Rfc9293 WIP

net/tcp.lisp

@@ -1,14 +1,8 @@
 ;;; TCP
 ;;;
 ;;; Transmission Control Protocol - Protocol Specification
-;;; https://tools.ietf.org/html/rfc793
+;;; https://datatracker.ietf.org/doc/html/rfc9293
 ;;;
-;;; EFSM/SDL modeling of the original TCP standard (RFC793) and the
-;;; Congestion Control Mechanism of TCP Reno
-;;; http://www.medianet.kent.edu/techreports/TR2005-07-22-tcp-EFSM.pdf
-;;;
-;;; Computing TCP's Retransmission Timer
-;;; https://tools.ietf.org/html/rfc6298
 
 (in-package :mezzano.network.tcp)
 
@@ -383,8 +377,9 @@ Set to a value near 2^32 to test SND sequence number wrapping.")
              (setf (tcp-connection-last-ack-time connection)
                    (get-internal-run-time))
              (when (not *netmangler-force-local-retransmit*)
-               (tcp4-send-packet connection iss (+u32 irs 1) nil :ack-p t :syn-p t))))
+               (tcp4-send-packet connection iss (+u32 irs 1) nil :syn-p t))))
           ((logtest flags +tcp4-flag-rst+)) ; Do nothing for resets addressed to nobody.
+          ((logtest flags +tcp4-flag-fin+)) ; Do nothing for finish since the SEG.SEQ cannot be validated
           (t
            (let* ((seq (if (logtest flags +tcp4-flag-ack+)
                            (tcp-packet-acknowledgment-number packet start end)
@@ -471,11 +466,7 @@ Set to a value near 2^32 to test SND sequence number wrapping.")
   (when (<= seq (tcp-connection-rcv.nxt connection))
     ;; Don't check *netmangler-force-local-retransmit* here,
     ;; or no acks will ever get through.
-    (tcp4-send-packet connection
-                      (tcp-connection-snd.nxt connection)
-                      (tcp-connection-rcv.nxt connection)
-                      nil
-                      :ack-p t)))
+    (tcp4-send-ack connection)))
 
 (defun tcp-packet-sequence-number (packet start end)
   (declare (ignore end))
@@ -496,16 +487,15 @@ Set to a value near 2^32 to test SND sequence number wrapping.")
 (defun tcp-packet-data-length (packet start end)
   (- end (+ start (tcp-packet-header-length packet start end))))
 
