p2p/discover/v4wire: use optional RLP field for EIP-868 seq (#22842)

This changes the definitions of Ping and Pong, adding an optional field
for the sequence number. This field was previously encoded/decoded using
the "tail" struct tag, but using "optional" is much nicer.

p2p/discover/v4_udp.go

@@ -34,7 +34,6 @@ import (
 	"github.com/ethereum/go-ethereum/p2p/discover/v4wire"
 	"github.com/ethereum/go-ethereum/p2p/enode"
 	"github.com/ethereum/go-ethereum/p2p/netutil"
-	"github.com/ethereum/go-ethereum/rlp"
 )
 
 // Errors
@@ -217,7 +216,7 @@ func (t *UDPv4) Ping(n *enode.Node) error {
 func (t *UDPv4) ping(n *enode.Node) (seq uint64, err error) {
 	rm := t.sendPing(n.ID(), &net.UDPAddr{IP: n.IP(), Port: n.UDP()}, nil)
 	if err = <-rm.errc; err == nil {
-		seq = rm.reply.(*v4wire.Pong).ENRSeq()
+		seq = rm.reply.(*v4wire.Pong).ENRSeq
 	}
 	return seq, err
 }
@@ -248,13 +247,12 @@ func (t *UDPv4) sendPing(toid enode.ID, toaddr *net.UDPAddr, callback func()) *r
 }
 
 func (t *UDPv4) makePing(toaddr *net.UDPAddr) *v4wire.Ping {
-	seq, _ := rlp.EncodeToBytes(t.localNode.Node().Seq())
 	return &v4wire.Ping{
 		Version:    4,
 		From:       t.ourEndpoint(),
 		To:         v4wire.NewEndpoint(toaddr, 0),
 		Expiration: uint64(time.Now().Add(expiration).Unix()),
-		Rest:       []rlp.RawValue{seq},
+		ENRSeq:     t.localNode.Node().Seq(),
 	}
 }
 
@@ -660,12 +658,11 @@ func (t *UDPv4) handlePing(h *packetHandlerV4, from *net.UDPAddr, fromID enode.I
 	req := h.Packet.(*v4wire.Ping)
 
 	// Reply.
-	seq, _ := rlp.EncodeToBytes(t.localNode.Node().Seq())
 	t.send(from, fromID, &v4wire.Pong{
 		To:         v4wire.NewEndpoint(from, req.From.TCP),
 		ReplyTok:   mac,
 		Expiration: uint64(time.Now().Add(expiration).Unix()),
-		Rest:       []rlp.RawValue{seq},
+		ENRSeq:     t.localNode.Node().Seq(),
 	})
 
 	// Ping back if our last pong on file is too far in the past.

p2p/discover/v4_udp_test.go

@@ -470,13 +470,13 @@ func TestUDPv4_EIP868(t *testing.T) {
 	// Perform endpoint proof and check for sequence number in packet tail.
 	test.packetIn(nil, &v4wire.Ping{Expiration: futureExp})
 	test.waitPacketOut(func(p *v4wire.Pong, addr *net.UDPAddr, hash []byte) {
-		if p.ENRSeq() != wantNode.Seq() {
+		if p.ENRSeq != wantNode.Seq() {
-			t.Errorf("wrong sequence number in pong: %d, want %d", p.ENRSeq(), wantNode.Seq())
+			t.Errorf("wrong sequence number in pong: %d, want %d", p.ENRSeq, wantNode.Seq())
 		}
 	})
 	test.waitPacketOut(func(p *v4wire.Ping, addr *net.UDPAddr, hash []byte) {
-		if p.ENRSeq() != wantNode.Seq() {
+		if p.ENRSeq != wantNode.Seq() {
-			t.Errorf("wrong sequence number in ping: %d, want %d", p.ENRSeq(), wantNode.Seq())
+			t.Errorf("wrong sequence number in ping: %d, want %d", p.ENRSeq, wantNode.Seq())
 		}
 		test.packetIn(nil, &v4wire.Pong{Expiration: futureExp, ReplyTok: hash})
 	})

p2p/discover/v4wire/v4wire.go

@@ -50,6 +50,8 @@ type (
 		Version    uint
 		From, To   Endpoint
 		Expiration uint64
+		ENRSeq     uint64 `rlp:"optional"` // Sequence number of local record, added by EIP-868.
+
 		// Ignore additional fields (for forward compatibility).
 		Rest []rlp.RawValue `rlp:"tail"`
 	}
@@ -62,6 +64,8 @@ type (
 		To         Endpoint
 		ReplyTok   []byte // This contains the hash of the ping packet.
 		Expiration uint64 // Absolute timestamp at which the packet becomes invalid.
+		ENRSeq     uint64 `rlp:"optional"` // Sequence number of local record, added by EIP-868.
+
 		// Ignore additional fields (for forward compatibility).
 		Rest []rlp.RawValue `rlp:"tail"`
 	}
@@ -162,13 +166,11 @@ type Packet interface {
 	Kind() byte
 }
 
