[asterisk-bugs] [JIRA] (ASTERISK-20644) Don't always use the existing TCP connection for in-dialog requests

[Iñaki Baz Castillo (JIRA)]

Iñaki Baz Castillo created ASTERISK-20644:
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             Summary: Don't always use the existing TCP connection for in-dialog requests
                 Key: ASTERISK-20644
                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-20644
             Project: Asterisk
          Issue Type: Bug
      Security Level: None
          Components: Channels/chan_sip/Interoperability
    Affects Versions: 11.0.0
            Reporter: Iñaki Baz Castillo


If Asterisk receives an INVITE via TCP comming from a SIP proxy, answers the call and later Asterisk sends a re-INVITE or BYE for that dialog, Asterisk sends such an in-dialog request over the existing TCP connection previously opened by the SIP proxy. This is incorrect. Asterisk should open a NEW TCP connection to the address given in the top Record-Route header.

So for example, Asterisk receives the following INVITE from TCP 1.2.3.4 port 8888:

------------------
# TCP 1.2.3.4:8888 => ASTERISK:5060

INVITE sip:test at domain.com SIP/2.0
Record-Route: <sip:1.2.3.4:5060;transport=tcp>
------------------

When Asterisk sends a BYE or a re-INVITE in this leg, it MUST respect the address in the top Route of the BYE or re-INVITE, which is: TCP 1.2.3.4 port 5060. So it should send the BYE to:

------------------
# TCP ASTERISK:5060 => 1.2.3.4:5060
BYE sip:abc at 9.8.7.6 SIP/2.0
Route: <sip:1.2.3.4:5060;transport=tcp>
------------------

This is something really basic in RFC 3261 and mandatory. Asterisk could use the existing TCP connection just in case nat=yes (or some other new values I don't fuly know in the latest version), but by default, is "nat" parameter is not set for the Proxy peer, please DON'T reuse the existing TCP connection because that is a violation of RFC 3261.

In fact, it's perfectly legal for a SIP proxy or SIP server to refuse/reject SIP requests coming from a TCP connection that the proxy/server itself opened against a remote proxy/server. These are RFC 3261 rules, really.

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