document Conn interface better, in preparation

for per-method interface documentation
by mkdoc.pl.

implement timeouts on network reads
and use them in dns client.

also added locks on i/o to ensure writes
are not interlaced.

R=r
DELTA=340  (272 added, 25 deleted, 43 changed)
OCL=25799
CL=25874

src/lib/net/dnsclient.go

@@ -62,14 +62,15 @@ func _Exchange(cfg *_DNS_Config, c Conn, name string) (m *_DNS_Msg, err *os.Erro
 			return nil, err
 		}
 
-		// TODO(rsc): set up timeout or call ReadTimeout.
+		c.SetReadTimeout(1e9);	// nanoseconds
-		// right now net does not support that.
 
 		buf := make([]byte, 2000);	// More than enough.
 		n, err = c.Read(buf);
+		if err == os.EAGAIN {
+			continue;
+		}
 		if err != nil {
-			// TODO(rsc): only continue if timed out
+			return nil, err;
-			continue
 		}
 		buf = buf[0:n];
 		in := new(_DNS_Msg);
@@ -84,7 +85,7 @@ func _Exchange(cfg *_DNS_Config, c Conn, name string) (m *_DNS_Msg, err *os.Erro
 
 // Find answer for name in dns message.
 // On return, if err == nil, addrs != nil.
-// TODO(rsc): Maybe return [][]byte (==[]IPAddr) instead?
+// TODO(rsc): Maybe return []IP instead?
 func answer(name string, dns *_DNS_Msg) (addrs []string, err *os.Error) {
 	addrs = make([]string, 0, len(dns.answer));
 

src/lib/net/dnsconfig.go

@@ -29,7 +29,7 @@ var _DNS_configError *os.Error;
 // of the host name to get the default search domain.
 // We assume it's in resolv.conf anyway.
 func _DNS_ReadConfig() (*_DNS_Config, *os.Error) {
-	// TODO(rsc): 6g won't let me use "file :="
+	// TODO(rsc): 6g won't let me say file, err :=
 	var file *file;
 	var err *os.Error;
 	file, err = open("/etc/resolv.conf");

src/lib/net/fd.go

@@ -10,6 +10,7 @@ import (
 	"net";
 	"once";
 	"os";
+	"sync";
 	"syscall";
 )
 
@@ -24,6 +25,14 @@ type netFD struct {
 	laddr string;
 	raddr string;
 
+	// owned by client
+	rdeadline_delta int64;
+	rdeadline int64;
+	rio sync.Mutex;
+	wdeadline_delta int64;
+	wdeadline int64;
+	wio sync.Mutex;
+
 	// owned by fd wait server
 	ncr, ncw int;
 }
@@ -41,6 +50,14 @@ func setNonblock(fd int64) *os.Error {
 	return nil
 }
 
+// Make reads/writes blocking; last gasp, so no error checking.
+func setBlock(fd int64) {
+	flags, e := syscall.Fcntl(fd, syscall.F_GETFL, 0);
+	if e != 0 {
+		return;
+	}
+	syscall.Fcntl(fd, syscall.F_SETFL, flags & ^syscall.O_NONBLOCK);
+}
 
 // A pollServer helps FDs determine when to retry a non-blocking
 // read or write after they get EAGAIN.  When an FD needs to wait,
@@ -76,6 +93,7 @@ type pollServer struct {
 	pr, pw *os.FD;
 	pending map[int64] *netFD;
 	poll *pollster;	// low-level OS hooks
+	deadline int64;	// next deadline (nsec since 1970)
 }
 func (s *pollServer) Run();
 
@@ -109,18 +127,24 @@ func newPollServer() (s *pollServer, err *os.Error) {
 
 func (s *pollServer) AddFD(fd *netFD, mode int) {
 	if err := s.poll.AddFD(fd.fd, mode, false); err != nil {
-		print("pollServer AddFD: ", err.String(), "\n");
+		panicln("pollServer AddFD ", fd.fd, ": ", err.String(), "\n");
 		return
 	}
 
