155 lines
3.6 KiB
Go
155 lines
3.6 KiB
Go
package tcp
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import (
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"errors"
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"fmt"
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"io"
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"log"
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"net"
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"os"
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"sync"
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"time"
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)
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const (
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// DefaultTimeout is the default length of time to wait for first byte.
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DefaultTimeout = 30 * time.Second
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)
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// Mux multiplexes a network connection.
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type Mux struct {
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ln net.Listener
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m map[byte]*listener
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wg sync.WaitGroup
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// The amount of time to wait for the first header byte.
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Timeout time.Duration
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// Out-of-band error logger
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Logger *log.Logger
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}
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// NewMux returns a new instance of Mux for ln.
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func NewMux() *Mux {
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return &Mux{
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m: make(map[byte]*listener),
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Timeout: DefaultTimeout,
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Logger: log.New(os.Stderr, "[tcp] ", log.LstdFlags),
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}
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}
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// Serve handles connections from ln and multiplexes then across registered listener.
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func (mux *Mux) Serve(ln net.Listener) error {
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for {
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// Wait for the next connection.
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// If it returns a temporary error then simply retry.
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// If it returns any other error then exit immediately.
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conn, err := ln.Accept()
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if err, ok := err.(interface {
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Temporary() bool
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}); ok && err.Temporary() {
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continue
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}
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if err != nil {
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// Wait for all connections to be demux
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mux.wg.Wait()
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for _, ln := range mux.m {
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close(ln.c)
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}
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return err
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}
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// Demux in a goroutine to
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mux.wg.Add(1)
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go mux.handleConn(conn)
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}
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}
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func (mux *Mux) handleConn(conn net.Conn) {
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defer mux.wg.Done()
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// Set a read deadline so connections with no data don't timeout.
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if err := conn.SetReadDeadline(time.Now().Add(mux.Timeout)); err != nil {
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conn.Close()
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mux.Logger.Printf("tcp.Mux: cannot set read deadline: %s", err)
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return
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}
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// Read first byte from connection to determine handler.
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var typ [1]byte
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if _, err := io.ReadFull(conn, typ[:]); err != nil {
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conn.Close()
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mux.Logger.Printf("tcp.Mux: cannot read header byte: %s", err)
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return
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}
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// Reset read deadline and let the listener handle that.
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if err := conn.SetReadDeadline(time.Time{}); err != nil {
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conn.Close()
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mux.Logger.Printf("tcp.Mux: cannot reset set read deadline: %s", err)
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return
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}
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// Retrieve handler based on first byte.
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handler := mux.m[typ[0]]
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if handler == nil {
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conn.Close()
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mux.Logger.Printf("tcp.Mux: handler not registered: %d", typ[0])
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return
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}
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// Send connection to handler. The handler is responsible for closing the connection.
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handler.c <- conn
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}
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// Listen returns a listener identified by header.
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// Any connection accepted by mux is multiplexed based on the initial header byte.
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func (mux *Mux) Listen(header byte) net.Listener {
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// Ensure two listeners are not created for the same header byte.
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if _, ok := mux.m[header]; ok {
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panic(fmt.Sprintf("listener already registered under header byte: %d", header))
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}
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// Create a new listener and assign it.
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ln := &listener{
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c: make(chan net.Conn),
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}
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mux.m[header] = ln
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return ln
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}
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// listener is a receiver for connections received by Mux.
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type listener struct {
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c chan net.Conn
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}
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// Accept waits for and returns the next connection to the listener.
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func (ln *listener) Accept() (c net.Conn, err error) {
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conn, ok := <-ln.c
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if !ok {
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return nil, errors.New("network connection closed")
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}
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return conn, nil
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}
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// Close is a no-op. The mux's listener should be closed instead.
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func (ln *listener) Close() error { return nil }
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// Addr always returns nil.
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func (ln *listener) Addr() net.Addr { return nil }
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// Dial connects to a remote mux listener with a given header byte.
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func Dial(network, address string, header byte) (net.Conn, error) {
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conn, err := net.Dial(network, address)
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if err != nil {
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return nil, err
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}
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if _, err := conn.Write([]byte{header}); err != nil {
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return nil, fmt.Errorf("write mux header: %s", err)
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}
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return conn, nil
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}
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