net: plan9 changes for default net directory

This change include updates to the probeIPv4Stack
and probeIPv6Stack to ensure that one or both
protocols are supported by ip(3).
The addition of fdMutex to netFD fixes the
TestTCPConcurrentAccept failures.
Additional changes add support for keepalive.

R=golang-codereviews, 0intro
CC=golang-codereviews, rsc
https://golang.org/cl/49920048

src/pkg/net/fd_plan9.go

@@ -13,12 +13,23 @@ import (
 
 // Network file descritor.
 type netFD struct {
-	proto, name, dir string
-	ctl, data        *os.File
-	laddr, raddr     Addr
+	// locking/lifetime of sysfd + serialize access to Read and Write methods
+	fdmu fdMutex
+
+	// immutable until Close
+	proto        string
+	n            string
+	dir          string
+	ctl, data    *os.File
+	laddr, raddr Addr
 }
 
+var (
+	netdir string // default network
+)
+
 func sysInit() {
+	netdir = "/net"
 }
 
 func dial(net string, ra Addr, dialer func(time.Time) (Conn, error), deadline time.Time) (Conn, error) {
@@ -27,16 +38,99 @@ func dial(net string, ra Addr, dialer func(time.Time) (Conn, error), deadline ti
 	return dialChannel(net, ra, dialer, deadline)
 }
 
-func newFD(proto, name string, ctl, data *os.File, laddr, raddr Addr) *netFD {
-	return &netFD{proto, name, "/net/" + proto + "/" + name, ctl, data, laddr, raddr}
+func newFD(proto, name string, ctl, data *os.File, laddr, raddr Addr) (*netFD, error) {
+	return &netFD{proto: proto, n: name, dir: netdir + "/" + proto + "/" + name, ctl: ctl, data: data, laddr: laddr, raddr: raddr}, nil
+}
+
+func (fd *netFD) init() error {
+	// stub for future fd.pd.Init(fd)
+	return nil
+}
+
+func (fd *netFD) name() string {
+	var ls, rs string
+	if fd.laddr != nil {
+		ls = fd.laddr.String()
+	}
+	if fd.raddr != nil {
+		rs = fd.raddr.String()
+	}
+	return fd.proto + ":" + ls + "->" + rs
 }
 
 func (fd *netFD) ok() bool { return fd != nil && fd.ctl != nil }
 
+func (fd *netFD) destroy() {
+	if !fd.ok() {
+		return
+	}
+	err := fd.ctl.Close()
+	if fd.data != nil {
+		if err1 := fd.data.Close(); err1 != nil && err == nil {
+			err = err1
+		}
+	}
+	fd.ctl = nil
+	fd.data = nil
+}
+
+// Add a reference to this fd.
+// Returns an error if the fd cannot be used.
+func (fd *netFD) incref() error {
+	if !fd.fdmu.Incref() {
+		return errClosing
+	}
+	return nil
+}
+
+// Remove a reference to this FD and close if we've been asked to do so
+// (and there are no references left).
+func (fd *netFD) decref() {
+	if fd.fdmu.Decref() {
+		fd.destroy()
+	}
+}
+
+// Add a reference to this fd and lock for reading.
+// Returns an error if the fd cannot be used.
+func (fd *netFD) readLock() error {
+	if !fd.fdmu.RWLock(true) {
+		return errClosing
+	}
+	return nil
+}
+
+// Unlock for reading and remove a reference to this FD.
+func (fd *netFD) readUnlock() {
+	if fd.fdmu.RWUnlock(true) {
+		fd.destroy()
+	}
+}
+
+// Add a reference to this fd and lock for writing.
+// Returns an error if the fd cannot be used.
+func (fd *netFD) writeLock() error {
+	if !fd.fdmu.RWLock(false) {
+		return errClosing
+	}
+	return nil
+}
+
+// Unlock for writing and remove a reference to this FD.
+func (fd *netFD) writeUnlock() {
+	if fd.fdmu.RWUnlock(false) {
+		fd.destroy()
+	}
+}
+
 func (fd *netFD) Read(b []byte) (n int, err error) {
 	if !fd.ok() || fd.data == nil {
 		return 0, syscall.EINVAL
 	}
+	if err := fd.readLock(); err != nil {
+		return 0, err
+	}
+	defer fd.readUnlock()
 	n, err = fd.data.Read(b)
 	if fd.proto == "udp" && err == io.EOF {
 		n = 0
@@ -49,6 +143,10 @@ func (fd *netFD) Write(b []byte) (n int, err error) {
 	if !fd.ok() || fd.data == nil {
 		return 0, syscall.EINVAL
 	}
+	if err := fd.writeLock(); err != nil {
+		return 0, err
+	}
+	defer fd.writeUnlock()
 	return fd.data.Write(b)
 }
 
