device: remove global for roaming escape hatch

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

device/mobilequirks.go

@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2020 WireGuard LLC. All Rights Reserved.
+ */
+
+package device
+
+func (device *Device) DisableSomeRoamingForBrokenMobileSemantics() {
+	device.peers.RLock()
+	for _, peer := range device.peers.keyMap {
+		peer.Lock()
+		defer peer.Unlock()
+		peer.disableRoaming = peer.endpoint != nil
+	}
+	device.peers.RUnlock()
+}

device/peer.go

@@ -28,6 +28,7 @@ type Peer struct {
 	device                      *Device
 	endpoint                    conn.Endpoint
 	persistentKeepaliveInterval uint16
+	disableRoaming              bool
 
 	// These fields are accessed with atomic operations, which must be
 	// 64-bit aligned even on 32-bit platforms. Go guarantees that an
@@ -290,10 +291,9 @@ func (peer *Peer) Stop() {
 	peer.ZeroAndFlushAll()
 }
 
-var RoamingDisabled bool
 
 func (peer *Peer) SetEndpointFromPacket(endpoint conn.Endpoint) {
-	if RoamingDisabled {
+	if peer.disableRoaming {
 		return
 	}
 	peer.Lock()