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- // Copyright 2015 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/>.
- package discover
- import (
- "bytes"
- "crypto/ecdsa"
- crand "crypto/rand"
- "encoding/binary"
- "errors"
- "fmt"
- "io"
- "math/rand"
- "net"
- "reflect"
- "sync"
- "testing"
- "time"
- "github.com/ethereum/go-ethereum/internal/testlog"
- "github.com/ethereum/go-ethereum/log"
- "github.com/ethereum/go-ethereum/p2p/discover/v4wire"
- "github.com/ethereum/go-ethereum/p2p/enode"
- "github.com/ethereum/go-ethereum/p2p/enr"
- )
- // shared test variables
- var (
- futureExp = uint64(time.Now().Add(10 * time.Hour).Unix())
- testTarget = v4wire.Pubkey{0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1}
- testRemote = v4wire.Endpoint{IP: net.ParseIP("1.1.1.1").To4(), UDP: 1, TCP: 2}
- testLocalAnnounced = v4wire.Endpoint{IP: net.ParseIP("2.2.2.2").To4(), UDP: 3, TCP: 4}
- testLocal = v4wire.Endpoint{IP: net.ParseIP("3.3.3.3").To4(), UDP: 5, TCP: 6}
- )
- type udpTest struct {
- t *testing.T
- pipe *dgramPipe
- table *Table
- db *enode.DB
- udp *UDPv4
- sent [][]byte
- localkey, remotekey *ecdsa.PrivateKey
- remoteaddr *net.UDPAddr
- }
- func newUDPTest(t *testing.T) *udpTest {
- test := &udpTest{
- t: t,
- pipe: newpipe(),
- localkey: newkey(),
- remotekey: newkey(),
- remoteaddr: &net.UDPAddr{IP: net.IP{10, 0, 1, 99}, Port: 30303},
- }
- test.db, _ = enode.OpenDB("")
- ln := enode.NewLocalNode(test.db, test.localkey)
- test.udp, _ = ListenV4(test.pipe, ln, Config{
- PrivateKey: test.localkey,
- Log: testlog.Logger(t, log.LvlTrace),
- })
- test.table = test.udp.tab
- // Wait for initial refresh so the table doesn't send unexpected findnode.
- <-test.table.initDone
- return test
- }
- func (test *udpTest) close() {
- test.udp.Close()
- test.db.Close()
- }
- // handles a packet as if it had been sent to the transport.
- func (test *udpTest) packetIn(wantError error, data v4wire.Packet) {
- test.t.Helper()
- test.packetInFrom(wantError, test.remotekey, test.remoteaddr, data)
- }
- // handles a packet as if it had been sent to the transport by the key/endpoint.
- func (test *udpTest) packetInFrom(wantError error, key *ecdsa.PrivateKey, addr *net.UDPAddr, data v4wire.Packet) {
- test.t.Helper()
- enc, _, err := v4wire.Encode(key, data)
- if err != nil {
- test.t.Errorf("%s encode error: %v", data.Name(), err)
- }
- test.sent = append(test.sent, enc)
- if err = test.udp.handlePacket(addr, enc); err != wantError {
- test.t.Errorf("error mismatch: got %q, want %q", err, wantError)
- }
- }
- // waits for a packet to be sent by the transport.
- // validate should have type func(X, *net.UDPAddr, []byte), where X is a packet type.