+	var t int64;
 	key := fd.fd << 1;
 	if mode == 'r' {
 		fd.ncr++;
+		t = fd.rdeadline;
 	} else {
 		fd.ncw++;
 		key++;
+		t = fd.wdeadline;
+	}
+	s.pending[key] = fd;
+	if t > 0 && (s.deadline == 0 || t < s.deadline) {
+		s.deadline = t;
 	}
-	s.pending[key] = fd
 }
 
 func (s *pollServer) LookupFD(fd int64, mode int) *netFD {
@@ -136,14 +160,88 @@ func (s *pollServer) LookupFD(fd int64, mode int) *netFD {
 	return netfd
 }
 
+func (s *pollServer) WakeFD(fd *netFD, mode int) {
+	if mode == 'r' {
+		for fd.ncr > 0 {
+			fd.ncr--;
+			fd.cr <- fd
+		}
+	} else {
+		for fd.ncw > 0 {
+			fd.ncw--;
+			fd.cw <- fd
+		}
+	}
+}
+
+func (s *pollServer) Now() int64 {
+	sec, nsec, err := os.Time();
+	if err != nil {
+		panic("net: os.Time: ", err.String());
+	}
+	nsec += sec * 1e9;
+	return nsec;
+}
+
+func (s *pollServer) CheckDeadlines() {
+	now := s.Now();
+	// TODO(rsc): This will need to be handled more efficiently,
+	// probably with a heap indexed by wakeup time.
+
+	var next_deadline int64;
+	for key, fd := range s.pending {
+		var t int64;
+		var mode int;
+		if key&1 == 0 {
+			mode = 'r';
+		} else {
+			mode = 'w';
+		}
+		if mode == 'r' {
+			t = fd.rdeadline;
+		} else {
+			t = fd.wdeadline;
+		}
+		if t > 0 {
+			if t <= now {
+				s.pending[key] = nil, false;
+				if mode == 'r' {
+					s.poll.DelFD(fd.fd, mode);
+					fd.rdeadline = -1;
+				} else {
+					s.poll.DelFD(fd.fd, mode);
+					fd.wdeadline = -1;
+				}
+				s.WakeFD(fd, mode);
+			} else if next_deadline == 0 || t < next_deadline {
+				next_deadline = t;
+			}
+		}
+	}
+	s.deadline = next_deadline;
+}
+
 func (s *pollServer) Run() {
 	var scratch [100]byte;
 	for {
-		fd, mode, err := s.poll.WaitFD();
+		var t = s.deadline;
+		if t > 0 {
+			t = t - s.Now();
+			if t < 0 {
+				s.CheckDeadlines();
+				continue;
+			}
+		}
+		fd, mode, err := s.poll.WaitFD(t);
 		if err != nil {
 			print("pollServer WaitFD: ", err.String(), "\n");
 			return
 		}
+		if fd < 0 {
+			// Timeout happened.
+			s.CheckDeadlines();
+			continue;
+		}
 		if fd == s.pr.Fd() {
 			// Drain our wakeup pipe.
 			for nn, e := s.pr.Read(scratch); nn > 0; {
@@ -163,17 +261,7 @@ func (s *pollServer) Run() {
 				print("pollServer: unexpected wakeup for fd=", netfd, " mode=", string(mode), "\n");
 				continue
 			}
-			if mode == 'r' {
+			s.WakeFD(netfd, mode);
-				for netfd.ncr > 0 {
-					netfd.ncr--;
-					netfd.cr <- netfd
-				}
-			} else {
-				for netfd.ncw > 0 {
-					netfd.ncw--;
-					netfd.cw <- netfd
-				}
-			}
 		}
 	}
 }
@@ -231,6 +319,15 @@ func (fd *netFD) Close() *os.Error {
 	if fd == nil || fd.osfd == nil {
 		return os.EINVAL
 	}
+
+	// In case the user has set linger,
+	// switch to blocking mode so the close blocks.
+	// As long as this doesn't happen often,
+	// we can handle the extra OS processes.
+	// Otherwise we'll need to use the pollserver
+	// for Close too.  Sigh.
+	setBlock(fd.osfd.Fd());
+
 	e := fd.osfd.Close();
 	fd.osfd = nil;
 	fd.fd = -1;
@@ -241,8 +338,15 @@ func (fd *netFD) Read(p []byte) (n int, err *os.Error) {
 	if fd == nil || fd.osfd == nil {
 		return -1, os.EINVAL
 	}
+	fd.rio.Lock();
+	defer fd.rio.Unlock();
+	if fd.rdeadline_delta > 0 {
+		fd.rdeadline = pollserver.Now() + fd.rdeadline_delta;
+	} else {
+		fd.rdeadline = 0;
+	}
 	n, err = fd.osfd.Read(p);
-	for err == os.EAGAIN {
+	for err == os.EAGAIN && fd.rdeadline >= 0 {
 		pollserver.WaitRead(fd);
 		n, err = fd.osfd.Read(p)
 	}
@@ -253,21 +357,29 @@ func (fd *netFD) Write(p []byte) (n int, err *os.Error) {
 	if fd == nil || fd.osfd == nil {
 		return -1, os.EINVAL
 	}
-	// TODO(rsc): Lock fd while writing to avoid interlacing writes.
+	fd.wio.Lock();
+	defer fd.wio.Unlock();
+	if fd.wdeadline_delta > 0 {
+		fd.wdeadline = pollserver.Now() + fd.wdeadline_delta;
+	} else {
+		fd.wdeadline = 0;
+	}
 	err = nil;
 	nn := 0;
-	for nn < len(p) && err == nil {
+	for nn < len(p) {
-		// TODO(rsc): If os.FD.Write loops, have to use syscall instead.
 		n, err = fd.osfd.Write(p[nn:len(p)]);
-		for err == os.EAGAIN {
-			pollserver.WaitWrite(fd);
-			n, err = fd.osfd.Write(p[nn:len(p)])
-		}
 		if n > 0 {
 			nn += n
 		}
-		if n == 0 {
+		if nn == len(p) {
-			break
+			break;
+		}
+		if err == os.EAGAIN && fd.wdeadline >= 0 {
+			pollserver.WaitWrite(fd);
+			continue;
+		}
+		if n == 0 || err != nil {
+			break;
 		}
 	}
 	return nn, err

