net: make {TCP,UDP,IP,Unix}Conn compliant of syscall.Conn interface

This change makes {TCP,UDP,IP,Unix}Conn types compliant of
syscall.Conn interface and adds type rawConn as an implementation of
syscall.RawConn interface.

By this change, the long-standing issues regarding unsupported socket
options and system calls can be solved partly and the broken x/net
packages due to https://go-review.googlesource.com/36799 can be
repaired.

Fixes #3661.
Updates #9661.
Updates #19051.
Updates #19435.

Change-Id: Ic996b040418b54f6d043bc70591789d5a5b23270
Reviewed-on: https://go-review.googlesource.com/37039
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/net/iprawsock.go

@@ -93,6 +93,15 @@ type IPConn struct {
 	conn
 }
 
+// SyscallConn returns a raw network connection.
+// This implements the syscall.Conn interface.
+func (c *IPConn) SyscallConn() (syscall.RawConn, error) {
+	if !c.ok() {
+		return nil, syscall.EINVAL
+	}
+	return newRawConn(c.fd)
+}
+
 // ReadFromIP reads an IP packet from c, copying the payload into b.
 // It returns the number of bytes copied into b and the return address
 // that was on the packet.

src/net/rawconn.go

@@ -0,0 +1,59 @@
+// 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 net
+
+import (
+	"runtime"
+	"syscall"
+)
+
+// BUG(mikio): On NaCl, Plan 9 and Windows, the Control, Read and
+// Write methods of syscall.RawConn are not implemented.
+
+type rawConn struct {
+	fd *netFD
+}
+
+func (c *rawConn) ok() bool { return c != nil && c.fd != nil }
+
+func (c *rawConn) Control(f func(uintptr)) error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	err := c.fd.pfd.RawControl(f)
+	runtime.KeepAlive(c.fd)
+	if err != nil {
+		err = &OpError{Op: "raw-control", Net: c.fd.net, Source: nil, Addr: c.fd.laddr, Err: err}
+	}
+	return err
+}
+
+func (c *rawConn) Read(f func(uintptr) bool) error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	err := c.fd.pfd.RawRead(f)
+	runtime.KeepAlive(c.fd)
+	if err != nil {
+		err = &OpError{Op: "raw-read", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
+	}
+	return err
+}
+
+func (c *rawConn) Write(f func(uintptr) bool) error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	err := c.fd.pfd.RawWrite(f)
+	runtime.KeepAlive(c.fd)
+	if err != nil {
+		err = &OpError{Op: "raw-write", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
+	}
+	return err
+}
+
+func newRawConn(fd *netFD) (*rawConn, error) {
+	return &rawConn{fd: fd}, nil
+}

src/net/rawconn_test.go

@@ -0,0 +1,94 @@
+// 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 net
+
+import (
+	"bytes"
+	"syscall"
+	"testing"
+)
+
+func TestRawConn(t *testing.T) {
+	handler := func(ls *localServer, ln Listener) {
+		c, err := ln.Accept()
+		if err != nil {
+			t.Error(err)
+			return
+		}
+		defer c.Close()
+		var b [32]byte
+		n, err := c.Read(b[:])
+		if err != nil {
+			t.Error(err)
+			return
+		}
+		if _, err := c.Write(b[:n]); err != nil {
+			t.Error(err)
+			return
+		}
+	}
+	ls, err := newLocalServer("tcp")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer ls.teardown()
+	if err := ls.buildup(handler); err != nil {
+		t.Fatal(err)
+	}
+
+	c, err := Dial(ls.Listener.Addr().Network(), ls.Listener.Addr().String())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer c.Close()
+	cc, err := c.(*TCPConn).SyscallConn()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var operr error
+	data := []byte("HELLO-R-U-THERE")
+	err = cc.Write(func(s uintptr) bool {
+		_, operr = syscall.Write(int(s), data)
+		if operr == syscall.EAGAIN {
+			return false
+		}
+		return true
+	})
+	if err != nil || operr != nil {
+		t.Fatal(err, operr)
+	}
+
+	var nr int
+	var b [32]byte
+	err = cc.Read(func(s uintptr) bool {
+		nr, operr = syscall.Read(int(s), b[:])
+		if operr == syscall.EAGAIN {
+			return false
+		}
+		return true
+	})
+	if err != nil || operr != nil {
+		t.Fatal(err, operr)
+	}
+	if bytes.Compare(b[:nr], data) != 0 {
+		t.Fatalf("got %#v; want %#v", b[:nr], data)
+	}
+
+	fn := func(s uintptr) {
+		operr = syscall.SetsockoptInt(int(s), syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1)
+	}
+	err = cc.Control(fn)
+	if err != nil || operr != nil {
+		t.Fatal(err, operr)
+	}
+	c.Close()
+	err = cc.Control(fn)
+	if err == nil {
+		t.Fatal("should fail")
+	}
+}

src/net/tcpsock.go

@@ -80,6 +80,15 @@ type TCPConn struct {
 	conn
 }
 
+// SyscallConn returns a raw network connection.
+// This implements the syscall.Conn interface.
+func (c *TCPConn) SyscallConn() (syscall.RawConn, error) {
+	if !c.ok() {
+		return nil, syscall.EINVAL
+	}
+	return newRawConn(c.fd)
+}
+
 // ReadFrom implements the io.ReaderFrom ReadFrom method.
 func (c *TCPConn) ReadFrom(r io.Reader) (int64, error) {
 	if !c.ok() {

src/net/udpsock.go

@@ -83,6 +83,15 @@ type UDPConn struct {
 	conn
 }
 
+// SyscallConn returns a raw network connection.
+// This implements the syscall.Conn interface.
+func (c *UDPConn) SyscallConn() (syscall.RawConn, error) {
+	if !c.ok() {
+		return nil, syscall.EINVAL
+	}
+	return newRawConn(c.fd)
+}
+
 // ReadFromUDP reads a UDP packet from c, copying the payload into b.
 // It returns the number of bytes copied into b and the return address
 // that was on the packet.

src/net/unixsock.go

@@ -60,6 +60,15 @@ type UnixConn struct {
 	conn
 }
 
+// SyscallConn returns a raw network connection.
+// This implements the syscall.Conn interface.
+func (c *UnixConn) SyscallConn() (syscall.RawConn, error) {
+	if !c.ok() {
+		return nil, syscall.EINVAL
+	}
+	return newRawConn(c.fd)
+}
+
 // CloseRead shuts down the reading side of the Unix domain connection.
 // Most callers should just use Close.
 func (c *UnixConn) CloseRead() error {