- func (test *udpTest) waitPacketOut(validate interface{}) (closed bool) {
- test.t.Helper()
- dgram, err := test.pipe.receive()
- if err == errClosed {
- return true
- } else if err != nil {
- test.t.Error("packet receive error:", err)
- return false
- }
- p, _, hash, err := v4wire.Decode(dgram.data)
- if err != nil {
- test.t.Errorf("sent packet decode error: %v", err)
- return false
- }
- fn := reflect.ValueOf(validate)
- exptype := fn.Type().In(0)
- if !reflect.TypeOf(p).AssignableTo(exptype) {
- test.t.Errorf("sent packet type mismatch, got: %v, want: %v", reflect.TypeOf(p), exptype)
- return false
- }
- fn.Call([]reflect.Value{reflect.ValueOf(p), reflect.ValueOf(&dgram.to), reflect.ValueOf(hash)})
- return false
- }
- func TestUDPv4_packetErrors(t *testing.T) {
- test := newUDPTest(t)
- defer test.close()
- test.packetIn(errExpired, &v4wire.Ping{From: testRemote, To: testLocalAnnounced, Version: 4})
- test.packetIn(errUnsolicitedReply, &v4wire.Pong{ReplyTok: []byte{}, Expiration: futureExp})
- test.packetIn(errUnknownNode, &v4wire.Findnode{Expiration: futureExp})
- test.packetIn(errUnsolicitedReply, &v4wire.Neighbors{Expiration: futureExp})
- }
- func TestUDPv4_pingTimeout(t *testing.T) {
- t.Parallel()
- test := newUDPTest(t)
- defer test.close()
- key := newkey()
- toaddr := &net.UDPAddr{IP: net.ParseIP("1.2.3.4"), Port: 2222}
- node := enode.NewV4(&key.PublicKey, toaddr.IP, 0, toaddr.Port)
- if _, err := test.udp.ping(node); err != errTimeout {
- t.Error("expected timeout error, got", err)
- }
- }
- type testPacket byte
- func (req testPacket) Kind() byte { return byte(req) }
- func (req testPacket) Name() string { return "" }
- func TestUDPv4_responseTimeouts(t *testing.T) {
- t.Parallel()
- test := newUDPTest(t)
- defer test.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 := &replyMatcher{
- ptype: byte(rand.Intn(255)),
- callback: func(v4wire.Packet) (bool, bool) { return true, true },
- }
- binary.BigEndian.PutUint64(p.from[:], uint64(i))
- if p.ptype <= 128 {
- p.errc = timeoutErr
- test.udp.addReplyMatcher <- p
- nTimeouts++
- } else {
- p.errc = nilErr
- test.udp.addReplyMatcher <- p
- time.AfterFunc(randomDuration(60*time.Millisecond), func() {
- if !test.udp.handleReply(p.from, p.ip, testPacket(p.ptype)) {
- t.Logf("not matched: %v", 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 TestUDPv4_findnodeTimeout(t *testing.T) {
- t.Parallel()
- test := newUDPTest(t)
- defer test.close()
- toaddr := &net.UDPAddr{IP: net.ParseIP("1.2.3.4"), Port: 2222}
- toid := enode.ID{1, 2, 3, 4}
- target := v4wire.Pubkey{4, 5, 6, 7}
- result, err := test.udp.findnode(toid, toaddr, target)
- if err != errTimeout {
- t.Error("expected timeout error, got", err)
- }
- if len(result) > 0 {
- t.Error("expected empty result, got", result)
- }
- }
- func TestUDPv4_findnode(t *testing.T) {
- test := newUDPTest(t)
- defer test.close()
- // put a few nodes into the table. their exact
- // distribution shouldn't matter much, although we need to
- // take care not to overflow any bucket.
- nodes := &nodesByDistance{target: testTarget.ID()}
- live := make(map[enode.ID]bool)
- numCandidates := 2 * bucketSize
- for i := 0; i < numCandidates; i++ {
- key := newkey()
- ip := net.IP{10, 13, 0, byte(i)}
- n := wrapNode(enode.NewV4(&key.PublicKey, ip, 0, 2000))
- // Ensure half of table content isn't verified live yet.
- if i > numCandidates/2 {
- n.livenessChecks = 1
- live[n.ID()] = true
- }
- nodes.push(n, numCandidates)
- }
- fillTable(test.table, nodes.entries)
- // ensure there's a bond with the test node,
- // findnode won't be accepted otherwise.
