Fix data race in FQDN ruleSyncTracker

[tnqn]

ruleSyncTracker.Run() can update ruleSyncTracker.dirtyRules in-place, while ruleSyncTracker.getDirtyRules() returns the pointer of the set which could be read by other goroutines and leads to a data race like below:

WARNING: DATA RACE
Write at 0x00c000dd8180 by goroutine 276:
  runtime.mapdelete_faststr()
      /usr/local/go/src/runtime/map_faststr.go:301 +0x0
  k8s.io/apimachinery/pkg/util/sets.Set[go.shape.string].Delete()
      /root/go/pkg/mod/k8s.io/apimachinery@v0.26.4/pkg/util/sets/set.go:62 +0x2ae
  antrea.io/antrea/pkg/agent/controller/networkpolicy.(*ruleSyncTracker).Run()
      /root/antrea/pkg/agent/controller/networkpolicy/fqdn.go:570 +0x1d2
  antrea.io/antrea/pkg/agent/controller/networkpolicy.(*fqdnController).runRuleSyncTracker()
      /root/antrea/pkg/agent/controller/networkpolicy/fqdn.go:584 +0x4a
  antrea.io/antrea/pkg/agent/controller/networkpolicy.TestSyncDirtyRules.func1.4()
      /root/antrea/pkg/agent/controller/networkpolicy/fqdn_test.go:495 +0x44

Previous read at 0x00c000dd8180 by goroutine 271:
  reflect.maplen()
      /usr/local/go/src/runtime/map.go:1411 +0x0
  reflect.Value.lenNonSlice()
      /usr/local/go/src/reflect/value.go:1720 +0x324
  reflect.Value.Len()
      /usr/local/go/src/reflect/value.go:1709 +0x158f
  reflect.deepValueEqual()
      /usr/local/go/src/reflect/deepequal.go:139 +0x1571
  reflect.DeepEqual()
      /usr/local/go/src/reflect/deepequal.go:237 +0x38b
  github.com/stretchr/testify/assert.ObjectsAreEqual()
      /root/go/pkg/mod/github.com/stretchr/testify@v1.8.4/assert/assertions.go:65 +0x172
  github.com/stretchr/testify/assert.Equal()
      /root/go/pkg/mod/github.com/stretchr/testify@v1.8.4/assert/assertions.go:414 +0x1f7
  antrea.io/antrea/pkg/agent/controller/networkpolicy.TestSyncDirtyRules.func1()
      /root/antrea/pkg/agent/controller/networkpolicy/fqdn_test.go:517 +0xb6f
  testing.tRunner()
      /usr/local/go/src/testing/testing.go:1595 +0x238
  testing.(*T).Run.func1()
      /usr/local/go/src/testing/testing.go:1648 +0x44

The data race was introduced by #5566 so is not present in releases yet. The patch needs to be backported together with #5566.

[tnqn]

/test-all

[Dyanngg]

LGTM, thanks for the fix.

[antoninbas]

LGTM
We could also replace getDirtyRules (which has a single caller) with a new dirtyRulesIntersection function, to avoid the extra set copy, but I don't have a strong preference.

[tnqn]

We could also replace getDirtyRules (which has a single caller) with a new dirtyRulesIntersection function, to avoid the extra set copy, but I don't have a strong preference.

Thanks for the advice. In production the function will only be called in abnormal case (previous packetin not handled succussfullly) so its impact should be trival for now.