feat: add support for pcap replay

.github/workflows/check.yaml

@@ -23,6 +23,9 @@ jobs:
         with:
           go-version: 'stable'
 
+      - name: Install pcap
+        run: sudo apt install -y libpcap-dev
+
       - run: go vet ./...
 
       - name: staticcheck
@@ -44,4 +47,7 @@ jobs:
         with:
           go-version: 'stable'
 
+      - name: Install pcap
+        run: sudo apt install -y libpcap-dev
+
       - run: go test ./...

.github/workflows/release.yaml

@@ -24,6 +24,9 @@ jobs:
         with:
           go-version: "1.22"
 
+      - name: Install pcap
+        run: sudo apt install -y libpcap-dev
+
       - name: Build
         env:
           GOOS: ${{ matrix.goos }}

cmd/root.go

@@ -43,6 +43,7 @@ var logger *zap.Logger
 // Flags
 var (
 	cfgFile   string
+	pcapFile  string
 	logLevel  string
 	logFormat string
 )
@@ -118,6 +119,7 @@ func init() {
 
 func initFlags() {
 	rootCmd.PersistentFlags().StringVarP(&cfgFile, "config", "c", "", "config file")
+	rootCmd.PersistentFlags().StringVarP(&pcapFile, "pcap", "p", "", "pcap file (optional)")
 	rootCmd.PersistentFlags().StringVarP(&logLevel, "log-level", "l", envOrDefaultString(appLogLevelEnv, "info"), "log level")
 	rootCmd.PersistentFlags().StringVarP(&logFormat, "log-format", "f", envOrDefaultString(appLogFormatEnv, "console"), "log format")
 }
@@ -167,6 +169,7 @@ type cliConfig struct {
 	IO      cliConfigIO      `mapstructure:"io"`
 	Workers cliConfigWorkers `mapstructure:"workers"`
 	Ruleset cliConfigRuleset `mapstructure:"ruleset"`
+	Replay  cliConfigReplay  `mapstructure:"replay"`
 }
 
 type cliConfigIO struct {
@@ -177,6 +180,10 @@ type cliConfigIO struct {
 	RST         bool   `mapstructure:"rst"`
 }
 
+type cliConfigReplay struct {
+	Realtime bool `mapstructure:"realtime"`
+}
+
 type cliConfigWorkers struct {
 	Count                      int           `mapstructure:"count"`
 	QueueSize                  int           `mapstructure:"queueSize"`
@@ -197,17 +204,30 @@ func (c *cliConfig) fillLogger(config *engine.Config) error {
 }
 
 func (c *cliConfig) fillIO(config *engine.Config) error {
-	nfio, err := io.NewNFQueuePacketIO(io.NFQueuePacketIOConfig{
-		QueueSize:   c.IO.QueueSize,
-		ReadBuffer:  c.IO.ReadBuffer,
-		WriteBuffer: c.IO.WriteBuffer,
-		Local:       c.IO.Local,
-		RST:         c.IO.RST,
-	})
+	var ioImpl io.PacketIO
+	var err error
+	if pcapFile != "" {
+		// Setup IO for pcap file replay
+		logger.Info("replaying from pcap file", zap.String("pcap file", pcapFile))
+		ioImpl, err = io.NewPcapPacketIO(io.PcapPacketIOConfig{
+			PcapFile: pcapFile,
+			Realtime: c.Replay.Realtime,
+		})
+	} else {
+		// Setup IO for nfqueue
+		ioImpl, err = io.NewNFQueuePacketIO(io.NFQueuePacketIOConfig{
+			QueueSize:   c.IO.QueueSize,
+			ReadBuffer:  c.IO.ReadBuffer,
+			WriteBuffer: c.IO.WriteBuffer,
+			Local:       c.IO.Local,
+			RST:         c.IO.RST,
+		})
+	}
+
 	if err != nil {
 		return configError{Field: "io", Err: err}
 	}
-	config.IO = nfio
+	config.IO = ioImpl
 	return nil
 }
 

engine/engine.go

@@ -58,12 +58,17 @@ func (e *engine) UpdateRuleset(r ruleset.Ruleset) error {
 }
 
 func (e *engine) Run(ctx context.Context) error {
+	workerCtx, workerCancel := context.WithCancel(ctx)
+	defer workerCancel() // Stop workers
+
+	// Register IO shutdown
 	ioCtx, ioCancel := context.WithCancel(ctx)
-	defer ioCancel() // Stop workers & IO
+	e.io.SetCancelFunc(ioCancel)
+	defer ioCancel() // Stop IO
 
 	// Start workers
 	for _, w := range e.workers {
-		go w.Run(ioCtx)
+		go w.Run(workerCtx)
 	}
 
