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Fix crashes in ast_rtcp_write().

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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show a crash in ast_rtcp_write() where it appears that the RTP instance is no
longer valid.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/1.8@336877 65c4cc65-6c06-0410-ace0-fbb531ad65f3
This commit is contained in:
Russell Bryant
2011-09-20 00:56:20 +00:00
parent 0628cce193
commit df4d47dff4
1 changed files with 42 additions and 13 deletions
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55
res/res_rtp_asterisk.c
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@@ -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");
}
}
}
@@ -2177,7 +2196,12 @@ 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;
@@ -2591,9 +2615,14 @@ 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) {
AST_SCHED_DEL(rtp->sched, rtp->rtcp->schedid);
if (rtp->rtcp && rtp->rtcp->schedid > 0) {
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);