SSH connection hanging on logout

[John Bowman]

Here is a new version of the hang-on-exit patch, which:

1. fixes the hang-on-exit bug (without data loss);
2. does not exit if there are unterminated X applications;
3. exits the session when all X applications have closed.

Of these three tests, Openssh-2.9p1 only passes the second one. The
third one is another type of hanging bug in Openssh, as is demonstrated by
the following test:

ssh host
xterm -e sleep 20 &
exit

Even after the xsession terminates, the ssh session is left hanging forever.
The correct behaviour is to wait 20 seconds for the X application to close
and then exit.

-- John Bowman

University of Alberta
http://www.math.ualberta.ca/~bowman


diff -ur openssh-2.9p1/channels.c openssh-2.9p1J/channels.c
--- openssh-2.9p1/channels.c	Tue Apr 17 12:14:35 2001
+++ openssh-2.9p1J/channels.c	Mon May 14 20:51:14 2001
@@ -1137,6 +1137,10 @@
 			continue;
 		if (ftab[c->type] == NULL)
 			continue;
+		if(c->type == SSH_CHANNEL_OPEN && c->rfd == -1) {
+		  c->type = SSH_CHANNEL_FREE;
+		  continue;
+		}
 		(*ftab[c->type])(c, readset, writeset);
 		if (chan_is_dead(c)) {
 			/*
@@ -1639,6 +1643,47 @@
 	for (i = 0; i < channels_alloc; i++)
 		if (channels[i].type != SSH_CHANNEL_FREE)
 			channel_close_fds(&channels[i]);
+}
+
+/* Returns true if session is inactive. */
+
+int
+channel_inactive_session()
+{
+	u_int i;
+	if(channels_alloc == 0) return 0;
+	
+	for (i = 0; i < channels_alloc; i++) {
+		switch (channels[i].type) {
+		case SSH_CHANNEL_FREE:
+		case SSH_CHANNEL_X11_LISTENER:
+		case SSH_CHANNEL_CLOSED:
+			break;
+		case SSH_CHANNEL_PORT_LISTENER:
+		case SSH_CHANNEL_RPORT_LISTENER:
+		case SSH_CHANNEL_AUTH_SOCKET:
+		case SSH_CHANNEL_DYNAMIC:
+		case SSH_CHANNEL_CONNECTING: 	/* XXX ??? */
+			return 0;
+		case SSH_CHANNEL_LARVAL:
+			if (!compat20)
+				fatal("cannot happen: SSH_CHANNEL_LARVAL");
+			return 0;
+		case SSH_CHANNEL_OPENING:
+		case SSH_CHANNEL_OPEN:
+		case SSH_CHANNEL_X11_OPEN:
+			return 0;
+		case SSH_CHANNEL_INPUT_DRAINING:
+		case SSH_CHANNEL_OUTPUT_DRAINING:
+			if (!compat13)
+				fatal("cannot happen: OUT_DRAIN");
+			return 0;
+		default:
+			fatal("channel_inactive_session: bad channel type %d", channels[i].type);
+			/* NOTREACHED */
+		}
+	}
+	return 1;
 }
 
 /* Returns true if any channel is still open. */
diff -ur openssh-2.9p1/channels.h openssh-2.9p1J/channels.h
--- openssh-2.9p1/channels.h	Fri Apr 13 17:28:02 2001
+++ openssh-2.9p1J/channels.h	Mon May 14 20:51:14 2001
@@ -197,6 +197,9 @@
  */
 void    channel_close_all(void);
 
+/* Returns true if session is inactive. */
+int     channel_inactive_session();
+  
 /* Returns true if there is still an open channel over the connection. */
 int     channel_still_open(void);
 
diff -ur openssh-2.9p1/clientloop.c openssh-2.9p1J/clientloop.c
--- openssh-2.9p1/clientloop.c	Fri Apr 20 06:50:51 2001
+++ openssh-2.9p1J/clientloop.c	Mon May 14 20:51:14 2001
@@ -440,9 +440,13 @@
 		len = read(connection_in, buf, sizeof(buf));
 		if (len == 0) {
 			/* Received EOF.  The remote host has closed the connection. */
-			snprintf(buf, sizeof buf, "Connection to %.300s closed by remote host.\r\n",
-				 host);
-			buffer_append(&stderr_buffer, buf, strlen(buf));
+/* 
+ * This message duplicates the one already in client_loop().
+ *
+ *			snprintf(buf, sizeof buf, "Connection to %.300s closed by remote host.\r\n",
+ *				 host);
+ *			buffer_append(&stderr_buffer, buf, strlen(buf));
+ */			
 			quit_pending = 1;
 			return;
 		}
diff -ur openssh-2.9p1/nchan.c openssh-2.9p1J/nchan.c
--- openssh-2.9p1/nchan.c	Tue Apr  3 07:02:48 2001
+++ openssh-2.9p1J/nchan.c	Mon May 14 20:51:14 2001
@@ -56,7 +56,7 @@
 
 /* helper */
 static void	chan_shutdown_write(Channel *c);
-static void	chan_shutdown_read(Channel *c);
+void		chan_shutdown_read(Channel *c);
 
 /*
  * SSH1 specific implementation of event functions
@@ -479,7 +479,7 @@
 		c->wfd = -1;
 	}
 }
-static void
+void
 chan_shutdown_read(Channel *c)
 {
 	if (compat20 && c->type == SSH_CHANNEL_LARVAL)
diff -ur openssh-2.9p1/nchan.h openssh-2.9p1J/nchan.h
--- openssh-2.9p1/nchan.h	Sun Mar  4 23:16:12 2001
+++ openssh-2.9p1J/nchan.h	Mon May 14 20:51:14 2001
@@ -88,4 +88,5 @@
 
 void    chan_init_iostates(Channel * c);
 void	chan_init(void);
+void	chan_shutdown_read(Channel *c);
 #endif
diff -ur openssh-2.9p1/serverloop.c openssh-2.9p1J/serverloop.c
--- openssh-2.9p1/serverloop.c	Fri Apr 13 17:28:03 2001
+++ openssh-2.9p1J/serverloop.c	Mon May 14 20:51:14 2001
@@ -726,7 +726,7 @@
 		if (!rekeying)
 			channel_after_select(readset, writeset);
 		process_input(readset);
-		if (connection_closed)
+		if (connection_closed || channel_inactive_session())
 			break;
 		process_output(writeset);
 	}
diff -ur openssh-2.9p1/session.c openssh-2.9p1J/session.c
--- openssh-2.9p1/session.c	Wed Apr 18 09:29:34 2001
+++ openssh-2.9p1J/session.c	Mon May 14 20:51:14 2001
@@ -1960,6 +1960,9 @@
 	 */
 	if (c->ostate != CHAN_OUTPUT_CLOSED)
 		chan_write_failed(c);
+	if (c->istate == CHAN_INPUT_OPEN && compat20) {
+  		chan_shutdown_read(c);
+	}
 	s->chanid = -1;
 }