distribution/registry/listener/listener.go

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package listener
import (
"fmt"
"net"
"os"
"time"
"github.com/coreos/go-systemd/v22/activation"
log "github.com/sirupsen/logrus"
)
// tcpKeepAliveListener sets TCP keep-alive timeouts on accepted
// connections. It's used by ListenAndServe and ListenAndServeTLS so
// dead TCP connections (e.g. closing laptop mid-download) eventually
// go away.
// it is a plain copy-paste from net/http/server.go
type tcpKeepAliveListener struct {
*net.TCPListener
}
func (ln tcpKeepAliveListener) Accept() (c net.Conn, err error) {
tc, err := ln.AcceptTCP()
if err != nil {
return
}
tc.SetKeepAlive(true)
tc.SetKeepAlivePeriod(3 * time.Minute)
return tc, nil
}
// NewListener announces on laddr and net. Accepted values of the net are
// 'unix' and 'tcp'
func NewListener(net, laddr string) (net.Listener, error) {
listeners, err := activation.Listeners()
if err != nil {
return nil, fmt.Errorf("Socket activation failed: %v", err)
}
switch len(listeners) {
case 0:
// No socket-activation found
switch net {
case "unix":
return newUnixListener(laddr)
case "tcp", "": // an empty net means tcp
return newTCPListener(laddr)
default:
return nil, fmt.Errorf("unknown address type %s", net)
}
case 1:
log.Info("Socet-activation is being used. Overriding requested address")
return listeners[0], nil
default:
return nil, fmt.Errorf("Found %d socket-activation listeners, only expected 1", len(listeners))
}
}
func newUnixListener(laddr string) (net.Listener, error) {
fi, err := os.Stat(laddr)
if err == nil {
// the file exists.
// try to remove it if it's a socket
if !isSocket(fi.Mode()) {
return nil, fmt.Errorf("file %s exists and is not a socket", laddr)
}
if err := os.Remove(laddr); err != nil {
return nil, err
}
} else if !os.IsNotExist(err) {
// we can't do stat on the file.
// it means we can not remove it
return nil, err
}
return net.Listen("unix", laddr)
}
func isSocket(m os.FileMode) bool {
return m&os.ModeSocket != 0
}
func newTCPListener(laddr string) (net.Listener, error) {
ln, err := net.Listen("tcp", laddr)
if err != nil {
return nil, err
}
return tcpKeepAliveListener{ln.(*net.TCPListener)}, nil
}