internal/socket/socket_test.go - net - Git at Google

 // Copyright 2017 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 //go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris || windows || zos
 // +build aix darwin dragonfly freebsd linux netbsd openbsd solaris windows zos

 package socket_test

 import (
 	"bytes"
 	"fmt"
 	"io/ioutil"
 	"net"
 	"os"
 	"os/exec"
 	"path/filepath"
 	"runtime"
 	"strings"
 	"syscall"
 	"testing"

 	"golang.org/x/net/internal/socket"
 	"golang.org/x/net/nettest"
 )

 func TestSocket(t *testing.T) {
 	t.Run("Option", func(t *testing.T) {
 		testSocketOption(t, &socket.Option{Level: syscall.SOL_SOCKET, Name: syscall.SO_RCVBUF, Len: 4})
 	})
 }

 func testSocketOption(t *testing.T, so *socket.Option) {
 	c, err := nettest.NewLocalPacketListener("udp")
 	if err != nil {
 		t.Skipf("not supported on %s/%s: %v", runtime.GOOS, runtime.GOARCH, err)
 	}
 	defer c.Close()
 	cc, err := socket.NewConn(c.(net.Conn))
 	if err != nil {
 		t.Fatal(err)
 	}
 	const N = 2048
 	if err := so.SetInt(cc, N); err != nil {
 		t.Fatal(err)
 	}
 	n, err := so.GetInt(cc)
 	if err != nil {
 		t.Fatal(err)
 	}
 	if n < N {
 		t.Fatalf("got %d; want greater than or equal to %d", n, N)
 	}
 }

 type mockControl struct {
 	Level int
 	Type  int
 	Data  []byte
 }

 func TestControlMessage(t *testing.T) {
 	switch runtime.GOOS {
 	case "windows":
 		t.Skipf("not supported on %s", runtime.GOOS)
 	}

 	for _, tt := range []struct {
 		cs []mockControl
 	}{
 		{
 			[]mockControl{
 				{Level: 1, Type: 1},
 			},
 		},
 		{
 			[]mockControl{
 				{Level: 2, Type: 2, Data: []byte{0xfe}},
 			},
 		},
 		{
 			[]mockControl{
 				{Level: 3, Type: 3, Data: []byte{0xfe, 0xff, 0xff, 0xfe}},
 			},
 		},
 		{
 			[]mockControl{
 				{Level: 4, Type: 4, Data: []byte{0xfe, 0xff, 0xff, 0xfe, 0xfe, 0xff, 0xff, 0xfe}},
 			},
 		},
 		{
 			[]mockControl{
 				{Level: 4, Type: 4, Data: []byte{0xfe, 0xff, 0xff, 0xfe, 0xfe, 0xff, 0xff, 0xfe}},
 				{Level: 2, Type: 2, Data: []byte{0xfe}},
 			},
 		},
 	} {
 		var w []byte
 		var tailPadLen int
 		mm := socket.NewControlMessage([]int{0})
 		for i, c := range tt.cs {
 			m := socket.NewControlMessage([]int{len(c.Data)})
 			l := len(m) - len(mm)
 			if i == len(tt.cs)-1 && l > len(c.Data) {
 				tailPadLen = l - len(c.Data)
 			}
 			w = append(w, m...)
 		}

 		var err error
 		ww := make([]byte, len(w))
 		copy(ww, w)
 		m := socket.ControlMessage(ww)
 		for _, c := range tt.cs {
 			if err = m.MarshalHeader(c.Level, c.Type, len(c.Data)); err != nil {
 				t.Fatalf("(%v).MarshalHeader() = %v", tt.cs, err)
 			}
 			copy(m.Data(len(c.Data)), c.Data)
 			m = m.Next(len(c.Data))
 		}
 		m = socket.ControlMessage(w)
 		for _, c := range tt.cs {
 			m, err = m.Marshal(c.Level, c.Type, c.Data)
 			if err != nil {
 				t.Fatalf("(%v).Marshal() = %v", tt.cs, err)
 			}
 		}
 		if !bytes.Equal(ww, w) {
 			t.Fatalf("got %#v; want %#v", ww, w)
 		}

