[Dnsmasq-discuss] Multicast dns

Simon Kelley simon at thekelleys.org.uk
Tue Apr 24 17:02:12 BST 2007

Tom Fanning wrote:
> <snip>
>> Not at all, It's a reasonable suggestion that dnsmasq should be
>> configurable to listen for mDNS and reply to everything: Even with the
>> nsswitch.conf fix, that has to be fixed on every new Ubuntu Feisty
>> install, a dnsmasq configuration tweak would do it for  a whole network
>> and if mDNS was not otherwise in use, nothing is lost.
>> OTOH, against doing this is that it breaks "real mDNS" so it's  a bug
>> to
>> fix another bug. Also it's possibly bloat for dnsmasq and of minor real
>> world use for most people. A judgement call, like most possible
>> enhancements.
> Well I guess it's up to you, Simon. I can certainly help with testing at
> this end. (Obviously!) Code-wise, I'm not hot on unmanaged code, so not much
> use to you here.

I think that the following might be useful, and probably RFC-compliant.

1) Add a flag --multicast, which makes dnsmasq listen for multicast DNS
requests: these are treated completely as normal, _except_ that queries
for the .local domain are ignored.

2) Add a second flag --local-ok which removes the _except_ behaviour from 2)

Just setting --multicast makes an RFC-compliant network which will work
with clients which do multicast for ordinary DNS and allow the
distributed-query system to work to answer .local queries.

setting --local-ok will stop mDNS from working, but it will allow
networks to still work which have used .local as the private domain,
even in the presence of Ubuntu Feisty-like clients which talk mDNS and
use multicast by default for .local queries. That should solve the sort
of problems Jan was seeing.

I'm not sure if this should go in 2.39 or not: I'll hack some code, and
see how disruptive it is, before deciding that.



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