github.com/Night-mk/quorum@v21.1.0+incompatible/p2p/server_test.go

// Copyright 2014 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 p2p

import (
	"crypto/ecdsa"
	"errors"
	"io"
	"io/ioutil"
	"math/rand"
	"net"
	"os"
	"path"
	"reflect"
	"testing"
	"time"

	"github.com/stretchr/testify/assert"
	"golang.org/x/crypto/sha3"

	"github.com/ethereum/go-ethereum/crypto"
	"github.com/ethereum/go-ethereum/internal/testlog"
	"github.com/ethereum/go-ethereum/log"
	"github.com/ethereum/go-ethereum/p2p/enode"
	"github.com/ethereum/go-ethereum/p2p/enr"
	"github.com/ethereum/go-ethereum/params"
)

// func init() {
// 	log.Root().SetHandler(log.LvlFilterHandler(log.LvlTrace, log.StreamHandler(os.Stderr, log.TerminalFormat(false))))
// }

type testTransport struct {
	rpub *ecdsa.PublicKey
	*rlpx

	closeErr error
}

func newTestTransport(rpub *ecdsa.PublicKey, fd net.Conn) transport {
	wrapped := newRLPX(fd).(*rlpx)
	wrapped.rw = newRLPXFrameRW(fd, secrets{
		MAC:        zero16,
		AES:        zero16,
		IngressMAC: sha3.NewLegacyKeccak256(),
		EgressMAC:  sha3.NewLegacyKeccak256(),
	})
	return &testTransport{rpub: rpub, rlpx: wrapped}
}

func (c *testTransport) doEncHandshake(prv *ecdsa.PrivateKey, dialDest *ecdsa.PublicKey) (*ecdsa.PublicKey, error) {
	return c.rpub, nil
}

func (c *testTransport) doProtoHandshake(our *protoHandshake) (*protoHandshake, error) {
	pubkey := crypto.FromECDSAPub(c.rpub)[1:]
	return &protoHandshake{ID: pubkey, Name: "test"}, nil
}

func (c *testTransport) close(err error) {
	c.rlpx.fd.Close()
	c.closeErr = err
}

func startTestServer(t *testing.T, remoteKey *ecdsa.PublicKey, pf func(*Peer)) *Server {
	config := Config{
		Name:       "test",
		MaxPeers:   10,
		ListenAddr: "127.0.0.1:0",
		PrivateKey: newkey(),
		Logger:     testlog.Logger(t, log.LvlTrace),
	}
	server := &Server{
		Config:       config,
		newPeerHook:  pf,
		newTransport: func(fd net.Conn) transport { return newTestTransport(remoteKey, fd) },
	}
	if err := server.Start(); err != nil {
		t.Fatalf("Could not start server: %v", err)
	}
	return server
}

func TestServerListen(t *testing.T) {
	// start the test server
	connected := make(chan *Peer)
	remid := &newkey().PublicKey
	srv := startTestServer(t, remid, func(p *Peer) {
		if p.ID() != enode.PubkeyToIDV4(remid) {
			t.Error("peer func called with wrong node id")
		}
		connected <- p
	})
	defer close(connected)
	defer srv.Stop()

	// dial the test server
	conn, err := net.DialTimeout("tcp", srv.ListenAddr, 5*time.Second)
	if err != nil {
		t.Fatalf("could not dial: %v", err)
	}
	defer conn.Close()

	select {
	case peer := <-connected:
		if peer.LocalAddr().String() != conn.RemoteAddr().String() {
			t.Errorf("peer started with wrong conn: got %v, want %v",
				peer.LocalAddr(), conn.RemoteAddr())
		}
		peers := srv.Peers()
		if !reflect.DeepEqual(peers, []*Peer{peer}) {
			t.Errorf("Peers mismatch: got %v, want %v", peers, []*Peer{peer})
		}
	case <-time.After(1 * time.Second):
		t.Error("server did not accept within one second")
	}
}

func TestServerDial(t *testing.T) {
	// run a one-shot TCP server to handle the connection.
	listener, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("could not setup listener: %v", err)
	}
	defer listener.Close()
	accepted := make(chan net.Conn)
	go func() {
		conn, err := listener.Accept()
		if err != nil {
			t.Error("accept error:", err)
			return
		}
		accepted <- conn
	}()

