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/* io.c
 *
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 *
 *
 * $Id$ */

/* lsh, an implementation of the ssh protocol
 *
 * Copyright (C) 1998 Niels Mller
 *
 * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
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 */

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#include <assert.h>
#include <string.h>

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#include <unistd.h>
#include <poll.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/socket.h>
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#include <arpa/inet.h>
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#include "io.h"
#include "werror.h"
#include "write_buffer.h"
#include "xalloc.h"

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/* A little more than an hour */
#define MAX_TIMEOUT 4000

struct fd_read
{
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  struct abstract_read super;
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  int fd;
};

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static int do_read(struct abstract_read **r, UINT32 length, UINT8 *buffer)
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{
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  struct fd_read *closure
    = (struct fd_read *) *r;

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  MDEBUG(closure);
  
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  while(1)
    {
      int res = read(closure->fd, buffer, length);
      if (!res)
	return A_EOF;
      if (res > 0)
	return res;
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      switch(errno)
	{
	case EINTR:
	  continue;
	case EWOULDBLOCK:  /* aka EAGAIN */
	  return 0;
	default:
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	  werror("io.c: do_read: read() failed (errno %d), %s\n",
		 errno, strerror(errno));
	  debug("  fd = %d, buffer = %p, length = %ud\n",
		closure->fd, buffer, length);
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	  return A_FAIL;
	}
    }
}
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#define FOR_FDS(type, fd, list, extra)				\
{								\
  type **(_fd);							\
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  type *(fd);							\
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  for(_fd = &(list); ((fd) = *_fd); (extra)) {
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#define END_FOR_FDS _fd = &(*_fd)->next; } }

/* UNLINK_FD must be followed by a continue, to avoid updating _fd */
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#define UNLINK_FD (*_fd = (*_fd)->next)
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static int io_iter(struct io_backend *b)
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{
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  struct pollfd *fds;
  int i;
  unsigned long nfds; /* FIXME: Should be nfds_t if that type is defined */
  int timeout;
  int res;

  nfds = b->nio + b->nlisten + b->nconnect;

  if (b->callouts)
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    {
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      time_t now = time(NULL);
      if (now >= b->callouts->when)
	timeout = 0;
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      else
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	{
	  if (b->callouts->when > now + MAX_TIMEOUT)
	    timeout = MAX_TIMEOUT * 1000;
	  else
	    timeout = (b->callouts->when - now) * 1000;
	}
    }
  else
    {
      if (!nfds)
	/* All done */
	return 0;
      timeout = -1;
    }
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  fds = alloca(sizeof(struct pollfd) * nfds);
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  /* Handle fds in order: write, read, accept, connect. */
  i = 0;
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  FOR_FDS(struct io_fd, fd, b->io, i++)
    {
      fds[i].fd = fd->fd;
      fds[i].events = 0;
      if (!fd->on_hold)
	fds[i].events |= POLLIN;

      /* pre_write returns 0 if the buffer is empty */
      if (write_buffer_pre_write(fd->buffer))
	fds[i].events |= POLLOUT;
    }
  END_FOR_FDS;
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  FOR_FDS(struct listen_fd, fd, b->listen, i++)
    {
      fds[i].fd = fd->fd;
      fds[i].events = POLLIN;
    }
  END_FOR_FDS;
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  FOR_FDS(struct connect_fd, fd, b->connect, i++)
    {
      fds[i].fd = fd->fd;
      fds[i].events = POLLOUT;
    }
  END_FOR_FDS;

  res = poll(fds, nfds, timeout);

  if (!res)
    {
      /* Timeout. Run the callout */
      struct callout *f = b->callouts;

      if (!CALLBACK(f->callout))
	fatal("What now?");
      b->callouts = f->next;
      lsh_free(f);
    }
  if (res<0)
    {
      switch(errno)
	{
	case EAGAIN:
	case EINTR:
	  return 1;
	default:
	  fatal("io_run:poll failed: %s", strerror(errno));
	}
    }
  else
    { /* Process files */
      i = 0;

