nchan.c - security/openssh-library - Rivoreo Source Code Repositories

 /*
  * Copyright (c) 1999 Markus Friedl.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "includes.h"
 RCSID("$OpenBSD: nchan.c,v 1.28 2001/05/31 10:30:16 markus Exp $");

 #include "ssh1.h"
 #include "ssh2.h"
 #include "buffer.h"
 #include "packet.h"
 #include "channels.h"
 #include "compat.h"
 #include "log.h"

 /*
  * SSH Protocol 1.5 aka New Channel Protocol
  * Thanks to Martina, Axel and everyone who left Erlangen, leaving me bored.
  * Written by Markus Friedl in October 1999
  *
  * Protocol versions 1.3 and 1.5 differ in the handshake protocol used for the
  * tear down of channels:
  *
  * 1.3:	strict request-ack-protocol:
  * 	CLOSE	->
  * 		<-  CLOSE_CONFIRM
  *
  * 1.5:	uses variations of:
  * 	IEOF	->
  * 		<-  OCLOSE
  * 		<-  IEOF
  * 	OCLOSE	->
  * 	i.e. both sides have to close the channel
  *
  * 2.0: the EOF messages are optional
  *
  * See the debugging output from 'ssh -v' and 'sshd -d' of
  * ssh-1.2.27 as an example.
  *
  */

 /* functions manipulating channel states */
 /*
  * EVENTS update channel input/output states execute ACTIONS
  */
 /* events concerning the INPUT from socket for channel (istate) */
 chan_event_fn *chan_rcvd_oclose			= NULL;
 chan_event_fn *chan_read_failed			= NULL;
 chan_event_fn *chan_ibuf_empty			= NULL;
 /* events concerning the OUTPUT from channel for socket (ostate) */
 chan_event_fn *chan_rcvd_ieof			= NULL;
 chan_event_fn *chan_write_failed		= NULL;
 chan_event_fn *chan_obuf_empty			= NULL;
 /*
  * ACTIONS: should never update the channel states
  */
 static void	chan_send_ieof1(Channel *c);
 static void	chan_send_oclose1(Channel *c);
 static void	chan_send_close2(Channel *c);
 static void	chan_send_eof2(Channel *c);

 /* helper */
 static void	chan_shutdown_write(Channel *c);
 static void	chan_shutdown_read(Channel *c);

