net, os, syscall: Plan 9: adjust error handling

syscall: Use NewError for all system errors and introduce
        some new errors for compatibility with other packages
        and proper error handling in net. Also introduce
        Temporary and Timeout methods on ErrorString.

net: Make errors from dial, accept, listen functions follow the
        OpError standard and discern whether the underlying
        error came from syscall. Since Plan 9 uses a correspondence
        between file and network operations, all system error
        reporting happens through the underlying file operation.
        In Go code, we go through package os for file operations,
        so there is another level of indirection in error types.
        This change allows us to compare the errors with those in
        package syscall, when appropriate.

os: Just use the error string already present in package os,
        instead of calling out to package syscall.

R=rsc, ality, rminnich, bradfitz
CC=golang-dev
https://golang.org/cl/7398054

src/pkg/net/ipsock_plan9.go

@@ -9,6 +9,7 @@ package net
 import (
 	"errors"
 	"os"
+	"syscall"
 )
 
 // /sys/include/ape/sys/socket.h:/SOMAXCONN
@@ -104,50 +105,58 @@ func startPlan9(net string, addr Addr) (ctl *os.File, dest, proto, name string,
 	return f, dest, proto, string(buf[:n]), nil
 }
 
-func dialPlan9(net string, laddr, raddr Addr) (*netFD, error) {
+func netErr(e error) {
+	oe, ok := e.(*OpError)
+	if !ok {
+		return
+	}
+	if pe, ok := oe.Err.(*os.PathError); ok {
+		if _, ok = pe.Err.(syscall.ErrorString); ok {
+			oe.Err = pe.Err
+		}
+	}
+}
+
+func dialPlan9(net string, laddr, raddr Addr) (fd *netFD, err error) {
+	defer func() { netErr(err) }()
 	f, dest, proto, name, err := startPlan9(net, raddr)
 	if err != nil {
-		return nil, err
+		return nil, &OpError{"dial", net, raddr, err}
 	}
 	_, err = f.WriteString("connect " + dest)
 	if err != nil {
 		f.Close()
-		return nil, err
+		return nil, &OpError{"dial", f.Name(), raddr, err}
 	}
 	data, err := os.OpenFile("/net/"+proto+"/"+name+"/data", os.O_RDWR, 0)
 	if err != nil {
 		f.Close()
-		return nil, err
+		return nil, &OpError{"dial", net, raddr, err}
 	}
 	laddr, err = readPlan9Addr(proto, "/net/"+proto+"/"+name+"/local")
 	if err != nil {
 		data.Close()
 		f.Close()
-		return nil, err
-	}
-	raddr, err = readPlan9Addr(proto, "/net/"+proto+"/"+name+"/remote")
-	if err != nil {
-		data.Close()
-		f.Close()
-		return nil, err
+		return nil, &OpError{"dial", proto, raddr, err}
 	}
 	return newFD(proto, name, f, data, laddr, raddr), nil
 }
 
-func listenPlan9(net string, laddr Addr) (*netFD, error) {
+func listenPlan9(net string, laddr Addr) (fd *netFD, err error) {
+	defer func() { netErr(err) }()
 	f, dest, proto, name, err := startPlan9(net, laddr)
 	if err != nil {
-		return nil, err
+		return nil, &OpError{"listen", net, laddr, err}
 	}
 	_, err = f.WriteString("announce " + dest)
 	if err != nil {
 		f.Close()
-		return nil, err
+		return nil, &OpError{"announce", proto, laddr, err}
 	}
 	laddr, err = readPlan9Addr(proto, "/net/"+proto+"/"+name+"/local")
 	if err != nil {
 		f.Close()
-		return nil, err
+		return nil, &OpError{Op: "listen", Net: net, Err: err}
 	}
 	return newFD(proto, name, f, nil, laddr, nil), nil
 }
@@ -156,28 +165,29 @@ func (l *netFD) netFD() *netFD {
 	return newFD(l.proto, l.name, l.ctl, l.data, l.laddr, l.raddr)
 }
 
-func (l *netFD) acceptPlan9() (*netFD, error) {
+func (l *netFD) acceptPlan9() (fd *netFD, err error) {
+	defer func() { netErr(err) }()
 	f, err := os.Open(l.dir + "/listen")
 	if err != nil {
-		return nil, err
+		return nil, &OpError{"accept", l.dir + "/listen", l.laddr, err}
 	}
 	var buf [16]byte
 	n, err := f.Read(buf[:])
 	if err != nil {
 		f.Close()
-		return nil, err
+		return nil, &OpError{"accept", l.dir + "/listen", l.laddr, err}
 	}
 	name := string(buf[:n])
 	data, err := os.OpenFile("/net/"+l.proto+"/"+name+"/data", os.O_RDWR, 0)
 	if err != nil {
 		f.Close()
-		return nil, err
+		return nil, &OpError{"accept", l.proto, l.laddr, err}
 	}
 	raddr, err := readPlan9Addr(l.proto, "/net/"+l.proto+"/"+name+"/remote")
 	if err != nil {
 		data.Close()
 		f.Close()
-		return nil, err
+		return nil, &OpError{"accept", l.proto, l.laddr, err}
 	}
 	return newFD(l.proto, name, f, data, l.laddr, raddr), nil
 }

