internal/socket: new package

This is a counterpart of https://go-review.googlesource.com/37039.

This change introduces a package that provides a portable interface
for the manipulation of sockets using either syscall.Conn and
syscall.RawConn interfaces or the internal/netreflect package
appropriately.

The package ensures that a package using this works with all supported
versions of the Go standard library.

Updates golang/go#19051.

Change-Id: Ib72ea369e6839e77fed6e35b9aedc364e73c51cb
Reviewed-on: https://go-review.googlesource.com/37035
Reviewed-by: Ian Lance Taylor <iant@golang.org>

internal/socket/error_unix.go

@@ -0,0 +1,31 @@
+// 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.
+
+// +build darwin dragonfly freebsd linux netbsd openbsd solaris
+
+package socket
+
+import "syscall"
+
+var (
+	errEAGAIN error = syscall.EAGAIN
+	errEINVAL error = syscall.EINVAL
+	errENOENT error = syscall.ENOENT
+)
+
+// errnoErr returns common boxed Errno values, to prevent allocations
+// at runtime.
+func errnoErr(errno syscall.Errno) error {
+	switch errno {
+	case 0:
+		return nil
+	case syscall.EAGAIN:
+		return errEAGAIN
+	case syscall.EINVAL:
+		return errEINVAL
+	case syscall.ENOENT:
+		return errENOENT
+	}
+	return errno
+}

internal/socket/error_windows.go

@@ -0,0 +1,26 @@
+// 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.
+
+package socket
+
+import "syscall"
+
+var (
+	errERROR_IO_PENDING error = syscall.ERROR_IO_PENDING
+	errEINVAL           error = syscall.EINVAL
+)
+
+// errnoErr returns common boxed Errno values, to prevent allocations
+// at runtime.
+func errnoErr(errno syscall.Errno) error {
+	switch errno {
+	case 0:
+		return nil
+	case syscall.ERROR_IO_PENDING:
+		return errERROR_IO_PENDING
+	case syscall.EINVAL:
+		return errEINVAL
+	}
+	return errno
+}

internal/socket/rawconn.go

@@ -0,0 +1,66 @@
+// 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.
+
+// +build go1.9
+
+package socket
+
+import (
+	"errors"
+	"net"
+	"os"
+	"syscall"
+)
+
+// A Conn represents a raw connection.
+type Conn struct {
+	network string
+	c       syscall.RawConn
+}
+
+// NewConn returns a new raw connection.
+func NewConn(c net.Conn) (*Conn, error) {
+	var err error
+	var cc Conn
+	switch c := c.(type) {
+	case *net.TCPConn:
+		cc.network = "tcp"
+		cc.c, err = c.SyscallConn()
+	case *net.UDPConn:
+		cc.network = "udp"
+		cc.c, err = c.SyscallConn()
+	case *net.IPConn:
+		cc.network = "ip"
+		cc.c, err = c.SyscallConn()
+	default:
+		return nil, errors.New("unknown connection type")
+	}
+	if err != nil {
+		return nil, err
+	}
+	return &cc, nil
+}
+
+func (o *Option) get(c *Conn, b []byte) (int, error) {
+	var operr error
+	var n int
+	fn := func(s uintptr) {
+		n, operr = getsockopt(s, o.Level, o.Name, b)
+	}
+	if err := c.c.Control(fn); err != nil {
+		return 0, err
+	}
+	return n, os.NewSyscallError("getsockopt", operr)
+}
+
+func (o *Option) set(c *Conn, b []byte) error {
+	var operr error
+	fn := func(s uintptr) {
+		operr = setsockopt(s, o.Level, o.Name, b)
+	}
+	if err := c.c.Control(fn); err != nil {
+		return err
+	}
+	return os.NewSyscallError("setsockopt", operr)
+}

internal/socket/reflect.go

@@ -0,0 +1,41 @@
+// 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.
+
+// +build !go1.9
+
+package socket
+
+import (
+	"net"
+	"os"
+
+	"golang.org/x/net/internal/netreflect"
+)
+
+// A Conn represents a raw connection.
+type Conn struct {
+	c net.Conn
+}
+
+// NewConn returns a new raw connection.
+func NewConn(c net.Conn) (*Conn, error) {
+	return &Conn{c: c}, nil
+}
+
+func (o *Option) get(c *Conn, b []byte) (int, error) {
+	s, err := netreflect.SocketOf(c.c)
+	if err != nil {
+		return 0, err
+	}
+	n, err := getsockopt(s, o.Level, o.Name, b)
+	return n, os.NewSyscallError("getsockopt", err)
+}
+
+func (o *Option) set(c *Conn, b []byte) error {
+	s, err := netreflect.SocketOf(c.c)
+	if err != nil {
+		return err
+	}
+	return os.NewSyscallError("setsockopt", setsockopt(s, o.Level, o.Name, b))
+}

