Re: [Bugme-new] [Bug 28512] New: IPv6 SLAAC address preferred over static one as source address

(switched to email.  Please respond via emailed reply-to-all, not via the
bugzilla web interface).

On Mon, 7 Feb 2011 16:15:16 GMT
bugzilla-daemon@bugzilla.kernel.org wrote:

https://bugzilla.kernel.org/show_bug.cgi?id=28512

           Summary: IPv6 SLAAC address preferred over static one as source
                    address
           Product: Networking
           Version: 2.5
    Kernel Version: 2.6.36
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: IPV6
        AssignedTo: yoshfuji@linux-ipv6.org
        ReportedBy: ghen@telenet.be
        Regression: No


Linux IPv6 source address selection rules are described here:
http://www.davidc.net/networking/ipv6-source-address-selection-linux

In case of a tie, "Linux chooses to use the latest address added".

A very common tie is where a host has a SLAAC (Stateless address
auto-configuration) address as well as one or more statically assigned ones in
the same /64.  The SLAAC address will almost always be the most recently
"added" one, as it is renewed with every Router Advertisement on the network,
and there will be a tie for all other rules.

As a consequence, the kernel chooses this address by default for outgoing
connections.  This is usually not the preferred scenario; the static address
will more likely have proper reverse DNS, be configured in ACL's, etc.

This has been discussed on the ipv6-ops mailing list
(ipv6-ops@lists.cluenet.de), and a better suggestion for a tie-breaker came
out: the preferred lifetime of the address.

SLAAC addresses will have a limited preferred lifetime (as defined by the
router), static addresses will usually have an unlimited preferred lifetime
(0).  So it makes a lot of sense to take this preferred lifetime into account
for source address selection (how is it otherwise "preferred"?).

This could be added as rule #9 before using the most recently added as a final
tie breaker?

Geert