Shuyi Chen | d7955ce | 2013-05-22 14:51:55 -0700 | [diff] [blame] | 1 | // Copyright (c) 1999-2004 Brian Wellington (bwelling@xbill.org) |
| 2 | |
| 3 | package org.xbill.DNS; |
| 4 | |
| 5 | import java.io.*; |
| 6 | import java.util.*; |
| 7 | |
| 8 | /** |
| 9 | * A DNS message header |
| 10 | * @see Message |
| 11 | * |
| 12 | * @author Brian Wellington |
| 13 | */ |
| 14 | |
| 15 | public class Header implements Cloneable { |
| 16 | |
| 17 | private int id; |
| 18 | private int flags; |
| 19 | private int [] counts; |
| 20 | |
| 21 | private static Random random = new Random(); |
| 22 | |
| 23 | /** The length of a DNS Header in wire format. */ |
| 24 | public static final int LENGTH = 12; |
| 25 | |
| 26 | private void |
| 27 | init() { |
| 28 | counts = new int[4]; |
| 29 | flags = 0; |
| 30 | id = -1; |
| 31 | } |
| 32 | |
| 33 | /** |
| 34 | * Create a new empty header. |
| 35 | * @param id The message id |
| 36 | */ |
| 37 | public |
| 38 | Header(int id) { |
| 39 | init(); |
| 40 | setID(id); |
| 41 | } |
| 42 | |
| 43 | /** |
| 44 | * Create a new empty header with a random message id |
| 45 | */ |
| 46 | public |
| 47 | Header() { |
| 48 | init(); |
| 49 | } |
| 50 | |
| 51 | /** |
| 52 | * Parses a Header from a stream containing DNS wire format. |
| 53 | */ |
| 54 | Header(DNSInput in) throws IOException { |
| 55 | this(in.readU16()); |
| 56 | flags = in.readU16(); |
| 57 | for (int i = 0; i < counts.length; i++) |
| 58 | counts[i] = in.readU16(); |
| 59 | } |
| 60 | |
| 61 | /** |
| 62 | * Creates a new Header from its DNS wire format representation |
| 63 | * @param b A byte array containing the DNS Header. |
| 64 | */ |
| 65 | public |
| 66 | Header(byte [] b) throws IOException { |
| 67 | this(new DNSInput(b)); |
| 68 | } |
| 69 | |
| 70 | void |
| 71 | toWire(DNSOutput out) { |
| 72 | out.writeU16(getID()); |
| 73 | out.writeU16(flags); |
| 74 | for (int i = 0; i < counts.length; i++) |
| 75 | out.writeU16(counts[i]); |
| 76 | } |
| 77 | |
| 78 | public byte [] |
| 79 | toWire() { |
| 80 | DNSOutput out = new DNSOutput(); |
| 81 | toWire(out); |
| 82 | return out.toByteArray(); |
| 83 | } |
| 84 | |
| 85 | static private boolean |
| 86 | validFlag(int bit) { |
| 87 | return (bit >= 0 && bit <= 0xF && Flags.isFlag(bit)); |
| 88 | } |
| 89 | |
| 90 | static private void |
| 91 | checkFlag(int bit) { |
| 92 | if (!validFlag(bit)) |
| 93 | throw new IllegalArgumentException("invalid flag bit " + bit); |
| 94 | } |
| 95 | |
| 96 | /** |
| 97 | * Sets a flag to the supplied value |
| 98 | * @see Flags |
| 99 | */ |
| 100 | public void |
| 101 | setFlag(int bit) { |
| 102 | checkFlag(bit); |
| 103 | // bits are indexed from left to right |
| 104 | flags |= (1 << (15 - bit)); |
| 105 | } |
| 106 | |
| 107 | /** |
| 108 | * Sets a flag to the supplied value |
| 109 | * @see Flags |
| 110 | */ |
| 111 | public void |
| 112 | unsetFlag(int bit) { |
| 113 | checkFlag(bit); |
| 114 | // bits are indexed from left to right |
| 115 | flags &= ~(1 << (15 - bit)); |
| 116 | } |
| 117 | |
| 118 | /** |
| 119 | * Retrieves a flag |
| 120 | * @see Flags |
| 121 | */ |
| 122 | public boolean |
| 123 | getFlag(int bit) { |
| 124 | checkFlag(bit); |
| 125 | // bits are indexed from left to right |
| 126 | return (flags & (1 << (15 - bit))) != 0; |
| 127 | } |
| 128 | |
| 129 | boolean [] |
| 130 | getFlags() { |
| 131 | boolean [] array = new boolean[16]; |
| 132 | for (int i = 0; i < array.length; i++) |
| 133 | if (validFlag(i)) |
| 134 | array[i] = getFlag(i); |
| 135 | return array; |
| 136 | } |
| 137 | |
| 138 | /** |
| 139 | * Retrieves the message ID |
| 140 | */ |
| 141 | public int |
| 142 | getID() { |
| 143 | if (id >= 0) |
| 144 | return id; |
| 145 | synchronized (this) { |
| 146 | if (id < 0) |
| 147 | id = random.nextInt(0xffff); |
| 148 | return id; |
