2 files changed, 120 insertions, 31 deletions

diff --git a/p2p/discover/udp.go b/p2p/discover/udp.go
index d7ca9000d..008e63937 100644
--- a/p2p/discover/udp.go
+++ b/p2p/discover/udp.go
@@ -18,6 +18,7 @@ package discover
 
 import (
 	"bytes"
+	"container/list"
 	"crypto/ecdsa"
 	"errors"
 	"fmt"
@@ -43,6 +44,7 @@ var (
 	errUnsolicitedReply = errors.New("unsolicited reply")
 	errUnknownNode      = errors.New("unknown node")
 	errTimeout          = errors.New("RPC timeout")
+	errClockWarp        = errors.New("reply deadline too far in the future")
 	errClosed           = errors.New("socket closed")
 )
 
@@ -296,7 +298,7 @@ func (t *udp) pending(id NodeID, ptype byte, callback func(interface{}) bool) <-
 }
 
 func (t *udp) handleReply(from NodeID, ptype byte, req packet) bool {
-	matched := make(chan bool)
+	matched := make(chan bool, 1)
 	select {
 	case t.gotreply <- reply{from, ptype, req, matched}:
 		// loop will handle it
@@ -310,68 +312,82 @@ func (t *udp) handleReply(from NodeID, ptype byte, req packet) bool {
 // the refresh timer and the pending reply queue.
 func (t *udp) loop() {
 	var (
-		pending      []*pending
-		nextDeadline time.Time
-		timeout      = time.NewTimer(0)
-		refresh      = time.NewTicker(refreshInterval)
+		plist       = list.New()
+		timeout     = time.NewTimer(0)
+		nextTimeout *pending // head of plist when timeout was last reset
+		refresh     = time.NewTicker(refreshInterval)
 	)
 	<-timeout.C // ignore first timeout
 	defer refresh.Stop()
 	defer timeout.Stop()
 
-	rearmTimeout := func() {
-		now := time.Now()
-		if len(pending) == 0 || now.Before(nextDeadline) {
+	resetTimeout := func() {
+		if plist.Front() == nil || nextTimeout == plist.Front().Value {
 			return
 		}
-		nextDeadline = pending[0].deadline
-		timeout.Reset(nextDeadline.Sub(now))
+		// Start the timer so it fires when the next pending reply has expired.
+		now := time.Now()
+		for el := plist.Front(); el != nil; el = el.Next() {
+			nextTimeout = el.Value.(*pending)
+			if dist := nextTimeout.deadline.Sub(now); dist < 2*respTimeout {
+				timeout.Reset(dist)
+				return
+			}
+			// Remove pending replies whose deadline is too far in the
+			// future. These can occur if the system clock jumped
+			// backwards after the deadline was assigned.
+			nextTimeout.errc <- errClockWarp
+			plist.Remove(el)
+		}
+		nextTimeout = nil
+		timeout.Stop()
 	}
 
 	for {
+		resetTimeout()
+
 		select {
 		case <-refresh.C:
 			go t.refresh()
 
 		case <-t.closing:
-			for _, p := range pending {
-				p.errc <- errClosed
+			for el := plist.Front(); el != nil; el = el.Next() {
+				el.Value.(*pending).errc <- errClosed
 			}
-			pending = nil
 			return
 
 		case p := <-t.addpending:
 			p.deadline = time.Now().Add(respTimeout)
-			pending = append(pending, p)
-			rearmTimeout()
+			plist.PushBack(p)
 
 		case r := <-t.gotreply:
 			var matched bool
-			for i := 0; i < len(pending); i++ {
-				if p := pending[i]; p.from == r.from && p.ptype == r.ptype {
+			for el := plist.Front(); el != nil; el = el.Next() {
+				p := el.Value.(*pending)
+				if p.from == r.from && p.ptype == r.ptype {
 					matched = true
+					// Remove the matcher if its callback indicates
+					// that all replies have been received. This is
+					// required for packet types that expect multiple
+					// reply packets.
 					if p.callback(r.data) {
-						// callback indicates the request is done, remove it.
 						p.errc <- nil
-						copy(pending[i:], pending[i+1:])
-						pending = pending[:len(pending)-1]
-						i--
+						plist.Remove(el)
 					}
 				}
 			}
 			r.matched <- matched
 
