net: make use of the kernel state to listen on TCP, Unix

R=golang-dev, dave, minux.ma
CC=golang-dev
https://golang.org/cl/5545044

src/pkg/net/Makefile

@@ -36,6 +36,7 @@ GOFILES_darwin=\
 	port.go\
 	sendfile_stub.go\
 	sock.go\
+	sock_bsd.go\
 	sockopt.go\
 	sockopt_bsd.go\
 	sockoptip.go\
@@ -68,6 +69,7 @@ GOFILES_freebsd=\
 	port.go\
 	sendfile_stub.go\
 	sock.go\
+	sock_bsd.go\
 	sockopt.go\
 	sockopt_bsd.go\
 	sockoptip.go\
@@ -99,6 +101,7 @@ GOFILES_linux=\
 	port.go\
 	sendfile_linux.go\
 	sock.go\
+	sock_linux.go\
 	sockopt.go\
 	sockopt_linux.go\
 	sockoptip.go\
@@ -130,6 +133,7 @@ GOFILES_netbsd=\
 	port.go\
 	sendfile_stub.go\
 	sock.go\
+	sock_bsd.go\
 	sockopt.go\
 	sockopt_bsd.go\
 	sockoptip.go\
@@ -155,6 +159,7 @@ GOFILES_openbsd=\
 	port.go\
 	sendfile_stub.go\
 	sock.go\
+	sock_bsd.go\
 	sockopt.go\
 	sockopt_bsd.go\
 	sockoptip.go\
@@ -184,6 +189,7 @@ GOFILES_windows=\
 	lookup_windows.go\
 	sendfile_windows.go\
 	sock.go\
+	sock_windows.go\
 	sockopt.go\
 	sockopt_windows.go\
 	sockoptip.go\

src/pkg/net/ipsock_posix.go

@@ -91,11 +91,6 @@ func favoriteAddrFamily(net string, raddr, laddr sockaddr, mode string) int {
 	return syscall.AF_INET6
 }
 
-// TODO(rsc): if syscall.OS == "linux", we're supposed to read
-// /proc/sys/net/core/somaxconn,
-// to take advantage of kernels that have raised the limit.
-func listenBacklog() int { return syscall.SOMAXCONN }
-
 // Internet sockets (TCP, UDP)
 
 // A sockaddr represents a TCP or UDP network address that can

src/pkg/net/sock.go

@@ -14,6 +14,8 @@ import (
 	"syscall"
 )
 
+var listenerBacklog = maxListenerBacklog()
+
 // Generic socket creation.
 func socket(net string, f, p, t int, la, ra syscall.Sockaddr, toAddr func(syscall.Sockaddr) Addr) (fd *netFD, err error) {
 	// See ../syscall/exec.go for description of ForkLock.

src/pkg/net/sock_bsd.go

+// 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.
+
+// +build darwin freebsd netbsd openbsd
+
+// Sockets for BSD variants
+
+package net
+
+import (
+	"runtime"
+	"syscall"
+)
+
+func maxListenerBacklog() int {
+	var (
+		n   uint32
+		err error
+	)
+	switch runtime.GOOS {
+	case "darwin", "freebsd":
+		n, err = syscall.SysctlUint32("kern.ipc.somaxconn")
+	case "netbsd":
+		// NOTE: NetBSD has no somaxconn-like kernel state so far
+	case "openbsd":
+		n, err = syscall.SysctlUint32("kern.somaxconn")
+	}
+	if n == 0 || err != nil {
+		return syscall.SOMAXCONN
+	}
+	return int(n)
+}

src/pkg/net/sock_linux.go

+// 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.
+
+// Sockets for Linux
+
+package net
+
+import "syscall"
+
+func maxListenerBacklog() int {
+	fd, err := open("/proc/sys/net/core/somaxconn")
+	if err != nil {
+		return syscall.SOMAXCONN
+	}
+	defer fd.close()
+	l, ok := fd.readLine()
+	if !ok {
+		return syscall.SOMAXCONN
+	}
+	f := getFields(l)
+	n, _, ok := dtoi(f[0], 0)
+	if n == 0 || !ok {
+		return syscall.SOMAXCONN
+	}
+	return n
+}

src/pkg/net/sock_windows.go

+// 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.
+
+// Sockets for Windows
+
+package net
+
+import "syscall"
+
+func maxListenerBacklog() int {
+	// TODO: Implement this
+	return syscall.SOMAXCONN
+}

src/pkg/net/tcpsock_posix.go

@@ -249,10 +249,10 @@ func ListenTCP(net string, laddr *TCPAddr) (l *TCPListener, err error) {
 	if err != nil {
 		return nil, err
 	}
-	errno := syscall.Listen(fd.sysfd, listenBacklog())
-	if errno != nil {
+	err = syscall.Listen(fd.sysfd, listenerBacklog)
+	if err != nil {
 		closesocket(fd.sysfd)
-		return nil, &OpError{"listen", "tcp", laddr, errno}
+		return nil, &OpError{"listen", "tcp", laddr, err}
 	}
 	l = new(TCPListener)
 	l.fd = fd

src/pkg/net/unixsock_posix.go

@@ -315,7 +315,7 @@ type UnixListener struct {
 
 // ListenUnix announces on the Unix domain socket laddr and returns a Unix listener.
 // Net must be "unix" (stream sockets).
-func ListenUnix(net string, laddr *UnixAddr) (l *UnixListener, err error) {
+func ListenUnix(net string, laddr *UnixAddr) (*UnixListener, error) {
 	if net != "unix" && net != "unixgram" && net != "unixpacket" {
 		return nil, UnknownNetworkError(net)
 	}
@@ -326,10 +326,10 @@ func ListenUnix(net string, laddr *UnixAddr) (l *UnixListener, err error) {
 	if err != nil {
 		return nil, err
 	}
-	e1 := syscall.Listen(fd.sysfd, 8) // listenBacklog());
-	if e1 != nil {
+	err = syscall.Listen(fd.sysfd, listenerBacklog)
+	if err != nil {
 		closesocket(fd.sysfd)
-		return nil, &OpError{Op: "listen", Net: "unix", Addr: laddr, Err: e1}
+		return nil, &OpError{Op: "listen", Net: "unix", Addr: laddr, Err: err}
 	}
 	return &UnixListener{fd, laddr.Name}, nil
 }