eth: request id dispatcher and direct req/reply APIs (#23576)

* eth: request ID based message dispatcher

* eth: fix dispatcher cancellation, rework fetchers idleness tracker

* eth/downloader: drop peers who refuse to serve advertised chains

eth/downloader/fetchers.go

@@ -0,0 +1,115 @@
+// Copyright 2021 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 downloader
+
+import (
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/eth/protocols/eth"
+)
+
+// fetchHeadersByHash is a blocking version of Peer.RequestHeadersByHash which
+// handles all the cancellation, interruption and timeout mechanisms of a data
+// retrieval to allow blocking API calls.
+func (d *Downloader) fetchHeadersByHash(p *peerConnection, hash common.Hash, amount int, skip int, reverse bool) ([]*types.Header, error) {
+	// Create the response sink and send the network request
+	start := time.Now()
+	resCh := make(chan *eth.Response)
+
+	req, err := p.peer.RequestHeadersByHash(hash, amount, skip, reverse, resCh)
+	if err != nil {
+		return nil, err
+	}
+	defer req.Close()
+
+	// Wait until the response arrives, the request is cancelled or times out
+	ttl := d.peers.rates.TargetTimeout()
+
+	timeoutTimer := time.NewTimer(ttl)
+	defer timeoutTimer.Stop()
+
+	select {
+	case <-d.cancelCh:
+		return nil, errCanceled
+
+	case <-timeoutTimer.C:
+		// Header retrieval timed out, update the metrics
+		p.log.Debug("Header request timed out", "elapsed", ttl)
+		headerTimeoutMeter.Mark(1)
+
+		return nil, errTimeout
+
+	case res := <-resCh:
+		// Headers successfully retrieved, update the metrics
+		headerReqTimer.Update(time.Since(start))
+		headerInMeter.Mark(int64(len(*res.Res.(*eth.BlockHeadersPacket))))
+
+		// Don't reject the packet even if it turns out to be bad, downloader will
+		// disconnect the peer on its own terms. Simply delivery the headers to
+		// be processed by the caller
+		res.Done <- nil
+
+		return *res.Res.(*eth.BlockHeadersPacket), nil
+	}
+}
+
+// fetchHeadersByNumber is a blocking version of Peer.RequestHeadersByNumber which
+// handles all the cancellation, interruption and timeout mechanisms of a data
+// retrieval to allow blocking API calls.
+func (d *Downloader) fetchHeadersByNumber(p *peerConnection, number uint64, amount int, skip int, reverse bool) ([]*types.Header, error) {
+	// Create the response sink and send the network request
+	start := time.Now()
+	resCh := make(chan *eth.Response)
+
+	req, err := p.peer.RequestHeadersByNumber(number, amount, skip, reverse, resCh)
+	if err != nil {
+		return nil, err
+	}
+	defer req.Close()
+
+	// Wait until the response arrives, the request is cancelled or times out
+	ttl := d.peers.rates.TargetTimeout()
+
+	timeoutTimer := time.NewTimer(ttl)
+	defer timeoutTimer.Stop()
+
+	select {
+	case <-d.cancelCh:
+		return nil, errCanceled
+
+	case <-timeoutTimer.C:
+		// Header retrieval timed out, update the metrics
+		p.log.Debug("Header request timed out", "elapsed", ttl)
+		headerTimeoutMeter.Mark(1)
+
+		return nil, errTimeout
+
+	case res := <-resCh:
+		// Headers successfully retrieved, update the metrics
+		headerReqTimer.Update(time.Since(start))
+		headerInMeter.Mark(int64(len(*res.Res.(*eth.BlockHeadersPacket))))
+
+		// Don't reject the packet even if it turns out to be bad, downloader will
+		// disconnect the peer on its own terms. Simply delivery the headers to
+		// be processed by the caller
+		res.Done <- nil
+
+		return *res.Res.(*eth.BlockHeadersPacket), nil
+	}
+}