Remove automatic switching from T.38 to voice mode in chan_sip.

chan_sip has some code to automatically switch from T.38 mode to voice mode when
a voice frame is written to the channel while it is in T.38 mode; this was
intended to handle the situation when a FAX transmission has ended and the channel
is not yet hung up, but is causing problems at the beginning of FAX sessions as
well when there are still voice frames 'in flight' at the time the T.38 negotiation
completes. This patch removes the automatic switchover, and changes app_fax to
explicitly switch off T.38 mode when the FAX transmission process ends.

(closes issue #16025)
Reported by: jamicque


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@223652 65c4cc65-6c06-0410-ace0-fbb531ad65f3

apps/app_fax.c

@@ -598,6 +598,7 @@ static int transmit_t38(fax_session *s)
 	struct timeval now, start, state_change, last_frame;
 	t30_state_t *t30state;
 	t38_core_state_t *t38state;
+	struct ast_control_t38_parameters t38_parameters = { .request_response = AST_T38_REQUEST_TERMINATE, };
 
 #if SPANDSP_RELEASE_DATE >= 20080725
 	/* for spandsp shaphots 0.0.6 and higher */
@@ -613,7 +614,8 @@ static int transmit_t38(fax_session *s)
 	memset(&t38, 0, sizeof(t38));
 	if (t38_terminal_init(&t38, s->caller_mode, t38_tx_packet_handler, s->chan) == NULL) {
 		ast_log(LOG_WARNING, "Unable to start T.38 termination.\n");
-		return -1;
+		res = -1;
+		goto disable_t38;
 	}
 
 	t38_set_max_datagram_size(t38state, s->t38parameters.max_ifp);
@@ -703,6 +705,57 @@ static int transmit_t38(fax_session *s)
 	t30_terminate(t30state);
 	t38_terminal_release(&t38);
 
+disable_t38:
+	if (ast_channel_get_t38_state(s->chan) == T38_STATE_NEGOTIATED) {
+		if (ast_indicate_data(s->chan, AST_CONTROL_T38_PARAMETERS, &t38_parameters, sizeof(t38_parameters)) == 0) {
+			/* wait up to five seconds for negotiation to complete */
+			unsigned int timeout = 5000;
+			int ms;
+			
+			ast_debug(1, "Shutting down T.38 on %s\n", s->chan->name);
+			while (timeout > 0) {
+				ms = ast_waitfor(s->chan, 1000);
+				if (ms < 0) {
+					ast_log(LOG_WARNING, "something bad happened while channel '%s' was polling.\n", s->chan->name);
+					return -1;
+				}
+				if (!ms) {
+					/* nothing happened */
+					if (timeout > 0) {
+						timeout -= 1000;
+						continue;
+					} else {
+						ast_log(LOG_WARNING, "channel '%s' timed-out during the T.38 shutdown.\n", s->chan->name);
+						break;
+					}
+				}
+				if (!(inf = ast_read(s->chan))) {
+					return -1;
+				}
+				if ((inf->frametype == AST_FRAME_CONTROL) &&
+				    (inf->subclass == AST_CONTROL_T38_PARAMETERS) &&
+				    (inf->datalen == sizeof(t38_parameters))) {
+					struct ast_control_t38_parameters *parameters = inf->data.ptr;
+					
+					switch (parameters->request_response) {
+					case AST_T38_NEGOTIATED:
+						ast_debug(1, "Shut down T.38 on %s\n", s->chan->name);
+						break;
+					case AST_T38_REFUSED:
+						ast_log(LOG_WARNING, "channel '%s' refused to disable T.38\n", s->chan->name);
+						break;
+					default:
+						ast_log(LOG_ERROR, "channel '%s' failed to disable T.38\n", s->chan->name);
+						break;
+					}
+					ast_frfree(inf);
+					break;
+				}
+				ast_frfree(inf);
+			}
+		}
+	}
+
 	return res;
 }
 

channels/chan_sip.c

@@ -6323,8 +6323,7 @@ static int sip_write(struct ast_channel *ast, struct ast_frame *frame)
 						ast_set_flag(&p->flags[0], SIP_PROGRESS_SENT);
 					}
 				} else if (p->t38.state == T38_ENABLED) {
-					change_t38_state(p, T38_DISABLED);
-					transmit_reinvite_with_sdp(p, FALSE, FALSE);
+					/* drop frame, can't sent VOICE frames while in T.38 mode */
 				} else {
 					p->lastrtptx = time(NULL);
 					res = ast_rtp_instance_write(p->rtp, frame);