IsoTpMessage: extend timeout on first frame response (#1933)

* extend on first frame too

* debug/checks

* fix able to go from single to first to single etc forever

* more clean up

* more clean up

* comments!

python/uds.py

@@ -455,7 +455,8 @@ def recv(self, timeout=None) -> tuple[bytes | None, bool]:
         for msg in self._can_client.recv():
           frame_type = self._isotp_rx_next(msg)
           start_time = time.monotonic()
-          rx_in_progress = frame_type == ISOTP_FRAME_TYPE.CONSECUTIVE
+          # Anything that signifies we're building a response
+          rx_in_progress = frame_type in (ISOTP_FRAME_TYPE.FIRST, ISOTP_FRAME_TYPE.CONSECUTIVE)
           if self.tx_done and self.rx_done:
             return self.rx_dat, False
         # no timeout indicates non-blocking
@@ -473,6 +474,7 @@ def _isotp_rx_next(self, rx_data: bytes) -> ISOTP_FRAME_TYPE:
     # assert len(rx_data) == self.max_len, f"isotp - rx: invalid CAN frame length: {len(rx_data)}"
 
     if rx_data[0] >> 4 == ISOTP_FRAME_TYPE.SINGLE:
+      assert self.rx_dat == b"" or self.rx_done, "isotp - rx: single frame with active frame"
       self.rx_len = rx_data[0] & 0x0F
       assert self.rx_len < self.max_len, f"isotp - rx: invalid single frame length: {self.rx_len}"
       self.rx_dat = rx_data[1:1 + self.rx_len]
@@ -483,8 +485,11 @@ def _isotp_rx_next(self, rx_data: bytes) -> ISOTP_FRAME_TYPE:
       return ISOTP_FRAME_TYPE.SINGLE
 
     elif rx_data[0] >> 4 == ISOTP_FRAME_TYPE.FIRST:
+      # Once a first frame is received, further frames must be consecutive
+      assert self.rx_dat == b"" or self.rx_done, "isotp - rx: first frame with active frame"
       self.rx_len = ((rx_data[0] & 0x0F) << 8) + rx_data[1]
-      assert self.max_len <= self.rx_len, f"isotp - rx: invalid first frame length: {self.rx_len}"
+      assert self.rx_len >= self.max_len, f"isotp - rx: invalid first frame length: {self.rx_len}"
+      assert len(rx_data) == self.max_len, f"isotp - rx: invalid CAN frame length: {len(rx_data)}"
       self.rx_dat = rx_data[2:]
       self.rx_idx = 0
       self.rx_done = False