/* Realms of Aurealis Rerouter */
/* James Rhone */

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <netdb.h>
#include <sys/time.h>
#include <fcntl.h>
#include <ctype.h>
#include <string.h>

#include <signal.h>
#include <sys/un.h>
#include <netdb.h>
#include <errno.h>
#include <netinet/in.h>

void	watch(int port);
int	init_socket(int port);
void	nonblock(int s);
int     reaper();
int     goodnight();

extern int errno;

#define MAX_STRING_LENGTH       8192

/* global mother descriptor */
int	mother;

int main(int argc, char **argv)
{
  int	port;
  char	buf[128];

  if (argc != 2)
  {
    printf("usage: %s <port#>\n",*argv);
    exit(0);
  }

  if ((port = atoi(argv[1])) <= 1024) {
     fputs("Illegal port #\n", stderr);
     exit(0);
  }

  watch(port);

  return 1;
}

int reaper()
{
  int status;
  int pid;

  while ((pid = wait3(&status, WNOHANG, (struct rusage *)0)) > 0)
    printf("Child %d exited.\n\r", pid);
}

int goodnight()
{
  printf("Signal received.  Closing mother connection.\n");
  printf("Killing children.\n");
  close(mother);
  exit(3);
}

int passivesock(char *service, char *protocol, int qlen)
{
  struct servent *pse;
  struct protoent *ppe;
  struct sockaddr_in sin;
  int s, type;
  u_short portbase = 0;

  bzero((char *)&sin, sizeof(sin));
  sin.sin_family = AF_INET;
  sin.sin_addr.s_addr = INADDR_ANY;

  if (pse = getservbyname(service, protocol))
    sin.sin_port = htons(ntohs((u_short)pse->s_port) + portbase);
  else
  if ((sin.sin_port = htons((u_short)atoi(service))) == 0)
  {
    printf("can't get %s service entry\n",service);
    exit(0);
  }

  if ((ppe = getprotobyname(protocol)) == 0)
  {
    printf("can't get %s proto entry\n",protocol);
    exit(0); 
  }

  if (!strcmp(protocol, "udp"))
    type = SOCK_DGRAM;
  else
    type = SOCK_STREAM;

  s = socket(PF_INET, type, ppe->p_proto);
  if (s < 0)
  {
    printf("cant create socket\n");
    exit (0);
  }

  if (bind(s, (struct sockaddr *)&sin, sizeof(sin)) < 0)
  {
    printf("cant bind\n");
    exit (0);
  }

  if (type == SOCK_STREAM && listen(s, qlen) < 0)
  {
    printf("cant listen on stream socket\n");
    exit (0);
  }

  return s;
}

int passiveTCP(char *service, int qlen)
{
  return passivesock(service, "tcp", qlen);
}

void interface_to_roa(int sok)
{
  struct sockaddr_in srvadr_in;
  struct hostent *sp;
  int addrlen;
  int mud;
  char buf[MAX_STRING_LENGTH];
  int cnt;
  int opt;

  addrlen = sizeof(struct sockaddr_in);
  memset((char *)&srvadr_in, 0, addrlen);
  srvadr_in.sin_family = AF_INET;
  sp = gethostbyname("sc27.dreamscape.com");
  if (!sp)
  {
    printf("could not get hostname.\n");
    exit(1);
  }

  srvadr_in.sin_addr.s_addr = ((struct in_addr *)(sp->h_addr))->s_addr;
  srvadr_in.sin_port = htons(4000);

  mud = socket(PF_INET, SOCK_STREAM, 0);
  if (mud < 0) 
  {
    perror("Init-mud-socket");
    exit(0);
  }

#if defined(SO_SNDBUF)
  opt = MAX_STRING_LENGTH + 128;
  if (setsockopt(mud, SOL_SOCKET, SO_SNDBUF, (char *) &opt, sizeof(opt)) < 0) 
  {
    perror("setsockopt SNDBUF");
    exit(1);
  }
#endif

  opt = 1;
  if (setsockopt(mud, SOL_SOCKET, SO_REUSEADDR, (char *) & opt, sizeof (opt)) < 0) 
  {
    perror ("setsockopt REUSEADDR");
    exit (0);
  }

