1 /* 2 * Copyright (C) 2020 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package android.net.netlink; 18 19 import static android.system.OsConstants.AF_INET6; 20 21 import androidx.annotation.NonNull; 22 23 import java.net.Inet6Address; 24 import java.net.InetAddress; 25 import java.net.UnknownHostException; 26 import java.nio.BufferUnderflowException; 27 import java.nio.ByteBuffer; 28 import java.nio.ByteOrder; 29 30 /** 31 * A NetlinkMessage subclass for RTM_NEWNDUSEROPT messages. 32 */ 33 public class NduseroptMessage extends NetlinkMessage { 34 public static final int STRUCT_SIZE = 16; 35 36 static final int NDUSEROPT_SRCADDR = 1; 37 38 /** The address family. Presumably always AF_INET6. */ 39 public final byte family; 40 /** 41 * The total length in bytes of the options that follow this structure. 42 * Actually a 16-bit unsigned integer. 43 */ 44 public final int opts_len; 45 /** The interface index on which the options were received. */ 46 public final int ifindex; 47 /** The ICMP type of the packet that contained the options. */ 48 public final byte icmp_type; 49 /** The ICMP code of the packet that contained the options. */ 50 public final byte icmp_code; 51 52 /** 53 * ND option that was in this message. 54 * Even though the length field is called "opts_len", the kernel only ever sends one option per 55 * message. It is unlikely that this will ever change as it would break existing userspace code. 56 * But if it does, we can simply update this code, since userspace is typically newer than the 57 * kernel. 58 */ 59 public final NdOption option; 60 61 /** The IP address that sent the packet containing the option. */ 62 public final InetAddress srcaddr; 63 NduseroptMessage(@onNull StructNlMsgHdr header, @NonNull ByteBuffer buf)64 NduseroptMessage(@NonNull StructNlMsgHdr header, @NonNull ByteBuffer buf) 65 throws UnknownHostException { 66 super(header); 67 68 // The structure itself. 69 buf.order(ByteOrder.nativeOrder()); // Restored in the finally clause inside parse(). 70 final int start = buf.position(); 71 family = buf.get(); 72 buf.get(); // Skip 1 byte of padding. 73 opts_len = Short.toUnsignedInt(buf.getShort()); 74 ifindex = buf.getInt(); 75 icmp_type = buf.get(); 76 icmp_code = buf.get(); 77 buf.position(buf.position() + 6); // Skip 6 bytes of padding. 78 79 // The ND option. 80 // Ensure we don't read past opts_len even if the option length is invalid. 81 // Note that this check is not really necessary since if the option length is not valid, 82 // this struct won't be very useful to the caller. 83 buf.order(ByteOrder.BIG_ENDIAN); 84 int oldLimit = buf.limit(); 85 buf.limit(start + STRUCT_SIZE + opts_len); 86 try { 87 option = NdOption.parse(buf); 88 } finally { 89 buf.limit(oldLimit); 90 } 91 92 // The source address. 93 int newPosition = start + STRUCT_SIZE + opts_len; 94 if (newPosition >= buf.limit()) { 95 throw new IllegalArgumentException("ND options extend past end of buffer"); 96 } 97 buf.position(newPosition); 98 99 StructNlAttr nla = StructNlAttr.parse(buf); 100 if (nla == null || nla.nla_type != NDUSEROPT_SRCADDR || nla.nla_value == null) { 101 throw new IllegalArgumentException("Invalid source address in ND useropt"); 102 } 103 if (family == AF_INET6) { 104 // InetAddress.getByAddress only looks at the ifindex if the address type needs one. 105 srcaddr = Inet6Address.getByAddress(null /* hostname */, nla.nla_value, ifindex); 106 } else { 107 srcaddr = InetAddress.getByAddress(nla.nla_value); 108 } 109 } 110 111 /** 112 * Parses a StructNduseroptmsg from a {@link ByteBuffer}. 113 * 114 * @param header the netlink message header. 115 * @param buf The buffer from which to parse the option. The buffer's byte order must be 116 * {@link java.nio.ByteOrder#BIG_ENDIAN}. 117 * @return the parsed option, or {@code null} if the option could not be parsed successfully 118 * (for example, if it was truncated, or if the prefix length code was wrong). 119 */ parse(@onNull StructNlMsgHdr header, @NonNull ByteBuffer buf)120 public static NduseroptMessage parse(@NonNull StructNlMsgHdr header, @NonNull ByteBuffer buf) { 121 if (buf == null || buf.remaining() < STRUCT_SIZE) return null; 122 ByteOrder oldOrder = buf.order(); 123 try { 124 return new NduseroptMessage(header, buf); 125 } catch (IllegalArgumentException | UnknownHostException | BufferUnderflowException e) { 126 // Not great, but better than throwing an exception that might crash the caller. 127 // Convention in this package is that null indicates that the option was truncated, so 128 // callers must already handle it. 129 return null; 130 } finally { 131 buf.order(oldOrder); 132 } 133 } 134 135 @Override toString()136 public String toString() { 137 return String.format("Nduseroptmsg(%d, %d, %d, %d, %d, %s)", 138 family, opts_len, ifindex, Byte.toUnsignedInt(icmp_type), 139 Byte.toUnsignedInt(icmp_code), srcaddr.getHostAddress()); 140 } 141 } 142