[8.0-RC1] IPv6 multicast not received when ale0 not promiscuous

Hi,

I have an 8.0-RC1 amd64 system that cannot receive IPv6 multicast
traffic when ale0 (onboard and only NIC) is not in promiscuous mode.
When I run 'tcpdump icmp6' on the host, I see multicast neighbour
advertisements and router advertisements, and I can solicit a router
advertisement as well.  When tcpdump is not running or is running with
-p, no default route is learned, and with 'tcpdump -p', the RA and NA
packets aren't even captured.  I do see the outgoing solicitations and
unicast NS/NA.

I noticed this problem under 8.0-BETA4 (20090915) when I started
running v6 again after a few months of not doing so (first try on this
box, though), and it has continued in RC1 (csup RELENG_8 just a couple
hours ago).  Other v6-enabled hosts on the network have no problems,
including an OpenSolaris box that used to run 7-STABLE with sk(4) and
nfe(4) (one at a time), no problems with either OS or interface, and
an 8.0-BETA4 (20090915) i386 VirtualBox with an emulated em(4)
interface (82540EM) on the above OpenSolaris host.

Does this ring a bell with anyone?  Anything I should look for or try
before submitting a PR?

thanks,
Jeff


ale0_at_pci0:2:0:0:        class=0x020000 card=0x831c1043 chip=0x10261969
rev=0xb0 hdr=0x00
    vendor     = 'Attansic (Now owned by Atheros)'
    device     = 'PCI-E ETHERNET CONTROLLER  (AR8121/AR8113 )'
    class      = network
    subclass   = ethernet

# ifconfig ale0
ale0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
        options=319a<TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,TSO4,WOL_MCAST,WOL_MAGIC>
        ether 00:26:18:82:fc:65
        inet6 fe80::226:18ff:fe82:fc65%ale0 prefixlen 64 scopeid 0x1 
        inet6 2001:5c0:1104:7a00::1:1 prefixlen 64 
        inet 172.19.3.81 netmask 0xffffff00 broadcast 172.19.3.255
        media: Ethernet autoselect (100baseTX <full-duplex>)
        status: active

# egrep 'ale|v6' /etc/rc.conf
ifconfig_ale0=DHCP
ipv6_enable=YES
ipv6_ifconfig_ale0="2001:5c0:1104:7a00::1:1 prefixlen 64"
ipv6_default_interface=ale0

# netstat -rnf inet6
Routing tables

Internet6:
Destination                       Gateway                       Flags      Netif Expire
::/96                             ::1                           UGRS        lo0
::1                               ::1                           UH          lo0
::ffff:0.0.0.0/96                 ::1                           UGRS        lo0
2001:5c0:1104:7a00::/64           link#1                        U          ale0
2001:5c0:1104:7a00::1:1           link#1                        UHS         lo0
fe80::/10                         ::1                           UGRS        lo0
fe80::%ale0/64                    link#1                        U          ale0
fe80::226:18ff:fe82:fc65%ale0     link#1                        UHS         lo0
fe80::%lo0/64                     link#4                        U           lo0
fe80::1%lo0                       link#4                        UHS         lo0
fe80::%tun0/64                    link#5                        U          tun0
fe80::226:18ff:fe82:fc65%tun0     link#5                        UHS         lo0
ff01:1::/32                       fe80::226:18ff:fe82:fc65%ale0 U          ale0
ff01:4::/32                       ::1                           U           lo0
ff01:5::/32                       fe80::226:18ff:fe82:fc65%tun0 U          tun0
ff02::%ale0/32                    fe80::226:18ff:fe82:fc65%ale0 U          ale0
ff02::%lo0/32                     ::1                           U           lo0
ff02::%tun0/32                    fe80::226:18ff:fe82:fc65%tun0 U          tun0