On 5/30/23 20:27, Mark Michelson wrote:
> Thanks Ihar and Dumitru.
> 
> I applied this series to main and branch-23.06. I encountered conflicts

Thanks, Mark!  Unfortunately, I had missed the fact that a new test had
been added in the meantime and that we had to update the table numbers
for that one too.  CI was failing because of that.

I posted a fix for it:

https://patchwork.ozlabs.org/project/ovn/patch/[email protected]/

Regards,
Dumitru

> when trying to apply this to branch-23.03, specifically with patch 4. I
> suspect a lot of this is due to the fact that the tiered ACL changes are
> not present in branch-23.03, so
> 
> * The table numbers don't work out the same in some cases.
> * ACL flow actions are different prior to 23.06.
> 
> If you can post backport versions of the patches for 23.03 and below,
> that would be great, Ihar.
> 
> Thanks,
> Mark Michelson
> 
> On 5/23/23 17:55, Ihar Hrachyshka wrote:
>> This series fixes a non-optimal behavior with some multichassis ports.
>>
>> Specifically,
>>
>> - when a multichassis port belongs to a switch that also has a localnet
>>    port,
>> - because ingress and egress traffic for the port is funnelled through
>>    tunnels to guarantee delivery of packets to all chassis that host the
>>    port,
>> - because tunnels add overhead to each funnelled packet,
>> - leaving less space for actual packets,
>>
>> ... the effective MTU of the path for multichassis ports is reduced by
>> the size that takes the tunnel to wrap a packet around. (This depends on
>> the type of tunnel, also on IP version of the tunnel.)
>>
>> When this happens, the port and its peers are not notified about the
>> reduced MTU for the path to the port, effectively blackholing some of
>> the larger packets.
>>
>> This patch series makes OVN detect these scenarios and handle them as
>> follows:
>>
>> - for all multichassis ports, 4 flows are added - for inport and
>>    outport matches - to detect "too-big" IP packets;
>> - for all "too-big" packets, 2 flows are added to produce a ICMP
>>    Fragmentation Needed (for IPv4) or Too Big (for IPv6) packet and
>>    return it to the offending sender.
>>
>> The proposed implementation is isolated in ovn-controller. An
>> alternative would be to implement flows producing ICMP errors via the
>> existing Logical_Flow action icmp4_error, as is done for router ports.
>> In this case, the 4 flows that detect "too-big" packets would still have
>> to reside in ovn-controller because of limitations of the current OVN
>> port model, namely lack of `mtu` as an attribute of OVN logical port.
>>
>> Caveats: this works for IP traffic only. The party receiving the ICMP
>> error should handle it by temporarily lowering the MTU used to reach the
>> port. Behavior may depend on protocol implementation of the offending
>> peer as well as its networking stack configuration.
>>
>> This patch series was successfully tested with Linux kernel 6.0.8.
>>
>> This patch series is designed to simplify backporting process. It is
>> split in logical pieces to simplify cherry-picking. I consider the
>> original behavior described at the start of the cover letter a bug and
>> worth a backport.
>>
>> ---
>> v1: - initial version.
>> v2: - more system test cases adjusted to new table numbers for egress
>>        pipeline;
>>      - switch from xxd to coreutils (tr, head) tools to avoid a new
>>        dependency;
>>      - adjusted a comment in the new test case to avoid "migrator"
>>        terminology that makes no sense outside live migration context -
>>        which is not the only potential use case for multichassis ports;
>>      - guard the new test case with HAVE_SCAPY;
>>      - nit: rewrapped some lines in patch 6/7 to avoid unnecessary line
>>        changes;
>>      - added a NEWS entry for patch 6/7 that implements the core of the
>>        feature;
>>      - rebased to latest main.
>> v3: - expose and reuse lib/actions.c:encode_[start|finish]_controller_op
>>        functions;
>>      - reuse ETH_HEADER_LEN, IP_HEADER_LEN, and IPV6_HEADER_LEN from
>>        ovs:lib/packets.h;
>>      - add a comment for REGBIT_PKT_LARGER that mentions that the
>>        register is also used in OFTABLE_OUTPUT_LARGE_PKT_DETECT table;
>>      - squash the patch that makes if-status-mgr track changes to
>>        interface mtu into the patch that introduces the mtu field in the
>>        manager;
>>      - doc: don't describe path discovery flows in the patch that
>>        introduces new tables (only in the patch that actually implements
>>        the flows);
>>      - nit: use MAX to shave off several lines of code;
>>      - nit: remove redundant if_status_mgr_iface_get_mtu declaration from
>>        a header file;
>>      - rebased to latest main;
>>      - updated acks based on latest review comments.
>> v4: - fix compilation issue in the middle of the series due to previous
>>        commit rearrangement.
>> v5: - introduce a new if-status-mgr input to pflow_output, then process
>>        OVS interface updates inside if-status-mgr handlers.
>>      - if-status-mgr: remove set_mtu public function, instead other
>>        modules should call to if_status_mgr_iface_update. This allows the
>>        callers to not care which particular fields if-status-mgr would
>>        like to persist from the OVS record, keeping concerns separated.
>> v6: - update more tests in ovn-controller.at to reflect new table
>>        numbers.
>> v7: - remove ovs submodule bump that creeped in by mistake.
>> ---
>>
>> Ihar Hrachyshka (5):
>>    Track ip version of tunnel in chassis_tunnel struct
>>    Track interface MTU in if-status-mgr
>>    if-status: track interfaces for additional chassis
>>    Add new egress tables to accommodate for too-big packets handling
>>    Implement MTU Path Discovery for multichassis ports
>>
>>   NEWS                        |   6 +
>>   controller/binding.c        |  48 +--
>>   controller/binding.h        |   4 +
>>   controller/if-status.c      |  48 ++-
>>   controller/if-status.h      |   8 +-
>>   controller/lflow.c          |   4 +-
>>   controller/lflow.h          |  49 +--
>>   controller/local_data.c     |   2 +
>>   controller/local_data.h     |   1 +
>>   controller/ovn-controller.c | 122 +++++++
>>   controller/ovsport.c        |   9 +
>>   controller/ovsport.h        |   2 +
>>   controller/physical.c       | 337 ++++++++++++++++++--
>>   controller/physical.h       |   2 +
>>   controller/pinctrl.c        |   8 +-
>>   include/ovn/actions.h       |   3 +
>>   lib/actions.c               |   4 +-
>>   lib/ovn-util.h              |   7 +
>>   northd/northd.c             |   2 +
>>   ovn-architecture.7.xml      |  76 ++---
>>   tests/ovn-controller.at     | 298 +++++++++---------
>>   tests/ovn.at                | 611 +++++++++++++++++++++++++++---------
>>   tests/system-ovn-kmod.at    |   2 +-
>>   tests/system-ovn.at         |   8 +-
>>   24 files changed, 1241 insertions(+), 420 deletions(-)
>>
> 
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