br-fw-admin: Multicast hash table chain limit reached:

[Alexander Nevenchannyy]

[root@fuel ~]# fuel --fuel-version
DEPRECATION WARNING: file /etc/fuel/client/config.yaml is found and will be used as a source for settings. However, it deprecated and will not be used by default in the ongoing version of python-fuelclient.
api: '1.0'
astute_sha: 3f1ece0318e5e93eaf48802fefabf512ca1dce40
auth_required: true
build_id: 2015-03-26_21-32-43
build_number: '233'
feature_groups:
- mirantis
fuellib_sha: 9c7716bc2ce6075065d7d9dcf96f4c94662c0b56
fuelmain_sha: 320b5f46fc1b2798f9e86ed7df51d3bda1686c10
nailgun_sha: b163f6fc77d6639aaffd9dd992e1ad96951c3bbf
ostf_sha: a4cf5f218c6aea98105b10c97a4aed8115c15867
production: docker
python-fuelclient_sha: e5e8389d8d481561a4d7107a99daae07c6ec5177
release: '6.1'
release_versions:
  2014.2-6.1:
    VERSION:
      api: '1.0'
      astute_sha: 3f1ece0318e5e93eaf48802fefabf512ca1dce40
      build_id: 2015-03-26_21-32-43
      build_number: '233'
      feature_groups:
      - mirantis
      fuellib_sha: 9c7716bc2ce6075065d7d9dcf96f4c94662c0b56
      fuelmain_sha: 320b5f46fc1b2798f9e86ed7df51d3bda1686c10
      nailgun_sha: b163f6fc77d6639aaffd9dd992e1ad96951c3bbf
      ostf_sha: a4cf5f218c6aea98105b10c97a4aed8115c15867
      production: docker
      python-fuelclient_sha: e5e8389d8d481561a4d7107a99daae07c6ec5177
      release: '6.1'

Cluster configuration: Ubunru 14.04, 3 controllers + 197 compute nodes with ceph

While running Full rally tests, we found in dmesg logs errors like:
[11171.821270] br-fw-admin: Multicast hash table chain limit reached: eth0
[11171.821350] br-fw-admin: Cannot rehash multicast hash table, disabling snooping: eth0, 389, -22
[48570.396018] br-ex: Multicast hash table chain limit reached: eth4

[Bogdan Dobrelya (bogdando)]

Please provide logs and elaborate how this issue impacts the Openstack environment

[Mike Scherbakov (mihgen)]

We need to investigate why we've got this error, i.e. what was actually using multicast at all and in such a way that we've got hash limit. According to the code, https://github.com/opennetworklinux/linux-3.8.13/blob/master/net/bridge/br_multicast.c#L534, multicast being turned off after limit is reached (as I can understand from the code, I might be wrong)