 		ws := [][]byte{w}
 		if tailPadLen > 0 {
 			// Test a message with no tail padding.
 			nopad := w[:len(w)-tailPadLen]
 			ws = append(ws, [][]byte{nopad}...)
 		}
 		for _, w := range ws {
 			ms, err := socket.ControlMessage(w).Parse()
 			if err != nil {
 				t.Fatalf("(%v).Parse() = %v", tt.cs, err)
 			}
 			for i, m := range ms {
 				lvl, typ, dataLen, err := m.ParseHeader()
 				if err != nil {
 					t.Fatalf("(%v).ParseHeader() = %v", tt.cs, err)
 				}
 				if lvl != tt.cs[i].Level || typ != tt.cs[i].Type || dataLen != len(tt.cs[i].Data) {
 					t.Fatalf("%v: got %d, %d, %d; want %d, %d, %d", tt.cs[i], lvl, typ, dataLen, tt.cs[i].Level, tt.cs[i].Type, len(tt.cs[i].Data))
 				}
 			}
 		}
 	}
 }

 func TestUDP(t *testing.T) {
 	switch runtime.GOOS {
 	case "windows":
 		t.Skipf("not supported on %s", runtime.GOOS)
 	}

 	c, err := nettest.NewLocalPacketListener("udp")
 	if err != nil {
 		t.Skipf("not supported on %s/%s: %v", runtime.GOOS, runtime.GOARCH, err)
 	}
 	defer c.Close()
 	// test that wrapped connections work with NewConn too
 	type wrappedConn struct{ *net.UDPConn }
 	cc, err := socket.NewConn(&wrappedConn{c.(*net.UDPConn)})
 	if err != nil {
 		t.Fatal(err)
 	}

 	// create a dialed connection talking (only) to c/cc
 	cDialed, err := net.Dial("udp", c.LocalAddr().String())
 	if err != nil {
 		t.Fatal(err)
 	}
 	ccDialed, err := socket.NewConn(cDialed)
 	if err != nil {
 		t.Fatal(err)
 	}

 	t.Run("Message", func(t *testing.T) {
 		data := []byte("HELLO-R-U-THERE")
 		wm := socket.Message{
 			Buffers: bytes.SplitAfter(data, []byte("-")),
 			Addr:    c.LocalAddr(),
 		}
 		if err := cc.SendMsg(&wm, 0); err != nil {
 			t.Fatal(err)
 		}
 		b := make([]byte, 32)
 		rm := socket.Message{
 			Buffers: [][]byte{b[:1], b[1:3], b[3:7], b[7:11], b[11:]},
 		}
 		if err := cc.RecvMsg(&rm, 0); err != nil {
 			t.Fatal(err)
 		}
 		if !bytes.Equal(b[:rm.N], data) {
 			t.Fatalf("got %#v; want %#v", b[:rm.N], data)
 		}
 	})
 	t.Run("Message-dialed", func(t *testing.T) {
 		data := []byte("HELLO-R-U-THERE")
 		wm := socket.Message{
 			Buffers: bytes.SplitAfter(data, []byte("-")),
 			Addr:    nil,
 		}
 		if err := ccDialed.SendMsg(&wm, 0); err != nil {
 			t.Fatal(err)
 		}
 		b := make([]byte, 32)
 		rm := socket.Message{
 			Buffers: [][]byte{b[:1], b[1:3], b[3:7], b[7:11], b[11:]},
 		}
 		if err := cc.RecvMsg(&rm, 0); err != nil {
 			t.Fatal(err)
 		}
 		if !bytes.Equal(b[:rm.N], data) {
 			t.Fatalf("got %#v; want %#v", b[:rm.N], data)
 		}
 	})

