commit
918f37d2f8
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/*
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Package tcp provides various TCP-related utilities. The TCP mux code provided by this package originated with InfluxDB.
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*/
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package tcp
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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 demuxed
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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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package tcp
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import (
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"bytes"
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"io"
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"io/ioutil"
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"log"
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"net"
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"strings"
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"sync"
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"testing"
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"testing/quick"
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"time"
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)
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// Ensure the muxer can split a listener's connections across multiple listeners.
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func TestMux(t *testing.T) {
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if err := quick.Check(func(n uint8, msg []byte) bool {
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if testing.Verbose() {
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if len(msg) == 0 {
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log.Printf("n=%d, <no message>", n)
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} else {
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log.Printf("n=%d, hdr=%d, len=%d", n, msg[0], len(msg))
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}
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}
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var wg sync.WaitGroup
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// Open single listener on random port.
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tcpListener, err := net.Listen("tcp", "127.0.0.1:0")
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if err != nil {
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t.Fatal(err)
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}
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defer tcpListener.Close()
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// Setup muxer & listeners.
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mux := NewMux()
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mux.Timeout = 200 * time.Millisecond
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if !testing.Verbose() {
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mux.Logger = log.New(ioutil.Discard, "", 0)
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}
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for i := uint8(0); i < n; i++ {
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ln := mux.Listen(byte(i))
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wg.Add(1)
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go func(i uint8, ln net.Listener) {
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defer wg.Done()
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// Wait for a connection for this listener.
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conn, err := ln.Accept()
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if conn != nil {
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defer conn.Close()
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}
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// If there is no message or the header byte
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// doesn't match then expect close.
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if len(msg) == 0 || msg[0] != byte(i) {
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if err == nil || err.Error() != "network connection closed" {
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t.Fatalf("unexpected error: %s", err)
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}
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return
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}
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// If the header byte matches this listener
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// then expect a connection and read the message.
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var buf bytes.Buffer
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if _, err := io.CopyN(&buf, conn, int64(len(msg)-1)); err != nil {
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t.Fatal(err)
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} else if !bytes.Equal(msg[1:], buf.Bytes()) {
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t.Fatalf("message mismatch:\n\nexp=%x\n\ngot=%x\n\n", msg[1:], buf.Bytes())
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}
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// Write response.
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if _, err := conn.Write([]byte("OK")); err != nil {
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t.Fatal(err)
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}
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}(i, ln)
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}
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// Begin serving from the listener.
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go mux.Serve(tcpListener)
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// Write message to TCP listener and read OK response.
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conn, err := net.Dial("tcp", tcpListener.Addr().String())
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if err != nil {
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t.Fatal(err)
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} else if _, err = conn.Write(msg); err != nil {
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t.Fatal(err)
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}
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// Read the response into the buffer.
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var resp [2]byte
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_, err = io.ReadFull(conn, resp[:])
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// If the message header is less than n then expect a response.
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// Otherwise we should get an EOF because the mux closed.
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if len(msg) > 0 && uint8(msg[0]) < n {
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if string(resp[:]) != `OK` {
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t.Fatalf("unexpected response: %s", resp[:])
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}
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} else {
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if err == nil || (err != io.EOF && !(strings.Contains(err.Error(), "connection reset by peer") ||
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strings.Contains(err.Error(), "closed by the remote host"))) {
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t.Fatalf("unexpected error: %s", err)
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}
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}
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// Close connection.
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if err := conn.Close(); err != nil {
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t.Fatal(err)
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}
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// Close original TCP listener and wait for all goroutines to close.
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tcpListener.Close()
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wg.Wait()
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return true
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}, nil); err != nil {
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t.Error(err)
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}
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}
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// Ensure two handlers cannot be registered for the same header byte.
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func TestMux_Listen_ErrAlreadyRegistered(t *testing.T) {
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defer func() {
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if r := recover(); r != `listener already registered under header byte: 5` {
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t.Fatalf("unexpected recover: %#v", r)
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}
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}()
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// Register two listeners with the same header byte.
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mux := NewMux()
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mux.Listen(5)
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mux.Listen(5)
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}
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Loading…
Reference in New Issue