trie: remove Key in MissingNodeError

The key was constructed from nibbles, which isn't possible for all
nodes. Remove the only use of Key in LightTrie by always retrying with
the original key that was looked up.

Author: fjl

light/trie.go

@@ -19,6 +19,7 @@ package light
 import (
 	"context"
 
+	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/trie"
 )
@@ -46,26 +47,18 @@ func NewLightTrie(id *TrieID, odr OdrBackend, useFakeMap bool) *LightTrie {
 // retrieveKey retrieves a single key, returns true and stores nodes in local
 // database if successful
 func (t *LightTrie) retrieveKey(ctx context.Context, key []byte) bool {
-	r := &TrieRequest{Id: t.id, Key: key}
+	r := &TrieRequest{Id: t.id, Key: crypto.Keccak256(key)}
 	return t.odr.Retrieve(ctx, r) == nil
 }
 
 // do tries and retries to execute a function until it returns with no error or
 // an error type other than MissingNodeError
-func (t *LightTrie) do(ctx context.Context, fallbackKey []byte, fn func() error) error {
+func (t *LightTrie) do(ctx context.Context, key []byte, fn func() error) error {
 	err := fn()
 	for err != nil {
-		mn, ok := err.(*trie.MissingNodeError)
-		if !ok {
+		if _, ok := err.(*trie.MissingNodeError); !ok {
 			return err
 		}
-
-		var key []byte
-		if mn.PrefixLen+mn.SuffixLen > 0 {
-			key = mn.Key
-		} else {
-			key = fallbackKey
-		}
 		if !t.retrieveKey(ctx, key) {
 			break
 		}

trie/errors.go

@@ -30,10 +30,6 @@ import (
 //
 // RootHash is the original root of the trie that contains the node
 //
-// Key is a binary-encoded key that contains the prefix that leads to the first
-// missing node and optionally a suffix that hints on which further nodes should
-// also be retrieved
-//
 // PrefixLen is the nibble length of the key prefix that leads from the root to
 // the missing node
 //
@@ -42,7 +38,6 @@ import (
 // such hints in the error message)
 type MissingNodeError struct {
 	RootHash, NodeHash   common.Hash
-	Key                  []byte
 	PrefixLen, SuffixLen int
 }
 

trie/trie.go

@@ -450,7 +450,6 @@ func (t *Trie) resolveHash(n hashNode, prefix, suffix []byte) (node, error) {
 		return nil, &MissingNodeError{
 			RootHash:  t.originalRoot,
 			NodeHash:  common.BytesToHash(n),
-			Key:       compactHexEncode(append(prefix, suffix...)),
 			PrefixLen: len(prefix),
 			SuffixLen: len(suffix),
 		}