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[Bug network/14307] getaddrinfo() sends superfluous DNS requests in x86_64 programs for certain hostnames
- From: "jvb127 at gmail dot com" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sources dot redhat dot com
- Date: Sat, 30 Jun 2012 02:23:01 +0000
- Subject: [Bug network/14307] getaddrinfo() sends superfluous DNS requests in x86_64 programs for certain hostnames
- Auto-submitted: auto-generated
- References: <bug-14307-131@http.sourceware.org/bugzilla/>
http://sourceware.org/bugzilla/show_bug.cgi?id=14307
--- Comment #3 from Jeroen van Bemmel <jvb127 at gmail dot com> 2012-06-30 02:23:01 UTC ---
(In reply to comment #2)
> Reproducible on HEAD.
>
> The size of the response is what seems to be causing the second query -- 6 or
> more seems to be the trigger. My initial guess was that the first lookup led to
> an ERANGE internally, resulting in the second query, but that should have
> happened for 32-bit as well. So this might well be something else. This has
> nothing to do with whether there is a CNAME in the response.
You are correct that __gethostbyname2_r in sysdeps/posix/getaddrinfo.c returns
ERANGE the first time when using a 512-byte buffer, in 64-bit mode. It is then
retried with a 1024-byte buffer, and the call succeeds
However, the same call in 32-bit mode also uses a 512-byte buffer, and does not
return ERANGE.
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