[asterisk-dev] [Code Review] RFC3261 Section 8.1.1.5. The sequence number value MUST be expressible as a 32-bit unsigned integer

[Alec Davis]

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This is an automatically generated e-mail. To reply, visit:
https://reviewboard.asterisk.org/r/1699/
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(Updated Jan. 27, 2012, 3:34 p.m.)


Review request for Asterisk Developers.


Changes
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Still has an INITIAL_CSEQ set to 2147483645 (2^31 - 2) to allow testing.


Summary (updated)
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RFC 3261 Section 8.1 documents intial value of CSeq and it's maximum out side of a dialog.
  8.1 UAC Behavior
     This section covers UAC behavior outside of a dialog.
  8.1.1.5
     .. "The sequence number value MUST be expressible as a 32-bit unsigned integer and MUST be less than 2**31." 
     "Section 12.2.1.1 discusses construction of the CSeq for requests within a dialog."

RFC 3261 Section 12.2.1.1, documents the maximum value a seqno can get to within a dialog, 2^32-1. (136 years equals 2^32 seconds).
   "If the local sequence number is empty, an initial value MUST be chosen using the guidelines of Section 8.1.1.5"  
   .. "With a length of 32 bits, a client could generate, within a single call, one request a second for about 136 years before needing to wrap around."
  
===============================================================================

By defining INITIAL_CSEQ to values near the maximum, it can clearly be seen that asterisk will represent the cseqno as negative numbers as %d is used in most places.

//#define INITIAL_CSEQ              101    /*!< Our initial sip sequence number */
#define INITIAL_CSEQ              2147483640 /*!< Our initial sip sequence number */
#define INITIAL_CSEQ              4294967290UL   /*!< Our initial sip sequence number */ 

Examples below after a few messages with INITIAL_CSEQ set to 214783640

...
Call-ID: d469d55c9e9e81ae at 192.168.y.yyy
CSeq: -2147483639 NOTIFY
User-Agent: Asterisk PBX SVN-trunk-r352864M
Subscription-State: active
Event: dialog
Content-Type: application/dialog-info+xml
Content-Length: 206

<?xml version="1.0"?>
<dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info" version="16" state="full" entity="sip:8612 at 192.168.x.xxx">

...
Call-ID: 7d1d964b7867eee008705e1e64386d4e at 192.168.x.xxx:5060
CSeq: -5 NOTIFY
User-Agent: Asterisk PBX SVN-trunk-r352864M
Event: message-summary
Content-Type: application/simple-message-summary
Content-Length: 92

Messages-Waiting: no
Message-Account: sip:asterisk at 192.168.x.xxx
Voice-Message: 0/0 (0/0)

 


Diffs (updated)
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  trunk/channels/chan_sip.c 352913 
  trunk/channels/sip/include/dialog.h 352913 
  trunk/channels/sip/include/sip.h 352913 

Diff: https://reviewboard.asterisk.org/r/1699/diff


Testing
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Noted that Notify for BLF and MWI, that the CSeq numbers now wrapped around to 0.

After using the 2nd maximum of 2^32 minus a few (#define INITIAL_CSEQ              4294967290UL) phones, BLF and MWI still workign as normal.

Previously the BLF would stop functioning after the minus values were reached.
Now it wraps around from 4294967295 to 0, as below.

Call-ID: c2aaba2919cfcd4a at 192.168.y.yyy
CSeq: 4294967295 NOTIFY
User-Agent: Asterisk PBX SVN-trunk-r352864M
Subscription-State: active
Event: dialog
Content-Type: application/dialog-info+xml
Content-Length: 205

<?xml version="1.0"?>
<dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info" version="4" state="full" entity="sip:8612 at 192.168.x.xxx">
<dialog id="8612">

...
Call-ID: c2aaba2919cfcd4a at 192.168.y.yyy
CSeq: 0 NOTIFY
User-Agent: Asterisk PBX SVN-trunk-r352864M
Subscription-State: active
Event: dialog
Content-Type: application/dialog-info+xml
Content-Length: 205

<?xml version="1.0"?>
<dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info" version="5" state="full" entity="sip:8612 at 192.168.x.xxx">
<dialog id="8612">


Thanks,

Alec

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