net: fix inconsistent errors

These a series of changes fix inconsistent errors on the package net
APIs. Now almost all the APIs return OpError as a common error type
except Lookup, Resolve and Parse APIs. The Lookup, Resolve and Parse
APIs return more specific errors such as DNSError, AddrError or
ParseError.

An OpError may contain nested error information. For example, Dial may
return an OpError containing a DNSError, AddrError, unexposed type/value
or other package's type/value like the following:
	OpError{/* dial info */, Err: &DNSError{}}
	OpError{/* dial info */, Err: &AddrError{}}
	OpError{/* dial info */, Err: <unexposed type or value>}
	OpError{/* dial info */, Err: <other package's type or value>}

and Read and Write may return an OpError containing other OpError when
an application uses io.Copy or similar:
	OpError{/* for io.Reader */, Err: &OpError{/* for io.Writer */}}

When an endpoint is created for connection-oriented byte-stream
protocols, Read may return an io.EOF when the connection is closed by
remote endpoint.

Fixes #4856.

A series of changes:
- net: fix inconsistent error values on Dial, Listen partially
  https://go.googlesource.com/go/+/89b7c66d0d14462fd7893be4290bdfe5f9063ae1
- net: fix inconsistent error values on Read
  https://go.googlesource.com/go/+/ec1144423f45e010c72363fe59291d43214b6e31
- net: fix inconsistent error values on Write
  https://go.googlesource.com/go/+/11b5f98bf0d5eb8854f735cc332c912725070214
- net: fix inconsistent error values on Close
  https://go.googlesource.com/go/+/310db63c5bc121e7bfccb494c01a6b91a257e7fc
- net: fix inconsistent error values on Accept
  https://go.googlesource.com/go/+/4540e162b1aefda8157372764ad3d290a414ef1d
- net: fix inconsistent error values on File
  https://go.googlesource.com/go/+/885111365ba0a74421059bfbd18f4c57c1e70332
- net: fix inconsistent error values on setters
  https://go.googlesource.com/go/+/2173a27903897c481b0a0daf3ca3e0a0685701db
- net: fix inconsistent error values on Interface
  https://go.googlesource.com/go/+/456cf0f22c93e1a6654980f4a48a564555f6c8a2
- net: fix inconsistent error values on Lookup
  https://go.googlesource.com/go/+/0fc582e87942b2e52bed751b6c56660ba99e9a7d
- net: add Source field to OpError
  https://go.googlesource.com/go/+/afd2d2b6df3ebfe99faf347030f15adfdf422fa0

Change-Id: Id678e369088dc9fbe9073cfe7ff8a8754a57d61f
Reviewed-on: https://go-review.googlesource.com/9236Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/net/fd_plan9.go

@@ -202,7 +202,7 @@ func (fd *netFD) file(f *os.File, s string) (*os.File, error) {
 	dfd, err := syscall.Dup(int(f.Fd()), -1)
 	syscall.ForkLock.RUnlock()
 	if err != nil {
-		return nil, err
+		return nil, os.NewSyscallError("dup", err)
 	}
 	return os.NewFile(uintptr(dfd), s), nil
 }

src/net/fd_unix.go

@@ -93,7 +93,7 @@ func (fd *netFD) connect(la, ra syscall.Sockaddr, deadline time.Time) error {
 		}
 		fallthrough
 	default:
-		return err
+		return os.NewSyscallError("connect", err)
 	}
 	if err := fd.init(); err != nil {
 		return err
@@ -116,14 +116,14 @@ func (fd *netFD) connect(la, ra syscall.Sockaddr, deadline time.Time) error {
 		}
 		nerr, err := getsockoptIntFunc(fd.sysfd, syscall.SOL_SOCKET, syscall.SO_ERROR)
 		if err != nil {
-			return err
+			return os.NewSyscallError("getsockopt", err)
 		}
 		switch err := syscall.Errno(nerr); err {
 		case syscall.EINPROGRESS, syscall.EALREADY, syscall.EINTR:
 		case syscall.Errno(0), syscall.EISCONN:
 			return nil
 		default:
-			return err
+			return os.NewSyscallError("getsockopt", err)
 		}
 	}
 }
@@ -205,7 +205,7 @@ func (fd *netFD) shutdown(how int) error {
 		return err
 	}
 	defer fd.decref()
-	return syscall.Shutdown(fd.sysfd, how)
+	return os.NewSyscallError("shutdown", syscall.Shutdown(fd.sysfd, how))
 }
 
 func (fd *netFD) closeRead() error {
@@ -237,6 +237,9 @@ func (fd *netFD) Read(p []byte) (n int, err error) {
 		err = fd.eofError(n, err)
 		break
 	}
+	if _, ok := err.(syscall.Errno); ok {
+		err = os.NewSyscallError("read", err)
+	}
 	return
 }
 
@@ -261,6 +264,9 @@ func (fd *netFD) readFrom(p []byte) (n int, sa syscall.Sockaddr, err error) {
 		err = fd.eofError(n, err)
 		break
 	}
+	if _, ok := err.(syscall.Errno); ok {
+		err = os.NewSyscallError("recvfrom", err)
+	}
 	return
 }
 
@@ -285,6 +291,9 @@ func (fd *netFD) readMsg(p []byte, oob []byte) (n, oobn, flags int, sa syscall.S
 		err = fd.eofError(n, err)
 		break
 	}
+	if _, ok := err.(syscall.Errno); ok {
+		err = os.NewSyscallError("recvmsg", err)
+	}
 	return
 }
 
@@ -318,6 +327,9 @@ func (fd *netFD) Write(p []byte) (nn int, err error) {
 			break
 		}
 	}
+	if _, ok := err.(syscall.Errno); ok {
+		err = os.NewSyscallError("write", err)
+	}
 	return nn, err
 }
 
@@ -341,6 +353,9 @@ func (fd *netFD) writeTo(p []byte, sa syscall.Sockaddr) (n int, err error) {
 	if err == nil {
 		n = len(p)
 	}
+	if _, ok := err.(syscall.Errno); ok {
+		err = os.NewSyscallError("sendto", err)
+	}
 	return
 }
 
@@ -364,6 +379,9 @@ func (fd *netFD) writeMsg(p []byte, oob []byte, sa syscall.Sockaddr) (n int, oob
 	if err == nil {
 		oobn = len(oob)
 	}
+	if _, ok := err.(syscall.Errno); ok {
+		err = os.NewSyscallError("sendmsg", err)
+	}
 	return
 }
 
