Read each request in full

read_request called recv once for the length and once for the body. A stream socket can deliver a request in several pieces, and the server then rejected that request.

The server now uses the read loop of the client, which moves to utilities as recv_exact. The server refuses a request above 64 KiB.

tests/test_server.py

@@ -253,6 +253,46 @@ class TestReadRequestErrors:
             srv.close()
             cli.close()
 
+    @pytest.mark.parametrize("split", [2, 10], ids=["inside-the-length", "inside-the-body"])
+    def test_request_in_two_pieces_is_read_whole(self, split):
+        """A stream socket can deliver one request in several pieces."""
+        srv, cli = socket_module.socketpair(socket_module.AF_UNIX, socket_module.SOCK_STREAM)
+        payload = json.dumps({"command": "GET", "client": "split"}).encode()
+        frame = struct.pack("!I", len(payload)) + payload
+        late = threading.Timer(0.05, cli.sendall, args=(frame[split:],))
+        try:
+            srv.settimeout(5)
+            cli.sendall(frame[:split])
+            late.start()
+            assert read_request(srv) == {"command": "GET", "client": "split"}
+        finally:
+            late.join()
+            srv.close()
+            cli.close()
+
+    def test_client_that_closes_after_half_a_request_is_an_error(self):
+        srv, cli = socket_module.socketpair(socket_module.AF_UNIX, socket_module.SOCK_STREAM)
+        payload = json.dumps({"command": "GET", "client": "half"}).encode()
+        try:
+            cli.sendall(struct.pack("!I", len(payload)) + payload[:10])
+            cli.close()
+            with pytest.raises(OSError, match="unable to read socket: socket closed after 10 of"):
+                read_request(srv)
+        finally:
+            srv.close()
+
+    def test_request_above_the_size_limit_is_refused(self):
+        """A wrong length prefix must not make the server wait for gigabytes."""
+        from bmspy.server import MAX_REQUEST_BYTES
+        srv, cli = socket_module.socketpair(socket_module.AF_UNIX, socket_module.SOCK_STREAM)
+        try:
+            cli.sendall(struct.pack("!I", MAX_REQUEST_BYTES + 1) + b"{}")
+            with pytest.raises(OSError, match="exceeds the limit"):
+                read_request(srv)
+        finally:
+            srv.close()
+            cli.close()
+
     def test_truncated_length_bytes_raises(self):
         srv, cli = socket_module.socketpair()
         try: