Return Genesis Block (#5709)

* add check
* lint
* lint
* Merge branch 'master' into returnGenesis
* Merge refs/heads/master into returnGenesis
* Merge refs/heads/master into returnGenesis
* Merge refs/heads/master into returnGenesis
* Merge refs/heads/master into returnGenesis
* Merge refs/heads/master into returnGenesis
* terence's review
* Merge branch 'returnGenesis' of https://github.com/prysmaticlabs/geth-sharding into returnGenesis
* Merge refs/heads/master into returnGenesis
* Merge refs/heads/master into returnGenesis
* fix failing test

beacon-chain/sync/BUILD.bazel

@@ -55,6 +55,7 @@ go_library(
         "//beacon-chain/p2p/encoder:go_default_library",
         "//beacon-chain/state:go_default_library",
         "//beacon-chain/state/stategen:go_default_library",
+        "//beacon-chain/state/stateutil:go_default_library",
         "//proto/beacon/p2p/v1:go_default_library",
         "//shared:go_default_library",
         "//shared/attestationutil:go_default_library",
@@ -132,6 +133,7 @@ go_test(
         "//beacon-chain/p2p/testing:go_default_library",
         "//beacon-chain/state:go_default_library",
         "//beacon-chain/state/stategen:go_default_library",
+        "//beacon-chain/state/stateutil:go_default_library",
         "//beacon-chain/sync/initial-sync/testing:go_default_library",
         "//proto/beacon/p2p/v1:go_default_library",
         "//proto/testing:go_default_library",

beacon-chain/sync/rpc_beacon_blocks_by_range.go

@@ -6,8 +6,10 @@ import (
 
 	libp2pcore "github.com/libp2p/go-libp2p-core"
 	"github.com/pkg/errors"
+	ethpb "github.com/prysmaticlabs/ethereumapis/eth/v1alpha1"
 	"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
 	"github.com/prysmaticlabs/prysm/beacon-chain/db/filters"
+	"github.com/prysmaticlabs/prysm/beacon-chain/state/stateutil"
 	pb "github.com/prysmaticlabs/prysm/proto/beacon/p2p/v1"
 	"github.com/prysmaticlabs/prysm/shared/traceutil"
 	"go.opencensus.io/trace"
@@ -124,6 +126,18 @@ func (r *Service) writeBlockRangeToStream(ctx context.Context, startSlot, endSlo
 		traceutil.AnnotateError(span, err)
 		return err
 	}
+	// handle genesis case
+	if startSlot == 0 {
+		genBlock, genRoot, err := r.retrieveGenesisBlock(ctx)
+		if err != nil {
+			log.WithError(err).Error("Failed to retrieve genesis block")
+			r.writeErrorResponseToStream(responseCodeServerError, genericError, stream)
+			traceutil.AnnotateError(span, err)
+			return err
+		}
+		blks = append([]*ethpb.SignedBeaconBlock{genBlock}, blks...)
+		roots = append([][32]byte{genRoot}, roots...)
+	}
 	checkpoint, err := r.db.FinalizedCheckpoint(ctx)
 	if err != nil {
 		log.WithError(err).Error("Failed to retrieve finalized checkpoint")
@@ -159,3 +173,15 @@ func (r *Service) writeErrorResponseToStream(responseCode byte, reason string, s
 		}
 	}
 }
+
+func (r *Service) retrieveGenesisBlock(ctx context.Context) (*ethpb.SignedBeaconBlock, [32]byte, error) {
+	genBlock, err := r.db.GenesisBlock(ctx)
+	if err != nil {
+		return nil, [32]byte{}, err
+	}
+	genRoot, err := stateutil.BlockRoot(genBlock.Block)
+	if err != nil {
+		return nil, [32]byte{}, err
+	}
+	return genBlock, genRoot, nil
+}

beacon-chain/sync/rpc_beacon_blocks_by_range_test.go

@@ -12,6 +12,7 @@ import (
 	ethpb "github.com/prysmaticlabs/ethereumapis/eth/v1alpha1"
 	db "github.com/prysmaticlabs/prysm/beacon-chain/db/testing"
 	p2ptest "github.com/prysmaticlabs/prysm/beacon-chain/p2p/testing"
+	"github.com/prysmaticlabs/prysm/beacon-chain/state/stateutil"
 	pb "github.com/prysmaticlabs/prysm/proto/beacon/p2p/v1"
 	"github.com/prysmaticlabs/prysm/shared/testutil"
 )
@@ -71,3 +72,75 @@ func TestBeaconBlocksRPCHandler_ReturnsBlocks(t *testing.T) {
 		t.Fatal("Did not receive stream within 1 sec")
 	}
 }
+
+func TestBeaconBlocksRPCHandler_ReturnsGenesisBlock(t *testing.T) {
+	p1 := p2ptest.NewTestP2P(t)
+	p2 := p2ptest.NewTestP2P(t)
+	p1.Connect(p2)
+	if len(p1.Host.Network().Peers()) != 1 {
+		t.Error("Expected peers to be connected")
+	}
+	d := db.SetupDB(t)
+
+	req := &pb.BeaconBlocksByRangeRequest{
+		StartSlot: 0,
+		Step:      1,
+		Count:     4,
+	}
+
+	// Populate the database with blocks that would match the request.
+	for i := req.StartSlot; i < req.StartSlot+(req.Step*req.Count); i++ {
+		// Save genesis block
+		if i == 0 {
+			rt, err := stateutil.BlockRoot(&ethpb.BeaconBlock{Slot: i})
+			if err != nil {
+				t.Fatal(err)
+			}
+			if err := d.SaveGenesisBlockRoot(context.Background(), rt); err != nil {
+				t.Fatal(err)
+			}
+		}
+		if err := d.SaveBlock(context.Background(), &ethpb.SignedBeaconBlock{Block: &ethpb.BeaconBlock{Slot: i}}); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	r := &Service{p2p: p1, db: d, blocksRateLimiter: leakybucket.NewCollector(10000, 10000, false)}
+	pcl := protocol.ID("/testing")
+
+	var wg sync.WaitGroup
+	wg.Add(1)
+	p2.Host.SetStreamHandler(pcl, func(stream network.Stream) {
+		defer wg.Done()
+		// check for genesis block
+		expectSuccess(t, r, stream)
+		res := &ethpb.SignedBeaconBlock{}
+		if err := r.p2p.Encoding().DecodeWithLength(stream, res); err != nil {
+			t.Error(err)
+		}
+		if res.Block.Slot != 0 {
+			t.Fatal("genesis block was not returned")
+		}
+		for i := req.StartSlot + req.Step; i < req.Count*req.Step; i += req.Step {
+			expectSuccess(t, r, stream)
+			res := &ethpb.SignedBeaconBlock{}
+			if err := r.p2p.Encoding().DecodeWithLength(stream, res); err != nil {
+				t.Error(err)
+			}
+		}
+	})
+
+	stream1, err := p1.Host.NewStream(context.Background(), p2.Host.ID(), pcl)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = r.beaconBlocksByRangeRPCHandler(context.Background(), req, stream1)
+	if err != nil {
+		t.Errorf("Unexpected error: %v", err)
+	}
+
+	if testutil.WaitTimeout(&wg, 1*time.Second) {
+		t.Fatal("Did not receive stream within 1 sec")
+	}
+}