[asterisk-dev] [Code Review] Lightweight NAT Support

[Simon Perreault]

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I have two questions...


1. CRLF keep-alives are supported only for connection-oriented transports. Not UDP. Excerpt from RFC 5626:

4.4.1. Keep-Alive with CRLF

   This approach MUST only be used with connection oriented transports
   such as TCP or SCTP; it MUST NOT be used with connection-less
   transports such as UDP.

This is because of RFC 3261 section 7.5. Excerpt:

   Implementations processing SIP messages over stream-oriented
   transports MUST ignore any CRLF appearing before the start-line
   [H4.1].

A CRLF transported over UDP is just plain wrong. It is not valid SIP.

So, question: did I miss something? Did I not understand what you're sending over UDP?


2. If Asterisk is talking over TCP or TLS to a UA that supports RFC 5626, that UA would echo the CRLF back to Asterisk. Is Asterisk prepared to handle that?

- Simon


On Feb. 21, 2012, 7:26 a.m., Joshua Colp wrote:
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> (Updated Feb. 21, 2012, 7:26 a.m.)
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> Review request for Asterisk Developers.
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> Summary
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> This patch implements extremely lightweight NAT support, specifically sending a CRLF at a defined interval to keep the NAT mapping open. It does not use this mechanism to determine if the remote server is available or not, that is the trade off.
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> Diffs
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>   /trunk/channels/chan_sip.c 355996 
>   /trunk/channels/sip/include/sip.h 355996 
>   /trunk/configs/sip.conf.sample 355996 
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> Diff: https://reviewboard.asterisk.org/r/1756/diff
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> 
> Testing
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> Confirmed packet is sent at default interval as well as configured interval. Also wrote testsuite test which will be in another review.
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> Thanks,
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> Joshua
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>

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