Re: [RFC] DNS system upgrades

On 02/19/2013 05:08 PM, Amos Jeffries wrote:
> A few things are on my radar that need improving in the Squid DNS
> components. I am proposing these as a batch, any which we can agree on
> will be scheduled for fixing in 3.4.
>
>
> 1) renaming all DNS options to begin with dns_* prefix.
>
> This will allow the cfgman documentation to collate these options
> together as a batch in future.
> Also clarify what component in Squid some of the more obscure options
> relate to.
> Also, allow for some future upgrades compacting these type of options
> into a single component directive / command line interpreter simplicity.
>
> Options affected that I'm aware of:
> append_domain
> ignore_unknown_nameservers
> hosts_file
> cache_dns_program ... (stripping the cache_ part.)
>
>
> NP: at this point I am on the fence about adding the prefix to fqdncache
> and ipcache options and *not* proposing a change to them.
>
>
>
> 2) adapting append_domains from a string type to a custom type
>
> This will allow us to do additional configuration validation. Such as
> identifying whether resolv.conf or squid.conf was used as data source.
>
>
> * auto-enablling dns_defnames search list
>
> /etc/resolv.conf contains two similar but different directives for
> labelling the local domain name.
>
> The "search" directive in particular signals DNS searching of multiple
> domains to the default host resolver. But Squid still requires explicit
> "dns_defnames on" in squid.conf to enable that behaviour. As a result we
> have administrators seeing a 'bad' difference between internal and
> dnsserver when they try upgrading to internal DNS.
>
> I propose using the resolv.conf hint to enable dns_defnames searching
> automatically in the absence of explicit squid.conf configuration.

By "explicit squid.conf configuration", you mean the dns_nameservers
option, right? In other words, if dns_nameservers is given, the entire
/etc/resolv.conf is ignored. Otherwise, both "nameserver" and "search"
directives in /etc/resolv.conf are honored, correct?

> Administrators who do not want it are supposed to be using the
> alternative "domain" directive, when they use tools like host or
> nslookup to debug they should see consistent behaviour (diverting them
> away from Squid to the actual DNS issues in resolv.conf settings), and
> this will prevent future confusion such as appears to be happening in
> bug 3585.

> 3) removal of dnsserver and related code.
>
> IRIC the argument for keeping it previously was NetBIOS or WINS name
> lookup still being needed (though I am suspicious the dns_defnames issue
> was the actual cause of this).
>
> - NetBIOS was deprecated in 2000, to be replaced by DNS
> - WINS was deprecated in 2012, to be replaced by IPv6
> auto-configuration / adhoc services.
>
>
> I am okay to see this delayed a few more squid series to give WINS
> longer to die, but it is time we looked again at why it is still there.
>
> Since the last round of discussion we adjusted the internal engine to
> fix most of the remaining issues. The above dns_defnames behaviour
> change is the last bit I am aware of that is needed for a seamless
> upgrade, short of full-blown NetBIOS support integration which is not
> very feasible.

All three items above sound good to me, but this is not my area of
expertise so I hope others will chime in.

The WINS-related decision may be worth discussing on squid-users as well.

Thank you,

Alex.
Received on Wed Feb 20 2013 - 07:46:06 MST