Refactor embed capture API to StartCapture/StopCapture

client/embed/capture.go

@@ -0,0 +1,65 @@
+package embed
+
+import (
+	"io"
+
+	"github.com/netbirdio/netbird/client/internal"
+	"github.com/netbirdio/netbird/util/capture"
+)
+
+// CaptureOptions configures a packet capture session.
+type CaptureOptions struct {
+	// Output receives pcap-formatted data. Nil disables pcap output.
+	Output io.Writer
+	// TextOutput receives human-readable packet summaries. Nil disables text output.
+	TextOutput io.Writer
+	// Filter is a BPF-like filter expression (e.g. "host 10.0.0.1 and tcp port 443").
+	// Empty captures all packets.
+	Filter string
+	// Verbose adds seq/ack, TTL, window, and total length to text output.
+	Verbose bool
+	// ASCII dumps transport payload as printable ASCII after each packet line.
+	ASCII bool
+}
+
+// CaptureStats reports capture session counters.
+type CaptureStats struct {
+	Packets int64
+	Bytes   int64
+	Dropped int64
+}
+
+// CaptureSession represents an active packet capture. Call Stop to end the
+// capture and flush buffered packets.
+type CaptureSession struct {
+	sess   *capture.Session
+	engine *internal.Engine
+}
+
+// Stop ends the capture, flushes remaining packets, and detaches from the device.
+// Safe to call multiple times.
+func (cs *CaptureSession) Stop() {
+	if cs.engine != nil {
+		_ = cs.engine.SetCapture(nil)
+		cs.engine = nil
+	}
+	if cs.sess != nil {
+		cs.sess.Stop()
+	}
+}
+
+// Stats returns current capture counters.
+func (cs *CaptureSession) Stats() CaptureStats {
+	s := cs.sess.Stats()
+	return CaptureStats{
+		Packets: s.Packets,
+		Bytes:   s.Bytes,
+		Dropped: s.Dropped,
+	}
+}
+
+// Done returns a channel that is closed when the capture's writer goroutine
+// has fully exited and all buffered packets have been flushed.
+func (cs *CaptureSession) Done() <-chan struct{} {
+	return cs.sess.Done()
+}

client/embed/embed.go

@@ -66,7 +66,7 @@ type Options struct {
 	PrivateKey string
 	// ManagementURL overrides the default management server URL
 	ManagementURL string
-	// PreSharedKey is the pre-shared key for the WireGuard interface
+	// PreSharedKey is the pre-shared key for the tunnel interface
 	PreSharedKey string
 	// LogOutput is the output destination for logs (defaults to os.Stderr if nil)
 	LogOutput io.Writer
@@ -82,9 +82,9 @@ type Options struct {
 	DisableClientRoutes bool
 	// BlockInbound blocks all inbound connections from peers
 	BlockInbound bool
-	// WireguardPort is the port for the WireGuard interface. Use 0 for a random port.
+	// WireguardPort is the port for the tunnel interface. Use 0 for a random port.
 	WireguardPort *int
-	// MTU is the MTU for the WireGuard interface.
+	// MTU is the MTU for the tunnel interface.
 	// Valid values are in the range 576..8192 bytes.
 	// If non-nil, this value overrides any value stored in the config file.
 	// If nil, the existing config MTU (if non-zero) is preserved; otherwise it defaults to 1280.
@@ -470,6 +470,52 @@ func (c *Client) VerifySSHHostKey(peerAddress string, key []byte) error {
 	return sshcommon.VerifyHostKey(storedKey, key, peerAddress)
 }
 
+// StartCapture begins capturing packets on this client's tunnel device.
+// Only one capture can be active at a time; starting a new one stops the previous.
+// Call StopCapture (or CaptureSession.Stop) to end it.
+func (c *Client) StartCapture(opts CaptureOptions) (*CaptureSession, error) {
+	engine, err := c.getEngine()
+	if err != nil {
+		return nil, err
+	}
+
+	var matcher capture.Matcher
+	if opts.Filter != "" {
+		m, err := capture.ParseFilter(opts.Filter)
+		if err != nil {
+			return nil, fmt.Errorf("parse filter: %w", err)
+		}
+		matcher = m
+	}
+
+	sess, err := capture.NewSession(capture.Options{
+		Output:     opts.Output,
+		TextOutput: opts.TextOutput,
+		Matcher:    matcher,
+		Verbose:    opts.Verbose,
+		ASCII:      opts.ASCII,
+	})
+	if err != nil {
+		return nil, fmt.Errorf("create capture session: %w", err)
+	}
+
+	if err := engine.SetCapture(sess); err != nil {
+		sess.Stop()
+		return nil, fmt.Errorf("set capture: %w", err)
+	}
+
+	return &CaptureSession{sess: sess, engine: engine}, nil
+}
+
+// StopCapture stops the active capture session if one is running.
+func (c *Client) StopCapture() error {
+	engine, err := c.getEngine()
+	if err != nil {
+		return err
+	}
+	return engine.SetCapture(nil)
+}
+
 // getEngine safely retrieves the engine from the client with proper locking.
 // Returns ErrClientNotStarted if the client is not started.
 // Returns ErrEngineNotStarted if the engine is not available.
@@ -490,22 +536,6 @@ func (c *Client) getEngine() (*internal.Engine, error) {
 	return engine, nil
 }
 
-// SetCapture sets or clears packet capture on this client's WireGuard device.
-// Pass nil to disable capture.
-func (c *Client) SetCapture(sess *capture.Session) error {
-	engine, err := c.getEngine()
-	if err != nil {
-		return err
-	}
-	// Explicit nil check to avoid wrapping a nil *Session in the
-	// device.PacketCapture interface, which would appear non-nil to
-	// FilteredDevice and cause a nil-pointer dereference in Offer.
-	if sess == nil {
-		return engine.SetCapture(nil)
-	}
-	return engine.SetCapture(sess)
-}
-
 func (c *Client) getNet() (*wgnetstack.Net, netip.Addr, error) {
 	engine, err := c.getEngine()
 	if err != nil {