Merged revisions 336877 via svnmerge from

https://origsvn.digium.com/svn/asterisk/branches/1.8

........
  r336877 | russell | 2011-09-19 19:56:20 -0500 (Mon, 19 Sep 2011) | 36 lines
  
  Fix crashes in ast_rtcp_write().
  
  This patch addresses crashes related to RTCP handling.  The backtraces just
  show a crash in ast_rtcp_write() where it appears that the RTP instance is no
  longer valid.  There is a race condition with scheduled RTCP transmissions and
  the destruction of the RTP instance.  This patch utilizes the fact that
  ast_rtp_instance is a reference counted object and ensures that it will not get
  destroyed while a reference is still around due to scheduled RTCP
  transmissions.
  
  RTCP transmissions are scheduled and executed from the chan_sip scheduler
  context.  This scheduler context is processed in the SIP monitor thread.  The
  destruction of an RTP instance occurs when the associated sip_pvt gets
  destroyed (which happens when the sip_pvt reference count reaches 0).  However,
  the SIP monitor thread is not the only thread that can cause a sip_pvt to get
  destroyed.  The sip_hangup function, executed from a channel thread, also
  decrements the reference count on a sip_pvt and could cause it to get
  destroyed.
  
  While this is being changed anyway, the patch also removes calling
  ast_sched_del() from within the RTCP scheduler callback.  It's not helpful.
  Simply returning 0 prevents the callback from being rescheduled.
  
  (closes issue ASTERISK-18570)
  
  Related issues that look like they are the same problem:
  
  (issue ASTERISK-17560)
  (issue ASTERISK-15406)
  (issue ASTERISK-15257)
  (issue ASTERISK-13334)
  (issue ASTERISK-9977)
  (issue ASTERISK-9716)
  
  Review: https://reviewboard.asterisk.org/r/1444/
........


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/10@336878 65c4cc65-6c06-0410-ace0-fbb531ad65f3

res/res_rtp_asterisk.c

@@ -522,7 +522,11 @@ static int ast_rtp_destroy(struct ast_rtp_instance *instance)
 
 	/* Destroy RTCP if it was being used */
 	if (rtp->rtcp) {
-		AST_SCHED_DEL(rtp->sched, rtp->rtcp->schedid);
+		/*
+		 * It is not possible for there to be an active RTCP scheduler
+		 * entry at this point since it holds a reference to the
+		 * RTP instance while it's active.
+		 */
 		close(rtp->rtcp->s);
 		ast_free(rtp->rtcp);
 	}
@@ -830,8 +834,9 @@ static int ast_rtcp_write_rr(struct ast_rtp_instance *instance)
 		return 0;
 
 	if (ast_sockaddr_isnull(&rtp->rtcp->them)) {
-		ast_log(LOG_ERROR, "RTCP RR transmission error, rtcp halted\n");
+		/*
-		AST_SCHED_DEL(rtp->sched, rtp->rtcp->schedid);
+		 * RTCP was stopped.
+		 */
 		return 0;
 	}
 
@@ -886,8 +891,6 @@ static int ast_rtcp_write_rr(struct ast_rtp_instance *instance)
 
 	if (res < 0) {
 		ast_log(LOG_ERROR, "RTCP RR transmission error, rtcp halted: %s\n",strerror(errno));
-		/* Remove the scheduler */
-		AST_SCHED_DEL(rtp->sched, rtp->rtcp->schedid);
 		return 0;
 	}
 
@@ -932,8 +935,9 @@ static int ast_rtcp_write_sr(struct ast_rtp_instance *instance)
 		return 0;
 
 	if (ast_sockaddr_isnull(&rtp->rtcp->them)) {  /* This'll stop rtcp for this rtp session */
-		ast_verbose("RTCP SR transmission error, rtcp halted\n");
+		/*
-		AST_SCHED_DEL(rtp->sched, rtp->rtcp->schedid);
+		 * RTCP was stopped.
+		 */
 		return 0;
 	}
 
