Index: channels/chan_sip.c
===================================================================
--- channels/chan_sip.c	(revision 143269)
+++ channels/chan_sip.c	(working copy)
@@ -2076,6 +2076,9 @@
 	}
 }
 
+/* adding this for tracking */
+int hangfix_count = 0;
+
 /*! \brief Kill a SIP dialog (called by scheduler) */
 static int __sip_autodestruct(const void *data)
 {
@@ -2092,10 +2095,14 @@
 	}
 
 	/* If there are packets still waiting for delivery, delay the destruction */
-	if (p->packets) {
+	if (p->packets && !ast_test_flag(&p->flags[0], SIP_NEEDDESTROY)) {
 		if (option_debug > 2)
 			ast_log(LOG_DEBUG, "Re-scheduled destruction of SIP call %s\n", p->callid ? p->callid : "<unknown>");
 		append_history(p, "ReliableXmit", "timeout");
+		if (p->method == SIP_CANCEL || p->method == SIP_BYE) {
+			ast_set_flag(&p->flags[0], SIP_NEEDDESTROY);
+			hangfix_count++;
+		}
 		return 10000;
 	}
 
@@ -10028,7 +10035,16 @@
 	"\r\n", total, idtext);
 	return 0;
 }
+/*! \brief CLI Show Hangfix command; shows how many times a 'software safety valve' 
+ * saved a channel from being hung
+ * */
 
+static int sip_show_hangfix(int fd, int argc, char *argv[])
+{
+	ast_cli(fd,"The NEEDDESTROY flag has been set on %d channels so far; they probably would have hung otherwise.\n", hangfix_count);
+	return RESULT_SUCCESS;
+}
+
 /*! \brief  CLI Show Peers command */
 static int sip_show_peers(int fd, int argc, char *argv[])
 {
@@ -11792,6 +11808,10 @@
 "Usage: sip show history <channel>\n"
 "       Provides detailed dialog history on a given SIP channel.\n";
 
+static char show_hangfix_usage[] = 
+"Usage: sip show hangfix\n"
+"       Shows how many times a code patch allowed zombie channels to taste sweet death.\n";
+
 static char show_peers_usage[] = 
 "Usage: sip show peers [like <pattern>]\n"
 "       Lists all known SIP peers.\n"
@@ -18476,6 +18496,10 @@
 	sip_show_objects, "List all SIP object allocations",
 	show_objects_usage },
 
+	{ { "sip", "show", "hangfix", NULL },
+	sip_show_hangfix, "Show how many times a patch allowed a zombie channel to die",
+	show_hangfix_usage },
+
 	{ { "sip", "show", "peers", NULL },
 	sip_show_peers, "List defined SIP peers",
 	show_peers_usage },