From 034a1a12f7849276823546f369b00507dc8029ce Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Wed, 12 Dec 2018 00:45:50 +0100
Subject: [PATCH] Supply missing pieces of path change

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 .../PacketTunnelProvider.swift                 | 18 ++++++++++--------
 .../PacketTunnelSettingsGenerator.swift        |  4 ++--
 wireguard-go-bridge/src/api-ios.go             | 15 +++++++++++++--
 wireguard-go-bridge/wireguard.h                |  3 ++-
 4 files changed, 27 insertions(+), 13 deletions(-)

diff --git a/WireGuard/WireGuardNetworkExtension/PacketTunnelProvider.swift b/WireGuard/WireGuardNetworkExtension/PacketTunnelProvider.swift
index 04e9637..f5f0296 100644
--- a/WireGuard/WireGuardNetworkExtension/PacketTunnelProvider.swift
+++ b/WireGuard/WireGuardNetworkExtension/PacketTunnelProvider.swift
@@ -95,16 +95,18 @@ class PacketTunnelProvider: NEPacketTunnelProvider {
         networkMonitor = NWPathMonitor()
         networkMonitor?.pathUpdateHandler = { path in
             guard handle >= 0 else { return }
-            
             if path.status == .satisfied {
-                let endpointString = packetTunnelSettingsGenerator.endpointUapiConfiguration()
-                
-                let endpointGoString = endpointString.withCString {
-                    gostring_t(p: $0, n: endpointString.utf8.count)
+                wg_log(.debug, message: "Network change detected, re-establishing sockets and IPs: \(path.availableInterfaces)")
+                let endpointString = packetTunnelSettingsGenerator.endpointUapiConfiguration(currentListenPort: wgGetListenPort(handle))
+                let err = endpointString.withCString {
+                    wgSetConfig(handle,  gostring_t(p: $0, n: endpointString.utf8.count))
+                }
+                if err == -EADDRINUSE {
+                    let endpointString = packetTunnelSettingsGenerator.endpointUapiConfiguration(currentListenPort: 0)
+                    _ = endpointString.withCString {
+                        wgSetConfig(handle,  gostring_t(p: $0, n: endpointString.utf8.count))
+                    }
                 }
-                
-                wg_log(.debug, staticMessage: "Network change detected, calling wgSetConfig")
-                wgSetConfig(handle, endpointGoString)
             }
         }
         networkMonitor?.start(queue: DispatchQueue(label: "NetworkMonitor"))
diff --git a/WireGuard/WireGuardNetworkExtension/PacketTunnelSettingsGenerator.swift b/WireGuard/WireGuardNetworkExtension/PacketTunnelSettingsGenerator.swift
index 0eea95a..61e161e 100644
--- a/WireGuard/WireGuardNetworkExtension/PacketTunnelSettingsGenerator.swift
+++ b/WireGuard/WireGuardNetworkExtension/PacketTunnelSettingsGenerator.swift
@@ -15,8 +15,8 @@ class PacketTunnelSettingsGenerator {
         self.resolvedEndpoints = resolvedEndpoints
     }
 
-    func endpointUapiConfiguration() -> String {
-        var wgSettings = "listen_port=\(tunnelConfiguration.interface.listenPort ?? 0)\n"
+    func endpointUapiConfiguration(currentListenPort: UInt16) -> String {
+        var wgSettings = "listen_port=\(tunnelConfiguration.interface.listenPort ?? currentListenPort)\n"
 
         for (i, peer) in tunnelConfiguration.peers.enumerated() {
             wgSettings.append("public_key=\(peer.publicKey.hexEncodedString())\n")
diff --git a/wireguard-go-bridge/src/api-ios.go b/wireguard-go-bridge/src/api-ios.go
index ff7aab2..3d35d1e 100644
--- a/wireguard-go-bridge/src/api-ios.go
+++ b/wireguard-go-bridge/src/api-ios.go
@@ -128,16 +128,27 @@ func wgTurnOff(tunnelHandle int32) {
 }
 
 //export wgSetConfig
-func wgSetConfig(tunnelHandle int32, settings string) {
+func wgSetConfig(tunnelHandle int32, settings string) int64 {
 	device, ok := tunnelHandles[tunnelHandle]
 	if !ok {
-		return
+		return 0
 	}
 	bufferedSettings := bufio.NewReadWriter(bufio.NewReader(strings.NewReader(settings)), bufio.NewWriter(ioutil.Discard))
 	err := ipcSetOperation(device, bufferedSettings)
 	if err != nil {
 		device.log.Error.Println(err)
+		return err.Code
 	}
+	return 0
+}
+
+//export wgGetListenPort
+func wgGetListenPort(tunnelHandle int32) uint16 {
+	device, ok := tunnelHandles[tunnelHandle]
+	if !ok {
+		return 0
+	}
+	return device.net.port
 }
 
 //export wgVersion
diff --git a/wireguard-go-bridge/wireguard.h b/wireguard-go-bridge/wireguard.h
index 54cb928..fec352d 100644
--- a/wireguard-go-bridge/wireguard.h
+++ b/wireguard-go-bridge/wireguard.h
@@ -14,7 +14,8 @@ typedef void(*logger_fn_t)(int level, const char *msg);
 extern void wgSetLogger(logger_fn_t logger_fn);
 extern int wgTurnOn(gostring_t ifname, gostring_t settings, int32_t tun_fd);
 extern void wgTurnOff(int handle);
-extern void wgSetConfig(int handle, gostring_t settings);
+extern int64_t wgSetConfig(int handle, gostring_t settings);
+extern uint16_t wgGetListenPort(int handle);
 extern char *wgVersion();
 
 #endif