From 434e51f69d2d89b1fedaa7ee48cbc72dcf0b285d Mon Sep 17 00:00:00 2001
From: Bram Matthys <syzop@vulnscan.org>
Date: Wed, 13 Jan 2016 10:30:07 +0100
Subject: [PATCH] Fix crash when listen block was removed while it had
 connected clients on that port. Reported by AnGeLoCaDuTo (#4544).

There were a few flaws in the code: 1) it should close the listener on /rehash,
shouldnt't matter if there are clients or not, 2) then there was a bug where it
would properly close the listener but it would be re-opened by add_listener2.

Also added a "IRCd no longer listening on .." message if you remove a listen block.
---
 src/s_bsd.c  | 20 +++++++++++++-------
 src/s_conf.c |  3 ++-
 2 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/src/s_bsd.c b/src/s_bsd.c
index 35cf1ac25..7da04df8b 100644
--- a/src/s_bsd.c
+++ b/src/s_bsd.c
@@ -450,12 +450,20 @@ int add_listener2(ConfigItem_listen *conf)
 /*
  * close_listeners
  *
- * Close and free all clients which are marked as having their socket open
- * and in a state where they can accept connections.
+ * Close the listener. Note that this won't *free* the listen block, it
+ * just makes it so no new clients are accepted (and marks the listener
+ * as "not bound").
  */
 void close_listener(ConfigItem_listen *listener)
 {
-	fd_close(listener->fd);
+	if (listener->fd >= 0)
+	{
+		ircd_log(LOG_ERROR, "IRCd no longer listening on %s:%d (%s)%s",
+			listener->ip, listener->port,
+			listener->ipv6 ? "IPv6" : "IPv4",
+			listener->options & LISTENER_SSL ? " (SSL)" : "");
+		fd_close(listener->fd);
+	}
 
 	listener->options &= ~LISTENER_BOUND;
 	listener->fd = -1;
@@ -466,14 +474,12 @@ void close_listeners(void)
 	aClient *cptr;
 	ConfigItem_listen *aconf, *aconf_next;
 
-	/*
-	 * close all 'extra' listening ports we have
-	 */
+	/* close all 'extra' listening ports we have */
 	for (aconf = conf_listen; aconf != NULL; aconf = aconf_next)
 	{
 		aconf_next = (ConfigItem_listen *) aconf->next;
 
-		if (aconf->flag.temporary && (aconf->clients == 0))
+		if (aconf->flag.temporary)
 			close_listener(aconf);
 	}
 }
diff --git a/src/s_conf.c b/src/s_conf.c
index 0d595edce..c22315bb7 100644
--- a/src/s_conf.c
+++ b/src/s_conf.c
@@ -8108,7 +8108,8 @@ void start_listeners(void)
 
 	for (listenptr = conf_listen; listenptr; listenptr = (ConfigItem_listen *) listenptr->next)
 	{
-		if (!(listenptr->options & LISTENER_BOUND))
+		/* Try to bind to any ports that are not yet bound and not marked as temporary */
+		if (!(listenptr->options & LISTENER_BOUND) && !listenptr->flag.temporary)
 		{
 			if (add_listener2(listenptr) == -1)
 			{