diff options
| -rw-r--r-- | p2p/enr/enr.go | 290 | ||||
| -rw-r--r-- | p2p/enr/enr_test.go | 318 | ||||
| -rw-r--r-- | p2p/enr/entries.go | 160 |
3 files changed, 768 insertions, 0 deletions
diff --git a/p2p/enr/enr.go b/p2p/enr/enr.go new file mode 100644 index 000000000..2c3afb43e --- /dev/null +++ b/p2p/enr/enr.go @@ -0,0 +1,290 @@ +// 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 implements Ethereum Node Records as defined in EIP-778. A node record holds +// arbitrary information about a node on the peer-to-peer network. +// +// Records contain named keys. To store and retrieve key/values in a record, use the Entry +// interface. +// +// Records must be signed before transmitting them to another node. Decoding a record verifies +// its signature. When creating a record, set the entries you want, then call Sign to add the +// signature. Modifying a record invalidates the signature. +// +// Package enr supports the "secp256k1-keccak" identity scheme. +package enr + +import ( + "bytes" + "crypto/ecdsa" + "errors" + "fmt" + "io" + "sort" + + "github.com/ethereum/go-ethereum/crypto" + "github.com/ethereum/go-ethereum/crypto/sha3" + "github.com/ethereum/go-ethereum/rlp" +) + +const SizeLimit = 300 // maximum encoded size of a node record in bytes + +const ID_SECP256k1_KECCAK = ID("secp256k1-keccak") // the default identity scheme + +var ( + errNoID = errors.New("unknown or unspecified identity scheme") + errInvalidSigsize = errors.New("invalid signature size") + errInvalidSig = errors.New("invalid signature") + errNotSorted = errors.New("record key/value pairs are not sorted by key") + errDuplicateKey = errors.New("record contains duplicate key") + errIncompletePair = errors.New("record contains incomplete k/v pair") + errTooBig = fmt.Errorf("record bigger than %d bytes", SizeLimit) + errEncodeUnsigned = errors.New("can't encode unsigned record") + errNotFound = errors.New("no such key in record") +) + +// Record represents a node record. The zero value is an empty record. +type Record struct { + seq uint64 // sequence number + signature []byte // the signature + raw []byte // RLP encoded record + pairs []pair // sorted list of all key/value pairs +} + +// pair is a key/value pair in a record. +type pair struct { + k string + v rlp.RawValue +} + +// Signed reports whether the record has a valid signature. +func (r *Record) Signed() bool { + return r.signature != nil +} + +// Seq returns the sequence number. +func (r *Record) Seq() uint64 { + return r.seq +} + +// SetSeq updates the record sequence number. This invalidates any signature on the record. +// Calling SetSeq is usually not required because signing the redord increments the +// sequence number. +func (r *Record) SetSeq(s uint64) { + r.signature = nil + r.raw = nil + r.seq = s +} + +// Load retrieves the value of a key/value pair. The given Entry must be a pointer and will +// be set to the value of the entry in the record. +// +// Errors returned by Load are wrapped in KeyError. You can distinguish decoding errors +// from missing keys using the IsNotFound function. +func (r *Record) Load(e Entry) error { + i := sort.Search(len(r.pairs), func(i int) bool { return r.pairs[i].k >= e.ENRKey() }) + if i < len(r.pairs) && r.pairs[i].k == e.ENRKey() { + if err := rlp.DecodeBytes(r.pairs[i].v, e); err != nil { + return &KeyError{Key: e.ENRKey(), Err: err} + } + return nil + } + return &KeyError{Key: e.ENRKey(), Err: errNotFound} +} + +// Set adds or updates the given entry in the record. +// It panics if the value can't be encoded. +func (r *Record) Set(e Entry) { + r.signature = nil + r.raw = nil + blob, err := rlp.EncodeToBytes(e) + if err != nil { + panic(fmt.Errorf("enr: can't encode %s: %v", e.ENRKey(), err)) + } + + i := sort.Search(len(r.pairs), func(i int) bool { return r.pairs[i].k >= e.ENRKey() }) + + if i < len(r.pairs) && r.pairs[i].k == e.ENRKey() { + // element is present at r.pairs[i] + r.pairs[i].v = blob + return + } else if i < len(r.pairs) { + // insert pair before i-th elem + el := pair{e.ENRKey(), blob} + r.pairs = append(r.pairs, pair{}) + copy(r.pairs[i+1:], r.pairs[i:]) + r.pairs[i] = el + return + } + + // element should be placed at the end of r.pairs + r.pairs = append(r.pairs, pair{e.ENRKey(), blob}) +} + +// EncodeRLP implements rlp.Encoder. Encoding fails if +// the record is unsigned. +func (r Record) EncodeRLP(w io.Writer) error { + if !r.Signed() { + return errEncodeUnsigned + } + _, err := w.Write(r.raw) + return err +} + +// DecodeRLP implements rlp.Decoder. Decoding verifies the signature. +func (r *Record) DecodeRLP(s *rlp.Stream) error { + raw, err := s.Raw() + if err != nil { + return err + } + if len(raw) > SizeLimit { + return errTooBig + } + + // Decode the RLP container. + dec := Record{raw: raw} + s = rlp.NewStream(bytes.NewReader(raw), 0) + if _, err := s.List(); err != nil { + return err + } + if err = s.Decode(&dec.signature); err != nil { + return err + } + if err = s.Decode(&dec.seq); err != nil { + return err + } + // The rest of the record contains sorted k/v pairs. + var prevkey string + for i := 0; ; i++ { + var kv pair + if err := s.Decode(&kv.k); err != nil { + if err == rlp.EOL { + break + } + return err + } + if err := s.Decode(&kv.v); err != nil { + if err == rlp.EOL { + return errIncompletePair + } + return err + } + if i > 0 { + if kv.k == prevkey { + return errDuplicateKey + } + if kv.k < prevkey { + return errNotSorted + } + } + dec.pairs = append(dec.pairs, kv) + prevkey = kv.k + } + if err := s.ListEnd(); err != nil { + return err + } + + // Verify signature. + if err = dec.verifySignature(); err != nil { + return err + } + *r = dec + return nil +} + +type s256raw []byte + +func (s256raw) ENRKey() string { return "secp256k1" } + +// NodeAddr returns the node address. The return value will be nil if the record is +// unsigned. +func (r *Record) NodeAddr() []byte { + var entry s256raw + if r.Load(&entry) != nil { + return nil + } + return crypto.Keccak256(entry) +} + +// Sign signs the record with the given private key. It updates the record's identity +// scheme, public key and increments the sequence number. Sign returns an error if the +// encoded record is larger than the size limit. +func (r *Record) Sign(privkey *ecdsa.PrivateKey) error { + r.seq = r.seq + 1 + r.Set(ID_SECP256k1_KECCAK) + r.Set(Secp256k1(privkey.PublicKey)) + return r.signAndEncode(privkey) +} + +func (r *Record) appendPairs(list []interface{}) []interface{} { + list = append(list, r.seq) + for _, p := range r.pairs { + list = append(list, p.k, p.v) + } + return list +} + +func (r *Record) signAndEncode(privkey *ecdsa.PrivateKey) error { + // Put record elements into a flat list. Leave room for the signature. + list := make([]interface{}, 1, len(r.pairs)*2+2) + list = r.appendPairs(list) + + // Sign the tail of the list. + h := sha3.NewKeccak256() + rlp.Encode(h, list[1:]) + sig, err := crypto.Sign(h.Sum(nil), privkey) + if err != nil { + return err + } + sig = sig[:len(sig)-1] // remove v + + // Put signature in front. + r.signature, list[0] = sig, sig + r.raw, err = rlp.EncodeToBytes(list) + if err != nil { + return err + } + if len(r.raw) > SizeLimit { + return errTooBig + } + return nil +} + +func (r *Record) verifySignature() error { + // Get identity scheme, public key, signature. + var id ID + var entry s256raw + if err := r.Load(&id); err != nil { + return err + } else if id != ID_SECP256k1_KECCAK { + return errNoID + } + if err := r.Load(&entry); err != nil { + return err + } else if len(entry) != 33 { + return fmt.Errorf("invalid public key") + } + + // Verify the signature. + list := make([]interface{}, 0, len(r.pairs)*2+1) + list = r.appendPairs(list) + h := sha3.NewKeccak256() + rlp.Encode(h, list) + if !crypto.VerifySignature(entry, h.Sum(nil), r.signature) { + return errInvalidSig + } + return nil +} diff --git a/p2p/enr/enr_test.go b/p2p/enr/enr_test.go new file mode 100644 index 000000000..ce7767d10 --- /dev/null +++ b/p2p/enr/enr_test.go @@ -0,0 +1,318 @@ +// 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 ( + "bytes" + "encoding/hex" + "fmt" + "math/rand" + "testing" + "time" + + "github.com/ethereum/go-ethereum/crypto" + "github.com/ethereum/go-ethereum/rlp" + "github.com/stretchr/testify/assert" + "github.com/stretchr/testify/require" +) + +var ( + privkey, _ = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291") + pubkey = &privkey.PublicKey +) + +var rnd = rand.New(rand.NewSource(time.Now().UnixNano())) + +func randomString(strlen int) string { + b := make([]byte, strlen) + rnd.Read(b) + return string(b) +} + +// TestGetSetID tests encoding/decoding and setting/getting of the ID key. +func TestGetSetID(t *testing.T) { + id := ID("someid") + var r Record + r.Set(id) + + var id2 ID + require.NoError(t, r.Load(&id2)) + assert.Equal(t, id, id2) +} + +// TestGetSetIP4 tests encoding/decoding and setting/getting of the IP4 key. +func TestGetSetIP4(t *testing.T) { + ip := IP4{192, 168, 0, 3} + var r Record + r.Set(ip) + + var ip2 IP4 + require.NoError(t, r.Load(&ip2)) + assert.Equal(t, ip, ip2) +} + +// TestGetSetIP6 tests encoding/decoding and setting/getting of the IP6 key. +func TestGetSetIP6(t *testing.T) { + ip := IP6{0x20, 0x01, 0x48, 0x60, 0, 0, 0x20, 0x01, 0, 0, 0, 0, 0, 0, 0x00, 0x68} + var r Record + r.Set(ip) + + var ip2 IP6 + require.NoError(t, r.Load(&ip2)) + assert.Equal(t, ip, ip2) +} + +// TestGetSetDiscPort tests encoding/decoding and setting/getting of the DiscPort key. +func TestGetSetDiscPort(t *testing.T) { + port := DiscPort(30309) + var r Record + r.Set(port) + + var port2 DiscPort + require.NoError(t, r.Load(&port2)) + assert.Equal(t, port, port2) +} + +// TestGetSetSecp256k1 tests encoding/decoding and setting/getting of the Secp256k1 key. +func TestGetSetSecp256k1(t *testing.T) { + var r Record + if err := r.Sign(privkey); err != nil { + t.Fatal(err) + } + + var pk Secp256k1 + require.NoError(t, r.Load(&pk)) + assert.EqualValues(t, pubkey, &pk) +} + +func TestLoadErrors(t *testing.T) { + var r Record + ip4 := IP4{127, 0, 0, 1} + r.Set(ip4) + + // Check error for missing keys. + var ip6 IP6 + err := r.Load(&ip6) + if !IsNotFound(err) { + t.Error("IsNotFound should return true for missing key") + } + assert.Equal(t, &KeyError{Key: ip6.ENRKey(), Err: errNotFound}, err) + + // Check error for invalid keys. + var list []uint + err = r.Load(WithEntry(ip4.ENRKey(), &list)) + kerr, ok := err.(*KeyError) + if !ok { + t.Fatalf("expected KeyError, got %T", err) + } + assert.Equal(t, kerr.Key, ip4.ENRKey()) + assert.Error(t, kerr.Err) + if IsNotFound(err) { + t.Error("IsNotFound should return false for decoding errors") + } +} + +// TestSortedGetAndSet tests that Set produced a sorted pairs slice. +func TestSortedGetAndSet(t *testing.T) { + type pair struct { + k string + v uint32 + } + + for _, tt := range []struct { + input []pair + want []pair + }{ + { + input: []pair{{"a", 1}, {"c", 2}, {"b", 3}}, + want: []pair{{"a", 1}, {"b", 3}, {"c", 2}}, + }, + { + input: []pair{{"a", 1}, {"c", 2}, {"b", 3}, {"d", 4}, {"a", 5}, {"bb", 6}}, + want: []pair{{"a", 5}, {"b", 3}, {"bb", 6}, {"c", 2}, {"d", 4}}, + }, + { + input: []pair{{"c", 2}, {"b", 3}, {"d", 4}, {"a", 5}, {"bb", 6}}, + want: []pair{{"a", 5}, {"b", 3}, {"bb", 6}, {"c", 2}, {"d", 4}}, + }, + } { + var r Record + for _, i := range tt.input { + r.Set(WithEntry(i.k, &i.v)) + } + for i, w := range tt.want { + // set got's key from r.pair[i], so that we preserve order of pairs + got := pair{k: r.pairs[i].k} + assert.NoError(t, r.Load(WithEntry(w.k, &got.v))) + assert.Equal(t, w, got) + } + } +} + +// TestDirty tests record signature removal on setting of new key/value pair in record. +func TestDirty(t *testing.T) { + var r Record + + if r.Signed() { + t.Error("Signed returned true for zero record") + } + if _, err := rlp.EncodeToBytes(r); err != errEncodeUnsigned { + t.Errorf("expected errEncodeUnsigned, got %#v", err) + } + + require.NoError(t, r.Sign(privkey)) + if !r.Signed() { + t.Error("Signed return false for signed record") + } + _, err := rlp.EncodeToBytes(r) + assert.NoError(t, err) + + r.SetSeq(3) + if r.Signed() { + t.Error("Signed returned true for modified record") + } + if _, err := rlp.EncodeToBytes(r); err != errEncodeUnsigned { + t.Errorf("expected errEncodeUnsigned, got %#v", err) + } +} + +// TestGetSetOverwrite tests value overwrite when setting a new value with an existing key in record. +func TestGetSetOverwrite(t *testing.T) { + var r Record + + ip := IP4{192, 168, 0, 3} + r.Set(ip) + + ip2 := IP4{192, 168, 0, 4} + r.Set(ip2) + + var ip3 IP4 + require.NoError(t, r.Load(&ip3)) + assert.Equal(t, ip2, ip3) +} + +// TestSignEncodeAndDecode tests signing, RLP encoding and RLP decoding of a record. +func TestSignEncodeAndDecode(t *testing.T) { + var r Record + r.Set(DiscPort(30303)) + r.Set(IP4{127, 0, 0, 1}) + require.NoError(t, r.Sign(privkey)) + + blob, err := rlp.EncodeToBytes(r) + require.NoError(t, err) + + var r2 Record + require.NoError(t, rlp.DecodeBytes(blob, &r2)) + assert.Equal(t, r, r2) + + blob2, err := rlp.EncodeToBytes(r2) + require.NoError(t, err) + assert.Equal(t, blob, blob2) +} + +func TestNodeAddr(t *testing.T) { + var r Record + if addr := r.NodeAddr(); addr != nil { + t.Errorf("wrong address on empty record: got %v, want %v", addr, nil) + } + + require.NoError(t, r.Sign(privkey)) + expected := "caaa1485d83b18b32ed9ad666026151bf0cae8a0a88c857ae2d4c5be2daa6726" + assert.Equal(t, expected, hex.EncodeToString(r.NodeAddr())) +} + +var pyRecord, _ = hex.DecodeString("f896b840954dc36583c1f4b69ab59b1375f362f06ee99f3723cd77e64b6de6d211c27d7870642a79d4516997f94091325d2a7ca6215376971455fb221d34f35b277149a1018664697363763582765f82696490736563703235366b312d6b656363616b83697034847f00000189736563703235366b31a103ca634cae0d49acb401d8a4c6b6fe8c55b70d115bf400769cc1400f3258cd3138") + +// TestPythonInterop checks that we can decode and verify a record produced by the Python +// implementation. +func TestPythonInterop(t *testing.T) { + var r Record + if err := rlp.DecodeBytes(pyRecord, &r); err != nil { + t.Fatalf("can't decode: %v", err) + } + + var ( + wantAddr, _ = hex.DecodeString("caaa1485d83b18b32ed9ad666026151bf0cae8a0a88c857ae2d4c5be2daa6726") + wantSeq = uint64(1) + wantIP = IP4{127, 0, 0, 1} + wantDiscport = DiscPort(30303) + ) + if r.Seq() != wantSeq { + t.Errorf("wrong seq: got %d, want %d", r.Seq(), wantSeq) + } + if addr := r.NodeAddr(); !bytes.Equal(addr, wantAddr) { + t.Errorf("wrong addr: got %x, want %x", addr, wantAddr) + } + want := map[Entry]interface{}{new(IP4): &wantIP, new(DiscPort): &wantDiscport} + for k, v := range want { + desc := fmt.Sprintf("loading key %q", k.ENRKey()) + if assert.NoError(t, r.Load(k), desc) { + assert.Equal(t, k, v, desc) + } + } +} + +// TestRecordTooBig tests that records bigger than SizeLimit bytes cannot be signed. +func TestRecordTooBig(t *testing.T) { + var r Record + key := randomString(10) + + // set a big value for random key, expect error + r.Set(WithEntry(key, randomString(300))) + if err := r.Sign(privkey); err != errTooBig { + t.Fatalf("expected to get errTooBig, got %#v", err) + } + + // set an acceptable value for random key, expect no error + r.Set(WithEntry(key, randomString(100))) + require.NoError(t, r.Sign(privkey)) +} + +// TestSignEncodeAndDecodeRandom tests encoding/decoding of records containing random key/value pairs. +func TestSignEncodeAndDecodeRandom(t *testing.T) { + var r Record + + // random key/value pairs for testing + pairs := map[string]uint32{} + for i := 0; i < 10; i++ { + key := randomString(7) + value := rnd.Uint32() + pairs[key] = value + r.Set(WithEntry(key, &value)) + } + + require.NoError(t, r.Sign(privkey)) + _, err := rlp.EncodeToBytes(r) + require.NoError(t, err) + + for k, v := range pairs { + desc := fmt.Sprintf("key %q", k) + var got uint32 + buf := WithEntry(k, &got) + require.NoError(t, r.Load(buf), desc) + require.Equal(t, v, got, desc) + } +} + +func BenchmarkDecode(b *testing.B) { + var r Record + for i := 0; i < b.N; i++ { + rlp.DecodeBytes(pyRecord, &r) + } + b.StopTimer() + r.NodeAddr() +} diff --git a/p2p/enr/entries.go b/p2p/enr/entries.go new file mode 100644 index 000000000..7591e6eff --- /dev/null +++ b/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 +} |