/* IP/tcp_port Redirector
 * Redirect data from source A to dest C via B (this host),
 * thus overiding routing path in application layer.
 * This works like a proxy www server, but it works for
 * any port/application (w/o proxy cache of course)
 * I made this for J. Deliyannis who's connection with USA is
 * slow, thus by using this program he can connect to USA through greece
 * and have a fast connection ;-)
 * Ioannou Spiros Nov '97
 *
 * Program tested under sunos 5.x 
 * Can support MAXCHILDS connections to the same host simultaneously.
 * forks a new process for every connection.
 *
 * Change MAXCHILDS as you wish.
 */

#define  MAXCHILDS 10

#include <sys/types.h>
#include <sys/time.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <poll.h>
#include <stropts.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <signal.h>
#include <stdio.h>

/* TODO list
   
   -Add child forking
   Done

   -Add capability to change DestHost via network
    without restarting daemon 

*/

 void childhdl();
 char buffer[100000];
 int lsd, a, b, i,Asd,Csd,len,we_full,we_child,cdown;
 int reconfigurable,Confsd,rConfsd;
 char desthost[64],destport[10];

 struct sockaddr_in sa, sc,sconf;
 unsigned char in[2];
 struct timeval tval;
 struct hostent *chost;
 fd_set inout_fds;

main (int argc, char *argv[])
{
  int  one=1;

  Asd=-1;
  Csd=-1;
  Confsd=-1;
  we_full=0;
  we_child=0;
  reconfigurable=0;
  cdown=1;


  if (argc != 4) {
	printf ("Usage: ipredirect localport desthost destport\n\tor\n");
	printf ("Usage: ipredirect localport  \"rec\"   confport\n\n");
	exit (-1);
  }
  else if (!strcmp(argv[2],"rec")) reconfigurable=1;
  else reconfigurable=0;
 

  if (reconfigurable) {
      printf("\nRunning in reconfigurable mode, connect to \n");
      printf("confport %d to specify new destination address\n",atoi(argv[3]));
  }


  signal(SIGCHLD,childhdl);
  

  if (reconfigurable) {

    if ((Confsd = socket (AF_INET, SOCK_STREAM, 0)) < 0) {
	    perror ("conf:socket");
	    exit (1);
      }
      setsockopt(Confsd,SOL_SOCKET,SO_REUSEADDR,(char *)&one,sizeof(one));
      sconf.sin_family = AF_INET;
      sconf.sin_port = htons ((u_short) atoi (argv[3]));
      sconf.sin_addr.s_addr = htonl (INADDR_ANY);

      if (bind (Confsd, (struct sockaddr *) &sconf, sizeof (sconf)) < 0) {
	    perror ("conf:bind");
	    exit (2);
      }

      if (listen (Confsd, 1) < 0) {
	    perror ("conf:listen");
	    exit (3);
      }
      len = sizeof (sconf);
      printf ("\nConfiguration port ready ... awaiting for connection\n");


  }
  else {

      strcpy(desthost,argv[2]);
      strcpy(destport,argv[3]);
  }


 if (reconfigurable)
  if ((rConfsd = accept (Confsd, (struct sockaddr *) &sconf, &len)) < 0) {
	perror ("rConfsd:accept");
	exit(4);
  }
  else {
      strcpy(buffer,"\nWelcome to ipredirector\n-----------------------\n");
      strcat(buffer,"Please specify a destination host after each prompt in\n");
      strcat(buffer,"the form : host port\nType help for help, or exit to quit\n\n");
      strcat(buffer,"Destination > ");
      write (rConfsd,buffer,strlen(buffer));
      newdest();
  }


  /*Open  the "A"  socket*/

  if ((lsd = socket (AF_INET, SOCK_STREAM, 0)) < 0) {
	perror ("socket");
	exit (1);
  }
  setsockopt(lsd,SOL_SOCKET,SO_REUSEADDR,(char *)&one,sizeof(one));
  sa.sin_family = AF_INET;
  sa.sin_port = htons ((u_short) atoi (argv[1]));
  sa.sin_addr.s_addr = htonl (INADDR_ANY);

  if (bind (lsd, (struct sockaddr *) &sa, sizeof (sa)) < 0) {
	perror ("bind");
	exit (2);
  }

  if (listen (lsd, 10) < 0) {
	perror ("listen");
	exit (4);
  }
  len = sizeof (sa);
  strcpy (buffer, "");
  printf ("daemon ready ...\n");


 while (1) {
	fflush (stdout);
	tval.tv_sec = 0;
	tval.tv_usec = 0; /*50 microseconds*/

startselect:

	FD_ZERO (&inout_fds); /*Initialize file descriptors for select*/

	/* Prepare for input from host A */
	  if (we_child && Asd > 0)
		FD_SET (Asd, &inout_fds);

	/* Prepare for input from host C */
	  if (we_child && Csd > 0)
		FD_SET (Csd, &inout_fds);


	/* Prepare to accept a connection to our socket */

	if (!we_child) 
	    FD_SET (lsd, &inout_fds);

	if (!we_child && reconfigurable) 
	    FD_SET (rConfsd,&inout_fds);


#ifdef TESTING
	printf("\nbefore select.. child:%d ",we_child);
#endif
	/* Do a non-timeout select (interupt driven) to minimize load*/
	do {
	     i = select (64, &inout_fds, (fd_set *) 0, (fd_set *) 0, 
				    (struct timeval *)0/*&tval*/ );
#ifdef TESTING
	     if (i==EINTR) printf("Select probably interrupted by SIGCHLD signal\n");
#endif
	} while(i==EINTR||i<0);
#ifdef TESTING
    printf("after select=%d..child:%d\n",i,we_child);
#endif

        if (FD_ISSET (rConfsd,&inout_fds)) {
	    newdest();
	    printf("New destination is: %s %s\n",desthost,destport);
	}

	/*We are server, and full,and a new connection*/

	if (FD_ISSET (lsd, &inout_fds) && we_full>=MAXCHILDS && !we_child) {
	  if ((Asd = accept (lsd, (struct sockaddr *) &sa, &len)) < 0) {
		perror ("accept");
	  }
	  else {
		/*deny connection*/
#ifdef TESTING
		printf ("\nRejected new connection -- server full,%d\n", Asd);
		printf ("Family=:%d , port=%d address: %s\n",
		sa.sin_family, ntohs (sa.sin_port), inet_ntoa (sa.sin_addr));
#endif
		strcpy (buffer, "\nServer full, sorry ;-).\n");
		write (Asd, buffer, sizeof (buffer));
		shutdown(Asd,2);
		close(Asd);
		Asd=-1;
	  }
	}
	/*A new connection, ...*/
	else if (FD_ISSET (lsd, &inout_fds) && we_full<MAXCHILDS  && !we_child) {

	  if (!fork()) {

	    we_child=1;
	    we_full=0;
	    if ((Asd = accept (lsd, (struct sockaddr *) &sa, &len)) < 0) {
		perror ("child accept Asd");
		exit(6);
	    }
	    printf("GOT HERE,dh:%s,dp:%s\n",desthost,destport);
	    printf ("A new connection from address: %s port=%d \n",
		     inet_ntoa (sa.sin_addr),ntohs (sa.sin_port));
	    close(lsd);
#ifdef ALLTESTING
	    strcpy (buffer, "\nServer welcomes you.\n");
	    write (Asd, buffer, sizeof (buffer));
#endif
	    connectC(desthost,destport);
	    goto startselect;
	  }
	  else we_full++;
	}

	  /* transfer data from A to C*/
	if (we_child && Asd > 0 && FD_ISSET (Asd, &inout_fds)) {
		  bzero (buffer, sizeof (buffer));

		  /* read data from A */
		  b = read (Asd, buffer, sizeof (buffer));	
#ifdef ALLTESTING
		  printf ("buffer read from A is:#%s#=%d bytes\n", 
			   buffer, b);
#endif
		  /*If read failed : A closed connection*/
		  if (b <= 0) {
			/*Free A for a new connection */

			shutdown (Asd, 2);
			close (Asd);

			/* Close C also to establish new connection 
			 * in a fresh manner
			 */
			shutdown (Csd, 2);
			close (Csd);
			Csd=-1;
			printf ("Closed connection to  address: %s port=%d \n",
			inet_ntoa (sa.sin_addr),ntohs (sa.sin_port));

			exit(0);
#ifdef TESTING
			printf ("pid %d:quiting, A closed connection \n",getpid());
#endif
		  }
		  else  {
#ifdef ALLTESTING
		  printf ("\nbuffer written to C is:#%s#=%d bytes\n", 
			   buffer, b);
#endif
			/* write A data to C */
			write (Csd, buffer, b);	
#ifdef  DEBUG
			printf ("A to C: #%s#\n", buffer);	
#endif
		  }
	}
	/*Transfer data from C to A*/
	if (we_child && Csd > 0 && FD_ISSET (Csd, &inout_fds) && Asd>0 ) {
		  bzero (buffer, sizeof (buffer));
#ifdef TESTING
		  printf("\nReading from C...");
#endif
		  /* read data from C*/
		  b = read (Csd, buffer, sizeof (buffer));		
#ifdef TESTING
                  printf("Ok, read %d bytes\n",b);
#endif

