Merge pull request #204 from fjl/fix-p2p-disconnect

p2p: fix decoding of disconnect reason

7 files changed, 277 insertions, 8 deletions

diff --git a/p2p/message.go b/p2p/message.go
index d3b8b74d4..f5418ff47 100644
--- a/p2p/message.go
+++ b/p2p/message.go
@@ -3,9 +3,11 @@ package p2p
 import (
 	"bytes"
 	"encoding/binary"
+	"errors"
 	"io"
 	"io/ioutil"
 	"math/big"
+	"sync/atomic"
 
 	"github.com/ethereum/go-ethereum/ethutil"
 	"github.com/ethereum/go-ethereum/rlp"
@@ -153,3 +155,78 @@ func (r *postrack) ReadByte() (byte, error) {
 	}
 	return b, err
 }
+
+// MsgPipe creates a message pipe. Reads on one end are matched
+// with writes on the other. The pipe is full-duplex, both ends
+// implement MsgReadWriter.
+func MsgPipe() (*MsgPipeRW, *MsgPipeRW) {
+	var (
+		c1, c2  = make(chan Msg), make(chan Msg)
+		closing = make(chan struct{})
+		closed  = new(int32)
+		rw1     = &MsgPipeRW{c1, c2, closing, closed}
+		rw2     = &MsgPipeRW{c2, c1, closing, closed}
+	)
+	return rw1, rw2
+}
+
+// ErrPipeClosed is returned from pipe operations after the
+// pipe has been closed.
+var ErrPipeClosed = errors.New("p2p: read or write on closed message pipe")
+
+// MsgPipeRW is an endpoint of a MsgReadWriter pipe.
+type MsgPipeRW struct {
+	w       chan<- Msg
+	r       <-chan Msg
+	closing chan struct{}
+	closed  *int32
+}
+
+// WriteMsg sends a messsage on the pipe.
+// It blocks until the receiver has consumed the message payload.
+func (p *MsgPipeRW) WriteMsg(msg Msg) error {
+	if atomic.LoadInt32(p.closed) == 0 {
+		consumed := make(chan struct{}, 1)
+		msg.Payload = &eofSignal{msg.Payload, int64(msg.Size), consumed}
+		select {
+		case p.w <- msg:
+			if msg.Size > 0 {
+				// wait for payload read or discard
+				<-consumed
+			}
+			return nil
+		case <-p.closing:
+		}
+	}
+	return ErrPipeClosed
+}
+
+// EncodeMsg is a convenient shorthand for sending an RLP-encoded message.
+func (p *MsgPipeRW) EncodeMsg(code uint64, data ...interface{}) error {
+	return p.WriteMsg(NewMsg(code, data...))
+}
+
+// ReadMsg returns a message sent on the other end of the pipe.
+func (p *MsgPipeRW) ReadMsg() (Msg, error) {
+	if atomic.LoadInt32(p.closed) == 0 {
+		select {
+		case msg := <-p.r:
+			return msg, nil
+		case <-p.closing:
+		}
+	}
+	return Msg{}, ErrPipeClosed
+}
+
+// Close unblocks any pending ReadMsg and WriteMsg calls on both ends
+// of the pipe. They will return ErrPipeClosed. Note that Close does
+// not interrupt any reads from a message payload.
+func (p *MsgPipeRW) Close() error {
+	if atomic.AddInt32(p.closed, 1) != 1 {
+		// someone else is already closing
+		atomic.StoreInt32(p.closed, 1) // avoid overflow
+		return nil
+	}
+	close(p.closing)
+	return nil
+}
diff --git a/p2p/message_test.go b/p2p/message_test.go
index 557bfed26..066d2516d 100644
--- a/p2p/message_test.go
+++ b/p2p/message_test.go
@@ -2,8 +2,11 @@ package p2p
 
 import (
 	"bytes"
+	"fmt"
 	"io/ioutil"
+	"runtime"
 	"testing"
+	"time"
 