-(defun acceptable-segment-p (connection packet start end)
+(defun acceptable-segment-p (connection seg.seq seg.len)
   (let ((rcv.wnd (tcp-connection-rcv.wnd connection))
-        (rcv.nxt (tcp-connection-rcv.nxt connection))
-        (seg.seq (tcp-packet-sequence-number packet start end))
-        (seg.len (tcp-packet-data-length packet start end)))
+        (rcv.nxt (tcp-connection-rcv.nxt connection)))
     (if (eql rcv.wnd 0)
         (and (eql seg.len 0)
              (eql seg.seq rcv.nxt))
         ;; Arithmetic here is not wrapping, so as to avoid wrap-around problems.
-        (and (and (<= rcv.nxt seg.seq) (< seg.seq (+ rcv.nxt rcv.wnd)))
+        (and (<= rcv.nxt seg.seq)
+             (< seg.seq (+ rcv.nxt rcv.wnd))
              (or (eql seg.len 0)
                  (let ((seq-end (+ seg.seq seg.len -1)))
                    (and (<= rcv.nxt seq-end) (< seq-end (+ rcv.nxt rcv.wnd)))))))))
@@ -593,7 +583,7 @@ Set to a value near 2^32 to test SND sequence number wrapping.")
                       (tcp-connection-rcv.nxt connection) (+u32 seq 1))
                 (when (not *netmangler-force-local-retransmit*)
                   (tcp4-send-packet connection ack (tcp-connection-rcv.nxt connection) nil
-                                    :ack-p t :syn-p t))
+                                    :syn-p t))
                 ;; Cancel retransmit
                 (disarm-retransmit-timer connection)
                 (disarm-timeout-timer connection))
@@ -632,13 +622,9 @@ Set to a value near 2^32 to test SND sequence number wrapping.")
                   (remhash connection (tcp-listener-pending-connections listener))
                   (decf (tcp-listener-n-pending-connections listener))))))
         (:established
-         (cond ((not (acceptable-segment-p connection packet start end))
+         (cond ((not (acceptable-segment-p connection seq data-length))
                 (when (not (logtest flags +tcp4-flag-rst+))
-                  (tcp4-send-packet connection
-                                    (tcp-connection-snd.nxt connection)
-                                    (tcp-connection-rcv.nxt connection)
-                                    nil
-                                    :ack-p t)))
+                  (tcp4-send-ack connection)))
                ((logtest flags +tcp4-flag-rst+)
                 (setf (tcp-connection-pending-error connection)
                       (make-condition 'connection-reset
@@ -652,7 +638,7 @@ Set to a value near 2^32 to test SND sequence number wrapping.")
                                       :port (tcp-connection-remote-port connection)))
                 (detach-tcp-connection connection)
                 (tcp4-send-packet connection
-                                  (tcp-connection-snd.next connection)
+                                  (tcp-connection-snd.nxt connection)
                                   0 ; ???
                                   nil
                                   :ack-p nil
@@ -700,7 +686,7 @@ Set to a value near 2^32 to test SND sequence number wrapping.")
                       (setf (mezzano.supervisor:event-state
                              (tcp-connection-receive-event connection))
                             t)
-                      (tcp4-send-packet connection ack (+u32 seq 1) nil :ack-p t))
+                      (tcp4-send-packet connection ack (+u32 seq 1) nil))
                     (tcp4-receive-data connection data-length end header-length packet seq start)))
                ((eql (tcp-connection-snd.una connection) ack)
                 ;; TODO: slow start/duplicate ack detection/fast retransmit/etc.
@@ -722,10 +708,7 @@ Set to a value near 2^32 to test SND sequence number wrapping.")
                (cond ((logtest flags +tcp4-flag-fin+)
                       (setf (tcp-connection-rcv.nxt connection)
                             (+u32 (tcp-connection-rcv.nxt connection) 1))
-                      (tcp4-send-packet connection
-                                        (tcp-connection-snd.nxt connection)
-                                        (tcp-connection-rcv.nxt connection)
-                                        nil)
+                      (tcp4-send-ack connection)
                       (if (logtest flags +tcp4-flag-ack+)
                           ;; Remote saw our FIN and closed as well.
                           (detach-tcp-connection connection)
@@ -743,10 +726,7 @@ Set to a value near 2^32 to test SND sequence number wrapping.")
                ;; Remote has sent FIN and waiting for ACK
                (setf (tcp-connection-rcv.nxt connection)
                      (+u32 (tcp-connection-rcv.nxt connection) 1))
-               (tcp4-send-packet connection
-                                 (tcp-connection-snd.nxt connection)
-                                 (tcp-connection-rcv.nxt connection)
-                                 nil)
+               (tcp4-send-ack connection)
                (detach-tcp-connection connection))
              (tcp4-receive-data connection data-length end header-length packet seq start)))
         (:closing
@@ -787,6 +767,12 @@ Set to a value near 2^32 to test SND sequence number wrapping.")
         (when errors-escape
           (error c))))))
 
+(defun tcp4-send-ack (connection)
+  (tcp4-send-packet connection
+                    (tcp-connection-snd.nxt connection)
+                    (tcp-connection-rcv.nxt connection)
+                    nil))
+
 (defun compute-ip-pseudo-header-partial-checksum (src-ip dst-ip protocol length)
   (+ (logand src-ip #xFFFF)
      (logand (ash src-ip -16) #xFFFF)