netbird/client/server/capture.go

package server

import (
	"context"
	"io"
	"os"
	"sync"
	"time"

	log "github.com/sirupsen/logrus"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"

	"github.com/netbirdio/netbird/client/internal"
	"github.com/netbirdio/netbird/client/proto"
	"github.com/netbirdio/netbird/util/capture"
)

const maxBundleCaptureDuration = 10 * time.Minute

// bundleCapture holds the state of an in-progress capture destined for the
// debug bundle. The lifecycle is:
//
//	StartBundleCapture → capture running, writing to temp file
//	StopBundleCapture  → capture stopped, temp file available
//	DebugBundle        → temp file included in zip, then cleaned up
type bundleCapture struct {
	mu      sync.Mutex
	sess    *capture.Session
	file    *os.File
	engine  *internal.Engine
	cancel  context.CancelFunc
	stopped bool
}

// stop halts the capture session and closes the pcap writer. Idempotent.
func (bc *bundleCapture) stop() {
	bc.mu.Lock()
	defer bc.mu.Unlock()

	if bc.stopped {
		return
	}
	bc.stopped = true

	if bc.cancel != nil {
		bc.cancel()
	}
	if bc.engine != nil {
		if err := bc.engine.SetCapture(nil); err != nil {
			log.Debugf("clear bundle capture: %v", err)
		}
	}
	if bc.sess != nil {
		bc.sess.Stop()
	}
}

// path returns the temp file path, or "" if no file exists.
func (bc *bundleCapture) path() string {
	if bc.file == nil {
		return ""
	}
	return bc.file.Name()
}

// cleanup removes the temp file.
func (bc *bundleCapture) cleanup() {
	if bc.file == nil {
		return
	}
	name := bc.file.Name()
	if err := bc.file.Close(); err != nil {
		log.Debugf("close bundle capture file: %v", err)
	}
	if err := os.Remove(name); err != nil && !os.IsNotExist(err) {
		log.Debugf("remove bundle capture file: %v", err)
	}
	bc.file = nil
}

// StartCapture streams a pcap or text packet capture over gRPC.
// Gated by the --enable-capture service flag.
func (s *Server) StartCapture(req *proto.StartCaptureRequest, stream proto.DaemonService_StartCaptureServer) error {
	if !s.captureEnabled {
		return status.Error(codes.PermissionDenied,
			"packet capture is disabled; reinstall or reconfigure the service with --enable-capture")
	}

	engine, err := s.getCaptureEngine()
	if err != nil {
		return err
	}

	matcher, err := parseCaptureFilter(req)
	if err != nil {
		return status.Errorf(codes.InvalidArgument, "invalid filter: %v", err)
	}

	pr, pw := io.Pipe()

	opts := capture.Options{
		Matcher: matcher,
		SnapLen: req.GetSnapLen(),
		Verbose: req.GetVerbose(),
		ASCII:   req.GetAscii(),
	}
	if req.GetTextOutput() {
		opts.TextOutput = pw
	} else {
		opts.Output = pw
	}

	sess, err := capture.NewSession(opts)
	if err != nil {
		pw.Close()
		return status.Errorf(codes.Internal, "create capture session: %v", err)
	}

	if err := engine.SetCapture(sess); err != nil {
		sess.Stop()
		pw.Close()
		return status.Errorf(codes.Internal, "set capture: %v", err)
	}

	// Send an empty initial message to signal that the capture was accepted.
	// The client waits for this before printing the banner, so it must arrive
	// before any packet data.
	if err := stream.Send(&proto.CapturePacket{}); err != nil {
		if clearErr := engine.SetCapture(nil); clearErr != nil {
			log.Debugf("clear capture after send failure: %v", clearErr)
		}
		sess.Stop()
		pw.Close()
		return status.Errorf(codes.Internal, "send initial message: %v", err)
	}

	ctx := stream.Context()
	if d := req.GetDuration(); d != nil {
		dur := d.AsDuration()
		if dur < 0 {
			if clearErr := engine.SetCapture(nil); clearErr != nil {
				log.Debugf("clear capture: %v", clearErr)
			}
			sess.Stop()
			pw.Close()
			return status.Errorf(codes.InvalidArgument, "duration must not be negative")
		}
		if dur > 0 {
			var cancel context.CancelFunc
			ctx, cancel = context.WithTimeout(ctx, dur)
			defer cancel()
		}
	}

	go func() {
		<-ctx.Done()
		if err := engine.SetCapture(nil); err != nil {
			log.Debugf("clear capture: %v", err)
		}
		sess.Stop()
		pw.Close()
	}()
	defer pr.Close()

	log.Infof("packet capture started (text=%v, expr=%q)", req.GetTextOutput(), req.GetFilterExpr())
	defer func() {
		stats := sess.Stats()
		log.Infof("packet capture stopped: %d packets, %d bytes, %d dropped",
			stats.Packets, stats.Bytes, stats.Dropped)
	}()

	return streamToGRPC(pr, stream)
}

func streamToGRPC(r io.Reader, stream proto.DaemonService_StartCaptureServer) error {
	buf := make([]byte, 32*1024)
	for {
		n, readErr := r.Read(buf)
		if n > 0 {
			if err := stream.Send(&proto.CapturePacket{Data: buf[:n]}); err != nil {
				log.Debugf("capture stream send: %v", err)
				return nil //nolint:nilerr // client disconnected
			}
		}
		if readErr != nil {
			return nil //nolint:nilerr // pipe closed, capture stopped normally
		}
	}
}