@@ -67,6 +165,9 @@ func (fd *netFD) CloseWrite() error {
 }
 
 func (fd *netFD) Close() error {
+	if !fd.fdmu.IncrefAndClose() {
+		return errClosing
+	}
 	if !fd.ok() {
 		return syscall.EINVAL
 	}

src/pkg/net/file_plan9.go

@@ -43,7 +43,7 @@ func newFileFD(f *os.File) (net *netFD, err error) {
 	}
 	comp := splitAtBytes(path, "/")
 	n := len(comp)
-	if n < 3 || comp[0] != "net" {
+	if n < 3 || comp[0][0:3] != "net" {
 		return nil, syscall.EPLAN9
 	}
 
@@ -58,7 +58,7 @@ func newFileFD(f *os.File) (net *netFD, err error) {
 		}
 		defer close(fd)
 
-		dir := "/net/" + comp[n-2]
+		dir := netdir + "/" + comp[n-2]
 		ctl = os.NewFile(uintptr(fd), dir+"/"+file)
 		ctl.Seek(0, 0)
 		var buf [16]byte
@@ -71,19 +71,19 @@ func newFileFD(f *os.File) (net *netFD, err error) {
 		if len(comp) < 4 {
 			return nil, errors.New("could not find control file for connection")
 		}
-		dir := "/net/" + comp[1] + "/" + name
+		dir := netdir + "/" + comp[1] + "/" + name
 		ctl, err = os.OpenFile(dir+"/ctl", os.O_RDWR, 0)
 		if err != nil {
 			return nil, err
 		}
 		defer close(int(ctl.Fd()))
 	}
-	dir := "/net/" + comp[1] + "/" + name
+	dir := netdir + "/" + comp[1] + "/" + name
 	laddr, err := readPlan9Addr(comp[1], dir+"/local")
 	if err != nil {
 		return nil, err
 	}
-	return newFD(comp[1], name, ctl, nil, laddr, nil), nil
+	return newFD(comp[1], name, ctl, nil, laddr, nil)
 }
 
 func newFileConn(f *os.File) (c Conn, err error) {

src/pkg/net/ipsock_plan9.go

@@ -12,19 +12,45 @@ import (
 	"syscall"
 )
 
+func probe(filename, query string, bufSize int) bool {
+	var file *file
+	var err error
+	if file, err = open(filename); err != nil {
+		return false
+	}
+
+	r := false
+	for line, ok := file.readLine(); ok && !r; line, ok = file.readLine() {
+		f := getFields(line)
+		if len(f) < 3 {
+			continue
+		}
+		for i := 0; i < len(f); i++ {
+			if query == f[i] {
+				r = true
+				break
+			}
+		}
+	}
+	file.close()
+	return r
+}
+
 func probeIPv4Stack() bool {
-	// TODO(mikio): implement this when Plan 9 supports IPv6-only
-	// kernel.
-	return true
+	return probe(netdir+"/ipselftab", "127.0.0.1", 128)
 }
 
