peer: Re-instate _ack_state, use it for handling peer N(R)

Now its purpose makes sense!  Not part of the AX.25 2.0 spec, but it
seems to make more sense than the other variables for tracking this
point.

aioax25/peer.py

@@ -201,6 +201,12 @@ def __init__(
         self._recv_seq = 0
         self._recv_seq_name = "N(R)"
 
+        # ACK state number.
+        # Used to track the sequence number previously ACKed in an I or S
+        # frame N(R) field.
+        self._ack_state = 0  # AKA V(A)
+        self._ack_state_name = "V(A)"
+
         self._local_busy = False  # Local end busy, respond to
         # RR and I-frames with RNR.
         self._peer_busy = False  # Peer busy, await RR.
@@ -731,14 +737,14 @@ def _ack_outstanding(self, nr):
         """
         Receive all frames up to N(R)-1
         """
-        self._log.debug("%d through to %d are received", self._recv_seq, nr)
-        while self._recv_seq != nr:
+        self._log.debug("%d through to %d are received", self._ack_state, nr)
+        while self._ack_state != nr:
             if self._log.isEnabledFor(logging.DEBUG):
                 self._log.debug("Pending frames: %r", self._pending_iframes)
 
-            self._log.debug("ACKing N(R)=%s", self._recv_seq)
+            self._log.debug("ACKing N(R)=%s", self._ack_state)
             try:
-                frame = self._pending_iframes.pop(self._recv_seq)
+                frame = self._pending_iframes.pop(self._ack_state)
                 if self._log.isEnabledFor(logging.DEBUG):
                     self._log.debug(
                         "Popped %s off pending queue, N(R)s pending: %r",
@@ -749,12 +755,12 @@ def _ack_outstanding(self, nr):
                 if self._log.isEnabledFor(logging.DEBUG):
                     self._log.debug(
                         "ACK to unexpected N(R) number %s, pending: %r",
-                        self._recv_seq,
+                        self._ack_state,
                         self._pending_iframes,
                     )
             finally:
                 self._update_state(
-                    "_recv_seq", delta=1, comment="ACKed by peer N(R)"
+                    "_ack_state", delta=1, comment="ACKed by peer N(R)"
                 )
 
     def _on_receive_test(self, frame):
@@ -979,6 +985,7 @@ def _reset_connection_state(self):
         self._update_state("_send_seq", value=0, comment="reset")
         self._update_state("_recv_state", value=0, comment="reset")
         self._update_state("_recv_seq", value=0, comment="reset")
+        self._update_state("_ack_state", value=0, comment="reset")
 
         # Unacknowledged I-frames to be ACKed
         self._pending_iframes = {}

tests/test_peer/test_connection.py

@@ -1466,7 +1466,8 @@ def _update_state(prop, **kwargs):
         {"comment": "reset", "prop": "_send_seq", "value": 0},
         {"comment": "reset", "prop": "_recv_state", "value": 0},
         {"comment": "reset", "prop": "_recv_seq", "value": 0},
-        {"comment": "ACKed by peer N(R)", "delta": 1, "prop": "_recv_seq"},
+        {"comment": "reset", "prop": "_ack_state", "value": 0},
+        {"comment": "ACKed by peer N(R)", "delta": 1, "prop": "_ack_state"},
     ]
 
     # We should send a RNR in reply
@@ -1536,7 +1537,8 @@ def _update_state(prop, **kwargs):
         {"comment": "reset", "prop": "_send_seq", "value": 0},
         {"comment": "reset", "prop": "_recv_state", "value": 0},
         {"comment": "reset", "prop": "_recv_seq", "value": 0},
-        {"comment": "ACKed by peer N(R)", "delta": 1, "prop": "_recv_seq"},
+        {"comment": "reset", "prop": "_ack_state", "value": 0},
+        {"comment": "ACKed by peer N(R)", "delta": 1, "prop": "_ack_state"},
     ]
 
     # We should send a RR in reply
@@ -1606,8 +1608,9 @@ def _update_state(prop, **kwargs):
         {"comment": "reset", "prop": "_send_seq", "value": 0},
         {"comment": "reset", "prop": "_recv_state", "value": 0},
         {"comment": "reset", "prop": "_recv_seq", "value": 0},
+        {"comment": "reset", "prop": "_ack_state", "value": 0},
         # Peer ACK
-        {"comment": "ACKed by peer N(R)", "delta": 1, "prop": "_recv_seq"},
+        {"comment": "ACKed by peer N(R)", "delta": 1, "prop": "_ack_state"},
         # REJ handling
         {"comment": "from REJ N(R)", "prop": "_send_state", "value": 2},
     ]
@@ -2138,6 +2141,7 @@ def test_init_connection_mod8():
     peer._send_seq = 2
     peer._recv_state = 3
     peer._recv_seq = 4
+    peer._ack_state = 5
     peer._modulo = 6
     peer._max_outstanding = 7
     peer._IFrameClass = None
@@ -2164,6 +2168,7 @@ def test_init_connection_mod8():
     assert peer._send_seq == 0
     assert peer._recv_state == 0
     assert peer._recv_seq == 0
+    assert peer._ack_state == 0
     assert peer._pending_iframes == {}
     assert peer._pending_data == []
 
@@ -2187,6 +2192,7 @@ def test_init_connection_mod128():
     peer._send_seq = 2
     peer._recv_state = 3
     peer._recv_seq = 4
+    peer._ack_state = 5
     peer._modulo = 6
     peer._max_outstanding = 7
     peer._IFrameClass = None
@@ -2213,6 +2219,7 @@ def test_init_connection_mod128():
     assert peer._send_seq == 0
     assert peer._recv_state == 0
     assert peer._recv_seq == 0
+    assert peer._ack_state == 0
     assert peer._pending_iframes == {}
     assert peer._pending_data == []