feat: add Windows drop reasons (#406)

# Description

Please provide a brief description of the changes made in this pull
request.

Add drop reasons specifically to windows builds.

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- [ ] I have correctly attributed the author(s) of the code.
- [ ] I have tested the changes locally.
- [ ] I have followed the project's style guidelines.
- [ ] I have updated the documentation, if necessary.
- [ ] I have added tests, if applicable.

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## Additional Notes

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---

Please refer to the [CONTRIBUTING.md](../CONTRIBUTING.md) file for more
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pkg/utils/flow_utils.go

@@ -271,16 +271,8 @@ func AddDropReason(f *flow.Flow, meta *RetinaMetadata, dropReason uint32) {
 	// Retina drop reasons are different from the drop reasons available in flow library.
 	// We map the ones available in flow library to the ones available in Retina.
 	// Rest are set to UNKNOWN. The details are added in the metadata.
-	switch meta.GetDropReason() { //nolint:exhaustive // We are handling all the cases.
-	case DropReason_IPTABLE_RULE_DROP:
-		f.DropReasonDesc = flow.DropReason_POLICY_DENIED
-	case DropReason_IPTABLE_NAT_DROP:
-		f.DropReasonDesc = flow.DropReason_SNAT_NO_MAP_FOUND
-	case DropReason_CONNTRACK_ADD_DROP:
-		f.DropReasonDesc = flow.DropReason_UNKNOWN_CONNECTION_TRACKING_STATE
-	default:
-		f.DropReasonDesc = flow.DropReason_DROP_REASON_UNKNOWN
-	}
+
+	f.DropReasonDesc = GetDropReasonDesc(meta.GetDropReason())
 
 	f.EventType = &flow.CiliumEventType{
 		Type:    int32(api.MessageTypeDrop),

pkg/utils/utils_linux.go

@@ -10,6 +10,7 @@ import (
 	"syscall"
 	"unsafe"
 
+	"github.com/cilium/cilium/api/v1/flow"
 	"github.com/pkg/errors"
 	"github.com/vishvananda/netlink"
 	"golang.org/x/exp/maps"
@@ -113,3 +114,20 @@ func isDefaultRoute(route netlink.Route) bool {
 
 	return false
 }
+
+func GetDropReasonDesc(dr DropReason) flow.DropReason {
+	// Set the drop reason.
+	// Retina drop reasons are different from the drop reasons available in flow library.
+	// We map the ones available in flow library to the ones available in Retina.
+	// Rest are set to UNKNOWN. The details are added in the metadata.
+	switch dr { //nolint:exhaustive // We are handling all the cases.
+	case DropReason_IPTABLE_RULE_DROP:
+		return flow.DropReason_POLICY_DENIED
+	case DropReason_IPTABLE_NAT_DROP:
+		return flow.DropReason_SNAT_NO_MAP_FOUND
+	case DropReason_CONNTRACK_ADD_DROP:
+		return flow.DropReason_UNKNOWN_CONNECTION_TRACKING_STATE
+	default:
+		return flow.DropReason_DROP_REASON_UNKNOWN
+	}
+}

pkg/utils/utils_windows.go

@@ -0,0 +1,16 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+package utils
+
+import (
+	"github.com/cilium/cilium/api/v1/flow"
+)
+
+func GetDropReasonDesc(dr DropReason) flow.DropReason {
+	switch dr { //nolint:exhaustive // We are handling all the cases.
+	case DropReason_Drop_INET_FinWait2:
+		return flow.DropReason_UNKNOWN_CONNECTION_TRACKING_STATE
+	default:
+		return flow.DropReason_DROP_REASON_UNKNOWN
+	}
+}