 /*
  * SSH1 specific implementation of event functions
  */

 static void
 chan_rcvd_oclose1(Channel *c)
 {
 	debug("channel %d: rcvd oclose", c->self);
 	switch (c->istate) {
 	case CHAN_INPUT_WAIT_OCLOSE:
 		debug("channel %d: input wait_oclose -> closed", c->self);
 		c->istate = CHAN_INPUT_CLOSED;
 		break;
 	case CHAN_INPUT_OPEN:
 		debug("channel %d: input open -> closed", c->self);
 		chan_shutdown_read(c);
 		chan_send_ieof1(c);
 		c->istate = CHAN_INPUT_CLOSED;
 		break;
 	case CHAN_INPUT_WAIT_DRAIN:
 		/* both local read_failed and remote write_failed  */
 		log("channel %d: input drain -> closed", c->self);
 		chan_send_ieof1(c);
 		c->istate = CHAN_INPUT_CLOSED;
 		break;
 	default:
 		error("channel %d: protocol error: rcvd_oclose for istate %d",
 		    c->self, c->istate);
 		return;
 	}
 }
 static void
 chan_read_failed_12(Channel *c)
 {
 	debug("channel %d: read failed", c->self);
 	switch (c->istate) {
 	case CHAN_INPUT_OPEN:
 		debug("channel %d: input open -> drain", c->self);
 		chan_shutdown_read(c);
 		c->istate = CHAN_INPUT_WAIT_DRAIN;
 #if 0
 		if (buffer_len(&c->input) == 0) {
 			debug("channel %d: input: no drain shortcut", c->self);
 			chan_ibuf_empty(c);
 		}
 #endif
 		break;
 	default:
 		error("channel %d: chan_read_failed for istate %d",
 		    c->self, c->istate);
 		break;
 	}
 }
 static void
 chan_ibuf_empty1(Channel *c)
 {
 	debug("channel %d: ibuf empty", c->self);
 	if (buffer_len(&c->input)) {
 		error("channel %d: chan_ibuf_empty for non empty buffer",
 		    c->self);
 		return;
 	}
 	switch (c->istate) {
 	case CHAN_INPUT_WAIT_DRAIN:
 		debug("channel %d: input drain -> wait_oclose", c->self);
 		chan_send_ieof1(c);
 		c->istate = CHAN_INPUT_WAIT_OCLOSE;
 		break;
 	default:
 		error("channel %d: chan_ibuf_empty for istate %d",
 		    c->self, c->istate);
 		break;
 	}
 }
 static void
 chan_rcvd_ieof1(Channel *c)
 {
 	debug("channel %d: rcvd ieof", c->self);
 	if (c->type != SSH_CHANNEL_OPEN) {
 		debug("channel %d: non-open", c->self);
 		if (c->istate == CHAN_INPUT_OPEN) {
 			debug("channel %d: non-open: input open -> wait_oclose",
 			    c->self);
 			chan_shutdown_read(c);
 			chan_send_ieof1(c);
 			c->istate = CHAN_INPUT_WAIT_OCLOSE;
 		} else {
 			error("channel %d: non-open: istate %d != open",
 			    c->self, c->istate);
 		}
 		if (c->ostate == CHAN_OUTPUT_OPEN) {
 			debug("channel %d: non-open: output open -> closed",
 			    c->self);
 			chan_send_oclose1(c);
 			c->ostate = CHAN_OUTPUT_CLOSED;
 		} else {
 			error("channel %d: non-open: ostate %d != open",
 			    c->self, c->ostate);
 		}
 		return;
 	}
 	switch (c->ostate) {
 	case CHAN_OUTPUT_OPEN:
 		debug("channel %d: output open -> drain", c->self);
 		c->ostate = CHAN_OUTPUT_WAIT_DRAIN;
 		break;
 	case CHAN_OUTPUT_WAIT_IEOF:
 		debug("channel %d: output wait_ieof -> closed", c->self);
 		c->ostate = CHAN_OUTPUT_CLOSED;
 		break;
 	default:
 		error("channel %d: protocol error: rcvd_ieof for ostate %d",
 		    c->self, c->ostate);
 		break;
 	}
 }
 static void
 chan_write_failed1(Channel *c)
 {
 	debug("channel %d: write failed", c->self);
 	switch (c->ostate) {
 	case CHAN_OUTPUT_OPEN:
 		debug("channel %d: output open -> wait_ieof", c->self);
 		chan_send_oclose1(c);
 		c->ostate = CHAN_OUTPUT_WAIT_IEOF;
 		break;
 	case CHAN_OUTPUT_WAIT_DRAIN:
 		debug("channel %d: output wait_drain -> closed", c->self);
 		chan_send_oclose1(c);
 		c->ostate = CHAN_OUTPUT_CLOSED;
 		break;
 	default:
 		error("channel %d: chan_write_failed for ostate %d",
 		    c->self, c->ostate);
 		break;
 	}
 }
 static void
 chan_obuf_empty1(Channel *c)
 {
 	debug("channel %d: obuf empty", c->self);
 	if (buffer_len(&c->output)) {
 		error("channel %d: chan_obuf_empty for non empty buffer",
 		    c->self);
 		return;
 	}
 	switch (c->ostate) {
 	case CHAN_OUTPUT_WAIT_DRAIN:
 		debug("channel %d: output drain -> closed", c->self);
 		chan_send_oclose1(c);
 		c->ostate = CHAN_OUTPUT_CLOSED;
 		break;
 	default:
 		error("channel %d: internal error: obuf_empty for ostate %d",
 		    c->self, c->ostate);
 		break;
 	}
 }
 static void
 chan_send_ieof1(Channel *c)
 {
 	debug("channel %d: send ieof", c->self);
 	switch (c->istate) {
 	case CHAN_INPUT_OPEN:
 	case CHAN_INPUT_WAIT_DRAIN:
 		packet_start(SSH_MSG_CHANNEL_INPUT_EOF);
 		packet_put_int(c->remote_id);
 		packet_send();
 		break;
 	default:
 		error("channel %d: cannot send ieof for istate %d",
 		    c->self, c->istate);
 		break;
 	}
 }
 static void
 chan_send_oclose1(Channel *c)
 {
 	debug("channel %d: send oclose", c->self);
 	switch (c->ostate) {
 	case CHAN_OUTPUT_OPEN:
 	case CHAN_OUTPUT_WAIT_DRAIN:
 		chan_shutdown_write(c);
 		buffer_consume(&c->output, buffer_len(&c->output));
 		packet_start(SSH_MSG_CHANNEL_OUTPUT_CLOSE);
 		packet_put_int(c->remote_id);
 		packet_send();
 		break;
 	default:
 		error("channel %d: cannot send oclose for ostate %d",
 		     c->self, c->ostate);
 		break;
 	}
 }

