From a104548f7c380cb68a0efba8f8f8beb8d884cb6b Mon Sep 17 00:00:00 2001
From: akwizgran <akwizgran@users.sourceforge.net>
Date: Tue, 28 Aug 2012 14:22:29 +0100
Subject: [PATCH] Allow for the maximum overhead when calculating capacity.
---
.../briar/api/protocol/ProtocolConstants.java | 9 +++--
.../briar/transport/ConnectionWriterImpl.java | 13 ++-----
.../net/sf/briar/transport/FrameWriter.java | 4 +--
.../transport/OutgoingEncryptionLayer.java | 35 ++++++++++++-------
.../briar/transport/ConnectionWriterTest.java | 12 +++----
5 files changed, 37 insertions(+), 36 deletions(-)
diff --git a/api/net/sf/briar/api/protocol/ProtocolConstants.java b/api/net/sf/briar/api/protocol/ProtocolConstants.java
index ba87ec12cf..aa54918a36 100644
--- a/api/net/sf/briar/api/protocol/ProtocolConstants.java
+++ b/api/net/sf/briar/api/protocol/ProtocolConstants.java
@@ -1,19 +1,18 @@
package net.sf.briar.api.protocol;
-import net.sf.briar.api.transport.TransportConstants;
+import static net.sf.briar.api.transport.TransportConstants.MIN_CONNECTION_LENGTH;
public interface ProtocolConstants {
/**
* The maximum length of a serialised packet in bytes. To allow for future
* changes in the protocol, this is smaller than the minimum connection
- * length minus the encryption and authentication overhead.
+ * length minus the maximum encryption and authentication overhead.
*/
- static final int MAX_PACKET_LENGTH =
- TransportConstants.MIN_CONNECTION_LENGTH - 1024;
+ static final int MAX_PACKET_LENGTH = MIN_CONNECTION_LENGTH / 2;
/** The maximum number of transports a node may support. */
- static final int MAX_TRANSPORTS = 50;
+ static final int MAX_TRANSPORTS = 25;
/** The maximum number of properties per transport. */
static final int MAX_PROPERTIES_PER_TRANSPORT = 100;
diff --git a/components/net/sf/briar/transport/ConnectionWriterImpl.java b/components/net/sf/briar/transport/ConnectionWriterImpl.java
index 39ee053790..4932cff5c7 100644
--- a/components/net/sf/briar/transport/ConnectionWriterImpl.java
+++ b/components/net/sf/briar/transport/ConnectionWriterImpl.java
@@ -35,11 +35,7 @@ class ConnectionWriterImpl extends OutputStream implements ConnectionWriter {
}
public long getRemainingCapacity() {
- long capacity = out.getRemainingCapacity();
- int maxPayloadLength = frameLength - HEADER_LENGTH - MAC_LENGTH;
- long frames = (long) Math.ceil((double) capacity / maxPayloadLength);
- long overhead = (frames + 1) * (HEADER_LENGTH + MAC_LENGTH);
- return capacity - overhead - length;
+ return out.getRemainingCapacity();
}
@Override
@@ -83,12 +79,9 @@ class ConnectionWriterImpl extends OutputStream implements ConnectionWriter {
length += len;
}
- private void writeFrame(boolean lastFrame) throws IOException {
+ private void writeFrame(boolean finalFrame) throws IOException {
if(frameNumber > MAX_32_BIT_UNSIGNED) throw new IllegalStateException();
- int capacity = (int) Math.min(frameLength, out.getRemainingCapacity());
- int paddingLength = capacity - HEADER_LENGTH - length - MAC_LENGTH;
- if(paddingLength < 0) throw new IllegalStateException();
- out.writeFrame(frame, length, lastFrame ? 0 : paddingLength, lastFrame);
+ out.writeFrame(frame, length, finalFrame);
length = 0;
frameNumber++;
}
diff --git a/components/net/sf/briar/transport/FrameWriter.java b/components/net/sf/briar/transport/FrameWriter.java
index c3167b411d..947e8bf1b7 100644
--- a/components/net/sf/briar/transport/FrameWriter.java
+++ b/components/net/sf/briar/transport/FrameWriter.java
@@ -5,8 +5,8 @@ import java.io.IOException;
interface FrameWriter {
/** Writes the given frame. */
- void writeFrame(byte[] frame, int payloadLength, int paddingLength,
- boolean lastFrame) throws IOException;
+ void writeFrame(byte[] frame, int payloadLength, boolean finalFrame)
+ throws IOException;
/** Flushes the stack. */
void flush() throws IOException;
diff --git a/components/net/sf/briar/transport/OutgoingEncryptionLayer.java b/components/net/sf/briar/transport/OutgoingEncryptionLayer.java
index c9080a6c5e..9d6a67260c 100644
--- a/components/net/sf/briar/transport/OutgoingEncryptionLayer.java
+++ b/components/net/sf/briar/transport/OutgoingEncryptionLayer.java
@@ -6,6 +6,7 @@ import static net.sf.briar.api.transport.TransportConstants.HEADER_LENGTH;
import static net.sf.briar.api.transport.TransportConstants.IV_LENGTH;
import static net.sf.briar.api.transport.TransportConstants.MAC_LENGTH;
import static net.sf.briar.api.transport.TransportConstants.TAG_LENGTH;
