Use IP address library

ATTRIBUTION.md

@@ -43,3 +43,4 @@ FairEmail uses:
 * [Caladea font](https://fonts.google.com/specimen/Caladea). By Andrés Torresi, Carolina Giovanolli. [Apache License 2.0](https://fonts.google.com/specimen/Caladea#license).
 * [Apache Commons Compress](https://commons.apache.org/proper/commons-compress/). Copyright © 2002-2021 The Apache Software Foundation. All Rights Reserved. [Apache License 2.0](https://www.apache.org/licenses/).
 * [LeakCanary](https://github.com/square/leakcanary). Copyright 2015 Square, Inc. [Apache License 2.0](https://github.com/square/leakcanary/blob/main/LICENSE.txt).
+* [IPAddress](https://github.com/seancfoley/IPAddress). Copyright 2016-2018 Sean C Foley. [Apache License 2.0](https://github.com/seancfoley/IPAddress/blob/master/LICENSE).

app/build.gradle

@@ -375,6 +375,7 @@ dependencies {
     def rxjava2_version = "2.2.21"
     def svg_version = "1.4"
     def compress_version = "1.21"
+    def ipaddress_version = "5.3.4"
     def canary_version = "2.8.1"
 
     // https://developer.android.com/jetpack/androidx/releases/startup
@@ -579,6 +580,10 @@ dependencies {
     // https://mvnrepository.com/artifact/org.apache.commons/commons-compress
     implementation "org.apache.commons:commons-compress:$compress_version"
 
+    // https://seancfoley.github.io/IPAddress/
+    // https://mvnrepository.com/artifact/com.github.seancfoley/ipaddress
+    implementation "com.github.seancfoley:ipaddress:$ipaddress_version"
+
     // https://github.com/square/leakcanary
     // https://square.github.io/leakcanary/getting_started/
     // https://mvnrepository.com/artifact/com.squareup.leakcanary/leakcanary-android

app/src/main/assets/ATTRIBUTION.md

@@ -43,3 +43,4 @@ FairEmail uses:
 * [Caladea font](https://fonts.google.com/specimen/Caladea). By Andrés Torresi, Carolina Giovanolli. [Apache License 2.0](https://fonts.google.com/specimen/Caladea#license).
 * [Apache Commons Compress](https://commons.apache.org/proper/commons-compress/). Copyright © 2002-2021 The Apache Software Foundation. All Rights Reserved. [Apache License 2.0](https://www.apache.org/licenses/).
 * [LeakCanary](https://github.com/square/leakcanary). Copyright 2015 Square, Inc. [Apache License 2.0](https://github.com/square/leakcanary/blob/main/LICENSE.txt).
+* [IPAddress](https://github.com/seancfoley/IPAddress). Copyright 2016-2018 Sean C Foley. [Apache License 2.0](https://github.com/seancfoley/IPAddress/blob/master/LICENSE).

app/src/main/java/eu/faircode/email/ConnectionHelper.java

@@ -59,6 +59,8 @@
 import javax.net.ssl.SSLSocket;
 import javax.net.ssl.SSLSocketFactory;
 
+import inet.ipaddr.IPAddressString;
+
 public class ConnectionHelper {
     static final List<String> PREF_NETWORK = Collections.unmodifiableList(Arrays.asList(
             "metered", "roaming", "rlah", "require_validated", "vpn_only" // update network state
@@ -558,23 +560,8 @@ static boolean isLocalAddress(String host) {
 
     static boolean inSubnet(final String ip, final String net, final int prefix) {
         try {
-            byte[] _ip = InetAddress.getByName(ip).getAddress();
-            byte[] _net = InetAddress.getByName(net).getAddress();
-
-            if (_ip.length != _net.length)
-                return false;
-
-            int i = 0;
-            int p = prefix;
-            while (p >= 8) {
-                if (_ip[i] != _net[i])
-                    return false;
-                ++i;
-                p -= 8;
-            }
-
-            int m = (0xFF00 >> p) & 0xFF;
-            return (_ip[i] & m) == (_net[i] & m);
+            return new IPAddressString(net + "/" + prefix).getAddress()
+                    .contains(new IPAddressString(ip).getAddress());
         } catch (Throwable ex) {
             Log.w(ex);
             return false;