#if defined(SO_LINGER)
  {
    struct linger ld;
    ld.l_onoff = 0; ld.l_linger = 0;
    if (setsockopt(mud, SOL_SOCKET, SO_LINGER, (char *) &ld, sizeof(ld)) < 0) 
    {
      perror("setsockopt LINGER");
      exit(1);
    }
  }
#endif

  if (connect(mud, (struct sockaddr *)&srvadr_in, addrlen) < 0)
  {
    printf("couldnt connect to roa.sunyit.edu.\n");
    perror("connect: ");
    exit(1);
  }

  nonblock(mud);
  nonblock(sok);

  printf("Child %d connected to RoA.\n", getpid());

  for ( ; ; )
  {
    errno = 0;
    if ((cnt = recv(mud, buf, MAX_STRING_LENGTH, 0)) < 0)
      if (errno != EAGAIN)
      {
	perror("first recv: ");
	break;
      }

    if (cnt > 0)
    {
      buf[cnt] = '\0';
      if ((cnt = send(sok, buf, strlen(buf), 0)) < 0)
      {
        *buf = '\0';
	break;
      }
    }

    errno = 0;
    if ((cnt = recv(sok, buf, MAX_STRING_LENGTH, 0)) < 0)
      if (errno != EAGAIN)
      {
	perror("second recv: ");
	break;
      }

    if (cnt > 0)
    {
      buf[cnt] = '\0';
      if ((cnt = send(mud, buf, strlen(buf), 0)) < 0)
      {
        *buf = '\0';
        break;
      }
    }

  }

  close(sok);
  close(mud);
  printf("Child %d connection closed.\n", getpid());
  exit(3);
}

void	watch(int port)
{
   int con;

   signal (SIGCHLD, (void *) reaper);
   signal (SIGINT,  (void *) goodnight);
   signal (SIGTERM, (void *) goodnight);
   signal (SIGHUP, (void *) goodnight);
   signal (SIGABRT, (void *) goodnight);

   mother = init_socket(port);
   printf("mother socket opened on port %d\n",port);

   for (; ; ) 
   {
     con = accept(mother, (struct sockaddr *) 0, 0); 
     if (con < 0) continue;
     if (!fork())
     {
       printf("Connection detected, Child %d forked.\n",getpid());
       interface_to_roa(con);
       close(con);
       exit(0);
     }
     else
       close(con);
   }
}

int	init_socket(int port)
{
   int	s;
   char	*opt;
   char	hostname[1024];
   struct sockaddr_in sa;
   struct hostent *hp;

   bzero(&sa, sizeof(struct sockaddr_in ));
   gethostname(hostname, 1023);

   hp = gethostbyname(hostname);
   if (!hp)
   {
      perror("gethostbyname");
      exit(0);
   }

   sa.sin_family = hp->h_addrtype;
   sa.sin_port	 = htons(port);

   s = socket(AF_INET, SOCK_STREAM, 0);
   if (s < 0) 
   {
      perror("Init-socket");
      exit(0);
   }
   if (setsockopt (s, SOL_SOCKET, SO_REUSEADDR, (char *) & opt, sizeof (opt)) < 0) 
   {
      perror ("setsockopt REUSEADDR");
      exit (0);
   }

#ifdef USE_LINGER
   struct linger ld;
   ld.l_onoff = 1;
   ld.l_linger = 1000;
   if (setsockopt(s, SOL_SOCKET, SO_LINGER, &ld, sizeof(ld)) < 0) 
   {
      perror("setsockopt LINGER");
      exit(0);
   }
#endif

   if (bind(s, (struct sockaddr *)&sa, sizeof(sa)) < 0) 
   {
      perror("bind");
      close(s);
      exit(0);
   }
   listen(s, 5);
   return(s);
}

void	nonblock(int s)
{
   int	flags;
   flags = fcntl(s, F_GETFL);
   flags |= O_NONBLOCK;
   if (fcntl(s, F_SETFL, flags) < 0) {
      perror("Fatal error executing nonblock (comm.c)");
      exit(1);
   }
}