@@ -381,13 +399,20 @@ func (fd *netFD) accept() (netfd *netFD, err error) {
 	for {
 		s, rsa, err = accept(fd.sysfd)
 		if err != nil {
-			if err == syscall.EAGAIN {
+			nerr, ok := err.(*os.SyscallError)
+			if !ok {
+				return nil, err
+			}
+			switch nerr.Err {
+			case syscall.EAGAIN:
 				if err = fd.pd.WaitRead(); err == nil {
 					continue
 				}
-			} else if err == syscall.ECONNABORTED {
-				// This means that a socket on the listen queue was closed
-				// before we Accept()ed it; it's a silly error, so try again.
+			case syscall.ECONNABORTED:
+				// This means that a socket on the
+				// listen queue was closed before we
+				// Accept()ed it; it's a silly error,
+				// so try again.
 				continue
 			}
 			return nil, err
@@ -436,7 +461,7 @@ func dupCloseOnExec(fd int) (newfd int, err error) {
 			// from now on.
 			atomic.StoreInt32(&tryDupCloexec, 0)
 		default:
-			return -1, e1
+			return -1, os.NewSyscallError("fcntl", e1)
 		}
 	}
 	return dupCloseOnExecOld(fd)
@@ -449,7 +474,7 @@ func dupCloseOnExecOld(fd int) (newfd int, err error) {
 	defer syscall.ForkLock.RUnlock()
 	newfd, err = syscall.Dup(fd)
 	if err != nil {
-		return -1, err
+		return -1, os.NewSyscallError("dup", err)
 	}
 	syscall.CloseOnExec(newfd)
 	return
@@ -466,7 +491,7 @@ func (fd *netFD) dup() (f *os.File, err error) {
 	// I/O will block the thread instead of letting us use the epoll server.
 	// Everything will still work, just with more threads.
 	if err = syscall.SetNonblock(ns, false); err != nil {
-		return nil, err
+		return nil, os.NewSyscallError("setnonblock", err)
 	}
 
 	return os.NewFile(uintptr(ns), fd.name()), nil

src/net/fd_windows.go

@@ -38,7 +38,7 @@ func sysInit() {
 	var d syscall.WSAData
 	e := syscall.WSAStartup(uint32(0x202), &d)
 	if e != nil {
-		initErr = os.NewSyscallError("WSAStartup", e)
+		initErr = os.NewSyscallError("wsastartup", e)
 	}
 	canCancelIO = syscall.LoadCancelIoEx() == nil
 	if syscall.LoadGetAddrInfo() == nil {
@@ -297,7 +297,7 @@ func (fd *netFD) init() error {
 		size := uint32(unsafe.Sizeof(flag))
 		err := syscall.WSAIoctl(fd.sysfd, syscall.SIO_UDP_CONNRESET, (*byte)(unsafe.Pointer(&flag)), size, nil, 0, &ret, nil, 0)
 		if err != nil {
-			return os.NewSyscallError("WSAIoctl", err)
+			return os.NewSyscallError("wsaioctl", err)
 		}
 	}
 	fd.rop.mode = 'r'
@@ -331,7 +331,7 @@ func (fd *netFD) connect(la, ra syscall.Sockaddr, deadline time.Time) error {
 		defer fd.setWriteDeadline(noDeadline)
 	}
 	if !canUseConnectEx(fd.net) {
-		return connectFunc(fd.sysfd, ra)
+		return os.NewSyscallError("connect", connectFunc(fd.sysfd, ra))
 	}
 	// ConnectEx windows API requires an unconnected, previously bound socket.
 	if la == nil {
@@ -344,7 +344,7 @@ func (fd *netFD) connect(la, ra syscall.Sockaddr, deadline time.Time) error {
 			panic("unexpected type in connect")
 		}
 		if err := syscall.Bind(fd.sysfd, la); err != nil {
-			return err
+			return os.NewSyscallError("bind", err)
 		}
 	}
 	// Call ConnectEx API.
@@ -354,10 +354,13 @@ func (fd *netFD) connect(la, ra syscall.Sockaddr, deadline time.Time) error {
 		return connectExFunc(o.fd.sysfd, o.sa, nil, 0, nil, &o.o)
 	})
 	if err != nil {
+		if _, ok := err.(syscall.Errno); ok {
+			err = os.NewSyscallError("connectex", err)
+		}
 		return err
 	}
 	// Refresh socket properties.
-	return syscall.Setsockopt(fd.sysfd, syscall.SOL_SOCKET, syscall.SO_UPDATE_CONNECT_CONTEXT, (*byte)(unsafe.Pointer(&fd.sysfd)), int32(unsafe.Sizeof(fd.sysfd)))
+	return os.NewSyscallError("setsockopt", syscall.Setsockopt(fd.sysfd, syscall.SOL_SOCKET, syscall.SO_UPDATE_CONNECT_CONTEXT, (*byte)(unsafe.Pointer(&fd.sysfd)), int32(unsafe.Sizeof(fd.sysfd))))
 }
 
 func (fd *netFD) destroy() {
@@ -461,7 +464,11 @@ func (fd *netFD) Read(buf []byte) (int, error) {
 	if raceenabled {
 		raceAcquire(unsafe.Pointer(&ioSync))
 	}
-	return n, fd.eofError(n, err)
+	err = fd.eofError(n, err)
+	if _, ok := err.(syscall.Errno); ok {
+		err = os.NewSyscallError("wsarecv", err)
+	}
+	return n, err
 }
 
 func (fd *netFD) readFrom(buf []byte) (int, syscall.Sockaddr, error) {
@@ -482,11 +489,14 @@ func (fd *netFD) readFrom(buf []byte) (int, syscall.Sockaddr, error) {
 		return syscall.WSARecvFrom(o.fd.sysfd, &o.buf, 1, &o.qty, &o.flags, o.rsa, &o.rsan, &o.o, nil)
 	})
 	err = fd.eofError(n, err)
+	if _, ok := err.(syscall.Errno); ok {
+		err = os.NewSyscallError("wsarecvfrom", err)
+	}
 	if err != nil {
 		return n, nil, err
 	}
 	sa, _ := o.rsa.Sockaddr()
-	return n, sa, err
+	return n, sa, nil
 }
 
 func (fd *netFD) Write(buf []byte) (int, error) {
@@ -502,6 +512,9 @@ func (fd *netFD) Write(buf []byte) (int, error) {
 	n, err := wsrv.ExecIO(o, "WSASend", func(o *operation) error {
 		return syscall.WSASend(o.fd.sysfd, &o.buf, 1, &o.qty, 0, &o.o, nil)
 	})
+	if _, ok := err.(syscall.Errno); ok {
+		err = os.NewSyscallError("wsasend", err)
+	}
 	return n, err
 }
 
