424 lines
14 KiB
Racket
424 lines
14 KiB
Racket
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#lang racket/base
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(provide (struct-out tcp-address)
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(struct-out tcp-handle)
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(struct-out tcp-listener)
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(struct-out tcp-channel)
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spawn-tcp-driver)
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(require racket/set)
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(require racket/match)
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(require minimart)
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(require minimart/drivers/timer)
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(require minimart/demand-matcher)
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(require bitsyntax)
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(require "dump-bytes.rkt")
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(require "checksum.rkt")
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(require "ip.rkt")
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;; tcp-address/tcp-address : "kernel" tcp connection state machines
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;; tcp-handle/tcp-address : "user" outbound connections
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;; tcp-listener/tcp-address : "user" inbound connections
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(struct tcp-address (host port) #:prefab)
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(struct tcp-handle (id) #:prefab)
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(struct tcp-listener (port) #:prefab)
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(struct tcp-channel (source destination subpacket) #:prefab)
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(struct tcp-packet (from-wire?
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source-ip
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source-port
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destination-ip
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destination-port
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sequence-number
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ack-number
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flags
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window-size
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options
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data)
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#:prefab)
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(define PROTOCOL-TCP 6)
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(struct codec-state (active-state-vectors) #:transparent)
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(define (spawn-tcp-driver)
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(define (flip-statevec statevec)
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(match-define (list si sp di dp) statevec)
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(list di dp si sp))
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(define (state-vector-active? statevec s)
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(or (set-member? (codec-state-active-state-vectors s) statevec)
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(set-member? (codec-state-active-state-vectors s) (flip-statevec statevec))))
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(define (analyze-incoming-packet src-ip dst-ip body s)
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(bit-string-case body
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([ (src-port :: integer bytes 2)
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(dst-port :: integer bytes 2)
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(sequence-number :: integer bytes 4)
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(ack-number :: integer bytes 4)
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(data-offset :: integer bits 4)
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(reserved :: integer bits 3)
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(ns :: integer bits 1)
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(cwr :: integer bits 1)
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(ece :: integer bits 1)
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(urg :: integer bits 1)
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(ack :: integer bits 1)
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(psh :: integer bits 1)
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(rst :: integer bits 1)
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(syn :: integer bits 1)
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(fin :: integer bits 1)
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(window-size :: integer bytes 2)
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(checksum :: integer bytes 2) ;; TODO: check checksum
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(urgent-pointer :: integer bytes 2)
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(rest :: binary) ]
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(let* ((flags (set))
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(statevec (list src-ip src-port dst-ip dst-port))
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(old-active-state-vectors (codec-state-active-state-vectors s))
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(spawn-needed? (not (state-vector-active? statevec s))))
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(define-syntax-rule (set-flags! v ...)
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(begin (unless (zero? v) (set! flags (set-add flags 'v))) ...))
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(set-flags! ns cwr ece urg ack psh rst syn fin)
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(log-info "TCP ~a:~a -> ~a:~a (seq ~a, ack ~a, flags ~a, window ~a)"
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(ip-address->hostname src-ip)
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src-port
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(ip-address->hostname dst-ip)
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dst-port
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sequence-number
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ack-number
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flags
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window-size)
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(when spawn-needed? (log-info " - spawn needed!"))
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(bit-string-case rest
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([ (opts :: binary bytes (- (* data-offset 4) 20))
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(data :: binary) ]
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(let ((packet (tcp-packet #t
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src-ip
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src-port
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dst-ip
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dst-port
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sequence-number
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ack-number
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flags
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window-size
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(bit-string->bytes opts)
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(bit-string->bytes data))))
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(transition (if spawn-needed?
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(struct-copy codec-state s
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[active-state-vectors
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(set-add old-active-state-vectors statevec)])
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s)
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(list
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(when spawn-needed? (spawn-state-vector src-ip src-port
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dst-ip dst-port))
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;; TODO: get packet to the new state-vector process somehow
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(send packet)))))
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(else #f))))
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(else #f)))
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(define statevec-projection
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(compile-gestalt-projection
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(tcp-packet ? (?!) (?!) (?!) (?!) ? ? ? ? ? ?)))
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(define (analyze-gestalt g s)
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(define statevecs (matcher-key-set (gestalt-project g 0 0 #f statevec-projection)))
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(log-info "gestalt yielded statevecs ~v" statevecs)
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(transition (struct-copy codec-state s [active-state-vectors statevecs]) '()))
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(define (deliver-outbound-packet p s)
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(match-define (tcp-packet #f
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src-ip
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src-port
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dst-ip
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dst-port
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sequence-number
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ack-number
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flags
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window-size
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options
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data)
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p)
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(log-info "TCP ~a:~a -> ~a:~a (seq ~a, ack ~a, flags ~a, window ~a)"
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(ip-address->hostname src-ip)
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src-port
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(ip-address->hostname dst-ip)
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dst-port
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sequence-number
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ack-number
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flags
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window-size)
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(define (flag-bit sym) (if (set-member? flags sym) 1 0))
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(define payload (bit-string (src-port :: integer bytes 2)
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(dst-port :: integer bytes 2)
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(sequence-number :: integer bytes 4)
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(ack-number :: integer bytes 4)
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((+ 5 (quotient (bit-string-byte-count options) 4))
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:: integer bits 4) ;; TODO: enforce 4-byte alignment
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(0 :: integer bits 3)
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((flag-bit 'ns) :: integer bits 1)
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((flag-bit 'cwr) :: integer bits 1)
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((flag-bit 'ece) :: integer bits 1)
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((flag-bit 'urg) :: integer bits 1)
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((flag-bit 'ack) :: integer bits 1)
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((flag-bit 'psh) :: integer bits 1)
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((flag-bit 'rst) :: integer bits 1)
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((flag-bit 'syn) :: integer bits 1)
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((flag-bit 'fin) :: integer bits 1)
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(window-size :: integer bytes 2)
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(0 :: integer bytes 2) ;; checksum location
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(0 :: integer bytes 2) ;; TODO: urgent pointer
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(data :: binary)))
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(define pseudo-header (bit-string (src-ip :: binary bytes 4)
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(dst-ip :: binary bytes 4)
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0
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PROTOCOL-TCP
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((bit-string-byte-count payload) :: integer bytes 2)))
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(transition s (send (ip-packet src-ip dst-ip PROTOCOL-TCP #""
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(ip-checksum 16 payload #:pseudo-header pseudo-header)))))
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(spawn (lambda (e s)
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(match e
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[(routing-update g)
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(analyze-gestalt g s)]
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[(message (ip-packet src dst _ _ body) _ _)
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(analyze-incoming-packet src dst body s)]
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[(message (? tcp-packet? p) _ _)
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#:when (not (tcp-packet-from-wire? p))
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(deliver-outbound-packet p s)]
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[_ #f]))
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(codec-state (set))
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(gestalt-union (pub (ip-packet ? ? PROTOCOL-TCP ? ?))
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(sub (ip-packet ? ? PROTOCOL-TCP ? ?))
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(sub (tcp-packet #f ? ? ? ? ? ? ? ? ? ?))
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(pub (tcp-packet #t ? ? ? ? ? ? ? ? ? ?))
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(pub (tcp-packet #t ? ? ? ? ? ? ? ? ? ?)
