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[Bug 1799599] [NEW] neutron creates wrong vlan_tci filter in flow for gateway on flat external network and drops all PCP / QOS frames

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Public bug reported:

neutron creates wrong vlan_tci filter in flow for gateway on flat
external network


How reproducible:

Before:
~~~
[root@overcloud-controller-0 ~]# ovs-ofctl dump-flows br-int
 cookie=0xe8434ff964f0cbac, duration=6774.388s, table=0, n_packets=1, n_bytes=78, priority=3,in_port="int-br-ex",dl_vlan=905 actions=mod_vlan_vid:1,resubmit(,60)
 cookie=0xe8434ff964f0cbac, duration=8311.490s, table=0, n_packets=613, n_bytes=47932, priority=2,in_port="int-br-ex" actions=drop
 cookie=0xe8434ff964f0cbac, duration=8311.755s, table=0, n_packets=1566, n_bytes=148447, priority=0 actions=resubmit(,60)
 cookie=0xe8434ff964f0cbac, duration=8311.757s, table=23, n_packets=0, n_bytes=0, priority=0 actions=drop
 cookie=0xe8434ff964f0cbac, duration=8311.752s, table=24, n_packets=0, n_bytes=0, priority=0 actions=drop
 cookie=0xe8434ff964f0cbac, duration=8311.754s, table=60, n_packets=1567, n_bytes=148525, priority=3 actions=NORMAL
~~~

Create router on flat network:
~~~
openstack network create provider2 --provider-network-type flat --provider-physical-network datacentre  --share --external
openstack subnet create --network provider2 --subnet-range 10.1.0.0/24 provider2-subnet
openstack router create router2
openstack router set --external-gateway provider2 router2
~~~

After:
~~~
[root@overcloud-controller-0 ~]# ovs-ofctl dump-flows br-int
 cookie=0xe8434ff964f0cbac, duration=7228.959s, table=0, n_packets=2, n_bytes=156, priority=3,in_port="int-br-ex",dl_vlan=905 actions=mod_vlan_vid:1,resubmit(,60)
 cookie=0xe8434ff964f0cbac, duration=45.778s, table=0, n_packets=0, n_bytes=0, priority=3,in_port="int-br-ex",vlan_tci=0x0000/0x1fff actions=mod_vlan_vid:3,resubmit(,60)   #   <-------------------------------- issue in this rule
 cookie=0xe8434ff964f0cbac, duration=8766.061s, table=0, n_packets=645, n_bytes=50428, priority=2,in_port="int-br-ex" actions=drop
 cookie=0xe8434ff964f0cbac, duration=8766.326s, table=0, n_packets=1588, n_bytes=150603, priority=0 actions=resubmit(,60)
 cookie=0xe8434ff964f0cbac, duration=8766.328s, table=23, n_packets=0, n_bytes=0, priority=0 actions=drop
 cookie=0xe8434ff964f0cbac, duration=8766.323s, table=24, n_packets=0, n_bytes=0, priority=0 actions=drop
 cookie=0xe8434ff964f0cbac, duration=8766.325s, table=60, n_packets=1590, n_bytes=150759, priority=3 actions=NORMAL
[root@overcloud-controller-0 ~]# 
~~~

The problematic rule is:
~~~
 cookie=0xe8434ff964f0cbac, duration=45.778s, table=0, n_packets=0, n_bytes=0, priority=3,in_port="int-br-ex",vlan_tci=0x0000/0x1fff actions=mod_vlan_vid:3,resubmit(,60)   #   <-------------------------------- issue in this rule
~~~

This filter here:
vlan_tci=0x0000/0x1fff

Needs to be:
vlan_tci=0x0000/0x0fff

The existing filter works fine for frames without a dot1q tag. The
filter does not work for dot1q tagged frames on VLAN 0. E.g., it COP is
modified, frames with VLAN 0 and a COP value will be dropped.

~~~
man ovs-ofctl
(...)
The value that vlan_tci matches against is 0 for a packet that has no 802.1Q header.  Otherwise, it is the TCI value from the 802.1Q header with the CFI bit (with value 0x1000) forced to 1.
~~~

We should not be filtering on the DCI bit, as it can be 0 or 1.