@@ -519,6 +532,9 @@ func (fd *netFD) writeTo(buf []byte, sa syscall.Sockaddr) (int, error) {
 	n, err := wsrv.ExecIO(o, "WSASendto", func(o *operation) error {
 		return syscall.WSASendto(o.fd.sysfd, &o.buf, 1, &o.qty, 0, o.sa, &o.o, nil)
 	})
+	if _, ok := err.(syscall.Errno); ok {
+		err = os.NewSyscallError("wsasendto", err)
+	}
 	return n, err
 }
 
@@ -548,6 +564,9 @@ func (fd *netFD) acceptOne(rawsa []syscall.RawSockaddrAny, o *operation) (*netFD
 	})
 	if err != nil {
 		netfd.Close()
+		if _, ok := err.(syscall.Errno); ok {
+			err = os.NewSyscallError("acceptex", err)
+		}
 		return nil, err
 	}
 
@@ -555,7 +574,7 @@ func (fd *netFD) acceptOne(rawsa []syscall.RawSockaddrAny, o *operation) (*netFD
 	err = syscall.Setsockopt(s, syscall.SOL_SOCKET, syscall.SO_UPDATE_ACCEPT_CONTEXT, (*byte)(unsafe.Pointer(&fd.sysfd)), int32(unsafe.Sizeof(fd.sysfd)))
 	if err != nil {
 		netfd.Close()
-		return nil, err
+		return nil, os.NewSyscallError("setsockopt", err)
 	}
 
 	return netfd, nil
@@ -581,7 +600,11 @@ func (fd *netFD) accept() (*netFD, error) {
 		// before AcceptEx could complete. These errors relate to new
 		// connection, not to AcceptEx, so ignore broken connection and
 		// try AcceptEx again for more connections.
-		errno, ok := err.(syscall.Errno)
+		nerr, ok := err.(*os.SyscallError)
+		if !ok {
+			return nil, err
+		}
+		errno, ok := nerr.Err.(syscall.Errno)
 		if !ok {
 			return nil, err
 		}

src/net/file_plan9.go

@@ -39,7 +39,7 @@ func newFileFD(f *os.File) (net *netFD, err error) {
 
 	path, err := syscall.Fd2path(int(f.Fd()))
 	if err != nil {
-		return nil, err
+		return nil, os.NewSyscallError("fd2path", err)
 	}
 	comp := splitAtBytes(path, "/")
 	n := len(comp)
@@ -54,7 +54,7 @@ func newFileFD(f *os.File) (net *netFD, err error) {
 		fd, err := syscall.Dup(int(f.Fd()), -1)
 		syscall.ForkLock.RUnlock()
 		if err != nil {
-			return nil, err
+			return nil, os.NewSyscallError("dup", err)
 		}
 		defer close(fd)
 

src/net/file_unix.go

@@ -19,13 +19,13 @@ func newFileFD(f *os.File) (*netFD, error) {
 
 	if err = syscall.SetNonblock(fd, true); err != nil {
 		closeFunc(fd)
-		return nil, err
+		return nil, os.NewSyscallError("setnonblock", err)
 	}
 
 	sotype, err := syscall.GetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_TYPE)
 	if err != nil {
 		closeFunc(fd)
-		return nil, err
+		return nil, os.NewSyscallError("getsockopt", err)
 	}
 
 	family := syscall.AF_UNSPEC

src/net/interface_bsd.go

@@ -7,6 +7,7 @@
 package net
 
 import (
+	"os"
 	"syscall"
 	"unsafe"
 )
@@ -17,11 +18,11 @@ import (
 func interfaceTable(ifindex int) ([]Interface, error) {
 	tab, err := syscall.RouteRIB(syscall.NET_RT_IFLIST, ifindex)
 	if err != nil {
-		return nil, err
+		return nil, os.NewSyscallError("routerib", err)
 	}
 	msgs, err := syscall.ParseRoutingMessage(tab)
 	if err != nil {
-		return nil, err
+		return nil, os.NewSyscallError("parseroutingmessage", err)
 	}
 	return parseInterfaceTable(ifindex, msgs)
 }
@@ -50,7 +51,7 @@ loop:
 func newLink(m *syscall.InterfaceMessage) (*Interface, error) {
 	sas, err := syscall.ParseRoutingSockaddr(m)
 	if err != nil {
-		return nil, err
+		return nil, os.NewSyscallError("parseroutingsockaddr", err)
 	}
 	ifi := &Interface{Index: int(m.Header.Index), Flags: linkFlags(m.Header.Flags)}
 	sa, _ := sas[syscall.RTAX_IFP].(*syscall.SockaddrDatalink)
@@ -103,11 +104,11 @@ func interfaceAddrTable(ifi *Interface) ([]Addr, error) {
 	}
 	tab, err := syscall.RouteRIB(syscall.NET_RT_IFLIST, index)
 	if err != nil {
-		return nil, err
+		return nil, os.NewSyscallError("routerib", err)
 	}
 	msgs, err := syscall.ParseRoutingMessage(tab)
 	if err != nil {
-		return nil, err
+		return nil, os.NewSyscallError("parseroutingmessage", err)
 	}
 	var ift []Interface
 	if index == 0 {
@@ -144,7 +145,7 @@ func interfaceAddrTable(ifi *Interface) ([]Addr, error) {
 func newAddr(ifi *Interface, m *syscall.InterfaceAddrMessage) (*IPNet, error) {
 	sas, err := syscall.ParseRoutingSockaddr(m)
 	if err != nil {
-		return nil, err
+		return nil, os.NewSyscallError("parseroutingsockaddr", err)
 	}
 	ifa := &IPNet{}
 	switch sa := sas[syscall.RTAX_NETMASK].(type) {

src/net/interface_darwin.go

@@ -4,18 +4,21 @@
 
 package net
 
-import "syscall"
+import (
+	"os"
+	"syscall"
+)
 
