update modbusrtuframer.

Co-authored-by: dlmoffett

pymodbus/framer/patched_rtuframer

@@ -0,0 +1,37 @@
+import logging
+
+from pymodbus.framer.rtu_framer import ModbusRtuFramer
+
+
+log = logging.getLogger(__name__)
+
+
+class PatchedModbusRtuFramer(ModbusRtuFramer):
+
+    def processIncomingPacket(self, data, callback, unit, **kwargs):
+        if not isinstance(unit, (list, tuple)):
+            unit = [unit]
+        self.addToFrame(data)
+        single = kwargs.get("single", False)
+        while True:
+            if not self.isFrameIntendedForUs(unit):
+                if self.advanceToNextOccurrenceOfUnit(unit) == 0:
+                    log.info(f"❌ Frame - [{data}] not intended for us, ignoring!!")
+                    break
+            elif self.isFrameReady():
+                if self.checkFrame():
+                    if self._validate_unit_id(unit, single):
+                        self._process(callback)
+                        log.info(f"✅ Frame - [{data}] responded to!!")
+                    else:
+                        header_txt = self._header["uid"]
+                        log.info(f"Not a valid unit id - {header_txt}, ignoring!!")
+                        self.resetFrame()
+                        break
+                else:
+                    log.info("Frame check failed, ignoring!!")
+                    if self.advanceToNextOccurrenceOfUnit(unit) == 0:
+                        break
+            else:
+                log.info(f"Frame - [{data}] not ready")
+                break

pymodbus/framer/rtu_framer.py

@@ -2,6 +2,7 @@
 # pylint: disable=missing-type-doc
 import struct
 import time
+from typing import List
 
 from pymodbus.exceptions import (
     InvalidMessageReceivedException,
@@ -87,6 +88,16 @@ def checkFrame(self):
         try:
             self.populateHeader()
             frame_size = self._header["len"]
+
+            if len(self._buffer) > frame_size:
+                # This means there are bytes *after* a valid frame intended to us.
+                # If there are bytes after that means we've probably de-sychronized
+                # and the master has considered us as having timed out and moved on.
+                # That or there is somehow a random sequence of bytes which looks like
+                # a real command to us and magically a crc.
+                # In either case, we must not respond.
+                return False
+
             data = self._buffer[: frame_size - 2]
             crc = self._header["crc"]
             crc_val = (int(crc[0]) << 8) + int(crc[1])
@@ -191,6 +202,24 @@ def populateResult(self, result):
         result.slave_id = self._header["uid"]
         result.transaction_id = self._header["uid"]
 
+    def isFrameIntendedForUs(self, slaves: List[int]):
+        """Check slave ID of frame."""
+        try:
+            return self._buffer[0] in slaves
+        except IndexError:
+            return True
+
+    def advanceToNextOccurrenceOfUnit(self, slaves: List[int]):
+        """Skip to next slave id."""
+        newbuf = b""
+        for i, databyte in enumerate(self._buffer):
+            if databyte in slaves and i > 0:
+                newbuf = self._buffer[i:]
+                break
+        self._buffer = newbuf
+        self._header = {"uid": 0x00, "len": 0, "crc": b"\x00\x00"}
+        return len(self._buffer)
+
     # ----------------------------------------------------------------------- #
     # Public Member Functions
     # ----------------------------------------------------------------------- #
@@ -331,6 +360,3 @@ def get_expected_response_length(self, data):
         func_code = int(data[1])
         pdu_class = self.decoder.lookupPduClass(func_code)
         return pdu_class.calculateRtuFrameSize(data)
-
-
-# __END__

test/test_client_multidrop.py

@@ -109,7 +109,6 @@ def test_wrapped_frame(self, framer, callback):
         # and the master moved on and queried another device
         callback.assert_not_called()
 
-    @pytest.mark.skip
     def test_frame_with_trailing_data(self, framer, callback):
         """Test trailing data."""
         garbage = b"\x05\x04\x03\x02\x01\x00"

test/test_framers.py

@@ -258,7 +258,7 @@ def test_populate_result(rtu_framer):  # pylint: disable=redefined-outer-name
             True,
             False,
         ),  # incorrect slave id
-        (b"\x11\x03\x06\xAE\x41\x56\x52\x43\x40\x49\xAD\x11\x03", 17, False, True),
+        (b"\x11\x03\x06\xAE\x41\x56\x52\x43\x40\x49\xAD\x11\x03", 17, True, False),
         # good frame + part of next frame
     ],
 )