 /*
  * the same for SSH2
  */
 static void
 chan_rcvd_oclose2(Channel *c)
 {
 	debug("channel %d: rcvd close", c->self);
 	if (c->flags & CHAN_CLOSE_RCVD)
 		error("channel %d: protocol error: close rcvd twice", c->self);
 	c->flags |= CHAN_CLOSE_RCVD;
 	if (c->type == SSH_CHANNEL_LARVAL) {
 		/* tear down larval channels immediately */
 		c->ostate = CHAN_OUTPUT_CLOSED;
 		c->istate = CHAN_INPUT_CLOSED;
 		return;
 	}
 	switch (c->ostate) {
 	case CHAN_OUTPUT_OPEN:
 		/*
 		 * wait until a data from the channel is consumed if a CLOSE
 		 * is received
 		 */
 		debug("channel %d: output open -> drain", c->self);
 		c->ostate = CHAN_OUTPUT_WAIT_DRAIN;
 		break;
 	}
 	switch (c->istate) {
 	case CHAN_INPUT_OPEN:
 		debug("channel %d: input open -> closed", c->self);
 		chan_shutdown_read(c);
 		break;
 	case CHAN_INPUT_WAIT_DRAIN:
 		debug("channel %d: input drain -> closed", c->self);
 		chan_send_eof2(c);
 		break;
 	}
 	c->istate = CHAN_INPUT_CLOSED;
 }
 static void
 chan_ibuf_empty2(Channel *c)
 {
 	debug("channel %d: ibuf empty", c->self);
 	if (buffer_len(&c->input)) {
 		error("channel %d: chan_ibuf_empty for non empty buffer",
 		     c->self);
 		return;
 	}
 	switch (c->istate) {
 	case CHAN_INPUT_WAIT_DRAIN:
 		debug("channel %d: input drain -> closed", c->self);
 		if (!(c->flags & CHAN_CLOSE_SENT))
 			chan_send_eof2(c);
 		c->istate = CHAN_INPUT_CLOSED;
 		break;
 	default:
 		error("channel %d: chan_ibuf_empty for istate %d",
 		     c->self, c->istate);
 		break;
 	}
 }
 static void
 chan_rcvd_ieof2(Channel *c)
 {
 	debug("channel %d: rcvd eof", c->self);
 	if (c->ostate == CHAN_OUTPUT_OPEN) {
 		debug("channel %d: output open -> drain", c->self);
 		c->ostate = CHAN_OUTPUT_WAIT_DRAIN;
 	}
 }
 static void
 chan_write_failed2(Channel *c)
 {
 	debug("channel %d: write failed", c->self);
 	switch (c->ostate) {
 	case CHAN_OUTPUT_OPEN:
 		debug("channel %d: output open -> closed", c->self);
 		chan_shutdown_write(c); /* ?? */
 		c->ostate = CHAN_OUTPUT_CLOSED;
 		break;
 	case CHAN_OUTPUT_WAIT_DRAIN:
 		debug("channel %d: output drain -> closed", c->self);
 		chan_shutdown_write(c);
 		c->ostate = CHAN_OUTPUT_CLOSED;
 		break;
 	default:
 		error("channel %d: chan_write_failed for ostate %d",
 		    c->self, c->ostate);
 		break;
 	}
 }
 static void
 chan_obuf_empty2(Channel *c)
 {
 	debug("channel %d: obuf empty", c->self);
 	if (buffer_len(&c->output)) {
 		error("channel %d: chan_obuf_empty for non empty buffer",
 		    c->self);
 		return;
 	}
 	switch (c->ostate) {
 	case CHAN_OUTPUT_WAIT_DRAIN:
 		debug("channel %d: output drain -> closed", c->self);
 		chan_shutdown_write(c);
 		c->ostate = CHAN_OUTPUT_CLOSED;
 		break;
 	default:
 		error("channel %d: chan_obuf_empty for ostate %d",
 		    c->self, c->ostate);
 		break;
 	}
 }
 static void
 chan_send_eof2(Channel *c)
 {
 	debug("channel %d: send eof", c->self);
 	switch (c->istate) {
 	case CHAN_INPUT_WAIT_DRAIN:
 		packet_start(SSH2_MSG_CHANNEL_EOF);
 		packet_put_int(c->remote_id);
 		packet_send();
 		break;
 	default:
 		error("channel %d: cannot send eof for istate %d",
 		    c->self, c->istate);
 		break;
 	}
 }
 static void
 chan_send_close2(Channel *c)
 {
 	debug("channel %d: send close", c->self);
 	if (c->ostate != CHAN_OUTPUT_CLOSED ||
 	    c->istate != CHAN_INPUT_CLOSED) {
 		error("channel %d: cannot send close for istate/ostate %d/%d",
 		    c->self, c->istate, c->ostate);
 	} else if (c->flags & CHAN_CLOSE_SENT) {
 		error("channel %d: already sent close", c->self);
 	} else {
 		packet_start(SSH2_MSG_CHANNEL_CLOSE);
 		packet_put_int(c->remote_id);
 		packet_send();
 		c->flags |= CHAN_CLOSE_SENT;
 	}
 }

 /* shared */

 void
 chan_mark_dead(Channel *c)
 {
 	c->type = SSH_CHANNEL_ZOMBIE;
 }

 int
 chan_is_dead(Channel *c)
 {
 	if (c->type == SSH_CHANNEL_ZOMBIE) {
 		debug("channel %d: zombie", c->self);
 		return 1;
 	}
 	if (c->istate != CHAN_INPUT_CLOSED || c->ostate != CHAN_OUTPUT_CLOSED)
 		return 0;
 	if (!compat20) {
 		debug("channel %d: is dead", c->self);
 		return 1;
 	}
 	/*
 	 * we have to delay the close message if the efd (for stderr) is
 	 * still active
 	 */
 	if (((c->extended_usage != CHAN_EXTENDED_IGNORE) &&
 	    buffer_len(&c->extended) > 0)
 #if 0
 	    || ((c->extended_usage == CHAN_EXTENDED_READ) &&
 	    c->efd != -1)
 #endif
 	    ) {
 		debug2("channel %d: active efd: %d len %d type %s",
 		    c->self, c->efd, buffer_len(&c->extended),
 		    c->extended_usage==CHAN_EXTENDED_READ ?
 		       "read": "write");
 	} else {
 		if (!(c->flags & CHAN_CLOSE_SENT)) {
 			chan_send_close2(c);
 		}
 		if ((c->flags & CHAN_CLOSE_SENT) &&
 		    (c->flags & CHAN_CLOSE_RCVD)) {
 			debug("channel %d: is dead", c->self);
 			return 1;
 		}
 	}
 	return 0;
 }

 void
 chan_init_iostates(Channel *c)
 {
 	c->ostate = CHAN_OUTPUT_OPEN;
 	c->istate = CHAN_INPUT_OPEN;
 	c->flags = 0;
 }

 /* init */
 void
 chan_init(void)
 {
 	if (compat20) {
 		chan_rcvd_oclose		= chan_rcvd_oclose2;
 		chan_read_failed		= chan_read_failed_12;
 		chan_ibuf_empty			= chan_ibuf_empty2;

 		chan_rcvd_ieof			= chan_rcvd_ieof2;
 		chan_write_failed		= chan_write_failed2;
 		chan_obuf_empty			= chan_obuf_empty2;
 	} else {
 		chan_rcvd_oclose		= chan_rcvd_oclose1;
 		chan_read_failed		= chan_read_failed_12;
 		chan_ibuf_empty			= chan_ibuf_empty1;

 		chan_rcvd_ieof			= chan_rcvd_ieof1;
 		chan_write_failed		= chan_write_failed1;
 		chan_obuf_empty			= chan_obuf_empty1;
 	}
 }

 /* helper */
 static void
 chan_shutdown_write(Channel *c)
 {
 	buffer_consume(&c->output, buffer_len(&c->output));
 	if (compat20 && c->type == SSH_CHANNEL_LARVAL)
 		return;
 	/* shutdown failure is allowed if write failed already */
 	debug("channel %d: close_write", c->self);
 	if (c->sock != -1) {
 		if (shutdown(c->sock, SHUT_WR) < 0)
 			debug("channel %d: chan_shutdown_write: "
 			    "shutdown() failed for fd%d: %.100s",
 			    c->self, c->sock, strerror(errno));
 	} else {
 		if (close(c->wfd) < 0)
 			log("channel %d: chan_shutdown_write: "
 			    "close() failed for fd%d: %.100s",
 			    c->self, c->wfd, strerror(errno));
 		c->wfd = -1;
 	}
 }
 static void
 chan_shutdown_read(Channel *c)
 {
 	if (compat20 && c->type == SSH_CHANNEL_LARVAL)
 		return;
 	debug("channel %d: close_read", c->self);
 	if (c->sock != -1) {
 		/*
 		 * shutdown(sock, SHUT_READ) may return ENOTCONN if the
 		 * write side has been closed already. (bug on Linux)
 		 * HP-UX will return EINVAL.
 		 */
 		if (shutdown(c->sock, SHUT_RD) < 0
 		    && (errno != ENOTCONN && errno != EINVAL))
 			error("channel %d: chan_shutdown_read: "
 			    "shutdown() failed for fd%d [i%d o%d]: %.100s",
 			    c->self, c->sock, c->istate, c->ostate,
                             strerror(errno));
 	} else {
 		if (close(c->rfd) < 0)
 			log("channel %d: chan_shutdown_read: "
 			    "close() failed for fd%d: %.100s",
 			    c->self, c->rfd, strerror(errno));
 		c->rfd = -1;
 	}
 }
	/*
	* Copyright (c) 1999 Markus Friedl. All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	*
	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "includes.h"
	RCSID("$OpenBSD: nchan.c,v 1.28 2001/05/31 10:30:16 markus Exp $");

