Hi,

on the HEPix IPv6 working group testbed we stumbled
onto an issue in the glibc distributed with Scientific
Linux 6, where listening services that bind onto the first result
returned by getaddrinfo (when called with ai_req.ai_flags = AI_PASSIVE;
ai_req.ai_family = PF_UNSPEC;) will bind on IPv4 *only* even on
correctly configured IPv4/v6 dual-stack hosts.
This is different from the behaviour in SLC5, and affects notably
all network services offered by Globus.

We collected all details in this wiki page:
https://w3.hepix.org/ipv6-bis/doku.php?id=ipv6:siteconfig

The issue seems more in RFC3484 as it is, rather than in the corresponding
implementation in glibc, but one way to restore the IPv6 preference,
until/unless glibc is further patched (see for instance this glibc bugzilla ticket:
http://sourceware.org/bugzilla/show_bug.cgi?id=14967)
would be to add an extra label in /etc/gai.conf :

label ::ffff:7f00:0001/128 8

as in this example:
http://www.mi.infn.it/ipv6/prefer_dual_stack_on_unspec_binding_glibc29_gai.conf

Would you consider it useful for Scientific Linux distribution users
to add this /etc/gai.conf file to the default SL6 distribution ?
Maintaining IPv6 preference throughout on dual-stack hosts is key to keeping
enough momentum in the transition to IPv6.

Thanks.
Francesco Prelz
INFN - Milano