@@ -985,7 +989,6 @@ static int ast_rtcp_write_sr(struct ast_rtp_instance *instance)
 		ast_log(LOG_ERROR, "RTCP SR transmission error to %s, rtcp halted %s\n",
 			ast_sockaddr_stringify(&rtp->rtcp->them),
 			strerror(errno));
-		AST_SCHED_DEL(rtp->sched, rtp->rtcp->schedid);
 		return 0;
 	}
 
@@ -1044,13 +1047,24 @@ static int ast_rtcp_write(const void *data)
 	struct ast_rtp *rtp = ast_rtp_instance_get_data(instance);
 	int res;
 
-	if (!rtp || !rtp->rtcp)
+	if (!rtp || !rtp->rtcp || rtp->rtcp->schedid == -1) {
+		ao2_ref(instance, -1);
 		return 0;
+	}
 
-	if (rtp->txcount > rtp->rtcp->lastsrtxcount)
+	if (rtp->txcount > rtp->rtcp->lastsrtxcount) {
 		res = ast_rtcp_write_sr(instance);
-	else
+	} else {
 		res = ast_rtcp_write_rr(instance);
+	}
+
+	if (!res) {
+		/* 
+		 * Not being rescheduled.
+		 */
+		ao2_ref(instance, -1);
+		rtp->rtcp->schedid = -1;
+	}
 
 	return res;
 }
@@ -1162,7 +1176,12 @@ static int ast_rtp_raw_write(struct ast_rtp_instance *instance, struct ast_frame
 
 			if (rtp->rtcp && rtp->rtcp->schedid < 1) {
 				ast_debug(1, "Starting RTCP transmission on RTP instance '%p'\n", instance);
+				ao2_ref(instance, +1);
 				rtp->rtcp->schedid = ast_sched_add(rtp->sched, ast_rtcp_calc_interval(rtp), ast_rtcp_write, instance);
+				if (rtp->rtcp->schedid < 0) {
+					ao2_ref(instance, -1);
+					ast_log(LOG_WARNING, "scheduling RTCP transmission failed.\n");
+				}
 			}
 		}
 
@@ -2180,7 +2199,12 @@ static struct ast_frame *ast_rtp_read(struct ast_rtp_instance *instance, int rtc
 	/* Do not schedule RR if RTCP isn't run */
 	if (rtp->rtcp && !ast_sockaddr_isnull(&rtp->rtcp->them) && rtp->rtcp->schedid < 1) {
 		/* Schedule transmission of Receiver Report */
+		ao2_ref(instance, +1);
 		rtp->rtcp->schedid = ast_sched_add(rtp->sched, ast_rtcp_calc_interval(rtp), ast_rtcp_write, instance);
+		if (rtp->rtcp->schedid < 0) {
+			ao2_ref(instance, -1);
+			ast_log(LOG_WARNING, "scheduling RTCP transmission failed.\n");
+		}
 	}
 	if ((int)rtp->lastrxseqno - (int)seqno  > 100) /* if so it would indicate that the sender cycled; allow for misordering */
 		rtp->cycles += RTP_SEQ_MOD;
@@ -2592,9 +2616,14 @@ static void ast_rtp_stop(struct ast_rtp_instance *instance)
 	struct ast_rtp *rtp = ast_rtp_instance_get_data(instance);
 	struct ast_sockaddr addr = { {0,} };
 
-	if (rtp->rtcp) {
+	if (rtp->rtcp && rtp->rtcp->schedid > 0) {
-		AST_SCHED_DEL(rtp->sched, rtp->rtcp->schedid);
+		if (!ast_sched_del(rtp->sched, rtp->rtcp->schedid)) {
+			/* successfully cancelled scheduler entry. */
+			ao2_ref(instance, -1);
+		}
+		rtp->rtcp->schedid = -1;
 	}
+
 	if (rtp->red) {
 		AST_SCHED_DEL(rtp->sched, rtp->red->schedid);
 		free(rtp->red);