 // interfaceMulticastAddrTable returns addresses for a specific
 // interface.
 func interfaceMulticastAddrTable(ifi *Interface) ([]Addr, error) {
 	tab, err := syscall.RouteRIB(syscall.NET_RT_IFLIST2, ifi.Index)
 	if err != nil {
-		return nil, err
+		return nil, os.NewSyscallError("routerib", err)
 	}
 	msgs, err := syscall.ParseRoutingMessage(tab)
 	if err != nil {
-		return nil, err
+		return nil, os.NewSyscallError("parseroutingmessage", err)
 	}
 	var ifmat []Addr
 	for _, m := range msgs {
@@ -38,7 +41,7 @@ func interfaceMulticastAddrTable(ifi *Interface) ([]Addr, error) {
 func newMulticastAddr(ifi *Interface, m *syscall.InterfaceMulticastAddrMessage) (*IPAddr, error) {
 	sas, err := syscall.ParseRoutingSockaddr(m)
 	if err != nil {
-		return nil, err
+		return nil, os.NewSyscallError("parseroutingsockaddr", err)
 	}
 	switch sa := sas[syscall.RTAX_IFA].(type) {
 	case *syscall.SockaddrInet4:

src/net/interface_freebsd.go

@@ -4,18 +4,21 @@
 
 package net
 
-import "syscall"
+import (
+	"os"
+	"syscall"
+)
 
 // interfaceMulticastAddrTable returns addresses for a specific
 // interface.
 func interfaceMulticastAddrTable(ifi *Interface) ([]Addr, error) {
 	tab, err := syscall.RouteRIB(syscall.NET_RT_IFMALIST, ifi.Index)
 	if err != nil {
-		return nil, err
+		return nil, os.NewSyscallError("routerib", err)
 	}
 	msgs, err := syscall.ParseRoutingMessage(tab)
 	if err != nil {
-		return nil, err
+		return nil, os.NewSyscallError("parseroutingmessage", err)
 	}
 	var ifmat []Addr
 	for _, m := range msgs {
@@ -38,7 +41,7 @@ func interfaceMulticastAddrTable(ifi *Interface) ([]Addr, error) {
 func newMulticastAddr(ifi *Interface, m *syscall.InterfaceMulticastAddrMessage) (*IPAddr, error) {
 	sas, err := syscall.ParseRoutingSockaddr(m)
 	if err != nil {
-		return nil, err
+		return nil, os.NewSyscallError("parseroutingsockaddr", err)
 	}
 	switch sa := sas[syscall.RTAX_IFA].(type) {
 	case *syscall.SockaddrInet4:

src/net/interface_linux.go

@@ -5,6 +5,7 @@
 package net
 
 import (
+	"os"
 	"syscall"
 	"unsafe"
 )
@@ -15,11 +16,11 @@ import (
 func interfaceTable(ifindex int) ([]Interface, error) {
 	tab, err := syscall.NetlinkRIB(syscall.RTM_GETLINK, syscall.AF_UNSPEC)
 	if err != nil {
-		return nil, err
+		return nil, os.NewSyscallError("netlinkrib", err)
 	}
 	msgs, err := syscall.ParseNetlinkMessage(tab)
 	if err != nil {
-		return nil, err
+		return nil, os.NewSyscallError("parsenetlinkmessage", err)
 	}
 	var ift []Interface
 loop:
@@ -32,7 +33,7 @@ loop:
 			if ifindex == 0 || ifindex == int(ifim.Index) {
 				attrs, err := syscall.ParseNetlinkRouteAttr(&m)
 				if err != nil {
-					return nil, err
+					return nil, os.NewSyscallError("parsenetlinkrouteattr", err)
 				}
 				ift = append(ift, *newLink(ifim, attrs))
 				if ifindex == int(ifim.Index) {
@@ -119,11 +120,11 @@ func linkFlags(rawFlags uint32) Flags {
 func interfaceAddrTable(ifi *Interface) ([]Addr, error) {
 	tab, err := syscall.NetlinkRIB(syscall.RTM_GETADDR, syscall.AF_UNSPEC)
 	if err != nil {
-		return nil, err
+		return nil, os.NewSyscallError("netlinkrib", err)
 	}
 	msgs, err := syscall.ParseNetlinkMessage(tab)
 	if err != nil {
-		return nil, err
+		return nil, os.NewSyscallError("parsenetlinkmessage", err)
 	}
 	var ift []Interface
 	if ifi == nil {
@@ -159,7 +160,7 @@ loop:
 				}
 				attrs, err := syscall.ParseNetlinkRouteAttr(&m)
 				if err != nil {
-					return nil, err
+					return nil, os.NewSyscallError("parsenetlinkrouteattr", err)
 				}
 				ifa := newAddr(ifi, ifam, attrs)
 				if ifa != nil {

src/net/interface_windows.go

@@ -6,6 +6,7 @@ package net
 
 import (
 	"internal/syscall/windows"
+	"os"
 	"syscall"
 	"unsafe"
 )
@@ -26,7 +27,7 @@ func getAdapters() (*windows.IpAdapterAddresses, error) {
 			break
 		}
 		if err.(syscall.Errno) != syscall.ERROR_BUFFER_OVERFLOW {
-			return nil, err
+			return nil, os.NewSyscallError("getadaptersaddresses", err)
 		}
 	}
 	return &addrs[0], nil
@@ -44,7 +45,7 @@ func getInterfaceInfos() ([]syscall.InterfaceInfo, error) {
 	size := uint32(unsafe.Sizeof(iia))
 	err = syscall.WSAIoctl(s, syscall.SIO_GET_INTERFACE_LIST, nil, 0, (*byte)(unsafe.Pointer(&iia[0])), size, &ret, nil, 0)
 	if err != nil {
-		return nil, err
+		return nil, os.NewSyscallError("wsaioctl", err)
 	}
 	iilen := ret / uint32(unsafe.Sizeof(iia[0]))
 	return iia[:iilen-1], nil

src/net/ip.go

@@ -12,8 +12,6 @@
 
 package net
 
-import "errors"
-
 // IP address lengths (bytes).
 const (
 	IPv4len = 4
@@ -331,7 +329,7 @@ func (ip IP) MarshalText() ([]byte, error) {
 		return []byte(""), nil
 	}
 	if len(ip) != IPv4len && len(ip) != IPv6len {
-		return nil, errors.New("invalid IP address")
+		return nil, &AddrError{Err: "invalid IP address", Addr: ip.String()}
 	}
 	return []byte(ip.String()), nil
 }
@@ -346,7 +344,7 @@ func (ip *IP) UnmarshalText(text []byte) error {
 	s := string(text)
 	x := ParseIP(s)
 	if x == nil {
-		return &ParseError{"IP address", s}
+		return &ParseError{Type: "IP address", Text: s}
 	}
 	*ip = x
 	return nil
@@ -633,16 +631,6 @@ func parseIPv6(s string, zoneAllowed bool) (ip IP, zone string) {
 	return ip, zone
 }
 