 	switch runtime.GOOS {
 	case "android", "linux":
 		t.Run("Messages", func(t *testing.T) {
 			data := []byte("HELLO-R-U-THERE")
 			wmbs := bytes.SplitAfter(data, []byte("-"))
 			wms := []socket.Message{
 				{Buffers: wmbs[:1], Addr: c.LocalAddr()},
 				{Buffers: wmbs[1:], Addr: c.LocalAddr()},
 			}
 			n, err := cc.SendMsgs(wms, 0)
 			if err != nil {
 				t.Fatal(err)
 			}
 			if n != len(wms) {
 				t.Fatalf("got %d; want %d", n, len(wms))
 			}
 			b := make([]byte, 32)
 			rmbs := [][][]byte{{b[:len(wmbs[0])]}, {b[len(wmbs[0]):]}}
 			rms := []socket.Message{
 				{Buffers: rmbs[0]},
 				{Buffers: rmbs[1]},
 			}
 			n, err = cc.RecvMsgs(rms, 0)
 			if err != nil {
 				t.Fatal(err)
 			}
 			if n != len(rms) {
 				t.Fatalf("got %d; want %d", n, len(rms))
 			}
 			nn := 0
 			for i := 0; i < n; i++ {
 				nn += rms[i].N
 			}
 			if !bytes.Equal(b[:nn], data) {
 				t.Fatalf("got %#v; want %#v", b[:nn], data)
 			}
 		})
 		t.Run("Messages-undialed-no-dst", func(t *testing.T) {
 			// sending without destination address should fail.
 			// This checks that the internally recycled buffers are reset correctly.
 			data := []byte("HELLO-R-U-THERE")
 			wmbs := bytes.SplitAfter(data, []byte("-"))
 			wms := []socket.Message{
 				{Buffers: wmbs[:1], Addr: nil},
 				{Buffers: wmbs[1:], Addr: nil},
 			}
 			n, err := cc.SendMsgs(wms, 0)
 			if n != 0 && err == nil {
 				t.Fatal("expected error, destination address required")
 			}
 		})
 		t.Run("Messages-dialed", func(t *testing.T) {
 			data := []byte("HELLO-R-U-THERE")
 			wmbs := bytes.SplitAfter(data, []byte("-"))
 			wms := []socket.Message{
 				{Buffers: wmbs[:1], Addr: nil},
 				{Buffers: wmbs[1:], Addr: nil},
 			}
 			n, err := ccDialed.SendMsgs(wms, 0)
 			if err != nil {
 				t.Fatal(err)
 			}
 			if n != len(wms) {
 				t.Fatalf("got %d; want %d", n, len(wms))
 			}
 			b := make([]byte, 32)
 			rmbs := [][][]byte{{b[:len(wmbs[0])]}, {b[len(wmbs[0]):]}}
 			rms := []socket.Message{
 				{Buffers: rmbs[0]},
 				{Buffers: rmbs[1]},
 			}
 			n, err = cc.RecvMsgs(rms, 0)
 			if err != nil {
 				t.Fatal(err)
 			}
 			if n != len(rms) {
 				t.Fatalf("got %d; want %d", n, len(rms))
 			}
 			nn := 0
 			for i := 0; i < n; i++ {
 				nn += rms[i].N
 			}
 			if !bytes.Equal(b[:nn], data) {
 				t.Fatalf("got %#v; want %#v", b[:nn], data)
 			}
 		})
 	}

 	// The behavior of transmission for zero byte paylaod depends
 	// on each platform implementation. Some may transmit only
 	// protocol header and options, other may transmit nothing.
 	// We test only that SendMsg and SendMsgs will not crash with
 	// empty buffers.
 	wm := socket.Message{
 		Buffers: [][]byte{{}},
 		Addr:    c.LocalAddr(),
 	}
 	cc.SendMsg(&wm, 0)
 	wms := []socket.Message{
 		{Buffers: [][]byte{{}}, Addr: c.LocalAddr()},
 	}
 	cc.SendMsgs(wms, 0)
 }

 func BenchmarkUDP(b *testing.B) {
 	c, err := nettest.NewLocalPacketListener("udp")
 	if err != nil {
 		b.Skipf("not supported on %s/%s: %v", runtime.GOOS, runtime.GOARCH, err)
 	}
 	defer c.Close()
 	cc, err := socket.NewConn(c.(net.Conn))
 	if err != nil {
 		b.Fatal(err)
 	}
 	data := []byte("HELLO-R-U-THERE")
 	wm := socket.Message{
 		Buffers: [][]byte{data},
 		Addr:    c.LocalAddr(),
 	}
 	rm := socket.Message{
 		Buffers: [][]byte{make([]byte, 128)},
 		OOB:     make([]byte, 128),
 	}

