les: light client protocol and API

1 files changed, 247 insertions, 0 deletions

diff --git a/les/odr.go b/les/odr.go
new file mode 100644
index 000000000..2674ba6a1
--- /dev/null
+++ b/les/odr.go
@@ -0,0 +1,247 @@
+// Copyright 2015 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 (
+	"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 LesOdr struct {
+	light.OdrBackend
+	db           ethdb.Database
+	stop         chan struct{}
+	removePeer   peerDropFn
+	mlock, clock sync.Mutex
+	sentReqs     map[uint64]*sentReq
+	peers        *odrPeerSet
+	lastReqID    uint64
+}
+
+func NewLesOdr(db ethdb.Database) *LesOdr {
+	return &LesOdr{
+		db:       db,
+		stop:     make(chan struct{}),
+		peers:    newOdrPeerSet(),
+		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
+}
+
+// RegisterPeer registers a new LES peer to the ODR capable peer set
+func (self *LesOdr) RegisterPeer(p *peer) error {
+	return self.peers.register(p)
+}
+
+// UnregisterPeer removes a peer from the ODR capable peer set
+func (self *LesOdr) UnregisterPeer(p *peer) {
+	self.peers.unregister(p)
+}
+
+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:
+		servTime := uint64(mclock.Now() - stime)
+		self.peers.updateTimeout(peer, false)
+		self.peers.updateServTime(peer, servTime)
+		return
+	case <-time.After(softRequestTimeout):
+		close(timeout)
+		if self.peers.updateTimeout(peer, true) {
+			self.removePeer(peer.id)
+		}
+	case <-self.stop:
+		return
+	}
+
+	select {
+	case <-delivered:
+		servTime := uint64(mclock.Now() - stime)
+		self.peers.updateServTime(peer, servTime)
+		return
+	case <-time.After(hardRequestTimeout):
+		self.removePeer(peer.id)
+	case <-self.stop:
+		return
+	}
+}
+
+// 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 := self.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 {
+		if peer := self.peers.bestPeer(lreq, exclude); peer == nil {
+			select {
+			case <-ctx.Done():
+				return ctx.Err()
+			case <-req.answered:
+				return nil
+			case <-time.After(retryPeers):
+			}
+		} else {
+			exclude[peer] = struct{}{}
+			delivered := make(chan struct{})
+			timeout := make(chan struct{})
+			req.lock.Lock()
+			req.sentTo[peer] = delivered
+			req.lock.Unlock()
+			reqWg.Add(1)
+			cost := lreq.GetCost(peer)
+			peer.fcServer.SendRequest(reqID, cost)
+			go self.requestPeer(req, peer, delivered, timeout, reqWg)
+			lreq.Request(reqID, peer)
+
+			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 (self *LesOdr) getNextReqID() uint64 {
+	self.clock.Lock()
+	defer self.clock.Unlock()
+
+	self.lastReqID++
+	return self.lastReqID
+}