[Bug 1896938] [NEW] strange IPv6 NDP behaviour with OVN on Focal

[Frode Nordahl]

Public bug reported:

[Impact]
The issue I'm seeing is that if I have multiple OVN routers connected to the same external OVS uplink switch (which in turn is connected via veth to a native linux bridge), when NDP solicit packets are sent from the native linux bridge into the logical OVN switch, for some reason every OVN router that is connected to the OVN switch retransmits the NDP packet from its own MAC address. Which in turn causes them all to receive another NDP packet, which are then all retransmitted (a flood then ensues until OVS rate limiting takes effect).

This occurs even for IPs that do not exist on the network that the OVN
routers dont know anything about.

It doesn't happen for ARP, nor does it occur in Groovy.
[Test Case]

[Regression Potential]

[Other Info]

** Affects: ovn (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1896938

Title:
  strange IPv6 NDP behaviour with OVN on Focal

Status in ovn package in Ubuntu:
  New

Bug description:
  [Impact]
  The issue I'm seeing is that if I have multiple OVN routers connected to the same external OVS uplink switch (which in turn is connected via veth to a native linux bridge), when NDP solicit packets are sent from the native linux bridge into the logical OVN switch, for some reason every OVN router that is connected to the OVN switch retransmits the NDP packet from its own MAC address. Which in turn causes them all to receive another NDP packet, which are then all retransmitted (a flood then ensues until OVS rate limiting takes effect).

  This occurs even for IPs that do not exist on the network that the OVN
  routers dont know anything about.

  It doesn't happen for ARP, nor does it occur in Groovy.
  [Test Case]

  [Regression Potential]

  [Other Info]

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