 	for M := 1; M <= 1<<9; M = M << 1 {
 		b.Run(fmt.Sprintf("Iter-%d", M), func(b *testing.B) {
 			for i := 0; i < b.N; i++ {
 				for j := 0; j < M; j++ {
 					if err := cc.SendMsg(&wm, 0); err != nil {
 						b.Fatal(err)
 					}
 					if err := cc.RecvMsg(&rm, 0); err != nil {
 						b.Fatal(err)
 					}
 				}
 			}
 		})
 		switch runtime.GOOS {
 		case "android", "linux":
 			wms := make([]socket.Message, M)
 			for i := range wms {
 				wms[i].Buffers = [][]byte{data}
 				wms[i].Addr = c.LocalAddr()
 			}
 			rms := make([]socket.Message, M)
 			for i := range rms {
 				rms[i].Buffers = [][]byte{make([]byte, 128)}
 				rms[i].OOB = make([]byte, 128)
 			}
 			b.Run(fmt.Sprintf("Batch-%d", M), func(b *testing.B) {
 				for i := 0; i < b.N; i++ {
 					if _, err := cc.SendMsgs(wms, 0); err != nil {
 						b.Fatal(err)
 					}
 					if _, err := cc.RecvMsgs(rms, 0); err != nil {
 						b.Fatal(err)
 					}
 				}
 			})
 		}
 	}
 }

 func TestRace(t *testing.T) {
 	tests := []string{
 		`
 package main
 import (
 	"log"
 	"net"

 	"golang.org/x/net/ipv4"
 )

 var g byte

 func main() {
 	c, err := net.ListenPacket("udp", "127.0.0.1:0")
 	if err != nil {
 		log.Fatalf("ListenPacket: %v", err)
 	}
 	cc := ipv4.NewPacketConn(c)
 	sync := make(chan bool)
 	src := make([]byte, 100)
 	dst := make([]byte, 100)
 	go func() {
 		if _, err := cc.WriteTo(src, nil, c.LocalAddr()); err != nil {
 			log.Fatalf("WriteTo: %v", err)
 		}
 	}()
 	go func() {
 		if _, _, _, err := cc.ReadFrom(dst); err != nil {
 			log.Fatalf("ReadFrom: %v", err)
 		}
 		sync <- true
 	}()
 	g = dst[0]
 	<-sync
 }
 `,
 		`
 package main
 import (
 	"log"
 	"net"

 	"golang.org/x/net/ipv4"
 )

 func main() {
 	c, err := net.ListenPacket("udp", "127.0.0.1:0")
 	if err != nil {
 		log.Fatalf("ListenPacket: %v", err)
 	}
 	cc := ipv4.NewPacketConn(c)
 	sync := make(chan bool)
 	src := make([]byte, 100)
 	dst := make([]byte, 100)
 	go func() {
 		if _, err := cc.WriteTo(src, nil, c.LocalAddr()); err != nil {
 			log.Fatalf("WriteTo: %v", err)
 		}
 		sync <- true
 	}()
 	src[0] = 0
 	go func() {
 		if _, _, _, err := cc.ReadFrom(dst); err != nil {
 			log.Fatalf("ReadFrom: %v", err)
 		}
 	}()
 	<-sync
 }
 `,
 	}
 	platforms := map[string]bool{
 		"linux/amd64":   true,
 		"linux/ppc64le": true,
 		"linux/arm64":   true,
 	}
 	if !platforms[runtime.GOOS+"/"+runtime.GOARCH] {
 		t.Skip("skipping test on non-race-enabled host.")
 	}
 	dir, err := ioutil.TempDir("", "testrace")
 	if err != nil {
 		t.Fatalf("failed to create temp directory: %v", err)
 	}
 	defer os.RemoveAll(dir)
 	goBinary := filepath.Join(runtime.GOROOT(), "bin", "go")
 	t.Logf("%s version", goBinary)
 	got, err := exec.Command(goBinary, "version").CombinedOutput()
 	if len(got) > 0 {
 		t.Logf("%s", got)
 	}
 	if err != nil {
 		t.Fatalf("go version failed: %v", err)
 	}
 	for i, test := range tests {
 		t.Run(fmt.Sprintf("test %d", i), func(t *testing.T) {
 			src := filepath.Join(dir, fmt.Sprintf("test%d.go", i))
 			if err := ioutil.WriteFile(src, []byte(test), 0644); err != nil {
 				t.Fatalf("failed to write file: %v", err)
 			}
 			t.Logf("%s run -race %s", goBinary, src)
 			got, err := exec.Command(goBinary, "run", "-race", src).CombinedOutput()
 			if len(got) > 0 {
 				t.Logf("%s", got)
 			}
 			if strings.Contains(string(got), "-race requires cgo") {
 				t.Log("CGO is not enabled so can't use -race")
 			} else if !strings.Contains(string(got), "WARNING: DATA RACE") {
 				t.Errorf("race not detected for test %d: err:%v", i, err)
 			}
 		})
 	}
 }
	// Copyright 2017 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	//go:build aix \|\| darwin \|\| dragonfly \|\| freebsd \|\| linux \|\| netbsd \|\| openbsd \|\| solaris \|\| windows \|\| zos
	// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris windows zos

