Feature/exit node Android (#1916)

Support exit node on Android.
With the protect socket function, we mark every connection that should be used out of VPN.

util/net/dialer_android.go

@@ -0,0 +1,25 @@
+package net
+
+import (
+	"syscall"
+
+	log "github.com/sirupsen/logrus"
+)
+
+func (d *Dialer) init() {
+	d.Dialer.Control = func(_, _ string, c syscall.RawConn) error {
+		err := c.Control(func(fd uintptr) {
+			androidProtectSocketLock.Lock()
+			f := androidProtectSocket
+			androidProtectSocketLock.Unlock()
+			if f == nil {
+				return
+			}
+			ok := f(int32(fd))
+			if !ok {
+				log.Errorf("failed to protect socket: %d", fd)
+			}
+		})
+		return err
+	}
+}

util/net/dialer_ios.go

@@ -1,5 +1,3 @@
-//go:build android || ios
-
 package net
 
 import (

util/net/dialer_nonios.go

@@ -1,4 +1,4 @@
-//go:build !android && !ios
+//go:build !ios
 
 package net
 
@@ -36,7 +36,7 @@ func AddDialerCloseHook(hook DialerCloseHookFunc) {
 	dialerCloseHooks = append(dialerCloseHooks, hook)
 }
 
-// RemoveDialerHook removes all dialer hooks.
+// RemoveDialerHooks removes all dialer hooks.
 func RemoveDialerHooks() {
 	dialerDialHooksMutex.Lock()
 	defer dialerDialHooksMutex.Unlock()

util/net/dialer_nonlinux.go

@@ -1,4 +1,4 @@
-//go:build !linux || android
+//go:build !linux
 
 package net
 

util/net/listener_android.go

@@ -0,0 +1,26 @@
+package net
+
+import (
+	"syscall"
+
+	log "github.com/sirupsen/logrus"
+)
+
+// init configures the net.ListenerConfig Control function to set the fwmark on the socket
+func (l *ListenerConfig) init() {
+	l.ListenConfig.Control = func(_, _ string, c syscall.RawConn) error {
+		err := c.Control(func(fd uintptr) {
+			androidProtectSocketLock.Lock()
+			f := androidProtectSocket
+			androidProtectSocketLock.Unlock()
+			if f == nil {
+				return
+			}
+			ok := f(int32(fd))
+			if !ok {
+				log.Errorf("failed to protect listener socket: %d", fd)
+			}
+		})
+		return err
+	}
+}

util/net/listener_ios.go

@@ -1,4 +1,4 @@
-//go:build android || ios
+//go:build ios
 
 package net
 

util/net/listener_nonios.go

@@ -1,4 +1,4 @@
-//go:build !android && !ios
+//go:build !ios
 
 package net
 

util/net/listener_nonlinux.go

@@ -1,4 +1,4 @@
-//go:build !linux || android
+//go:build !linux
 
 package net
 

util/net/protectsocket_android.go

@@ -0,0 +1,14 @@
+package net
+
+import "sync"
+
+var (
+	androidProtectSocketLock sync.Mutex
+	androidProtectSocket     func(fd int32) bool
+)
+
+func SetAndroidProtectSocketFn(f func(fd int32) bool) {
+	androidProtectSocketLock.Lock()
+	androidProtectSocket = f
+	androidProtectSocketLock.Unlock()
+}