 // probeIPv6Stack returns two boolean values.  If the first boolean
 // value is true, kernel supports basic IPv6 functionality.  If the
 // second boolean value is true, kernel supports IPv6 IPv4-mapping.
 func probeIPv6Stack() (supportsIPv6, supportsIPv4map bool) {
-	// TODO(mikio): implement this once Plan 9 gets an IPv6
-	// protocol stack implementation.
-	return false, false
+	// Plan 9 uses IPv6 natively, see ip(3).
+	r := probe(netdir+"/iproute", "6i", 128)
+	v := false
+	if r {
+		v = probe(netdir+"/iproute", "4b", 128)
+	}
+	return r, v
 }
 
 // parsePlan9Addr parses address of the form [ip!]port (e.g. 127.0.0.1!80).
@@ -133,18 +159,18 @@ func dialPlan9(net string, laddr, raddr Addr) (fd *netFD, err error) {
 		f.Close()
 		return nil, &OpError{"dial", f.Name(), raddr, err}
 	}
-	data, err := os.OpenFile("/net/"+proto+"/"+name+"/data", os.O_RDWR, 0)
+	data, err := os.OpenFile(netdir+"/"+proto+"/"+name+"/data", os.O_RDWR, 0)
 	if err != nil {
 		f.Close()
 		return nil, &OpError{"dial", net, raddr, err}
 	}
-	laddr, err = readPlan9Addr(proto, "/net/"+proto+"/"+name+"/local")
+	laddr, err = readPlan9Addr(proto, netdir+"/"+proto+"/"+name+"/local")
 	if err != nil {
 		data.Close()
 		f.Close()
 		return nil, &OpError{"dial", proto, raddr, err}
 	}
-	return newFD(proto, name, f, data, laddr, raddr), nil
+	return newFD(proto, name, f, data, laddr, raddr)
 }
 
 func listenPlan9(net string, laddr Addr) (fd *netFD, err error) {
@@ -158,20 +184,24 @@ func listenPlan9(net string, laddr Addr) (fd *netFD, err error) {
 		f.Close()
 		return nil, &OpError{"announce", proto, laddr, err}
 	}
-	laddr, err = readPlan9Addr(proto, "/net/"+proto+"/"+name+"/local")
+	laddr, err = readPlan9Addr(proto, netdir+"/"+proto+"/"+name+"/local")
 	if err != nil {
 		f.Close()
 		return nil, &OpError{Op: "listen", Net: net, Err: err}
 	}
-	return newFD(proto, name, f, nil, laddr, nil), nil
+	return newFD(proto, name, f, nil, laddr, nil)
 }
 
-func (l *netFD) netFD() *netFD {
-	return newFD(l.proto, l.name, l.ctl, l.data, l.laddr, l.raddr)
+func (l *netFD) netFD() (*netFD, error) {
+	return newFD(l.proto, l.n, l.ctl, l.data, l.laddr, l.raddr)
 }
 
 func (l *netFD) acceptPlan9() (fd *netFD, err error) {
 	defer func() { netErr(err) }()
+	if err := l.readLock(); err != nil {
+		return nil, err
+	}
+	defer l.readUnlock()
 	f, err := os.Open(l.dir + "/listen")
 	if err != nil {
 		return nil, &OpError{"accept", l.dir + "/listen", l.laddr, err}
@@ -183,16 +213,16 @@ func (l *netFD) acceptPlan9() (fd *netFD, err error) {
 		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)
+	data, err := os.OpenFile(netdir+"/"+l.proto+"/"+name+"/data", os.O_RDWR, 0)
 	if err != nil {
 		f.Close()
 		return nil, &OpError{"accept", l.proto, l.laddr, err}
 	}
-	raddr, err := readPlan9Addr(l.proto, "/net/"+l.proto+"/"+name+"/remote")
+	raddr, err := readPlan9Addr(l.proto, netdir+"/"+l.proto+"/"+name+"/remote")
 	if err != nil {
 		data.Close()
 		f.Close()
 		return nil, &OpError{"accept", l.proto, l.laddr, err}
 	}
-	return newFD(l.proto, name, f, data, l.laddr, raddr), nil
+	return newFD(l.proto, name, f, data, l.laddr, raddr)
 }