+import static net.sf.briar.util.ByteUtils.MAX_32_BIT_UNSIGNED;
import java.io.IOException;
import java.io.OutputStream;
@@ -33,7 +34,7 @@ class OutgoingEncryptionLayer implements FrameWriter {
AuthenticatedCipher frameCipher, ErasableKey tagKey,
ErasableKey frameKey, int frameLength) {
this.out = out;
- this.capacity = capacity - TAG_LENGTH;
+ this.capacity = capacity;
this.tagCipher = tagCipher;
this.frameCipher = frameCipher;
this.tagKey = tagKey;
@@ -64,17 +65,11 @@ class OutgoingEncryptionLayer implements FrameWriter {
writeTag = false;
}
- public void writeFrame(byte[] frame, int payloadLength, int paddingLength,
- boolean lastFrame) throws IOException {
- int plaintextLength = HEADER_LENGTH + payloadLength + paddingLength;
- int ciphertextLength = plaintextLength + MAC_LENGTH;
- if(ciphertextLength > frameLength)
- throw new IllegalArgumentException();
- if(!lastFrame && ciphertextLength < frameLength)
- throw new IllegalArgumentException();
+ public void writeFrame(byte[] frame, int payloadLength, boolean finalFrame)
+ throws IOException {
// If the initiator's side of the connection is closed without writing
- // any payload or padding, don't write a tag or an empty frame
- if(writeTag && lastFrame && payloadLength + paddingLength == 0) return;
+ // any data, don't write anything to the underlying transport
+ if(writeTag && finalFrame && payloadLength == 0) return;
// Write the tag if required
if(writeTag) {
TagEncoder.encodeTag(ciphertext, tagCipher, tagKey);
@@ -85,10 +80,20 @@ class OutgoingEncryptionLayer implements FrameWriter {
tagKey.erase();
throw e;
}
+ capacity -= TAG_LENGTH;
writeTag = false;
}
// Encode the header
- FrameEncoder.encodeHeader(frame, lastFrame, payloadLength);
+ FrameEncoder.encodeHeader(frame, finalFrame, payloadLength);
+ // Don't pad the final frame
+ int plaintextLength, ciphertextLength;
+ if(finalFrame) {
+ plaintextLength = HEADER_LENGTH + payloadLength;
+ ciphertextLength = plaintextLength + MAC_LENGTH;
+ } else {
+ plaintextLength = frameLength - MAC_LENGTH;
+ ciphertextLength = frameLength;
+ }
// If there's any padding it must all be zeroes
for(int i = HEADER_LENGTH + payloadLength; i < plaintextLength; i++)
frame[i] = 0;
@@ -120,6 +125,10 @@ class OutgoingEncryptionLayer implements FrameWriter {
}
public long getRemainingCapacity() {
- return capacity;
+ long capacityExcludingTag = writeTag ? capacity - TAG_LENGTH : capacity;
+ long frames = capacityExcludingTag / frameLength;
+ long frameNumbers = MAX_32_BIT_UNSIGNED - frameNumber + 1;
+ int maxPayloadLength = frameLength - HEADER_LENGTH - MAC_LENGTH;
+ return maxPayloadLength * Math.min(frames, frameNumbers);
}
}
\ No newline at end of file
diff --git a/test/net/sf/briar/transport/ConnectionWriterTest.java b/test/net/sf/briar/transport/ConnectionWriterTest.java
index 9b7ebc082d..6c416658ec 100644
--- a/test/net/sf/briar/transport/ConnectionWriterTest.java
+++ b/test/net/sf/briar/transport/ConnectionWriterTest.java
@@ -48,14 +48,14 @@ public class ConnectionWriterTest extends BriarTestCase {
MIN_CONNECTION_LENGTH, secret, true);
// Check that the connection writer thinks there's room for a packet
long capacity = w.getRemainingCapacity();
- assertTrue(capacity >= MAX_PACKET_LENGTH);
- assertTrue(capacity <= MIN_CONNECTION_LENGTH);
+ assertTrue(capacity > MAX_PACKET_LENGTH);
+ assertTrue(capacity < MIN_CONNECTION_LENGTH);
// Check that there really is room for a packet
byte[] payload = new byte[MAX_PACKET_LENGTH];
w.getOutputStream().write(payload);
w.getOutputStream().close();
long used = out.size();
- assertTrue(used >= MAX_PACKET_LENGTH);
+ assertTrue(used > MAX_PACKET_LENGTH);
assertTrue(used <= MIN_CONNECTION_LENGTH);
}
@@ -67,14 +67,14 @@ public class ConnectionWriterTest extends BriarTestCase {
MIN_CONNECTION_LENGTH, secret, false);
// Check that the connection writer thinks there's room for a packet
long capacity = w.getRemainingCapacity();
- assertTrue(capacity >= MAX_PACKET_LENGTH);
- assertTrue(capacity <= MIN_CONNECTION_LENGTH);
+ assertTrue(capacity > MAX_PACKET_LENGTH);
+ assertTrue(capacity < MIN_CONNECTION_LENGTH);
// Check that there really is room for a packet
byte[] payload = new byte[MAX_PACKET_LENGTH];
w.getOutputStream().write(payload);
w.getOutputStream().close();
long used = out.size();
- assertTrue(used >= MAX_PACKET_LENGTH);
+ assertTrue(used > MAX_PACKET_LENGTH);
assertTrue(used <= MIN_CONNECTION_LENGTH);
}
}
--
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