res_pjsip_t38.c: Fix crash by ignoring 1xx messages.

If we initiated a T.38 reINVITE, we would crash if we received any other
1xx response message except 100 if it were followed by a 200 response.

* Made ignore any 1xx response so we do not close out the T.38 negotiation
too early.  For good measure we'll now accept any 2xx response as
acceptance of the reINVITE T.38 offer.

ASTERISK-27944

Change-Id: I0ca88aae708d091db7335af73f41035a212adff4

res/res_pjsip_t38.c

@@ -251,8 +251,6 @@ static struct t38_state *t38_state_get_or_alloc(struct ast_sip_session *session)
 	/* This will get bumped up before scheduling */
 	pj_timer_entry_init(&state->timer, 0, session, t38_automatic_reject_timer_cb);
 
-	datastore->data = state;
-
 	return state;
 }
 
@@ -297,18 +295,21 @@ static int t38_reinvite_response_cb(struct ast_sip_session *session, pjsip_rx_da
 	struct t38_state *state;
 	struct ast_sip_session_media *session_media = NULL;
 
-	if (status.code == 100) {
+	if (status.code / 100 <= 1) {
+		/* Ignore any non-final responses (1xx) */
 		return 0;
 	}
 
 	state = t38_state_get_or_alloc(session);
 	if (!session->channel || !state) {
-		ast_log(LOG_WARNING, "Received response to T.38 re-invite on '%s' but state unavailable\n",
+		ast_log(LOG_WARNING, "Received %d response to T.38 re-invite on '%s' but state unavailable\n",
+			status.code,
 			session->channel ? ast_channel_name(session->channel) : "unknown channel");
 		return 0;
 	}
 
-	if (status.code == 200) {
+	if (status.code / 100 == 2) {
+		/* Accept any 2xx response as successfully negotiated */
 		int index;
 
 		session_media = session->active_media_state->default_session[AST_MEDIA_TYPE_IMAGE];