1 files changed, 425 insertions, 0 deletions
diff --git a/src/net/net.go b/src/net/net.go
new file mode 100644
index 000000000..cb31af5e3
--- /dev/null
+++ b/src/net/net.go
@@ -0,0 +1,425 @@
+// 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 provides a portable interface for network I/O, including
+TCP/IP, UDP, domain name resolution, and Unix domain sockets.
+
+Although the package provides access to low-level networking
+primitives, most clients will need only the basic interface provided
+by the Dial, Listen, and Accept functions and the associated
+Conn and Listener interfaces. The crypto/tls package uses
+the same interfaces and similar Dial and Listen functions.
+
+The Dial function connects to a server:
+
+	conn, err := net.Dial("tcp", "google.com:80")
+	if err != nil {
+		// handle error
+	}
+	fmt.Fprintf(conn, "GET / HTTP/1.0\r\n\r\n")
+	status, err := bufio.NewReader(conn).ReadString('\n')
+	// ...
+
+The Listen function creates servers:
+
+	ln, err := net.Listen("tcp", ":8080")
+	if err != nil {
+		// handle error
+	}
+	for {
+		conn, err := ln.Accept()
+		if err != nil {
+			// handle error
+		}
+		go handleConnection(conn)
+	}
+*/
+package net
+
+// TODO(rsc):
+//	support for raw ethernet sockets
+
+import (
+	"errors"
+	"io"
+	"os"
+	"syscall"
+	"time"
+)
+
+// Addr represents a network end point address.
+type Addr interface {
+	Network() string // name of the network
+	String() string  // string form of address
+}
+
+// Conn is a generic stream-oriented network connection.
+//
+// Multiple goroutines may invoke methods on a Conn simultaneously.
+type Conn interface {
+	// Read reads data from the connection.
+	// Read can be made to time out and return a Error with Timeout() == true
+	// after a fixed time limit; see SetDeadline and SetReadDeadline.
+	Read(b []byte) (n int, err error)
+
+	// Write writes data to the connection.
+	// Write can be made to time out and return a Error with Timeout() == true
+	// after a fixed time limit; see SetDeadline and SetWriteDeadline.
+	Write(b []byte) (n int, err error)
+
+	// Close closes the connection.
+	// Any blocked Read or Write operations will be unblocked and return errors.
+	Close() error
+
+	// LocalAddr returns the local network address.
+	LocalAddr() Addr
+
+	// RemoteAddr returns the remote network address.
+	RemoteAddr() Addr
+
+	// SetDeadline sets the read and write deadlines associated
+	// with the connection. It is equivalent to calling both
+	// SetReadDeadline and SetWriteDeadline.
+	//
+	// A deadline is an absolute time after which I/O operations
+	// fail with a timeout (see type Error) instead of
+	// blocking. The deadline applies to all future I/O, not just
+	// the immediately following call to Read or Write.
+	//
+	// An idle timeout can be implemented by repeatedly extending
+	// the deadline after successful Read or Write calls.
+	//
+	// A zero value for t means I/O operations will not time out.
+	SetDeadline(t time.Time) error
+
+	// SetReadDeadline sets the deadline for future Read calls.
+	// A zero value for t means Read will not time out.
+	SetReadDeadline(t time.Time) error
+
+	// SetWriteDeadline sets the deadline for future Write calls.
+	// Even if write times out, it may return n > 0, indicating that
+	// some of the data was successfully written.
+	// A zero value for t means Write will not time out.
+	SetWriteDeadline(t time.Time) error
+}
+
+type conn struct {
+	fd *netFD
+}
+
+func (c *conn) ok() bool { return c != nil && c.fd != nil }
+
+// Implementation of the Conn interface.
+
+// Read implements the Conn Read method.
+func (c *conn) Read(b []byte) (int, error) {
+	if !c.ok() {
+		return 0, syscall.EINVAL
+	}
+	return c.fd.Read(b)
+}
+
+// Write implements the Conn Write method.
+func (c *conn) Write(b []byte) (int, error) {
+	if !c.ok() {
+		return 0, syscall.EINVAL
+	}
+	return c.fd.Write(b)
+}
+
+// Close closes the connection.
+func (c *conn) Close() error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	return c.fd.Close()
+}
+
+// LocalAddr returns the local network address.