      /* Handle writing first */
      FOR_FDS(struct io_fd, fd, b->io, i++)
	{
	  if (fds[i].revents & POLLOUT)
	    {
	      UINT32 size = MIN(fd->buffer->end - fd->buffer->start,
				fd->buffer->block_size);
	      int res = write(fd->fd,
			      fd->buffer->buffer + fd->buffer->start,
			      size);
	      if (!res)
		fatal("Closed?");
	      if (res < 0)
		switch(errno)
		  {
		  case EINTR:
		  case EAGAIN:
		    break;
		  default:
		    werror("io.c: write failed, %s\n", strerror(errno));
		    CALLBACK(fd->close_callback);

		    fd->please_close = 1;

		    break;
		  }
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	      // else if (!res)
	      // fatal("What now?");
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	      else
		fd->buffer->start += res;
	    }
	}
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      END_FOR_FDS;

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      /* Handle reading */
      i = 0; /* Start over */
      FOR_FDS(struct io_fd, fd, b->io, i++)
	{
	  if (!fd->please_close
	      && (fds[i].revents & POLLIN))
	    {
	      struct fd_read r =
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	      { { STATIC_HEADER do_read }, fd->fd };
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	      /* The handler function may install a new handler */
	      if (!READ_HANDLER(fd->handler,
				&r.super))
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		{
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		  /* FIXME: Perhaps we should not close yet, but
		   * stop reading and close as soon as the write
		   * buffer is flushed? But in that case, we
		   * probably also want to set some flag on the
		   * write buffer so that no more data can be
		   * written into it. */
		  fd->please_close = 1;
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		}
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	    }
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	  if (fd->please_close)
	    {
	      /* FIXME: Cleanup properly...
	       *
	       * After a write error, read state must be freed,
	       * and vice versa. */
	      UNLINK_FD;
	      b->nio--;
	      if (fd->handler)
		lsh_free(fd->handler);
	      lsh_free(fd->buffer);
	      lsh_free(fd);
	      continue;
	    }
	}
      END_FOR_FDS;
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      FOR_FDS(struct listen_fd, fd, b->listen, i++)
	{
	  if (fds[i].revents & POLLIN)
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	    {
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	      /* FIXME: Do something with the peer address? */
	      struct sockaddr_in peer;
	      size_t addr_len = sizeof(peer);
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	      int conn = accept(fd->fd,
				(struct sockaddr *) &peer, &addr_len);
	      if (conn < 0)
		{
		  werror("io.c: accept() failed, %s", strerror(errno));
		  continue;
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		}
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	      if (!FD_CALLBACK(fd->callback, conn))
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		{
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		  /* FIXME: Should fd be closed here? */
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		  UNLINK_FD;
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		  lsh_free(fd);
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		  continue;
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		}
	    }
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	}
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      END_FOR_FDS;
	  
      FOR_FDS(struct connect_fd, fd, b->connect, i++)
	{
	  if (fds[i].revents & POLLOUT)
	    {
	      if (!FD_CALLBACK(fd->callback, fd->fd))
		fatal("What now?");
	      b->nconnect--;
	      UNLINK_FD;
	      lsh_free(fd);
	      continue;
	    }
	}
      END_FOR_FDS;
    }
  return 1;
}

void io_run(struct io_backend *b)
{
  while(io_iter(b))
    ;
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}

/*
 * Fill in ADDR from HOST, SERVICE and PROTOCOL.
 * Supplying a null pointer for HOST means use INADDR_ANY.
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 * Otherwise HOST is an numbers-and-dots ip-number or a dns name.
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 *
 * PROTOCOL can be tcp or udp.
 *
 * Supplying a null pointer for SERVICE, means use port 0, i.e. no port.
 * 
 * Returns zero on errors, 1 if everything is ok.
 */
int
get_inaddr(struct sockaddr_in	* addr,
	   const char		* host,
	   const char		* service,
	   const char		* protocol)
{
  memset(addr, 0, sizeof *addr);
  addr->sin_family = AF_INET;

