286 lines
12 KiB
Racket
286 lines
12 KiB
Racket
#lang racket/base
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;; TCP drivers, ported from os2.rkt directly
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(require racket/set)
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(require racket/match)
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(require (prefix-in tcp: racket/tcp))
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(require racket/port)
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(require "../sugar.rkt")
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(require "../support/dump-bytes.rkt")
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(require "../unify.rkt")
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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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(struct-out tcp-credit)
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(struct-out tcp-mode)
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send-tcp-credit
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send-tcp-mode
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tcp-driver
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tcp-spy)
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;; A TcpAddress is one of
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;; -- a (tcp-address String Uint16), representing a remote socket
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;; -- a (tcp-handle Any), representing a local socket on a kernel-assigned port
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;; -- a (tcp-listener Uint16), representing a local socket on a user-assigned port
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;; Note that tcp-handle-ids must be chosen carefully: they are scoped
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;; to the local VM, i.e. shared between processes in that VM, so
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;; processes must make sure not to accidentally clash in handle ID
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;; selection. They are also used in TcpChannel to mean a specific
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;; *instance* of a TCP connection, so if you are likely to want to
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;; reconnect individual flows, use different tcp-handle-ids.
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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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;; A TcpChannel is a (tcp-channel TcpAddress TcpAddress TcpSubPacket),
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;; and represents a section of a unidirectional TCP flow appearing on
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;; our local "subnet" of the full TCP network, complete with source,
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;; destination and subpacket.
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(struct tcp-channel (source destination subpacket) #:prefab)
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;; A TcpSubPacket is either
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;; -- a Bytes, representing a section of the data carried by a
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;; TcpChannel. In principle, this should also have a sequence
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;; number field, but for simplicity we rely on os2.rkt's
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;; preservation of ordering.
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;; -- an EndOfFile, representing the end of a the channel's stream.
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;; -- a (tcp-credit NonNegativeInteger), for flow control.
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;; -- a (tcp-mode TcpModeName), for mode selection.
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(struct tcp-credit (amount) #:prefab)
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(struct tcp-mode (name) #:prefab)
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;; A TcpModeName is either
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;; -- 'lines, for reading line-at-a-time, or
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;; -- 'bytes, for reading chunks of bytes.
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;; TODO: BUG?: Routing packets between two local sockets won't work
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;; because the patterns aren't set up to recognise that situation.
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;; A TcpConnectionState is a (tcp-connection-state TcpModeName
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;; Integer), representing the current input mode and issued credit.
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(struct tcp-connection-state (mode credit) #:prefab)
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;; TcpAddress TcpAddress NonNegativeInteger -> Preaction
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;; Sends a credit message on a channel using the correct (subscriber) role.
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(define (send-tcp-credit source-addr sink-addr amount)
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(send-feedback (tcp-channel source-addr sink-addr (tcp-credit amount))))
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;; TcpAddress TcpAddress TcpModeName -> Preaction
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;; Sends a mode selection message on a channel using the correct (subscriber) role.
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(define (send-tcp-mode source-addr sink-addr mode-name)
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(send-feedback (tcp-channel source-addr sink-addr (tcp-mode mode-name))))
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;; TcpAddresses; represents various wildcard addresses
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(define any-remote (tcp-address (wild) (wild)))
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(define any-handle (tcp-handle (wild)))
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(define any-listener (tcp-listener (wild)))
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;; Spawn
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;; Process acting as a TCP socket factory.
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(define (tcp-driver)
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(name-process 'tcp-driver
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(spawn
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(transition (set)
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(observe-publishers/everything (tcp-channel any-listener any-remote (wild))
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(match-state active-handles
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(match-conversation c
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(on-presence (maybe-spawn-socket 'publisher c active-handles #f tcp-listener-manager))
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(on-absence (maybe-forget-socket 'publisher c active-handles)))))
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(observe-subscribers/everything (tcp-channel any-remote any-listener (wild))
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(match-state active-handles
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(match-conversation c
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(on-presence (maybe-spawn-socket 'subscriber c active-handles #f tcp-listener-manager))
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(on-absence (maybe-forget-socket 'subscriber c active-handles)))))
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(observe-publishers (tcp-channel any-handle any-remote (wild))
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(match-state active-handles
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(match-conversation c
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(on-presence
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(maybe-spawn-socket 'publisher c active-handles #t tcp-connection-manager))
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(on-absence (maybe-forget-socket 'publisher c active-handles)))))
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(observe-subscribers (tcp-channel any-remote any-handle (wild))
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(match-state active-handles
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(match-conversation c
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(on-presence
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(maybe-spawn-socket 'subscriber c active-handles #t tcp-connection-manager))
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(on-absence (maybe-forget-socket 'subscriber c active-handles)))))))))
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;; Orientation Topic Set<HandleMapping> Boolean (TcpAddress TcpAddress -> BootK) -> Transition
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(define (maybe-spawn-socket orientation c active-handles remote-should-be-ground driver-fun)
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(match (list orientation c)
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[(or (list 'publisher (tcp-channel local-addr remote-addr _))
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(list 'subscriber (tcp-channel remote-addr local-addr _)))
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(cond
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[(not (eqv? remote-should-be-ground (ground? remote-addr))) (transition active-handles)]
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[(not (ground? local-addr)) (transition active-handles)]
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[(set-member? active-handles (cons local-addr remote-addr)) (transition active-handles)]
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[else
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(transition (set-add active-handles (cons local-addr remote-addr))
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(name-process (cons local-addr remote-addr)
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(spawn (driver-fun local-addr remote-addr))))])]))
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;; Orientation Topic Set<HandleMapping> -> Transition
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(define (maybe-forget-socket orientation c active-handles)