	// start the server
	connected := make(chan *Peer)
	remid := &newkey().PublicKey
	srv := startTestServer(t, remid, func(p *Peer) { connected <- p })
	defer close(connected)
	defer srv.Stop()

	// tell the server to connect
	tcpAddr := listener.Addr().(*net.TCPAddr)
	node := enode.NewV4(remid, tcpAddr.IP, tcpAddr.Port, 0)
	srv.AddPeer(node)

	select {
	case conn := <-accepted:
		defer conn.Close()

		select {
		case peer := <-connected:
			if peer.ID() != enode.PubkeyToIDV4(remid) {
				t.Errorf("peer has wrong id")
			}
			if peer.Name() != "test" {
				t.Errorf("peer has wrong name")
			}
			if peer.RemoteAddr().String() != conn.LocalAddr().String() {
				t.Errorf("peer started with wrong conn: got %v, want %v",
					peer.RemoteAddr(), conn.LocalAddr())
			}
			peers := srv.Peers()
			if !reflect.DeepEqual(peers, []*Peer{peer}) {
				t.Errorf("Peers mismatch: got %v, want %v", peers, []*Peer{peer})
			}

			// Test AddTrustedPeer/RemoveTrustedPeer and changing Trusted flags
			// Particularly for race conditions on changing the flag state.
			if peer := srv.Peers()[0]; peer.Info().Network.Trusted {
				t.Errorf("peer is trusted prematurely: %v", peer)
			}
			done := make(chan bool)
			go func() {
				srv.AddTrustedPeer(node)
				if peer := srv.Peers()[0]; !peer.Info().Network.Trusted {
					t.Errorf("peer is not trusted after AddTrustedPeer: %v", peer)
				}
				srv.RemoveTrustedPeer(node)
				if peer := srv.Peers()[0]; peer.Info().Network.Trusted {
					t.Errorf("peer is trusted after RemoveTrustedPeer: %v", peer)
				}
				done <- true
			}()
			// Trigger potential race conditions
			peer = srv.Peers()[0]
			_ = peer.Inbound()
			_ = peer.Info()
			<-done
		case <-time.After(1 * time.Second):
			t.Error("server did not launch peer within one second")
		}

	case <-time.After(1 * time.Second):
		t.Error("server did not connect within one second")
	}
}

// This test checks that tasks generated by dialstate are
// actually executed and taskdone is called for them.
func TestServerTaskScheduling(t *testing.T) {
	var (
		done           = make(chan *testTask)
		quit, returned = make(chan struct{}), make(chan struct{})
		tc             = 0
		tg             = taskgen{
			newFunc: func(running int, peers map[enode.ID]*Peer) []task {
				tc++
				return []task{&testTask{index: tc - 1}}
			},
			doneFunc: func(t task) {
				select {
				case done <- t.(*testTask):
				case <-quit:
				}
			},
		}
	)

	// The Server in this test isn't actually running
	// because we're only interested in what run does.
	db, _ := enode.OpenDB("")
	srv := &Server{
		Config:    Config{MaxPeers: 10},
		localnode: enode.NewLocalNode(db, newkey()),
		nodedb:    db,
		discmix:   enode.NewFairMix(0),
		quit:      make(chan struct{}),
		running:   true,
		log:       log.New(),
	}
	srv.loopWG.Add(1)
	go func() {
		srv.run(tg)
		close(returned)
	}()

	var gotdone []*testTask
	for i := 0; i < 100; i++ {
		gotdone = append(gotdone, <-done)
	}
	for i, task := range gotdone {
		if task.index != i {
			t.Errorf("task %d has wrong index, got %d", i, task.index)
			break
		}
		if !task.called {
			t.Errorf("task %d was not called", i)
			break
		}
	}

	close(quit)
	srv.Stop()
	select {
	case <-returned:
	case <-time.After(500 * time.Millisecond):
		t.Error("Server.run did not return within 500ms")
	}
}

