Re: [Dproxy-devel] 0.5 vs nexgen?

[Mark H. <mar...@ho...>]

On Thu, Aug 29, 2002 at 01:27:22AM -0700, Matthew Pratt wrote:
>> The 0.5 behavior did not require you to
>> pre-configure a DNS server in
>> dproxy's config, but nexgen does.  This behavior
>> does not really do
>> what I'm looking for, and I'm much more interested
>> in the 0.5 behavior,
>> which indirectly uses /etc/resolve.conf.
>
>Could you please explain a little more?

I use a program called win4lin on my laptop.  Win4lin is a program
like vmware which creates a virtual machine in linux that can runs
a windows OS.  In order to connect up to the network, I have set up a
"dummy" network w/in linux.  This looks exactly like an ethernet network,
but it's entirely abstracted w/in the linux kernel.  You could think
of it like this: my laptop is two computers (one linux and one windows)
connected together with a "virtual ethernet" (i.e. the dummy network).
When win4lin connects to the dummy network, it routes through my laptop
using iptables and NAT.

The problem is DNS.  Win4lin (on the dummy network) needs to have a
different DNS configuration depending on whether or not I'm at work
at home network, or if I'm on the road dialed up into the internet.
In the third case, I don't know in advance what the DNS servers will be.
In the other two cases, I can't access my work DNS servers from home and
vice versa.  So I end up having to reconfigure DNS in win4lin everytime
I switch networks.

But this is not a problem in Linux.  Linux simply gets the DNS servers
during network config using either DHCP or PPP, and it uses those servers
because they're stored in /etc/resolv.conf.  What I was looking for with
dproxy was a way to extend the use of the DHCP assigned DNS servers to
my statically configured win4lin.

So I can do this by setting up dproxy 0.5 on my linux box.  And then
statically pointing the DNS resolver in win4lin to use my linux box for
all DNS resolution.  Then it doesn't matter where I am connected, as long
as linux's /etc/resolv.conf is correct, win4lin can properly resolve DNS.

Using nexgen requires that I know in advance what all of my DNS servers
will be when I configure dproxy.  And I don't.

I've found lots of different DNS proxies that support the new strategic
direction of dproxy: dnrd, pdnsd, totd, dnscache.  But dproxy was the
only one that I found that supported what I actually wanted to do.
I'd really like to see it available as an option in nexgen to use
blocking gethostbyname().  For what I'm trying to do the speed thing
just is NOT that big of a deal.  However, I can see how it would not be
a good default setting.

>One thing that the nexgen version does that the 0.5
>version doesn't  is parallel queries. It will
>simultaneously query all the DNS servers listed in its
>config file and reply with which ever anwser happens
>to come back first.

You might want to consider doing something that pdnsd does.  It keeps
track of which dns servers are available.  Pdnsd will (by default) ping
test all DNS servers in its configuration, and only send queries to
those servers that are available.  Ping is the default test, but there
are others.

Just something to think about.

Thanks so much for your reply.
- Mark