Add experimental-field-mask flag

Follow-up to change in cilium exposing new experimental field in
requests: cilium/cilium#23198

Usage example:
  hubble observe --experimental-field-mask time,verdict

Signed-off-by: Aleksander Mistewicz <amistewicz@google.com>

cmd/observe/flows.go

@@ -30,6 +30,7 @@ import (
 	"github.com/spf13/viper"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
+	"google.golang.org/protobuf/types/known/fieldmaskpb"
 	"google.golang.org/protobuf/types/known/timestamppb"
 	"gopkg.in/yaml.v3"
 )
@@ -701,6 +702,16 @@ func getFlowsRequest(ofilter *flowFilter, allowlist []string, denylist []string)
 		First:     first,
 	}
 
+	if len(experimentalOpts.fieldMask) > 0 {
+		fm, err := fieldmaskpb.New(&flowpb.Flow{}, experimentalOpts.fieldMask...)
+		if err != nil {
+			return nil, fmt.Errorf("failed to construct field mask: %w", err)
+		}
+		req.Experimental = &observerpb.GetFlowsRequest_Experimental{
+			FieldMask: fm,
+		}
+	}
+
 	return req, nil
 }
 

cmd/observe/flows_test.go

@@ -16,6 +16,7 @@ import (
 	"github.com/cilium/hubble/pkg/defaults"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"google.golang.org/protobuf/types/known/fieldmaskpb"
 	"google.golang.org/protobuf/types/known/timestamppb"
 )
 
@@ -125,3 +126,24 @@ denylist:
 	assert.NoError(t, err)
 	assert.Equal(t, expected, out)
 }
+
+func Test_getFlowsRequest_ExperimentalFieldMask_valid(t *testing.T) {
+	selectorOpts.until = ""
+	experimentalOpts.fieldMask = []string{"time", "verdict"}
+	filter := newFlowFilter()
+	req, err := getFlowsRequest(filter, nil, nil)
+	assert.NoError(t, err)
+	assert.Equal(t, &observerpb.GetFlowsRequest{
+		Number: 20,
+		Experimental: &observerpb.GetFlowsRequest_Experimental{
+			FieldMask: &fieldmaskpb.FieldMask{Paths: []string{"time", "verdict"}},
+		},
+	}, req)
+}
+
+func Test_getFlowsRequest_ExperimentalFieldMask_invalid(t *testing.T) {
+	experimentalOpts.fieldMask = []string{"time", "verdict", "invalid-field"}
+	filter := newFlowFilter()
+	_, err := getFlowsRequest(filter, nil, nil)
+	assert.ErrorContains(t, err, "invalid-field")
+}

cmd/observe/observe.go

@@ -42,6 +42,10 @@ var (
 		inputFile       string
 	}
 
+	experimentalOpts struct {
+		fieldMask []string
+	}
+
 	printer *hubprinter.Printer
 
 	// selector flags
@@ -150,6 +154,9 @@ func init() {
 
 	otherFlags.StringVar(&otherOpts.inputFile, "input-file", "",
 		"Query flows from this file instead of the server. Use '-' to read from stdin.")
+
+	otherFlags.StringSliceVar(&experimentalOpts.fieldMask, "experimental-field-mask", nil,
+		"Experimental: Comma-separated list of fields for mask. Fields not in the mask will be removed from server response.")
 }
 
 // New observer command.