kern/56948: eqos(4) never receives IPv6 mcast ethernet packets

[martin%NetBSD.org@localhost]

>Number:         56948
>Category:       kern
>Synopsis:       eqos(4) never receives IPv6 mcast ethernet packets
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Aug 01 10:05:01 +0000 2022
>Originator:     Martin Husemann
>Release:        NetBSD 9.99.99
>Organization:
The NetBSD Foundation, Inc.
>Environment:
System: NetBSD plug.duskware.de 9.99.99 NetBSD 9.99.99 (GENERIC64) #318: Wed Jul 27 18:16:42 CEST 2022 martin%seven-days-to-the-wolves.aprisoft.de@localhost:/work/src/sys/arch/evbarm/compile/GENERIC64 evbarm
Architecture: aarch64
Machine: evbarm
>Description:

When this machine configures IPv6 and I start using it (e.g. by a ping6 to
some outside machine) it does the standard NDP dance with the (fixed)
router:

10:39:39.905231 e2:0c:f9:36:da:cc (oui Unknown) > 33:33:ff:79:54:ca (oui Unknown), ethertype IPv6 (0x86dd), length 86: (hlim 255, next-header ICMPv6 (58) payload length: 32) 2001:470:1f0b:e84:e00c:f9ff:fe36:dacc > ff02::1:ff79:54ca: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has fe80::3ea6:2fff:fe79:54ca
          source link-address option (1), length 8 (1): e2:0c:f9:36:da:cc
            0x0000:  e20c f936 dacc
10:39:39.905981 3c:a6:2f:79:54:ca (oui Unknown) > e2:0c:f9:36:da:cc (oui Unknown), ethertype IPv6 (0x86dd), length 90: (hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::3ea6:2fff:fe79:54ca > 2001:470:1f0b:e84:e00c:f9ff:fe36:dacc: [icmp6 sum ok] ICMP6, neighbor advertisement, length 32, tgt is fe80::3ea6:2fff:fe79:54ca, Flags [router, solicited, override]
          destination link-address option (2), length 8 (1): 3c:a6:2f:79:54:ca
            0x0000:  3ca6 2f79 54ca

The neighbour solicitation is sent to the ethernet IPv6 multicast group ff,
with destination mac address prefix 33:33:ff:, while the reply is sent
to the unicast mac adress.

If after some time (neighbour chache expired on the router) I do the same
again, the router sends a neighbour solicitation for this machines public
IPv6 adress, again using the 33:33:ff: mac prefix for IPv6 multicast.
Same happens when I try to ping6 this machine from others on the local
network (using either the link local or the public IPv6 address).

The eqos(4) driver never receives any of the 33:33:ff:... destined
ethernet packets (even if a tcpdump is running, so the interface
should be in promiscous mode).

>How-To-Repeat:
s/a

>Fix:
n/a