- remoteID := v4wire.EncodePubkey(&test.remotekey.PublicKey).ID()
- test.table.db.UpdateLastPongReceived(remoteID, test.remoteaddr.IP, time.Now())
- // check that closest neighbors are returned.
- expected := test.table.findnodeByID(testTarget.ID(), bucketSize, true)
- test.packetIn(nil, &v4wire.Findnode{Target: testTarget, Expiration: futureExp})
- waitNeighbors := func(want []*node) {
- test.waitPacketOut(func(p *v4wire.Neighbors, to *net.UDPAddr, hash []byte) {
- if len(p.Nodes) != len(want) {
- t.Errorf("wrong number of results: got %d, want %d", len(p.Nodes), bucketSize)
- }
- for i, n := range p.Nodes {
- if n.ID.ID() != want[i].ID() {
- t.Errorf("result mismatch at %d:\n got: %v\n want: %v", i, n, expected.entries[i])
- }
- if !live[n.ID.ID()] {
- t.Errorf("result includes dead node %v", n.ID.ID())
- }
- }
- })
- }
- // Receive replies.
- want := expected.entries
- if len(want) > v4wire.MaxNeighbors {
- waitNeighbors(want[:v4wire.MaxNeighbors])
- want = want[v4wire.MaxNeighbors:]
- }
- waitNeighbors(want)
- }
- func TestUDPv4_findnodeMultiReply(t *testing.T) {
- test := newUDPTest(t)
- defer test.close()
- rid := enode.PubkeyToIDV4(&test.remotekey.PublicKey)
- test.table.db.UpdateLastPingReceived(rid, test.remoteaddr.IP, time.Now())
- // queue a pending findnode request
- resultc, errc := make(chan []*node), make(chan error)
- go func() {
- rid := encodePubkey(&test.remotekey.PublicKey).id()
- ns, err := test.udp.findnode(rid, test.remoteaddr, testTarget)
- if err != nil && len(ns) == 0 {
- errc <- err
- } else {
- resultc <- ns
- }
- }()
- // wait for the findnode to be sent.
- // after it is sent, the transport is waiting for a reply
- test.waitPacketOut(func(p *v4wire.Findnode, to *net.UDPAddr, hash []byte) {
- if p.Target != testTarget {
- t.Errorf("wrong target: got %v, want %v", p.Target, testTarget)
- }
- })
- // send the reply as two packets.
- list := []*node{
- wrapNode(enode.MustParse("enode://ba85011c70bcc5c04d8607d3a0ed29aa6179c092cbdda10d5d32684fb33ed01bd94f588ca8f91ac48318087dcb02eaf36773a7a453f0eedd6742af668097b29c@10.0.1.16:30303?discport=30304")),
- wrapNode(enode.MustParse("enode://81fa361d25f157cd421c60dcc28d8dac5ef6a89476633339c5df30287474520caca09627da18543d9079b5b288698b542d56167aa5c09111e55acdbbdf2ef799@10.0.1.16:30303")),
- wrapNode(enode.MustParse("enode://9bffefd833d53fac8e652415f4973bee289e8b1a5c6c4cbe70abf817ce8a64cee11b823b66a987f51aaa9fba0d6a91b3e6bf0d5a5d1042de8e9eeea057b217f8@10.0.1.36:30301?discport=17")),
- wrapNode(enode.MustParse("enode://1b5b4aa662d7cb44a7221bfba67302590b643028197a7d5214790f3bac7aaa4a3241be9e83c09cf1f6c69d007c634faae3dc1b1221793e8446c0b3a09de65960@10.0.1.16:30303")),
- }
- rpclist := make([]v4wire.Node, len(list))
- for i := range list {
- rpclist[i] = nodeToRPC(list[i])
- }
- test.packetIn(nil, &v4wire.Neighbors{Expiration: futureExp, Nodes: rpclist[:2]})
- test.packetIn(nil, &v4wire.Neighbors{Expiration: futureExp, Nodes: rpclist[2:]})
- // check that the sent neighbors are all returned by findnode
- select {
- case result := <-resultc:
- want := append(list[:2], list[3:]...)