| 149 | } |
| 150 | } |
| 151 | |
| 152 | /** |
| 153 | * Sets the message ID |
| 154 | */ |
| 155 | public void |
| 156 | setID(int id) { |
| 157 | if (id < 0 || id > 0xffff) |
| 158 | throw new IllegalArgumentException("DNS message ID " + id + |
| 159 | " is out of range"); |
| 160 | this.id = id; |
| 161 | } |
| 162 | |
| 163 | /** |
| 164 | * Sets the message's rcode |
| 165 | * @see Rcode |
| 166 | */ |
| 167 | public void |
| 168 | setRcode(int value) { |
| 169 | if (value < 0 || value > 0xF) |
| 170 | throw new IllegalArgumentException("DNS Rcode " + value + |
| 171 | " is out of range"); |
| 172 | flags &= ~0xF; |
| 173 | flags |= value; |
| 174 | } |
| 175 | |
| 176 | /** |
| 177 | * Retrieves the mesasge's rcode |
| 178 | * @see Rcode |
| 179 | */ |
| 180 | public int |
| 181 | getRcode() { |
| 182 | return flags & 0xF; |
| 183 | } |
| 184 | |
| 185 | /** |
| 186 | * Sets the message's opcode |
| 187 | * @see Opcode |
| 188 | */ |
| 189 | public void |
| 190 | setOpcode(int value) { |
| 191 | if (value < 0 || value > 0xF) |
| 192 | throw new IllegalArgumentException("DNS Opcode " + value + |
| 193 | "is out of range"); |
| 194 | flags &= 0x87FF; |
| 195 | flags |= (value << 11); |
| 196 | } |
| 197 | |
| 198 | /** |
| 199 | * Retrieves the mesasge's opcode |
| 200 | * @see Opcode |
| 201 | */ |
| 202 | public int |
| 203 | getOpcode() { |
| 204 | return (flags >> 11) & 0xF; |
| 205 | } |
| 206 | |
| 207 | void |
| 208 | setCount(int field, int value) { |
| 209 | if (value < 0 || value > 0xFFFF) |
| 210 | throw new IllegalArgumentException("DNS section count " + |
| 211 | value + " is out of range"); |
| 212 | counts[field] = value; |
| 213 | } |
| 214 | |
| 215 | void |
| 216 | incCount(int field) { |
| 217 | if (counts[field] == 0xFFFF) |
| 218 | throw new IllegalStateException("DNS section count cannot " + |
| 219 | "be incremented"); |
| 220 | counts[field]++; |
| 221 | } |
| 222 | |
| 223 | void |
| 224 | decCount(int field) { |
| 225 | if (counts[field] == 0) |
| 226 | throw new IllegalStateException("DNS section count cannot " + |
| 227 | "be decremented"); |
| 228 | counts[field]--; |
| 229 | } |
| 230 | |
| 231 | /** |
| 232 | * Retrieves the record count for the given section |
| 233 | * @see Section |
| 234 | */ |
| 235 | public int |
| 236 | getCount(int field) { |
| 237 | return counts[field]; |
| 238 | } |
| 239 | |
| 240 | /** Converts the header's flags into a String */ |
| 241 | public String |
| 242 | printFlags() { |
| 243 | StringBuffer sb = new StringBuffer(); |
| 244 | |
| 245 | for (int i = 0; i < 16; i++) |
| 246 | if (validFlag(i) && getFlag(i)) { |
| 247 | sb.append(Flags.string(i)); |
| 248 | sb.append(" "); |
| 249 | } |
| 250 | return sb.toString(); |
| 251 | } |
| 252 | |
| 253 | String |
| 254 | toStringWithRcode(int newrcode) { |
| 255 | StringBuffer sb = new StringBuffer(); |
| 256 | |
| 257 | sb.append(";; ->>HEADER<<- "); |
| 258 | sb.append("opcode: " + Opcode.string(getOpcode())); |
| 259 | sb.append(", status: " + Rcode.string(newrcode)); |
| 260 | sb.append(", id: " + getID()); |
| 261 | sb.append("\n"); |
| 262 | |
| 263 | sb.append(";; flags: " + printFlags()); |
| 264 | sb.append("; "); |
| 265 | for (int i = 0; i < 4; i++) |
| 266 | sb.append(Section.string(i) + ": " + getCount(i) + " "); |
| 267 | return sb.toString(); |
| 268 | } |
| 269 | |
| 270 | /** Converts the header into a String */ |
| 271 | public String |
| 272 | toString() { |
| 273 | return toStringWithRcode(getRcode()); |
| 274 | } |
| 275 | |
| 276 | /* Creates a new Header identical to the current one */ |
| 277 | public Object |
| 278 | clone() { |
| 279 | Header h = new Header(); |
| 280 | h.id = id; |
| 281 | h.flags = flags; |
| 282 | System.arraycopy(counts, 0, h.counts, 0, counts.length); |
| 283 | return h; |
| 284 | } |
| 285 | |
| 286 | } |