path: root/eth/protocol.go

package eth

import (
    "bytes"
    "fmt"
    "io"
    "math/big"

    "github.com/ethereum/go-ethereum/core/types"
    "github.com/ethereum/go-ethereum/ethutil"
    "github.com/ethereum/go-ethereum/p2p"
    "github.com/ethereum/go-ethereum/rlp"
)

const (
    ProtocolVersion    = 51
    NetworkId          = 0
    ProtocolLength     = uint64(8)
    ProtocolMaxMsgSize = 10 * 1024 * 1024
)

// eth protocol message codes
const (
    StatusMsg = iota
    GetTxMsg  // unused
    TxMsg
    GetBlockHashesMsg
    BlockHashesMsg
    GetBlocksMsg
    BlocksMsg
    NewBlockMsg
)

// ethProtocol represents the ethereum wire protocol
// instance is running on each peer
type ethProtocol struct {
    txPool       txPool
    chainManager chainManager
    blockPool    blockPool
    peer         *p2p.Peer
    id           string
    rw           p2p.MsgReadWriter
}

// backend is the interface the ethereum protocol backend should implement
// used as an argument to EthProtocol
type txPool interface {
    AddTransactions([]*types.Transaction)
}

type chainManager interface {
    GetBlockHashesFromHash(hash []byte, amount uint64) (hashes [][]byte)
    GetBlock(hash []byte) (block *types.Block)
    Status() (td *big.Int, currentBlock []byte, genesisBlock []byte)
}

type blockPool interface {
    AddBlockHashes(next func() ([]byte, bool), peerId string)
    AddBlock(block *types.Block, peerId string)
    AddPeer(td *big.Int, currentBlock []byte, peerId string, requestHashes func([]byte) error, requestBlocks func([][]byte) error, peerError func(int, string, ...interface{})) (best bool)
    RemovePeer(peerId string)
}

// message structs used for rlp decoding
type newBlockMsgData struct {
    Block *types.Block
    TD    *big.Int
}

type getBlockHashesMsgData struct {
    Hash   []byte
    Amount uint64
}

// main entrypoint, wrappers starting a server running the eth protocol
// use this constructor to attach the protocol ("class") to server caps
// the Dev p2p layer then runs the protocol instance on each peer
func EthProtocol(txPool txPool, chainManager chainManager, blockPool blockPool) p2p.Protocol {
    return p2p.Protocol{
        Name:    "eth",
        Version: ProtocolVersion,
        Length:  ProtocolLength,
        Run: func(peer *p2p.Peer, rw p2p.MsgReadWriter) error {
            return runEthProtocol(txPool, chainManager, blockPool, peer, rw)
        },
    }
}

// the main loop that handles incoming messages
// note RemovePeer in the post-disconnect hook
func runEthProtocol(txPool txPool, chainManager chainManager, blockPool blockPool, peer *p2p.Peer, rw p2p.MsgReadWriter) (err error) {
    self := &ethProtocol{
        txPool:       txPool,
        chainManager: chainManager,
        blockPool:    blockPool,
        rw:           rw,
        peer:         peer,
        id:           fmt.Sprintf("%x", peer.Identity().Pubkey()[:8]),
    }
    err = self.handleStatus()
    if err == nil {
        for {
            err = self.handle()
            if err != nil {
                self.blockPool.RemovePeer(self.id)
                break
            }
        }
    }
    return
}

func (self *ethProtocol) handle() error {
    msg, err := self.rw.ReadMsg()
    if err != nil {
        return err
    }
    if msg.Size > ProtocolMaxMsgSize {
        return self.protoError(ErrMsgTooLarge, "%v > %v", msg.Size, ProtocolMaxMsgSize)
    }
    // make sure that the payload has been fully consumed
    defer msg.Discard()

    switch msg.Code {

    case StatusMsg:
        return self.protoError(ErrExtraStatusMsg, "")

    case TxMsg:
        // TODO: rework using lazy RLP stream
        var txs []*types.Transaction
        if err := msg.Decode(&txs); err != nil {
            return self.protoError(ErrDecode, "msg %v: %v", msg, err)
        }
        self.txPool.AddTransactions(txs)

    case GetBlockHashesMsg:
        var request getBlockHashesMsgData
        if err := msg.Decode(&request); err != nil {
            return self.protoError(ErrDecode, "->msg %v: %v", msg, err)
        }
        hashes := self.chainManager.GetBlockHashesFromHash(request.Hash, request.Amount)
        return self.rw.EncodeMsg(BlockHashesMsg, ethutil.ByteSliceToInterface(hashes)...)

    case BlockHashesMsg:
        // TODO: redo using lazy decode , this way very inefficient on known chains
        msgStream := rlp.NewStream(msg.Payload)
        var err error
        var i int

        iter := func() (hash []byte, ok bool) {
            hash, err = msgStream.Bytes()
            if err == nil {
                i++
                ok = true
            } else {
                if err != io.EOF {
                    self.protoError(ErrDecode, "msg %v: after %v hashes : %v", msg, i, err)
                }
            }
            return
        }

        self.blockPool.AddBlockHashes(iter, self.id)

    case GetBlocksMsg:
        msgStream := rlp.NewStream(msg.Payload)
        var blocks []interface{}
        var i int
        for {
            i++
            var hash []byte
            if err := msgStream.Decode(&hash); err != nil {
                if err == io.EOF {
                    break
                } else {
                    return self.protoError(ErrDecode, "msg %v: %v", msg, err)
                }
            }
            block := self.chainManager.GetBlock(hash)
            if block != nil {
                blocks = append(blocks, block)
            }
            if i == blockHashesBatchSize {
                break
            }
        }
        return self.rw.EncodeMsg(BlocksMsg, blocks...)