src/lib/net/fd_darwin.go

@@ -62,15 +62,45 @@ func (p *pollster) AddFD(fd int64, mode int, repeat bool) *os.Error {
 	return nil
 }
 
-func (p *pollster) WaitFD() (fd int64, mode int, err *os.Error) {
+func (p *pollster) DelFD(fd int64, mode int) {
+	var kmode int16;
+	if mode == 'r' {
+		kmode = syscall.EVFILT_READ
+	} else {
+		kmode = syscall.EVFILT_WRITE
+	}
+	var events [1]syscall.Kevent_t;
+	ev := &events[0];
+	ev.Ident = fd;
+	ev.Filter = kmode;
+
+	// EV_DELETE - delete event from kqueue list
+	// EV_RECEIPT - generate fake EV_ERROR as result of add,
+	//	rather than waiting for real event
+	ev.Flags = syscall.EV_DELETE | syscall.EV_RECEIPT;
+	syscall.Kevent(p.kq, events, events, nil);
+}
+
+func (p *pollster) WaitFD(nsec int64) (fd int64, mode int, err *os.Error) {
+	var t *syscall.Timespec;
 	for len(p.events) == 0 {
-		nn, e := syscall.Kevent(p.kq, nil, p.eventbuf, nil);
+		if nsec > 0 {
+			if t == nil {
+				t = new(syscall.Timespec);
+			}
+			t.Sec = nsec / 1e9;
+			t.Nsec = uint64(nsec % 1e9);
+		}
+		nn, e := syscall.Kevent(p.kq, nil, p.eventbuf, t);
 		if e != 0 {
-			if e == syscall.EAGAIN || e == syscall.EINTR {
+			if e == syscall.EINTR {
 				continue
 			}
 			return -1, 0, os.ErrnoToError(e)
 		}
+		if nn == 0 {
+			return -1, 0, nil;
+		}
 		p.events = p.eventbuf[0:nn]
 	}
 	ev := &p.events[0];

