client.cpp

#include <fcntl.h>  /* O_RDWR */
#include <string.h> /* memset(), memcpy() */
#include <stdio.h> /* perror(), printf(), fprintf() */
#include <stdlib.h> /* exit(), malloc(), free() */
#include <unistd.h> /* read(), close() */
#include <sys/select.h> /* select() */

/* cxx */
#include <iostream>

using namespace std;

/* 3rd party libs */
#include "socketwrapper.h"
#include <tins/tins.h>

using namespace Tins;

char remote_ip[16] = ""; 

void process_arguments(int argc, char **argv) {
	bool argMissing = true;
	int opt;
	
	while (~(opt = getopt(argc, argv, "hHs:S:"))) { 
		switch(opt) {
			case 's': case 'S':
				if (optarg) {
					strncpy(remote_ip,optarg,15);
					argMissing = false;
				} else {
					fputs("?\n", stdout);
					exit(0);
				}
				break;
			case 'h': case 'H':
				fputs("?\n", stdout);
				exit(0);
				//break;
		}
	}

	if (argMissing) {
		fputs("?\n", stdout);
		exit(0);
	}
} 

int main(int argc, char *argv[])
{
	int socketfd, tunfd, nbytes;
	char buf[1600];

	process_arguments(argc, argv);

	// dgram
	struct sockaddr_in srvaddr;
	socketfd = Socket(AF_INET, SOCK_DGRAM/* | SOCK_NONBLOCK*/, 0);
	bzero(&srvaddr, sizeof(srvaddr));
	srvaddr.sin_family = AF_INET;
	srvaddr.sin_port = htons(SERV_PORT);
	inet_pton(AF_INET, remote_ip, &srvaddr.sin_addr);

	// tun
	tunfd = tun_open("clienttun");
	system("route add 123.123.123.123 clienttun");

	fputs("Client now running in UDP mode.\n", stdout);

	int maxfd = (socketfd > tunfd) ? socketfd : tunfd;

	while(1) {

		fd_set rd_set;
		
		FD_ZERO(&rd_set);
		FD_SET(tunfd, &rd_set); FD_SET(socketfd, &rd_set);

		int ret = select(maxfd + 1, &rd_set, NULL, NULL, NULL);
		if (ret < 0 && errno == EINTR) continue;
		if (ret < 0) {
			perror("select()"); exit(1);
		}

		if(FD_ISSET(tunfd, &rd_set)) {
			nbytes = read(tunfd, buf, sizeof(buf));
			printf("Read %d bytes from clienttun\n", nbytes);
			//hex_dump(buf, nbytes);
			RawPDU p((uint8_t *)buf, nbytes);
			try {
				IP ip(p.to<IP>());
				cout << "IP Packet: " << ip.src_addr() << " -> " << ip.dst_addr() << std::endl;
				sendto(socketfd, buf, nbytes, 0, (sockaddr*)&srvaddr, sizeof(srvaddr));
			} catch (...) {
				continue;
			}
		}

		if(FD_ISSET(socketfd, &rd_set)) { 
			int size84 = recvfrom(socketfd, buf, 1600, 0, NULL, NULL);
			printf("Recv %d bytes from udp socket\n", nbytes);
			write(tunfd, buf, size84);
		}
	}
	return 0;
}