[client, proxy] Add packet capture to debug bundle and CLI

client/Dockerfile

@@ -17,6 +17,7 @@ ENV \
     NETBIRD_BIN="/usr/local/bin/netbird" \
     NB_LOG_FILE="console,/var/log/netbird/client.log" \
     NB_DAEMON_ADDR="unix:///var/run/netbird.sock" \
+    NB_ENABLE_CAPTURE="false" \
     NB_ENTRYPOINT_SERVICE_TIMEOUT="30"
 
 ENTRYPOINT [ "/usr/local/bin/netbird-entrypoint.sh" ]

client/Dockerfile-rootless

@@ -23,6 +23,7 @@ ENV \
     NB_DAEMON_ADDR="unix:///var/lib/netbird/netbird.sock" \
     NB_LOG_FILE="console,/var/lib/netbird/client.log" \
     NB_DISABLE_DNS="true" \
+    NB_ENABLE_CAPTURE="false" \
     NB_ENTRYPOINT_SERVICE_TIMEOUT="30"
 
 ENTRYPOINT [ "/usr/local/bin/netbird-entrypoint.sh" ]

client/cmd/capture.go

@@ -0,0 +1,196 @@
+package cmd
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"os"
+	"os/signal"
+	"path/filepath"
+	"strings"
+	"syscall"
+
+	"github.com/hashicorp/go-multierror"
+	"github.com/spf13/cobra"
+	"google.golang.org/grpc/status"
+	"google.golang.org/protobuf/types/known/durationpb"
+
+	nberrors "github.com/netbirdio/netbird/client/errors"
+	"github.com/netbirdio/netbird/client/proto"
+	"github.com/netbirdio/netbird/util/capture"
+)
+
+var captureCmd = &cobra.Command{
+	Use:   "capture",
+	Short: "Capture packets on the WireGuard interface",
+	Long: `Captures decrypted packets flowing through the WireGuard interface.
+
+Default output is human-readable text. Use --pcap or --output for pcap binary.
+Requires --enable-capture to be set at service install or reconfigure time.
+
+Examples:
+  netbird debug capture
+  netbird debug capture host 100.64.0.1 and port 443
+  netbird debug capture tcp
+  netbird debug capture icmp
+  netbird debug capture src host 10.0.0.1 and dst port 80
+  netbird debug capture -o capture.pcap
+  netbird debug capture --pcap | tshark -r -
+  netbird debug capture --pcap | tcpdump -r - -n`,
+	Args: cobra.ArbitraryArgs,
+	RunE: runCapture,
+}
+
+func init() {
+	debugCmd.AddCommand(captureCmd)
+
+	captureCmd.Flags().Bool("pcap", false, "Force pcap binary output (default when --output is set)")
+	captureCmd.Flags().BoolP("verbose", "v", false, "Show seq/ack, TTL, window, total length")
+	captureCmd.Flags().Bool("ascii", false, "Print payload as ASCII after each packet (useful for HTTP)")
+	captureCmd.Flags().Uint32("snap-len", 0, "Max bytes per packet (0 = full)")
+	captureCmd.Flags().DurationP("duration", "d", 0, "Capture duration (0 = until interrupted)")
+	captureCmd.Flags().StringP("output", "o", "", "Write pcap to file instead of stdout")
+}
+
+func runCapture(cmd *cobra.Command, args []string) error {
+	conn, err := getClient(cmd)
+	if err != nil {
+		return err
+	}
+	defer func() {
+		if err := conn.Close(); err != nil {
+			cmd.PrintErrf(errCloseConnection, err)
+		}
+	}()
+
+	client := proto.NewDaemonServiceClient(conn)
+
+	req, err := buildCaptureRequest(cmd, args)
+	if err != nil {
+		return err
+	}
+
+	ctx, cancel := signal.NotifyContext(cmd.Context(), syscall.SIGINT, syscall.SIGTERM)
+	defer cancel()
+
+	stream, err := client.StartCapture(ctx, req)
+	if err != nil {
+		return handleCaptureError(err)
+	}
+
+	// First Recv is the empty acceptance message from the server. If the
+	// device is unavailable (kernel WG, not connected, capture disabled),
+	// the server returns an error instead.
+	if _, err := stream.Recv(); err != nil {
+		return handleCaptureError(err)
+	}
+
+	out, cleanup, err := captureOutput(cmd)