// StartBundleCapture begins capturing packets to a server-side temp file for
// inclusion in the next debug bundle. Not gated by --enable-capture since the
// output stays on the server (same trust level as CPU profiling).
//
// A timeout auto-stops the capture as a safety net if StopBundleCapture is
// never called (e.g. CLI crash).
func (s *Server) StartBundleCapture(_ context.Context, req *proto.StartBundleCaptureRequest) (*proto.StartBundleCaptureResponse, error) {
	s.mutex.Lock()
	defer s.mutex.Unlock()

	s.stopBundleCaptureLocked()
	s.cleanupBundleCapture()

	engine, err := s.getCaptureEngineLocked()
	if err != nil {
		// Not fatal: kernel mode or not connected. Log and return success
		// so the debug bundle still generates without capture data.
		log.Warnf("packet capture unavailable, skipping: %v", err)
		return &proto.StartBundleCaptureResponse{}, nil
	}

	timeout := req.GetTimeout().AsDuration()
	if timeout <= 0 || timeout > maxBundleCaptureDuration {
		timeout = maxBundleCaptureDuration
	}

	f, err := os.CreateTemp("", "netbird.capture.*.pcap")
	if err != nil {
		return nil, status.Errorf(codes.Internal, "create temp file: %v", err)
	}

	sess, err := capture.NewSession(capture.Options{Output: f})
	if err != nil {
		f.Close()
		os.Remove(f.Name())
		return nil, status.Errorf(codes.Internal, "create capture session: %v", err)
	}

	if err := engine.SetCapture(sess); err != nil {
		sess.Stop()
		f.Close()
		os.Remove(f.Name())
		log.Warnf("packet capture unavailable (no filtered device), skipping: %v", err)
		return &proto.StartBundleCaptureResponse{}, nil
	}

	ctx, cancel := context.WithTimeout(context.Background(), timeout)
	bc := &bundleCapture{
		sess:   sess,
		file:   f,
		engine: engine,
		cancel: cancel,
	}

	go func() {
		<-ctx.Done()
		bc.stop()
		log.Infof("bundle capture auto-stopped after timeout")
	}()

	s.bundleCapture = bc
	log.Infof("bundle capture started (timeout=%s, file=%s)", timeout, f.Name())

	return &proto.StartBundleCaptureResponse{}, nil
}

// StopBundleCapture stops the running bundle capture. Idempotent.
func (s *Server) StopBundleCapture(_ context.Context, _ *proto.StopBundleCaptureRequest) (*proto.StopBundleCaptureResponse, error) {
	s.mutex.Lock()
	defer s.mutex.Unlock()

	s.stopBundleCaptureLocked()
	return &proto.StopBundleCaptureResponse{}, nil
}

// stopBundleCaptureLocked stops the bundle capture if running. Must hold s.mutex.
func (s *Server) stopBundleCaptureLocked() {
	if s.bundleCapture == nil {
		return
	}
	s.bundleCapture.stop()

	stats := s.bundleCapture.sess.Stats()
	log.Infof("bundle capture stopped: %d packets, %d bytes, %d dropped",
		stats.Packets, stats.Bytes, stats.Dropped)
}

// bundleCapturePath returns the temp file path if a capture has been taken,
// stops any running capture, and returns "". Called from DebugBundle.
// Must hold s.mutex.
func (s *Server) bundleCapturePath() string {
	if s.bundleCapture == nil {
		return ""
	}

	s.bundleCapture.stop()
	return s.bundleCapture.path()
}

// cleanupBundleCapture removes the temp file and clears state. Must hold s.mutex.
func (s *Server) cleanupBundleCapture() {
	if s.bundleCapture == nil {
		return
	}
	s.bundleCapture.cleanup()
	s.bundleCapture = nil
}

func (s *Server) getCaptureEngine() (*internal.Engine, error) {
	s.mutex.Lock()
	defer s.mutex.Unlock()
	return s.getCaptureEngineLocked()
}

func (s *Server) getCaptureEngineLocked() (*internal.Engine, error) {
	if s.connectClient == nil {
		return nil, status.Error(codes.FailedPrecondition, "client not connected")
	}
	engine := s.connectClient.Engine()
	if engine == nil {
		return nil, status.Error(codes.FailedPrecondition, "engine not initialized")
	}
	return engine, nil
}

// parseCaptureFilter returns a Matcher from the request.
// Returns nil (match all) when no filter expression is set.
func parseCaptureFilter(req *proto.StartCaptureRequest) (capture.Matcher, error) {
	expr := req.GetFilterExpr()
	if expr == "" {
		return nil, nil //nolint:nilnil // nil Matcher means "match all"
	}
	return capture.ParseFilter(expr)
}