extmod/modwebsocket: Fix websocket to send correct close frame.

When the websocket closes currently, it does not send a proper
"close"-frame, but rather encodes the 0x8800-sequence inside a binary
packet, which is wrong.  The close packet is a different kind of websocket
frame, according to https://www.rfc-editor.org/rfc/rfc6455.

This change resolves an error in Firefox when the websocket closes.

Signed-off-by: Felix Dörre <felix@dogcraft.de>

extmod/modwebsocket.c

@@ -56,6 +56,7 @@ typedef struct _mp_obj_websocket_t {
 } mp_obj_websocket_t;
 
 STATIC mp_uint_t websocket_write(mp_obj_t self_in, const void *buf, mp_uint_t size, int *errcode);
+STATIC mp_uint_t websocket_write_raw(mp_obj_t self_in, const byte *header, int hdr_sz, const void *buf, mp_uint_t size, int *errcode);
 
 STATIC mp_obj_t websocket_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
     mp_arg_check_num(n_args, n_kw, 1, 2, false);
@@ -193,9 +194,9 @@ STATIC mp_uint_t websocket_read(mp_obj_t self_in, void *buf, mp_uint_t size, int
                     if (last_state == CONTROL) {
                         byte frame_type = self->last_flags & FRAME_OPCODE_MASK;
                         if (frame_type == FRAME_CLOSE) {
-                            static const char close_resp[2] = {0x88, 0};
+                            static const byte close_resp[2] = {0x88, 0};
                             int err;
-                            websocket_write(self_in, close_resp, sizeof(close_resp), &err);
+                            websocket_write_raw(self_in, close_resp, sizeof(close_resp), close_resp, 0, &err);
                             return 0;
                         }
 
@@ -230,6 +231,11 @@ STATIC mp_uint_t websocket_write(mp_obj_t self_in, const void *buf, mp_uint_t si
         hdr_sz = 4;
     }
 
+    return websocket_write_raw(self_in, header, hdr_sz, buf, size, errcode);
+}
+STATIC mp_uint_t websocket_write_raw(mp_obj_t self_in, const byte *header, int hdr_sz, const void *buf, mp_uint_t size, int *errcode) {
+    mp_obj_websocket_t *self = MP_OBJ_TO_PTR(self_in);
+
     mp_obj_t dest[3];
     if (self->opts & BLOCKING_WRITE) {
         mp_load_method(self->sock, MP_QSTR_setblocking, dest);

tests/extmod/websocket_basic.py.exp

@@ -5,7 +5,7 @@ b'pingpingpingpingpingpingpingpingpingpingpingpingpingpingpingpingpingpingpingpi
 b'\x81~\x00\x80pongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpongpong'
 b'\x00\x00\x00\x00'
 b''
-b'\x81\x02\x88\x00'
+b'\x88\x00'
 b'ping'
 b'pong'
 0