Bug 837695

Summary: glibc sends spurious DNS requests for certain hostnames
Product: Red Hat Enterprise Linux 6 Reporter: Jeroen van Bemmel <jvb127>
Component: glibcAssignee: Patsy Griffin <pfrankli>
Status: CLOSED ERRATA QA Contact: qe-baseos-tools-bugs
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 6.5CC: fweimer, law, mcermak, mfranc, rfreire
Target Milestone: rc   
Target Release: ---   
Hardware: Unspecified   
OS: Linux   
Whiteboard:
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.
 Story Points: ---
Clone Of:
: 1003669 (view as bug list) Environment:
Last Closed: 2013-02-21 07:05:13 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 1003669    
Attachments:
Description Flags
Potential fix none

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.

http://rhn.redhat.com/errata/RHBA-2013-0279.html