct_labelmap *l = nfct_labelmap_new(NULL);

        if (argc < 2)
                show_labels(l);

        cbargs.bit = l ? nfct_labelmap_get_bit(l, argv[1]) : -1;

        if (cbargs.bit < 0) {
                cbargs.bit = atoi(argv[1]);
                if (cbargs.bit == 0 && argv[1][0] != '0')
                        show_labels(l);
        }

        if (cbargs.bit < 0)
                puts("will clear all labels");
        else
                printf("will set label bit %d\n", cbargs.bit);

        nl = sock_nl_create();
        portid = mnl_socket_get_portid(nl);

        nlh = mnl_nlmsg_put_header(buf);
        nlh->nlmsg_type = (NFNL_SUBSYS_CTNETLINK << 8) | IPCTNL_MSG_CT_GET;
        nlh->nlmsg_flags = NLM_F_REQUEST|NLM_F_DUMP;
        nlh->nlmsg_seq = seq = time(NULL);

        nfh = mnl_nlmsg_put_extra_header(nlh, sizeof(struct nfgenmsg));
        nfh->nfgen_family = AF_UNSPEC;
        nfh->version = NFNETLINK_V0;
        nfh->res_id = 0;


        ret = mnl_socket_sendto(nl, nlh, nlh->nlmsg_len);
        if (ret == -1) {
                perror("mnl_socket_sendto");
                exit(EXIT_FAILURE);
        }

        ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));


        cbargs.nl = sock_nl_create();
        cbargs.seq = seq;

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

        if (l)
                nfct_labelmap_destroy(l);
        mnl_socket_close(nl);

        return 0;
}