old.c

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

#include <libmnl/libmnl.h>
#include <linux/netfilter.h>
#include <linux/netfilter/nfnetlink.h>

#include <linux/types.h>
#include <linux/netfilter/nfnetlink_queue.h>

#include <libnetfilter_queue/libnetfilter_queue.h>

static struct mnl_socket *nl;

static struct nlmsghdr *
nfq_build_header(char *buf, int type, uint32_t queue_num)
{
        struct nlmsghdr *nlh = mnl_nlmsg_put_header(buf);
        nlh->nlmsg_type = (NFNL_SUBSYS_QUEUE << 8) | type;
        nlh->nlmsg_flags = NLM_F_REQUEST;

        struct nfgenmsg *nfg = mnl_nlmsg_put_extra_header(nlh, sizeof(*nfg));
        nfg->nfgen_family = AF_UNSPEC;
        nfg->version = NFNETLINK_V0;
        nfg->res_id = htons(queue_num);

        return nlh;
}

static int
nfq_send_verdict(int queue_num, uint32_t id, uint8_t *pkt, uint16_t pktlen)
{
        char buf[MNL_SOCKET_BUFFER_SIZE];
        struct nlmsghdr *nlh;
        int ret;

        nlh = nfq_build_header(buf, NFQNL_MSG_VERDICT, queue_num);
        nfq_nlmsg_verdict_build(nlh, id, NF_ACCEPT);
        nfq_nlmsg_verdict_payload(nlh, pkt, pktlen);

        if (mnl_socket_sendto(nl, nlh, nlh->nlmsg_len) < 0) {
                perror("mnl_socket_send");
                exit(EXIT_FAILURE);
        }

        return ret;
}

static int queue_cb(const struct nlmsghdr *nlh, void *data)
{
        struct nfqnl_msg_packet_hdr *ph = NULL;
        struct nlattr *attr[NFQA_MAX+1];
        uint32_t id = 0;
        struct nfgenmsg *nfg;
        uint8_t *pkt;
        uint16_t pktlen;

        if (nfq_nlmsg_parse(nlh, attr) < 0) {
                perror("problems parsing");
                return MNL_CB_ERROR;
        }

        nfg = mnl_nlmsg_get_payload(nlh);

        ph = (struct nfqnl_msg_packet_hdr *)
                mnl_attr_get_payload(attr[NFQA_PACKET_HDR]);
        if (ph == NULL) {
                perror("problems retrieving metaheader");
                return MNL_CB_ERROR;
        }

        id = ntohl(ph->packet_id);

        printf("packet received (id=%u hw=0x%04x hook=%u)\n",
                id, ntohs(ph->hw_protocol), ph->hook);

        pkt = mnl_attr_get_payload(attr[NFQA_PAYLOAD]);
        pktlen = mnl_attr_get_payload_len(attr[NFQA_PAYLOAD]);

        nfq_send_verdict(ntohs(nfg->res_id), id, pkt, pktlen);

        return MNL_CB_OK;
}

int main(int argc, char *argv[])
{
        char buf[MNL_SOCKET_BUFFER_SIZE];
        struct nlmsghdr *nlh;
        int ret;
        unsigned int portid, queue_num;

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

        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);
        }
        portid = mnl_socket_get_portid(nl);

        nlh = nfq_build_header(buf, NFQNL_MSG_CONFIG, 0);
        nfq_nlmsg_cfg_build_request(nlh, AF_INET, NFQNL_CFG_CMD_PF_UNBIND);

        if (mnl_socket_sendto(nl, nlh, nlh->nlmsg_len) < 0) {
                perror("mnl_socket_send");
                exit(EXIT_FAILURE);
        }

        nlh = nfq_build_header(buf, NFQNL_MSG_CONFIG, 0);
        nfq_nlmsg_cfg_build_request(nlh, AF_INET, NFQNL_CFG_CMD_PF_BIND);

        if (mnl_socket_sendto(nl, nlh, nlh->nlmsg_len) < 0) {
                perror("mnl_socket_send");
                exit(EXIT_FAILURE);
        }

        nlh = nfq_build_header(buf, NFQNL_MSG_CONFIG, queue_num);
        nfq_nlmsg_cfg_build_request(nlh, AF_INET, NFQNL_CFG_CMD_BIND);

        if (mnl_socket_sendto(nl, nlh, nlh->nlmsg_len) < 0) {
                perror("mnl_socket_send");
                exit(EXIT_FAILURE);
        }

        nlh = nfq_build_header(buf, NFQNL_MSG_CONFIG, queue_num);
        nfq_nlmsg_cfg_add_copy(nlh, NFQNL_COPY_PACKET, 0xffff);

        if (mnl_socket_sendto(nl, nlh, nlh->nlmsg_len) < 0) {
                perror("mnl_socket_send");
                exit(EXIT_FAILURE);
        }

        ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
        if (ret == -1) {
                perror("mnl_socket_recvfrom");
                exit(EXIT_FAILURE);
        }
        while (ret > 0) {
                uint32_t id;

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

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

        mnl_socket_close(nl);

        return 0;
}