[Bug 1072899] [NEW] vpn dns server addresses - host lookups fail if first server is not reachable

[Glenn Coombs]

Public bug reported:

I tried to report this bug using "ubuntu-bug dnsmasq-base" but that
process repeatably crashes :-(  I've filed a separate bug report on that
issue but therefore there is no information automatically appended.  The
output of lsb_release -a is:

No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 12.04.1 LTS
Release:        12.04
Codename:       precise

and I am happy to append any further information that may be required.


I connect to my work network via VPN.  The config has been working well but stopped working recently.  The symptoms were that the VPN connection still succeeded but that DNS lookups of machines on the VPN failed.  I have these lines in the syslog:

Oct 29 20:47:11 mini NetworkManager[1071]: <info> Internal IP4 DNS: 192.168.15.221
Oct 29 20:47:11 mini NetworkManager[1071]: <info> Internal IP4 DNS: 192.168.5.221
Oct 29 20:47:11 mini NetworkManager[1071]: <info> DNS Domain: 'kl.imgtec.org'

which shows that 2 DNS servers were reported when the VPN connection was
established.  If I attempt to lookup the IP address of my machine:

% host glenn.kl.imgtec.org
;; connection timed out; no servers could be reached

then it times out.  If I tell it to use the second server:

$ host glenn.kl.imgtec.org 192.168.5.221
Using domain server:
Name: 192.168.5.221
Address: 192.168.5.221#53
Aliases: 

glenn.kl.imgtec.org has address 192.168.17.88

then it works as expected.  It seems that the 15.221 server is down (I
cannot ping it) but the 5.221 server is fine.  I would have expected the
DNS lookup to fall back to the second server when it failed to receive a
reply from the first server instead of just giving up.

The nm-dns-dnsmasq.conf file only shows information relating to the 1st
server - it seems to have totally ignored the 2nd server:

$ cat /var/run/nm-dns-dnsmasq.conf 
server=/kl.imgtec.org/192.168.15.221
server=/79.168.192.in-addr.arpa/192.168.15.221
server=/200.9.192.in-addr.arpa/192.168.15.221
server=/5.168.192.in-addr.arpa/192.168.15.221
server=/6.168.192.in-addr.arpa/192.168.15.221
server=/7.168.192.in-addr.arpa/192.168.15.221
server=/14.168.192.in-addr.arpa/192.168.15.221
server=/15.168.192.in-addr.arpa/192.168.15.221

--
Glenn

** Affects: dnsmasq (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: dns vpn

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https://bugs.launchpad.net/bugs/1072899

Title:
  vpn dns server addresses - host lookups fail if first server is not
  reachable

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