glibc 2.9-8

_ [debian] glibc 2.9-8

Starting with version 2.9-8, unified IPv4/IPv6 lookup have been enabled in the glibc’s resolver. This is faster, fixes numerous of bugs, but is problematic on some broken DNS servers and/or wrongly configured firewalls.

If such a DNS server is detected, the resolver switches (permanently for that process) to a mode where the second request is sent only when the first answer has been received. This means the first request will be timeout, but subsequent requests should be fast again. This behaviour can be enabled permanently by adding ‘single-request’ to /etc/resolv.conf.

ref. /usr/share/doc/libc6/NEWS.Debian.gz

というニュースが入っていた。手元ではとりあえず問題なさそう？