[Dnsmasq-discuss] Patch to cache SRV records - updated version (#3)

[Donald Muller]

I think this should be added to the code maybe with an option in the config file to turn on the caching of these records.

> -----Original Message-----
> From: Dnsmasq-discuss <dnsmasq-discuss-bounces at lists.thekelleys.org.uk>
> On Behalf Of Jeremy Allison
> Sent: Thursday, December 20, 2018 4:39 PM
> To: dnsmasq-discuss at lists.thekelleys.org.uk
> Subject: Re: [Dnsmasq-discuss] Patch to cache SRV records - updated version
> (#3)
> 
> On 12/20/2018 12:20 PM, Jeremy Allison wrote:
> > On Thu, 20 Dec 2018 11:53:11 -0800
> >
> > Jeremy Allison <jra at google.com> wrote:
> >
> >> I know dnsmasq doesn't cache SRV records by design:
> >>
> >> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=579536;msg=9
> >>
> >> However, when used with Samba code (winbindd) and
> >> other Windows-integrating technology (MIT krb5)
> >> there are a lot of SRV record queries that make
> >> the whole integration stack slow if SRV records
> >> are not cached.
> >>
> >> With that in mind, here is a patch to cache
> >> SRV records positively and negatively inside
> >> dnsmasq.
> >>
> >> I'm sending here it so that people who might need
> >> this functionality have a central place to find
> >> it (it might end up being used in ChromeOS, depending
> >> on test results / review).
> >
> > Sigh. Found a bug when testing. free_mx_srv_record()
> > wasn't checking for NULL pointers on free(),
> > which can be the case for negative cache
> > records.
> 
> Third time is the charm :-). Remember to NULL
> out free'd and uninitialized pointers and
> structrures, and remove the F_SRV flag on deleting
> the cache entry.
> 
> Hopefully this is the last iteration of this.
> I can't see any more issues to address, but
> I'm still testing :-).
> 
> Jeremy.