	package socket_test

	import (
	"bytes"
	"fmt"
	"io/ioutil"
	"net"
	"os"
	"os/exec"
	"path/filepath"
	"runtime"
	"strings"
	"syscall"
	"testing"

	"golang.org/x/net/internal/socket"
	"golang.org/x/net/nettest"
	)

	func TestSocket(t *testing.T) {
	t.Run("Option", func(t *testing.T) {
	testSocketOption(t, &socket.Option{Level: syscall.SOL_SOCKET, Name: syscall.SO_RCVBUF, Len: 4})
	})
	}

	func testSocketOption(t testing.T, so socket.Option) {
	c, err := nettest.NewLocalPacketListener("udp")
	if err != nil {
	t.Skipf("not supported on %s/%s: %v", runtime.GOOS, runtime.GOARCH, err)
	}
	defer c.Close()
	cc, err := socket.NewConn(c.(net.Conn))
	if err != nil {
	t.Fatal(err)
	}
	const N = 2048
	if err := so.SetInt(cc, N); err != nil {
	t.Fatal(err)
	}
	n, err := so.GetInt(cc)
	if err != nil {
	t.Fatal(err)
	}
	if n < N {
	t.Fatalf("got %d; want greater than or equal to %d", n, N)
	}
	}

	type mockControl struct {
	Level int
	Type int
	Data []byte
	}

	func TestControlMessage(t *testing.T) {
	switch runtime.GOOS {
	case "windows":
	t.Skipf("not supported on %s", runtime.GOOS)
	}

	for _, tt := range []struct {
	cs []mockControl
	}{
	{
	[]mockControl{
	{Level: 1, Type: 1},
	},
	},
	{
	[]mockControl{
	{Level: 2, Type: 2, Data: []byte{0xfe}},
	},
	},
	{
	[]mockControl{
	{Level: 3, Type: 3, Data: []byte{0xfe, 0xff, 0xff, 0xfe}},
	},
	},
	{
	[]mockControl{
	{Level: 4, Type: 4, Data: []byte{0xfe, 0xff, 0xff, 0xfe, 0xfe, 0xff, 0xff, 0xfe}},
	},
	},
	{
	[]mockControl{
	{Level: 4, Type: 4, Data: []byte{0xfe, 0xff, 0xff, 0xfe, 0xfe, 0xff, 0xff, 0xfe}},
	{Level: 2, Type: 2, Data: []byte{0xfe}},
	},
	},
	} {
	var w []byte
	var tailPadLen int
	mm := socket.NewControlMessage([]int{0})
	for i, c := range tt.cs {
	m := socket.NewControlMessage([]int{len(c.Data)})
	l := len(m) - len(mm)
	if i == len(tt.cs)-1 && l > len(c.Data) {
	tailPadLen = l - len(c.Data)
	}
	w = append(w, m...)
	}

	var err error
	ww := make([]byte, len(w))
	copy(ww, w)
	m := socket.ControlMessage(ww)
	for _, c := range tt.cs {
	if err = m.MarshalHeader(c.Level, c.Type, len(c.Data)); err != nil {
	t.Fatalf("(%v).MarshalHeader() = %v", tt.cs, err)
	}
	copy(m.Data(len(c.Data)), c.Data)
	m = m.Next(len(c.Data))
	}
	m = socket.ControlMessage(w)
	for _, c := range tt.cs {
	m, err = m.Marshal(c.Level, c.Type, c.Data)
	if err != nil {
	t.Fatalf("(%v).Marshal() = %v", tt.cs, err)
	}
	}
	if !bytes.Equal(ww, w) {
	t.Fatalf("got %#v; want %#v", ww, w)
	}