#ifdef ALLTESTING
		  printf ("buffer read from C is:#%s#=%d bytes\n", 
			   buffer, b);
#endif
		  if (b <= 0) {
			/*C closed connection*/
			shutdown (Csd, 2);
			close (Csd);
			Csd=-1;

			/*Tell A nothing more to hope for*/
			shutdown (Asd, 2);
			close (Asd);
			Asd=-1;
			printf ("Closed connection :   address: %s port=%d \n",
			inet_ntoa (sa.sin_addr),ntohs (sa.sin_port));
			exit(0);
#ifdef TESTING
			printf ("pid %d:quiting, C closed connection \n",getpid());
#endif
		  }
		  else {
#ifdef ALLTESTING
		      printf ("\nbuffer written to A is:#%s#=%d bytes\n", 
			   buffer, b);
#endif
#ifdef TESTING
		      printf("\nWriting to A...");
#endif
		      /*Write data to A*/
		      write (Asd, &buffer, b);
#ifdef DEBUG
			printf ("C to A: #%s#\n", buffer);	
#endif
#ifdef TESTING
		      printf("Ok...\n");
#endif
		    }
	}

 }
} /*End of main*/


connectC(char *host,char *port) {

/*Open C socket and connect to C host*/

	if ((Csd = socket (AF_INET, SOCK_STREAM, 0)) < 0) {
	  perror ("Can't open C socket");
	  exit (-2);
	}
	sc.sin_port = htons ((u_short) atoi (port));

	chost = gethostbyname (host);
#ifdef TESTING
	 printf ("\nC address : %s %d \n" , inet_ntoa (chost->h_addr),
		 ntohs(sc.sin_port)); 

#endif
	 sc.sin_family = AF_INET;
	 memcpy (&sc.sin_addr, chost->h_addr, chost->h_length);

	if (connect (Csd,(struct sockaddr *) &sc, sizeof (sc)) < 0) {
	  perror ("Can't connect to C");
	  exit (-3);
	}
#ifdef TESTING
	else printf("Connected to C\n");
#endif
        cdown=0;
}

my_usleep(x) {
        struct timeval  time;

        time.tv_sec= x/1000000;
        time.tv_usec=x%1000000;
        select(0, NULL, NULL, NULL, &time);
      }

void childhdl ()
{

  wait (0);
  we_full--;
#ifdef TESTING
  printf("\nInside childhandler, a child died\n");
#endif 
  signal (SIGCHLD, childhdl);

}

newdest() {
int c,ph;


      ph=0;
      bzero(buffer,sizeof(buffer));
      c=read(rConfsd,buffer,sizeof(buffer));
      if (c <= 0) {
	  printf("Configuration port closed,shuting down\n");
	  if (Asd>0) shutdown (Asd,2);
	  if (Csd>0) shutdown (Csd,2);
	  shutdown (Confsd,2);
	  close (Asd);
	  close (Csd);
	  close (Confsd);
	  exit(5);
      }
      else buffer[c]='\0';
      sscanf(buffer,"%s%s",desthost,destport);

      if (!strcmp(desthost,"help")) {
	  strcpy(buffer,"\nJust type hostname and port, i.e. \"www.sun.com 80\"\n");
	  strcat(buffer,"or type \"exit\" to exit\n\n");
      }
      else if (!strcmp(desthost,"exit")) {
	  printf("Configuration port requested exit,shuting down\n");
	  if (Asd>0) shutdown (Asd,2);
	  if (Csd>0) shutdown (Csd,2);
	  shutdown (Confsd,2);
	  close (Asd);
	  close (Csd);
	  close (Confsd);
	  exit(5);
      }
      else 
        sprintf(buffer,"\nDestination host: %s\nDestination port:%s\n",
			  desthost,destport);

      strcat(buffer,"\nDestination > ");
      write(rConfsd,buffer,strlen(buffer));
}