Hi,
Yesterday, I noticed that one of my platforms had become unreachable
over IPv6. This platform is connected to a Clearfog, which uses
the Marvell 88e6176 switch.
The setup is:
(rest of network)
| | | | | | |
Source ---- Netgear switch ---- Clearfog switch ---- Target
^ ^ ^
lan1 lan5 eth2
port 4 port 0
Both the source and target could ping the IPv6 link-local address on
the clearfog, and IPv4 traffic was fine.
The source was attempting to ping the target, and the target had been
attempting to mount a NFS share over IPv6 (and failing.)
Statistics from the Clearfog switch - port 0 is the target, port 4 is
the netgear switch, port 5 is the CPU port:
Statistic Port 0 Port 1 Port 2 Port 3 Port 4 Port 5 Port 6
in_multicasts: 27670 0 0 14552 78196 1674 0
out_multicasts: 439 0 331 332 331 114860 334
As you can see, very few multicast packets have been sent out any of
the ports.
Running tcpdump on the source machine:
21:31:48.805654 xx:xx:xx:15:37:dd > 33:33:ff:00:00:05,
ethertype IPv6 (0x86dd), length 86:
fd8f:xxxx:xxxx:xxxx:222:68ff:fe15:37dd > ff02::1:ff00:5:
ICMP6, neighbor solicitation, who has
fd8f:xxxx:xxxx:xxxx:200:ff:fe00:5, length 32
tcpdump on the clearfog for port 4:
21:31:48.807640 xx:xx:xx:15:37:dd > 33:33:ff:00:00:05,
ethertype IPv6 (0x86dd), length 86:
fd8f:xxxx:xxxx:xxxx:222:68ff:fe15:37dd > ff02::1:ff00:5:
ICMP6, neighbor solicitation, who has
fd8f:xxxx:xxxx:xxxx:200:ff:fe00:5, length 32
The port connected to the target doesn't see these multicast messages
which are intended for it. However, I am able to see messages
multicasted from the target, which is trying to solicit a different
machine on my network:
21:33:22.394653 00:00:00:00:00:05 > 33:33:ff:10:1b:e6,
ethertype IPv6 (0x86dd), length 86:
fd8f:xxxx:xxxx:xxxx:200:ff:fe00:5 > ff02::1:ff10:1be6:
ICMP6, neighbor solicitation, who has
fd8f:xxxx:xxxx:xxxx:214:fdff:fe10:1be6, length 32
but these neighbour solicitations are also not forwarded to through
the switch to the rest of the network.
Tweaking the DSA switch port register 4 (which had a value of 0x0433)
to 0x043b resolved the issue - multicast traffic started to egress
these ports, and the neighbour solicitations then worked.
I thought maybe this was a 4.16 regression, but it seems my other
clearfog has a similar register setup, so I'm not sure. I'm pretty
sure that it used to work at some point, as I'm a heavy user of IPv6
internally, and I'm quite certain that I would have noticed a failure
such as this.
The setup on the target is eth2 is part of a Linux bridge device.
--
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up
According to speedtest.net: 8.21Mbps down 510kbps up
