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[Bug network/14307] New: getaddrinfo() triggers duplicate DNS requests when answer contains CNAME
- From: "jvb127 at gmail dot com" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sources dot redhat dot com
- Date: Fri, 29 Jun 2012 00:04:34 +0000
- Subject: [Bug network/14307] New: getaddrinfo() triggers duplicate DNS requests when answer contains CNAME
- Auto-submitted: auto-generated
http://sourceware.org/bugzilla/show_bug.cgi?id=14307
Bug #: 14307
Summary: getaddrinfo() triggers duplicate DNS requests when
answer contains CNAME
Product: glibc
Version: unspecified
Status: NEW
Severity: normal
Priority: P2
Component: network
AssignedTo: unassigned@sourceware.org
ReportedBy: jvb127@gmail.com
Classification: Unclassified
Created attachment 6493
--> http://sourceware.org/bugzilla/attachment.cgi?id=6493
Packet capture illustrating duplicate (redundant) DNS requests
I noticed spurious DNS requests on the network, and traced them down to
getaddrinfo() calls (e.g. using wget). This occurs on a Fedora 16 machine with
latest glibc, as well as a CentOS machine with older versions
To reproduce, perform the following in 2 consoles:
$tcpdump -v -n -i eth0 udp port 53 -w getaddr.pcap
$wget -4 http://www.gmail.com/
Result:
reading from file ./getaddr.pcap, link-type EN10MB (Ethernet)
17:59:38.263471 IP 192.168.1.9.54553 > 8.8.8.8.domain: 32628+ A? www.gmail.com.
(31)
17:59:38.313021 IP 8.8.8.8.domain > 192.168.1.9.54553: 32628 4/0/0 CNAME
mail.google.com., CNAME googlemail.l.google.com., A 74.125.226.22, A
74.125.226.21 (116)
17:59:38.313311 IP 192.168.1.9.57920 > 8.8.8.8.domain: 44145+ A? www.gmail.com.
(31)
17:59:38.367738 IP 8.8.8.8.domain > 192.168.1.9.57920: 44145 4/0/0 CNAME
mail.google.com., CNAME googlemail.l.google.com., A 74.125.226.22, A
74.125.226.21 (116)
17:59:38.476300 IP 192.168.1.9.50993 > 8.8.8.8.domain: 25319+ A?
mail.google.com. (33)
17:59:38.561056 IP 8.8.8.8.domain > 192.168.1.9.50993: 25319 3/0/0 CNAME
googlemail.l.google.com., A 74.125.226.21, A 74.125.226.22 (92)
17:59:38.561306 IP 192.168.1.9.54508 > 8.8.8.8.domain: 35020+ A?
mail.google.com. (33)
17:59:38.610485 IP 8.8.8.8.domain > 192.168.1.9.54508: 35020 3/0/0 CNAME
googlemail.l.google.com., A 74.125.226.21, A 74.125.226.22 (92)
17:59:38.716233 IP 192.168.1.9.59783 > 8.8.8.8.domain: 48556+ A?
accounts.google.com. (37)
17:59:38.765100 IP 8.8.8.8.domain > 192.168.1.9.59783: 48556 2/0/0 CNAME
accounts.l.google.com., A 209.85.225.84 (78)
17:59:38.765348 IP 192.168.1.9.41685 > 8.8.8.8.domain: 24558+ A?
accounts.google.com. (37)
17:59:38.819577 IP 8.8.8.8.domain > 192.168.1.9.41685: 24558 2/0/0 CNAME
accounts.l.google.com., A 209.85.225.84 (78)
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