Merge pull request #2146 from fjl/discover-win32-large-packets

p2p/discover: fix Windows-specific issue for larger-than-buffer packets

p2p/discover/udp.go

@@ -453,8 +453,11 @@ func encodePacket(priv *ecdsa.PrivateKey, ptype byte, req interface{}) ([]byte,
 	return packet, nil
 }
 
-type tempError interface {
-	Temporary() bool
+func isTemporaryError(err error) bool {
+	tempErr, ok := err.(interface {
+		Temporary() bool
+	})
+	return ok && tempErr.Temporary() || isPacketTooBig(err)
 }
 
 // readLoop runs in its own goroutine. it handles incoming UDP packets.
@@ -466,7 +469,7 @@ func (t *udp) readLoop() {
 	buf := make([]byte, 1280)
 	for {
 		nbytes, from, err := t.conn.ReadFromUDP(buf)
-		if tempErr, ok := err.(tempError); ok && tempErr.Temporary() {
+		if isTemporaryError(err) {
 			// Ignore temporary read errors.
 			glog.V(logger.Debug).Infof("Temporary read error: %v", err)
 			continue

p2p/discover/udp_notwindows.go

@@ -0,0 +1,26 @@
+// Copyright 2016 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/>.
+
+//+build !windows
+
+package discover
+
+// reports whether err indicates that a UDP packet didn't
+// fit the receive buffer. There is no such error on
+// non-Windows platforms.
+func isPacketTooBig(err error) bool {
+	return false
+}

p2p/discover/udp_test.go

@@ -23,10 +23,8 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	logpkg "log"
 	"math/rand"
 	"net"
-	"os"
 	"path/filepath"
 	"reflect"
 	"runtime"
@@ -34,12 +32,62 @@ import (
 	"testing"
 	"time"
 
+	"github.com/davecgh/go-spew/spew"
 	"github.com/ethereum/go-ethereum/crypto"
-	"github.com/ethereum/go-ethereum/logger"
 )
 
 func init() {
-	logger.AddLogSystem(logger.NewStdLogSystem(os.Stdout, logpkg.LstdFlags, logger.ErrorLevel))
+	spew.Config.DisableMethods = true
+}
+
+// This test checks that isPacketTooBig correctly identifies
+// errors that result from receiving a UDP packet larger
+// than the supplied receive buffer.
+func TestIsPacketTooBig(t *testing.T) {
+	listener, err := net.ListenPacket("udp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer listener.Close()
+	sender, err := net.Dial("udp", listener.LocalAddr().String())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer sender.Close()
+
+	sendN := 1800
+	recvN := 300
+	for i := 0; i < 20; i++ {
+		go func() {
+			buf := make([]byte, sendN)
+			for i := range buf {
+				buf[i] = byte(i)
+			}
+			sender.Write(buf)
+		}()
+
+		buf := make([]byte, recvN)
+		listener.SetDeadline(time.Now().Add(1 * time.Second))
+		n, _, err := listener.ReadFrom(buf)
+		if err != nil {
+			if nerr, ok := err.(net.Error); ok && nerr.Timeout() {
+				continue
+			}
+			if !isPacketTooBig(err) {
+				t.Fatal("unexpected read error:", spew.Sdump(err))
+			}
+			continue
+		}
+		if n != recvN {
+			t.Fatalf("short read: %d, want %d", n, recvN)
+		}
+		for i := range buf {
+			if buf[i] != byte(i) {
+				t.Fatalf("error in pattern")
+				break
+			}
+		}
+	}
 }
 
 // shared test variables

p2p/discover/udp_windows.go

@@ -0,0 +1,40 @@
+// Copyright 2016 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/>.
+
+//+build windows
+
+package discover
+
+import (
+	"net"
+	"os"
+	"syscall"
+)
+
+const _WSAEMSGSIZE = syscall.Errno(10040)
+
+// reports whether err indicates that a UDP packet didn't
+// fit the receive buffer. On Windows, WSARecvFrom returns
+// code WSAEMSGSIZE and no data if this happens.
+func isPacketTooBig(err error) bool {
+	if opErr, ok := err.(*net.OpError); ok {
+		if scErr, ok := opErr.Err.(*os.SyscallError); ok {
+			return scErr.Err == _WSAEMSGSIZE
+		}
+		return opErr.Err == _WSAEMSGSIZE
+	}
+	return false
+}