-// A ParseError represents a malformed text string and the type of string that was expected.
-type ParseError struct {
-	Type string
-	Text string
-}
-
-func (e *ParseError) Error() string {
-	return "invalid " + e.Type + ": " + e.Text
-}
-
 // ParseIP parses s as an IP address, returning the result.
 // The string s can be in dotted decimal ("74.125.19.99")
 // or IPv6 ("2001:4860:0:2001::68") form.
@@ -671,7 +659,7 @@ func ParseIP(s string) IP {
 func ParseCIDR(s string) (IP, *IPNet, error) {
 	i := byteIndex(s, '/')
 	if i < 0 {
-		return nil, nil, &ParseError{"CIDR address", s}
+		return nil, nil, &ParseError{Type: "CIDR address", Text: s}
 	}
 	addr, mask := s[:i], s[i+1:]
 	iplen := IPv4len
@@ -682,7 +670,7 @@ func ParseCIDR(s string) (IP, *IPNet, error) {
 	}
 	n, i, ok := dtoi(mask, 0)
 	if ip == nil || !ok || i != len(mask) || n < 0 || n > 8*iplen {
-		return nil, nil, &ParseError{"CIDR address", s}
+		return nil, nil, &ParseError{Type: "CIDR address", Text: s}
 	}
 	m := CIDRMask(n, 8*iplen)
 	return ip, &IPNet{IP: ip.Mask(m), Mask: m}, nil

src/net/ip_test.go

@@ -194,10 +194,10 @@ var parseCIDRTests = []struct {
 	{"abcd:2345::/24", ParseIP("abcd:2345::"), &IPNet{IP: ParseIP("abcd:2300::"), Mask: IPMask(ParseIP("ffff:ff00::"))}, nil},
 	{"2001:DB8::/48", ParseIP("2001:DB8::"), &IPNet{IP: ParseIP("2001:DB8::"), Mask: IPMask(ParseIP("ffff:ffff:ffff::"))}, nil},
 	{"2001:DB8::1/48", ParseIP("2001:DB8::1"), &IPNet{IP: ParseIP("2001:DB8::"), Mask: IPMask(ParseIP("ffff:ffff:ffff::"))}, nil},
-	{"192.168.1.1/255.255.255.0", nil, nil, &ParseError{"CIDR address", "192.168.1.1/255.255.255.0"}},
-	{"192.168.1.1/35", nil, nil, &ParseError{"CIDR address", "192.168.1.1/35"}},
-	{"2001:db8::1/-1", nil, nil, &ParseError{"CIDR address", "2001:db8::1/-1"}},
-	{"", nil, nil, &ParseError{"CIDR address", ""}},
+	{"192.168.1.1/255.255.255.0", nil, nil, &ParseError{Type: "CIDR address", Text: "192.168.1.1/255.255.255.0"}},
+	{"192.168.1.1/35", nil, nil, &ParseError{Type: "CIDR address", Text: "192.168.1.1/35"}},
+	{"2001:db8::1/-1", nil, nil, &ParseError{Type: "CIDR address", Text: "2001:db8::1/-1"}},
+	{"", nil, nil, &ParseError{Type: "CIDR address", Text: ""}},
 }
 
 func TestParseCIDR(t *testing.T) {

src/net/ipsock.go

@@ -122,7 +122,7 @@ func SplitHostPort(hostport string) (host, port string, err error) {
 		// Expect the first ']' just before the last ':'.
 		end := byteIndex(hostport, ']')
 		if end < 0 {
-			err = &AddrError{"missing ']' in address", hostport}
+			err = &AddrError{Err: "missing ']' in address", Addr: hostport}
 			return
 		}
 		switch end + 1 {
@@ -151,11 +151,11 @@ func SplitHostPort(hostport string) (host, port string, err error) {
 		}
 	}
 	if byteIndex(hostport[j:], '[') >= 0 {
-		err = &AddrError{"unexpected '[' in address", hostport}
+		err = &AddrError{Err: "unexpected '[' in address", Addr: hostport}
 		return
 	}
 	if byteIndex(hostport[k:], ']') >= 0 {
-		err = &AddrError{"unexpected ']' in address", hostport}
+		err = &AddrError{Err: "unexpected ']' in address", Addr: hostport}
 		return
 	}
 
@@ -163,15 +163,15 @@ func SplitHostPort(hostport string) (host, port string, err error) {
 	return
 
 missingPort:
-	err = &AddrError{"missing port in address", hostport}
+	err = &AddrError{Err: "missing port in address", Addr: hostport}
 	return
 
 tooManyColons:
-	err = &AddrError{"too many colons in address", hostport}
+	err = &AddrError{Err: "too many colons in address", Addr: hostport}
 	return
 
 missingBrackets:
-	err = &AddrError{"missing brackets in address", hostport}
+	err = &AddrError{Err: "missing brackets in address", Addr: hostport}
 	return
 }
 