src/lib/net/fd_linux.go

@@ -44,19 +44,19 @@ func (p *pollster) AddFD(fd int64, mode int, repeat bool) *os.Error {
 	ev.Fd = int32(fd);
 	ev.Events, already = p.events[fd];
 	if !repeat {
-		ev.Events |= syscall.EPOLLONESHOT
+		ev.Events |= syscall.EPOLLONESHOT;
 	}
 	if mode == 'r' {
-		ev.Events |= readFlags
+		ev.Events |= readFlags;
 	} else {
-		ev.Events |= writeFlags
+		ev.Events |= writeFlags;
 	}
 
 	var op int64;
 	if already {
-		op = syscall.EPOLL_CTL_MOD
+		op = syscall.EPOLL_CTL_MOD;
 	} else {
-		op = syscall.EPOLL_CTL_ADD
+		op = syscall.EPOLL_CTL_ADD;
 	}
 	if e := syscall.Epoll_ctl(p.epfd, op, fd, &ev); e != 0 {
 		return os.ErrnoToError(e)
@@ -69,13 +69,13 @@ func (p *pollster) StopWaiting(fd int64, bits uint) {
 	events, already := p.events[fd];
 	if !already {
 		print("Epoll unexpected fd=", fd, "\n");
-		return
+		return;
 	}
 
 	// If syscall.EPOLLONESHOT is not set, the wait
 	// is a repeating wait, so don't change it.
 	if events & syscall.EPOLLONESHOT == 0 {
-		return
+		return;
 	}
 
 	// Disable the given bits.
@@ -87,50 +87,65 @@ func (p *pollster) StopWaiting(fd int64, bits uint) {
 		ev.Fd = int32(fd);
 		ev.Events = events;
 		if e := syscall.Epoll_ctl(p.epfd, syscall.EPOLL_CTL_MOD, fd, &ev); e != 0 {
-			print("Epoll modify fd=", fd, ": ", os.ErrnoToError(e).String(), "\n")
+			print("Epoll modify fd=", fd, ": ", os.ErrnoToError(e).String(), "\n");
 		}
-		p.events[fd] = events
+		p.events[fd] = events;
 	} else {
 		if e := syscall.Epoll_ctl(p.epfd, syscall.EPOLL_CTL_DEL, fd, nil); e != 0 {
-			print("Epoll delete fd=", fd, ": ", os.ErrnoToError(e).String(), "\n")
+			print("Epoll delete fd=", fd, ": ", os.ErrnoToError(e).String(), "\n");
 		}
-		p.events[fd] = 0, false
+		p.events[fd] = 0, false;
 	}
 }
 
-func (p *pollster) WaitFD() (fd int64, mode int, err *os.Error) {
+func (p *pollster) DelFD(fd int64, mode int) {
+	if mode == 'r' {
+		p.StopWaiting(fd, readFlags);
+	} else {
+		p.StopWaiting(fd, writeFlags);
+	}
+}
+
+func (p *pollster) WaitFD(nsec int64) (fd int64, mode int, err *os.Error) {
 	// Get an event.
 	var evarray [1]syscall.EpollEvent;
 	ev := &evarray[0];
-	n, e := syscall.Epoll_wait(p.epfd, evarray, -1);
+	var msec int64 = -1;
+	if nsec > 0 {
+		msec = (nsec + 1e6 - 1)/1e6;
+	}
+	n, e := syscall.Epoll_wait(p.epfd, evarray, msec);
 	for e == syscall.EAGAIN || e == syscall.EINTR {
-		n, e = syscall.Epoll_wait(p.epfd, evarray, -1)
+		n, e = syscall.Epoll_wait(p.epfd, evarray, msec);
 	}
 	if e != 0 {
-		return -1, 0, os.ErrnoToError(e)
+		return -1, 0, os.ErrnoToError(e);
+	}
+	if n == 0 {
+		return -1, 0, nil;
 	}
 	fd = int64(ev.Fd);
 
 	if ev.Events & writeFlags != 0 {
 		p.StopWaiting(fd, writeFlags);
-		return fd, 'w', nil
+		return fd, 'w', nil;
 	}
 	if ev.Events & readFlags != 0 {
 		p.StopWaiting(fd, readFlags);
-		return fd, 'r', nil
+		return fd, 'r', nil;
 	}
 