Additional info:
See https://bugzilla.redhat.com/1635909 for further details

** Affects: neutron
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1799599

Title:
   neutron creates wrong vlan_tci filter in flow for gateway on flat
  external network and drops all PCP / QOS frames

Status in neutron:
  New

Bug description:
  neutron creates wrong vlan_tci filter in flow for gateway on flat
  external network


  How reproducible:

  Before:
  ~~~
  [root@overcloud-controller-0 ~]# ovs-ofctl dump-flows br-int
   cookie=0xe8434ff964f0cbac, duration=6774.388s, table=0, n_packets=1, n_bytes=78, priority=3,in_port="int-br-ex",dl_vlan=905 actions=mod_vlan_vid:1,resubmit(,60)
   cookie=0xe8434ff964f0cbac, duration=8311.490s, table=0, n_packets=613, n_bytes=47932, priority=2,in_port="int-br-ex" actions=drop
   cookie=0xe8434ff964f0cbac, duration=8311.755s, table=0, n_packets=1566, n_bytes=148447, priority=0 actions=resubmit(,60)
   cookie=0xe8434ff964f0cbac, duration=8311.757s, table=23, n_packets=0, n_bytes=0, priority=0 actions=drop
   cookie=0xe8434ff964f0cbac, duration=8311.752s, table=24, n_packets=0, n_bytes=0, priority=0 actions=drop
   cookie=0xe8434ff964f0cbac, duration=8311.754s, table=60, n_packets=1567, n_bytes=148525, priority=3 actions=NORMAL
  ~~~

  Create router on flat network:
  ~~~
  openstack network create provider2 --provider-network-type flat --provider-physical-network datacentre  --share --external
  openstack subnet create --network provider2 --subnet-range 10.1.0.0/24 provider2-subnet
  openstack router create router2
  openstack router set --external-gateway provider2 router2
  ~~~

  After:
  ~~~
  [root@overcloud-controller-0 ~]# ovs-ofctl dump-flows br-int
   cookie=0xe8434ff964f0cbac, duration=7228.959s, table=0, n_packets=2, n_bytes=156, priority=3,in_port="int-br-ex",dl_vlan=905 actions=mod_vlan_vid:1,resubmit(,60)
   cookie=0xe8434ff964f0cbac, duration=45.778s, table=0, n_packets=0, n_bytes=0, priority=3,in_port="int-br-ex",vlan_tci=0x0000/0x1fff actions=mod_vlan_vid:3,resubmit(,60)   #   <-------------------------------- issue in this rule
   cookie=0xe8434ff964f0cbac, duration=8766.061s, table=0, n_packets=645, n_bytes=50428, priority=2,in_port="int-br-ex" actions=drop
   cookie=0xe8434ff964f0cbac, duration=8766.326s, table=0, n_packets=1588, n_bytes=150603, priority=0 actions=resubmit(,60)
   cookie=0xe8434ff964f0cbac, duration=8766.328s, table=23, n_packets=0, n_bytes=0, priority=0 actions=drop
   cookie=0xe8434ff964f0cbac, duration=8766.323s, table=24, n_packets=0, n_bytes=0, priority=0 actions=drop
   cookie=0xe8434ff964f0cbac, duration=8766.325s, table=60, n_packets=1590, n_bytes=150759, priority=3 actions=NORMAL
  [root@overcloud-controller-0 ~]# 
  ~~~

  The problematic rule is:
  ~~~
   cookie=0xe8434ff964f0cbac, duration=45.778s, table=0, n_packets=0, n_bytes=0, priority=3,in_port="int-br-ex",vlan_tci=0x0000/0x1fff actions=mod_vlan_vid:3,resubmit(,60)   #   <-------------------------------- issue in this rule
  ~~~

  This filter here:
  vlan_tci=0x0000/0x1fff

  Needs to be:
  vlan_tci=0x0000/0x0fff

  The existing filter works fine for frames without a dot1q tag. The
  filter does not work for dot1q tagged frames on VLAN 0. E.g., it COP
  is modified, frames with VLAN 0 and a COP value will be dropped.

  ~~~
  man ovs-ofctl
  (...)
  The value that vlan_tci matches against is 0 for a packet that has no 802.1Q header.  Otherwise, it is the TCI value from the 802.1Q header with the CFI bit (with value 0x1000) forced to 1.
  ~~~

  We should not be filtering on the DCI bit, as it can be 0 or 1.

  Additional info:
  See https://bugzilla.redhat.com/1635909 for further details

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Follow ups

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