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