src/pkg/net/lookup_plan9.go

@@ -49,7 +49,7 @@ func queryCS(net, host, service string) (res []string, err error) {
 	if host == "" {
 		host = "*"
 	}
-	return query("/net/cs", net+"!"+host+"!"+service, 128)
+	return query(netdir+"/cs", net+"!"+host+"!"+service, 128)
 }
 
 func queryCS1(net string, ip IP, port int) (clone, dest string, err error) {
@@ -70,7 +70,7 @@ func queryCS1(net string, ip IP, port int) (clone, dest string, err error) {
 }
 
 func queryDNS(addr string, typ string) (res []string, err error) {
-	return query("/net/dns", addr+" "+typ, 1024)
+	return query(netdir+"/dns", addr+" "+typ, 1024)
 }
 
 // toLower returns a lower-case version of in. Restricting us to
@@ -97,7 +97,7 @@ func toLower(in string) string {
 // lookupProtocol looks up IP protocol name and returns
 // the corresponding protocol number.
 func lookupProtocol(name string) (proto int, err error) {
-	lines, err := query("/net/cs", "!protocol="+toLower(name), 128)
+	lines, err := query(netdir+"/cs", "!protocol="+toLower(name), 128)
 	if err != nil {
 		return 0, err
 	}
@@ -117,7 +117,7 @@ func lookupProtocol(name string) (proto int, err error) {
 }
 
 func lookupHost(host string) (addrs []string, err error) {
-	// Use /net/cs instead of /net/dns because cs knows about
+	// Use netdir/cs instead of netdir/dns because cs knows about
 	// host names in local network (e.g. from /lib/ndb/local)
 	lines, err := queryCS("net", host, "1")
 	if err != nil {

src/pkg/net/sockopt_plan9.go

+// 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.
+
+package net
+
+func setKeepAlive(fd *netFD, keepalive bool) error {
+	if keepalive {
+		_, e := fd.ctl.WriteAt([]byte("keepalive"), 0)
+		return e
+	}
+	return nil
+}

src/pkg/net/tcpsock_plan9.go

@@ -62,12 +62,18 @@ func (c *TCPConn) SetLinger(sec int) error {
 // SetKeepAlive sets whether the operating system should send
 // keepalive messages on the connection.
 func (c *TCPConn) SetKeepAlive(keepalive bool) error {
-	return syscall.EPLAN9
+	if !c.ok() {
+		return syscall.EPLAN9
+	}
+	return setKeepAlive(c.fd, keepalive)
 }
 
 // SetKeepAlivePeriod sets period between keep alives.
 func (c *TCPConn) SetKeepAlivePeriod(d time.Duration) error {
-	return syscall.EPLAN9
+	if !c.ok() {
+		return syscall.EPLAN9
+	}
+	return setKeepAlivePeriod(c.fd, d)
 }
 
 // SetNoDelay controls whether the operating system should delay

src/pkg/net/tcpsockopt_plan9.go

+// 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.
+
+// TCP socket options for plan9
+
+package net
+
+import (
+	"time"
+)
+
+// Set keep alive period.
+func setKeepAlivePeriod(fd *netFD, d time.Duration) error {
+	cmd := "keepalive " + string(int64(d/time.Millisecond))
+	_, e := fd.ctl.WriteAt([]byte(cmd), 0)
+	return e
+}

src/pkg/net/udpsock_plan9.go

@@ -190,7 +190,8 @@ func ListenUDP(net string, laddr *UDPAddr) (*UDPConn, error) {
 	if err != nil {
 		return nil, err
 	}
-	return newUDPConn(l.netFD()), nil
+	fd, err := l.netFD()
+	return newUDPConn(fd), err
 }
 
 // ListenMulticastUDP listens for incoming multicast UDP packets