 	// Other events are error conditions - wake whoever is waiting.
 	events, already := p.events[fd];
 	if events & writeFlags != 0 {
 		p.StopWaiting(fd, writeFlags);
-		return fd, 'w', nil
+		return fd, 'w', nil;
 	}
 	p.StopWaiting(fd, readFlags);
-	return fd, 'r', nil
+	return fd, 'r', nil;
 }
 
 func (p *pollster) Close() *os.Error {
 	r, e := syscall.Close(p.epfd);
-	return os.ErrnoToError(e)
+	return os.ErrnoToError(e);
 }

src/lib/net/net.go

@@ -255,11 +255,13 @@ func (c *connBase) SetWriteBuffer(bytes int) *os.Error {
 }
 
 func (c *connBase) SetReadTimeout(nsec int64) *os.Error {
-	return setsockopt_tv(c.sysFD(), syscall.SOL_SOCKET, syscall.SO_RCVTIMEO, nsec);
+	c.fd.rdeadline_delta = nsec;
+	return nil;
 }
 
 func (c *connBase) SetWriteTimeout(nsec int64) *os.Error {
-	return setsockopt_tv(c.sysFD(), syscall.SOL_SOCKET, syscall.SO_SNDTIMEO, nsec);
+	c.fd.wdeadline_delta = nsec;
+	return nil;
 }
 
 func (c *connBase) SetTimeout(nsec int64) *os.Error {
@@ -432,29 +434,82 @@ func DialUDP(net, laddr, raddr string) (c *ConnUDP, err *os.Error) {
 
 // TODO: raw IP connections
 
-
 // TODO: raw ethernet connections
 
 // A Conn is a generic network connection.
 type Conn interface {
+	// Read blocks until data is ready from the connection
+	// and then reads into b.  It returns the number
+	// of bytes read, or 0 if the connection has been closed.
 	Read(b []byte) (n int, err *os.Error);
+
+	// Write writes the data in b to the connection.
 	Write(b []byte) (n int, err *os.Error);
+
+	// Close closes the connection.
 	Close() *os.Error;
 
-	// For UDP sockets.
+	// For packet-based protocols such as UDP,
+	// ReadFrom reads the next packet from the network,
+	// returning the number of bytes read and the remote
+	// address that sent them.
 	ReadFrom(b []byte) (n int, addr string, err *os.Error);
+
+	// For packet-based protocols such as UDP,
+	// WriteTo writes the byte buffer b to the network
+	// as a single payload, sending it to the target address.
 	WriteTo(addr string, b []byte) (n int, err *os.Error);
 