+	if err != nil {
+		return err
+	}
+
+	if req.TextOutput {
+		cmd.PrintErrf("Capturing packets... Press Ctrl+C to stop.\n")
+	} else {
+		cmd.PrintErrf("Capturing packets (pcap)... Press Ctrl+C to stop.\n")
+	}
+
+	streamErr := streamCapture(ctx, cmd, stream, out)
+	cleanupErr := cleanup()
+	if streamErr != nil {
+		return streamErr
+	}
+	return cleanupErr
+}
+
+func buildCaptureRequest(cmd *cobra.Command, args []string) (*proto.StartCaptureRequest, error) {
+	req := &proto.StartCaptureRequest{}
+
+	if len(args) > 0 {
+		expr := strings.Join(args, " ")
+		if _, err := capture.ParseFilter(expr); err != nil {
+			return nil, fmt.Errorf("invalid filter: %w", err)
+		}
+		req.FilterExpr = expr
+	}
+
+	if snap, _ := cmd.Flags().GetUint32("snap-len"); snap > 0 {
+		req.SnapLen = snap
+	}
+	if d, _ := cmd.Flags().GetDuration("duration"); d != 0 {
+		if d < 0 {
+			return nil, fmt.Errorf("duration must not be negative")
+		}
+		req.Duration = durationpb.New(d)
+	}
+	req.Verbose, _ = cmd.Flags().GetBool("verbose")
+	req.Ascii, _ = cmd.Flags().GetBool("ascii")
+
+	outPath, _ := cmd.Flags().GetString("output")
+	forcePcap, _ := cmd.Flags().GetBool("pcap")
+	req.TextOutput = !forcePcap && outPath == ""
+
+	return req, nil
+}
+
+func streamCapture(ctx context.Context, cmd *cobra.Command, stream proto.DaemonService_StartCaptureClient, out io.Writer) error {
+	for {
+		pkt, err := stream.Recv()
+		if err != nil {
+			if ctx.Err() != nil {
+				cmd.PrintErrf("\nCapture stopped.\n")
+				return nil //nolint:nilerr // user interrupted
+			}
+			if err == io.EOF {
+				cmd.PrintErrf("\nCapture finished.\n")
+				return nil
+			}
+			return handleCaptureError(err)
+		}
+		if _, err := out.Write(pkt.GetData()); err != nil {
+			return fmt.Errorf("write output: %w", err)
+		}
+	}
+}
+
+// captureOutput returns the writer for capture data and a cleanup function
+// that finalizes the file. Errors from the cleanup must be propagated.
+func captureOutput(cmd *cobra.Command) (io.Writer, func() error, error) {
+	outPath, _ := cmd.Flags().GetString("output")
+	if outPath == "" {
+		return os.Stdout, func() error { return nil }, nil
+	}
+
+	f, err := os.CreateTemp(filepath.Dir(outPath), filepath.Base(outPath)+".*.tmp")
+	if err != nil {
+		return nil, nil, fmt.Errorf("create output file: %w", err)
+	}
+	tmpPath := f.Name()
+	return f, func() error {
+		var merr *multierror.Error
+		if err := f.Close(); err != nil {
+			merr = multierror.Append(merr, fmt.Errorf("close output file: %w", err))
+		}
+		fi, statErr := os.Stat(tmpPath)
+		if statErr != nil || fi.Size() == 0 {
+			if rmErr := os.Remove(tmpPath); rmErr != nil && !os.IsNotExist(rmErr) {
+				merr = multierror.Append(merr, fmt.Errorf("remove empty output file: %w", rmErr))
+			}
+			return nberrors.FormatErrorOrNil(merr)
+		}
+		if err := os.Rename(tmpPath, outPath); err != nil {
+			merr = multierror.Append(merr, fmt.Errorf("rename output file: %w", err))
+			return nberrors.FormatErrorOrNil(merr)
+		}
+		cmd.PrintErrf("Wrote %s\n", outPath)
+		return nberrors.FormatErrorOrNil(merr)
+	}, nil
+}
+
+func handleCaptureError(err error) error {
+	if s, ok := status.FromError(err); ok {
+		return fmt.Errorf("%s", s.Message())
+	}
+	return err
+}

client/cmd/debug.go

@@ -9,6 +9,7 @@ import (
 	log "github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
 	"google.golang.org/grpc/status"
+	"google.golang.org/protobuf/types/known/durationpb"
 
