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.

les/protocol.go

@@ -18,24 +18,34 @@
 package les
 
 import (
+	"bytes"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"errors"
 	"fmt"
 	"io"
 	"math/big"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/crypto/secp256k1"
 	"github.com/ethereum/go-ethereum/rlp"
 )
 
 // Constants to match up protocol versions and messages
 const (
 	lpv1 = 1
+	lpv2 = 2
 )
 
-// Supported versions of the les protocol (first is primary).
-var ProtocolVersions = []uint{lpv1}
+// Supported versions of the les protocol (first is primary)
+var (
+	ClientProtocolVersions = []uint{lpv2, lpv1}
+	ServerProtocolVersions = []uint{lpv2, lpv1}
+)
 
 // Number of implemented message corresponding to different protocol versions.
-var ProtocolLengths = []uint64{15}
+var ProtocolLengths = map[uint]uint64{lpv1: 15, lpv2: 22}
 
 const (
 	NetworkId          = 1
@@ -53,13 +63,21 @@ const (
 	BlockBodiesMsg     = 0x05
 	GetReceiptsMsg     = 0x06
 	ReceiptsMsg        = 0x07
-	GetProofsMsg       = 0x08
-	ProofsMsg          = 0x09
+	GetProofsV1Msg     = 0x08
+	ProofsV1Msg        = 0x09
 	GetCodeMsg         = 0x0a
 	CodeMsg            = 0x0b
 	SendTxMsg          = 0x0c
 	GetHeaderProofsMsg = 0x0d
 	HeaderProofsMsg    = 0x0e
+	// Protocol messages belonging to LPV2
+	GetProofsV2Msg         = 0x0f
+	ProofsV2Msg            = 0x10
+	GetHelperTrieProofsMsg = 0x11
+	HelperTrieProofsMsg    = 0x12
+	SendTxV2Msg            = 0x13
+	GetTxStatusMsg         = 0x14
+	TxStatusMsg            = 0x15
 )
 
 type errCode int
@@ -79,7 +97,7 @@ const (
 	ErrUnexpectedResponse
 	ErrInvalidResponse
 	ErrTooManyTimeouts
-	ErrHandshakeMissingKey
+	ErrMissingKey
 )
 
 func (e errCode) String() string {
@@ -101,7 +119,13 @@ var errorToString = map[int]string{
 	ErrUnexpectedResponse:      "Unexpected response",
 	ErrInvalidResponse:         "Invalid response",
 	ErrTooManyTimeouts:         "Too many request timeouts",
-	ErrHandshakeMissingKey:     "Key missing from handshake message",
+	ErrMissingKey:              "Key missing from list",
+}
+
+type announceBlock struct {
+	Hash   common.Hash // Hash of one particular block being announced
+	Number uint64      // Number of one particular block being announced
+	Td     *big.Int    // Total difficulty of one particular block being announced
 }
 
 // announceData is the network packet for the block announcements.
@@ -113,6 +137,32 @@ type announceData struct {
 	Update     keyValueList
 }
 
+// sign adds a signature to the block announcement by the given privKey
+func (a *announceData) sign(privKey *ecdsa.PrivateKey) {
+	rlp, _ := rlp.EncodeToBytes(announceBlock{a.Hash, a.Number, a.Td})
+	sig, _ := crypto.Sign(crypto.Keccak256(rlp), privKey)
+	a.Update = a.Update.add("sign", sig)
+}
+
+// checkSignature verifies if the block announcement has a valid signature by the given pubKey
+func (a *announceData) checkSignature(pubKey *ecdsa.PublicKey) error {
+	var sig []byte
+	if err := a.Update.decode().get("sign", &sig); err != nil {
+		return err
+	}
+	rlp, _ := rlp.EncodeToBytes(announceBlock{a.Hash, a.Number, a.Td})
+	recPubkey, err := secp256k1.RecoverPubkey(crypto.Keccak256(rlp), sig)
+	if err != nil {
+		return err
+	}
+	pbytes := elliptic.Marshal(pubKey.Curve, pubKey.X, pubKey.Y)
+	if bytes.Equal(pbytes, recPubkey) {
+		return nil
+	} else {
+		return errors.New("Wrong signature")
+	}
+}
+
 type blockInfo struct {
 	Hash   common.Hash // Hash of one particular block being announced
 	Number uint64      // Number of one particular block being announced