src/net/ipsock_plan9.go

@@ -7,7 +7,6 @@
 package net
 
 import (
-	"errors"
 	"os"
 	"syscall"
 )
@@ -60,15 +59,15 @@ func parsePlan9Addr(s string) (ip IP, iport int, err error) {
 	if i >= 0 {
 		addr = ParseIP(s[:i])
 		if addr == nil {
-			return nil, 0, errors.New("parsing IP failed")
+			return nil, 0, &ParseError{Type: "IP address", Text: s}
 		}
 	}
 	p, _, ok := dtoi(s[i+1:], 0)
 	if !ok {
-		return nil, 0, errors.New("parsing port failed")
+		return nil, 0, &ParseError{Type: "port", Text: s}
 	}
 	if p < 0 || p > 0xFFFF {
-		return nil, 0, &AddrError{"invalid port", string(p)}
+		return nil, 0, &AddrError{Err: "invalid port", Addr: string(p)}
 	}
 	return addr, p, nil
 }
@@ -95,7 +94,7 @@ func readPlan9Addr(proto, filename string) (addr Addr, err error) {
 	case "udp":
 		addr = &UDPAddr{IP: ip, Port: port}
 	default:
-		return nil, errors.New("unknown protocol " + proto)
+		return nil, UnknownNetworkError(proto)
 	}
 	return addr, nil
 }

src/net/ipsock_posix.go

@@ -144,7 +144,7 @@ func ipToSockaddr(family int, ip IP, port int, zone string) (syscall.Sockaddr, e
 			ip = IPv4zero
 		}
 		if ip = ip.To4(); ip == nil {
-			return nil, InvalidAddrError("non-IPv4 address")
+			return nil, &AddrError{Err: "non-IPv4 address", Addr: ip.String()}
 		}
 		sa := new(syscall.SockaddrInet4)
 		for i := 0; i < IPv4len; i++ {
@@ -163,7 +163,7 @@ func ipToSockaddr(family int, ip IP, port int, zone string) (syscall.Sockaddr, e
 			ip = IPv6zero
 		}
 		if ip = ip.To16(); ip == nil {
-			return nil, InvalidAddrError("non-IPv6 address")
+			return nil, &AddrError{Err: "non-IPv6 address", Addr: ip.String()}
 		}
 		sa := new(syscall.SockaddrInet6)
 		for i := 0; i < IPv6len; i++ {
@@ -173,5 +173,5 @@ func ipToSockaddr(family int, ip IP, port int, zone string) (syscall.Sockaddr, e
 		sa.ZoneId = uint32(zoneToInt(zone))
 		return sa, nil
 	}
-	return nil, InvalidAddrError("unexpected socket family")
+	return nil, &AddrError{Err: "invalid address family", Addr: ip.String()}
 }

src/net/lookup_plan9.go

@@ -101,19 +101,18 @@ func lookupProtocol(name string) (proto int, err error) {
 	if err != nil {
 		return 0, err
 	}
-	unknownProtoError := errors.New("unknown IP protocol specified: " + name)
 	if len(lines) == 0 {
-		return 0, unknownProtoError
+		return 0, UnknownNetworkError(name)
 	}
 	f := getFields(lines[0])
 	if len(f) < 2 {
-		return 0, unknownProtoError
+		return 0, UnknownNetworkError(name)
 	}
 	s := f[1]
 	if n, _, ok := dtoi(s, byteIndex(s, '=')+1); ok {
 		return n, nil
 	}
-	return 0, unknownProtoError
+	return 0, UnknownNetworkError(name)
 }
 
 func lookupHost(host string) (addrs []string, err error) {
@@ -173,7 +172,7 @@ func lookupPort(network, service string) (port int, err error) {
 	if err != nil {
 		return
 	}
-	unknownPortError := &AddrError{"unknown port", network + "/" + service}
+	unknownPortError := &AddrError{Err: "unknown port", Addr: network + "/" + service}
 	if len(lines) == 0 {
 		return 0, unknownPortError
 	}

src/net/lookup_windows.go

@@ -5,6 +5,7 @@
 package net
 
 import (
+	"os"
 	"runtime"
 	"syscall"
 	"unsafe"
@@ -18,7 +19,7 @@ var (
 func getprotobyname(name string) (proto int, err error) {
 	p, err := syscall.GetProtoByName(name)
 	if err != nil {
-		return 0, err
+		return 0, os.NewSyscallError("getorotobyname", err)
 	}
 	return int(p.Proto), nil
 }
@@ -66,7 +67,7 @@ func gethostbyname(name string) (addrs []IPAddr, err error) {
 	// caller already acquired thread
 	h, err := syscall.GetHostByName(name)
 	if err != nil {
-		return nil, err
+		return nil, os.NewSyscallError("gethostbyname", err)
 	}
 	switch h.AddrType {
 	case syscall.AF_INET:
@@ -116,7 +117,7 @@ func newLookupIP(name string) ([]IPAddr, error) {
 	var result *syscall.AddrinfoW
 	e := syscall.GetAddrInfoW(syscall.StringToUTF16Ptr(name), nil, &hints, &result)
 	if e != nil {
-		return nil, &DNSError{Err: e.Error(), Name: name}
+		return nil, &DNSError{Err: os.NewSyscallError("getaddrinfow", e).Error(), Name: name}
 	}
 	defer syscall.FreeAddrInfoW(result)
 	addrs := make([]IPAddr, 0, 5)
@@ -148,7 +149,7 @@ func getservbyname(network, service string) (int, error) {
 	}
 	s, err := syscall.GetServByName(service, network)
 	if err != nil {
-		return 0, err
+		return 0, os.NewSyscallError("getservbyname", err)
 	}
 	return int(syscall.Ntohs(s.Port)), nil
 }
@@ -194,7 +195,7 @@ func newLookupPort(network, service string) (int, error) {
 	var result *syscall.AddrinfoW
 	e := syscall.GetAddrInfoW(nil, syscall.StringToUTF16Ptr(service), &hints, &result)
 	if e != nil {
-		return 0, &DNSError{Err: e.Error(), Name: network + "/" + service}
+		return 0, &DNSError{Err: os.NewSyscallError("getaddrinfow", e).Error(), Name: network + "/" + service}
 	}
 	defer syscall.FreeAddrInfoW(result)
 	if result == nil {
@@ -226,7 +227,7 @@ func lookupCNAME(name string) (string, error) {
 		return name, nil
 	}
 	if e != nil {
-		return "", &DNSError{Err: e.Error(), Name: name}
+		return "", &DNSError{Err: os.NewSyscallError("dnsquery", e).Error(), Name: name}
 	}
 	defer syscall.DnsRecordListFree(r, 1)
 
@@ -247,7 +248,7 @@ func lookupSRV(service, proto, name string) (string, []*SRV, error) {
 	var r *syscall.DNSRecord
 	e := syscall.DnsQuery(target, syscall.DNS_TYPE_SRV, 0, nil, &r, nil)
 	if e != nil {
-		return "", nil, &DNSError{Err: e.Error(), Name: target}
+		return "", nil, &DNSError{Err: os.NewSyscallError("dnsquery", e).Error(), Name: target}
 	}
 	defer syscall.DnsRecordListFree(r, 1)
 