	#include "ssh1.h"
	#include "ssh2.h"
	#include "buffer.h"
	#include "packet.h"
	#include "channels.h"
	#include "compat.h"
	#include "log.h"

	/*
	* SSH Protocol 1.5 aka New Channel Protocol
	* Thanks to Martina, Axel and everyone who left Erlangen, leaving me bored.
	* Written by Markus Friedl in October 1999
	*
	* Protocol versions 1.3 and 1.5 differ in the handshake protocol used for the
	* tear down of channels:
	*
	* 1.3: strict request-ack-protocol:
	* CLOSE ->
	* <- CLOSE_CONFIRM
	*
	* 1.5: uses variations of:
	* IEOF ->
	* <- OCLOSE
	* <- IEOF
	* OCLOSE ->
	* i.e. both sides have to close the channel
	*
	* 2.0: the EOF messages are optional
	*
	* See the debugging output from 'ssh -v' and 'sshd -d' of
	* ssh-1.2.27 as an example.
	*
	*/

	/* functions manipulating channel states */
	/*
	* EVENTS update channel input/output states execute ACTIONS
	*/
	/* events concerning the INPUT from socket for channel (istate) */
	chan_event_fn *chan_rcvd_oclose = NULL;
	chan_event_fn *chan_read_failed = NULL;
	chan_event_fn *chan_ibuf_empty = NULL;
	/* events concerning the OUTPUT from channel for socket (ostate) */
	chan_event_fn *chan_rcvd_ieof = NULL;
	chan_event_fn *chan_write_failed = NULL;
	chan_event_fn *chan_obuf_empty = NULL;
	/*
	* ACTIONS: should never update the channel states
	*/
	static void chan_send_ieof1(Channel *c);
	static void chan_send_oclose1(Channel *c);
	static void chan_send_close2(Channel *c);
	static void chan_send_eof2(Channel *c);

	/* helper */
	static void chan_shutdown_write(Channel *c);
	static void chan_shutdown_read(Channel *c);

