#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <ctype.h>
#include <time.h>
#include <errno.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/uio.h>
#include <asm/types.h>
#include <linux/if.h>
#include <linux/netlink.h>
#include <linux/netfilter_ipv4/ip_nat.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv4/ip_conntrack.h>
#include <linux/netfilter_ipv4/ip_conntrack_tcp.h>
#include <linux/netfilter_ipv4/ip_conntrack_ftp.h>
#include <linux/netfilter_ipv4/ip_conntrack_icmp.h>
#include <linux/netfilter_ipv4/ip_conntrack_tuple.h>
#include <linux/nfnetlink_conntrack.h>

#include "libctnetlink.h"

#define NETLINK_SOCKBUFSZ	1<<20

int accept_msg(struct sockaddr_nl *who, struct nlmsghdr *n, void *arg)
{
	int udp_sock = *(int *)arg;

	if (send(udp_sock, n, n->nlmsg_len, 0) < 0)
		perror("send\n");

	return 0;
}

int main(int argc, char **argv)
{
	struct nfnl_handle nlh;
	struct sockaddr_in sin;
	int sock_buf_size = NETLINK_SOCKBUFSZ;
	int udp_sock;

	if (argc < 2) {
		fprintf(stderr, "Usage: %s [ <ip> | listen ]\n", argv[0]);
		exit(1);
	}

	if (nfnl_open(&nlh, NFNL_SUBSYS_CTNETLINK, ~NFGRP_IPV4_CT_UDP)) {
		perror("nfnl_open\n");
		exit(1);
	}

	if ((udp_sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0) {
		perror("socket\n");
		exit(1);
	}

	sin.sin_family = AF_INET;
	sin.sin_port = htons(10000);

	if (strncmp(argv[1], "listen", sizeof("listen")) == 0) {
		char buf[4000];
		struct nlmsghdr *n = (struct nlmsghdr *)buf;
		int len;
		
		sin.sin_addr.s_addr = 0;
		if (bind(udp_sock, (struct sockaddr *)&sin, sizeof(sin)) < 0) {
			perror("bind\n");
			exit(1);
		}

		while ((len = recv(udp_sock, &buf, sizeof(buf), 0))) {
			n->nlmsg_flags = NLM_F_REQUEST|NLM_F_CREATE|NLM_F_EXCL;
			if (nfnl_send(&nlh, n) < 0)
				perror("nfnl_send\n");
		}
		exit(0);
	}

	if (setsockopt(nlh.fd, SOL_SOCKET, SO_RCVBUF,
	               (const char *)&sock_buf_size, sizeof(int)) < 0) {
		perror("setsockopt\n");
		exit(1);
	}

	inet_aton(argv[1],&sin.sin_addr.s_addr);

	if (connect(udp_sock, (struct sockaddr *)&sin, sizeof(sin)) < 0) {
		perror("connect\n");
		exit(1);
	}

	if (nfnl_listen(&nlh, accept_msg, &udp_sock) < 0) {
		perror("nfnl_listen\n");
		exit(1);
	}
}