	ws := [][]byte{w}
	if tailPadLen > 0 {
	// Test a message with no tail padding.
	nopad := w[:len(w)-tailPadLen]
	ws = append(ws, [][]byte{nopad}...)
	}
	for _, w := range ws {
	ms, err := socket.ControlMessage(w).Parse()
	if err != nil {
	t.Fatalf("(%v).Parse() = %v", tt.cs, err)
	}
	for i, m := range ms {
	lvl, typ, dataLen, err := m.ParseHeader()
	if err != nil {
	t.Fatalf("(%v).ParseHeader() = %v", tt.cs, err)
	}
	if lvl != tt.cs[i].Level \|\| typ != tt.cs[i].Type \|\| dataLen != len(tt.cs[i].Data) {
	t.Fatalf("%v: got %d, %d, %d; want %d, %d, %d", tt.cs[i], lvl, typ, dataLen, tt.cs[i].Level, tt.cs[i].Type, len(tt.cs[i].Data))
	}
	}
	}
	}
	}

	func TestUDP(t *testing.T) {
	switch runtime.GOOS {
	case "windows":
	t.Skipf("not supported on %s", runtime.GOOS)
	}

	c, err := nettest.NewLocalPacketListener("udp")
	if err != nil {
	t.Skipf("not supported on %s/%s: %v", runtime.GOOS, runtime.GOARCH, err)
	}
	defer c.Close()
	// test that wrapped connections work with NewConn too
	type wrappedConn struct{ *net.UDPConn }
	cc, err := socket.NewConn(&wrappedConn{c.(*net.UDPConn)})
	if err != nil {
	t.Fatal(err)
	}

	// create a dialed connection talking (only) to c/cc
	cDialed, err := net.Dial("udp", c.LocalAddr().String())
	if err != nil {
	t.Fatal(err)
	}
	ccDialed, err := socket.NewConn(cDialed)
	if err != nil {
	t.Fatal(err)
	}

	t.Run("Message", func(t *testing.T) {
	data := []byte("HELLO-R-U-THERE")
	wm := socket.Message{
	Buffers: bytes.SplitAfter(data, []byte("-")),
	Addr: c.LocalAddr(),
	}
	if err := cc.SendMsg(&wm, 0); err != nil {
	t.Fatal(err)
	}
	b := make([]byte, 32)
	rm := socket.Message{
	Buffers: [][]byte{b[:1], b[1:3], b[3:7], b[7:11], b[11:]},
	}
	if err := cc.RecvMsg(&rm, 0); err != nil {
	t.Fatal(err)
	}
	if !bytes.Equal(b[:rm.N], data) {
	t.Fatalf("got %#v; want %#v", b[:rm.N], data)
	}
	})
	t.Run("Message-dialed", func(t *testing.T) {
	data := []byte("HELLO-R-U-THERE")
	wm := socket.Message{
	Buffers: bytes.SplitAfter(data, []byte("-")),
	Addr: nil,
	}
	if err := ccDialed.SendMsg(&wm, 0); err != nil {
	t.Fatal(err)
	}
	b := make([]byte, 32)
	rm := socket.Message{
	Buffers: [][]byte{b[:1], b[1:3], b[3:7], b[7:11], b[11:]},
	}
	if err := cc.RecvMsg(&rm, 0); err != nil {
	t.Fatal(err)
	}
	if !bytes.Equal(b[:rm.N], data) {
	t.Fatalf("got %#v; want %#v", b[:rm.N], data)
	}
	})