- if !reflect.DeepEqual(result, want) {
- t.Errorf("neighbors mismatch:\n got: %v\n want: %v", result, want)
- }
- case err := <-errc:
- t.Errorf("findnode error: %v", err)
- case <-time.After(5 * time.Second):
- t.Error("findnode did not return within 5 seconds")
- }
- }
- // This test checks that reply matching of pong verifies the ping hash.
- func TestUDPv4_pingMatch(t *testing.T) {
- test := newUDPTest(t)
- defer test.close()
- randToken := make([]byte, 32)
- crand.Read(randToken)
- test.packetIn(nil, &v4wire.Ping{From: testRemote, To: testLocalAnnounced, Version: 4, Expiration: futureExp})
- test.waitPacketOut(func(*v4wire.Pong, *net.UDPAddr, []byte) {})
- test.waitPacketOut(func(*v4wire.Ping, *net.UDPAddr, []byte) {})
- test.packetIn(errUnsolicitedReply, &v4wire.Pong{ReplyTok: randToken, To: testLocalAnnounced, Expiration: futureExp})
- }
- // This test checks that reply matching of pong verifies the sender IP address.
- func TestUDPv4_pingMatchIP(t *testing.T) {
- test := newUDPTest(t)
- defer test.close()
- test.packetIn(nil, &v4wire.Ping{From: testRemote, To: testLocalAnnounced, Version: 4, Expiration: futureExp})
- test.waitPacketOut(func(*v4wire.Pong, *net.UDPAddr, []byte) {})
- test.waitPacketOut(func(p *v4wire.Ping, to *net.UDPAddr, hash []byte) {
- wrongAddr := &net.UDPAddr{IP: net.IP{33, 44, 1, 2}, Port: 30000}
- test.packetInFrom(errUnsolicitedReply, test.remotekey, wrongAddr, &v4wire.Pong{
- ReplyTok: hash,
- To: testLocalAnnounced,
- Expiration: futureExp,
- })
- })
- }
- func TestUDPv4_successfulPing(t *testing.T) {
- test := newUDPTest(t)
- added := make(chan *node, 1)
- test.table.nodeAddedHook = func(n *node) { added <- n }
- defer test.close()
- // The remote side sends a ping packet to initiate the exchange.
- go test.packetIn(nil, &v4wire.Ping{From: testRemote, To: testLocalAnnounced, Version: 4, Expiration: futureExp})
- // The ping is replied to.
- test.waitPacketOut(func(p *v4wire.Pong, to *net.UDPAddr, hash []byte) {
- pinghash := test.sent[0][:32]
- if !bytes.Equal(p.ReplyTok, pinghash) {
- t.Errorf("got pong.ReplyTok %x, want %x", p.ReplyTok, pinghash)
- }
- wantTo := v4wire.Endpoint{
- // The mirrored UDP address is the UDP packet sender
- IP: test.remoteaddr.IP, UDP: uint16(test.remoteaddr.Port),
- // The mirrored TCP port is the one from the ping packet
- TCP: testRemote.TCP,
- }
- if !reflect.DeepEqual(p.To, wantTo) {
- t.Errorf("got pong.To %v, want %v", p.To, wantTo)
- }
- })
- // Remote is unknown, the table pings back.
- test.waitPacketOut(func(p *v4wire.Ping, to *net.UDPAddr, hash []byte) {
- if !reflect.DeepEqual(p.From, test.udp.ourEndpoint()) {
- t.Errorf("got ping.From %#v, want %#v", p.From, test.udp.ourEndpoint())
- }
- wantTo := v4wire.Endpoint{
- // The mirrored UDP address is the UDP packet sender.
