kern/135585: [ip6] net.inet6.ip6.accept_rtadv=1 removes a cloning route

[Hiroki Sato]

>Number:         135585
>Category:       kern
>Synopsis:       [ip6] net.inet6.ip6.accept_rtadv=1 removes a cloning route
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sun Jun 14 23:10:00 UTC 2009
>Closed-Date:
>Last-Modified:
>Originator:     Hiroki Sato
>Release:        FreeBSD 7.2-STABLE i386
>Organization:
Tokyo University of Science
>Environment:
System: FreeBSD phaleano.allbsd.org 7.2-STABLE FreeBSD 7.2-STABLE #20: Sun Jun 14 02:30:28 JST 2009 hrs at phaleano.allbsd.org:/usr/obj/usr/src/sys/PHALEANO i386

>Description:

	Behavior of net.int6.ip6.accept_rtadv=1 is odd on 7.1R and
	later.	The environment and symptom are the following:

	1. The box has two NICs.  One has an address 2001:0db8:1::1/64
	   (NIC A), and another has 2001:0db8:2::1/64 (NIC B).	These
	   addresses are assigned manually ($ipv6_ifconfig in
	   rc.conf).  Each NIC has a link-local address since
	   $ipv6_enable="YES" in rc.conf.

	2. RA is periodically sent to the network 2001:0db8:1::1/64
	   (NIC A) by a router on the subnet.  The RA includes a
	   source link-layer address option only.

	When setting net.inet6.ip6.accept_rtadv=1 in this
	configuration, I expected the box assigns an autoconf IPv6
	address (prefix 2001:0db8:1::/64 + EUI64) to NIC A and an
	default route based on source link-layer address in the RA
	packet.	 Actually, these two were done as expected.  However,
	after the autoconf address and default route are assigned,
	routes for NIC B disappeared from the routing table.  More
	specifically, a cloning route "2001:0db8:2::1/64 -> link#2"
	was removed for some reason.

>How-To-Repeat:

	Enable net.inet6.ip6.accept_rtadv=1 on a box with two NICs.
	7.0R works fine, but 7.1R and 7.2R remove cloning route of a
	NIC which did not receive RA unconditionally.

>Fix:

	No idea.
>Release-Note:
>Audit-Trail:
>Unformatted: