Multiple SSH Tunnels

ssh.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <signal.h>
#include <fcntl.h>
#include <netdb.h>
#define PORT 7070
#define ADDRESS "127.0.0.1"
#define RPORT 7071
#define THREAD 4
#define RADDR "127.0.0.1"
#define MAXDATA 1024
#define MAXCLIENT 255
#define LOG 0
#define ERRLOG 1
#define SELLOG 0
int INDEX = -1;
#define MSG_NOSIGNAL 0
void xsocket(int *_listen_fd){
	int on = 1;
	errno = 0;
	if((*_listen_fd=socket(AF_INET, SOCK_STREAM, 0)) >= 0){
		if(LOG) {perror("#10000.socket\t");}
	}
	else{
		if(ERRLOG) {perror("#10001.socket\t");}
		//exit(1);
	}
	errno = 0;
	if(setsockopt(*_listen_fd, SOL_SOCKET, SO_REUSEADDR, (int *) &on, sizeof(on)) >= 0){
		if(LOG) {perror("#10020.setopt\t");}
	}
	else{
		if(ERRLOG) {perror("#10021.setopt\t");}
	}
	return;
}

void xbzero(struct sockaddr_in *_saddr){
	bzero(((char *) _saddr), sizeof(*_saddr));
	return;
}

void xbind(int *_listen_fd, struct sockaddr_in *_saddr, int *len){
	_saddr->sin_family = PF_INET;
	_saddr->sin_addr.s_addr = inet_addr(ADDRESS);
	_saddr->sin_port = htons(PORT);
	errno = 0;
	if(bind(*_listen_fd, (struct sockaddr *)_saddr, *len) >= 0){
		if(LOG) {perror("#10100.bind\t");}
	}
	else{
		if(ERRLOG) {perror("#10101.bind\t");}
		//exit(1);
	}
	return;
}

void xlisten(int *_listen_fd){
	errno = 0;
	if(listen(*_listen_fd, MAXCLIENT) >= 0){
		if(LOG) {perror("#10200.listen\t");}
	}
	else{
		if(ERRLOG) {perror("#10201.listen\t");}
		exit(1);
	}
	printf("start listening port %d\n", PORT);
	return;
}

int xaccept(int *_listen_fd, struct sockaddr_in *_caddr, int *_len){
	int conn_fd;
	if((conn_fd = accept(*_listen_fd, (struct sockaddr *) _caddr, (socklen_t *__restrict) _len)) >= 0){
		if(LOG) {perror("#10300.accept\t");}
	}
	else{
		if(ERRLOG) {perror("#10301.accept\t");}
	}
	return conn_fd;
}

void xgetaddrinfo(char *_name, int _port, struct addrinfo **_addr){
	char port[10];
	sprintf(port, "%d", _port);
	errno = 0;
	if(getaddrinfo(_name, port, NULL, _addr) >= 0){
		if(LOG) {perror("#11000.getaddr\t");}
	}
	else{
		if(ERRLOG) {perror("#11001.getaddr\t");}
		exit(1);
	}
	return;
}

int xconnect(int *_conn_fd, struct addrinfo *_addr){
	int ret = 0;
	errno = 0;
	if(connect(*_conn_fd, _addr->ai_addr, _addr->ai_addrlen) >= 0){
		if(LOG) {perror("#11100.connect\t");}
	}
	else{
		if(ERRLOG) {perror("#11101.connect\t");}
		ret = -1;
	}
	return ret;
}

int max(int x, int y){
	if(x >= y){
		return x;
	}
	else{
		return y;
	}
}

void dclose(int *fd, int *rfd, int i){
	close(fd[i]);
	close(rfd[i]);
	fd[i] = -1;
	rfd[i] = -1;
	return;
}

