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[Andy Whitcroft <apw@xxxxxxxxxxxxx>]

** Changed in: linux (Ubuntu)
   Importance: Undecided => High

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https://bugs.launchpad.net/bugs/1597806

Title:
  ipv6 neighbor discovery broken (on a bridge)

Status in linux package in Ubuntu:
  Confirmed

Bug description:
  I have a xenial (4.4.0-24-generic) machine that loses ipv6
  connectivity every time I reboot the gateway it uses.

  br0 is a bridge which has eth0.2 as its only member, with (currently) 6 "scope global temporary deprecated dynamic" (privacy) addresses, and:
      inet6 2601:282:8100:3500:24c:40ff:fe1a:c570/64 scope global mngtmpaddr dynamic
         valid_lft 300sec preferred_lft 120sec

  The tcpdump trace on against eth0.2 of the broken machine:
  http://paste.ubuntu.com/18170606/ (fe80::1 is the gateway)

  http://paste.ubuntu.com/18173670/ is the output of lspci -vvn on one
  of the (quad) interfaces on the machine.

  Setting the bridge to promisc and turning it back off works around the
  issue.  Tcpdump on the underlying eth0.2 does not.

  On another (yakkety) box, running 4-4-0.14-generic, I also see the
  problem: that interface is also br0, with eth0 (untagged) as its only
  member.

  All of the above leads me to believe that the kernel is not managing
  to correctly set up (at least some?) of the multicast addresses it
  needs to listen to on the bridge.

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