 	"github.com/ethereum/go-ethereum/ethutil"
 )
@@ -68,3 +71,63 @@ func TestDecodeRealMsg(t *testing.T) {
 		t.Errorf("incorrect code %d, want %d", msg.Code, 0)
 	}
 }
+
+func ExampleMsgPipe() {
+	rw1, rw2 := MsgPipe()
+	go func() {
+		rw1.EncodeMsg(8, []byte{0, 0})
+		rw1.EncodeMsg(5, []byte{1, 1})
+		rw1.Close()
+	}()
+
+	for {
+		msg, err := rw2.ReadMsg()
+		if err != nil {
+			break
+		}
+		var data [1][]byte
+		msg.Decode(&data)
+		fmt.Printf("msg: %d, %x\n", msg.Code, data[0])
+	}
+	// Output:
+	// msg: 8, 0000
+	// msg: 5, 0101
+}
+
+func TestMsgPipeUnblockWrite(t *testing.T) {
+loop:
+	for i := 0; i < 100; i++ {
+		rw1, rw2 := MsgPipe()
+		done := make(chan struct{})
+		go func() {
+			if err := rw1.EncodeMsg(1); err == nil {
+				t.Error("EncodeMsg returned nil error")
+			} else if err != ErrPipeClosed {
+				t.Error("EncodeMsg returned wrong error: got %v, want %v", err, ErrPipeClosed)
+			}
+			close(done)
+		}()
+
+		// this call should ensure that EncodeMsg is waiting to
+		// deliver sometimes. if this isn't done, Close is likely to
+		// be executed before EncodeMsg starts and then we won't test
+		// all the cases.
+		runtime.Gosched()
+
+		rw2.Close()
+		select {
+		case <-done:
+		case <-time.After(200 * time.Millisecond):
+			t.Errorf("write didn't unblock")
+			break loop
+		}
+	}
+}
+
+// This test should panic if concurrent close isn't implemented correctly.
+func TestMsgPipeConcurrentClose(t *testing.T) {
+	rw1, _ := MsgPipe()
+	for i := 0; i < 10; i++ {
+		go rw1.Close()
+	}
+}
diff --git a/p2p/peer.go b/p2p/peer.go
index 893ba86d7..86c4d7ab5 100644
--- a/p2p/peer.go
+++ b/p2p/peer.go
@@ -300,7 +300,7 @@ func (p *Peer) dispatch(msg Msg, protoDone chan struct{}) (wait bool, err error)
 		proto.in <- msg
 	} else {
 		wait = true
-		pr := &eofSignal{msg.Payload, protoDone}
+		pr := &eofSignal{msg.Payload, int64(msg.Size), protoDone}
 		msg.Payload = pr
 		proto.in <- msg
 	}
@@ -438,18 +438,25 @@ func (rw *proto) ReadMsg() (Msg, error) {
 	return msg, nil
 }
 
-// eofSignal wraps a reader with eof signaling.
-// the eof channel is closed when the wrapped reader
-// reaches EOF.
+// eofSignal wraps a reader with eof signaling. the eof channel is
+// closed when the wrapped reader returns an error or when count bytes
+// have been read.
+//
 type eofSignal struct {
 	wrapped io.Reader
+	count   int64
 	eof     chan<- struct{}
 }
 
+// note: when using eofSignal to detect whether a message payload
+// has been read, Read might not be called for zero sized messages.
+
 func (r *eofSignal) Read(buf []byte) (int, error) {
 	n, err := r.wrapped.Read(buf)
-	if err != nil {
+	r.count -= int64(n)
+	if (err != nil || r.count <= 0) && r.eof != nil {
 		r.eof <- struct{}{} // tell Peer that msg has been consumed
+		r.eof = nil
 	}
 	return n, err
 }
diff --git a/p2p/peer_error.go b/p2p/peer_error.go
index 88b870fbd..0eb7ec838 100644
--- a/p2p/peer_error.go
+++ b/p2p/peer_error.go
@@ -100,7 +100,16 @@ func (d DiscReason) String() string {
 	return discReasonToString[d]
 }
 
