les, light: LES/2 protocol version (#14970)

This PR implements the new LES protocol version extensions:

* new and more efficient Merkle proofs reply format (when replying to
  a multiple Merkle proofs request, we just send a single set of trie
  nodes containing all necessary nodes)
* BBT (BloomBitsTrie) works similarly to the existing CHT and contains
  the bloombits search data to speed up log searches
* GetTxStatusMsg returns the inclusion position or the
  pending/queued/unknown state of a transaction referenced by hash
* an optional signature of new block data (number/hash/td) can be
  included in AnnounceMsg to provide an option for "very light
  clients" (mobile/embedded devices) to skip expensive Ethash check
  and accept multiple signatures of somewhat trusted servers (still a
  lot better than trusting a single server completely and retrieving
  everything through RPC). The new client mode is not implemented in
  this PR, just the protocol extension.

trie/proof.go

@@ -18,11 +18,10 @@ package trie
 
 import (
 	"bytes"
-	"errors"
 	"fmt"
 
 	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/crypto/sha3"
+	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/rlp"
 )
@@ -36,7 +35,7 @@ import (
 // contains all nodes of the longest existing prefix of the key
 // (at least the root node), ending with the node that proves the
 // absence of the key.
-func (t *Trie) Prove(key []byte) []rlp.RawValue {
+func (t *Trie) Prove(key []byte, fromLevel uint, proofDb DatabaseWriter) error {
 	// Collect all nodes on the path to key.
 	key = keybytesToHex(key)
 	nodes := []node{}
@@ -61,67 +60,63 @@ func (t *Trie) Prove(key []byte) []rlp.RawValue {
 			tn, err = t.resolveHash(n, nil)
 			if err != nil {
 				log.Error(fmt.Sprintf("Unhandled trie error: %v", err))
-				return nil
+				return err
 			}
 		default:
 			panic(fmt.Sprintf("%T: invalid node: %v", tn, tn))
 		}
 	}
 	hasher := newHasher(0, 0)
-	proof := make([]rlp.RawValue, 0, len(nodes))
 	for i, n := range nodes {
 		// Don't bother checking for errors here since hasher panics
 		// if encoding doesn't work and we're not writing to any database.
 		n, _, _ = hasher.hashChildren(n, nil)
 		hn, _ := hasher.store(n, nil, false)
-		if _, ok := hn.(hashNode); ok || i == 0 {
+		if hash, ok := hn.(hashNode); ok || i == 0 {
 			// If the node's database encoding is a hash (or is the
 			// root node), it becomes a proof element.
-			enc, _ := rlp.EncodeToBytes(n)
-			proof = append(proof, enc)
+			if fromLevel > 0 {
+				fromLevel--
+			} else {
+				enc, _ := rlp.EncodeToBytes(n)
+				if !ok {
+					hash = crypto.Keccak256(enc)
+				}
+				proofDb.Put(hash, enc)
+			}
 		}
 	}
-	return proof
+	return nil
 }
 
 // VerifyProof checks merkle proofs. The given proof must contain the
 // value for key in a trie with the given root hash. VerifyProof
 // returns an error if the proof contains invalid trie nodes or the
 // wrong value.
-func VerifyProof(rootHash common.Hash, key []byte, proof []rlp.RawValue) (value []byte, err error) {
+func VerifyProof(rootHash common.Hash, key []byte, proofDb DatabaseReader) (value []byte, err error, nodes int) {
 	key = keybytesToHex(key)
-	sha := sha3.NewKeccak256()
-	wantHash := rootHash.Bytes()
-	for i, buf := range proof {
-		sha.Reset()
-		sha.Write(buf)
-		if !bytes.Equal(sha.Sum(nil), wantHash) {
-			return nil, fmt.Errorf("bad proof node %d: hash mismatch", i)
+	wantHash := rootHash[:]
+	for i := 0; ; i++ {
+		buf, _ := proofDb.Get(wantHash)
+		if buf == nil {
+			return nil, fmt.Errorf("proof node %d (hash %064x) missing", i, wantHash[:]), i
 		}
 		n, err := decodeNode(wantHash, buf, 0)
 		if err != nil {
-			return nil, fmt.Errorf("bad proof node %d: %v", i, err)
+			return nil, fmt.Errorf("bad proof node %d: %v", i, err), i
 		}
 		keyrest, cld := get(n, key)
 		switch cld := cld.(type) {
 		case nil:
-			if i != len(proof)-1 {
-				return nil, fmt.Errorf("key mismatch at proof node %d", i)
-			} else {
-				// The trie doesn't contain the key.
-				return nil, nil
-			}
+			// The trie doesn't contain the key.
+			return nil, nil, i
 		case hashNode:
 			key = keyrest
 			wantHash = cld
 		case valueNode:
-			if i != len(proof)-1 {
-				return nil, errors.New("additional nodes at end of proof")
-			}
-			return cld, nil
+			return cld, nil, i + 1
 		}
 	}
-	return nil, errors.New("unexpected end of proof")
 }
 
 func get(tn node, key []byte) ([]byte, node) {