net: rearrange the call order of runtime-integrated network pollster and syscall functions

This CL rearranges the call order for raw networking primitives like
the following;

- For dialers that open active connections, pollDesc.Init will be
  called before syscall.Connect.

- For stream listeners that open passive stream connections,
  pollDesc.Init will be called just after syscall.Listen.

- For datagram listeners that open datagram connections,
  pollDesc.Init will be called just after syscall.Bind.

This is in preparation for runtime-integrated network pollster for BSD
variants.

Update #5199

R=golang-dev, alex.brainman
CC=golang-dev
https://golang.org/cl/12730043

src/pkg/net/sock_posix.go

@@ -53,10 +53,6 @@ func socket(net string, f, t, p int, ipv6only bool, laddr, raddr sockaddr, deadl
 		closesocket(s)
 		return nil, err
 	}
-	if err := fd.init(); err != nil {
-		fd.Close()
-		return nil, err
-	}
 
 	// This function makes a network file descriptor for stream
 	// and datagram dialers, stream and datagram listeners.
@@ -75,7 +71,7 @@ func socket(net string, f, t, p int, ipv6only bool, laddr, raddr sockaddr, deadl
 	if laddr != nil && raddr == nil {
 		switch t {
 		case syscall.SOCK_STREAM, syscall.SOCK_SEQPACKET:
-			if err := fd.listenStream(laddr, toAddr); err != nil {
+			if err := fd.listenStream(laddr, listenerBacklog, toAddr); err != nil {
 				fd.Close()
 				return nil, err
 			}
@@ -107,6 +103,9 @@ func (fd *netFD) dial(laddr, raddr sockaddr, deadline time.Time, toAddr func(sys
 			}
 		}
 	}
+	if err := fd.init(); err != nil {
+		return err
+	}
 	var rsa syscall.Sockaddr
 	if raddr != nil {
 		if rsa, err = raddr.sockaddr(fd.family); err != nil {
@@ -133,7 +132,7 @@ func (fd *netFD) dial(laddr, raddr sockaddr, deadline time.Time, toAddr func(sys
 	return nil
 }
 
-func (fd *netFD) listenStream(laddr sockaddr, toAddr func(syscall.Sockaddr) Addr) error {
+func (fd *netFD) listenStream(laddr sockaddr, backlog int, toAddr func(syscall.Sockaddr) Addr) error {
 	if err := setDefaultListenerSockopts(fd.sysfd); err != nil {
 		return err
 	}
@@ -144,6 +143,12 @@ func (fd *netFD) listenStream(laddr sockaddr, toAddr func(syscall.Sockaddr) Addr
 			return os.NewSyscallError("bind", err)
 		}
 	}
+	if err := syscall.Listen(fd.sysfd, backlog); err != nil {
+		return os.NewSyscallError("listen", err)
+	}
+	if err := fd.init(); err != nil {
+		return err
+	}
 	lsa, _ := syscall.Getsockname(fd.sysfd)
 	fd.setAddr(toAddr(lsa), nil)
 	return nil
@@ -180,6 +185,9 @@ func (fd *netFD) listenDatagram(laddr sockaddr, toAddr func(syscall.Sockaddr) Ad
 			return os.NewSyscallError("bind", err)
 		}
 	}
+	if err := fd.init(); err != nil {
+		return err
+	}
 	lsa, _ := syscall.Getsockname(fd.sysfd)
 	fd.setAddr(toAddr(lsa), nil)
 	return nil

src/pkg/net/tcpsock_posix.go

@@ -301,10 +301,5 @@ func ListenTCP(net string, laddr *TCPAddr) (*TCPListener, error) {
 	if err != nil {
 		return nil, err
 	}
-	err = syscall.Listen(fd.sysfd, listenerBacklog)
-	if err != nil {
-		fd.Close()
-		return nil, &OpError{"listen", net, laddr, err}
-	}
 	return &TCPListener{fd}, nil
 }

src/pkg/net/unixsock_posix.go

@@ -283,11 +283,6 @@ func ListenUnix(net string, laddr *UnixAddr) (*UnixListener, error) {
 	if err != nil {
 		return nil, err
 	}
-	err = syscall.Listen(fd.sysfd, listenerBacklog)
-	if err != nil {
-		fd.Close()
-		return nil, &OpError{Op: "listen", Net: net, Addr: laddr, Err: err}
-	}
 	return &UnixListener{fd, laddr.Name}, nil
 }