/*******************************************************************************This program is free software; you can redistribute it and/or modifyit under the terms of the GNU General Public License as published bythe Free Software Foundation; either version 2 of the License, or(at your option) any later version.This program is distributed in the hope that it will be useful,but WITHOUT ANY WARRANTY; without even the implied warranty ofMERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See theGNU General Public License for more details.You should have received a copy of the GNU General Public Licensealong with this program; if not, write to the Free SoftwareFoundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA*******************************************************************************//*******************************************************************************Program: sp.cDescription: a smart proxyAuthor: Alan Chen (ariesram@may10.ca)Date: July 18, 2001*******************************************************************************/
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/wait.h>
#include <unistd.h>
#include <netinet/in.h>
#define ERRLOG "./sp.log"
int do_proxy(int infd, char* addr, int port);
int max(int i, int j);
void waitchild(int);
void version();
void usage();
void daemonize();
void p_error(const char * err_msg);
int main(int argc, char** argv) 
{
	struct sockaddr_in servaddr, clientaddr;
	int listenfd, connfd;
	int clientlen;pid_t chpid;
	int service_port = 0, remote_port = 0;
	char remote_addr[17];
	const char optstring[] = "s:r:p:vh";
	int opt;
	extern char *optarg;
	extern int optind, opterr, optopt;
	extern FILE *stderr;
	memset(remote_addr, 0, 17);
	if( argc == 2 ) 
		{while( (opt = getopt(argc, argv, optstring)) != -1 ) 
			{
				if( opt == 'v' ) {version();exit(0);}
				else if ( opt == 'h' ) {usage();exit(0);}
					else {printf("type sp -h for help message");usage();exit(0);}}}
						else {while( (opt = getopt(argc, argv, optstring)) != -1 ) 
							{switch(opt) {
								case 's':service_port = atoi(optarg);break;
								case 'r':memcpy(remote_addr, optarg, strlen(optarg));remote_addr[strlen(remote_addr)] = '';break;
								case 'p':remote_port = atoi(optarg);break;default:usage();exit(0);}}}
						if( service_port == 0' 'remote_port == 0' 'remote_addr[0] == '') {usage();exit(0);}
			daemonize();
			bzero(&servaddr, sizeof(servaddr));
			servaddr.sin_family = AF_INET;
			servaddr.sin_port = htons(service_port);
			servaddr.sin_addr.s_addr = INADDR_ANY;
			listenfd = socket(AF_INET, SOCK_STREAM, 0);
			if(listenfd < 0) {p_error("socket error");exit(-1);}
			if( bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) < 0 ) {p_error("bind error");exit(-1);}
			if( listen(listenfd, 5) < 0 ) {p_error("listen error");exit(-1);}
			signal(SIGCHLD, waitchild);
			for(;;) 
			{
				connfd = accept( listenfd, (struct sockaddr *)&clientaddr,&clientlen );
				if( connfd < 0 ) {p_error("accept error");exit(-1);}
				if( (chpid = fork()) == -1 ) {p_error("fork error");exit(-1);}
				if( chpid == 0 ) {close(listenfd);do_proxy(connfd, remote_addr, remote_port);exit(0);}
				if( chpid > 0 ) {close(connfd);}
			}
			exit(0);
}
int do_proxy(int infd, char *addr, int port) 
		{
			struct sockaddr_in rout;
			int outfd;int maxfd;
			int count = 65535;
			int n;
			fd_set set;
			char buf[count];
			bzero(&rout, sizeof(rout));
			rout.sin_family = AF_INET;
			rout.sin_port = htons(port);
			rout.sin_addr.s_addr = inet_addr(addr);
			if( (outfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) 
				{p_error("socket error");exit(-1);}
			if( connect(outfd, (struct sockaddr *)&rout, sizeof(rout)) < 0 ) {p_error("connect error");exit(-1);}
			while(1) 
			{
				FD_ZERO(&set);
				FD_SET(infd, &set);
				FD_SET(outfd, &set);
				maxfd = max(outfd, infd);
				if( select(maxfd   1, &set, NULL, NULL, NULL) < 0 ) {perror("select error:");exit(-1);}
				if( FD_ISSET(infd, &set) ) 
					{n = read(infd, (void *)buf, count);
						if( n <= 0)break;
						if( write(outfd, (const void *)buf, n) != n ) {p_error("write error");continue;}}
						if( FD_ISSET(outfd, &set) ) {n = read(outfd, (void *)buf, count);
							if( n <= 0)break;
							if( write(infd, (const void *)buf, n) != n ) {p_error("write error");continue;}
								}
			}
			close(infd);
			close(outfd);
}
int max(int i, int j) 
{
	return i>j?i:j;
}
void waitchild(int signo) 
{
	int status;
	pid_t childpid;
	if( (childpid = waitpid(-1, &status, WNOHANG)) < 0 ) {p_error("wait error");exit(1);}return;
}
void version() 
{
	printf("GNU SP 1.0Copyright 2001 Aryes Software Studio, Inc.SP is free software, covered by the GNU General Public License, and you arewelcome to change it and/or distribute copies of it under certain conditions.");
}
void usage() 
{
	printf("This is the GNU smart proxy daemon. Usage:sp -s service_port -r remote_address -p remote_portsp -vsp -hoption:-s specify service port of sp-r specify remote address which sp will connect-p specify remote port while sp will connect to-v display version message-h display this help messageReport bugs to <ariesram@may10.ca>.");
}
void daemonize() 
{
	int i;
	#ifndef _DEBUGsignal(SIGINT, SIG_IGN);
	#endifsignal(SIGHUP, SIG_IGN);
	signal(SIGABRT, SIG_IGN);
	signal(SIGSTOP, SIG_IGN);
	signal(SIGCHLD, SIG_IGN);
	#ifndef _DEBUG
	if (fork() != 0)exit(0);
		setsid();
		for (i = 256; i >= 0; i --)
		#endif
		#ifdef _DEBUG
		for (i = 256; i >= 3; i --)
		#endif
		close(i);
}
void p_error(const char * err_msg)
{
	FILE * fp;
	#ifdef _DEBUGprintf("%s", err_msg);
	#endif
	fp = fopen(ERRLOG, "a");
	if (fp == NULL)return;
	fprintf(fp, "%s", err_msg);
	fclose(fp);
}