Catchup: NetworkFetcher service to export fetchBlock

catchup/networkFetcher.go

@@ -35,54 +35,56 @@ type NetworkFetcher struct {
 	log          logging.Logger
 	net          network.GossipNode
 	cfg          config.Local
+	auth         BlockAuthenticator
 	peerSelector *peerSelector
 }
 
 // MakeNetworkFetcher initializes a NetworkFetcher service
-func MakeNetworkFetcher(log logging.Logger, net network.GossipNode, cfg config.Local, pipelineFetch bool) *NetworkFetcher {
+func MakeNetworkFetcher(log logging.Logger, net network.GossipNode, cfg config.Local, auth BlockAuthenticator, pipelineFetch bool) *NetworkFetcher {
 	netFetcher := &NetworkFetcher{
 		log:          log,
 		net:          net,
 		cfg:          cfg,
+		auth:         auth,
 		peerSelector: createPeerSelector(net, cfg, pipelineFetch),
 	}
 	return netFetcher
 }
 
-func (netFetcher *NetworkFetcher) getHTTPPeer(count int) (network.HTTPPeer, *peerSelectorPeer, int, error) {
-	for retryCount := count; retryCount < netFetcher.cfg.CatchupBlockDownloadRetryAttempts; retryCount++ {
+func (netFetcher *NetworkFetcher) getHTTPPeer() (network.HTTPPeer, *peerSelectorPeer, error) {
+	for retryCount := 0; retryCount < netFetcher.cfg.CatchupBlockDownloadRetryAttempts; retryCount++ {
 		psp, err := netFetcher.peerSelector.getNextPeer()
 		if err != nil {
 			if err != errPeerSelectorNoPeerPoolsAvailable {
 				err = fmt.Errorf("FetchBlock: unable to obtain a list of peers to download the block from : %w", err)
-				return nil, nil, retryCount, err
+				return nil, nil, err
 			}
 			// this is a possible on startup, since the network package might have yet to retrieve the list of peers.
 			netFetcher.log.Infof("FetchBlock: unable to obtain a list of peers to download the block from; will retry shortly.")
 			time.Sleep(noPeersAvailableSleepInterval)
-		} else {
-			peer := psp.Peer
-			httpPeer, ok := peer.(network.HTTPPeer)
-			if ok {
-				return httpPeer, psp, retryCount, nil
-			}
-			netFetcher.log.Warnf("FetchBlock: non-HTTP peer was provided by the peer selector")
-			netFetcher.peerSelector.rankPeer(psp, peerRankInvalidDownload)
+			continue
 		}
+		peer := psp.Peer
+		httpPeer, ok := peer.(network.HTTPPeer)
+		if ok {
+			return httpPeer, psp, nil
+		}
+		netFetcher.log.Warnf("FetchBlock: non-HTTP peer was provided by the peer selector")
+		netFetcher.peerSelector.rankPeer(psp, peerRankInvalidDownload)
 	}
-	return nil, nil, netFetcher.cfg.CatchupBlockDownloadRetryAttempts, errors.New("FetchBlock: recurring non-HTTP peer was provided by the peer selector")
+	return nil, nil, errors.New("FetchBlock: recurring non-HTTP peer was provided by the peer selector")
 }
 
 // FetchBlock function given a round number returns a block from a http peer
 func (netFetcher *NetworkFetcher) FetchBlock(ctx context.Context, round basics.Round) (*bookkeeping.Block,
 	*agreement.Certificate, time.Duration, error) {
 	// internal retry attempt to fetch the block
 	for retryCount := 0; retryCount < netFetcher.cfg.CatchupBlockDownloadRetryAttempts; retryCount++ {
-		// keep retrying until a valid http peer is selected by the peerSelector
-		httpPeer, psp, retryCount, err := netFetcher.getHTTPPeer(retryCount)
+		httpPeer, psp, err := netFetcher.getHTTPPeer()
 		if err != nil {
 			return nil, nil, time.Duration(0), err
 		}
+
 		fetcher := makeUniversalBlockFetcher(netFetcher.log, netFetcher.net, netFetcher.cfg)
 		blk, cert, downloadDuration, err := fetcher.fetchBlock(ctx, round, httpPeer)
 		if err != nil {
@@ -92,20 +94,36 @@ func (netFetcher *NetworkFetcher) FetchBlock(ctx context.Context, round basics.R
 			}
 			netFetcher.log.Infof("FetchBlock: failed to download block %d on attempt %d out of %d. %v", round, retryCount, netFetcher.cfg.CatchupBlockDownloadRetryAttempts, err)
 			netFetcher.peerSelector.rankPeer(psp, peerRankDownloadFailed)
-		} else if !blk.ContentsMatchHeader() && blk.Round() > 0 {
+			continue // retry the fetch
+		}
+
+		// Check that the block's contents match the block header
+		if !blk.ContentsMatchHeader() && blk.Round() > 0 {
 			netFetcher.peerSelector.rankPeer(psp, peerRankInvalidDownload)
 			// Check if this mismatch is due to an unsupported protocol version
 			if _, ok := config.Consensus[blk.BlockHeader.CurrentProtocol]; !ok {
 				netFetcher.log.Errorf("FetchBlock: downloaded block(%v) unsupported protocol version detected: '%v'", round, blk.BlockHeader.CurrentProtocol)
 			}
 			netFetcher.log.Warnf("FetchBlock: downloaded block(%v) contents do not match header", round)
 			netFetcher.log.Infof("FetchBlock: failed to download block %d on attempt %d out of %d. %v", round, retryCount, netFetcher.cfg.CatchupBlockDownloadRetryAttempts, err)
-		} else {
-			// upon successful download rank the peer according to the download speed
-			peerRank := netFetcher.peerSelector.peerDownloadDurationToRank(psp, downloadDuration)
-			netFetcher.peerSelector.rankPeer(psp, peerRank)
-			return blk, cert, downloadDuration, err
+			continue // retry the fetch
+		}
+
+		// Authenticate the block. for correct execution, caller should call FetchBlock only when the lookback block is available
+		if netFetcher.cfg.CatchupVerifyCertificate() {
+			err = netFetcher.auth.Authenticate(blk, cert)
+			if err != nil {
+				netFetcher.log.Warnf("FetchBlock: cert did not authenticate block %d on attempt %d out of %d. %v", round, retryCount, netFetcher.cfg.CatchupBlockDownloadRetryAttempts, err)
+				netFetcher.peerSelector.rankPeer(psp, peerRankInvalidDownload)
+				continue // retry the fetch
+			}
 		}
+
+		// upon successful download rank the peer according to the download speed
+		peerRank := netFetcher.peerSelector.peerDownloadDurationToRank(psp, downloadDuration)
+		netFetcher.peerSelector.rankPeer(psp, peerRank)
+		return blk, cert, downloadDuration, err
+
 	}
 	err := fmt.Errorf("FetchBlock failed after multiple blocks download attempts: %v unsuccessful attempts", netFetcher.cfg.CatchupBlockDownloadRetryAttempts)
 	return nil, nil, time.Duration(0), err

catchup/networkFetcher_test.go

@@ -56,7 +56,9 @@ func TestFetchBlock(t *testing.T) {
 
 	net.addPeer(rootURL)
 
-	fetcher := MakeNetworkFetcher(logging.TestingLog(t), net, cfg, false)
+	// Disable block authentication
+	cfg.CatchupBlockValidateMode = 1
+	fetcher := MakeNetworkFetcher(logging.TestingLog(t), net, cfg, nil, false)
 
 	var block *bookkeeping.Block
 	var cert *agreement.Certificate