	switch runtime.GOOS {
	case "android", "linux":
	t.Run("Messages", func(t *testing.T) {
	data := []byte("HELLO-R-U-THERE")
	wmbs := bytes.SplitAfter(data, []byte("-"))
	wms := []socket.Message{
	{Buffers: wmbs[:1], Addr: c.LocalAddr()},
	{Buffers: wmbs[1:], Addr: c.LocalAddr()},
	}
	n, err := cc.SendMsgs(wms, 0)
	if err != nil {
	t.Fatal(err)
	}
	if n != len(wms) {
	t.Fatalf("got %d; want %d", n, len(wms))
	}
	b := make([]byte, 32)
	rmbs := [][][]byte{{b[:len(wmbs[0])]}, {b[len(wmbs[0]):]}}
	rms := []socket.Message{
	{Buffers: rmbs[0]},
	{Buffers: rmbs[1]},
	}
	n, err = cc.RecvMsgs(rms, 0)
	if err != nil {
	t.Fatal(err)
	}
	if n != len(rms) {
	t.Fatalf("got %d; want %d", n, len(rms))
	}
	nn := 0
	for i := 0; i < n; i++ {
	nn += rms[i].N
	}
	if !bytes.Equal(b[:nn], data) {
	t.Fatalf("got %#v; want %#v", b[:nn], data)
	}
	})
	t.Run("Messages-undialed-no-dst", func(t *testing.T) {
	// sending without destination address should fail.
	// This checks that the internally recycled buffers are reset correctly.
	data := []byte("HELLO-R-U-THERE")
	wmbs := bytes.SplitAfter(data, []byte("-"))
	wms := []socket.Message{
	{Buffers: wmbs[:1], Addr: nil},
	{Buffers: wmbs[1:], Addr: nil},
	}
	n, err := cc.SendMsgs(wms, 0)
	if n != 0 && err == nil {
	t.Fatal("expected error, destination address required")
	}
	})
	t.Run("Messages-dialed", func(t *testing.T) {
	data := []byte("HELLO-R-U-THERE")
	wmbs := bytes.SplitAfter(data, []byte("-"))
	wms := []socket.Message{
	{Buffers: wmbs[:1], Addr: nil},
	{Buffers: wmbs[1:], Addr: nil},
	}
	n, err := ccDialed.SendMsgs(wms, 0)
	if err != nil {
	t.Fatal(err)
	}
	if n != len(wms) {
	t.Fatalf("got %d; want %d", n, len(wms))
	}
	b := make([]byte, 32)
	rmbs := [][][]byte{{b[:len(wmbs[0])]}, {b[len(wmbs[0]):]}}
	rms := []socket.Message{
	{Buffers: rmbs[0]},
	{Buffers: rmbs[1]},
	}
	n, err = cc.RecvMsgs(rms, 0)
	if err != nil {
	t.Fatal(err)
	}
	if n != len(rms) {
	t.Fatalf("got %d; want %d", n, len(rms))
	}
	nn := 0
	for i := 0; i < n; i++ {
	nn += rms[i].N
	}
	if !bytes.Equal(b[:nn], data) {
	t.Fatalf("got %#v; want %#v", b[:nn], data)
	}
	})
	}

	// The behavior of transmission for zero byte paylaod depends
	// on each platform implementation. Some may transmit only
	// protocol header and options, other may transmit nothing.
	// We test only that SendMsg and SendMsgs will not crash with
	// empty buffers.
	wm := socket.Message{
	Buffers: [][]byte{{}},
	Addr: c.LocalAddr(),
	}
	cc.SendMsg(&wm, 0)
	wms := []socket.Message{
	{Buffers: [][]byte{{}}, Addr: c.LocalAddr()},
	}
	cc.SendMsgs(wms, 0)
	}

	func BenchmarkUDP(b *testing.B) {
	c, err := nettest.NewLocalPacketListener("udp")
	if err != nil {
	b.Skipf("not supported on %s/%s: %v", runtime.GOOS, runtime.GOARCH, err)
	}
	defer c.Close()
	cc, err := socket.NewConn(c.(net.Conn))
	if err != nil {
	b.Fatal(err)
	}
	data := []byte("HELLO-R-U-THERE")
	wm := socket.Message{
	Buffers: [][]byte{data},
	Addr: c.LocalAddr(),
	}
	rm := socket.Message{
	Buffers: [][]byte{make([]byte, 128)},
	OOB: make([]byte, 128),
	}

