bridge_softmix.c: Fix crash if could not allocate the dsp.

Fix off nominal crash where we could not setup the channel to process
frames for the softmix bridge technology because of allocation failure.

Change-Id: Ic307a8386e46bf551e48fcd1eb97276714d56372

bridges/bridge_softmix.c

@@ -357,6 +357,7 @@ static void set_softmix_bridge_data(int rate, int interval, struct ast_bridge_ch
 {
 	struct softmix_channel *sc = bridge_channel->tech_pvt;
 	struct ast_format *slin_format;
+	int setup_fail;
 
 	slin_format = ast_format_cache_get_slin_by_rate(rate);
 
@@ -386,17 +387,24 @@ static void set_softmix_bridge_data(int rate, int interval, struct ast_bridge_ch
 	sc->read_slin_format = slin_format;
 
 	/* Setup smoother */
-	ast_slinfactory_init_with_format(&sc->factory, slin_format);
+	setup_fail = ast_slinfactory_init_with_format(&sc->factory, slin_format);
 
 	/* set new read and write formats on channel. */
 	ast_channel_lock(bridge_channel->chan);
-	ast_set_read_format_path(bridge_channel->chan,
+	setup_fail |= ast_set_read_format_path(bridge_channel->chan,
 		ast_channel_rawreadformat(bridge_channel->chan), slin_format);
 	ast_channel_unlock(bridge_channel->chan);
-	ast_set_write_format(bridge_channel->chan, slin_format);
+	setup_fail |= ast_set_write_format(bridge_channel->chan, slin_format);
 
 	/* set up new DSP.  This is on the read side only right before the read frame enters the smoother.  */
 	sc->dsp = ast_dsp_new_with_rate(rate);
+	if (setup_fail || !sc->dsp) {
+		/* Bad news.  Could not setup the channel for softmix. */
+		ast_mutex_unlock(&sc->lock);
+		ast_bridge_channel_leave_bridge(bridge_channel, BRIDGE_CHANNEL_STATE_END, 0);
+		return;
+	}
+
 	/* we want to aggressively detect silence to avoid feedback */
 	if (bridge_channel->tech_args.talking_threshold) {
 		ast_dsp_set_threshold(sc->dsp, bridge_channel->tech_args.talking_threshold);
@@ -616,7 +624,10 @@ static void softmix_bridge_write_voice(struct ast_bridge *bridge, struct ast_bri
 		ast_channel_unlock(bridge_channel->chan);
 	}
 
-	ast_dsp_silence_with_energy(sc->dsp, frame, &totalsilence, &cur_energy);
+	/* The channel will be leaving soon if there is no dsp. */
+	if (sc->dsp) {
+		ast_dsp_silence_with_energy(sc->dsp, frame, &totalsilence, &cur_energy);
+	}
 
 	if (bridge->softmix.video_mode.mode == AST_BRIDGE_VIDEO_MODE_TALKER_SRC) {
 		int cur_slot = sc->video_talker.energy_history_cur_slot;