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

[Mark Michelson]

> On Jan. 30, 2012, 2:57 p.m., Mark Michelson wrote:
> > Like Terry said, try not to make extraneous changes beyond the scope of the review if possible. Still, go ahead and commit since there's nothing _wrong_ here.
> 
> Alec Davis wrote:
>     I don't see any comments from Terry.
>     Pleae advise.

Sorry, I meant the ship it, but this comment was meant for a different review. Sorry for the confusion.


- Mark


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On Jan. 27, 2012, 3:34 p.m., Alec Davis wrote:
> 
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> 
> (Updated Jan. 27, 2012, 3:34 p.m.)
> 
> 
> Review request for Asterisk Developers.
> 
> 
> Summary
> -------
> 
> 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
> -----
> 
>   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
> -------
> 
> 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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