    case BlocksMsg:
        msgStream := rlp.NewStream(msg.Payload)
        for {
            var block types.Block
            if err := msgStream.Decode(&block); err != nil {
                if err == io.EOF {
                    break
                } else {
                    return self.protoError(ErrDecode, "msg %v: %v", msg, err)
                }
            }
            self.blockPool.AddBlock(&block, self.id)
        }

    case NewBlockMsg:
        var request newBlockMsgData
        if err := msg.Decode(&request); err != nil {
            return self.protoError(ErrDecode, "msg %v: %v", msg, err)
        }
        hash := request.Block.Hash()
        // to simplify backend interface adding a new block
        // uses AddPeer followed by AddHashes, AddBlock only if peer is the best peer
        // (or selected as new best peer)
        if self.blockPool.AddPeer(request.TD, hash, self.id, self.requestBlockHashes, self.requestBlocks, self.protoErrorDisconnect) {
            called := true
            iter := func() ([]byte, bool) {
                if called {
                    called = false
                    return hash, true
                } else {
                    return nil, false
                }
            }
            self.blockPool.AddBlockHashes(iter, self.id)
            self.blockPool.AddBlock(request.Block, self.id)
        }

    default:
        return self.protoError(ErrInvalidMsgCode, "%v", msg.Code)
    }
    return nil
}

type statusMsgData struct {
    ProtocolVersion uint32
    NetworkId       uint32
    TD              *big.Int
    CurrentBlock    []byte
    GenesisBlock    []byte
}

func (self *ethProtocol) statusMsg() p2p.Msg {
    td, currentBlock, genesisBlock := self.chainManager.Status()

    return p2p.NewMsg(StatusMsg,
        uint32(ProtocolVersion),
        uint32(NetworkId),
        td,
        currentBlock,
        genesisBlock,
    )
}

func (self *ethProtocol) handleStatus() error {
    // send precanned status message
    if err := self.rw.WriteMsg(self.statusMsg()); err != nil {
        return err
    }

    // read and handle remote status
    msg, err := self.rw.ReadMsg()
    if err != nil {
        return err
    }

    if msg.Code != StatusMsg {
        return self.protoError(ErrNoStatusMsg, "first msg has code %x (!= %x)", msg.Code, StatusMsg)
    }

    if msg.Size > ProtocolMaxMsgSize {
        return self.protoError(ErrMsgTooLarge, "%v > %v", msg.Size, ProtocolMaxMsgSize)
    }

    var status statusMsgData
    if err := msg.Decode(&status); err != nil {
        return self.protoError(ErrDecode, "msg %v: %v", msg, err)
    }

    _, _, genesisBlock := self.chainManager.Status()

    if bytes.Compare(status.GenesisBlock, genesisBlock) != 0 {
        return self.protoError(ErrGenesisBlockMismatch, "%x (!= %x)", status.GenesisBlock, genesisBlock)
    }

    if status.NetworkId != NetworkId {
        return self.protoError(ErrNetworkIdMismatch, "%d (!= %d)", status.NetworkId, NetworkId)
    }

    if ProtocolVersion != status.ProtocolVersion {
        return self.protoError(ErrProtocolVersionMismatch, "%d (!= %d)", status.ProtocolVersion, ProtocolVersion)
    }

    self.peer.Infof("Peer is [eth] capable (%d/%d). TD=%v H=%x\n", status.ProtocolVersion, status.NetworkId, status.TD, status.CurrentBlock[:4])

    self.blockPool.AddPeer(status.TD, status.CurrentBlock, self.id, self.requestBlockHashes, self.requestBlocks, self.protoErrorDisconnect)

    return nil
}

func (self *ethProtocol) requestBlockHashes(from []byte) error {
    self.peer.Debugf("fetching hashes (%d) %x...\n", blockHashesBatchSize, from[0:4])
    return self.rw.EncodeMsg(GetBlockHashesMsg, interface{}(from), uint64(blockHashesBatchSize))
}

func (self *ethProtocol) requestBlocks(hashes [][]byte) error {
    self.peer.Debugf("fetching %v blocks", len(hashes))
    return self.rw.EncodeMsg(GetBlocksMsg, ethutil.ByteSliceToInterface(hashes)...)
}

func (self *ethProtocol) protoError(code int, format string, params ...interface{}) (err *protocolError) {
    err = ProtocolError(code, format, params...)
    if err.Fatal() {
        self.peer.Errorln("err %v", err)
        // disconnect
    } else {
        self.peer.Debugf("fyi %v", err)
    }
    return
}

func (self *ethProtocol) protoErrorDisconnect(code int, format string, params ...interface{}) {
    err := ProtocolError(code, format, params...)
    if err.Fatal() {
        self.peer.Errorln("err %v", err)
        // disconnect
    } else {
        self.peer.Debugf("fyi %v", err)
    }

}