/*
    A portforwarding program
    Copyright (C) 2004  Kasper Dupont

    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
    with permission from the author 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
*/

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <string.h>

#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <linux/if.h>
#include <linux/if_tun.h>

#include <sys/time.h>
#include <time.h>
#include <errno.h>
#include <dirent.h>
#include <unistd.h>

#include <netdb.h>

#include <pwd.h>
#include <sys/types.h>
#include <grp.h>

#include <sys/wait.h>
#include <arpa/inet.h>

#define PORTNUMBER 7197
#define TARGETPORT 21877

#define ASSTRING2(_) #_
#define ASSTRING(_) ASSTRING2(_)

static inline void errstop(const char *s)
{
  perror(s);
  exit(1);
}

void forward(int src_fd,int dst_fd)
{
  char buf[4096];
  int r;

  fprintf(stderr,"%d => %d\n",src_fd,dst_fd);

  switch(fork()) {
  case 0:
    break;
  case -1:
    errstop("fork()");
  default:
    return;
  }

  dup2(src_fd,0);
  dup2(dst_fd,1);
  close(src_fd);
  close(dst_fd);

  while ((r=read(0,buf,4096))>0) {
    int i=0,w;
    while (i<r) {
      w=write(1,buf+i,r-i);
      if (w<0) {
	shutdown(0,SHUT_RD);
	_exit(1);
      }
      i+=w;
    }
  }
  shutdown(1,SHUT_WR);
  _exit(0);
}

int main()
{
  uint8_t addrbuf[512];
  socklen_t addrbuflen=255;
  int sock_fd;
  struct sockaddr_in sa;
  int log_fd=open("wrapper.log",O_CREAT|O_WRONLY|O_APPEND,0666);
  int yes=1;

  sock_fd=socket(PF_INET,SOCK_STREAM,0);
  if (sock_fd == -1) errstop("scoket");

  if (setsockopt(sock_fd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(yes)))
    errstop("SO_REUSEADDR");

  sa.sin_family = AF_INET;
  sa.sin_port = htons(PORTNUMBER);
  sa.sin_addr.s_addr=0;
  if (bind(sock_fd,(struct sockaddr*)&sa,sizeof(sa))) errstop("bind");
  if (listen(sock_fd,5)) errstop("listen");

  daemon(0,0);

  dup2(log_fd,2);
  close(log_fd);

  while(1) {
    int client_fd=accept(sock_fd,(struct sockaddr*)(addrbuf+256),&addrbuflen);
    pid_t childpid=fork();
    
    switch(childpid) {
    case 0:
      close(sock_fd);
      sock_fd=socket(PF_INET,SOCK_STREAM,0);

      sa.sin_family = AF_INET;
      sa.sin_port = htons(TARGETPORT);
      sa.sin_addr.s_addr=inet_addr("127.0.0.1");

      if (connect(sock_fd,(struct sockaddr*)&sa,sizeof(sa)))
	errstop("connect(127.0.0.1:" ASSTRING(TARGETPORT) ")");
      
      addrbuf[255]=addrbuflen;
      write(sock_fd,addrbuf+255,addrbuflen+1);
      forward(sock_fd,client_fd);
      forward(client_fd,sock_fd);
      fprintf(stderr,"Running\n");
      _exit(0);
    case -1:
      errstop("fork");
    default:
      close(client_fd);
      waitpid(childpid,NULL,0);
    }
  }

  return 0;
}