	for M := 1; M <= 1<<9; M = M << 1 {
	b.Run(fmt.Sprintf("Iter-%d", M), func(b *testing.B) {
	for i := 0; i < b.N; i++ {
	for j := 0; j < M; j++ {
	if err := cc.SendMsg(&wm, 0); err != nil {
	b.Fatal(err)
	}
	if err := cc.RecvMsg(&rm, 0); err != nil {
	b.Fatal(err)
	}
	}
	}
	})
	switch runtime.GOOS {
	case "android", "linux":
	wms := make([]socket.Message, M)
	for i := range wms {
	wms[i].Buffers = [][]byte{data}
	wms[i].Addr = c.LocalAddr()
	}
	rms := make([]socket.Message, M)
	for i := range rms {
	rms[i].Buffers = [][]byte{make([]byte, 128)}
	rms[i].OOB = make([]byte, 128)
	}
	b.Run(fmt.Sprintf("Batch-%d", M), func(b *testing.B) {
	for i := 0; i < b.N; i++ {
	if _, err := cc.SendMsgs(wms, 0); err != nil {
	b.Fatal(err)
	}
	if _, err := cc.RecvMsgs(rms, 0); err != nil {
	b.Fatal(err)
	}
	}
	})
	}
	}
	}

	func TestRace(t *testing.T) {
	tests := []string{
	`
	package main
	import (
	"log"
	"net"

	"golang.org/x/net/ipv4"
	)

	var g byte

	func main() {
	c, err := net.ListenPacket("udp", "127.0.0.1:0")
	if err != nil {
	log.Fatalf("ListenPacket: %v", err)
	}
	cc := ipv4.NewPacketConn(c)
	sync := make(chan bool)
	src := make([]byte, 100)
	dst := make([]byte, 100)
	go func() {
	if _, err := cc.WriteTo(src, nil, c.LocalAddr()); err != nil {
	log.Fatalf("WriteTo: %v", err)
	}
	}()
	go func() {
	if _, _, _, err := cc.ReadFrom(dst); err != nil {
	log.Fatalf("ReadFrom: %v", err)
	}
	sync <- true
	}()
	g = dst[0]
	<-sync
	}
	`,
	`
	package main
	import (
	"log"
	"net"

	"golang.org/x/net/ipv4"
	)

	func main() {
	c, err := net.ListenPacket("udp", "127.0.0.1:0")
	if err != nil {
	log.Fatalf("ListenPacket: %v", err)
	}
	cc := ipv4.NewPacketConn(c)
	sync := make(chan bool)
	src := make([]byte, 100)
	dst := make([]byte, 100)
	go func() {
	if _, err := cc.WriteTo(src, nil, c.LocalAddr()); err != nil {
	log.Fatalf("WriteTo: %v", err)
	}
	sync <- true
	}()
	src[0] = 0
	go func() {
	if _, _, _, err := cc.ReadFrom(dst); err != nil {
	log.Fatalf("ReadFrom: %v", err)
	}
	}()
	<-sync
	}
	`,
	}
	platforms := map[string]bool{
	"linux/amd64": true,
	"linux/ppc64le": true,
	"linux/arm64": true,
	}
	if !platforms[runtime.GOOS+"/"+runtime.GOARCH] {
	t.Skip("skipping test on non-race-enabled host.")
	}
	dir, err := ioutil.TempDir("", "testrace")
	if err != nil {
	t.Fatalf("failed to create temp directory: %v", err)
	}
	defer os.RemoveAll(dir)
	goBinary := filepath.Join(runtime.GOROOT(), "bin", "go")
	t.Logf("%s version", goBinary)
	got, err := exec.Command(goBinary, "version").CombinedOutput()
	if len(got) > 0 {
	t.Logf("%s", got)
	}
	if err != nil {
	t.Fatalf("go version failed: %v", err)
	}
	for i, test := range tests {
	t.Run(fmt.Sprintf("test %d", i), func(t *testing.T) {
	src := filepath.Join(dir, fmt.Sprintf("test%d.go", i))
	if err := ioutil.WriteFile(src, []byte(test), 0644); err != nil {
	t.Fatalf("failed to write file: %v", err)
	}
	t.Logf("%s run -race %s", goBinary, src)
	got, err := exec.Command(goBinary, "run", "-race", src).CombinedOutput()
	if len(got) > 0 {
	t.Logf("%s", got)
	}
	if strings.Contains(string(got), "-race requires cgo") {
	t.Log("CGO is not enabled so can't use -race")
	} else if !strings.Contains(string(got), "WARNING: DATA RACE") {
	t.Errorf("race not detected for test %d: err:%v", i, err)
	}
	})
	}
	}