[Asterisk-Dev] Feature request: auto-guessing NAT status based on From: IP address

[Eric Wieling]

Why not let you specify a netblock for nat or nonat.  i.e.
nat=172.16.0.0/255.255.240.0 or nonat=63.173.166.0/255.255.255.0 and
then make natdefault=nat or natdefault=nonat

Seems to me like a more flexable system than guessing if we should nat
or not.

--Eric

On Wed, 2003-04-16 at 19:47, John Todd wrote:
> [Sorry to put this up to the list instead of submitting code; I can't 
> code my way out of a wet paper bag, as I've said before.]
> 
> 
> Proposal:
> 
> Extension to the "nat=" flag in sip.conf to automatically guess on NAT status.
> 
> Reason:
> 
> I have a bunch of people that keep moving their SIP devices between 
> home and work (NAT and non-NAT IP space) and I get tired of switching 
> their "nat=" status every time they move.  Most (but of course, not 
> all) NAT devices give out RFC1918 addresses, so in any given REGISTER 
> or INVITE status we have a pretty good idea if a device is NAT'ed or 
> not.  Why not use that data to solve the problem for the 90% of the 
> people who have NATs that provide addresses in this space?  Retaining 
> the "yes" and "no" flags maintains backwards static compatibility for 
> those who need it or for address spaces that are NAT'ed but do not 
> fall into the RFC1918 area.
> 
> 
> Syntax:
> 
> Old syntax:
>   nat=[1,0]
> 
> New Syntax
>   nat=[1,0,yes,no,auto]
> 
> The "0" and "1" definitions will retain their historical meaning, and 
> will also have duplicates with the terms "yes" and "no" to mean "1" 
> and "0" respectively.
> 
> If the keyword "auto" is specified, the system will make a 'best 
> guess' as to the status of the NAT flag for that SIP peer.  If the IP 
> address in the "From:" field in an INVITE or REGISTER is set to one 
> of the common RFC1918 addresses, then the system will assume "yes" 
> and the appropriate re-write and "via" headers will be set.
> 
> 
> Definitions:
> 
> RFC1918 space:
> 
> 10/8
>    - match on first octet being a "10"
> 
> 172.16/12
>   -  match on first octet being 172, and second octet being between 16 and 31
> 
> 192.168/16
>   - match on first octet being 192, and second octet being 168
> 
> See RFC1918 (http://www.zvon.org/tmRFC/RFC1918/Output/index.html)
> 
> 
> JT
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