internal/socket/socket.go

@@ -0,0 +1,84 @@
+// 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.
+
+// Package socket provides a portable interface for socket system
+// calls.
+package socket // import "golang.org/x/net/internal/socket"
+
+import "errors"
+
+// An Option represents a sticky socket option.
+type Option struct {
+	Level int // level
+	Name  int // name; must be equal or greater than 1
+	Len   int // length of value in bytes; must be equal or greater than 1
+}
+
+// Get reads a value for the option from the kernel.
+// It returns the number of bytes written into b.
+func (o *Option) Get(c *Conn, b []byte) (int, error) {
+	if o.Name < 1 || o.Len < 1 {
+		return 0, errors.New("invalid option")
+	}
+	if len(b) < o.Len {
+		return 0, errors.New("short buffer")
+	}
+	return o.get(c, b)
+}
+
+// GetInt returns an integer value for the option.
+//
+// The Len field of Option must be either 1 or 4.
+func (o *Option) GetInt(c *Conn) (int, error) {
+	if o.Len != 1 && o.Len != 4 {
+		return 0, errors.New("invalid option")
+	}
+	var b []byte
+	var bb [4]byte
+	if o.Len == 1 {
+		b = bb[:1]
+	} else {
+		b = bb[:4]
+	}
+	n, err := o.get(c, b)
+	if err != nil {
+		return 0, err
+	}
+	if n != o.Len {
+		return 0, errors.New("invalid option length")
+	}
+	if o.Len == 1 {
+		return int(b[0]), nil
+	}
+	return int(NativeEndian.Uint32(b[:4])), nil
+}
+
+// Set writes the option and value to the kernel.
+func (o *Option) Set(c *Conn, b []byte) error {
+	if o.Name < 1 || o.Len < 1 {
+		return errors.New("invalid option")
+	}
+	if len(b) < o.Len {
+		return errors.New("short buffer")
+	}
+	return o.set(c, b)
+}
+
+// SetInt writes the option and value to the kernel.
+//
+// The Len field of Option must be either 1 or 4.
+func (o *Option) SetInt(c *Conn, v int) error {
+	if o.Len != 1 && o.Len != 4 {
+		return errors.New("invalid option")
+	}
+	var b []byte
+	if o.Len == 1 {
+		b = []byte{byte(v)}
+	} else {
+		var bb [4]byte
+		NativeEndian.PutUint32(bb[:o.Len], uint32(v))
+		b = bb[:4]
+	}
+	return o.set(c, b)
+}

internal/socket/socket_test.go

@@ -0,0 +1,46 @@
+// 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.
+
+// +build darwin dragonfly freebsd linux netbsd openbsd solaris windows
+
+package socket_test
+
+import (
+	"net"
+	"runtime"
+	"syscall"
+	"testing"
+
+	"golang.org/x/net/internal/nettest"
+	"golang.org/x/net/internal/socket"
+)
+
+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)
+	}
+}

internal/socket/sys.go

@@ -0,0 +1,24 @@
+// 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.
+
+package socket
+
+import (
+	"encoding/binary"
+	"unsafe"
+)
+
+// NativeEndian is the machine native endian implementation of
+// ByteOrder.
+var NativeEndian binary.ByteOrder
+
+func init() {
+	i := uint32(1)
+	b := (*[4]byte)(unsafe.Pointer(&i))
+	if b[0] == 1 {
+		NativeEndian = binary.LittleEndian
+	} else {
+		NativeEndian = binary.BigEndian
+	}
+}

internal/socket/sys_linux_386.go

@@ -0,0 +1,29 @@
+// 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.
+
+package socket
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+const (
+	sysSETSOCKOPT = 0xe
+	sysGETSOCKOPT = 0xf
+)
+
+func socketcall(call, a0, a1, a2, a3, a4, a5 uintptr) (uintptr, syscall.Errno)
+func rawsocketcall(call, a0, a1, a2, a3, a4, a5 uintptr) (uintptr, syscall.Errno)
+
+func getsockopt(s uintptr, level, name int, b []byte) (int, error) {
+	l := uint32(len(b))
+	_, errno := socketcall(sysGETSOCKOPT, s, uintptr(level), uintptr(name), uintptr(unsafe.Pointer(&b[0])), uintptr(unsafe.Pointer(&l)), 0)
+	return int(l), errnoErr(errno)
+}
+
+func setsockopt(s uintptr, level, name int, b []byte) error {
+	_, errno := socketcall(sysSETSOCKOPT, s, uintptr(level), uintptr(name), uintptr(unsafe.Pointer(&b[0])), uintptr(len(b)), 0)
+	return errnoErr(errno)
+}

internal/socket/sys_linux_386.s

@@ -0,0 +1,11 @@
+// Copyright 2014 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.
+
+#include "textflag.h"
+
+TEXT	·socketcall(SB),NOSPLIT,$0-36
+	JMP	syscall·socketcall(SB)
+
+TEXT	·rawsocketcall(SB),NOSPLIT,$0-36
+	JMP	syscall·rawsocketcall(SB)