Repair ability of SendFAX/ReceiveFAX to respond to T.38 switchover.

Recent changes in T.38 negotiation in Asterisk caused these applications to
not respond when the other endpoint initiated a switchover to T.38; this
resulted in the T.38 switchover failing, and the FAX attempt to be made
using an audio connection, instead of T.38 (which would usually cause the
FAX to fail completely).

This patch corrects this problem, and the applications will now correctly
respond to the T.38 switchover request. In addition, the response will include
the appopriate T.38 session parameters based on what the other end offered
and what our end is capable of.

(closes issue #14849)
Reported by: afosorio


git-svn-id: http://svn.digium.com/svn/asterisk/trunk@205696 f38db490-d61c-443f-a65b-d21fe96a405b

1 files changed, 19 insertions, 2 deletions

diff --git a/apps/app_fax.c b/apps/app_fax.c
index 7c35d84a6..815bb84f2 100644
--- a/apps/app_fax.c
+++ b/apps/app_fax.c
@@ -459,7 +459,7 @@ static int transmit_audio(fax_session *s)
 										 .version = 0,
 										 .max_datagram = 400,
 										 .rate = AST_T38_RATE_9600,
-										 .rate_management = AST_T38_RATE_MANAGEMENT_TRANSFERED_TCF,
+										 .rate_management = AST_T38_RATE_MANAGEMENT_TRANSFERRED_TCF,
 										 .fill_bit_removal = 1,
 										 .transcoding_mmr = 1,
 				};
@@ -476,7 +476,6 @@ static int transmit_audio(fax_session *s)
 		   that a frame in old format was already queued before we set chanel format
 		   to slinear so it will still be received by ast_read */
 		if (inf->frametype == AST_FRAME_VOICE && inf->subclass == AST_FORMAT_SLINEAR) {
-
 			if (fax_rx(&fax, inf->data.ptr, inf->samples) < 0) {
 				/* I know fax_rx never returns errors. The check here is for good style only */
 				ast_log(LOG_WARNING, "fax_rx returned error\n");
@@ -497,6 +496,24 @@ static int transmit_audio(fax_session *s)
 				ast_debug(1, "T38 negotiated, finishing audio loop\n");
 				res = 1;
 				break;
+			} else if (parameters->request_response == AST_T38_REQUEST_NEGOTIATE) {
+				if (parameters->version > 0) {
+					/* Only T.38 Version 0 is supported at this time */
+					parameters->version = 0;
+				}
+				if (parameters->max_datagram > 400) {
+					/* Limit incoming datagram size to our default */
+					/* TODO: this need to come from the udptl stack, not be hardcoded */
+					parameters->max_datagram = 400;
+				}
+				/* we only support bit rates up to 9.6kbps */
+				parameters->rate = AST_T38_RATE_9600;
+				ast_indicate_data(s->chan, AST_CONTROL_T38_PARAMETERS, parameters, sizeof(*parameters));
+				/* T38 switchover completed */
+				s->t38parameters = *parameters;
+				ast_debug(1, "T38 negotiated, finishing audio loop\n");
+				res = 1;
+				break;
 			}
 		}