+func (c *conn) LocalAddr() Addr {
+	if !c.ok() {
+		return nil
+	}
+	return c.fd.laddr
+}
+
+// RemoteAddr returns the remote network address.
+func (c *conn) RemoteAddr() Addr {
+	if !c.ok() {
+		return nil
+	}
+	return c.fd.raddr
+}
+
+// SetDeadline implements the Conn SetDeadline method.
+func (c *conn) SetDeadline(t time.Time) error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	return c.fd.setDeadline(t)
+}
+
+// SetReadDeadline implements the Conn SetReadDeadline method.
+func (c *conn) SetReadDeadline(t time.Time) error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	return c.fd.setReadDeadline(t)
+}
+
+// SetWriteDeadline implements the Conn SetWriteDeadline method.
+func (c *conn) SetWriteDeadline(t time.Time) error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	return c.fd.setWriteDeadline(t)
+}
+
+// SetReadBuffer sets the size of the operating system's
+// receive buffer associated with the connection.
+func (c *conn) SetReadBuffer(bytes int) error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	return setReadBuffer(c.fd, bytes)
+}
+
+// SetWriteBuffer sets the size of the operating system's
+// transmit buffer associated with the connection.
+func (c *conn) SetWriteBuffer(bytes int) error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	return setWriteBuffer(c.fd, bytes)
+}
+
+// File sets the underlying os.File to blocking mode and returns a copy.
+// It is the caller's responsibility to close f when finished.
+// Closing c does not affect f, and closing f does not affect c.
+//
+// The returned os.File's file descriptor is different from the connection's.
+// Attempting to change properties of the original using this duplicate
+// may or may not have the desired effect.
+func (c *conn) File() (f *os.File, err error) { return c.fd.dup() }
+
+// An Error represents a network error.
+type Error interface {
+	error
+	Timeout() bool   // Is the error a timeout?
+	Temporary() bool // Is the error temporary?
+}
+
+// PacketConn is a generic packet-oriented network connection.
+//
+// Multiple goroutines may invoke methods on a PacketConn simultaneously.
+type PacketConn interface {
+	// ReadFrom reads a packet from the connection,
+	// copying the payload into b.  It returns the number of
+	// bytes copied into b and the return address that
+	// was on the packet.
+	// ReadFrom can be made to time out and return
+	// an error with Timeout() == true after a fixed time limit;
+	// see SetDeadline and SetReadDeadline.
+	ReadFrom(b []byte) (n int, addr Addr, err error)
+
+	// WriteTo writes a packet with payload b to addr.
+	// WriteTo can be made to time out and return
+	// an error with Timeout() == true after a fixed time limit;
+	// see SetDeadline and SetWriteDeadline.
+	// On packet-oriented connections, write timeouts are rare.
+	WriteTo(b []byte, addr Addr) (n int, err error)
+
+	// Close closes the connection.
+	// Any blocked ReadFrom or WriteTo operations will be unblocked and return errors.
+	Close() error
+
+	// LocalAddr returns the local network address.
+	LocalAddr() Addr
+
+	// SetDeadline sets the read and write deadlines associated
+	// with the connection.
+	SetDeadline(t time.Time) error
+
+	// SetReadDeadline sets the deadline for future Read calls.
+	// If the deadline is reached, Read will fail with a timeout
+	// (see type Error) instead of blocking.
+	// A zero value for t means Read will not time out.
+	SetReadDeadline(t time.Time) error
+
+	// SetWriteDeadline sets the deadline for future Write calls.
+	// If the deadline is reached, Write will fail with a timeout
+	// (see type Error) instead of blocking.
+	// A zero value for t means Write will not time out.
+	// Even if write times out, it may return n > 0, indicating that
+	// some of the data was successfully written.
+	SetWriteDeadline(t time.Time) error
+}
+
+var listenerBacklog = maxListenerBacklog()
+
+// A Listener is a generic network listener for stream-oriented protocols.
+//
+// Multiple goroutines may invoke methods on a Listener simultaneously.
+type Listener interface {
+	// Accept waits for and returns the next connection to the listener.
+	Accept() (c Conn, err error)
+
+	// Close closes the listener.
+	// Any blocked Accept operations will be unblocked and return errors.