 		case now := <-timeout.C:
-			// notify and remove callbacks whose deadline is in the past.
-			i := 0
-			for ; i < len(pending) && now.After(pending[i].deadline); i++ {
-				pending[i].errc <- errTimeout
-			}
-			if i > 0 {
-				copy(pending, pending[i:])
-				pending = pending[:len(pending)-i]
+			nextTimeout = nil
+			// Notify and remove callbacks whose deadline is in the past.
+			for el := plist.Front(); el != nil; el = el.Next() {
+				p := el.Value.(*pending)
+				if now.After(p.deadline) || now.Equal(p.deadline) {
+					p.errc <- errTimeout
+					plist.Remove(el)
+				}
 			}
-			rearmTimeout()
 		}
 	}
 }
@@ -385,7 +401,7 @@ const (
 var (
 	headSpace = make([]byte, headSize)
 
-	// Neighbors responses are sent across multiple packets to
+	// Neighbors replies are sent across multiple packets to
 	// stay below the 1280 byte limit. We compute the maximum number
 	// of entries by stuffing a packet until it grows too large.
 	maxNeighbors int
diff --git a/p2p/discover/udp_test.go b/p2p/discover/udp_test.go
index b913424dd..a86d3737b 100644
--- a/p2p/discover/udp_test.go
+++ b/p2p/discover/udp_test.go
@@ -19,10 +19,12 @@ package discover
 import (
 	"bytes"
 	"crypto/ecdsa"
+	"encoding/binary"
 	"errors"
 	"fmt"
 	"io"
 	logpkg "log"
+	"math/rand"
 	"net"
 	"os"
 	"path/filepath"
@@ -138,6 +140,77 @@ func TestUDP_pingTimeout(t *testing.T) {
 	}
 }
 
+func TestUDP_responseTimeouts(t *testing.T) {
+	t.Parallel()
+	test := newUDPTest(t)
+	defer test.table.Close()
+
+	rand.Seed(time.Now().UnixNano())
+	randomDuration := func(max time.Duration) time.Duration {
+		return time.Duration(rand.Int63n(int64(max)))
+	}
+
+	var (
+		nReqs      = 200
+		nTimeouts  = 0                       // number of requests with ptype > 128
+		nilErr     = make(chan error, nReqs) // for requests that get a reply
+		timeoutErr = make(chan error, nReqs) // for requests that time out
+	)
+	for i := 0; i < nReqs; i++ {
+		// Create a matcher for a random request in udp.loop. Requests
+		// with ptype <= 128 will not get a reply and should time out.
+		// For all other requests, a reply is scheduled to arrive
+		// within the timeout window.
+		p := &pending{
+			ptype:    byte(rand.Intn(255)),
+			callback: func(interface{}) bool { return true },
+		}
+		binary.BigEndian.PutUint64(p.from[:], uint64(i))
+		if p.ptype <= 128 {
+			p.errc = timeoutErr
+			nTimeouts++
+		} else {
+			p.errc = nilErr
+			time.AfterFunc(randomDuration(60*time.Millisecond), func() {
+				if !test.udp.handleReply(p.from, p.ptype, nil) {
+					t.Logf("not matched: %v", p)
+				}
+			})
+		}
+		test.udp.addpending <- p
+		time.Sleep(randomDuration(30 * time.Millisecond))
+	}
+
+	// Check that all timeouts were delivered and that the rest got nil errors.
+	// The replies must be delivered.
+	var (
+		recvDeadline        = time.After(20 * time.Second)
+		nTimeoutsRecv, nNil = 0, 0
+	)
+	for i := 0; i < nReqs; i++ {
+		select {
+		case err := <-timeoutErr:
+			if err != errTimeout {
+				t.Fatalf("got non-timeout error on timeoutErr %d: %v", i, err)
+			}
+			nTimeoutsRecv++
+		case err := <-nilErr:
+			if err != nil {
+				t.Fatalf("got non-nil error on nilErr %d: %v", i, err)
+			}
+			nNil++
+		case <-recvDeadline:
+			t.Fatalf("exceeded recv deadline")
+		}
+	}
+	if nTimeoutsRecv != nTimeouts {
+		t.Errorf("wrong number of timeout errors received: got %d, want %d", nTimeoutsRecv, nTimeouts)
+	}
+	if nNil != nReqs-nTimeouts {
+		t.Errorf("wrong number of successful replies: got %d, want %d", nNil, nReqs-nTimeouts)
+	}
+}
+
 func TestUDP_findnodeTimeout(t *testing.T) {
 	t.Parallel()
 	test := newUDPTest(t)