 	"github.com/netbirdio/netbird/client/internal"
 	"github.com/netbirdio/netbird/client/internal/debug"
@@ -239,11 +240,50 @@ func runForDuration(cmd *cobra.Command, args []string) error {
 		}()
 	}
 
+	captureStarted := false
+	if wantCapture, _ := cmd.Flags().GetBool("capture"); wantCapture {
+		captureTimeout := duration + 30*time.Second
+		const maxBundleCapture = 10 * time.Minute
+		if captureTimeout > maxBundleCapture {
+			captureTimeout = maxBundleCapture
+		}
+		_, err := client.StartBundleCapture(cmd.Context(), &proto.StartBundleCaptureRequest{
+			Timeout: durationpb.New(captureTimeout),
+		})
+		if err != nil {
+			cmd.PrintErrf("Failed to start packet capture: %v\n", status.Convert(err).Message())
+		} else {
+			captureStarted = true
+			cmd.Println("Packet capture started.")
+			// Safety: always stop on exit, even if the normal stop below runs too.
+			defer func() {
+				if captureStarted {
+					stopCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+					defer cancel()
+					if _, err := client.StopBundleCapture(stopCtx, &proto.StopBundleCaptureRequest{}); err != nil {
+						cmd.PrintErrf("Failed to stop packet capture: %v\n", err)
+					}
+				}
+			}()
+		}
+	}
+
 	if waitErr := waitForDurationOrCancel(cmd.Context(), duration, cmd); waitErr != nil {
 		return waitErr
 	}
 	cmd.Println("\nDuration completed")
 
+	if captureStarted {
+		stopCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+		defer cancel()
+		if _, err := client.StopBundleCapture(stopCtx, &proto.StopBundleCaptureRequest{}); err != nil {
+			cmd.PrintErrf("Failed to stop packet capture: %v\n", err)
+		} else {
+			captureStarted = false
+			cmd.Println("Packet capture stopped.")
+		}
+	}
+
 	if cpuProfilingStarted {
 		if _, err := client.StopCPUProfile(cmd.Context(), &proto.StopCPUProfileRequest{}); err != nil {
 			cmd.PrintErrf("Failed to stop CPU profiling: %v\n", err)
@@ -416,4 +456,5 @@ func init() {
 	forCmd.Flags().BoolVarP(&systemInfoFlag, "system-info", "S", true, "Adds system information to the debug bundle")
 	forCmd.Flags().BoolVarP(&uploadBundleFlag, "upload-bundle", "U", false, "Uploads the debug bundle to a server")
 	forCmd.Flags().StringVar(&uploadBundleURLFlag, "upload-bundle-url", types.DefaultBundleURL, "Service URL to get an URL to upload the debug bundle")
+	forCmd.Flags().Bool("capture", false, "Capture packets during the debug duration and include in bundle")
 }

client/cmd/root.go

@@ -75,6 +75,7 @@ var (
 	mtu                     uint16
 	profilesDisabled        bool
 	updateSettingsDisabled  bool
+	captureEnabled          bool
 	networksDisabled        bool
 
