[sr-dev] Patch: Respect Order field in NAPTR, as required by RFC 2915

[Daniel-Constantin Mierla]

Hello,

thanks for the patch, I will look over it soon.

Cheers,
Daniel

On 10/18/13 3:14 PM, Øyvind Kolbu wrote:
> Hi,
>
> Kamailio's NAPTR behavior by default ignores the Order field, which it is
> not allowed to do. Excerpt from RFC 2915:
>
>     Order
>        A 16-bit unsigned integer specifying the order in which the NAPTR
>        records MUST be processed to ensure the correct ordering of
>        rules.  Low numbers are processed before high numbers, and once a
>        NAPTR is found whose rule "matches" the target, the client MUST
>        NOT consider any NAPTRs with a higher value for order (except as
>        noted below for the Flags field).
>
> Currently one can set dns_{udp,tcp,tls,sctp}_pref to the same value and
> then it will respect the Order field. This has the problem that the SRV
> lookup order is forced to udp, tcp, tls and sctp.¹ Hence you can not
> follow the RFC for NAPTR and also set your own priorities for SRV. E.g. I
> want to have tls -> tcp -> udp and adhere to the NAPTR.
>
> Made a core option, dns_naptr_ignore_rfc, default off, to preserve today's
> behavior. See attached patch.
>
> One implementation detail is that one currently can disable a protocol
> by setting the priority to -1. In my patch that is currently ignored.
> Can add a check for that in init_naptr_proto_prefs() before setting
> a protocol's preference to 1.
>
> ¹ Mandated by the order of ip_addr.h's enum sip_protos.
>
>
>
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-- 
Daniel-Constantin Mierla - http://www.asipto.com
http://twitter.com/#!/miconda - http://www.linkedin.com/in/miconda
Kamailio Advanced Trainings - Berlin, Nov 25-28; Miami, Nov 18-20, 2013
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