Bug#563552: libc: resolver doesn't fallback to secondary dns-server when first one is ipv6 and unreachable
tag 563552 - moreinfo
tag 563552 - unreproducible
block 562804 by 563552
severity 563552 serious
thanks
On Tue, Jan 05, 2010 at 07:58:01PM +0100, Luca Bruno wrote:
> Aurelien Jarno scrisse:
>
> > This is not observable here, with the same configuration as yours.
> > Have you tried an other nameserver than 8.8.8.8, or 8.8.8.8 alone?
> >
> > What's the output of 'strace getent ahosts www.debian.org'?
>
> [...]
> connect(3, {sa_family=AF_INET6, sin6_port=htons(53), inet_pton
> (AF_INET6, "::ffff:8.8.8.8", &sin6_addr), sin6_flowinfo=16895189,
> sin6_scope_id=0}, 28) = -1 ENETUNREACH (Network is unreachable)
>
> Looks like another effect of bindv6only, as I have
> "net.ipv6.bindv6only = 1".
>
> Perhaps you have set it to 0, as it is working that way:
>
> thetis:/home/lucab# sysctl net.ipv6.bindv6only=0
> net.ipv6.bindv6only = 0
> thetis:/home/lucab# getent ahosts www.debian.org
> 2001:888:2000:12::2 STREAM www.debian.org
> 2001:888:2000:12::2 DGRAM
> [...]
>
Indeed, I am now able to reproduce the problem. I haven't rebooted my
machine since the change, that's why I didn't see the problem.
It appears actually as soon as there is an IPv6 server in
/etc/resolv.conf, thus increasing the severity. You can't imagine how I
love uncoordinated unannounced breakages.
--
Aurelien Jarno GPG: 1024D/F1BCDB73
aurelien@aurel32.net http://www.aurel32.net
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