 	rootCmd = &cobra.Command{

client/cmd/service.go

@@ -44,6 +44,7 @@ func init() {
 	serviceCmd.AddCommand(runCmd, startCmd, stopCmd, restartCmd, svcStatusCmd, installCmd, uninstallCmd, reconfigureCmd, resetParamsCmd)
 	serviceCmd.PersistentFlags().BoolVar(&profilesDisabled, "disable-profiles", false, "Disables profiles feature. If enabled, the client will not be able to change or edit any profile. To persist this setting, use: netbird service install --disable-profiles")
 	serviceCmd.PersistentFlags().BoolVar(&updateSettingsDisabled, "disable-update-settings", false, "Disables update settings feature. If enabled, the client will not be able to change or edit any settings. To persist this setting, use: netbird service install --disable-update-settings")
+	serviceCmd.PersistentFlags().BoolVar(&captureEnabled, "enable-capture", false, "Enables packet capture via 'netbird debug capture'. To persist, use: netbird service install --enable-capture")
 	serviceCmd.PersistentFlags().BoolVar(&networksDisabled, "disable-networks", false, "Disables network selection. If enabled, the client will not allow listing, selecting, or deselecting networks. To persist, use: netbird service install --disable-networks")
 
 	rootCmd.PersistentFlags().StringVarP(&serviceName, "service", "s", defaultServiceName, "Netbird system service name")

client/cmd/service_controller.go

@@ -61,7 +61,7 @@ func (p *program) Start(svc service.Service) error {
 			}
 		}
 
-		serverInstance := server.New(p.ctx, util.FindFirstLogPath(logFiles), configPath, profilesDisabled, updateSettingsDisabled, networksDisabled)
+		serverInstance := server.New(p.ctx, util.FindFirstLogPath(logFiles), configPath, profilesDisabled, updateSettingsDisabled, captureEnabled, networksDisabled)
 		if err := serverInstance.Start(); err != nil {
 			log.Fatalf("failed to start daemon: %v", err)
 		}

client/cmd/service_installer.go

@@ -59,6 +59,10 @@ func buildServiceArguments() []string {
 		args = append(args, "--disable-update-settings")
 	}
 
+	if captureEnabled {
+		args = append(args, "--enable-capture")
+	}
+
 	if networksDisabled {
 		args = append(args, "--disable-networks")
 	}

client/cmd/service_params.go

@@ -28,6 +28,7 @@ type serviceParams struct {
 	LogFiles              []string          `json:"log_files,omitempty"`
 	DisableProfiles       bool              `json:"disable_profiles,omitempty"`
 	DisableUpdateSettings bool              `json:"disable_update_settings,omitempty"`
+	EnableCapture         bool              `json:"enable_capture,omitempty"`
 	DisableNetworks       bool              `json:"disable_networks,omitempty"`
 	ServiceEnvVars        map[string]string `json:"service_env_vars,omitempty"`
 }
@@ -79,6 +80,7 @@ func currentServiceParams() *serviceParams {
 		LogFiles:              logFiles,
 		DisableProfiles:       profilesDisabled,
 		DisableUpdateSettings: updateSettingsDisabled,
+		EnableCapture:         captureEnabled,
 		DisableNetworks:       networksDisabled,
 	}
 
@@ -144,6 +146,10 @@ func applyServiceParams(cmd *cobra.Command, params *serviceParams) {
 		updateSettingsDisabled = params.DisableUpdateSettings
 	}
 
+	if !serviceCmd.PersistentFlags().Changed("enable-capture") {
+		captureEnabled = params.EnableCapture
+	}
+
 	if !serviceCmd.PersistentFlags().Changed("disable-networks") {
 		networksDisabled = params.DisableNetworks
 	}

client/cmd/service_params_test.go

@@ -535,6 +535,7 @@ func fieldToGlobalVar(field string) string {
 		"LogFiles":              "logFiles",
 		"DisableProfiles":       "profilesDisabled",
 		"DisableUpdateSettings": "updateSettingsDisabled",
+		"EnableCapture":         "captureEnabled",
 		"DisableNetworks":       "networksDisabled",
 		"ServiceEnvVars":        "serviceEnvVars",
 	}

client/cmd/testutil_test.go

@@ -160,7 +160,7 @@ func startClientDaemon(
 	s := grpc.NewServer()
 
 	server := client.New(ctx,
-		"", "", false, false, false)
+		"", "", false, false, false, false)
 	if err := server.Start(); err != nil {
 		t.Fatal(err)
 	}