p2p/enr: initial implementation (#15585)

Initial implementation of ENR according to ethereum/EIPs#778

p2p/enr/entries.go

@@ -0,0 +1,160 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package enr
+
+import (
+	"crypto/ecdsa"
+	"fmt"
+	"io"
+	"net"
+
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/rlp"
+)
+
+// Entry is implemented by known node record entry types.
+//
+// To define a new entry that is to be included in a node record,
+// create a Go type that satisfies this interface. The type should
+// also implement rlp.Decoder if additional checks are needed on the value.
+type Entry interface {
+	ENRKey() string
+}
+
+type generic struct {
+	key   string
+	value interface{}
+}
+
+func (g generic) ENRKey() string { return g.key }
+
+func (g generic) EncodeRLP(w io.Writer) error {
+	return rlp.Encode(w, g.value)
+}
+
+func (g *generic) DecodeRLP(s *rlp.Stream) error {
+	return s.Decode(g.value)
+}
+
+// WithEntry wraps any value with a key name. It can be used to set and load arbitrary values
+// in a record. The value v must be supported by rlp. To use WithEntry with Load, the value
+// must be a pointer.
+func WithEntry(k string, v interface{}) Entry {
+	return &generic{key: k, value: v}
+}
+
+// DiscPort is the "discv5" key, which holds the UDP port for discovery v5.
+type DiscPort uint16
+
+func (v DiscPort) ENRKey() string { return "discv5" }
+
+// ID is the "id" key, which holds the name of the identity scheme.
+type ID string
+
+func (v ID) ENRKey() string { return "id" }
+
+// IP4 is the "ip4" key, which holds a 4-byte IPv4 address.
+type IP4 net.IP
+
+func (v IP4) ENRKey() string { return "ip4" }
+
+// EncodeRLP implements rlp.Encoder.
+func (v IP4) EncodeRLP(w io.Writer) error {
+	ip4 := net.IP(v).To4()
+	if ip4 == nil {
+		return fmt.Errorf("invalid IPv4 address: %v", v)
+	}
+	return rlp.Encode(w, ip4)
+}
+
+// DecodeRLP implements rlp.Decoder.
+func (v *IP4) DecodeRLP(s *rlp.Stream) error {
+	if err := s.Decode((*net.IP)(v)); err != nil {
+		return err
+	}
+	if len(*v) != 4 {
+		return fmt.Errorf("invalid IPv4 address, want 4 bytes: %v", *v)
+	}
+	return nil
+}
+
+// IP6 is the "ip6" key, which holds a 16-byte IPv6 address.
+type IP6 net.IP
+
+func (v IP6) ENRKey() string { return "ip6" }
+
+// EncodeRLP implements rlp.Encoder.
+func (v IP6) EncodeRLP(w io.Writer) error {
+	ip6 := net.IP(v)
+	return rlp.Encode(w, ip6)
+}
+
+// DecodeRLP implements rlp.Decoder.
+func (v *IP6) DecodeRLP(s *rlp.Stream) error {
+	if err := s.Decode((*net.IP)(v)); err != nil {
+		return err
+	}
+	if len(*v) != 16 {
+		return fmt.Errorf("invalid IPv6 address, want 16 bytes: %v", *v)
+	}
+	return nil
+}
+
+// Secp256k1 is the "secp256k1" key, which holds a public key.
+type Secp256k1 ecdsa.PublicKey
+
+func (v Secp256k1) ENRKey() string { return "secp256k1" }
+
+// EncodeRLP implements rlp.Encoder.
+func (v Secp256k1) EncodeRLP(w io.Writer) error {
+	return rlp.Encode(w, crypto.CompressPubkey((*ecdsa.PublicKey)(&v)))
+}
+
+// DecodeRLP implements rlp.Decoder.
+func (v *Secp256k1) DecodeRLP(s *rlp.Stream) error {
+	buf, err := s.Bytes()
+	if err != nil {
+		return err
+	}
+	pk, err := crypto.DecompressPubkey(buf)
+	if err != nil {
+		return err
+	}
+	*v = (Secp256k1)(*pk)
+	return nil
+}
+
+// KeyError is an error related to a key.
+type KeyError struct {
+	Key string
+	Err error
+}
+
+// Error implements error.
+func (err *KeyError) Error() string {
+	if err.Err == errNotFound {
+		return fmt.Sprintf("missing ENR key %q", err.Key)
+	}
+	return fmt.Sprintf("ENR key %q: %v", err.Key, err.Err)
+}
+
+// IsNotFound reports whether the given error means that a key/value pair is
+// missing from a record.
+func IsNotFound(err error) bool {
+	kerr, ok := err.(*KeyError)
+	return ok && kerr.Err == errNotFound
+}