+type discRequestedError DiscReason
+
+func (err discRequestedError) Error() string {
+	return fmt.Sprintf("disconnect requested: %v", DiscReason(err))
+}
+
 func discReasonForError(err error) DiscReason {
+	if reason, ok := err.(discRequestedError); ok {
+		return DiscReason(reason)
+	}
 	peerError, ok := err.(*peerError)
 	if !ok {
 		return DiscSubprotocolError
diff --git a/p2p/peer_test.go b/p2p/peer_test.go
index d9640292f..f7759786e 100644
--- a/p2p/peer_test.go
+++ b/p2p/peer_test.go
@@ -4,6 +4,7 @@ import (
 	"bufio"
 	"bytes"
 	"encoding/hex"
+	"io"
 	"io/ioutil"
 	"net"
 	"reflect"
@@ -237,3 +238,58 @@ func TestNewPeer(t *testing.T) {
 	// Should not hang.
 	p.Disconnect(DiscAlreadyConnected)
 }
+
+func TestEOFSignal(t *testing.T) {
+	rb := make([]byte, 10)
+
+	// empty reader
+	eof := make(chan struct{}, 1)
+	sig := &eofSignal{new(bytes.Buffer), 0, eof}
+	if n, err := sig.Read(rb); n != 0 || err != io.EOF {
+		t.Errorf("Read returned unexpected values: (%v, %v)", n, err)
+	}
+	select {
+	case <-eof:
+	default:
+		t.Error("EOF chan not signaled")
+	}
+
+	// count before error
+	eof = make(chan struct{}, 1)
+	sig = &eofSignal{bytes.NewBufferString("aaaaaaaa"), 4, eof}
+	if n, err := sig.Read(rb); n != 8 || err != nil {
+		t.Errorf("Read returned unexpected values: (%v, %v)", n, err)
+	}
+	select {
+	case <-eof:
+	default:
+		t.Error("EOF chan not signaled")
+	}
+
+	// error before count
+	eof = make(chan struct{}, 1)
+	sig = &eofSignal{bytes.NewBufferString("aaaa"), 999, eof}
+	if n, err := sig.Read(rb); n != 4 || err != nil {
+		t.Errorf("Read returned unexpected values: (%v, %v)", n, err)
+	}
+	if n, err := sig.Read(rb); n != 0 || err != io.EOF {
+		t.Errorf("Read returned unexpected values: (%v, %v)", n, err)
+	}
+	select {
+	case <-eof:
+	default:
+		t.Error("EOF chan not signaled")
+	}
+
+	// no signal if neither occurs
+	eof = make(chan struct{}, 1)
+	sig = &eofSignal{bytes.NewBufferString("aaaaaaaaaaaaaaaaaaaaa"), 999, eof}
+	if n, err := sig.Read(rb); n != 10 || err != nil {
+		t.Errorf("Read returned unexpected values: (%v, %v)", n, err)
+	}
+	select {
+	case <-eof:
+		t.Error("unexpected EOF signal")
+	default:
+	}
+}
diff --git a/p2p/protocol.go b/p2p/protocol.go
index 28eab87cd..3f52205f5 100644
--- a/p2p/protocol.go
+++ b/p2p/protocol.go
@@ -154,12 +154,11 @@ func (bp *baseProtocol) handle(rw MsgReadWriter) error {
 		return newPeerError(errProtocolBreach, "extra handshake received")
 
 	case discMsg:
-		var reason DiscReason
+		var reason [1]DiscReason
 		if err := msg.Decode(&reason); err != nil {
 			return err
 		}
-		bp.peer.Disconnect(reason)
-		return nil
+		return discRequestedError(reason[0])
 
 	case pingMsg:
 		return bp.rw.EncodeMsg(pongMsg)
diff --git a/p2p/protocol_test.go b/p2p/protocol_test.go
new file mode 100644
index 000000000..65f26fb12
--- /dev/null
+++ b/p2p/protocol_test.go
@@ -0,0 +1,58 @@
+package p2p
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestBaseProtocolDisconnect(t *testing.T) {
+	peer := NewPeer(NewSimpleClientIdentity("p1", "", "", "foo"), nil)
+	peer.ourID = NewSimpleClientIdentity("p2", "", "", "bar")
+	peer.pubkeyHook = func(*peerAddr) error { return nil }
+
+	rw1, rw2 := MsgPipe()
+	done := make(chan struct{})
+	go func() {
+		if err := expectMsg(rw2, handshakeMsg); err != nil {
+			t.Error(err)
+		}
+		err := rw2.EncodeMsg(handshakeMsg,
+			baseProtocolVersion,
+			"",
+			[]interface{}{},
+			0,
+			make([]byte, 64),
+		)
+		if err != nil {
+			t.Error(err)
+		}
+		if err := expectMsg(rw2, getPeersMsg); err != nil {
+			t.Error(err)
+		}
+		if err := rw2.EncodeMsg(discMsg, DiscQuitting); err != nil {
+			t.Error(err)
+		}
+		close(done)
+	}()
+
+	if err := runBaseProtocol(peer, rw1); err == nil {
+		t.Errorf("base protocol returned without error")
+	} else if reason, ok := err.(discRequestedError); !ok || reason != DiscQuitting {
+		t.Errorf("base protocol returned wrong error: %v", err)
+	}
+	<-done
+}
+
+func expectMsg(r MsgReader, code uint64) error {
+	msg, err := r.ReadMsg()
+	if err != nil {
+		return err
+	}
+	if err := msg.Discard(); err != nil {
+		return err
+	}
+	if msg.Code != code {
+		return fmt.Errorf("wrong message code: got %d, expected %d", msg.Code, code)
+	}
+	return nil
+}