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[Bug network/14307] New: getaddrinfo() triggers duplicate DNS requests when answer contains CNAME


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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