Add missing SDES accept routine

When we receive an incoming SDES parameter, we must match them against the
previously sent outgoing SDES parameters, choose the one that matches
what we just received and eliminate all others. This is a no-op if none
were sent previously (original offer).

Issue only appears in a re-invite when the first offered crypto suite is
accepted.

fixes #631

Change-Id: I4991d0aaf0b29c1ba66045ed0e5281fc18c8af2e

daemon/call.c

@@ -1447,7 +1447,7 @@ static void __generate_crypto(const struct sdp_ng_flags *flags, struct call_medi
 			}
 		}
 	}
-	else {
+	else { // OP_ANSWER
 		// we pick the first supported crypto suite
 		struct crypto_params_sdes *cps = cpq->head ? cpq->head->data : NULL;
 		struct crypto_params_sdes *cps_in = cpq_in->head ? cpq_in->head->data : NULL;
@@ -1491,6 +1491,32 @@ static void __generate_crypto(const struct sdp_ng_flags *flags, struct call_medi
 skip_sdes:
 	;
 }
+// for an answer, uses the incoming received list of SDES crypto suites to prune
+// the list of (generated) outgoing crypto suites to contain only the one that was
+// accepted
+static void __sdes_accept(struct call_media *media) {
+	if (!media->sdes_in.length)
+		return;
+	struct crypto_params_sdes *cps_in = media->sdes_in.head->data;
+	GList *l = media->sdes_out.head;
+	while (l) {
+		struct crypto_params_sdes *cps_out = l->data;
+		if (cps_out->params.crypto_suite != cps_in->params.crypto_suite)
+			goto del_next;
+		if (cps_out->tag != cps_in->tag)
+			goto del_next;
+
+		// this one's good
+		l = l->next;
+		continue;
+del_next:
+		// mismatch, prune this one out
+		crypto_params_sdes_free(cps_out);
+		GList *next = l->next;
+		g_queue_delete_link(&media->sdes_out, l);
+		l = next;
+	}
+}
 
 
 static void __disable_streams(struct call_media *media, unsigned int num_ports) {
@@ -1895,8 +1921,10 @@ int monologue_offer_answer(struct call_monologue *other_ml, GQueue *streams,
 			other_media->sdes_in = sp->sdes_params;
 			g_queue_init(&sp->sdes_params);
 
-			if (other_media->sdes_in.length)
+			if (other_media->sdes_in.length) {
 				MEDIA_SET(other_media, SDES);
+				__sdes_accept(other_media);
+			}
 		}
 
 		// codec and RTP payload types handling