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//go:build !linux
package caddy
import (
"fmt"
"net"
"sync"
"sync/atomic"
"time"
"go.uber.org/zap"
)
func ListenTimeout(network, addr string, keepAlivePeriod time.Duration) (net.Listener, error) {
// check to see if plugin provides listener
if ln, err := getListenerFromPlugin(network, addr); err != nil || ln != nil {
return ln, err
}
lnKey := listenerKey(network, addr)
sharedLn, _, err := listenerPool.LoadOrNew(lnKey, func() (Destructor, error) {
ln, err := net.Listen(network, addr)
if err != nil {
// https://github.com/caddyserver/caddy/pull/4534
if isUnixNetwork(network) && isListenBindAddressAlreadyInUseError(err) {
return nil, fmt.Errorf("%w: this can happen if Caddy was forcefully killed", err)
}
return nil, err
}
return &sharedListener{Listener: ln, key: lnKey}, nil
})
if err != nil {
return nil, err
}
return &fakeCloseListener{sharedListener: sharedLn.(*sharedListener), keepAlivePeriod: keepAlivePeriod}, nil
}
// fakeCloseListener is a private wrapper over a listener that
// is shared. The state of fakeCloseListener is not shared.
// This allows one user of a socket to "close" the listener
// while in reality the socket stays open for other users of
// the listener. In this way, servers become hot-swappable
// while the listener remains running. Listeners should be
// re-wrapped in a new fakeCloseListener each time the listener
// is reused. This type is atomic and values must not be copied.
type fakeCloseListener struct {
closed int32 // accessed atomically; belongs to this struct only
*sharedListener // embedded, so we also become a net.Listener
keepAlivePeriod time.Duration
}
type canSetKeepAlive interface {
SetKeepAlivePeriod(d time.Duration) error
SetKeepAlive(bool) error
}
func (fcl *fakeCloseListener) Accept() (net.Conn, error) {
// if the listener is already "closed", return error
if atomic.LoadInt32(&fcl.closed) == 1 {
return nil, fakeClosedErr(fcl)
}
// call underlying accept
conn, err := fcl.sharedListener.Accept()
if err == nil {
// if 0, do nothing, Go's default is already set
// and if the connection allows setting KeepAlive, set it
if tconn, ok := conn.(canSetKeepAlive); ok && fcl.keepAlivePeriod != 0 {
if fcl.keepAlivePeriod > 0 {
err = tconn.SetKeepAlivePeriod(fcl.keepAlivePeriod)
} else { // negative
err = tconn.SetKeepAlive(false)
}
if err != nil {
Log().With(zap.String("server", fcl.sharedListener.key)).Warn("unable to set keepalive for new connection:", zap.Error(err))
}
}
return conn, nil
}
// since Accept() returned an error, it may be because our reference to
// the listener (this fakeCloseListener) may have been closed, i.e. the
// server is shutting down; in that case, we need to clear the deadline
// that we set when Close() was called, and return a non-temporary and
// non-timeout error value to the caller, masking the "true" error, so
// that server loops / goroutines won't retry, linger, and leak
if atomic.LoadInt32(&fcl.closed) == 1 {
// we dereference the sharedListener explicitly even though it's embedded
// so that it's clear in the code that side-effects are shared with other
// users of this listener, not just our own reference to it; we also don't
// do anything with the error because all we could do is log it, but we
// expliclty assign it to nothing so we don't forget it's there if needed
_ = fcl.sharedListener.clearDeadline()
if netErr, ok := err.(net.Error); ok && netErr.Timeout() {
return nil, fakeClosedErr(fcl)
}
}
return nil, err
}
// Close stops accepting new connections without closing the
// underlying listener. The underlying listener is only closed
// if the caller is the last known user of the socket.
func (fcl *fakeCloseListener) Close() error {
if atomic.CompareAndSwapInt32(&fcl.closed, 0, 1) {
// There are two ways I know of to get an Accept()
// function to return to the server loop that called
// it: close the listener, or set a deadline in the
// past. Obviously, we can't close the socket yet
// since others may be using it (hence this whole
// file). But we can set the deadline in the past,
// and this is kind of cheating, but it works, and
// it apparently even works on Windows.
_ = fcl.sharedListener.setDeadline()
_, _ = listenerPool.Delete(fcl.sharedListener.key)
}
return nil
}
// sharedListener is a wrapper over an underlying listener. The listener
// and the other fields on the struct are shared state that is synchronized,
// so sharedListener structs must never be copied (always use a pointer).
type sharedListener struct {
net.Listener
key string // uniquely identifies this listener
deadline bool // whether a deadline is currently set
deadlineMu sync.Mutex
}
func (sl *sharedListener) clearDeadline() error {
var err error
sl.deadlineMu.Lock()
if sl.deadline {
switch ln := sl.Listener.(type) {
case *net.TCPListener:
err = ln.SetDeadline(time.Time{})
case *net.UnixListener:
err = ln.SetDeadline(time.Time{})
}
sl.deadline = false
}
sl.deadlineMu.Unlock()
return err
}
func (sl *sharedListener) setDeadline() error {
timeInPast := time.Now().Add(-1 * time.Minute)
var err error
sl.deadlineMu.Lock()
if !sl.deadline {
switch ln := sl.Listener.(type) {
case *net.TCPListener:
err = ln.SetDeadline(timeInPast)
case *net.UnixListener:
err = ln.SetDeadline(timeInPast)
}
sl.deadline = true
}
sl.deadlineMu.Unlock()
return err
}
// Destruct is called by the UsagePool when the listener is
// finally not being used anymore. It closes the socket.
func (sl *sharedListener) Destruct() error {
return sl.Listener.Close()
}
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