// This test checks that Server doesn't drop tasks,
// even if newTasks returns more than the maximum number of tasks.
func TestServerManyTasks(t *testing.T) {
	alltasks := make([]task, 300)
	for i := range alltasks {
		alltasks[i] = &testTask{index: i}
	}

	var (
		db, _ = enode.OpenDB("")
		srv   = &Server{
			quit:      make(chan struct{}),
			localnode: enode.NewLocalNode(db, newkey()),
			nodedb:    db,
			running:   true,
			log:       log.New(),
			discmix:   enode.NewFairMix(0),
		}
		done       = make(chan *testTask)
		start, end = 0, 0
	)
	defer srv.Stop()
	srv.loopWG.Add(1)
	go srv.run(taskgen{
		newFunc: func(running int, peers map[enode.ID]*Peer) []task {
			start, end = end, end+maxActiveDialTasks+10
			if end > len(alltasks) {
				end = len(alltasks)
			}
			return alltasks[start:end]
		},
		doneFunc: func(tt task) {
			done <- tt.(*testTask)
		},
	})

	doneset := make(map[int]bool)
	timeout := time.After(2 * time.Second)
	for len(doneset) < len(alltasks) {
		select {
		case tt := <-done:
			if doneset[tt.index] {
				t.Errorf("task %d got done more than once", tt.index)
			} else {
				doneset[tt.index] = true
			}
		case <-timeout:
			t.Errorf("%d of %d tasks got done within 2s", len(doneset), len(alltasks))
			for i := 0; i < len(alltasks); i++ {
				if !doneset[i] {
					t.Logf("task %d not done", i)
				}
			}
			return
		}
	}
}

type taskgen struct {
	newFunc  func(running int, peers map[enode.ID]*Peer) []task
	doneFunc func(task)
}

func (tg taskgen) newTasks(running int, peers map[enode.ID]*Peer, now time.Time) []task {
	return tg.newFunc(running, peers)
}
func (tg taskgen) taskDone(t task, now time.Time) {
	tg.doneFunc(t)
}
func (tg taskgen) addStatic(*enode.Node) {
}
func (tg taskgen) removeStatic(*enode.Node) {
}

type testTask struct {
	index  int
	called bool
}

func (t *testTask) Do(srv *Server) {
	t.called = true
}

// This test checks that connections are disconnected
// just after the encryption handshake when the server is
// at capacity. Trusted connections should still be accepted.
func TestServerAtCap(t *testing.T) {
	trustedNode := newkey()
	trustedID := enode.PubkeyToIDV4(&trustedNode.PublicKey)
	srv := &Server{
		Config: Config{
			PrivateKey:   newkey(),
			MaxPeers:     10,
			NoDial:       true,
			NoDiscovery:  true,
			TrustedNodes: []*enode.Node{newNode(trustedID, nil)},
		},
	}
	if err := srv.Start(); err != nil {
		t.Fatalf("could not start: %v", err)
	}
	defer srv.Stop()

	newconn := func(id enode.ID) *conn {
		fd, _ := net.Pipe()
		tx := newTestTransport(&trustedNode.PublicKey, fd)
		node := enode.SignNull(new(enr.Record), id)
		return &conn{fd: fd, transport: tx, flags: inboundConn, node: node, cont: make(chan error)}
	}

	// Inject a few connections to fill up the peer set.
	for i := 0; i < 10; i++ {
		c := newconn(randomID())
		if err := srv.checkpoint(c, srv.checkpointAddPeer); err != nil {
			t.Fatalf("could not add conn %d: %v", i, err)
		}
	}
	// Try inserting a non-trusted connection.
	anotherID := randomID()
	c := newconn(anotherID)
	if err := srv.checkpoint(c, srv.checkpointPostHandshake); err != DiscTooManyPeers {
		t.Error("wrong error for insert:", err)
	}
	// Try inserting a trusted connection.
	c = newconn(trustedID)
	if err := srv.checkpoint(c, srv.checkpointPostHandshake); err != nil {
		t.Error("unexpected error for trusted conn @posthandshake:", err)
	}
	if !c.is(trustedConn) {
		t.Error("Server did not set trusted flag")
	}

	// Remove from trusted set and try again
	srv.RemoveTrustedPeer(newNode(trustedID, nil))
	c = newconn(trustedID)
	if err := srv.checkpoint(c, srv.checkpointPostHandshake); err != DiscTooManyPeers {
		t.Error("wrong error for insert:", err)
	}

