conn: unbreak boundif on android

Another thing never tested ever.

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

conn/boundif_android.go

@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2017-2020 WireGuard LLC. All Rights Reserved.
+ */
+
+package conn
+
+func (bind *nativeBind) PeekLookAtSocketFd4() (fd int, err error) {
+	sysconn, err := bind.ipv4.SyscallConn()
+	if err != nil {
+		return -1, err
+	}
+	err = sysconn.Control(func(f uintptr) {
+		fd = int(f)
+	})
+	if err != nil {
+		return -1, err
+	}
+	return
+}
+
+func (bind *nativeBind) PeekLookAtSocketFd6() (fd int, err error) {
+	sysconn, err := bind.ipv6.SyscallConn()
+	if err != nil {
+		return -1, err
+	}
+	err = sysconn.Control(func(f uintptr) {
+		fd = int(f)
+	})
+	if err != nil {
+		return -1, err
+	}
+	return
+}

conn/conn.go

@@ -57,6 +57,13 @@ type BindSocketToInterface interface {
 	BindSocketToInterface6(interfaceIndex uint32, blackhole bool) error
 }
 
+// PeekLookAtSocketFd is implemented by Bind objects that support having their
+// file descriptor peeked at.
+type PeekLookAtSocketFd interface {
+	PeekLookAtSocketFd4() (fd int, err error)
+	PeekLookAtSocketFd6() (fd int, err error)
+}
+
 // An Endpoint maintains the source/destination caching for a peer.
 //
 //	dst : the remote address of a peer ("endpoint" in uapi terminology)

device/bindsocketshim.go

@@ -34,3 +34,27 @@ func (device *Device) BindSocketToInterface6(interfaceIndex uint32, blackhole bo
 	}
 	return nil
 }
+
+// TODO(crawshaw): this method is a compatibility shim. Replace with direct use of conn.
+func (device *Device) PeekLookAtSocketFd4() (fd int, err error) {
+	if device.net.bind == nil {
+		return -1, errors.New("Bind is not yet initialized")
+	}
+
+	if iface, ok := device.net.bind.(conn.PeekLookAtSocketFd); ok {
+		return iface.PeekLookAtSocketFd4()
+	}
+	return -1, errors.New("unimplemented")
+}
+
+// TODO(crawshaw): this method is a compatibility shim. Replace with direct use of conn.
+func (device *Device) PeekLookAtSocketFd6() (fd int, err error) {
+	if device.net.bind == nil {
+		return -1, errors.New("Bind is not yet initialized")
+	}
+
+	if iface, ok := device.net.bind.(conn.PeekLookAtSocketFd); ok {
+		return iface.PeekLookAtSocketFd6()
+	}
+	return -1, errors.New("unimplemented")
+}

device/boundif_android.go

@@ -1,44 +0,0 @@
-/* SPDX-License-Identifier: MIT
- *
- * Copyright (C) 2017-2020 WireGuard LLC. All Rights Reserved.
- */
-
-package device
-
-import "errors"
-
-func (device *Device) PeekLookAtSocketFd4() (fd int, err error) {
-	nb, ok := device.net.bind.(*nativeBind)
-	if !ok {
-		return 0, errors.New("no socket exists")
-	}
-	sysconn, err := nb.ipv4.SyscallConn()
-	if err != nil {
-		return
-	}
-	err = sysconn.Control(func(f uintptr) {
-		fd = int(f)
-	})
-	if err != nil {
-		return
-	}
-	return
-}
-
-func (device *Device) PeekLookAtSocketFd6() (fd int, err error) {
-	nb, ok := device.net.bind.(*nativeBind)
-	if !ok {
-		return 0, errors.New("no socket exists")
-	}
-	sysconn, err := nb.ipv6.SyscallConn()
-	if err != nil {
-		return
-	}
-	err = sysconn.Control(func(f uintptr) {
-		fd = int(f)
-	})
-	if err != nil {
-		return
-	}
-	return
-}