[Bug libc/11709] glibc domain resolution does not obtain IP addresses from truncated UDP DNS responses.

["pasky at suse dot cz" <sourceware-bugzilla@sourceware.org>]

------- Additional Comments From pasky at suse dot cz  2010-06-16 21:10 -------
Thanks for your report - though its form is more of a blog post and more
to-the-point summary would be easier to process.

As you note, the router behavior is completely non-standard. However, we cannot
just decide we do not need anything else from the DNS record, since it may be
crucial to get all the records e.g. to properly sort and choose the appropriate
IP address based on the preferred family and scope; getaddrinfo() supports
complex ordering mechanisms for this (see gai.conf(5)). Ignoring the rest of a
truncated reply would cause invalid behavior.

Thus, even if we introduced a special option to process even truncated UDP
replies, that behavior would be actually harmful and it is better then to use a
different (e.g. local-running) caching nameserver. Since this is the first bug
report about this router I have ever seen, I don't think your problem is that
wide-spread; but even if it was, it would be much better for the distributions
to test and handle such broken DNS servers specially (e.g. as part of the DHCP
negotiation), falling back to a local caching nameserver instead of forcing
glibc to process broken DNS replies at all costs.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |WONTFIX


http://sourceware.org/bugzilla/show_bug.cgi?id=11709

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