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#:level 1))))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(struct buffer (data ;; bit-string
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seqn ;; names leftmost byte in data
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window ;; counts bytes from leftmost byte in data
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finished?) ;; boolean: true after FIN
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#:transparent)
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(struct conn-state (outbound ;; buffer
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inbound ;; buffer
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syn-acked? ;; boolean
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latest-activity-time) ;; from current-inexact-milliseconds
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#:transparent)
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(define transmit-check-interval-msec 100)
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(define inbound-buffer-limit 65535)
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(define maximum-segment-size 536) ;; bytes
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(define maximum-segment-lifetime-sec (* 2 60)) ;; two minutes; 2MSL is TIME-WAIT timeout
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(define (spawn-state-vector src-ip src-port dst-ip dst-port)
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(define src (tcp-address (ip-address->hostname src-ip) src-port))
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(define dst (tcp-address (ip-address->hostname dst-ip) dst-port))
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(define (timer-name kind) (list 'tcp-timer kind src dst))
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(define (next-expected-seqn s)
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(define b (conn-state-inbound s))
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(define v (buffer-seqn b))
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(and v (seq+ v (bit-string-byte-count (buffer-data b)))))
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(define (buffer-push b data)
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(struct-copy buffer b [data (bit-string-append (buffer-data b) data)]))
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;; ConnState -> ConnState
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(define (set-inbound-seqn seqn s)
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(struct-copy conn-state s
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[inbound (struct-copy buffer (conn-state-inbound s) [seqn seqn])]))
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;; Bitstring ConnState -> Transition
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(define (incorporate-segment data s)
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(transition
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(if (buffer-finished? (conn-state-inbound s))
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s
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(struct-copy conn-state s [inbound (buffer-push (conn-state-inbound s) data)]))
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'()))
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(define (seq+ a b) (bitwise-and #xffffffff (+ a b)))
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;; Always positive
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(define (seq- larger smaller)
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(if (< larger smaller) ;; wraparound has occurred
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(+ (- larger smaller) #x100000000)
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(- larger smaller)))
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(define (seq> a b)
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(< (seq- a b) #x80000000))
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;; ConnState -> Transition
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(define (deliver-inbound-locally s)
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(define b (conn-state-inbound s))
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(if (bit-string-empty? (buffer-data b))
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(transition s '())
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(let ((chunk (bit-string->bytes (buffer-data b))))
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(transition (struct-copy conn-state s
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[inbound (struct-copy buffer b
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[data #""]
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[seqn (seq+ (buffer-seqn b) (bytes-length chunk))])])
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(send (tcp-channel src dst chunk))))))
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;; (Setof Symbol) -> ConnState -> Transition
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(define ((check-fin flags) s)
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(define b (conn-state-inbound s))
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(unless (bit-string-empty? (buffer-data b)) ;; assured by deliver-inbound-locally
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(error 'check-fin "Nonempty inbound buffer"))
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(transition
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(if (set-member? flags 'fin)
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(struct-copy conn-state s
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[inbound (struct-copy buffer b
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[seqn (seq+ (buffer-seqn b) 1)] ;; reliable: count fin as a byte
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[finished? #t])])
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s)
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'()))
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;; Boolean Nat -> ConnState -> Transition
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(define ((discard-acknowledged-outbound ack? ackn) s)
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(transition
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(if (not ack?)
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s
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(let* ((b (conn-state-outbound s))
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(limit (seq+ (buffer-seqn b) (bit-string-byte-count (buffer-data b))))
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(ackn (if (seq> ackn limit) limit ackn))
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(dist (seq- ackn (buffer-seqn b))))
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(define-values (discarded-acknowledged-data remaining-data)
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(bit-string-split-at (buffer-data b) (* dist 8))) ;; bit offset!
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(struct-copy conn-state s
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[outbound (struct-copy buffer b [data remaining-data] [seqn ackn])]
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[syn-acked? (or (conn-state-syn-acked? s)
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(positive? dist))])))
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'()))
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;; Nat -> ConnState -> Transition
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(define ((update-outbound-window peer-window) s)
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(transition (struct-copy conn-state s
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[outbound (struct-copy buffer (conn-state-outbound s)
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[window peer-window])])
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'()))
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;; ConnState -> Boolean
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(define (all-output-acknowledged? s)
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(bit-string-empty? (buffer-data (conn-state-outbound s))))
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;; ConnState -> Transition
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(define ((send-outbound old-ackn) s)
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(define b (conn-state-outbound s))
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(define pending-byte-count (max 0 (- (bit-string-byte-count (buffer-data b))
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(if (buffer-finished? b) 1 0))))
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(define segment-size (min maximum-segment-size
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(buffer-window b)
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pending-byte-count))
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(define segment-offset (if (conn-state-syn-acked? s) 0 1))
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(define-values (chunk0 remaining-data)
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(bit-string-split-at (buffer-data b) (* segment-size 8))) ;; bit offset!
