caddyhttp: Add support for listener wrapper modules

Wrapping listeners is useful for composing custom behavior related
to accepting, closing, reading/writing connections (etc) below the
application layer; for example, the PROXY protocol.

1 files changed, 13 insertions, 0 deletions

diff --git a/listeners.go b/listeners.go
index ae1873f..0bbee8a 100644
--- a/listeners.go
+++ b/listeners.go
@@ -386,6 +386,19 @@ func JoinNetworkAddress(network, host, port string) string {
 	return a
 }
 
+// ListenerWrapper is a type that wraps a listener
+// so it can modify the input listener's methods.
+// Modules that implement this interface are found
+// in the caddy.listeners namespace. Usually, to
+// wrap a listener, you will define your own struct
+// type that embeds the input listener, then
+// implement your own methods that you want to wrap,
+// calling the underlying listener's methods where
+// appropriate.
+type ListenerWrapper interface {
+	WrapListener(net.Listener) net.Listener
+}
+
 var (
 	listeners   = make(map[string]*globalListener)
 	listenersMu sync.Mutex