Just got back and saw this.
you should filter out loopback packets at the driver level. It's not
possible to do it at IP / layer-3. It may be possible at layer-2 but I'm
not sure it's the best way to do it.
You can enable reception of all multicast packets if you want. Upper
layers will filter out packets to groups we are not subscribed to. The
hardware filter just offloads the CPU. But it will work either way.
Cheers
Ivan
Date: Thu, 30 Jun 2016 14:00:27 +0200
From: chrysn <chr...@fsfe.org>
To: lwip-users@nongnu.org
Subject: [lwip-users] driver clarifications for ipv6: loopback,
multicast
Message-ID: <20160630120027.ga13...@hephaistos.amsuess.com>
Content-Type: text/plain; charset="us-ascii"
hi,
as of fixing my enc28j60 driver[1] to work well with ipv6 as well,
i've
stumbled over some corners where there might be a better solution i
haven't found.
* when operating in half duplex mode, ipv6 address autoconfiguration
failed because i had missed to configure the network card to
suppress
loopback of sent packages; as a result, the returning nd6 packages
were interpreted as another device's attempt to use the same one.
is it a general requirement of lwip netif drivers to suppress sent
packages? or should the nd6 have checked for whether the package
comes
from an own netif?
* i've enabled unconditional reception of multicasts for now. i could
leave it off by default and fully implement igmp_mac_filter and
mld_mac_filter, but i could still not know if i missed any other
potential indications of protocol's willingness to receive
multicast.
is there any interface i cen implement to be informed of the general
need to receive multicasts?
best regards
chrysn
[1]
https://gitlab.com/enc28j60driver/enc28j60driver/commit/f60093dd58eabaaaa92c0c87b172d1e5310e08f7
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