/* -*- C -*-
 * lullaby internetworks lab: (client alike) cable
 *
 * Copyright (C) 2001  zhaoway <zw@debian.org>
 *
 * $Id: cable.c.txt,v 1.1.1.1 2002/08/14 22:28:21 dan Exp $
 *
 * Compile with: gcc -Wall -g -o cable cable.c
 */

#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <arpa/inet.h>
#include <sys/select.h>
#include <sys/socket.h>

void banner(void)
{
  printf("lullaby internetworks lab: (client alike) cable $Revision: 1.1.1.1 $\n"
	 "Copyright (C) 2001  zhaoway <zw@debian.org>\n\n");
}

void usage(void)
{
  banner();
  printf("Usage: cable [cable buffer size] [1st ip] [1st port] [2nd ip] [2nd port] ..\n\n"
	 "o cable buffer size is in bytes. for example 10240.\n"
	 "o ports should be listening or connection attempts will fail.\n"
	 "o number of ip addr and port pairs is at least 2.\n");
}

/* Return value -1 is a failure .*/
int make_socket(struct sockaddr_in *servaddr)
{
  int sockfd;

  sockfd = socket(AF_INET, SOCK_STREAM, 0);
  if (connect(sockfd, (struct sockaddr *) servaddr, sizeof(struct sockaddr_in)) == -1)
    {
      perror("connect");
      return -1;
    }
  return sockfd;
}

/* Return the number of ports open, < 2 is a failure. */
int cmdline(int argc, char *argv[], int *sockfd[], int *maxline)
{
  struct sockaddr_in *servaddr, tmpaddr;
  int ports = 2, i;
  
  /* We have at least 2 connections. */
  servaddr = malloc(ports * sizeof(struct sockaddr_in));
  if (servaddr == NULL)
    {
      fprintf(stderr, "not enough memory!\n");
      return 1;
    }
  memset(servaddr, 0, sizeof(servaddr));
  for (i = 0; i < ports; i++) servaddr[i].sin_family = AF_INET;
  if (argc < 6
      || (*maxline = strtol(argv[1], NULL, 10)) == 0
      || (inet_pton(AF_INET, argv[2], &servaddr[0].sin_addr)) <= 0
      || (servaddr[0].sin_port = htons(strtol(argv[3], NULL, 10))) == 0
      || (inet_pton(AF_INET, argv[4], &servaddr[1].sin_addr)) <= 0
      || (servaddr[1].sin_port = htons(strtol(argv[5], NULL, 10))) == 0)
    {
      usage();
      return 0;
    }
  banner();
  for ( ; ; )
    {
      if ((argc -= 2) < 6) break;
      memset(&tmpaddr, 0, sizeof(struct sockaddr_in));
      if ((inet_pton(AF_INET, argv[ports * 2 + 2], &tmpaddr.sin_addr)) <= 0)
	break;
      if ((tmpaddr.sin_port = htons(strtol(argv[ports * 2 + 3], NULL, 10))) == 0)
	break;
      servaddr = realloc(servaddr, (ports + 1) * sizeof(struct sockaddr_in));
      servaddr[ports].sin_addr = tmpaddr.sin_addr;
      servaddr[ports].sin_port = tmpaddr.sin_port;
      ports++;
    }
  *sockfd = malloc(ports * sizeof(int));
  if (*sockfd == NULL)
    {
      fprintf(stderr, "not enough memory!\n");
      return 1;
    }
  for (i = 0; i < ports; i++)
    {
      if (((*sockfd)[i] = make_socket(&servaddr[i])) == -1)
	{
	  if (i >= --ports) break;
	  servaddr[i] = servaddr[ports];
	  i--;			/* retry */
	}
    }
  return ports;
}

int main(int argc, char *argv[])
{
  int *sockfd, ports, size, maxline, i, j;
  char *buff;
  fd_set rset, rset_memo, wset, wset_memo;
  struct timeval nowait = { 0, 0 };

  if ((ports = cmdline(argc, argv, &sockfd, &maxline)) < 2) return 1;
  buff = (char *) malloc(maxline * sizeof(char));
  if (buff == NULL)
    {
      fprintf(stderr, "not enough memory!\n");
      return 1;
    }
  FD_ZERO(&rset_memo);
  FD_ZERO(&wset_memo);
  for (i = 0; i < ports; i++)
    {
      FD_SET(sockfd[i], &rset_memo);
      FD_SET(sockfd[i], &wset_memo);
    }
  /* Ignore this to receive EPIPE. */
  signal(SIGPIPE, SIG_IGN);
  /* Main loop. */
  for ( ; ; )
    {
      if (ports < 2)
	{
	  fprintf(stderr,
		  "cable is broken, only %i connection(s) still open\n", ports);
	  return 1;
	}
      /* Prepare for reading. */
      rset = rset_memo;
      /* See if there is any port sending anything. */
      if ((select(FD_SETSIZE, &rset, NULL, NULL, &nowait)) <= 0) continue;
      /* Search the one which is readable. */
      for (i = 0; i < ports; i++)
	{
	  /* See if there is anything to be read from this port. */
	  if (! FD_ISSET(sockfd[i], &rset)) continue;
	  /* What if we have trouble reading? */
	  else if ((size = recv(sockfd[i], buff, maxline, 0)) == -1)
	    {
	      perror("recv err");
	      return errno;
	    }
	  /* What if we did read exactly nothing? */
	  else if (size == 0) continue;
	  /* Read something, prepare for writing. */
	  wset = wset_memo;
	  /* What if we can't write? */
	  if ((select(FD_SETSIZE, NULL, &wset, NULL, &nowait)) <= 0)
	    {
	      fprintf(stderr, "cable is broken, can't write!\n");
	      return 2;
	    }
	  /* Write. */
	  for (j = 0; j < ports; j++)
	    {
	      /* Do not write back to the sending port. */
	      if (j != i && FD_ISSET(sockfd[j], &wset))
		{
		  /* See if we have trouble writing. */
		  if ((send(sockfd[j], buff, size, 0)) == -1)
		    {
		      if (errno == EPIPE)
			{
			  FD_CLR(sockfd[j], &wset);
			  FD_CLR(sockfd[j], &rset);
			  close(sockfd[j]);
			  sockfd[j] = sockfd[--ports];
			}
		      else
			{
			  perror("send err");
			  return errno;
			}
		    }
		}
	    }
	} /* The loop searching the one which is readable. */
    } /* Main loop. */
}