@@ -266,7 +267,7 @@ func lookupMX(name string) ([]*MX, error) {
 	var r *syscall.DNSRecord
 	e := syscall.DnsQuery(name, syscall.DNS_TYPE_MX, 0, nil, &r, nil)
 	if e != nil {
-		return nil, &DNSError{Err: e.Error(), Name: name}
+		return nil, &DNSError{Err: os.NewSyscallError("dnsquery", e).Error(), Name: name}
 	}
 	defer syscall.DnsRecordListFree(r, 1)
 
@@ -285,7 +286,7 @@ func lookupNS(name string) ([]*NS, error) {
 	var r *syscall.DNSRecord
 	e := syscall.DnsQuery(name, syscall.DNS_TYPE_NS, 0, nil, &r, nil)
 	if e != nil {
-		return nil, &DNSError{Err: e.Error(), Name: name}
+		return nil, &DNSError{Err: os.NewSyscallError("dnsquery", e).Error(), Name: name}
 	}
 	defer syscall.DnsRecordListFree(r, 1)
 
@@ -303,7 +304,7 @@ func lookupTXT(name string) ([]string, error) {
 	var r *syscall.DNSRecord
 	e := syscall.DnsQuery(name, syscall.DNS_TYPE_TEXT, 0, nil, &r, nil)
 	if e != nil {
-		return nil, &DNSError{Err: e.Error(), Name: name}
+		return nil, &DNSError{Err: os.NewSyscallError("dnsquery", e).Error(), Name: name}
 	}
 	defer syscall.DnsRecordListFree(r, 1)
 
@@ -328,7 +329,7 @@ func lookupAddr(addr string) ([]string, error) {
 	var r *syscall.DNSRecord
 	e := syscall.DnsQuery(arpa, syscall.DNS_TYPE_PTR, 0, nil, &r, nil)
 	if e != nil {
-		return nil, &DNSError{Err: e.Error(), Name: addr}
+		return nil, &DNSError{Err: os.NewSyscallError("dnsquery", e).Error(), Name: addr}
 	}
 	defer syscall.DnsRecordListFree(r, 1)
 

src/net/mac.go

@@ -2,12 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// MAC address manipulations
-
 package net
 
-import "errors"
-
 const hexDigit = "0123456789abcdef"
 
 // A HardwareAddr represents a physical hardware address.
@@ -82,5 +78,5 @@ func ParseMAC(s string) (hw HardwareAddr, err error) {
 	return hw, nil
 
 error:
-	return nil, errors.New("invalid MAC address: " + s)
+	return nil, &AddrError{Err: "invalid MAC address", Addr: s}
 }

src/net/net.go

@@ -244,13 +244,6 @@ func (c *conn) File() (f *os.File, err error) {
 	return
 }
 
-// An Error represents a network error.
-type Error interface {
-	error
-	Timeout() bool   // Is the error a timeout?
-	Temporary() bool // Is the error temporary?
-}
-
 // PacketConn is a generic packet-oriented network connection.
 //
 // Multiple goroutines may invoke methods on a PacketConn simultaneously.
@@ -314,6 +307,13 @@ type Listener interface {
 	Addr() Addr
 }
 
+// An Error represents a network error.
+type Error interface {
+	error
+	Timeout() bool   // Is the error a timeout?
+	Temporary() bool // Is the error temporary?
+}
+
 // Various errors contained in OpError.
 var (
 	// For connection setup and write operations.
@@ -377,15 +377,6 @@ func (e *OpError) Error() string {
 	return s
 }
 
-type temporary interface {
-	Temporary() bool
-}
-
-func (e *OpError) Temporary() bool {
-	t, ok := e.Err.(temporary)
-	return ok && t.Temporary()
-}
-
 var noDeadline = time.Time{}
 
 type timeout interface {
@@ -393,16 +384,45 @@ type timeout interface {
 }
 
 func (e *OpError) Timeout() bool {
+	if ne, ok := e.Err.(*os.SyscallError); ok {
+		t, ok := ne.Err.(timeout)
+		return ok && t.Timeout()
+	}
 	t, ok := e.Err.(timeout)
 	return ok && t.Timeout()
 }
 
+type temporary interface {
+	Temporary() bool
+}
+
+func (e *OpError) Temporary() bool {
+	if ne, ok := e.Err.(*os.SyscallError); ok {
+		t, ok := ne.Err.(temporary)
+		return ok && t.Temporary()
+	}
+	t, ok := e.Err.(temporary)
+	return ok && t.Temporary()
+}
+
 type timeoutError struct{}
 
 func (e *timeoutError) Error() string   { return "i/o timeout" }
 func (e *timeoutError) Timeout() bool   { return true }
 func (e *timeoutError) Temporary() bool { return true }
 
+// A ParseError is the error type of literal network address parsers.
+type ParseError struct {
+	// Type is the type of string that was expected, such as
+	// "IP address", "CIDR address".
+	Type string
+
+	// Text is the malformed text string.
+	Text string
+}
+
+func (e *ParseError) Error() string { return "invalid " + e.Type + ": " + e.Text }
+
 type AddrError struct {
 	Err  string
 	Addr string
@@ -419,14 +439,14 @@ func (e *AddrError) Error() string {
 	return s
 }
 