-func (req *Ping) Name() string   { return "PING/v4" }
+func (req *Ping) Name() string { return "PING/v4" }
-func (req *Ping) Kind() byte     { return PingPacket }
+func (req *Ping) Kind() byte   { return PingPacket }
-func (req *Ping) ENRSeq() uint64 { return seqFromTail(req.Rest) }
 
-func (req *Pong) Name() string   { return "PONG/v4" }
+func (req *Pong) Name() string { return "PONG/v4" }
-func (req *Pong) Kind() byte     { return PongPacket }
+func (req *Pong) Kind() byte   { return PongPacket }
-func (req *Pong) ENRSeq() uint64 { return seqFromTail(req.Rest) }
 
 func (req *Findnode) Name() string { return "FINDNODE/v4" }
 func (req *Findnode) Kind() byte   { return FindnodePacket }
@@ -187,15 +189,6 @@ func Expired(ts uint64) bool {
 	return time.Unix(int64(ts), 0).Before(time.Now())
 }
 
-func seqFromTail(tail []rlp.RawValue) uint64 {
-	if len(tail) == 0 {
-		return 0
-	}
-	var seq uint64
-	rlp.DecodeBytes(tail[0], &seq)
-	return seq
-}
-
 // Encoder/decoder.
 
 const (

p2p/discover/v4wire/v4wire_test.go

@@ -23,7 +23,6 @@ import (
 	"testing"
 
 	"github.com/davecgh/go-spew/spew"
-	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/rlp"
 )
@@ -40,7 +39,6 @@ var testPackets = []struct {
 			From:       Endpoint{net.ParseIP("127.0.0.1").To4(), 3322, 5544},
 			To:         Endpoint{net.ParseIP("::1"), 2222, 3333},
 			Expiration: 1136239445,
-			Rest:       []rlp.RawValue{},
 		},
 	},
 	{
@@ -50,26 +48,8 @@ var testPackets = []struct {
 			From:       Endpoint{net.ParseIP("127.0.0.1").To4(), 3322, 5544},
 			To:         Endpoint{net.ParseIP("::1"), 2222, 3333},
 			Expiration: 1136239445,
-			Rest:       []rlp.RawValue{{0x01}, {0x02}},
+			ENRSeq:     1,
-		},
+			Rest:       []rlp.RawValue{{0x02}},
-	},
-	{
-		input: "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",
-		wantPacket: &Ping{
-			Version:    555,
-			From:       Endpoint{net.ParseIP("2001:db8:3c4d:15::abcd:ef12"), 3322, 5544},
-			To:         Endpoint{net.ParseIP("2001:db8:85a3:8d3:1319:8a2e:370:7348"), 2222, 33338},
-			Expiration: 1136239445,
-			Rest:       []rlp.RawValue{{0xC5, 0x01, 0x02, 0x03, 0x04, 0x05}},
-		},
-	},
-	{
-		input: "09b2428d83348d27cdf7064ad9024f526cebc19e4958f0fdad87c15eb598dd61d08423e0bf66b2069869e1724125f820d851c136684082774f870e614d95a2855d000f05d1648b2d5945470bc187c2d2216fbe870f43ed0909009882e176a46b0102f846d79020010db885a308d313198a2e037073488208ae82823aa0fbc914b16819237dcd8801d7e53f69e9719adecb3cc0e790c57e91ca4461c9548443b9a355c6010203c2040506a0c969a58f6f9095004c0177a6b47f451530cab38966a25cca5cb58f055542124e",
-		wantPacket: &Pong{
-			To:         Endpoint{net.ParseIP("2001:db8:85a3:8d3:1319:8a2e:370:7348"), 2222, 33338},
-			ReplyTok:   common.Hex2Bytes("fbc914b16819237dcd8801d7e53f69e9719adecb3cc0e790c57e91ca4461c954"),
-			Expiration: 1136239445,
-			Rest:       []rlp.RawValue{{0xC6, 0x01, 0x02, 0x03, 0xC2, 0x04, 0x05}, {0x06}},
 		},
 	},
 	{