[asterisk-bugs] [Asterisk 0019202]: [patch] switching From-address mid-register breaks channel variables

[Asterisk Bug Tracker]

The following issue has been UPDATED. 
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https://issues.asterisk.org/view.php?id=19202 
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Reported By:                wdoekes
Assigned To:                
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Project:                    Asterisk
Issue ID:                   19202
Category:                   Channels/chan_sip/General
Reproducibility:            always
Severity:                   minor
Priority:                   normal
Status:                     new
Asterisk Version:           1.4.41 
JIRA:                        
Regression:                 No 
Reviewboard Link:            
SVN Branch (only for SVN checkouts, not tarball releases): N/A 
SVN Revision (number only!):  
Request Review:              
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Date Submitted:             2011-04-29 05:12 CDT
Last Modified:              2011-04-29 05:13 CDT
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Summary:                    [patch] switching From-address mid-register breaks
channel variables
Description: 
Hi,

I'm using a inbound proxy before my asterisk which guesses which account
someone is using based on message headers and IP addresses. This is not
reliable until I get a Digest username. When I get the digest username I
am certain which user it is, and I replace the From-address accordingly.

In this scenario, the following can happen:

(1) INVITE from CLIENT to PROXY
(2) PROXY replaces From: with "Joe" and sends to ASTERISK
(3) ASTERISK challenges the INVITE with a 40[17]

(4) INVITE from CLIENT TO PROXY using Digest username "Lucy"
(5) PROXY replaces From: with "Lucy" and sends to ASTERISK
(6) ASTERISK handles INVITE fine...

... except for the fact that the channel variables are now duplicated
(and in the wrong order).


sip.conf:

[JoeUser]
setvar=username=Joe
accountcode=JoeAccount
...
[LucyUser]
setvar=username=Lucy
accountcode=LucyAccount
...

Now, in my dialplan:
- ${CDR(accountcode)} equals "LucyAccount"
and 
- ${username} equals "Joe"

Why is that? Because the channel variables set during the first INVITE
are not destroyed. And, due to the linked-list nature of chanvars, they
are in the "wrong" order, containing first username=Lucy and then
username=Joe.

When copying the chanvars to the dialplan context using
pbx_builtin_setvar_helper Joe overwrites Lucy, hence the inconsistency.


The attached patch should fix it.


Regards,
Walter Doekes
OSSO B.V.


P.S. I'm expecting someone to reply that switching From: mid-INVITE is
not legal, SIP-wise. As a pre-emptive response to that:
(1) I couldn't find the relevant RFC-part that states so and,
(2) asterisk is inconsistent in it's behaviour because it *does* accept
    the switch, apart from this bug.
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Issue History 
Date Modified    Username       Field                    Change               
====================================================================== 
2011-04-29 05:13 wdoekes        Summary                  switching From-address
mid-register breaks channel variables => [patch] switching From-address
mid-register breaks channel variables
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