  /*
   *  Set host part of ADDR
   */
  if (host == NULL)
    addr->sin_addr.s_addr = INADDR_ANY;
  else
    {
      /* First check for numerical ip-number */
      addr->sin_addr.s_addr = inet_addr(host);
      if (addr->sin_addr.s_addr == (unsigned long)-1)
	{
	  struct hostent * hp;
	  
	  hp = gethostbyname(host);
	  if (hp == NULL)
	    return 0;
	  memcpy(&addr->sin_addr, hp->h_addr, hp->h_length);
	  addr->sin_family = hp->h_addrtype;
	}
    }

  /*
   *  Set port part of ADDR
   */
  if (service == NULL)
    addr->sin_port = htons(0);
  else
    {
      char		* end;
      long		  portno;

      portno = strtol(service, &end, 10);
      if (portno > 0  &&  portno <= 65535
	  &&  end != service  &&  *end == '\0')
	{
	  addr->sin_port = htons(portno);
	}
      else
	{
	  struct servent	* serv;

	  serv = getservbyname(service, "tcp");
	  if (serv == NULL)
	    return 0;
	  addr->sin_port = serv->s_port;
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	}
    }
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  return 1;
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}

void io_set_nonblocking(int fd)
{
  if (fcntl(fd, F_SETFL, O_NONBLOCK) < 0)
    fatal("io_set_nonblocking: fcntl() failed, %s", strerror(errno));
}

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/* Some code is taken from bellman's tcputils. */
struct connect_fd *io_connect(struct io_backend *b,
			      struct sockaddr_in *remote,
			      struct sockaddr_in *local,
			      struct fd_callback *f)
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{
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  struct connect_fd *fd;
  int s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
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  if (s<0)
    return NULL;
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  io_set_nonblocking(s);
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  if (local  &&  bind(s, (struct sockaddr *)local, sizeof *local) < 0)
    {
      int saved_errno = errno;
      close(s);
      errno = saved_errno;
      return NULL;
    }
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  if ( (connect(s, (struct sockaddr *)remote, sizeof *remote) < 0)
       && (errno != EINPROGRESS) )       
    {
      int saved_errno = errno;
      close(s);
      errno = saved_errno;
      return NULL;
    }
  
  fd = xalloc(sizeof(struct connect_fd));
  fd->fd = s;
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  fd->callback = f;
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  fd->next = b->connect;
  b->connect = fd;
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  b->nconnect++;
  
  return fd;
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}

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struct listen_fd *io_listen(struct io_backend *b,
			    struct sockaddr_in *local,
			    struct fd_callback *callback)
{
  struct listen_fd *fd;
  int s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
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  if (s<0)
    return NULL;

  io_set_nonblocking(s);

  {
    int yes = 1;
    setsockopt(s, SOL_SOCKET, SO_REUSEADDR, (char*)&yes, sizeof yes);
  }

  if (bind(s, (struct sockaddr *)local, sizeof *local) < 0)
    {
      close(s);
      return NULL;
    }

  if (listen(s, 256) < 0) 
    {
      close(s);
      return NULL;
    }

  fd = xalloc(sizeof(struct connect_fd));

  fd->fd = s;
  fd->callback = callback;

  fd->next = b->listen;
  b->listen = fd;
  b->nlisten++;
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  return fd;
}

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struct abstract_write *io_read_write(struct io_backend *b,
				     int fd,
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				     struct read_handler *read_callback,
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				     UINT32 block_size,
				     struct callback *close_callback)
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{
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  struct io_fd *f= xalloc(sizeof(struct io_fd));
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  struct write_buffer *buffer = write_buffer_alloc(block_size);
  
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  f->fd = fd;
  f->please_close = 0;
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  /* Reading */
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  f->handler = read_callback;
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  f->on_hold = 0;

  /* Writing */
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  f->buffer = buffer;
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  f->close_callback = close_callback;
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  f->next = b->io;
  b->io = f;
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  b->nio++;
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  return &buffer->super;
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}