add new files for compat layer

wgstack/conn/controlfns.go

@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: MIT
+//
+// Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
+
+package conn
+
+import (
+	"net"
+	"syscall"
+)
+
+// UDP socket read/write buffer size (7MB). The value of 7MB is chosen as it is
+// the max supported by a default configuration of macOS. Some platforms will
+// silently clamp the value to other maximums, such as linux clamping to
+// net.core.{r,w}mem_max (see _linux.go for additional implementation that works
+// around this limitation)
+const socketBufferSize = 7 << 20
+
+// controlFn is the callback function signature from net.ListenConfig.Control.
+// It is used to apply platform specific configuration to the socket prior to
+// bind.
+type controlFn func(network, address string, c syscall.RawConn) error
+
+// controlFns is a list of functions that are called from the listen config
+// that can apply socket options.
+var controlFns = []controlFn{}
+
+// listenConfig returns a net.ListenConfig that applies the controlFns to the
+// socket prior to bind. This is used to apply socket buffer sizing and packet
+// information OOB configuration for sticky sockets.
+func listenConfig() *net.ListenConfig {
+	return &net.ListenConfig{
+		Control: func(network, address string, c syscall.RawConn) error {
+			for _, fn := range controlFns {
+				if err := fn(network, address, c); err != nil {
+					return err
+				}
+			}
+			return nil
+		},
+	}
+}