https://bz.apache.org/bugzilla/show_bug.cgi?id=63019
Bug ID: 63019
Summary: Websocket frame header encoding + fix
Product: Tomcat 8
Version: 8.5.32
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P2
Component: WebSocket
Assignee: dev@tomcat.apache.org
Reporter: benoit.courti...@glintware.fr
Target Milestone: ----
Hi,
i found that sending non 0 offseted bytebuffer through websocket does not work.
I guessed bug is at org.apache.tomcat.websocket.WsRemoteEndpointImplBase.java,
- function writeHeader
- lines 747 to 770
- all occurences of payload.limit() should be replaced by payload.remaining()
Let's see it in details :
>> private static void writeHeader(ByteBuffer headerBuffer, boolean fin,
>> int rsv, byte opCode, boolean masked, ByteBuffer payload,
>> byte[] mask, boolean first) {
>> [...]
>> // Next write the mask && length length
>> if (payload.limit() < 126) {
>> headerBuffer.put((byte) (payload.limit() | b));
>> } else if (payload.limit() < 65536) {
>> headerBuffer.put((byte) (126 | b));
>> headerBuffer.put((byte) (payload.limit() >>> 8));
>> headerBuffer.put((byte) (payload.limit() & 0xFF));
>> } else {
>> // Will never be more than 2^31-1
>> headerBuffer.put((byte) (127 | b));
>> headerBuffer.put((byte) 0);
>> headerBuffer.put((byte) 0);
>> headerBuffer.put((byte) 0);
>> headerBuffer.put((byte) 0);
>> headerBuffer.put((byte) (payload.limit() >>> 24));
>> headerBuffer.put((byte) (payload.limit() >>> 16));
>> headerBuffer.put((byte) (payload.limit() >>> 8));
>> headerBuffer.put((byte) (payload.limit() & 0xFF));
>> }
>> if (masked) {
>> headerBuffer.put(mask[0]);
>> headerBuffer.put(mask[1]);
>> headerBuffer.put(mask[2]);
>> headerBuffer.put(mask[3]);
>> }
>> }
payload.limit() is ***NOT*** the length, it will be equal to
payload.remaining() ***ONLY*** if offset = 0 and position = 0...
Even if it is the case most of the time, sometimes it is not.
For now, as a workaround I copy my buffer to a fresh one 0 offseted before
sending thus leading to a slight performance hit.
Best regards,
Benoit
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