	// Add anotherID to trusted set and try again
	srv.AddTrustedPeer(newNode(anotherID, nil))
	c = newconn(anotherID)
	if err := srv.checkpoint(c, srv.checkpointPostHandshake); err != nil {
		t.Error("unexpected error for trusted conn @posthandshake:", err)
	}
	if !c.is(trustedConn) {
		t.Error("Server did not set trusted flag")
	}
}

func TestServerPeerLimits(t *testing.T) {
	srvkey := newkey()
	clientkey := newkey()
	clientnode := enode.NewV4(&clientkey.PublicKey, nil, 0, 0)

	var tp = &setupTransport{
		pubkey: &clientkey.PublicKey,
		phs: protoHandshake{
			ID: crypto.FromECDSAPub(&clientkey.PublicKey)[1:],
			// Force "DiscUselessPeer" due to unmatching caps
			// Caps: []Cap{discard.cap()},
		},
	}

	srv := &Server{
		Config: Config{
			PrivateKey:  srvkey,
			MaxPeers:    0,
			NoDial:      true,
			NoDiscovery: true,
			Protocols:   []Protocol{discard},
		},
		newTransport: func(fd net.Conn) transport { return tp },
		log:          log.New(),
	}
	if err := srv.Start(); err != nil {
		t.Fatalf("couldn't start server: %v", err)
	}
	defer srv.Stop()

	// Check that server is full (MaxPeers=0)
	flags := dynDialedConn
	dialDest := clientnode
	conn, _ := net.Pipe()
	srv.SetupConn(conn, flags, dialDest)
	if tp.closeErr != DiscTooManyPeers {
		t.Errorf("unexpected close error: %q", tp.closeErr)
	}
	conn.Close()

	srv.AddTrustedPeer(clientnode)

	// Check that server allows a trusted peer despite being full.
	conn, _ = net.Pipe()
	srv.SetupConn(conn, flags, dialDest)
	if tp.closeErr == DiscTooManyPeers {
		t.Errorf("failed to bypass MaxPeers with trusted node: %q", tp.closeErr)
	}

	if tp.closeErr != DiscUselessPeer {
		t.Errorf("unexpected close error: %q", tp.closeErr)
	}
	conn.Close()

	srv.RemoveTrustedPeer(clientnode)

	// Check that server is full again.
	conn, _ = net.Pipe()
	srv.SetupConn(conn, flags, dialDest)
	if tp.closeErr != DiscTooManyPeers {
		t.Errorf("unexpected close error: %q", tp.closeErr)
	}
	conn.Close()
}

func TestServerSetupConn(t *testing.T) {
	var (
		clientkey, srvkey = newkey(), newkey()
		clientpub         = &clientkey.PublicKey
		srvpub            = &srvkey.PublicKey
	)
	tests := []struct {
		dontstart bool
		tt        *setupTransport
		flags     connFlag
		dialDest  *enode.Node

		wantCloseErr error
		wantCalls    string
	}{
		{
			dontstart:    true,
			tt:           &setupTransport{pubkey: clientpub},
			wantCalls:    "close,",
			wantCloseErr: errServerStopped,
		},
		{
			tt:           &setupTransport{pubkey: clientpub, encHandshakeErr: errors.New("read error")},
			flags:        inboundConn,
			wantCalls:    "doEncHandshake,close,",
			wantCloseErr: errors.New("read error"),
		},
		{
			tt:           &setupTransport{pubkey: clientpub},
			dialDest:     enode.NewV4(&newkey().PublicKey, nil, 0, 0),
			flags:        dynDialedConn,
			wantCalls:    "doEncHandshake,close,",
			wantCloseErr: DiscUnexpectedIdentity,
		},
		{
			tt:           &setupTransport{pubkey: clientpub, phs: protoHandshake{ID: randomID().Bytes()}},
			dialDest:     enode.NewV4(clientpub, nil, 0, 0),
			flags:        dynDialedConn,
			wantCalls:    "doEncHandshake,doProtoHandshake,close,",
			wantCloseErr: DiscUnexpectedIdentity,
		},
		{
			tt:           &setupTransport{pubkey: clientpub, protoHandshakeErr: errors.New("foo")},
			dialDest:     enode.NewV4(clientpub, nil, 0, 0),
			flags:        dynDialedConn,
			wantCalls:    "doEncHandshake,doProtoHandshake,close,",
			wantCloseErr: errors.New("foo"),
		},
		{
			tt:           &setupTransport{pubkey: srvpub, phs: protoHandshake{ID: crypto.FromECDSAPub(srvpub)[1:]}},
			flags:        inboundConn,
			wantCalls:    "doEncHandshake,close,",
			wantCloseErr: DiscSelf,
		},
		{
			tt:           &setupTransport{pubkey: clientpub, phs: protoHandshake{ID: crypto.FromECDSAPub(clientpub)[1:]}},
			flags:        inboundConn,
			wantCalls:    "doEncHandshake,doProtoHandshake,close,",
			wantCloseErr: DiscUselessPeer,
		},
	}

