[SR-Users] uac module From header rewriting problems

[Daniel-Constantin Mierla]

Hello,

On 7/3/12 8:02 AM, Timo Teras wrote:
> Hi,
>
> I fixed some uac From rewriting issues in commit e1d1c774c9ac0b4d,
> however even with the latest versions I'm still seeing corruption in
>  From headers when they are rewritten for the whole dialogue
> (from_restore_mode=auto, the default).
>
> I spent some time analyzing the problem and the problem seems to be
> connected with the fact that only the bitwise difference of the
> original and modified URI are stored (XOR).  The only purpose for this
> appears to be the idea to save only the difference in the rr params
> instead of two full URIs.
>
> However, it appears that in many cases (especially call transfer) the
>  From header will be altered during dialogue. This is explicitly allowed
> in RFC 3261 § 20.20:
>     The From header field indicates the initiator of the request.  This
>     may be different from the initiator of the dialog.
>
> I've seen this in practise with few commercial SIP stacks. Sometimes
> the changes are minor, or even trivial - but with the difference
> encoding having even one character changed (e.g. case), being deleted or
> added will result in the whole header being corrupted.
>
> I'm now wondering if we should just store both URIs in the rr params.
> While taking little more space, it should fix us sending garbage to the
> wire (which usually results in dropped call as the remote will reject
> the garbage messages).
>
> Any better ideas?

it makes sense storing the entire value. Not sure if anyone else will 
want to be made configurable via mod param, I will go for simplest 
approach and have only the correct option, it will help in code maintenance.

Cheers,
Daniel

-- 
Daniel-Constantin Mierla - http://www.asipto.com
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