Group net package

mobile/src/main/java/be/mygod/vpnhotspot/net/NetUtils.kt

@@ -0,0 +1,38 @@
+package be.mygod.vpnhotspot.net
+
+import android.os.Build
+import android.os.Bundle
+import android.support.annotation.RequiresApi
+import java.io.File
+
+object NetUtils {
+    // hidden constants from ConnectivityManager
+    /**
+     * This is a sticky broadcast since almost forever.
+     *
+     * https://android.googlesource.com/platform/frameworks/base.git/+/2a091d7aa0c174986387e5d56bf97a87fe075bdb%5E%21/services/java/com/android/server/connectivity/Tethering.java
+     */
+    const val ACTION_TETHER_STATE_CHANGED = "android.net.conn.TETHER_STATE_CHANGED"
+    @Deprecated("No longer used on Android 8+ (API 26+)")
+    private const val EXTRA_ACTIVE_TETHER_LEGACY = "activeArray"
+    @RequiresApi(26)
+    private const val EXTRA_ACTIVE_LOCAL_ONLY = "localOnlyArray"
+    @RequiresApi(26)
+    private const val EXTRA_ACTIVE_TETHER = "tetherArray"
+
+    private val spaces = " +".toPattern()
+    private val mac = "^([0-9a-f]{2}:){5}[0-9a-f]{2}$".toPattern()
+
+    fun getTetheredIfaces(extras: Bundle) = if (Build.VERSION.SDK_INT >= 26)
+        extras.getStringArrayList(EXTRA_ACTIVE_TETHER).toSet() + extras.getStringArrayList(EXTRA_ACTIVE_LOCAL_ONLY)
+    else extras.getStringArrayList(EXTRA_ACTIVE_TETHER_LEGACY).toSet()
+
+    fun arp(iface: String? = null) = File("/proc/net/arp").bufferedReader().useLines {
+        // IP address       HW type     Flags       HW address            Mask     Device
+        it.map { it.split(spaces) }
+                .drop(1)
+                .filter { it.size >= 4 && (iface == null || it.getOrNull(5) == iface) &&
+                        mac.matcher(it[3]).matches() }
+                .associateBy({ it[3] }, { it[0] })
+    }
+}