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add to javadoc and adjust logging

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zzz
2009-12-19 16:52:18 +00:00
parent 4baff9fbab
commit f0d444b32e
1 changed files with 65 additions and 8 deletions
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73
router/java/src/net/i2p/router/tunnel/FragmentHandler.java
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@ -21,6 +21,65 @@ import net.i2p.util.SimpleTimer;
* Handle fragments at the endpoint of a tunnel, peeling off fully completed
* I2NPMessages when they arrive, and dropping fragments if they take too long
* to arrive.
*
* From tunnel-alt.html:
<p>When the gateway wants to deliver data through the tunnel, it first
gathers zero or more <a href="i2np.html">I2NP</a> messages, selects how much padding will be used,
fragments it across the necessary number of 1KB tunnel messages, and decides how
each I2NP message should be handled by the tunnel endpoint, encoding that
data into the raw tunnel payload:</p>
<ul>
<li>the first 4 bytes of the SHA256 of the remaining preprocessed data concatenated
with the IV, using the IV as will be seen on the tunnel endpoint (for
outbound tunnels) or the IV as was seen on the tunnel gateway (for inbound
tunnels) (see below for IV processing).</li>
<li>0 or more bytes containing random nonzero integers</li>
<li>1 byte containing 0x00</li>
<li>a series of zero or more { instructions, message } pairs</li>
</ul>
<p>The instructions are encoded with a single control byte, followed by any
necessary additional information. The first bit in that control byte determines
how the remainder of the header is interpreted - if it is not set, the message
is either not fragmented or this is the first fragment in the message. If it is
set, this is a follow on fragment.</p>
<p>With the first bit being 0, the instructions are:</p>
<ul>
<li>1 byte control byte:<pre>
bit 0: is follow on fragment? (1 = true, 0 = false, must be 0)
bits 1-2: delivery type
(0x0 = LOCAL, 0x01 = TUNNEL, 0x02 = ROUTER)
bit 3: delay included? (1 = true, 0 = false)
bit 4: fragmented? (1 = true, 0 = false)
bit 5: extended options? (1 = true, 0 = false)
bits 6-7: reserved</pre></li>
<li>if the delivery type was TUNNEL, a 4 byte tunnel ID</li>
<li>if the delivery type was TUNNEL or ROUTER, a 32 byte router hash</li>
<li>if the delay included flag is true, a 1 byte value:<pre>
bit 0: type (0 = strict, 1 = randomized)
bits 1-7: delay exponent (2^value minutes)</pre></li>
<li>if the fragmented flag is true, a 4 byte message ID</li>
<li>if the extended options flag is true:<pre>
= a 1 byte option size (in bytes)
= that many bytes</pre></li>
<li>2 byte size of the I2NP message or this fragment</li>
</ul>
<p>If the first bit being 1, the instructions are:</p>
<ul>
<li>1 byte control byte:<pre>
bit 0: is follow on fragment? (1 = true, 0 = false, must be 1)
bits 1-6: fragment number
bit 7: is last? (1 = true, 0 = false)</pre></li>
<li>4 byte message ID (same one defined in the first fragment)</li>
<li>2 byte size of this fragment</li>
</ul>
<p>The I2NP message is encoded in its standard form, and the
preprocessed payload must be padded to a multiple of 16 bytes.</p>
*
*/
public class FragmentHandler {
@ -165,21 +224,19 @@ public class FragmentHandler {
_log.debug("endpoint IV: " + Base64.encode(preV, validLength - HopProcessor.IV_LENGTH, HopProcessor.IV_LENGTH));
Hash v = _context.sha().calculateHash(preV, 0, validLength);
_validateCache.release(ba);
//Hash v = _context.sha().calculateHash(preV, 0, validLength);
boolean eq = DataHelper.eq(v.getData(), 0, preprocessed, offset + HopProcessor.IV_LENGTH, 4);
if (!eq) {
if (_log.shouldLog(Log.WARN))
_log.warn("Corrupt tunnel message - verification fails: \n" + Base64.encode(preprocessed, offset+HopProcessor.IV_LENGTH, 4)
+ "\n" + Base64.encode(v.getData(), 0, 4));
if (_log.shouldLog(Log.WARN))
_log.warn("nomatching endpoint: # pad bytes: " + (paddingEnd-(HopProcessor.IV_LENGTH+4)-1) + "\n"
if (_log.shouldLog(Log.WARN)) {
_log.warn("Corrupt tunnel message - verification fails: " + Base64.encode(preprocessed, offset+HopProcessor.IV_LENGTH, 4)
+ " != " + Base64.encode(v.getData(), 0, 4));
_log.warn("No matching endpoint: # pad bytes: " + (paddingEnd-(HopProcessor.IV_LENGTH+4)-1)
+ " offset=" + offset + " length=" + length + " paddingEnd=" + paddingEnd
+ Base64.encode(preprocessed, offset, length));
}
}
_validateCache.release(ba);
if (eq) {
int excessPadding = paddingEnd - (HopProcessor.IV_LENGTH + 4 + 1);
if (excessPadding > 0) // suboptimal fragmentation