| /* |
| * Copyright (C) 2016 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.system; |
| |
| import static android.system.OsConstants.ICMP6_ECHO_REQUEST; |
| import static android.system.OsConstants.ICMP_ECHO; |
| |
| import java.io.FileDescriptor; |
| import java.net.SocketAddress; |
| |
| /** |
| * A utility class that can create ICMP header bytes corresponding to C's {@code struct icmphdr} |
| * from linux/icmp.h and {@code struct icmp6hdr} from linux/icmpv6.h. The bytes can be passed to |
| * methods like {@link Os#sendto(FileDescriptor, byte[], int, int, int, SocketAddress)}. |
| * |
| * @hide |
| */ |
| public final class IcmpHeaders { |
| |
| private IcmpHeaders() {} |
| |
| /** |
| * Creates the header bytes for an {@link OsConstants#ICMP_ECHO} or |
| * {@link OsConstants#ICMP6_ECHO_REQUEST} message. Code, checksum and identifier are left as |
| * zeros. |
| * |
| * <pre> |
| * 0 1 2 3 |
| * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 |
| * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| * | Type | Code | Checksum | |
| * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| * | Identifier | Sequence Number | |
| * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| * </pre> |
| */ |
| public static byte[] createIcmpEchoHdr(boolean ipv4, int seq) { |
| byte[] bytes = new byte[8]; |
| bytes[0] = ipv4 ? (byte) ICMP_ECHO : (byte) ICMP6_ECHO_REQUEST; |
| // packet[1]: Code is always zero. |
| // packet[2,3]: Checksum is computed by kernel. |
| // packet[4,5]: ID (= port) inserted by kernel. |
| bytes[6] = (byte) (seq >> 8); |
| bytes[7] = (byte) seq; |
| return bytes; |
| } |
| } |