 	// Register IO callback
@@ -85,6 +90,8 @@ func (e *engine) Run(ctx context.Context) error {
 		return err
 	case <-ctx.Done():
 		return nil
+	case <-ioCtx.Done():
+		return nil
 	}
 }
 

io/interface.go

@@ -48,6 +48,9 @@ type PacketIO interface {
 	ProtectedDialContext(ctx context.Context, network, address string) (net.Conn, error)
 	// Close closes the packet IO.
 	Close() error
+	// SetCancelFunc gives packet IO access to context cancel function, enabling it to
+	// trigger a shutdown
+	SetCancelFunc(cancelFunc context.CancelFunc) error
 }
 
 type ErrInvalidPacket struct {

io/nfqueue.go

@@ -281,6 +281,11 @@ func (n *nfqueuePacketIO) Close() error {
 	return n.n.Close()
 }
 
+// nfqueue IO does not issue shutdown
+func (n *nfqueuePacketIO) SetCancelFunc(cancelFunc context.CancelFunc) error {
+	return nil
+}
+
 func (n *nfqueuePacketIO) setupNft(local, rst, remove bool) error {
 	rules, err := generateNftRules(local, rst)
 	if err != nil {

io/pcap.go

@@ -0,0 +1,130 @@
+package io
+
+import (
+	"context"
+	"hash/crc32"
+	"net"
+	"sort"
+	"strings"
+	"time"
+
+	"github.com/google/gopacket"
+	"github.com/google/gopacket/pcap"
+)
+
+var _ PacketIO = (*pcapPacketIO)(nil)
+
+type pcapPacketIO struct {
+	pcap     *pcap.Handle
+	lastTime *time.Time
+	ioCancel context.CancelFunc
+	config   PcapPacketIOConfig
+
+	dialer *net.Dialer
+}
+
+type PcapPacketIOConfig struct {
+	PcapFile string
+	Realtime bool
+}
+
+func NewPcapPacketIO(config PcapPacketIOConfig) (PacketIO, error) {
+	handle, err := pcap.OpenOffline(config.PcapFile)
+	if err != nil {
+		return nil, err
+	}
+
+	return &pcapPacketIO{
+		pcap:     handle,
+		lastTime: nil,
+		ioCancel: nil,
+		config:   config,
+		dialer:   &net.Dialer{},
+	}, nil
+}
+
+func (p *pcapPacketIO) Register(ctx context.Context, cb PacketCallback) error {
+	go func() {
+		packetSource := gopacket.NewPacketSource(p.pcap, p.pcap.LinkType())
+		for packet := range packetSource.Packets() {
+			p.wait(packet)
+
+			networkLayer := packet.NetworkLayer()
+			if networkLayer != nil {
+				src, dst := networkLayer.NetworkFlow().Endpoints()
+				endpoints := []string{src.String(), dst.String()}
+				sort.Strings(endpoints)
+				id := crc32.Checksum([]byte(strings.Join(endpoints, ",")), crc32.IEEETable)
+
+				cb(&pcapPacket{
+					streamID:  id,
+					timestamp: packet.Metadata().Timestamp,
+					data:      packet.LinkLayer().LayerPayload(),
+				}, nil)
+			}
+		}
+		// Give the workers a chance to finish everything
+		time.Sleep(time.Second)
+		// Stop the engine when all packets are finished
+		p.ioCancel()
+	}()
+
+	return nil
+}
+
+// A normal dialer is sufficient as pcap IO does not mess up with the networking
+func (p *pcapPacketIO) ProtectedDialContext(ctx context.Context, network, address string) (net.Conn, error) {
+	return p.dialer.DialContext(ctx, network, address)
+}
+
+func (p *pcapPacketIO) SetVerdict(pkt Packet, v Verdict, newPacket []byte) error {
+	return nil
+}
+
+func (p *pcapPacketIO) SetCancelFunc(cancelFunc context.CancelFunc) error {
+	p.ioCancel = cancelFunc
+	return nil
+}
+
+func (p *pcapPacketIO) Close() error {
+	p.pcap.Close()
+	return nil
+}
+
+// Intentionally slow down the replay
+// In realtime mode, this is to match the timestamps in the capture
+func (p *pcapPacketIO) wait(packet gopacket.Packet) error {
+	if !p.config.Realtime {
+		return nil
+	}
+
+	if p.lastTime == nil {
+		p.lastTime = &packet.Metadata().Timestamp
+	} else {
+		t := packet.Metadata().Timestamp.Sub(*p.lastTime)
+		time.Sleep(t)
+		p.lastTime = &packet.Metadata().Timestamp
+	}
+
+	return nil
+}
+
+var _ Packet = (*pcapPacket)(nil)
+
+type pcapPacket struct {
+	streamID  uint32
+	timestamp time.Time
+	data      []byte
+}
+
+func (p *pcapPacket) StreamID() uint32 {
+	return p.streamID
+}
+
+func (p *pcapPacket) Timestamp() time.Time {
+	return p.timestamp
+}
+
+func (p *pcapPacket) Data() []byte {
+	return p.data
+}