disable IPv6 name lookups in Centos

As a kind of followup on my previous post, I’ve been increasingly annoyed by how puppet agent update on my Centos hosts takes a looong time. F.example I’m up in 120 seconds for my LAMP puppet profiles.
I suspected yum to be the slowdown, but my previous post from today gave me a hint that maybe puppet does something IPv6’ish stuff too .
I had a look at

 # tcpdump -vvvvv 'port 53'

while doing a puppet update, and I see a lot of:

[myhostname].42349 > ns1.[mydomain].domain: [bad udp cksum 5599!] 18560+ AAAA? puppet.[mudomain]. (36)
15:09:33.326822 IP (tos 0x0, ttl 64, id 61459, offset 0, flags [none], proto UDP (17), length 133)
    ns1.[mydomain].domain > [myhostname].42349: [udp sum ok] 18560 q: AAAA? puppet.[mydomain]. 0/1/0 ns: [mydomain]. [50m40s] SOA ns1.[my SOA]. hostmaster.[my SOA]. 1378837114 14400 3600 777600 3600 (105)

So those AAAA request does indeed look like some IPv6 lookups are happening.
Looking at the resolv.conf man page, and with help from wiki.echochat.org I tried adding to

options single-request-reopen

and suddenly puppet agent update took roughly 3 seconds, instead of 120 seconds …
Cool ! 🙂

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