	/*
	* SSH1 specific implementation of event functions
	*/

	static void
	chan_rcvd_oclose1(Channel *c)
	{
	debug("channel %d: rcvd oclose", c->self);
	switch (c->istate) {
	case CHAN_INPUT_WAIT_OCLOSE:
	debug("channel %d: input wait_oclose -> closed", c->self);
	c->istate = CHAN_INPUT_CLOSED;
	break;
	case CHAN_INPUT_OPEN:
	debug("channel %d: input open -> closed", c->self);
	chan_shutdown_read(c);
	chan_send_ieof1(c);
	c->istate = CHAN_INPUT_CLOSED;
	break;
	case CHAN_INPUT_WAIT_DRAIN:
	/* both local read_failed and remote write_failed */
	log("channel %d: input drain -> closed", c->self);
	chan_send_ieof1(c);
	c->istate = CHAN_INPUT_CLOSED;
	break;
	default:
	error("channel %d: protocol error: rcvd_oclose for istate %d",
	c->self, c->istate);
	return;
	}
	}
	static void
	chan_read_failed_12(Channel *c)
	{
	debug("channel %d: read failed", c->self);
	switch (c->istate) {
	case CHAN_INPUT_OPEN:
	debug("channel %d: input open -> drain", c->self);
	chan_shutdown_read(c);
	c->istate = CHAN_INPUT_WAIT_DRAIN;
	#if 0
	if (buffer_len(&c->input) == 0) {
	debug("channel %d: input: no drain shortcut", c->self);
	chan_ibuf_empty(c);
	}
	#endif
	break;
	default:
	error("channel %d: chan_read_failed for istate %d",
	c->self, c->istate);
	break;
	}
	}
	static void
	chan_ibuf_empty1(Channel *c)
	{
	debug("channel %d: ibuf empty", c->self);
	if (buffer_len(&c->input)) {
	error("channel %d: chan_ibuf_empty for non empty buffer",
	c->self);
	return;
	}
	switch (c->istate) {
	case CHAN_INPUT_WAIT_DRAIN:
	debug("channel %d: input drain -> wait_oclose", c->self);
	chan_send_ieof1(c);
	c->istate = CHAN_INPUT_WAIT_OCLOSE;
	break;
	default:
	error("channel %d: chan_ibuf_empty for istate %d",
	c->self, c->istate);
	break;
	}
	}
	static void
	chan_rcvd_ieof1(Channel *c)
	{
	debug("channel %d: rcvd ieof", c->self);
	if (c->type != SSH_CHANNEL_OPEN) {
	debug("channel %d: non-open", c->self);
	if (c->istate == CHAN_INPUT_OPEN) {
	debug("channel %d: non-open: input open -> wait_oclose",
	c->self);
	chan_shutdown_read(c);
	chan_send_ieof1(c);
	c->istate = CHAN_INPUT_WAIT_OCLOSE;
	} else {
	error("channel %d: non-open: istate %d != open",
	c->self, c->istate);
	}
	if (c->ostate == CHAN_OUTPUT_OPEN) {
	debug("channel %d: non-open: output open -> closed",
	c->self);
	chan_send_oclose1(c);
	c->ostate = CHAN_OUTPUT_CLOSED;
	} else {
	error("channel %d: non-open: ostate %d != open",
	c->self, c->ostate);
	}
	return;
	}
	switch (c->ostate) {
	case CHAN_OUTPUT_OPEN:
	debug("channel %d: output open -> drain", c->self);
	c->ostate = CHAN_OUTPUT_WAIT_DRAIN;
	break;
	case CHAN_OUTPUT_WAIT_IEOF:
	debug("channel %d: output wait_ieof -> closed", c->self);
	c->ostate = CHAN_OUTPUT_CLOSED;
	break;
	default:
	error("channel %d: protocol error: rcvd_ieof for ostate %d",
	c->self, c->ostate);
	break;
	}
	}
	static void
	chan_write_failed1(Channel *c)
	{
	debug("channel %d: write failed", c->self);
	switch (c->ostate) {
	case CHAN_OUTPUT_OPEN:
	debug("channel %d: output open -> wait_ieof", c->self);
	chan_send_oclose1(c);
	c->ostate = CHAN_OUTPUT_WAIT_IEOF;
	break;
	case CHAN_OUTPUT_WAIT_DRAIN:
	debug("channel %d: output wait_drain -> closed", c->self);
	chan_send_oclose1(c);
	c->ostate = CHAN_OUTPUT_CLOSED;
	break;
	default:
	error("channel %d: chan_write_failed for ostate %d",
	c->self, c->ostate);
	break;
	}
	}
	static void
	chan_obuf_empty1(Channel *c)
	{
	debug("channel %d: obuf empty", c->self);
	if (buffer_len(&c->output)) {
	error("channel %d: chan_obuf_empty for non empty buffer",
	c->self);
	return;
	}
	switch (c->ostate) {
	case CHAN_OUTPUT_WAIT_DRAIN:
	debug("channel %d: output drain -> closed", c->self);
	chan_send_oclose1(c);
	c->ostate = CHAN_OUTPUT_CLOSED;
	break;
	default:
	error("channel %d: internal error: obuf_empty for ostate %d",
	c->self, c->ostate);
	break;
	}
	}
	static void
	chan_send_ieof1(Channel *c)
	{
	debug("channel %d: send ieof", c->self);
	switch (c->istate) {
	case CHAN_INPUT_OPEN:
	case CHAN_INPUT_WAIT_DRAIN:
	packet_start(SSH_MSG_CHANNEL_INPUT_EOF);
	packet_put_int(c->remote_id);
	packet_send();
	break;
	default:
	error("channel %d: cannot send ieof for istate %d",
	c->self, c->istate);
	break;
	}
	}
	static void
	chan_send_oclose1(Channel *c)
	{
	debug("channel %d: send oclose", c->self);
	switch (c->ostate) {
	case CHAN_OUTPUT_OPEN:
	case CHAN_OUTPUT_WAIT_DRAIN:
	chan_shutdown_write(c);
	buffer_consume(&c->output, buffer_len(&c->output));
	packet_start(SSH_MSG_CHANNEL_OUTPUT_CLOSE);
	packet_put_int(c->remote_id);
	packet_send();
	break;
	default:
	error("channel %d: cannot send oclose for ostate %d",
	c->self, c->ostate);
	break;
	}
	}