- IP: test.remoteaddr.IP,
- UDP: uint16(test.remoteaddr.Port),
- TCP: 0,
- }
- if !reflect.DeepEqual(p.To, wantTo) {
- t.Errorf("got ping.To %v, want %v", p.To, wantTo)
- }
- test.packetIn(nil, &v4wire.Pong{ReplyTok: hash, Expiration: futureExp})
- })
- // The node should be added to the table shortly after getting the
- // pong packet.
- select {
- case n := <-added:
- rid := encodePubkey(&test.remotekey.PublicKey).id()
- if n.ID() != rid {
- t.Errorf("node has wrong ID: got %v, want %v", n.ID(), rid)
- }
- if !n.IP().Equal(test.remoteaddr.IP) {
- t.Errorf("node has wrong IP: got %v, want: %v", n.IP(), test.remoteaddr.IP)
- }
- if n.UDP() != test.remoteaddr.Port {
- t.Errorf("node has wrong UDP port: got %v, want: %v", n.UDP(), test.remoteaddr.Port)
- }
- if n.TCP() != int(testRemote.TCP) {
- t.Errorf("node has wrong TCP port: got %v, want: %v", n.TCP(), testRemote.TCP)
- }
- case <-time.After(2 * time.Second):
- t.Errorf("node was not added within 2 seconds")
- }
- }
- // This test checks that EIP-868 requests work.
- func TestUDPv4_EIP868(t *testing.T) {
- test := newUDPTest(t)
- defer test.close()
- test.udp.localNode.Set(enr.WithEntry("foo", "bar"))
- wantNode := test.udp.localNode.Node()
- // ENR requests aren't allowed before endpoint proof.
- test.packetIn(errUnknownNode, &v4wire.ENRRequest{Expiration: futureExp})
- // Perform endpoint proof and check for sequence number in packet tail.
- test.packetIn(nil, &v4wire.Ping{Expiration: futureExp})
- test.waitPacketOut(func(p *v4wire.Pong, addr *net.UDPAddr, hash []byte) {
- if p.ENRSeq() != wantNode.Seq() {
- t.Errorf("wrong sequence number in pong: %d, want %d", p.ENRSeq(), wantNode.Seq())
- }
- })
- test.waitPacketOut(func(p *v4wire.Ping, addr *net.UDPAddr, hash []byte) {
- if p.ENRSeq() != wantNode.Seq() {
- t.Errorf("wrong sequence number in ping: %d, want %d", p.ENRSeq(), wantNode.Seq())
- }
- test.packetIn(nil, &v4wire.Pong{Expiration: futureExp, ReplyTok: hash})
- })
- // Request should work now.
- test.packetIn(nil, &v4wire.ENRRequest{Expiration: futureExp})
- test.waitPacketOut(func(p *v4wire.ENRResponse, addr *net.UDPAddr, hash []byte) {
- n, err := enode.New(enode.ValidSchemes, &p.Record)
- if err != nil {
- t.Fatalf("invalid record: %v", err)
- }
- if !reflect.DeepEqual(n, wantNode) {
- t.Fatalf("wrong node in enrResponse: %v", n)
- }
- })
- }
- // This test verifies that a small network of nodes can boot up into a healthy state.
- func TestUDPv4_smallNetConvergence(t *testing.T) {
- t.Parallel()
- // Start the network.
- nodes := make([]*UDPv4, 4)
- for i := range nodes {
- var cfg Config
- if i > 0 {
- bn := nodes[0].Self()
- cfg.Bootnodes = []*enode.Node{bn}
- }
- nodes[i] = startLocalhostV4(t, cfg)
- defer nodes[i].Close()
- }
- // Run through the iterator on all nodes until
- // they have all found each other.
- status := make(chan error, len(nodes))
- for i := range nodes {
- node := nodes[i]
- go func() {
- found := make(map[enode.ID]bool, len(nodes))
- it := node.RandomNodes()
- for it.Next() {
- found[it.Node().ID()] = true
- if len(found) == len(nodes) {
- status <- nil
- return
- }
- }
- status <- fmt.Errorf("node %s didn't find all nodes", node.Self().ID().TerminalString())
- }()
- }
- // Wait for all status reports.
