android: Add helper to parse IP addresses from strings

Using InetAddress.fromName() is not ideal as it might result in a DNS
resolution, which causes an exception if we do it from the main thread.

src/frontends/android/app/src/main/java/org/strongswan/android/utils/Utils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2014-2017 Tobias Brunner
+ * Copyright (C) 2014-2019 Tobias Brunner
  * HSR Hochschule fuer Technik Rapperswil
  *
  * This program is free software; you can redistribute it and/or modify it
@@ -16,6 +16,9 @@
 package org.strongswan.android.utils;
 
 
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+
 public class Utils
 {
 	static final char[] HEXDIGITS = "0123456789abcdef".toCharArray();
@@ -46,4 +49,29 @@ public class Utils
 	 * @return true if valid
 	 */
 	public native static boolean isProposalValid(boolean ike, String proposal);
+
+	/**
+	 * Parse an IP address without doing a name lookup
+	 *
+	 * @param address IP address string
+	 * @return address bytes if valid
+	 */
+	private native static byte[] parseInetAddressBytes(String address);
+
+	/**
+	 * Parse an IP address without doing a name lookup (as compared to InetAddress.fromName())
+	 *
+	 * @param address IP address string
+	 * @return address if valid
+	 * @throws UnknownHostException if address is invalid
+	 */
+	public static InetAddress parseInetAddress(String address) throws UnknownHostException
+	{
+		byte[] bytes = parseInetAddressBytes(address);
+		if (bytes == null)
+		{
+			throw new UnknownHostException();
+		}
+		return InetAddress.getByAddress(bytes);
+	}
 }

src/frontends/android/app/src/main/jni/libandroidbridge/charonservice.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2012-2018 Tobias Brunner
+ * Copyright (C) 2012-2019 Tobias Brunner
  * Copyright (C) 2012 Giuliano Grassi
  * Copyright (C) 2012 Ralf Sager
  * HSR Hochschule fuer Technik Rapperswil
@@ -758,3 +758,34 @@ JNI_METHOD_P(org_strongswan_android_utils, Utils, isProposalValid, jboolean,
 	library_deinit();
 	return valid;
 }
+
+/**
+ * Utility function to parse an IP address from a string (static, so `this` is the class)
+ */
+JNI_METHOD_P(org_strongswan_android_utils, Utils, parseInetAddressBytes, jbyteArray,
+	jstring address)
+{
+	jbyteArray bytes;
+	host_t *host;
+	char *str;
+
+	dbg = dbg_android;
+
+	if (!library_init(NULL, "charon"))
+	{
+		library_deinit();
+		return NULL;
+	}
+	str = androidjni_convert_jstring(env, address);
+	host = host_create_from_string(str, 0);
+	if (!host)
+	{
+		free(str);
+		return NULL;
+	}
+	bytes = byte_array_from_chunk(env, host->get_address(host));
+	host->destroy(host);
+	free(str);
+	library_deinit();
+	return bytes;
+}