	/*
	* the same for SSH2
	*/
	static void
	chan_rcvd_oclose2(Channel *c)
	{
	debug("channel %d: rcvd close", c->self);
	if (c->flags & CHAN_CLOSE_RCVD)
	error("channel %d: protocol error: close rcvd twice", c->self);
	c->flags \|= CHAN_CLOSE_RCVD;
	if (c->type == SSH_CHANNEL_LARVAL) {
	/* tear down larval channels immediately */
	c->ostate = CHAN_OUTPUT_CLOSED;
	c->istate = CHAN_INPUT_CLOSED;
	return;
	}
	switch (c->ostate) {
	case CHAN_OUTPUT_OPEN:
	/*
	* wait until a data from the channel is consumed if a CLOSE
	* is received
	*/
	debug("channel %d: output open -> drain", c->self);
	c->ostate = CHAN_OUTPUT_WAIT_DRAIN;
	break;
	}
	switch (c->istate) {
	case CHAN_INPUT_OPEN:
	debug("channel %d: input open -> closed", c->self);
	chan_shutdown_read(c);
	break;
	case CHAN_INPUT_WAIT_DRAIN:
	debug("channel %d: input drain -> closed", c->self);
	chan_send_eof2(c);
	break;
	}
	c->istate = CHAN_INPUT_CLOSED;
	}
	static void
	chan_ibuf_empty2(Channel *c)
	{
	debug("channel %d: ibuf empty", c->self);
	if (buffer_len(&c->input)) {
	error("channel %d: chan_ibuf_empty for non empty buffer",
	c->self);
	return;
	}
	switch (c->istate) {
	case CHAN_INPUT_WAIT_DRAIN:
	debug("channel %d: input drain -> closed", c->self);
	if (!(c->flags & CHAN_CLOSE_SENT))
	chan_send_eof2(c);
	c->istate = CHAN_INPUT_CLOSED;
	break;
	default:
	error("channel %d: chan_ibuf_empty for istate %d",
	c->self, c->istate);
	break;
	}
	}
	static void
	chan_rcvd_ieof2(Channel *c)
	{
	debug("channel %d: rcvd eof", c->self);
	if (c->ostate == CHAN_OUTPUT_OPEN) {
	debug("channel %d: output open -> drain", c->self);
	c->ostate = CHAN_OUTPUT_WAIT_DRAIN;
	}
	}
	static void
	chan_write_failed2(Channel *c)
	{
	debug("channel %d: write failed", c->self);
	switch (c->ostate) {
	case CHAN_OUTPUT_OPEN:
	debug("channel %d: output open -> closed", c->self);
	chan_shutdown_write(c); /* ?? */
	c->ostate = CHAN_OUTPUT_CLOSED;
	break;
	case CHAN_OUTPUT_WAIT_DRAIN:
	debug("channel %d: output drain -> closed", c->self);
	chan_shutdown_write(c);
	c->ostate = CHAN_OUTPUT_CLOSED;
	break;
	default:
	error("channel %d: chan_write_failed for ostate %d",
	c->self, c->ostate);
	break;
	}
	}
	static void
	chan_obuf_empty2(Channel *c)
	{
	debug("channel %d: obuf empty", c->self);
	if (buffer_len(&c->output)) {
	error("channel %d: chan_obuf_empty for non empty buffer",
	c->self);
	return;
	}
	switch (c->ostate) {
	case CHAN_OUTPUT_WAIT_DRAIN:
	debug("channel %d: output drain -> closed", c->self);
	chan_shutdown_write(c);
	c->ostate = CHAN_OUTPUT_CLOSED;
	break;
	default:
	error("channel %d: chan_obuf_empty for ostate %d",
	c->self, c->ostate);
	break;
	}
	}
	static void
	chan_send_eof2(Channel *c)
	{
	debug("channel %d: send eof", c->self);
	switch (c->istate) {
	case CHAN_INPUT_WAIT_DRAIN:
	packet_start(SSH2_MSG_CHANNEL_EOF);
	packet_put_int(c->remote_id);
	packet_send();
	break;
	default:
	error("channel %d: cannot send eof for istate %d",
	c->self, c->istate);
	break;
	}
	}
	static void
	chan_send_close2(Channel *c)
	{
	debug("channel %d: send close", c->self);
	if (c->ostate != CHAN_OUTPUT_CLOSED \|\|
	c->istate != CHAN_INPUT_CLOSED) {
	error("channel %d: cannot send close for istate/ostate %d/%d",
	c->self, c->istate, c->ostate);
	} else if (c->flags & CHAN_CLOSE_SENT) {
	error("channel %d: already sent close", c->self);
	} else {
	packet_start(SSH2_MSG_CHANNEL_CLOSE);
	packet_put_int(c->remote_id);
	packet_send();
	c->flags \|= CHAN_CLOSE_SENT;
	}
	}

