feat: real time packet trace

Author: encodeous

cmd/inspect.go

@@ -16,17 +16,28 @@ var inspectCmd = &cobra.Command{
 			fmt.Println("Usage: nylon inspect <interface>")
 			return
 		}
-		itf := args[0]
-		result, err := core.IPCGet(itf)
-		if err != nil {
-			fmt.Println("Error:", err.Error())
-			return
+		if ok, _ := cmd.Flags().GetBool("trace"); ok {
+			itf := args[0]
+			err := core.IPCTrace(itf)
+			if err != nil {
+				fmt.Println("Error:", err.Error())
+				return
+			}
+		} else {
+			itf := args[0]
+			result, err := core.IPCGet(itf)
+			if err != nil {
+				fmt.Println("Error:", err.Error())
+				return
+			}
+			fmt.Print(result)
 		}
-		fmt.Print(result)
 	},
 	GroupID: "ny",
 }
 
 func init() {
 	rootCmd.AddCommand(inspectCmd)
+
+	inspectCmd.Flags().BoolP("trace", "t", false, "Enables live packet routing capture")
 }

core/entrypoint.go

@@ -234,6 +234,7 @@ func Start(ccfg state.CentralCfg, ncfg state.LocalCfg, logLevel slog.Level, conf
 
 func initModules(s *state.State) error {
 	var modules []state.NyModule
+	modules = append(modules, &NylonTrace{})
 	modules = append(modules, &NylonRouter{})
 	modules = append(modules, &Nylon{})
 

core/ipc.go

@@ -2,6 +2,7 @@ package core
 
 import (
 	"bufio"
+	"context"
 	"fmt"
 	"io"
 	"slices"
@@ -41,6 +42,37 @@ func IPCGet(itf string) (string, error) {
 	return strings.TrimSuffix(res, "\x00"), nil
 }
 
+func IPCTrace(itf string) error {
+	conn, err := ipc.UAPIDial(itf)
+	if err != nil {
+		return err
+	}
+	defer conn.Close()
+	rw := bufio.NewReadWriter(bufio.NewReader(conn), bufio.NewWriter(conn))
+
+	_, err = rw.WriteString("get=nylon\n")
+	if err != nil {
+		return err
+	}
+
+	_, err = rw.WriteString("trace\n")
+	if err != nil {
+		return err
+	}
+	err = rw.Flush()
+	if err != nil {
+		return err
+	}
+
+	for {
+		str, err := rw.ReadString('\n')
+		if err != nil {
+			return err
+		}
+		fmt.Print(str)
+	}
+}
+
 func HandleNylonIPCGet(s *state.State, rw *bufio.ReadWriter) error {
 	cmd, err := rw.ReadString('\n')
 	if err != nil {
@@ -139,6 +171,36 @@ func HandleNylonIPCGet(s *state.State, rw *bufio.ReadWriter) error {
 			return err
 		}
 		return rw.Flush()
+	case "trace\n":
+		if !state.DBG_trace_tc {
+			return fmt.Errorf("trace mode is not enabled")
+		}
+		ctx, cancel := context.WithCancel(context.Background())
+		t := Get[*NylonTrace](s)
+		go func() {
+			_, _ = rw.ReadByte() // wait for EOF
+			cancel()
+		}()
+		ch := make(chan interface{})
+		t.Register(ch)
+		defer t.Unregister(ch)
+		for {
+			select {
+			case <-ctx.Done():
+				return nil
+			case msg := <-ch:
+				if str, ok := msg.(string); ok {
+					_, err := rw.WriteString(str)
+					if err != nil {
+						return err
+					}
+					err = rw.Flush()
+					if err != nil {
+						return err
+					}
+				}
+			}
+		}
 	default:
 		return fmt.Errorf("unknown command %s", cmd)
 	}

core/nylon_tc.go

@@ -1,6 +1,7 @@
 package core
 
 import (
+	"fmt"
 	"net/netip"
 
 	"github.com/encodeous/nylon/polyamide/conn"
@@ -18,6 +19,7 @@ const (
 
 func (n *Nylon) InstallTC(s *state.State) {
 	r := Get[*NylonRouter](s)
+	t := Get[*NylonTrace](s)
 