	for i, test := range tests {
		t.Run(test.wantCalls, func(t *testing.T) {
			cfg := Config{
				PrivateKey:  srvkey,
				MaxPeers:    10,
				NoDial:      true,
				NoDiscovery: true,
				Protocols:   []Protocol{discard},
				Logger:      testlog.Logger(t, log.LvlTrace),
			}
			srv := &Server{
				Config:       cfg,
				newTransport: func(fd net.Conn) transport { return test.tt },
				log:          cfg.Logger,
			}
			if !test.dontstart {
				if err := srv.Start(); err != nil {
					t.Fatalf("couldn't start server: %v", err)
				}
				defer srv.Stop()
			}
			p1, _ := net.Pipe()
			srv.SetupConn(p1, test.flags, test.dialDest)
			if !reflect.DeepEqual(test.tt.closeErr, test.wantCloseErr) {
				t.Errorf("test %d: close error mismatch: got %q, want %q", i, test.tt.closeErr, test.wantCloseErr)
			}
			if test.tt.calls != test.wantCalls {
				t.Errorf("test %d: calls mismatch: got %q, want %q", i, test.tt.calls, test.wantCalls)
			}
		})
	}
}

func TestServerSetupConn_whenNotInRaftCluster(t *testing.T) {
	var (
		clientkey, srvkey = newkey(), newkey()
		clientpub         = &clientkey.PublicKey
	)

	clientNode := enode.NewV4(clientpub, nil, 0, 0)
	srv := &Server{
		Config: Config{
			PrivateKey:  srvkey,
			NoDiscovery: true,
		},
		newTransport: func(fd net.Conn) transport { return newTestTransport(clientpub, fd) },
		log:          log.New(),
		checkPeerInRaft: func(node *enode.Node) bool {
			return false
		},
	}
	if err := srv.Start(); err != nil {
		t.Fatalf("couldn't start server: %v", err)
	}
	defer srv.Stop()
	p1, _ := net.Pipe()
	err := srv.SetupConn(p1, inboundConn, clientNode)

	assert.IsType(t, &peerError{}, err)
	perr := err.(*peerError)
	t.Log(perr.Error())
	assert.Equal(t, errNotInRaftCluster, perr.code)
}

func TestServerSetupConn_whenNotPermissioned(t *testing.T) {
	tmpDir, err := ioutil.TempDir("", "")
	if err != nil {
		t.Fatal(err)
	}
	defer func() { _ = os.RemoveAll(tmpDir) }()
	if err := ioutil.WriteFile(path.Join(tmpDir, params.PERMISSIONED_CONFIG), []byte("[]"), 0644); err != nil {
		t.Fatal(err)
	}
	var (
		clientkey, srvkey = newkey(), newkey()
		clientpub         = &clientkey.PublicKey
	)
	clientNode := enode.NewV4(clientpub, nil, 0, 0)
	srv := &Server{
		Config: Config{
			PrivateKey:           srvkey,
			NoDiscovery:          true,
			DataDir:              tmpDir,
			EnableNodePermission: true,
		},
		newTransport: func(fd net.Conn) transport { return newTestTransport(clientpub, fd) },
		log:          log.New(),
	}
	if err := srv.Start(); err != nil {
		t.Fatalf("couldn't start server: %v", err)
	}
	defer srv.Stop()
	p1, _ := net.Pipe()
	err = srv.SetupConn(p1, inboundConn, clientNode)

	assert.IsType(t, &peerError{}, err)
	perr := err.(*peerError)
	t.Log(perr.Error())
	assert.Equal(t, errPermissionDenied, perr.code)
}

type setupTransport struct {
	pubkey            *ecdsa.PublicKey
	encHandshakeErr   error
	phs               protoHandshake
	protoHandshakeErr error