int main(int argc, char **argv){
	struct sockaddr_in saddr;
	struct sockaddr_in caddr;
	int listen_fd;
	int len = sizeof(struct sockaddr_in);
	int rsize;
	char buf[MAXDATA];
	int i;
	int ret;
	int fd[MAXCLIENT];
	int rfd[MAXCLIENT];
	int nfds = 0;
	struct addrinfo *addr[THREAD];
	fd_set rd;
	FD_ZERO(&rd);
	for(i = 0;i < MAXCLIENT;i++){
		fd[i] = -1;
		rfd[i] = -1;
	}
	for(i = 0;i < THREAD;i++){
		xgetaddrinfo(RADDR, RPORT+i, &addr[i]);
	}
	signal(SIGPIPE, SIG_IGN);
	xsocket(&listen_fd);
	xbzero(&saddr);
	xbzero(&caddr);
	xbind(&listen_fd, &saddr, &len);
	xlisten(&listen_fd);
	while(1){
		if(SELLOG){printf("loop start\n");}
		FD_ZERO(&rd);
		FD_SET(listen_fd, &rd);
		for(i = 0; i < MAXCLIENT; i++){
			if(fd[i] >= 0){
				FD_SET(fd[i], &rd);
			}
			if(rfd[i] >= 0){
				FD_SET(rfd[i], &rd);
			}
		}
		nfds = max(nfds, listen_fd);
		ret = select(nfds+1, &rd, NULL, NULL, NULL);
		if(SELLOG){printf("select return\n");}
		if(ret < 0){
			if (errno == EINTR){ //EINTR = 4
				continue;
			}
			else{
				if(ERRLOG){printf("begin select failure\n");}
			}
		}
		if(FD_ISSET(listen_fd ,&rd)){
			if(SELLOG){printf("start accept\n");}
			for(i = 0; i < MAXCLIENT; i++){
				if(fd[i] < 0){
					fd[i] = xaccept(&listen_fd, &caddr, &len);
					if(fd[i] < 0){
						if(ERRLOG){printf("accept a new connection failure\n");}
					}
					else{
						if(++INDEX >= THREAD){
							INDEX = 0;
						}
						if(SELLOG){printf("%d\n",RPORT+INDEX);}
						xsocket(&(rfd[i]));
						if(xconnect(&(rfd[i]), addr[INDEX]) < 0){
							if(ERRLOG){printf("connect remote server error\n");}
							dclose(fd, rfd, i);
						}
						else{
							if(SELLOG){printf("connect remote server finish\n");}
						}
					}
					if (fd[i] > nfds){
						nfds = fd[i];
					}
					if (rfd[i] > nfds){
						nfds = rfd[i];
					}
					break;
				}
			}
			continue;
		}
		for(i = 0; i < MAXCLIENT; i++){
			if(fd[i] < 0){
				continue;
			}
			if(FD_ISSET(fd[i], &rd)){
				bzero(&buf, sizeof(buf));
				errno = 0;
				if(SELLOG){printf("recv data form local\n");}
				rsize = recv(fd[i], buf, MAXDATA, MSG_NOSIGNAL);
				if(rsize < 0){
					if(SELLOG){perror("#50001.recv error");}
					dclose(fd, rfd, i);
					continue;
				}
				else if(rsize ==0){
					if(SELLOG){printf("local connection closed\n");}
					dclose(fd, rfd, i);
					continue;
				}
				else{
					if(SELLOG){printf("send data to remote server\n");}
					if(send(rfd[i], buf, rsize, MSG_NOSIGNAL) < 0){
						if(SELLOG){printf("send data to remote server error\n");}
						dclose(fd, rfd, i);
						continue;
					}
				}
			}
			if(FD_ISSET(rfd[i], &rd)){
				bzero(&buf, sizeof(buf));
				errno = 0;
				if(SELLOG){printf("recv data form remote server\n");}
				rsize = recv(rfd[i], buf, MAXDATA, MSG_NOSIGNAL);
				if(rsize < 0){
					if(SELLOG){perror("#50001.recv error");}
					dclose(fd, rfd, i);
					continue;
				}
				else if(rsize ==0){
					if(SELLOG){printf("remote connection closed\n");}
					dclose(fd, rfd, i);
					continue;
				}
				else{
					if(SELLOG){printf("send data to local\n");}
					if(send(fd[i], buf, rsize, MSG_NOSIGNAL) < 0){
						if(SELLOG){printf("send data to local error\n");}
						dclose(fd, rfd, i);
						continue;
					}
				}
			}
		}
	}
	return 0;
}