Bug#519774: libc6: causes many programs not to be able to resolve dns addresses
forcemerge 516218 519774
thanks
On Sun, Mar 15, 2009 at 07:20:42AM +0100, Petr Vandrovec wrote:
> Hello,
> it seems that DNS resolver is grossly confused, and sends
> two DNS requests on same socket back to back (strace below is
> from 'lynx http://www.jeep.com'). In first one DNS server
> responded only to second packet sent by resolver, and resolve
> failed (after that mdns was tried, and eventually lynx reported
> error that www.jeep.com does not exist). In second one DNS
> server responded only to first packet (in my tests I've never
> seen DNS server responding to both requests), and although DNS
> resolver still uselessly waited for 5 seconds, slowing web browsing
> to being almost unusable, after that 5 seconds DNS resolver
> declared success, and moved on.
>
> My /etc/resolv.conf is:
>
> gwy:~# cat /etc/resolv.conf
> domain hsd1.ca.comcast.net.
> search hsd1.ca.comcast.net.
> nameserver 68.87.76.178
> nameserver 68.87.78.130
> nameserver 68.87.69.146
> gwy:~#
>
> It seems to be caused by __libc_res_nquery always sending both
> T_A and T_AAAA request when T_UNSPEC query is being sent, and
> getting confused when only T_AAAA reply arrives.
>
The problem is that the DNS server of your ISP does not conform to the
RFC and only answer to the AAAA query with a void answer. It never
answer to the A query, so the glibc resolver can only conclude the whole
query has no answer.
This is a known problem, upstream has said he is working on a
workaround, but you should definitely talk to your ISP first, as the
--
Aurelien Jarno GPG: 1024D/F1BCDB73
aurelien@aurel32.net http://www.aurel32.net
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