-	// Methods that have meaning only on some networks.
+	// SetReadBuffer sets the size of the operating system's
+	// receive buffer associated with the connection.
 	SetReadBuffer(bytes int) *os.Error;
+
+	// SetReadBuffer sets the size of the operating system's
+	// transmit buffer associated with the connection.
 	SetWriteBuffer(bytes int) *os.Error;
+
+	// SetTimeout sets the read and write deadlines associated
+	// with the connection.
 	SetTimeout(nsec int64) *os.Error;
+
+	// SetReadTimeout sets the time (in nanoseconds) that
+	// Read will wait for data before returning os.EAGAIN.
+	// Setting nsec == 0 (the default) disables the deadline.
 	SetReadTimeout(nsec int64) *os.Error;
+
+	// SetWriteTimeout sets the time (in nanoseconds) that
+	// Write will wait to send its data before returning os.EAGAIN.
+	// Setting nsec == 0 (the default) disables the deadline.
+	// Even if write times out, it may return n > 0, indicating that
+	// some of the data was successfully written.
 	SetWriteTimeout(nsec int64) *os.Error;
+
+	// SetLinger sets the behavior of Close() on a connection
+	// which still has data waiting to be sent or to be acknowledged.
+	//
+	// If sec < 0 (the default), Close returns immediately and
+	// the operating system finishes sending the data in the background.
+	//
+	// If sec == 0, Close returns immediately and the operating system
+	// discards any unsent or unacknowledged data.
+	//
+	// If sec > 0, Close blocks for at most sec seconds waiting for
+	// data to be sent and acknowledged.
 	SetLinger(sec int) *os.Error;
+
+	// SetReuseAddr sets whether it is okay to reuse addresses
+	// from recent connections that were not properly closed.
 	SetReuseAddr(reuseaddr bool) *os.Error;
+
+	// SetDontRoute sets whether outgoing messages should
+	// bypass the system routing tables.
 	SetDontRoute(dontroute bool) *os.Error;
+
+	// SetKeepAlive sets whether the operating system should send
+	// keepalive messages on the connection.
 	SetKeepAlive(keepalive bool) *os.Error;
+
+	// BindToDevice binds a connection to a particular network device.
 	BindToDevice(dev string) *os.Error;
 }
 

src/lib/net/parse_test.go

@@ -20,7 +20,6 @@ func TestReadLine(t *testing.T) {
 	}
 	br := bufio.NewBufRead(fd);
 
-	// TODO(rsc): 6g rejects "file :="
 	var file *file;
 	file, err = open(filename);
 	if file == nil {

src/lib/net/timeout_test.go

@@ -0,0 +1,42 @@
+// Copyright 2009 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 (
+	"net";
+	"testing";
+	"time";
+	"os";
+)
+
+func testTimeout(t *testing.T, network, addr string) {
+	fd, err := net.Dial(network, "", addr);
+	defer fd.Close();
+	if err != nil {
+		t.Errorf("dial %s %s failed: %v", network, addr, err);
+	}
+	t0 := time.Nanoseconds();
+	fd.SetReadTimeout(1e8);	// 100ms
+	var b [100]byte;
+	n, err1 := fd.Read(b);
+	t1 := time.Nanoseconds();
+	if n != 0 || err1 != os.EAGAIN {
+		t.Errorf("fd.Read on %s %s did not return 0, EAGAIN: %v, %v", network, addr, n, err1);
+	}
+	if t1 - t0 < 0.5e8 || t1 - t0 > 1.5e8 {
+		t.Errorf("fd.Read on %s %s took %f seconds, expected 0.1", network, addr, float64(t1 - t0) / 1e9);
+	}
+}
+
+func TestTmeoutUDP(t *testing.T) {
+	testTimeout(t, "udp", "127.0.0.1:53");
+}
+
+func TestTimeoutTCP(t *testing.T) {
+	// 74.125.19.99 is www.google.com.
+	// could use dns, but dns depends on
+	// timeouts and this is the timeout test.
+	testTimeout(t, "tcp", "74.125.19.99:80");
+}

src/lib/syscall/socket_darwin.go

@@ -68,7 +68,7 @@ func Setsockopt_tv(fd, level, opt, nsec int64) int64 {
 
 func Setsockopt_linger(fd, level, opt int64, sec int) int64 {
 	var l Linger;
-	if sec != 0 {
+	if sec >= 0 {
 		l.Yes = 1;
 		l.Sec = int32(sec);
 	} else {

src/lib/syscall/socket_linux.go

@@ -80,7 +80,7 @@ func Setsockopt_tv(fd, level, opt, nsec int64) int64 {
 
 func Setsockopt_linger(fd, level, opt int64, sec int) int64 {
 	var l Linger;
-	if sec != 0 {
+	if sec >= 0 {
 		l.Yes = 1;
 		l.Sec = int32(sec)
 	} else {