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(define-values (discarded-dummy-syn-data chunk)
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(bit-string-split-at chunk0 (* segment-offset 8))) ;; bit offset!
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(define ackn (next-expected-seqn s))
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(define flags (set))
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(when ackn
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(set! flags (set-add flags 'ack)))
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(when (not (conn-state-syn-acked? s))
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(set! flags (set-add flags 'syn)))
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(when (and (buffer-finished? b)
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(= segment-size pending-byte-count)
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(not (all-output-acknowledged? s)))
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(set! flags (set-add flags 'fin)))
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(define window (min 65535 ;; limit of field width
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(max 0 ;; can't be negative
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(- (buffer-window (conn-state-inbound s))
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(bit-string-byte-count
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(buffer-data (conn-state-inbound s)))))))
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(transition s
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(unless (and (equal? ackn old-ackn)
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(conn-state-syn-acked? s)
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(zero? (bit-string-byte-count chunk)))
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(send (tcp-packet #f
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dst-ip
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dst-port
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src-ip
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src-port
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(buffer-seqn b)
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(or ackn 0)
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flags
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window
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#""
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chunk)))))
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;; ConnState -> Transition
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(define (bump-activity-time s)
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(transition (struct-copy conn-state s
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[latest-activity-time (current-inexact-milliseconds)])
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'()))
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;; ConnState -> Transition
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(define (quit-when-done s)
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(if (and (buffer-finished? (conn-state-outbound s))
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(buffer-finished? (conn-state-inbound s))
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(all-output-acknowledged? s)
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(> (- (current-inexact-milliseconds) (conn-state-latest-activity-time s))
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(* 2 1000 maximum-segment-lifetime-sec)))
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(transition s (quit))
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(transition s '())))
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;; Action
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(define send-set-transmit-check-timer
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(send (set-timer (timer-name 'transmit-check)
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transmit-check-interval-msec
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'relative)))
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(define (state-vector-behavior e s)
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(define old-ackn (buffer-seqn (conn-state-inbound s)))
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(match e
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[(message (tcp-packet #t _ _ _ _ seqn ackn flags window options data) _ _)
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(define expected (next-expected-seqn s))
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(sequence-transitions (if (not expected) ;; haven't seen syn yet...
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(if (set-member? flags 'syn) ;; ... and this is it
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(incorporate-segment data
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(set-inbound-seqn (seq+ seqn 1) s))
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(transition s '()))
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(if (= expected seqn)
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(incorporate-segment data s)
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(transition s '())))
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deliver-inbound-locally
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(check-fin flags)
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(discard-acknowledged-outbound (set-member? flags 'ack) ackn)
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(update-outbound-window window)
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(send-outbound old-ackn)
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bump-activity-time
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quit-when-done)]
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[(message (timer-expired (== (timer-name 'transmit-check)) _) _ _)
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(sequence-transitions (transition s send-set-transmit-check-timer)
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(send-outbound old-ackn)
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quit-when-done)]
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[_ #f]))
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;; (local-require racket/trace)
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;; (trace state-vector-behavior)
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(define initial-outbound-seqn
|
||
|
;; Yuck
|
||
|
(inexact->exact (truncate (* #x100000000 (random)))))
|
||
|
|
||
|
;; TODO accept input from user process
|
||
|
;; TODO append a dummy byte at FIN position in outbound buffer
|
||
|
(list
|
||
|
send-set-transmit-check-timer
|
||
|
(spawn state-vector-behavior
|
||
|
(conn-state (buffer #"!" initial-outbound-seqn 0 #f) ;; dummy data at SYN position
|
||
|
(buffer #"" #f inbound-buffer-limit #f)
|
||
|
#f
|
||
|
(current-inexact-milliseconds))
|
||
|
(gestalt-union (sub (timer-expired (timer-name ?) ?))
|
||
|
(sub (tcp-packet #t src-ip src-port dst-ip dst-port ? ? ? ? ? ?))
|
||
|
(pub (tcp-packet #f dst-ip dst-port src-ip src-port ? ? ? ? ? ?))
|
||
|
(sub (tcp-channel dst src ?))
|
||
|
(pub (tcp-channel src dst ?))))))
|