extmod/modwebsocket: Enable split frames and test them.

This fixes several assertion errors that were found in fuzz testing, for
unimplemented portions of the websocket spec.  The assertions were either
turned into Python exceptions, or the missing functionality was
implemented.

Split frames are now enabled and work, enabling reception of frames up to
64kB (assuming they are encoded with a 16-bit size field).

Frames with a 64-bit size fields remain unsupported but no longer result in
an assertion error.  Instead, Initial reception of such a frame will result
in OSError(EIO) and subsequent operations on the same websocket will fail
because framing has been lost.

Transmitting frames larger than 64kB is unsupported.  Attempting to
transmit such a frame will result in OSError(ENOBUFS).  Subsequent
operations on the websocket are possible.

Signed-off-by: Jeff Epler <jepler@gmail.com>

tests/extmod/websocket_basic.py

@@ -13,6 +13,13 @@ def ws_read(msg, sz):
     return ws.read(sz)
 
 
+# put raw data in the stream and do a series of websocket read
+def ws_readn(msg, *args):
+    ws = websocket.websocket(io.BytesIO(msg))
+    for sz in args:
+        yield ws.read(sz)
+
+
 # do a websocket write and then return the raw data from the stream
 def ws_write(msg, sz):
     s = io.BytesIO()
@@ -24,18 +31,28 @@ def ws_write(msg, sz):
 
 # basic frame
 print(ws_read(b"\x81\x04ping", 4))
-print(ws_read(b"\x80\x04ping", 4))  # FRAME_CONT
 print(ws_write(b"pong", 6))
 
-# split frames are not supported
-# print(ws_read(b"\x01\x04ping", 4))
+# split frames and irregular size reads
+for s in ws_readn(b"\x01\x04ping\x00\x04Ping\x80\x04PING", 6, 4, 2, 2):
+    print(s)
 
 # extended payloads
 print(ws_read(b"\x81~\x00\x80" + b"ping" * 32, 128))
 print(ws_write(b"pong" * 32, 132))
 
-# mask (returned data will be 'mask' ^ 'mask')
-print(ws_read(b"\x81\x84maskmask", 4))
+# 64-bit payload size, unsupported by MicroPython implementation. Framing is lost.
+msg = b"\x81\x7f\x00\x00\x00\x00\x00\x00\x00\x80" + b"ping" * 32
+ws = websocket.websocket(io.BytesIO(msg))
+try:
+    print(ws.read(1))
+except OSError as e:
+    print("ioctl: EIO:", e.errno == errno.EIO)
+
+# mask (returned data will be 'maskmask' ^ 'maskMASK')
+print(ws_read(b"\x81\x88maskmaskMASK", 8))
+# mask w/2-byte payload len (returned data will be 'maskmask' ^ 'maskMASK')
+print(ws_read(b"\x81\xfe\x00\x08maskmaskMASK", 8))
 
 # close control frame
 s = io.BytesIO(b"\x88\x00")  # FRAME_CLOSE

tests/extmod/websocket_basic.py.exp

@@ -1,9 +1,14 @@
 b'ping'
-b'ping'
 b'\x81\x04pong'
+b'pingPi'
+b'ngPI'
+b'NG'
+b''
 b'pingpingpingpingpingpingpingpingpingpingpingpingpingpingpingpingpingpingpingpingpingpingpingpingpingpingpingpingpingpingpingping'
 b'\x81~\x00\x80pongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpong'
-b'\x00\x00\x00\x00'
+ioctl: EIO: True
+b'\x00\x00\x00\x00    '
+b'\x00\x00\x00\x00    '
 b''
 b'\x88\x00'
 b'ping'