path: root/les/odr.go

// Copyright 2016 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 les

import (
    "crypto/rand"
    "encoding/binary"
    "sync"
    "time"

    "github.com/ethereum/go-ethereum/common/mclock"
    "github.com/ethereum/go-ethereum/ethdb"
    "github.com/ethereum/go-ethereum/light"
    "github.com/ethereum/go-ethereum/logger"
    "github.com/ethereum/go-ethereum/logger/glog"
    "golang.org/x/net/context"
)

var (
    softRequestTimeout = time.Millisecond * 500
    hardRequestTimeout = time.Second * 10
    retryPeers         = time.Second * 1
)

// peerDropFn is a callback type for dropping a peer detected as malicious.
type peerDropFn func(id string)

type odrPeerSelector interface {
    selectPeer(func(*peer) (bool, uint64)) *peer
    adjustResponseTime(*poolEntry, time.Duration, bool)
}

type LesOdr struct {
    light.OdrBackend
    db           ethdb.Database
    stop         chan struct{}
    removePeer   peerDropFn
    mlock, clock sync.Mutex
    sentReqs     map[uint64]*sentReq
    serverPool   odrPeerSelector
}

func NewLesOdr(db ethdb.Database) *LesOdr {
    return &LesOdr{
        db:       db,
        stop:     make(chan struct{}),
        sentReqs: make(map[uint64]*sentReq),
    }
}

func (odr *LesOdr) Stop() {
    close(odr.stop)
}

func (odr *LesOdr) Database() ethdb.Database {
    return odr.db
}

// validatorFunc is a function that processes a message and returns true if
// it was a meaningful answer to a given request
type validatorFunc func(ethdb.Database, *Msg) bool

// sentReq is a request waiting for an answer that satisfies its valFunc
type sentReq struct {
    valFunc  validatorFunc
    sentTo   map[*peer]chan struct{}
    lock     sync.RWMutex  // protects acces to sentTo
    answered chan struct{} // closed and set to nil when any peer answers it
}

const (
    MsgBlockBodies = iota
    MsgCode
    MsgReceipts
    MsgProofs
    MsgHeaderProofs
)

// Msg encodes a LES message that delivers reply data for a request
type Msg struct {
    MsgType int
    ReqID   uint64
    Obj     interface{}
}

// Deliver is called by the LES protocol manager to deliver ODR reply messages to waiting requests
func (self *LesOdr) Deliver(peer *peer, msg *Msg) error {
    var delivered chan struct{}
    self.mlock.Lock()
    req, ok := self.sentReqs[msg.ReqID]
    self.mlock.Unlock()
    if ok {
        req.lock.Lock()
        delivered, ok = req.sentTo[peer]
        req.lock.Unlock()
    }

    if !ok {
        return errResp(ErrUnexpectedResponse, "reqID = %v", msg.ReqID)
    }

    if req.valFunc(self.db, msg) {
        close(delivered)
        req.lock.Lock()
        if req.answered != nil {
            close(req.answered)
            req.answered = nil
        }
        req.lock.Unlock()
        return nil
    }
    return errResp(ErrInvalidResponse, "reqID = %v", msg.ReqID)
}

func (self *LesOdr) requestPeer(req *sentReq, peer *peer, delivered, timeout chan struct{}, reqWg *sync.WaitGroup) {
    stime := mclock.Now()
    defer func() {
        req.lock.Lock()
        delete(req.sentTo, peer)
        req.lock.Unlock()
        reqWg.Done()
    }()

    select {
    case <-delivered:
        if self.serverPool != nil {
            self.serverPool.adjustResponseTime(peer.poolEntry, time.Duration(mclock.Now()-stime), false)
        }
        return
    case <-time.After(softRequestTimeout):
        close(timeout)
    case <-self.stop:
        return
    }

    select {
    case <-delivered:
    case <-time.After(hardRequestTimeout):
        go self.removePeer(peer.id)
    case <-self.stop:
        return
    }
    if self.serverPool != nil {
        self.serverPool.adjustResponseTime(peer.poolEntry, time.Duration(mclock.Now()-stime), true)
    }
}

// networkRequest sends a request to known peers until an answer is received
// or the context is cancelled
func (self *LesOdr) networkRequest(ctx context.Context, lreq LesOdrRequest) error {
    answered := make(chan struct{})
    req := &sentReq{
        valFunc:  lreq.Valid,
        sentTo:   make(map[*peer]chan struct{}),
        answered: answered, // reply delivered by any peer
    }
    reqID := getNextReqID()
    self.mlock.Lock()
    self.sentReqs[reqID] = req
    self.mlock.Unlock()

    reqWg := new(sync.WaitGroup)
    reqWg.Add(1)
    defer reqWg.Done()
    go func() {
        reqWg.Wait()
        self.mlock.Lock()
        delete(self.sentReqs, reqID)
        self.mlock.Unlock()
    }()

    exclude := make(map[*peer]struct{})
    for {
        var p *peer
        if self.serverPool != nil {
            p = self.serverPool.selectPeer(func(p *peer) (bool, uint64) {
                if !lreq.CanSend(p) {
                    return false, 0
                }
                return true, p.fcServer.CanSend(lreq.GetCost(p))
            })
        }
        if p == nil {
            select {
            case <-ctx.Done():
                return ctx.Err()
            case <-req.answered:
                return nil
            case <-time.After(retryPeers):
            }
        } else {
            exclude[p] = struct{}{}
            delivered := make(chan struct{})
            timeout := make(chan struct{})
            req.lock.Lock()
            req.sentTo[p] = delivered
            req.lock.Unlock()
            reqWg.Add(1)
            cost := lreq.GetCost(p)
            p.fcServer.SendRequest(reqID, cost)
            go self.requestPeer(req, p, delivered, timeout, reqWg)
            lreq.Request(reqID, p)

            select {
            case <-ctx.Done():
                return ctx.Err()
            case <-answered:
                return nil
            case <-timeout:
            }
        }
    }
}

// Retrieve tries to fetch an object from the local db, then from the LES network.
// If the network retrieval was successful, it stores the object in local db.
func (self *LesOdr) Retrieve(ctx context.Context, req light.OdrRequest) (err error) {
    lreq := LesRequest(req)
    err = self.networkRequest(ctx, lreq)
    if err == nil {
        // retrieved from network, store in db
        req.StoreResult(self.db)
    } else {
        glog.V(logger.Debug).Infof("networkRequest  err = %v", err)
    }
    return
}

func getNextReqID() uint64 {
    var rnd [8]byte
    rand.Read(rnd[:])
    return binary.BigEndian.Uint64(rnd[:])
}