Bug 837695 - glibc sends spurious DNS requests for certain hostnames
Summary: glibc sends spurious DNS requests for certain hostnames
Alias: None
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: glibc
Version: 6.5
Hardware: Unspecified
OS: Linux
Target Milestone: rc
: ---
Assignee: Patsy Griffin
QA Contact: qe-baseos-tools-bugs
: 837696 837697 837698 854759 (view as bug list)
Depends On:
Blocks: 1003669
TreeView+ depends on / blocked
Reported: 2012-07-04 21:05 UTC by Jeroen van Bemmel
Modified: 2018-11-29 20:50 UTC (History)
5 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Cause: A buffer in glibc's resolver code was too small to handle results for certain DNS queries. Consequence: As a result, the query would have to be repeated after a larger buffer was allocated. This wastes time and network bandwidth. Fix: The buffer has been enlarged to handle the larger DNS results. Result: No extraneous DNS queries are generated.
Clone Of:
: 1003669 (view as bug list)
Last Closed: 2013-02-21 07:05:13 UTC
Target Upstream Version:

Attachments (Terms of Use)
Potential fix (1.99 KB, patch)
2012-07-05 21:03 UTC, Jeff Law
no flags Details | Diff

System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHBA-2013:0279 0 normal SHIPPED_LIVE glibc bug fix and enhancement update 2013-02-20 20:37:06 UTC
Sourceware 14307 0 None None None Never

Description Jeroen van Bemmel 2012-07-04 21:05:40 UTC
Description of problem:
A call to getaddrinfo() using glibc x86_64 results in duplicate DNS queries for the same A-record, causing redundant network traffic and extra delay for the client application. It may also break certain DNS-based load balancing schemes

Version-Release number of selected component (if applicable):
glibc latest HEAD

How reproducible: Always

Steps to Reproduce:
1. Start tcpdump using "udp port 53"
2. wget -4 www.google.com
Actual results:
2 DNS A queries + 2 identical answers for "www.google.com"

Expected results:
Single DNS A query + answer

Additional info:
See glibc bug report: http://sourceware.org/bugzilla/show_bug.cgi?id=14307

Comment 2 Jeff Law 2012-07-05 15:41:19 UTC
*** Bug 837696 has been marked as a duplicate of this bug. ***

Comment 3 Jeff Law 2012-07-05 15:41:57 UTC
*** Bug 837697 has been marked as a duplicate of this bug. ***

Comment 4 Jeff Law 2012-07-05 15:42:41 UTC
*** Bug 837698 has been marked as a duplicate of this bug. ***

Comment 5 Jeff Law 2012-07-05 21:03:40 UTC
Created attachment 596504 [details]
Potential fix

Comment 6 Jeroen van Bemmel 2012-07-06 01:24:16 UTC
Comment on attachment 596504 [details]
Potential fix

A slightly different patch was submitted to the libc-alpha mailing list: http://sourceware.org/ml/libc-alpha/2012-07/msg00057.html

It will probably be committed into SVN tomorrow (Friday)

Comment 7 Jeff Law 2012-07-06 02:29:46 UTC
I'm aware of that change; the RHEL 6 codebase is slightly different and in fact doesn't have the codepath where the fix is being made upstream.

Comment 10 Jeff Law 2012-09-05 18:51:10 UTC
*** Bug 854759 has been marked as a duplicate of this bug. ***

Comment 12 errata-xmlrpc 2013-02-21 07:05:13 UTC
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.


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