/*
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* Copyright (C) 2015 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package android.net.util;
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import java.net.Inet6Address;
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import java.net.InetAddress;
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import java.nio.BufferOverflowException;
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import java.nio.BufferUnderflowException;
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import java.nio.ByteBuffer;
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import java.nio.ShortBuffer;
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import static android.system.OsConstants.IPPROTO_TCP;
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import static android.system.OsConstants.IPPROTO_UDP;
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/**
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* @hide
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*/
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public class IpUtils {
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/**
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* Converts a signed short value to an unsigned int value. Needed
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* because Java does not have unsigned types.
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*/
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private static int intAbs(short v) {
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return v & 0xFFFF;
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}
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/**
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* Performs an IP checksum (used in IP header and across UDP
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* payload) on the specified portion of a ByteBuffer. The seed
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* allows the checksum to commence with a specified value.
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*/
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private static int checksum(ByteBuffer buf, int seed, int start, int end) {
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int sum = seed;
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final int bufPosition = buf.position();
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// set position of original ByteBuffer, so that the ShortBuffer
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// will be correctly initialized
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buf.position(start);
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ShortBuffer shortBuf = buf.asShortBuffer();
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// re-set ByteBuffer position
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buf.position(bufPosition);
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final int numShorts = (end - start) / 2;
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for (int i = 0; i < numShorts; i++) {
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sum += intAbs(shortBuf.get(i));
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}
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start += numShorts * 2;
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// see if a singleton byte remains
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if (end != start) {
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short b = buf.get(start);
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// make it unsigned
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if (b < 0) {
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b += 256;
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}
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sum += b * 256;
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}
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sum = ((sum >> 16) & 0xFFFF) + (sum & 0xFFFF);
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sum = ((sum + ((sum >> 16) & 0xFFFF)) & 0xFFFF);
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int negated = ~sum;
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return intAbs((short) negated);
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}
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private static int pseudoChecksumIPv4(
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ByteBuffer buf, int headerOffset, int protocol, int transportLen) {
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int partial = protocol + transportLen;
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partial += intAbs(buf.getShort(headerOffset + 12));
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partial += intAbs(buf.getShort(headerOffset + 14));
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partial += intAbs(buf.getShort(headerOffset + 16));
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partial += intAbs(buf.getShort(headerOffset + 18));
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return partial;
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}
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private static int pseudoChecksumIPv6(
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ByteBuffer buf, int headerOffset, int protocol, int transportLen) {
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int partial = protocol + transportLen;
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for (int offset = 8; offset < 40; offset += 2) {
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partial += intAbs(buf.getShort(headerOffset + offset));
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}
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return partial;
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}
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private static byte ipversion(ByteBuffer buf, int headerOffset) {
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return (byte) ((buf.get(headerOffset) & (byte) 0xf0) >> 4);
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}
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public static short ipChecksum(ByteBuffer buf, int headerOffset) {
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byte ihl = (byte) (buf.get(headerOffset) & 0x0f);
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return (short) checksum(buf, 0, headerOffset, headerOffset + ihl * 4);
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}
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private static short transportChecksum(ByteBuffer buf, int protocol,
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int ipOffset, int transportOffset, int transportLen) {
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if (transportLen < 0) {
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throw new IllegalArgumentException("Transport length < 0: " + transportLen);
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}
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int sum;
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byte ver = ipversion(buf, ipOffset);
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if (ver == 4) {
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sum = pseudoChecksumIPv4(buf, ipOffset, protocol, transportLen);
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} else if (ver == 6) {
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sum = pseudoChecksumIPv6(buf, ipOffset, protocol, transportLen);
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} else {
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throw new UnsupportedOperationException("Checksum must be IPv4 or IPv6");
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}
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sum = checksum(buf, sum, transportOffset, transportOffset + transportLen);
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if (protocol == IPPROTO_UDP && sum == 0) {
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sum = (short) 0xffff;
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}
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return (short) sum;
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}
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public static short udpChecksum(ByteBuffer buf, int ipOffset, int transportOffset) {
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int transportLen = intAbs(buf.getShort(transportOffset + 4));
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return transportChecksum(buf, IPPROTO_UDP, ipOffset, transportOffset, transportLen);
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}
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public static short tcpChecksum(ByteBuffer buf, int ipOffset, int transportOffset,
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int transportLen) {
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return transportChecksum(buf, IPPROTO_TCP, ipOffset, transportOffset, transportLen);
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}
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public static String addressAndPortToString(InetAddress address, int port) {
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return String.format(
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(address instanceof Inet6Address) ? "[%s]:%d" : "%s:%d",
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address.getHostAddress(), port);
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}
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public static boolean isValidUdpOrTcpPort(int port) {
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return port > 0 && port < 65536;
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}
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}
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