[Bug 2129005] Re: tc class show dev change of behavior for values of burst and cburst

[Jorge Merlino]

** Description changed:

- As detected by the ovn system testsuite the following test fails when
- upgrading iprotue2 from 6.14 to more recent versions:
+ [Impact] 
+ Patches on iproute2 changed the rounding math for the burst parameter and this made openvswitch autopkgtests fail as they expect specific values for the burst parameter.
+ A patch for iproute2 is being backported in LP #2125448 that includes this behavior change and autopkgtests are failing because of this issue.
  
-     egress qos
+ [Test Plan]
+ Running openvswitch autopkgtests without this patch should fail with the updated version of iproute2. After applying this patch tests should run successfully.
+ The tests have to be run using qemu as it needs full virtualization. For this first an image has to be created using:
  
- The command being executed by the testsuite is:
+ # autopkgtest-buildvm-ubuntu-cloud -r <release>
  
-     tc class show dev ovs-public
+ That should create an image file called autopkgtest-<release>-amd64.img
  
- And the printed value becomes:
+ Then, assuming that the openvswitch version to test is downloaded on the
+ openvswitch folder, the test is run by this command:
  
-     class htb 1:2 parent 1:fffe prio 0 rate 12Kbit ceil 34359Mbit burst
- 375000b cburst 374933b
+ autopkgtest openvswitch/ -U -- qemu autopkgtest-<release>-amd64.img
  
- While the expected output is:
+ To test with the iproute2 package in proposed from LP #2125448 the
+ command should be:
  
-     class htb 1:2 parent 1:fffe prio 0 rate 12Kbit ceil 34359Mbit burst
- 375000b cburst 373662b
+ autopkgtest openvswitch/ -U --apt-pocket=proposed=src:iproute2 -- qemu
+ autopkgtest-<release>-amd64.img\n
  
- The issue appears to be present in iproute2 versions 6.17.0-1,
- 6.16.0-1ubuntu2
- 
- Downgrading to 6.14.0-1ubuntu1 makes the problem go away.
+ [Where problems could occur]
+ The change in the tests makes them less restrictive with respect to the exact value of the burst parameter so every test that passed the previous tests should still pass them after the update

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https://bugs.launchpad.net/bugs/2129005

Title:
  tc class show dev change of behavior for values of burst and cburst

Status in iproute2 package in Ubuntu:
  New
Status in openvswitch package in Ubuntu:
  Fix Committed
Status in ovn package in Ubuntu:
  Fix Committed
Status in openvswitch source package in Jammy:
  New
Status in openvswitch source package in Noble:
  New
Status in openvswitch source package in Questing:
  New
Status in openvswitch source package in Resolute:
  Fix Committed

Bug description:
  [Impact] 
  Patches on iproute2 changed the rounding math for the burst parameter and this made openvswitch autopkgtests fail as they expect specific values for the burst parameter.
  A patch for iproute2 is being backported in LP #2125448 that includes this behavior change and autopkgtests are failing because of this issue.

  [Test Plan]
  Running openvswitch autopkgtests without this patch should fail with the updated version of iproute2. After applying this patch tests should run successfully.
  The tests have to be run using qemu as it needs full virtualization. For this first an image has to be created using:

  # autopkgtest-buildvm-ubuntu-cloud -r <release>

  That should create an image file called
  autopkgtest-<release>-amd64.img

  Then, assuming that the openvswitch version to test is downloaded on
  the openvswitch folder, the test is run by this command:

  autopkgtest openvswitch/ -U -- qemu autopkgtest-<release>-amd64.img

  To test with the iproute2 package in proposed from LP #2125448 the
  command should be:

  autopkgtest openvswitch/ -U --apt-pocket=proposed=src:iproute2 -- qemu
  autopkgtest-<release>-amd64.img\n

  [Where problems could occur]
  The change in the tests makes them less restrictive with respect to the exact value of the burst parameter so every test that passed the previous tests should still pass them after the update

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