expect_create_userspace.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <arpa/inet.h>

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

/*
 * This example shows how to setup a user-space expectation. This requires
 * a Linux kernel >= 2.6.37.
 */

int main(void)
{
        int ret;
        struct nfct_handle *h;
        struct nf_conntrack *master, *expected, *mask;
        struct nf_expect *exp;

        /*
         * Step 1: Setup master conntrack
         */

        master = nfct_new();
        if (!master) {
                perror("nfct_new");
                exit(EXIT_FAILURE);
        }

        nfct_set_attr_u8(master, ATTR_L3PROTO, AF_INET);
        nfct_set_attr_u32(master, ATTR_IPV4_SRC, inet_addr("1.1.1.1"));
        nfct_set_attr_u32(master, ATTR_IPV4_DST, inet_addr("2.2.2.2"));

        nfct_set_attr_u8(master, ATTR_L4PROTO, IPPROTO_TCP);
        nfct_set_attr_u16(master, ATTR_PORT_SRC, htons(1025));
        nfct_set_attr_u16(master, ATTR_PORT_DST, htons(21));

        nfct_setobjopt(master, NFCT_SOPT_SETUP_REPLY);

        nfct_set_attr_u8(master, ATTR_TCP_STATE, TCP_CONNTRACK_ESTABLISHED);
        nfct_set_attr_u32(master, ATTR_TIMEOUT, 200);

        h = nfct_open(CONNTRACK, 0);
        if (!h) {
                perror("nfct_open");
                return -1;
        }

        /*
         * In a real scenario in which you want to implement an helper in
         * user-space with NFQUEUE, the master conntrack does not need to
         * be created, since it should already exist.
         */
        ret = nfct_query(h, NFCT_Q_CREATE, master);

        printf("TEST: add master conntrack ");
        if (ret == -1)
                printf("(%d)(%s)\n", ret, strerror(errno));
        else
                printf("(OK)\n");

        nfct_close(h);

        expected = nfct_new();
        if (!expected) {
                perror("nfct_new");
                exit(EXIT_FAILURE);
        }

        nfct_set_attr_u8(expected, ATTR_L3PROTO, AF_INET);
        nfct_set_attr_u32(expected, ATTR_IPV4_SRC, inet_addr("1.1.1.1"));
        nfct_set_attr_u32(expected, ATTR_IPV4_DST, inet_addr("2.2.2.2"));

        nfct_set_attr_u8(expected, ATTR_L4PROTO, IPPROTO_TCP);
        nfct_set_attr_u16(expected, ATTR_PORT_SRC, 0);
        nfct_set_attr_u16(expected, ATTR_PORT_DST, htons(10241));

        mask = nfct_new();
        if (!mask) {
                perror("nfct_new");
                exit(EXIT_FAILURE);
        }

        nfct_set_attr_u8(mask, ATTR_L3PROTO, AF_INET);
        nfct_set_attr_u32(mask, ATTR_IPV4_SRC, 0xffffffff);
        nfct_set_attr_u32(mask, ATTR_IPV4_DST, 0xffffffff);

        nfct_set_attr_u8(mask, ATTR_L4PROTO, IPPROTO_TCP);
        nfct_set_attr_u16(mask, ATTR_PORT_SRC, 0x0000);
        nfct_set_attr_u16(mask, ATTR_PORT_DST, 0xffff);

        /*
         * Step 2: Setup expectation
         */

        exp = nfexp_new();
        if (!exp) {
                perror("nfexp_new");
                exit(EXIT_FAILURE);
        }

        nfexp_set_attr(exp, ATTR_EXP_MASTER, master);
        nfexp_set_attr(exp, ATTR_EXP_EXPECTED, expected);
        nfexp_set_attr(exp, ATTR_EXP_MASK, mask);
        nfexp_set_attr_u32(exp, ATTR_EXP_TIMEOUT, 200);

        nfct_destroy(master);
        nfct_destroy(expected);
        nfct_destroy(mask);

        h = nfct_open(EXPECT, 0);
        if (!h) {
                perror("nfct_open");
                return -1;
        }

        ret = nfexp_query(h, NFCT_Q_CREATE, exp);

        printf("TEST: create expectation ");
        if (ret == -1)
                printf("(%d)(%s)\n", ret, strerror(errno));
        else
                printf("(OK)\n");

        nfct_close(h);

        ret == -1 ? exit(EXIT_FAILURE) : exit(EXIT_SUCCESS);
}