- timeout := time.NewTimer(30 * time.Second)
- defer timeout.Stop()
- for received := 0; received < len(nodes); {
- select {
- case <-timeout.C:
- for _, node := range nodes {
- node.Close()
- }
- case err := <-status:
- received++
- if err != nil {
- t.Error("ERROR:", err)
- return
- }
- }
- }
- }
- func startLocalhostV4(t *testing.T, cfg Config) *UDPv4 {
- t.Helper()
- cfg.PrivateKey = newkey()
- db, _ := enode.OpenDB("")
- ln := enode.NewLocalNode(db, cfg.PrivateKey)
- // Prefix logs with node ID.
- lprefix := fmt.Sprintf("(%s)", ln.ID().TerminalString())
- lfmt := log.TerminalFormat(false)
- cfg.Log = testlog.Logger(t, log.LvlTrace)
- cfg.Log.SetHandler(log.FuncHandler(func(r *log.Record) error {
- t.Logf("%s %s", lprefix, lfmt.Format(r))
- return nil
- }))
- // Listen.
- socket, err := net.ListenUDP("udp4", &net.UDPAddr{IP: net.IP{127, 0, 0, 1}})
- if err != nil {
- t.Fatal(err)
- }
- realaddr := socket.LocalAddr().(*net.UDPAddr)
- ln.SetStaticIP(realaddr.IP)
- ln.SetFallbackUDP(realaddr.Port)
- udp, err := ListenV4(socket, ln, cfg)
- if err != nil {
- t.Fatal(err)
- }
- return udp
- }
- // dgramPipe is a fake UDP socket. It queues all sent datagrams.
- type dgramPipe struct {
- mu *sync.Mutex
- cond *sync.Cond
- closing chan struct{}
- closed bool
- queue []dgram
- }
- type dgram struct {
- to net.UDPAddr
- data []byte
- }
- func newpipe() *dgramPipe {
- mu := new(sync.Mutex)
- return &dgramPipe{
- closing: make(chan struct{}),
- cond: &sync.Cond{L: mu},
- mu: mu,
- }
- }
- // WriteToUDP queues a datagram.
- func (c *dgramPipe) WriteToUDP(b []byte, to *net.UDPAddr) (n int, err error) {
- msg := make([]byte, len(b))
- copy(msg, b)
- c.mu.Lock()
- defer c.mu.Unlock()
- if c.closed {
- return 0, errors.New("closed")
- }
- c.queue = append(c.queue, dgram{*to, b})
- c.cond.Signal()
- return len(b), nil
- }
- // ReadFromUDP just hangs until the pipe is closed.
- func (c *dgramPipe) ReadFromUDP(b []byte) (n int, addr *net.UDPAddr, err error) {
- <-c.closing
- return 0, nil, io.EOF
- }
- func (c *dgramPipe) Close() error {
- c.mu.Lock()
- defer c.mu.Unlock()
- if !c.closed {
- close(c.closing)
- c.closed = true
- }
- c.cond.Broadcast()
- return nil
- }
- func (c *dgramPipe) LocalAddr() net.Addr {
- return &net.UDPAddr{IP: testLocal.IP, Port: int(testLocal.UDP)}
- }
- func (c *dgramPipe) receive() (dgram, error) {
- c.mu.Lock()
- defer c.mu.Unlock()
- var timedOut bool
- timer := time.AfterFunc(3*time.Second, func() {
- c.mu.Lock()
- timedOut = true
- c.mu.Unlock()
- c.cond.Broadcast()
- })
- defer timer.Stop()
- for len(c.queue) == 0 && !c.closed && !timedOut {
- c.cond.Wait()
- }
- if c.closed {
- return dgram{}, errClosed
- }
- if timedOut {
- return dgram{}, errTimeout
- }
- p := c.queue[0]
- copy(c.queue, c.queue[1:])
- c.queue = c.queue[:len(c.queue)-1]
- return p, nil
- }
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