sp.c

linux下网络编程的函数

/*******************************************************************************
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the 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 of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*******************************************************************************/
/*******************************************************************************
Program: sp.c
Description: a smart proxy 
Author: Alan Chen ([e-mail])
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)] = '\0';
break;
case 'p':
remote_port = atoi(optarg);
break;
default:
usage();
exit(0);
}
}
}
if( service_port == 0&&remote_port == 0&&remote_addr[0] == '\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 1.0 Copyright 2001 Aryes Software Studio, Inc. SP is free software, covered by the GNU General Public License, and you are welcome 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_port sp -v  sp -h option: -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 message Report bugs to . ");
}

void daemonize() {
int i;
#ifndef _DEBUG
signal(SIGINT, SIG_IGN); 
#endif
signal(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 _DEBUG
printf("%s ", err_msg);
#endif

fp = fopen(ERRLOG, "a");
if (fp == NULL)
return;
fprintf(fp, "%s ", err_msg);
fclose(fp);
}