[CUWiN-Dev] adding nameservers to node config

[tom]

----- Original Message ----- 
From: "Chase Phillips" <shepard at ameth.org>
To: "tom" <tom at anotherwastedday.com>
Cc: <cu-wireless-dev at cuwireless.net>
Sent: Sunday, May 15, 2005 7:33 PM
Subject: Re: [CUWiN-Dev] adding nameservers to node config


> On Sun, 15 May 2005, tom wrote:
>
>> I was at Mike Lehman's house today and I think I've refined his setup to
>> the
>> point of usability. The trick is, his router doesn't give out DNS servers
>> along with a DHCP lease. Or if it does, it gives out the incorrect ones.
>> Mike's computer has a pair of DNS servers that it uses, and when I used
>> these I could connect to the Internet from my laptop through his node. I
>> did
>> this by specifying the DNS servers on my own computer, though, not on the
>> node.
>
> Might be worth finding out if the router is handing out DNS servers with
> the lease.  Maybe that could be fixed and the issue on the node would
> resolve itself?

The router is indeed handing out *a* DNS server, but it's either a fake one
or one that doesn't seem to be operating correctly. Even setting it manually
on my machine (thinking perhaps the router wasn't giving it out properly)
didn't work. Furthermore, trying to use the DNS servers I use from home
didn't work, which surprised me. My ISP has been on the blink this week,
though, so there's a chance that was just coincidence and those servers are
down.

Regardless, the only way Mike's computer seems to be able to use DNS is by
using the pair of nameservers that he's got configured on his machine.

Fixing the router would indeed fix this problem, but I'm not sure why it's
doing this to begin with. There's a chance it's by design, but I can't
really think of why. Would there be some reason Earthlink wouldn't want to
hand out their DNS servers over PPPoE?

>> So the question becomes how to permanently add these nameservers to the
>> node. I believe they can just be added to /etc/resolv.conf, but I don't
>> know
>> if that file persists after reboot. And a software upgrade would
>> certainly
>> wipe them, but I think that's unavoidable and not necessarily too
>> problematic (we will just need to be careful about reinstating these
>> servers
>> after an upgrade).
>
> /etc/resolv.conf won't persist across reboots.  For that to work it will
> also need to be modified at /permanent/etc/resolv.conf.  (bryan will
> correct me if I've got the path wrong.)  /permanent is mounted read-only
> so you'll need to remount it read-write before making any modifications.
> He also recommends doing something like
>
>  sh# cp /permanent/etc/resolv.conf /permanent/etc/garbage
>
> after you've completed making changes to /permanent/etc/resolv.conf to
> workaround a known issue with storing data prior to shutting down a node.
>
> How recent is the software on Mike's node?  If it's less than a year old,
> it may be using dhcpselect.  When dhcpselect runs dhclient,
> /etc/resolv.conf will probably get overwritten.  In some cases, then,
> changes made to /etc/resolv.conf won't persist between reboots, either.

This is using the March 9th build, so it's fairly recent software.

> There could be a flag for dhclient to only use the network address info
> (and not the DNS info) offered by the lease.  Hacking dhcpselect to call
> dhclient with that flag might keep it from touching /etc/resolv.conf.
> This would be a useful modification to dhcpselect if you're willing to
> look into it.

I'll check the docs on dhclient and see if this is even an option. But
normally we would *want* the DNS info, so how would this be implemented to
both work with a "standard" setup and be changeable? I suppose the hacked
version of dhcpselect could by default just go with the norm, but somewhere
in an editable config file have the option of only taking select bits of the
DHCP lease information.