-func (e *AddrError) Temporary() bool { return false }
 func (e *AddrError) Timeout() bool   { return false }
+func (e *AddrError) Temporary() bool { return false }
 
 type UnknownNetworkError string
 
 func (e UnknownNetworkError) Error() string   { return "unknown network " + string(e) }
-func (e UnknownNetworkError) Temporary() bool { return false }
 func (e UnknownNetworkError) Timeout() bool   { return false }
+func (e UnknownNetworkError) Temporary() bool { return false }
 
 type InvalidAddrError string
 

src/net/sendfile_dragonfly.go

@@ -99,5 +99,8 @@ func sendFile(c *netFD, r io.Reader) (written int64, err error, handled bool) {
 	if lr != nil {
 		lr.N = remain
 	}
+	if err != nil {
+		err = os.NewSyscallError("sendfile", err)
+	}
 	return written, err, written > 0
 }

src/net/sendfile_freebsd.go

@@ -99,5 +99,8 @@ func sendFile(c *netFD, r io.Reader) (written int64, err error, handled bool) {
 	if lr != nil {
 		lr.N = remain
 	}
+	if err != nil {
+		err = os.NewSyscallError("sendfile", err)
+	}
 	return written, err, written > 0
 }

src/net/sendfile_linux.go

@@ -72,5 +72,8 @@ func sendFile(c *netFD, r io.Reader) (written int64, err error, handled bool) {
 	if lr != nil {
 		lr.N = remain
 	}
+	if err != nil {
+		err = os.NewSyscallError("sendfile", err)
+	}
 	return written, err, written > 0
 }

src/net/sendfile_windows.go

@@ -46,7 +46,7 @@ func sendFile(fd *netFD, r io.Reader) (written int64, err error, handled bool) {
 		return syscall.TransmitFile(o.fd.sysfd, o.handle, o.qty, 0, &o.o, nil, syscall.TF_WRITE_BEHIND)
 	})
 	if err != nil {
-		return 0, err, false
+		return 0, os.NewSyscallError("transmitfile", err), false
 	}
 	if lr != nil {
 		lr.N -= int64(done)

src/net/sock_cloexec.go

@@ -9,7 +9,10 @@
 
 package net
 
-import "syscall"
+import (
+	"os"
+	"syscall"
+)
 
 // Wrapper around the socket system call that marks the returned file
 // descriptor as nonblocking and close-on-exec.
@@ -20,8 +23,12 @@ func sysSocket(family, sotype, proto int) (int, error) {
 	// introduced in 10 kernel. If we get an EINVAL error on Linux
 	// or EPROTONOSUPPORT error on FreeBSD, fall back to using
 	// socket without them.
-	if err == nil || (err != syscall.EPROTONOSUPPORT && err != syscall.EINVAL) {
-		return s, err
+	switch err {
+	case nil:
+		return s, nil
+	default:
+		return -1, os.NewSyscallError("socket", err)
+	case syscall.EPROTONOSUPPORT, syscall.EINVAL:
 	}
 
 	// See ../syscall/exec_unix.go for description of ForkLock.
@@ -32,11 +39,11 @@ func sysSocket(family, sotype, proto int) (int, error) {
 	}
 	syscall.ForkLock.RUnlock()
 	if err != nil {
-		return -1, err
+		return -1, os.NewSyscallError("socket", err)
 	}
 	if err = syscall.SetNonblock(s, true); err != nil {
 		closeFunc(s)
-		return -1, err
+		return -1, os.NewSyscallError("setnonblock", err)
 	}
 	return s, nil
 }
@@ -50,8 +57,10 @@ func accept(s int) (int, syscall.Sockaddr, error) {
 	// get an ENOSYS error on both Linux and FreeBSD, or EINVAL
 	// error on Linux, fall back to using accept.
 	switch err {
-	default: // nil and errors other than the ones listed
-		return ns, sa, err
+	case nil:
+		return ns, sa, nil
+	default: // errors other than the ones listed
+		return -1, sa, os.NewSyscallError("accept4", err)
 	case syscall.ENOSYS: // syscall missing
 	case syscall.EINVAL: // some Linux use this instead of ENOSYS
 	case syscall.EACCES: // some Linux use this instead of ENOSYS
@@ -68,11 +77,11 @@ func accept(s int) (int, syscall.Sockaddr, error) {
 		syscall.CloseOnExec(ns)
 	}
 	if err != nil {
-		return -1, nil, err
+		return -1, nil, os.NewSyscallError("accept", err)
 	}
 	if err = syscall.SetNonblock(ns, true); err != nil {
 		closeFunc(ns)
-		return -1, nil, err
+		return -1, nil, os.NewSyscallError("setnonblock", err)
 	}
 	return ns, sa, nil
 }

src/net/sock_windows.go

@@ -4,7 +4,10 @@
 
 package net
 
-import "syscall"
+import (
+	"os"
+	"syscall"
+)
 
 func maxListenerBacklog() int {
 	// TODO: Implement this
@@ -20,5 +23,8 @@ func sysSocket(family, sotype, proto int) (syscall.Handle, error) {
 		syscall.CloseOnExec(s)
 	}
 	syscall.ForkLock.RUnlock()
-	return s, err
+	if err != nil {
+		return syscall.InvalidHandle, os.NewSyscallError("socket", err)
+	}
+	return s, nil
 }

src/net/sys_cloexec.go

@@ -9,7 +9,10 @@
 
 package net
 
-import "syscall"
+import (
+	"os"
+	"syscall"
+)
 
 // Wrapper around the socket system call that marks the returned file
 // descriptor as nonblocking and close-on-exec.
@@ -22,11 +25,11 @@ func sysSocket(family, sotype, proto int) (int, error) {
 	}
 	syscall.ForkLock.RUnlock()
 	if err != nil {
-		return -1, err
+		return -1, os.NewSyscallError("socket", err)
 	}
 	if err = syscall.SetNonblock(s, true); err != nil {
 		closeFunc(s)
-		return -1, err
+		return -1, os.NewSyscallError("setnonblock", err)
 	}
 	return s, nil
 }
@@ -44,11 +47,11 @@ func accept(s int) (int, syscall.Sockaddr, error) {
 		syscall.CloseOnExec(ns)
 	}
 	if err != nil {
-		return -1, nil, err
+		return -1, nil, os.NewSyscallError("accept", err)
 	}
 	if err = syscall.SetNonblock(ns, true); err != nil {
 		closeFunc(ns)
-		return -1, nil, err
+		return -1, nil, os.NewSyscallError("setnonblock", err)
 	}
 	return ns, sa, nil
 }

src/net/tcpsockopt_windows.go

@@ -28,5 +28,5 @@ func setKeepAlivePeriod(fd *netFD, d time.Duration) error {
 	ret := uint32(0)
 	size := uint32(unsafe.Sizeof(ka))
 	err := syscall.WSAIoctl(fd.sysfd, syscall.SIO_KEEPALIVE_VALS, (*byte)(unsafe.Pointer(&ka)), size, nil, 0, &ret, nil, 0)
-	return os.NewSyscallError("WSAIoctl", err)
+	return os.NewSyscallError("wsaioctl", err)
 }