conn: disable sticky sockets on Android

We can't have the netlink listener socket, so it's not possible to
support it. Plus, android networking stack complexity makes it a bit
tricky anyway, so best to leave it disabled.

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

conn/controlfns_linux.go

@@ -7,6 +7,7 @@ package conn
 
 import (
 	"fmt"
+	"runtime"
 	"syscall"
 
 	"golang.org/x/sys/unix"
@@ -36,15 +37,19 @@ func init() {
 			var err error
 			switch network {
 			case "udp4":
+				if runtime.GOOS != "android" {
 					c.Control(func(fd uintptr) {
 						err = unix.SetsockoptInt(int(fd), unix.IPPROTO_IP, unix.IP_PKTINFO, 1)
 					})
+				}
 			case "udp6":
 				c.Control(func(fd uintptr) {
+					if runtime.GOOS != "android" {
 						err = unix.SetsockoptInt(int(fd), unix.IPPROTO_IPV6, unix.IPV6_RECVPKTINFO, 1)
 						if err != nil {
 							return
 						}
+					}
 					err = unix.SetsockoptInt(int(fd), unix.IPPROTO_IPV6, unix.IPV6_V6ONLY, 1)
 				})
 			default:

conn/sticky_default.go

@@ -1,4 +1,4 @@
-//go:build !linux
+//go:build !linux || android
 
 /* SPDX-License-Identifier: MIT
  *
@@ -23,3 +23,5 @@ func setSrcControl(control *[]byte, ep *StdNetEndpoint) {
 // srcControlSize returns the recommended buffer size for pooling sticky control
 // data.
 const srcControlSize = 0
+
+const StdNetSupportsStickySockets = false

conn/sticky_linux.go

@@ -1,3 +1,5 @@
+//go:build linux && !android
+
 /* SPDX-License-Identifier: MIT
  *
  * Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
@@ -111,3 +113,5 @@ func setSrcControl(control *[]byte, ep *StdNetEndpoint) {
 }
 
 var srcControlSize = unix.CmsgSpace(unix.SizeofInet6Pktinfo)
+
+const StdNetSupportsStickySockets = true

conn/sticky_linux_test.go

@@ -1,4 +1,4 @@
-//go:build linux
+//go:build linux && !android
 
 /* SPDX-License-Identifier: MIT
  *

device/sticky_linux.go

@@ -25,6 +25,9 @@ import (
 )
 
 func (device *Device) startRouteListener(bind conn.Bind) (*rwcancel.RWCancel, error) {
+	if !conn.StdNetSupportsStickySockets {
+		return nil, nil
+	}
 	if _, ok := bind.(*conn.StdNetBind); !ok {
 		return nil, nil
 	}