Merge pull request ethereum#1924 from fjl/eth-status-timeout

eth: time out status message exchange after 5s

Author: obscuren

eth/peer.go

@@ -21,6 +21,7 @@ import (
 	"fmt"
 	"math/big"
 	"sync"
+	"time"
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/types"
@@ -38,8 +39,9 @@ var (
 )
 
 const (
-	maxKnownTxs    = 32768 // Maximum transactions hashes to keep in the known list (prevent DOS)
-	maxKnownBlocks = 1024  // Maximum block hashes to keep in the known list (prevent DOS)
+	maxKnownTxs      = 32768 // Maximum transactions hashes to keep in the known list (prevent DOS)
+	maxKnownBlocks   = 1024  // Maximum block hashes to keep in the known list (prevent DOS)
+	handshakeTimeout = 5 * time.Second
 )
 
 type peer struct {
@@ -267,8 +269,8 @@ func (p *peer) RequestReceipts(hashes []common.Hash) error {
 // Handshake executes the eth protocol handshake, negotiating version number,
 // network IDs, difficulties, head and genesis blocks.
 func (p *peer) Handshake(td *big.Int, head common.Hash, genesis common.Hash) error {
-	// Send out own handshake in a new thread
-	errc := make(chan error, 1)
+	errc := make(chan error, 2)
+	var status statusData // safe to read after two values have been received from errc
 	go func() {
 		errc <- p2p.Send(p.rw, StatusMsg, &statusData{
 			ProtocolVersion: uint32(p.version),
@@ -278,7 +280,26 @@ func (p *peer) Handshake(td *big.Int, head common.Hash, genesis common.Hash) err
 			GenesisBlock:    genesis,
 		})
 	}()
-	// In the mean time retrieve the remote status message
+	go func() {
+		errc <- p.readStatus(&status, genesis)
+	}()
+	timeout := time.NewTimer(handshakeTimeout)
+	defer timeout.Stop()
+	for i := 0; i < 2; i++ {
+		select {
+		case err := <-errc:
+			if err != nil {
+				return err
+			}
+		case <-timeout.C:
+			return p2p.DiscReadTimeout
+		}
+	}
+	p.td, p.head = status.TD, status.CurrentBlock
+	return nil
+}
+
+func (p *peer) readStatus(status *statusData, genesis common.Hash) (err error) {
 	msg, err := p.rw.ReadMsg()
 	if err != nil {
 		return err
@@ -290,7 +311,6 @@ func (p *peer) Handshake(td *big.Int, head common.Hash, genesis common.Hash) err
 		return errResp(ErrMsgTooLarge, "%v > %v", msg.Size, ProtocolMaxMsgSize)
 	}
 	// Decode the handshake and make sure everything matches
-	var status statusData
 	if err := msg.Decode(&status); err != nil {
 		return errResp(ErrDecode, "msg %v: %v", msg, err)
 	}
@@ -303,9 +323,7 @@ func (p *peer) Handshake(td *big.Int, head common.Hash, genesis common.Hash) err
 	if int(status.ProtocolVersion) != p.version {
 		return errResp(ErrProtocolVersionMismatch, "%d (!= %d)", status.ProtocolVersion, p.version)
 	}
-	// Configure the remote peer, and sanity check out handshake too
-	p.td, p.head = status.TD, status.CurrentBlock
-	return <-errc
+	return nil
 }
 
 // String implements fmt.Stringer.