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From: Vladimir Oltean <olteanv@gmail.com>
To: David Ahern <dsahern@gmail.com>
Cc: netdev@vger.kernel.org
Subject: IPv6 multicast with VRF
Date: Wed, 20 Apr 2022 19:54:57 +0300	[thread overview]
Message-ID: <20220420165457.kd5yz6a6itqfcysj@skbuf> (raw)

Hi,

I don't have experience with either IPv6 multicast or VRF, yet I need to
send some IPv6 multicast packets from a device enslaved to a VRF, and I
don't really know what's wrong with the routing table setup.

The system is configured in the following way:

 ip link set dev eth0 up

 # The kernel kindly creates a ff00::/8 route for IPv6 multicast traffic
 # in the local table, and I think this is what makes multicast route
 # lookups find the egress device.
 ip -6 route show table local
local ::1 dev lo proto kernel metric 0 pref medium
local fe80::204:9fff:fe05:f4ab dev eth0 proto kernel metric 0 pref medium
multicast ff00::/8 dev eth0 proto kernel metric 256 pref medium

 ip -6 route get ff02::1
multicast ff02::1 dev eth0 table local proto kernel src fe80::204:9fff:fe05:f4ab metric 256 pref medium

 ip link add dev vrf0 type vrf table 3 && ip link set dev vrf0 up

 ip -4 route add table 3 unreachable default metric 4278198272

 ip -6 route add table 3 unreachable default metric 4278198272

 ip link set dev eth0 master vrf0

The problem seems to be that, although the "ff00::/8 dev eth0" route
migrates from table 255 to table 3, route lookups after this point fail
to find it and return -ENETUNREACH (ip6_null_entry).

 ip -6 route show table local
local ::1 dev lo proto kernel metric 0 pref medium

 ip -6 route show table main
::1 dev lo proto kernel metric 256 pref medium

 ip -6 route show table 3
local fe80::204:9fff:fe05:f4ab dev eth0 proto kernel metric 0 pref medium
fe80::/64 dev eth0 proto kernel metric 256 pref medium
multicast ff00::/8 dev eth0 proto kernel metric 256 pref medium
unreachable default dev lo metric 4278198272 pref medium

 ip -6 route get ff02::1
RTNETLINK answers: Network is unreachable

 ip -6 route get vrf vrf0 ff02::1
RTNETLINK answers: Network is unreachable

I'm not exactly sure what is missing?

             reply	other threads:[~2022-04-20 16:55 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-20 16:54 Vladimir Oltean [this message]
2022-04-20 18:59 ` IPv6 multicast with VRF David Ahern
2022-04-20 19:18   ` Vladimir Oltean
2022-04-20 20:40     ` David Ahern
2022-04-21  9:24       ` Vladimir Oltean
2022-04-21 23:44         ` David Ahern

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