src/pkg/net/tcpsock_plan9.go

@@ -89,7 +89,7 @@ func dialTCP(net string, laddr, raddr *TCPAddr, deadline time.Time) (*TCPConn, e
 	switch net {
 	case "tcp", "tcp4", "tcp6":
 	default:
-		return nil, UnknownNetworkError(net)
+		return nil, &OpError{"dial", net, raddr, UnknownNetworkError(net)}
 	}
 	if raddr == nil {
 		return nil, &OpError{"dial", net, nil, errMissingAddress}
@@ -141,7 +141,7 @@ func (l *TCPListener) Close() error {
 	}
 	if _, err := l.fd.ctl.WriteString("hangup"); err != nil {
 		l.fd.ctl.Close()
-		return err
+		return &OpError{"close", l.fd.ctl.Name(), l.fd.laddr, err}
 	}
 	return l.fd.ctl.Close()
 }
@@ -171,7 +171,7 @@ func ListenTCP(net string, laddr *TCPAddr) (*TCPListener, error) {
 	switch net {
 	case "tcp", "tcp4", "tcp6":
 	default:
-		return nil, UnknownNetworkError(net)
+		return nil, &OpError{"listen", net, laddr, UnknownNetworkError(net)}
 	}
 	if laddr == nil {
 		laddr = &TCPAddr{}

src/pkg/os/exec/lp_plan9.go

@@ -8,7 +8,6 @@ import (
 	"errors"
 	"os"
 	"strings"
-	"syscall"
 )
 
 // ErrNotFound is the error resulting if a path search failed to find an executable file.
@@ -22,7 +21,7 @@ func findExecutable(file string) error {
 	if m := d.Mode(); !m.IsDir() && m&0111 != 0 {
 		return nil
 	}
-	return syscall.EPERM
+	return os.ErrPermission
 }
 
 // LookPath searches for an executable binary named file

src/pkg/syscall/syscall_plan9.go

@@ -23,6 +23,14 @@ func (e ErrorString) Error() string { return string(e) }
 // NewError converts s to an ErrorString, which satisfies the Error interface.
 func NewError(s string) error { return ErrorString(s) }
 
+func (e ErrorString) Temporary() bool {
+	return e == EINTR || e == EMFILE || e.Timeout()
+}
+
+func (e ErrorString) Timeout() bool {
+	return e == EBUSY || e == ETIMEDOUT
+}
+
 // A Note is a string describing a process note.
 // It implements the os.Signal interface.
 type Note string
@@ -37,9 +45,6 @@ var (
 	Stdin  = 0
 	Stdout = 1
 	Stderr = 2
-
-	EAFNOSUPPORT = NewError("address family not supported by protocol")
-	EISDIR       = NewError("file is a directory")
 )
 
 // For testing: clients can set this flag to force

src/pkg/syscall/zerrors_plan9_386.go

@@ -4,8 +4,6 @@
 
 package syscall
 
-import "errors"
-
 // Constants
 const (
 	// Invented values to support what package os expects.
@@ -28,12 +26,23 @@ const (
 
 // Errors
 var (
-	EINVAL       = errors.New("bad arg in system call")
-	ENOTDIR      = errors.New("not a directory")
-	ENOENT       = errors.New("file does not exist")
-	EEXIST       = errors.New("file already exists")
-	EIO          = errors.New("i/o error")
-	ENAMETOOLONG = errors.New("file name too long")
-	EPERM        = errors.New("permission denied")
-	EPLAN9       = errors.New("not supported by plan 9")
+	EINVAL       = NewError("bad arg in system call")
+	ENOTDIR      = NewError("not a directory")
+	EISDIR       = NewError("file is a directory")
+	ENOENT       = NewError("file does not exist")
+	EEXIST       = NewError("file already exists")
+	EMFILE       = NewError("no free file descriptors")
+	EIO          = NewError("i/o error")
+	ENAMETOOLONG = NewError("file name too long")
+	EINTR        = NewError("interrupted")
+	EPERM        = NewError("permission denied")
+	EBUSY        = NewError("no free devices")
+	ETIMEDOUT    = NewError("connection timed out")
+	EPLAN9       = NewError("not supported by plan 9")
+
+	// The following errors do not correspond to any
+	// Plan 9 system messages. Invented to support
+	// what package os and others expect.
+	EACCES       = NewError("access permission denied")
+	EAFNOSUPPORT = NewError("address family not supported by protocol")
 )

src/pkg/syscall/zerrors_plan9_amd64.go

@@ -4,8 +4,6 @@
 
 package syscall
 
-import "errors"
-
 // Constants
 const (
 	// Invented values to support what package os expects.
@@ -28,12 +26,23 @@ const (
 
 // Errors
 var (
-	EINVAL       = errors.New("bad arg in system call")
-	ENOTDIR      = errors.New("not a directory")
-	ENOENT       = errors.New("file does not exist")
-	EEXIST       = errors.New("file already exists")
-	EIO          = errors.New("i/o error")
-	ENAMETOOLONG = errors.New("file name too long")
-	EPERM        = errors.New("permission denied")
-	EPLAN9       = errors.New("not supported by plan 9")
+	EINVAL       = NewError("bad arg in system call")
+	ENOTDIR      = NewError("not a directory")
+	EISDIR       = NewError("file is a directory")
+	ENOENT       = NewError("file does not exist")
+	EEXIST       = NewError("file already exists")
+	EMFILE       = NewError("no free file descriptors")
+	EIO          = NewError("i/o error")
+	ENAMETOOLONG = NewError("file name too long")
+	EINTR        = NewError("interrupted")
+	EPERM        = NewError("permission denied")
+	EBUSY        = NewError("no free devices")
+	ETIMEDOUT    = NewError("connection timed out")
+	EPLAN9       = NewError("not supported by plan 9")
+
+	// The following errors do not correspond to any
+	// Plan 9 system messages. Invented to support
+	// what package os and others expect.
+	EACCES       = NewError("access permission denied")
+	EAFNOSUPPORT = NewError("address family not supported by protocol")
 )