[Asterisk-code-review] udptl: Don't eat sequence numbers until OK is received (asterisk[certified/11.6])

[Joshua Colp]

Hello Mark Michelson, Anonymous Coward #1000019,

I'd like you to reexamine a change.  Please visit

    https://gerrit.asterisk.org/2870

to look at the new patch set (#4).

Change subject: udptl: Don't eat sequence numbers until OK is received
......................................................................

udptl: Don't eat sequence numbers until OK is received

Scenario:
Local fax -> Asterisk w/ firewall -> Provider -> Remote fax

* Local fax starts rtp call to remote fax
* Remote fax starts t38 call back to local fax.
* Local fax sends t38 no-signal to Asterisk before sending an OK.
* udptl processes the frame and increments the expected sequence number.
* chan_sip drops the frame because the call isn't up so nothing goes out
  the external interface to open the port for incoming packets.
* Local fax sends OK and Asterisk sends OK to the remote fax.
* Remote fax sends t38 packets which are dropped by the firewall.
* Local fax re-sends t38 no-signal with the same sequence number.
* udptl drops the frame because it thinks it's a dup.
* Still no outgoing packets to open the firewall.
* t38 negotiation fails.

The patch drops frames t38 received before udptl sequence processing
when the call hasn't been answered yet.  The second no-signal frame
is then seen as new and is relayed out the external interface which
opens the port and allows negotiation to continue.

ASTERISK-26034 #close

Change-Id: I11744b39748bd2ecbbe8ea84cdb4f3c5943c5af9
---
M main/udptl.c
1 file changed, 12 insertions(+), 0 deletions(-)


  git pull ssh://gerrit.asterisk.org:29418/asterisk refs/changes/70/2870/4
-- 
To view, visit https://gerrit.asterisk.org/2870
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Gerrit-MessageType: newpatchset
Gerrit-Change-Id: I11744b39748bd2ecbbe8ea84cdb4f3c5943c5af9
Gerrit-PatchSet: 4
Gerrit-Project: asterisk
Gerrit-Branch: certified/11.6
Gerrit-Owner: George Joseph <gjoseph at digium.com>
Gerrit-Reviewer: Anonymous Coward #1000019
Gerrit-Reviewer: Joshua Colp <jcolp at digium.com>
Gerrit-Reviewer: Mark Michelson <mmichelson at digium.com>