[Bug 1840716] Re: Existing ingress qdisc gets removed from port

[Jorge Niedbalski]

** Also affects: openvswitch
   Importance: Undecided
       Status: New

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https://bugs.launchpad.net/bugs/1840716

Title:
  Existing ingress qdisc gets removed from port

Status in openvswitch:
  New
Status in openvswitch package in Ubuntu:
  New

Bug description:
  [Environment]

  OpenvSwitch
  Ubuntu Bionic

  [Description]

  The current netdev linux bridge implementation removes the tc ingress
  qdisc for an existing ovs bridge port.

  This issue is reproducible without neutron with a bare ovs bridge + a
  libvirt definition.

  Consider the following ovs bridge.

  root at bionic-test:/home/ubuntu# ovs-vsctl show
  b936ab43-ba83-4aa0-825d-5975e8b87270
  Bridge "ovs-br0"
  Port "ens7"
  Interface "ens7"
  Port "ovs-br0"
  Interface "ovs-br0"
  type: internal
  ovs_version: "2.9.2"

  root at bionic-test:/home/ubuntu# ip link
  3: ens7: <BROADCAST,MULTICAST> mtu 1500 qdisc noop master ovs-system state DOWN mode DEFAULT group default qlen 1000
  link/ether 52:54:00:84:60:6e brd ff:ff:ff:ff:ff:ff
  4: ovs-system: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
  link/ether ba:5b:46:3a:dd:ff brd ff:ff:ff:ff:ff:ff
  5: ovs-br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
  link/ether 3a:bf:0b:5c:87:4a brd ff:ff:ff:ff:ff:ff

  16: vnet1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc htb master ovs-system state UNKNOWN mode DEFAULT group default qlen 1000
  link/ether fe:54:00:ae:17:05 brd ff:ff:ff:ff:ff:ff

  root at bionic-test:/home/ubuntu# tc qdisc show dev vnet1
  qdisc htb 1: root refcnt 2 r2q 10 default 1 direct_packets_stat 0 direct_qlen 1000
  qdisc sfq 2: parent 1:1 limit 127p quantum 1514b depth 127 divisor 1024 perturb 10sec

  root at bionic-test:/home/ubuntu# tc class show dev vnet1
  class htb 1:1 root leaf 2: prio rate 1024Kbit ceil 2048Kbit burst 256Kb cburst 1599b

  root at bionic-test:/home/ubuntu# tc filter show dev vnet1 parent ffff:
  root at bionic-test:/home/ubuntu#

  Following is the interface definition:

  <interface type='bridge'>
  <mac address='52:54:00:ae:17:05'/>
  <source bridge='ovs-br0'/>
  <virtualport type='openvswitch'>
  <parameters interfaceid='86814ca6-615b-41cd-8d85-4873638d1b66'/>
  </virtualport>
  <bandwidth>
  <inbound average='128' peak='256' burst='256'/>
  <outbound average='128' peak='256' burst='256'/>
  </bandwidth>
  <model type='rtl8139'/>
  <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
  </interface>

  ---- 2nd case

  Through a direct linux bridge (not managed by ovs)

  <interface type='bridge'>
  <mac address='52:54:00:88:9d:0a'/>
  <source bridge='virbr0'/>
  <bandwidth>
  <inbound average='128' peak='256' burst='256'/>
  <outbound average='128' peak='256' burst='256'/>
  </bandwidth>
  <model type='virtio'/>
  <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
  </interface>

  root at bionic-test:/home/ubuntu# tc qdisc show dev vnet2
  qdisc htb 1: root refcnt 2 r2q 10 default 1 direct_packets_stat 0 direct_qlen 1000
  qdisc sfq 2: parent 1:1 limit 127p quantum 1514b depth 127 divisor 1024 perturb 10sec
  qdisc ingress ffff: parent ffff:fff1 ----------------

  root at bionic-test:/home/ubuntu# tc class show dev vnet2
  class htb 1:1 root leaf 2: prio rate 1024Kbit ceil 2048Kbit burst 256Kb cburst 1599b

  root at bionic-test:/home/ubuntu# tc filter show dev vnet2 parent ffff:
  filter protocol all pref 49152 u32 chain 0
  filter protocol all pref 49152 u32 chain 0 fh 800: ht divisor 1
  filter protocol all pref 49152 u32 chain 0 fh 800::800 order 2048 key ht 800 bkt 0 flowid :1 not_in_hw
  match 00000000/00000000 at 0
  police 0x1 rate 1024Kbit burst 256Kb mtu 64Kb action drop overhead 0b
  ref 1 bind 1

  [Suggested solution]

  If no tc rate limits have been provided for the port and there is an existing
  ingress qdisc already set that differs from provided limits, avoid resetting the existing ingress qdisc.

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