Index: channels/chan_sip.c
===================================================================
RCS file: /usr/cvsroot/asterisk/channels/chan_sip.c,v
retrieving revision 1.784
diff -u -r1.784 chan_sip.c
--- channels/chan_sip.c	20 Jul 2005 17:05:18 -0000	1.784
+++ channels/chan_sip.c	23 Jul 2005 16:29:00 -0000
@@ -2183,12 +2183,13 @@
 	int needcancel = 0;
 	struct ast_flags locflags = {0};
 
-	if (option_debug)
-		ast_log(LOG_DEBUG, "sip_hangup(%s)\n", ast->name);
 	if (!p) {
 		ast_log(LOG_DEBUG, "Asked to hangup channel not connected\n");
 		return 0;
 	}
+	if (option_debug)
+		ast_log(LOG_DEBUG, "Hangup call %s, SIP callid %s)\n", ast->name, p->callid);
+
 	ast_mutex_lock(&p->lock);
 #ifdef OSP_SUPPORT
 	if ((p->osphandle > -1) && (ast->_state == AST_STATE_UP)) {
@@ -2204,12 +2205,14 @@
 	}
 	/* Determine how to disconnect */
 	if (p->owner != ast) {
-		ast_log(LOG_WARNING, "Huh?  We aren't the owner?\n");
+		ast_log(LOG_WARNING, "Huh?  We aren't the owner? Can't hangup call.\n");
 		ast_mutex_unlock(&p->lock);
 		return 0;
 	}
+	/* If the call is not UP, we need to send CANCEL instead of BYE */
 	if (ast->_state != AST_STATE_UP)
 		needcancel = 1;
+
 	/* Disconnect */
 	p = ast->tech_pvt;
 	if (p->vad) {
@@ -2224,9 +2227,10 @@
 	ast_update_use_count();
 
 	ast_set_flag(&locflags, SIP_NEEDDESTROY);	
+
 	/* Start the process if it's not already started */
 	if (!ast_test_flag(p, SIP_ALREADYGONE) && !ast_strlen_zero(p->initreq.data)) {
-		if (needcancel) {
+		if (needcancel) {	/* Outgoing call, not up */
 			if (ast_test_flag(p, SIP_OUTGOING)) {
 				transmit_request_with_auth(p, SIP_CANCEL, p->ocseq, 1, 0);
 				/* Actually don't destroy us yet, wait for the 487 on our original 
@@ -2243,14 +2247,14 @@
 						update_user_counter(p, INC_IN_USE);
 					}
 				}
-			} else {
+			} else {	/* Incoming call, not up */
 				char *res;
 				if (ast->hangupcause && ((res = hangup_cause2sip(ast->hangupcause)))) {
 					transmit_response_reliable(p, res, &p->initreq, 1);
 				} else 
 					transmit_response_reliable(p, "403 Forbidden", &p->initreq, 1);
 			}
-		} else {
+		} else {	/* Call is in UP state, send BYE */
 			if (!p->pendinginvite) {
 				/* Send a hangup */
 				transmit_request_with_auth(p, SIP_BYE, 0, 1, 1);
@@ -3809,6 +3813,11 @@
 	}
 	respprep(&resp, p, msg, req);
 	add_header(&resp, "Content-Length", "0");
+	/* If we are cancelling an incoming invite for some reason, add information
+		about the reason why we are doing this in clear text */
+	if (p->owner && p->owner->hangupcause) {
+		add_header(&resp, "X-asterisk-hangupcause:", ast_cause2str(p->owner->hangupcause));
+	}
 	add_blank_header(&resp);
 	return send_response(p, &resp, reliable, seqno);
 }
@@ -5010,14 +5019,20 @@
 	struct sip_request resp;
 
 	reqprep(&resp, p, sipmethod, seqno, newbranch);
-	if (*p->realm)
-	{
+	if (*p->realm) {
 		char digest[1024];
 
 		memset(digest, 0, sizeof(digest));
 		build_reply_digest(p, sipmethod, digest, sizeof(digest));
 		add_header(&resp, "Proxy-Authorization", digest);
 	}
+	/* If we are hanging up and know a cause for that, send it in clear text to make
+		debugging easier. */
+	if (sipmethod == SIP_BYE) {
+		if (p->owner && p->owner->hangupcause)	{
+			add_header(&resp, "X-asterisk-hangupcause:", ast_cause2str(p->owner->hangupcause));
+		}
+	}
 
 	add_header(&resp, "Content-Length", "0");
 	add_blank_header(&resp);