refactor(packet): redesign as nested Packet with optional layers

Replace the tagged-union API (PacketInfo interface + TCPInfo/UDPInfo/
ICMPInfo/ARPInfo + PacketType + UnmarshalPacketInfo) with a single
Packet struct that exposes each layer as an optional pointer
(Ether/IPv4/IPv6/TCP/UDP/ICMP/ARP). Adding a protocol no longer requires
a new type + tag, JSON round-trips through std json.Unmarshal without
out-of-band dispatch, and Parse returns (*Packet, error) so callers can
distinguish unknown EtherType from truncated buffers. Layer fields are
expanded to mirror gopacket's wire-level coverage; String() now emits
in protocol-stack order (ether -> L3 -> L4).

Author: hao022

cmd/dropwatch/format.go

@@ -20,7 +20,6 @@ import (
 	"io"
 	"os"
 
-	"huatuo-bamai/internal/packet"
 	"huatuo-bamai/internal/symbol"
 	"huatuo-bamai/internal/toolstream"
 	"huatuo-bamai/pkg/types"
@@ -34,8 +33,8 @@ type writer interface {
 type textWriter struct{ w io.Writer }
 
 func (s *textWriter) Write(ev *types.DropWatchTracing) error {
-	if _, err := fmt.Fprintf(s.w, "%s %s %s len=%d dev=%s pid=%d[%s] addr=%s\n",
-		ev.ObservedTimestamp, ev.PacketType, formatDetail(ev.PacketInfo),
+	if _, err := fmt.Fprintf(s.w, "%s %s len=%d dev=%s pid=%d[%s] addr=%s\n",
+		ev.ObservedTimestamp, ev.Layers,
 		ev.PacketLen, ev.NetdevName, ev.Pid, ev.Comm, ev.PacketSkbAddr); err != nil {
 		return err
 	}
@@ -78,12 +77,3 @@ func newWriter(outputFmt string, client *toolstream.Client) writer {
 		return &textWriter{w: os.Stdout}
 	}
 }
-
-type detailable interface{ Detail() string }
-
-func formatDetail(info packet.PacketInfo) string {
-	if d, ok := info.(detailable); ok {
-		return d.Detail()
-	}
-	return "[?]"
-}

cmd/dropwatch/format_test.go

@@ -18,7 +18,6 @@ import (
 	"errors"
 	"testing"
 
-	"huatuo-bamai/internal/packet"
 	"huatuo-bamai/pkg/types"
 )
 
@@ -34,7 +33,6 @@ func TestTextWriterPropagatesIOError(t *testing.T) {
 
 	err := w.Write(&types.DropWatchTracing{
 		ObservedTimestamp: "now",
-		PacketType:        packet.PacketTypeIPv4TCP,
 		NetdevName:        "eth0",
 	})
 	if !errors.Is(err, boom) {

cmd/dropwatch/main.go

@@ -122,15 +122,18 @@ func deviceFilterConsts(devName string, excluded bool) (map[string]any, error) {
 }
 
 func formatEvent(ev *dropPacketEvent) *types.DropWatchTracing {
-	pkt := packet.PacketHdr{
+	pkt := packet.Hdr{
 		EthProto:  ev.Raw.EthProto,
 		RawLen:    uint8(ev.Raw.RawLen),
 		HasEthHdr: uint8(ev.Raw.HasEthHdr),
 		SkState:   uint8(ev.Raw.SkState),
 		Raw:       ev.Raw.Raw,
 	}
 
-	pktType, pktInfo := packet.ParsePacketHdr(&pkt)
+	p, err := packet.Parse(&pkt)
+	if err != nil {
+		log.Debugf("dropwatch: parse packet: %v", err)
+	}
 
 	frames := symbol.KsymStackStrs(ev.Stack[:], symbol.KsymStackMaxDepth)
 	stackStr := strings.Join(frames, "\n")
@@ -149,8 +152,7 @@ func formatEvent(ev *dropPacketEvent) *types.DropWatchTracing {
 		PacketSkbAddr:      kernaddr.Format(ev.Meta.SkbAddr),
 		PacketEthProto:     fmt.Sprintf("0x%04x", ev.Raw.EthProto),
 		PacketLen:          ev.Raw.PktLen,
-		PacketType:         pktType,
-		PacketInfo:         pktInfo,
+		Layers:             p,
 		Stack:              stackStr,
 	}
 }

core/events/dropwatch.go

@@ -24,7 +24,6 @@ import (
 
 	internalconfig "huatuo-bamai/internal/config"
 	"huatuo-bamai/internal/log"
-	"huatuo-bamai/internal/packet"
 	"huatuo-bamai/internal/pod"
 	"huatuo-bamai/internal/toolstream"
 	"huatuo-bamai/internal/utils/kernaddr"
@@ -150,7 +149,7 @@ func ignoreDropwatch(data *types.DropWatchTracing) bool {
 	// 4. tcp_fin/ffffffff963ac200
 	// 5. ...
 	// CLOSE_WAIT + skb_rbtree_purge: normal socket teardown, not a drop.
-	if skState := packet.TCPSkState(data.PacketInfo); skState == "CLOSE_WAIT" {
+	if data.Layers != nil && data.Layers.TCP != nil && data.Layers.TCP.SkState == "CLOSE_WAIT" {
 		if len(stack) >= 3 && strings.HasPrefix(stack[2], "skb_rbtree_purge/") {
 			return true
 		}