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Re: new rawhide glibc



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Yanko Kaneti wrote:
> https://bugzilla.redhat.com/show_bug.cgi?id=448117
> 
> There are two namservers in resolv.conf which might be the tripping
> point? Sorry for failing to mention that before.

That's not an issue.

I think it's fixed now in cvs.  The reason why I didn't fix this before
is that the server I (indirectly) use doesn't return any answer fort he
T_AAAA query.  The server you're using is sending back a SERVFAIL error.

Anyway, I'm treating SERVFAILs now like timeouts when it comes to having
received one reply.

Jakub will hopefully build a new glibc sometime soon.


To comment on a few mails in this thread:

- - the problem is new and not new.  It is new because of new code paths
  which are obviously not yet well tested.  It is not new in that we
  had to treat the same situations before.

  The good news is that the new code should be faster since it waits
  less in total.

- - it is of course necessary to handle all these situations.  I know
  that the server setup quality out there is bad.  This is only the
  tip of the iceberg.  Nevertheless, there should be an effort to
  rectify the situation.  For instance, in this specific case, the
  server I talk to doesn't provide a SERVFAIL answer and therefore
  the resolver has to reply on a timeout.  Multiply this by the
  number of DNS servers in /etc/resolv.conf and the number of retries
  and you'll arrive at substantial delays.  There is nothing the
  resolver can do.  All one can do is to use nscd to cache the
  results (albeit it's only effective with the new libc).

- - the reason why ping is not affected is that it doesn't look up IPv6
  addresses.  The problem case is when both IPv4 and IPv6 addresses are
  needed at the same time using the getaddrinfo interface and AF_UNSPEC
  as the type.


There are likely more problems looming.  So keep your eyes open.  When
problems appear, capture the net traffic to and from port 53 as well as
strace of, say, getent.

- --
➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖
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