+	Close() error
+
+	// Addr returns the listener's network address.
+	Addr() Addr
+}
+
+// Various errors contained in OpError.
+var (
+	// For connection setup and write operations.
+	errMissingAddress = errors.New("missing address")
+
+	// For both read and write operations.
+	errTimeout          error = &timeoutError{}
+	errClosing                = errors.New("use of closed network connection")
+	ErrWriteToConnected       = errors.New("use of WriteTo with pre-connected connection")
+)
+
+// OpError is the error type usually returned by functions in the net
+// package. It describes the operation, network type, and address of
+// an error.
+type OpError struct {
+	// Op is the operation which caused the error, such as
+	// "read" or "write".
+	Op string
+
+	// Net is the network type on which this error occurred,
+	// such as "tcp" or "udp6".
+	Net string
+
+	// Addr is the network address on which this error occurred.
+	Addr Addr
+
+	// Err is the error that occurred during the operation.
+	Err error
+}
+
+func (e *OpError) Error() string {
+	if e == nil {
+		return "<nil>"
+	}
+	s := e.Op
+	if e.Net != "" {
+		s += " " + e.Net
+	}
+	if e.Addr != nil {
+		s += " " + e.Addr.String()
+	}
+	s += ": " + e.Err.Error()
+	return s
+}
+
+type temporary interface {
+	Temporary() bool
+}
+
+func (e *OpError) Temporary() bool {
+	t, ok := e.Err.(temporary)
+	return ok && t.Temporary()
+}
+
+var noDeadline = time.Time{}
+
+type timeout interface {
+	Timeout() bool
+}
+
+func (e *OpError) Timeout() bool {
+	t, ok := e.Err.(timeout)
+	return ok && t.Timeout()
+}
+
+type timeoutError struct{}
+
+func (e *timeoutError) Error() string   { return "i/o timeout" }
+func (e *timeoutError) Timeout() bool   { return true }
+func (e *timeoutError) Temporary() bool { return true }
+
+type AddrError struct {
+	Err  string
+	Addr string
+}
+
+func (e *AddrError) Error() string {
+	if e == nil {
+		return "<nil>"
+	}
+	s := e.Err
+	if e.Addr != "" {
+		s += " " + e.Addr
+	}
+	return s
+}
+
+func (e *AddrError) Temporary() bool {
+	return false
+}
+
+func (e *AddrError) Timeout() bool {
+	return false
+}
+
+type UnknownNetworkError string
+
+func (e UnknownNetworkError) Error() string   { return "unknown network " + string(e) }
+func (e UnknownNetworkError) Temporary() bool { return false }
+func (e UnknownNetworkError) Timeout() bool   { return false }
+
+type InvalidAddrError string
+
+func (e InvalidAddrError) Error() string   { return string(e) }
+func (e InvalidAddrError) Timeout() bool   { return false }
+func (e InvalidAddrError) Temporary() bool { return false }
+
+// DNSConfigError represents an error reading the machine's DNS configuration.
+type DNSConfigError struct {
+	Err error
+}
+
+func (e *DNSConfigError) Error() string {
+	return "error reading DNS config: " + e.Err.Error()
+}
+
+func (e *DNSConfigError) Timeout() bool   { return false }
+func (e *DNSConfigError) Temporary() bool { return false }
+
+type writerOnly struct {
+	io.Writer
+}
+
+// Fallback implementation of io.ReaderFrom's ReadFrom, when sendfile isn't
+// applicable.
+func genericReadFrom(w io.Writer, r io.Reader) (n int64, err error) {
+	// Use wrapper to hide existing r.ReadFrom from io.Copy.
+	return io.Copy(writerOnly{w}, r)
+}
+
+// Limit the number of concurrent cgo-using goroutines, because
+// each will block an entire operating system thread. The usual culprit
+// is resolving many DNS names in separate goroutines but the DNS
+// server is not responding. Then the many lookups each use a different
+// thread, and the system or the program runs out of threads.
+
+var threadLimit = make(chan struct{}, 500)
+
+// Using send for acquire is fine here because we are not using this
+// to protect any memory. All we care about is the number of goroutines
+// making calls at a time.
+
+func acquireThread() {
+	threadLimit <- struct{}{}
+}
+
+func releaseThread() {
+	<-threadLimit
+}