 	if state.DBG_trace_tc {
 		n.Device.InstallFilter(func(dev *device.Device, packet *device.TCElement) (device.TCAction, error) {
@@ -33,7 +35,7 @@ func (n *Nylon) InstallTC(s *state.State) {
 					peer != nil &&
 					src != netip.IPv4Unspecified() && src != netip.IPv6Unspecified() &&
 					dst != netip.IPv4Unspecified() && dst != netip.IPv6Unspecified() {
-					dev.Log.Verbosef("Unhandled TC packet: %v -> %v, peer %s", packet.GetSrc(), packet.GetDst(), peer)
+					t.Submit(fmt.Sprintf("Unhandled TC packet: %v -> %v, peer %s\n", packet.GetSrc(), packet.GetDst(), peer))
 				}
 			}
 			return device.TcPass, nil
@@ -56,7 +58,7 @@ func (n *Nylon) InstallTC(s *state.State) {
 			if ok && !packet.Incoming() {
 				packet.ToPeer = entry.Peer
 				if state.DBG_trace_tc {
-					dev.Log.Verbosef("Fwd packet: %v -> %v, via %s", packet.GetSrc(), packet.GetDst(), entry.Nh)
+					t.Submit(fmt.Sprintf("Fwd packet: %v -> %v, via %s\n", packet.GetSrc(), packet.GetDst(), entry.Nh))
 				}
 				return device.TcForward, nil
 			}
@@ -69,7 +71,7 @@ func (n *Nylon) InstallTC(s *state.State) {
 			if ok {
 				packet.ToPeer = entry.Peer
 				if state.DBG_trace_tc {
-					dev.Log.Verbosef("Fwd packet: %v -> %v, via %s", packet.GetSrc(), packet.GetDst(), entry.Nh)
+					t.Submit(fmt.Sprintf("Fwd packet: %v -> %v, via %s\n", packet.GetSrc(), packet.GetDst(), entry.Nh))
 				}
 				return device.TcForward, nil
 			}
@@ -87,7 +89,7 @@ func (n *Nylon) InstallTC(s *state.State) {
 				}
 				if ttl == 0 {
 					if state.DBG_trace_tc {
-						dev.Log.Verbosef("TTL Expired: %v -> %v, via %s", packet.GetSrc(), packet.GetDst())
+						t.Submit(fmt.Sprintf("TTL Expired: %v -> %v\n", packet.GetSrc(), packet.GetDst()))
 					}
 					return device.TcBounce, nil
 				}
@@ -103,6 +105,9 @@ func (n *Nylon) InstallTC(s *state.State) {
 		entry, ok := r.ExitTable.Lookup(packet.GetDst())
 		// we should only accept packets destined to us, but not our passive clients
 		if ok && entry.Nh == s.Id {
+			if state.DBG_trace_tc {
+				t.Submit(fmt.Sprintf("Exit: %v -> %v\n", packet.GetSrc(), packet.GetDst()))
+			}
 			//dev.Log.Verbosef("BounceCur packet: %v -> %v", packet.GetSrc(), packet.GetDst())
 			return device.TcBounce, nil
 		}

core/nylon_trace.go

@@ -0,0 +1,19 @@
+package core
+
+import (
+	"github.com/dustin/go-broadcast"
+	"github.com/encodeous/nylon/state"
+)
+
+type NylonTrace struct {
+	broadcast.Broadcaster
+}
+
+func (n *NylonTrace) Init(s *state.State) error {
+	n.Broadcaster = broadcast.NewBroadcaster(1024)
+	return nil
+}
+
+func (n *NylonTrace) Cleanup(s *state.State) error {
+	return n.Broadcaster.Close()
+}

core/router.go

@@ -97,6 +97,9 @@ func (r *NylonRouter) BroadcastRequestSeqno(src state.Source, seqno uint16, hopC
 }
 
 func (r *NylonRouter) Log(event RouterEvent, desc string, args ...any) {
+	if event == NoEpToNeighbour {
+		return // ignored
+	}
 	r.Env.Log.Debug(fmt.Sprintf("%s %s", event.String(), desc), args...)
 }
 

go.mod

@@ -44,6 +44,7 @@ require (
 	github.com/distribution/reference v0.6.0 // indirect
 	github.com/docker/go-connections v0.6.0 // indirect
 	github.com/docker/go-units v0.5.0 // indirect
+	github.com/dustin/go-broadcast v0.0.0-20211018055107-71439988bd91 // indirect
 	github.com/ebitengine/purego v0.8.4 // indirect
 	github.com/felixge/httpsnoop v1.0.4 // indirect
 	github.com/go-logr/logr v1.4.3 // indirect

go.sum

@@ -43,6 +43,8 @@ github.com/docker/go-connections v0.6.0 h1:LlMG9azAe1TqfR7sO+NJttz1gy6KO7VJBh+pM
 github.com/docker/go-connections v0.6.0/go.mod h1:AahvXYshr6JgfUJGdDCs2b5EZG/vmaMAntpSFH5BFKE=
 github.com/docker/go-units v0.5.0 h1:69rxXcBk27SvSaaxTtLh/8llcHD8vYHT7WSdRZ/jvr4=
 github.com/docker/go-units v0.5.0/go.mod h1:fgPhTUdO+D/Jk86RDLlptpiXQzgHJF7gydDDbaIK4Dk=
+github.com/dustin/go-broadcast v0.0.0-20211018055107-71439988bd91 h1:jAUM3D1KIrJmwx60DKB+a/qqM69yHnu6otDGVa2t0vs=
+github.com/dustin/go-broadcast v0.0.0-20211018055107-71439988bd91/go.mod h1:8rK6Kbo1Jd6sK22b24aPVgAm3jlNy1q1ft+lBALdIqA=
 github.com/ebitengine/purego v0.8.4 h1:CF7LEKg5FFOsASUj0+QwaXf8Ht6TlFxg09+S9wz0omw=
 github.com/ebitengine/purego v0.8.4/go.mod h1:iIjxzd6CiRiOG0UyXP+V1+jWqUXVjPKLAI0mRfJZTmQ=
 github.com/encodeous/metric v0.0.0-20251111175231-f339c2f7c4bd h1:B32Ob80QTv5MomcVt709TsiWyD0QrpUYtnwW1jQFNlE=