Re: [dnsext] EDNS0 options open issues

[Shane Kerr <shane@ca.afilias.info>]

Stuart,

On Mon, 2008-11-24 at 12:11 -0800, Stuart Cheshire wrote:
> On 20 Nov, 2008, at 05:04, Ólafur Guðmundsson /DNSEXT chair wrote:
> 
> > Q1: How do we mark Ignorable vs Required options ?
> > (see Section 4.4.2 of EDNS0-bis)
> > The possibilities include:
> >      - Continue to define all options as ignorable
> 
> My experience is that (at least some) current DNS implementations  
> return FmtErr (1) when they receive a DNS Query with an unrecognized  
> EDNS0 option.
> 
> Therefore the de facto reality appears to be that all current EDNS0  
> option are "reject if unknown".
> 
> Whether a given EDNS0 option is ignorable may depend on context. I  
> suggest we let the client choose, by defining the top bit as the "may  
> ignore" flag. In other words, EDNS0 options 1, 2, 3, 4 are "reject if  
> unknown" options, and 0x8001, 0x8002, 0x8003, 0x8004 are the "ignore  
> if unknown" versions of those same options.

Not a bad idea. Should the server return a code indicating which options
it does and does not understand? (This is beginning to smell a bit like
DHCP, BTW.)

--
Shane


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