res_rtp_asterisk.c: Fix crash in RTCP DTLS operation.

Occasionally a crash happens when processing the RTCP DTLS timeout
handler.  The RTCP DTLS timeout timer could be left running if we have not
completed the DTLS handshake before we place the call on hold or we
attempt direct media.

* Made ast_rtp_prop_set() stop the RTCP DTLS timer when disabling RTCP.

* Made some sanity tweaks to ast_rtp_prop_set() when switching from
standard RTCP mode to RTCP multiplexed mode.

ASTERISK-26692 #close

Change-Id: If6c64c79129961acfa4b3d63a864e8f6b664acc0

res/res_rtp_asterisk.c

@@ -1721,8 +1721,10 @@ static void ast_rtp_dtls_stop(struct ast_rtp_instance *instance)
 		dtls_srtp_stop_timeout_timer(instance, rtp, 1);
 		ao2_lock(instance);
 
-		if (rtp->rtcp->dtls.ssl && (rtp->rtcp->dtls.ssl != ssl)) {
+		if (rtp->rtcp->dtls.ssl) {
-			SSL_free(rtp->rtcp->dtls.ssl);
+			if (rtp->rtcp->dtls.ssl != ssl) {
+				SSL_free(rtp->rtcp->dtls.ssl);
+			}
 			rtp->rtcp->dtls.ssl = NULL;
 		}
 	}
@@ -5423,14 +5425,14 @@ static void ast_rtp_prop_set(struct ast_rtp_instance *instance, enum ast_rtp_pro
 				 * to activating RTP. It is not until RTP is activated that timers start for RTCP
 				 * transmission
 				 */
-				if (rtp->rtcp->s > -1) {
+				if (rtp->rtcp->s > -1 && rtp->rtcp->s != rtp->s) {
 					close(rtp->rtcp->s);
 				}
 				rtp->rtcp->s = rtp->s;
 				ast_rtp_instance_get_remote_address(instance, &addr);
 				ast_sockaddr_copy(&rtp->rtcp->them, &addr);
 #ifdef HAVE_OPENSSL_SRTP
-				if (rtp->rtcp->dtls.ssl) {
+				if (rtp->rtcp->dtls.ssl && rtp->rtcp->dtls.ssl != rtp->dtls.ssl) {
 					SSL_free(rtp->rtcp->dtls.ssl);
 				}
 				rtp->rtcp->dtls.ssl = rtp->dtls.ssl;
@@ -5438,7 +5440,6 @@ static void ast_rtp_prop_set(struct ast_rtp_instance *instance, enum ast_rtp_pro
 			}
 
 			ast_debug(1, "Setup RTCP on RTP instance '%p'\n", instance);
-			return;
 		} else {
 			if (rtp->rtcp) {
 				if (rtp->rtcp->schedid > -1) {
@@ -5459,6 +5460,10 @@ static void ast_rtp_prop_set(struct ast_rtp_instance *instance, enum ast_rtp_pro
 					close(rtp->rtcp->s);
 				}
 #ifdef HAVE_OPENSSL_SRTP
+				ao2_unlock(instance);
+				dtls_srtp_stop_timeout_timer(instance, rtp, 1);
+				ao2_lock(instance);
+
 				if (rtp->rtcp->dtls.ssl && rtp->rtcp->dtls.ssl != rtp->dtls.ssl) {
 					SSL_free(rtp->rtcp->dtls.ssl);
 				}
@@ -5467,11 +5472,8 @@ static void ast_rtp_prop_set(struct ast_rtp_instance *instance, enum ast_rtp_pro
 				ast_free(rtp->rtcp);
 				rtp->rtcp = NULL;
 			}
-			return;
 		}
 	}
-
-	return;
 }
 
 /*! \pre instance is locked */