[asterisk-bugs] [Asterisk 0013749]: IAX2 storm (type 4, subtype 20: AST_CONTROL_SRCUPDATE)

[Asterisk Bug Tracker]

A NOTE has been added to this issue. 
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http://bugs.digium.com/view.php?id=13749 
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Reported By:                adiemus
Assigned To:                
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Project:                    Asterisk
Issue ID:                   13749
Category:                   Channels/chan_iax2
Reproducibility:            always
Severity:                   major
Priority:                   normal
Status:                     acknowledged
Asterisk Version:           1.4.22 
SVN Branch (only for SVN checkouts, not tarball releases): N/A 
SVN Revision (number only!):  
Disclaimer on File?:        N/A 
Request Review:              
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Date Submitted:             2008-10-20 17:46 CDT
Last Modified:              2008-11-27 12:17 CST
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Summary:                    IAX2 storm (type 4, subtype 20:
AST_CONTROL_SRCUPDATE)
Description: 
This is a rather odd issue to describe.

In simplest terms, I have a server connected via IAX2 to another server. 
The configuration had been working fine through at least 1.4.18.  However,
between then an 1.4.21.2, this issue began occuring for all calls from
server A to server B.  (But oddly, not for calls from B->A)  The issue
persists in 1.4.22.

When a call is placed through server A to server B via IAX2, server A
sends a torrent of retransmitted packets right after the initial call
setup.  This storm eats up more than 20 Mbit and is reproducible for every
call from server A to server B.  If I replicate the configuration of server
B onto server C, the behavior remains the same.  Calls from server A to
server C show the same "packet storm" bug.

I have complete pcap captures of both sides of the connection, if that's
useful.  However, the short overview from server A's perspective is:

A -> B NEW
B -> A AUTHREQ
A -> B AUTHREP
B -> A ACCEPT
A -> B ACK
B -> A ANSWER
A -> B ACK
A -> B CONTROL (subclass = 20, AST_CONTROL_SRCUPDATE)
A -> B CONTROL (subclass = 20, AST_CONTROL_SRCUPDATE) [retrans]
<storm of identical, retransmitted packets>

This is a serious issue for us as the storm is enough to saturate the
internet connections both of LAN A and LAN B.  (Packet rate is into the
tens or hundreds of thousands per second)

I'm happy to provide more information, but I don't know what else would be
useful.

The iax.conf entry for server B on server A looks like:
[serverB]
type=user
auth=md5
secret=redacted
transfer=no
context=from-serverB
jitterbuffer=no

[serverB]
type=peer
auth=md5
secret=redacted
username=serverA
transfer=no
host=dynamic
disallow=all
allow=gsm
jitterbuffer=no

The config for serverA on serverB:
register => serverB:redacted at serverA.fqdn

[serverA]
type=user
auth=md5
secret=redacted
transfer=no
context=from-serverA
jitterbuffer=yes

[serverA]
type=peer
auth=md5
secret=redacted
username=serverB
host=serverA.fqdn
jitterbuffer=yes
trunk=no
trunktimestamps=no
disallow=all
allow=gsm

In the interim, I'll see if I can do a binary search to find in what
version this behavior started.
====================================================================== 

---------------------------------------------------------------------- 
 (0095579) sim (reporter) - 2008-11-27 12:17
 http://bugs.digium.com/view.php?id=13749#c95579 
---------------------------------------------------------------------- 
Ok, this issue can be reproduced very easily with a very basic dialplan. 
This particular dialplan used to work in older versions, because I used it
to try to load-test IAX previously when we were debugging the last VNAK
storming problem.

Steps to reproduce:

Set up two Asterisk 1.4.22 instances and peer them via IAX, with defaults.
 It happens with transfer=no or transfer=yes.

Install this dialplan, changing the Dial() on each box to reach the other
box:

[default]
exten => _1XXX,1,Answer
exten => _1XXX,n,Wait(.02)
exten => _1XXX,n,Dial(IAX2/t3/$[${EXTEN} - 1]@default)
exten => _1000,1,Answer
exten => _1000,n,SayDigits(123)
exten => _1000,n,Echo

(The Wait() or SayDigits() may not really be necessary, as it doesn't seem
to even get to extension 1000.)