	calls    string
	closeErr error
}

func (c *setupTransport) doEncHandshake(prv *ecdsa.PrivateKey, dialDest *ecdsa.PublicKey) (*ecdsa.PublicKey, error) {
	c.calls += "doEncHandshake,"
	return c.pubkey, c.encHandshakeErr
}

func (c *setupTransport) doProtoHandshake(our *protoHandshake) (*protoHandshake, error) {
	c.calls += "doProtoHandshake,"
	if c.protoHandshakeErr != nil {
		return nil, c.protoHandshakeErr
	}
	return &c.phs, nil
}
func (c *setupTransport) close(err error) {
	c.calls += "close,"
	c.closeErr = err
}

// setupConn shouldn't write to/read from the connection.
func (c *setupTransport) WriteMsg(Msg) error {
	panic("WriteMsg called on setupTransport")
}
func (c *setupTransport) ReadMsg() (Msg, error) {
	panic("ReadMsg called on setupTransport")
}

func newkey() *ecdsa.PrivateKey {
	key, err := crypto.GenerateKey()
	if err != nil {
		panic("couldn't generate key: " + err.Error())
	}
	return key
}

func randomID() (id enode.ID) {
	for i := range id {
		id[i] = byte(rand.Intn(255))
	}
	return id
}

// This test checks that inbound connections are throttled by IP.
func TestServerInboundThrottle(t *testing.T) {
	const timeout = 5 * time.Second
	newTransportCalled := make(chan struct{})
	srv := &Server{
		Config: Config{
			PrivateKey:  newkey(),
			ListenAddr:  "127.0.0.1:0",
			MaxPeers:    10,
			NoDial:      true,
			NoDiscovery: true,
			Protocols:   []Protocol{discard},
			Logger:      testlog.Logger(t, log.LvlTrace),
		},
		newTransport: func(fd net.Conn) transport {
			newTransportCalled <- struct{}{}
			return newRLPX(fd)
		},
		listenFunc: func(network, laddr string) (net.Listener, error) {
			fakeAddr := &net.TCPAddr{IP: net.IP{95, 33, 21, 2}, Port: 4444}
			return listenFakeAddr(network, laddr, fakeAddr)
		},
	}
	if err := srv.Start(); err != nil {
		t.Fatal("can't start: ", err)
	}
	defer srv.Stop()

	// Dial the test server.
	conn, err := net.DialTimeout("tcp", srv.ListenAddr, timeout)
	if err != nil {
		t.Fatalf("could not dial: %v", err)
	}
	select {
	case <-newTransportCalled:
		// OK
	case <-time.After(timeout):
		t.Error("newTransport not called")
	}
	conn.Close()

	// Dial again. This time the server should close the connection immediately.
	connClosed := make(chan struct{})
	conn, err = net.DialTimeout("tcp", srv.ListenAddr, timeout)
	if err != nil {
		t.Fatalf("could not dial: %v", err)
	}
	defer conn.Close()
	go func() {
		conn.SetDeadline(time.Now().Add(timeout))
		buf := make([]byte, 10)
		if n, err := conn.Read(buf); err != io.EOF || n != 0 {
			t.Errorf("expected io.EOF and n == 0, got error %q and n == %d", err, n)
		}
		connClosed <- struct{}{}
	}()
	select {
	case <-connClosed:
		// OK
	case <-newTransportCalled:
		t.Error("newTransport called for second attempt")
	case <-time.After(timeout):
		t.Error("connection not closed within timeout")
	}
}

func listenFakeAddr(network, laddr string, remoteAddr net.Addr) (net.Listener, error) {
	l, err := net.Listen(network, laddr)
	if err == nil {
		l = &fakeAddrListener{l, remoteAddr}
	}
	return l, err
}

// fakeAddrListener is a listener that creates connections with a mocked remote address.
type fakeAddrListener struct {
	net.Listener
	remoteAddr net.Addr
}

type fakeAddrConn struct {
	net.Conn
	remoteAddr net.Addr
}

func (l *fakeAddrListener) Accept() (net.Conn, error) {
	c, err := l.Listener.Accept()
	if err != nil {
		return nil, err
	}
	return &fakeAddrConn{c, l.remoteAddr}, nil
}

func (c *fakeAddrConn) RemoteAddr() net.Addr {
	return c.remoteAddr
}