	/* shared */

	void
	chan_mark_dead(Channel *c)
	{
	c->type = SSH_CHANNEL_ZOMBIE;
	}

	int
	chan_is_dead(Channel *c)
	{
	if (c->type == SSH_CHANNEL_ZOMBIE) {
	debug("channel %d: zombie", c->self);
	return 1;
	}
	if (c->istate != CHAN_INPUT_CLOSED \|\| c->ostate != CHAN_OUTPUT_CLOSED)
	return 0;
	if (!compat20) {
	debug("channel %d: is dead", c->self);
	return 1;
	}
	/*
	* we have to delay the close message if the efd (for stderr) is
	* still active
	*/
	if (((c->extended_usage != CHAN_EXTENDED_IGNORE) &&
	buffer_len(&c->extended) > 0)
	#if 0
	\|\| ((c->extended_usage == CHAN_EXTENDED_READ) &&
	c->efd != -1)
	#endif
	) {
	debug2("channel %d: active efd: %d len %d type %s",
	c->self, c->efd, buffer_len(&c->extended),
	c->extended_usage==CHAN_EXTENDED_READ ?
	"read": "write");
	} else {
	if (!(c->flags & CHAN_CLOSE_SENT)) {
	chan_send_close2(c);
	}
	if ((c->flags & CHAN_CLOSE_SENT) &&
	(c->flags & CHAN_CLOSE_RCVD)) {
	debug("channel %d: is dead", c->self);
	return 1;
	}
	}
	return 0;
	}

	void
	chan_init_iostates(Channel *c)
	{
	c->ostate = CHAN_OUTPUT_OPEN;
	c->istate = CHAN_INPUT_OPEN;
	c->flags = 0;
	}

	/* init */
	void
	chan_init(void)
	{
	if (compat20) {
	chan_rcvd_oclose = chan_rcvd_oclose2;
	chan_read_failed = chan_read_failed_12;
	chan_ibuf_empty = chan_ibuf_empty2;

	chan_rcvd_ieof = chan_rcvd_ieof2;
	chan_write_failed = chan_write_failed2;
	chan_obuf_empty = chan_obuf_empty2;
	} else {
	chan_rcvd_oclose = chan_rcvd_oclose1;
	chan_read_failed = chan_read_failed_12;
	chan_ibuf_empty = chan_ibuf_empty1;

	chan_rcvd_ieof = chan_rcvd_ieof1;
	chan_write_failed = chan_write_failed1;
	chan_obuf_empty = chan_obuf_empty1;
	}
	}

	/* helper */
	static void
	chan_shutdown_write(Channel *c)
	{
	buffer_consume(&c->output, buffer_len(&c->output));
	if (compat20 && c->type == SSH_CHANNEL_LARVAL)
	return;
	/* shutdown failure is allowed if write failed already */
	debug("channel %d: close_write", c->self);
	if (c->sock != -1) {
	if (shutdown(c->sock, SHUT_WR) < 0)
	debug("channel %d: chan_shutdown_write: "
	"shutdown() failed for fd%d: %.100s",
	c->self, c->sock, strerror(errno));
	} else {
	if (close(c->wfd) < 0)
	log("channel %d: chan_shutdown_write: "
	"close() failed for fd%d: %.100s",
	c->self, c->wfd, strerror(errno));
	c->wfd = -1;
	}
	}
	static void
	chan_shutdown_read(Channel *c)
	{
	if (compat20 && c->type == SSH_CHANNEL_LARVAL)
	return;
	debug("channel %d: close_read", c->self);
	if (c->sock != -1) {
	/*
	* shutdown(sock, SHUT_READ) may return ENOTCONN if the
	* write side has been closed already. (bug on Linux)
	* HP-UX will return EINVAL.
	*/
	if (shutdown(c->sock, SHUT_RD) < 0
	&& (errno != ENOTCONN && errno != EINVAL))
	error("channel %d: chan_shutdown_read: "
	"shutdown() failed for fd%d [i%d o%d]: %.100s",
	c->self, c->sock, c->istate, c->ostate,
	strerror(errno));
	} else {
	if (close(c->rfd) < 0)
	log("channel %d: chan_shutdown_read: "
	"close() failed for fd%d: %.100s",
	c->self, c->rfd, strerror(errno));
	c->rfd = -1;
	}
	}