From 3c2cdfea1c14ca1099fe21387f0611a162d01f9c Mon Sep 17 00:00:00 2001
From: Neil Alexander <neilalexander@users.noreply.github.com>
Date: Sun, 10 Mar 2019 18:05:27 +0000
Subject: [PATCH] Keep AWDL awake, or wake it up again after a minute if
 suspended for some reason (e.g. sleep)

---
 src/yggdrasil/multicast.go         |  2 +-
 src/yggdrasil/multicast_darwin.go  | 46 ++++++++++++++++++++++--------
 src/yggdrasil/multicast_other.go   |  2 +-
 src/yggdrasil/multicast_unix.go    |  2 +-
 src/yggdrasil/multicast_windows.go |  2 +-
 5 files changed, 38 insertions(+), 16 deletions(-)

diff --git a/src/yggdrasil/multicast.go b/src/yggdrasil/multicast.go
index bf4b2a7..a29bbc7 100644
--- a/src/yggdrasil/multicast.go
+++ b/src/yggdrasil/multicast.go
@@ -57,7 +57,7 @@ func (m *multicast) start() error {
 			// Windows can't set this flag, so we need to handle it in other ways
 		}
 
-		m.multicastWake()
+		go m.multicastStarted()
 		go m.listen()
 		go m.announce()
 	}
diff --git a/src/yggdrasil/multicast_darwin.go b/src/yggdrasil/multicast_darwin.go
index 66c1824..5364611 100644
--- a/src/yggdrasil/multicast_darwin.go
+++ b/src/yggdrasil/multicast_darwin.go
@@ -6,24 +6,46 @@ package yggdrasil
 #cgo CFLAGS: -x objective-c
 #cgo LDFLAGS: -framework Foundation
 #import <Foundation/Foundation.h>
-void WakeUpAWDL() {
-	NSNetServiceBrowser *serviceBrowser;
-
-	serviceBrowser = [[NSNetServiceBrowser alloc] init];
-	serviceBrowser.includesPeerToPeer = YES;
+NSNetServiceBrowser *serviceBrowser;
+void StartAWDLBrowsing() {
+	if (serviceBrowser == nil) {
+		serviceBrowser = [[NSNetServiceBrowser alloc] init];
+		serviceBrowser.includesPeerToPeer = YES;
+	}
 	[serviceBrowser searchForServicesOfType:@"_yggdrasil._tcp" inDomain:@""];
 }
+void StopAWDLBrowsing() {
+	if (serviceBrowser == nil) {
+		return;
+	}
+	[serviceBrowser stop];
+}
 */
 import "C"
-import "syscall"
-import "golang.org/x/sys/unix"
+import (
+	"syscall"
+	"time"
 
-func (m *multicast) multicastWake() {
-	for _, intf := range m.interfaces() {
-		if intf.Name == "awdl0" {
-			m.core.log.Infoln("Multicast discovery is waking up AWDL")
-			C.WakeUpAWDL()
+	"golang.org/x/sys/unix"
+)
+
+var awdlGoroutineStarted bool
+
+func (m *multicast) multicastStarted() {
+	if awdlGoroutineStarted {
+		return
+	}
+	m.core.log.Infoln("Multicast discovery will wake up AWDL if required")
+	awdlGoroutineStarted = true
+	for {
+		C.StopAWDLBrowsing()
+		for _, intf := range m.interfaces() {
+			if intf.Name == "awdl0" {
+				C.StartAWDLBrowsing()
+				break
+			}
 		}
+		time.Sleep(time.Minute)
 	}
 }
 
diff --git a/src/yggdrasil/multicast_other.go b/src/yggdrasil/multicast_other.go
index 043dd3a..e20bbda 100644
--- a/src/yggdrasil/multicast_other.go
+++ b/src/yggdrasil/multicast_other.go
@@ -4,7 +4,7 @@ package yggdrasil
 
 import "syscall"
 
-func (m *multicast) multicastWake() {
+func (m *multicast) multicastStarted() {
 
 }
 
diff --git a/src/yggdrasil/multicast_unix.go b/src/yggdrasil/multicast_unix.go
index 4237481..3da1ab4 100644
--- a/src/yggdrasil/multicast_unix.go
+++ b/src/yggdrasil/multicast_unix.go
@@ -5,7 +5,7 @@ package yggdrasil
 import "syscall"
 import "golang.org/x/sys/unix"
 
-func (m *multicast) multicastWake() {
+func (m *multicast) multicastStarted() {
 
 }
 
diff --git a/src/yggdrasil/multicast_windows.go b/src/yggdrasil/multicast_windows.go
index 14c9312..3e07f6c 100644
--- a/src/yggdrasil/multicast_windows.go
+++ b/src/yggdrasil/multicast_windows.go
@@ -5,7 +5,7 @@ package yggdrasil
 import "syscall"
 import "golang.org/x/sys/windows"
 
-func (m *multicast) multicastWake() {
+func (m *multicast) multicastStarted() {
 
 }