Pre-submission checklist

• I've ran the linters locally and fixed lint errors related to the files I modified in this PR. You can install the linters by running pip install -r requirements-dev.txt && pre-commit install
• pre-commit run

Summary

What: Delete-side counterparts for the copp config commands:

• delete copp cpu-queue <id> — removes the whole sw.cpuQueues[] entry. Refused while rxReason mappings (rxReasonToQueueOrderedList) or cpu-traffic-policy actions (send-to-queue, user-defined-trap) still reference the queue id; the error names each referencing entry.
• delete copp reason <reason-name> — removes the rxReasonToQueueOrderedList entry.

Why: The config-side copp commands landed without a way to unset what they set.

Notes

Whole-queue delete is not undoable by the CLI

delete copp cpu-queue <id> erases the entire cpuQueues[] entry, matching delete qos default-queue-config <id>, which erases a whole entry from defaultPortQueues — same list<PortQueue> shape.

The difference is on the config side. config qos default-queue-config can write reserved-bytes, shared-bytes, weight, scaling-factor, scheduling, stream-type, buffer-pool-name and AQM entries via utils::applyPortQueueConfig, so a deleted default queue can be rebuilt by hand. config copp cpu-queue writes only name and portQueueRate, so a deleted cpu-queue cannot.

PortQueue has 17 fields and the CLI can set two of them (name, and portQueueRate via rate-limit). streamType and scheduling are non-optional in thrift, so a recreated queue silently picks up their zero values. A platform agent.conf ships queue 9 as:

{ "id": 9, "name": "cpuQueue-high", "scheduling": 1, "streamType": 1 }

scheduling 1 is STRICT_PRIORITY, streamType 1 is MULTICAST. Delete it and recreate it and you get scheduling 0 (WEIGHTED_ROUND_ROBIN) and streamType 0 (UNICAST), with no command to set either back. The high-priority CPU queue would start round-robining.

So: delete a platform-provisioned cpu-queue only when you want it gone for good. Queues you created yourself are safe to delete and recreate.

To change a name or rate limit, no delete is involved — config overwrites in place:

fboss2-dev config copp cpu-queue 9 name some-name
fboss2-dev config copp cpu-queue 9 rate-limit pps 300

delete copp reason takes no queue id

Config is config copp reason <reason> queue <id>, delete is delete copp reason <reason>. rxReasonToQueueOrderedList holds at most one entry per reason — config overwrites an existing reason rather than appending a second entry — so the reason name alone identifies the entry, and delete looks it up that way:

// CmdDeleteCoppReason.cpp
auto it = std::find_if(
    list.begin(), list.end(), [&args](const cfg::PacketRxReasonToQueue& e) {
      return *e.rxReason() == args.getReason();
    });

Passing a queue id is rejected rather than ignored (->expected(1), plus the arg parser throws on a second token). The queue id shows up on the way out instead — Deleted reason ARP -> queue 9 mapping — read off the entry being removed.

Re-pointing a reason at a different queue is a config, not a delete: config copp reason arp queue 5 prints Updated reason ARP -> queue 5. Delete is for taking the reason off the CPU path entirely.

Clearing what blocks a queue delete

The refusal message lists each referrer: reason <NAME> for rxReason mappings, matcher '<name>' send-to-queue / matcher '<name>' user-defined-trap for cpu-traffic-policy actions (findQueueReferences(), CmdDeleteCoppCpuQueue.cpp). Only those two action types carry a queue id, so only they can block.

Clear reasons with delete copp reason <reason>; clearing a blocking action needs the cpu-traffic-policy action delete from #1379:

fboss2-dev delete copp cpu-traffic-policy match <matcher> action send-to-queue
fboss2-dev delete copp cpu-queue 9

The deprecated rxReasonToCPUQueue map is ignored entirely (per review — the field is no longer used).

Test Plan

Unit tests — 13 added by this PR (7 in CmdDeleteCoppCpuQueueTestFixture, 6 across the CmdDeleteCoppReason* fixtures), all passing:

$ bazel-bin/fboss/cli/fboss2/test/config/cmd_config_test --gtest_filter='CmdDeleteCoppCpuQueueTestFixture.*:CmdDeleteCoppReason*'
[==========] Running 13 tests from 4 test suites.
[----------] 7 tests from CmdDeleteCoppCpuQueueTestFixture (685 ms total)
[----------] 4 tests from CmdDeleteCoppReasonTestFixture (310 ms total)
[----------] 1 test from CmdDeleteCoppReasonNoPolicyFixture (99 ms total)
[----------] 1 test from CmdDeleteCoppReasonNoListFixture (89 ms total)
[==========] 13 tests from 4 test suites ran. (1185 ms total)
[  PASSED  ] 13 tests.

Integration tests on a freshly imaged T1 device — 2/2 pass)
One end-to-end test per command, both unconditional .
Each test creates what it deletes (config copp reason creates cpuTrafficPolicy and rxReasonToQueueOrderedList when absent) and removes it again, so nothing touches a live CoPP policy.

$ ./fboss2_integration_test --gtest_filter='DeleteCoppTest.*'
[==========] Running 2 tests from 1 test suite.
[ RUN      ] DeleteCoppTest.DeleteWholeCpuQueue
DeleteCoppTest.cpp:119] Creating scratch cpu-queue 3
[       OK ] DeleteCoppTest.DeleteWholeCpuQueue (185 ms)
[ RUN      ] DeleteCoppTest.DeleteReasonMapping
DeleteCoppTest.cpp:150] Mapping reason eapol -> scratch cpu-queue 3
DeleteCoppTest.cpp:161] Deleting reason eapol
DeleteCoppTest.cpp:170] Removing scratch cpu-queue 3
[       OK ] DeleteCoppTest.DeleteReasonMapping (242 ms)
[==========] 2 tests from 1 test suite ran. (427 ms total)
[  PASSED  ] 2 tests.

$ fboss2-dev config session diff        # device left unchanged
No differences between current live config and session config.

Sample usage on the same device — note the refusal list shrinks as the referencing reason is deleted:

$ fboss2-dev delete copp cpu-queue 9
localhost: Thrift call failed: 'Cannot delete cpu-queue 9: still referenced by
reason NDP, reason ARP_RESPONSE, reason BGP, reason BGPV6, reason LACP, reason ARP.
Delete those references first.'

$ fboss2-dev delete copp reason arp
Deleted reason ARP -> queue 9 mapping

$ fboss2-dev config session diff
--- current live config
+++ session config
@@ -146,10 +146,6 @@
         {
           "queueId": 1,
           "rxReason": 0
-        },
-        {
-          "queueId": 9,
-          "rxReason": 1
-        }
       ]
     },

$ fboss2-dev delete copp cpu-queue 9
localhost: Thrift call failed: 'Cannot delete cpu-queue 9: still referenced by
reason NDP, reason ARP_RESPONSE, reason BGP, reason BGPV6, reason LACP.
Delete those references first.'

$ fboss2-dev config session clear
Config session cleared successfully.

Review Findings

Pre-publication review (7 reviewers + verifier, confidence >= 0.7) surfaced these findings; all are addressed in this PR:

• shared parsing helpers moved to a dedicated CoppUtils.{h,cpp} instead of living in the config command header
• user-defined-trap refusal branch gained a unit test
• duplicated not-found throw in the reason delete collapsed into one helper
• integration-test reason candidates use cfg::PacketRxReason enum values instead of bare ints