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(match (list orientation c)
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[(or (list 'publisher (tcp-channel local-addr remote-addr _))
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(list 'subscriber (tcp-channel remote-addr local-addr _)))
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(cond
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[(ground? remote-addr) (transition active-handles)]
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[(not (ground? local-addr)) (transition active-handles)]
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[else (transition (set-remove active-handles (cons local-addr remote-addr)))])]))
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;; TcpAddress TcpAddress -> Transition
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(define (tcp-listener-manager local-addr dummy-remote-addr)
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(match-define (tcp-listener port) local-addr)
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(define listener (tcp:tcp-listen port 4 #t))
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(define (handle-absence orientation c state)
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;; Hey, what if the presence we need went away between our manager
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;; spawning us, and us getting to this point? Presence being
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;; "edge-" rather than "level-triggered" means we'll hang around
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;; sadly forever, accepting connections to nowhere. TODO
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(match (list orientation c)
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[(or (list 'publisher (tcp-channel (== local-addr) remote-addr _))
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(list 'subscriber (tcp-channel remote-addr (== local-addr) _)))
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(if (ground? remote-addr)
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(transition state)
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(transition 'listener-is-closed
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(quit)
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(when (eq? state 'listener-is-running)
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(name-process (list 'tcp-listener-closer local-addr)
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(spawn (begin (tcp:tcp-close listener)
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(transition 'dummy (quit))))))))]))
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(transition 'listener-is-running
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(observe-publishers/everything (tcp-channel local-addr any-remote (wild))
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(match-state state
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(match-conversation c
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(on-absence (handle-absence 'publisher c state)))))
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(observe-subscribers/everything (tcp-channel any-remote local-addr (wild))
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(match-state state
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(match-conversation c
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(on-absence (handle-absence 'subscriber c state)))))
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(subscriber (cons (tcp:tcp-accept-evt listener) (wild))
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(on-message
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[(cons _ (list cin cout))
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(let-values (((local-hostname local-port remote-hostname remote-port)
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(tcp:tcp-addresses cin #t)))
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(define remote-addr (tcp-address remote-hostname remote-port))
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(name-process (cons local-addr remote-addr)
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(spawn (tcp-connection-manager* local-addr remote-addr cin cout))))]))))
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;; TcpAddress TcpAddress -> Transition
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(define (tcp-connection-manager local-addr remote-addr)
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(match-define (tcp-address remote-hostname remote-port) remote-addr)
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(define-values (cin cout) (tcp:tcp-connect remote-hostname remote-port))
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(tcp-connection-manager* local-addr remote-addr cin cout))
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;; TcpAddress TcpAddress InputPort OutputPort -> Transition
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;;
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;; Our process state here is a Maybe<TcpConnectionState>, representing
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;; a shutting-down state if #f.
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(define (tcp-connection-manager* local-addr remote-addr cin cout)
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(define (close-transition state send-eof?)
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(transition #f
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(when (not (eq? state #f))
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(list (when send-eof?
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(send-message (tcp-channel remote-addr local-addr eof)))
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(name-process (list 'tcp-connection-closer local-addr remote-addr)
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(spawn(begin (tcp:tcp-abandon-port cin)
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(tcp:tcp-abandon-port cout)
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(transition 'dummy (quit)))))))
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(quit)))
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(define (adjust-credit state amount)
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(let ((new-credit (+ (tcp-connection-state-credit state) amount)))
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(transition (struct-copy tcp-connection-state state [credit new-credit])
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(delete-endpoint 'inbound-relay)
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(when (positive? new-credit)
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(case (tcp-connection-state-mode state)
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[(lines)
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(name-endpoint 'inbound-relay
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(subscriber (cons (read-bytes-line-evt cin 'any) (wild))
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(match-state state
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(on-message
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[(cons _ (? eof-object?))
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(close-transition state #t)]
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[(cons _ (? bytes? bs))
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(sequence-actions (adjust-credit state -1)
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(send-message (tcp-channel remote-addr local-addr bs)))]))))]
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[(bytes)
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(name-endpoint 'inbound-relay
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(subscriber (cons (read-bytes-evt new-credit cin) (wild))
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(match-state state
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(on-message
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[(cons _ (? eof-object?))
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(close-transition state #t)]
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[(cons _ (? bytes? bs))
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(let ((len (bytes-length bs)))
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(sequence-actions (adjust-credit state (- len))
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(send-message
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(tcp-channel remote-addr local-addr bs))))]))))])))))
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(transition (tcp-connection-state 'bytes 0)
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(subscriber (cons (eof-evt cin) (wild))
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(match-state state
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(on-message
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[(cons (? evt?) _)
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(close-transition state #t)])))
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(subscriber (tcp-channel local-addr remote-addr (wild))
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(match-state state
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(on-absence (close-transition state #f))
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(on-message
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[(tcp-channel (== local-addr) (== remote-addr) subpacket)
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(match subpacket
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[(? eof-object?) (close-transition state #f)]
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[(? bytes? bs)
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(define len (bytes-length bs))
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(write-bytes bs cout)
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(flush-output cout)
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(transition state (send-tcp-credit local-addr remote-addr len))]
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[_
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(error 'tcp-connection-manager*
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"Publisher on a channel isn't supposed to issue channel control messages")])])))
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(publisher (tcp-channel remote-addr local-addr (wild))
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(match-state state
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(on-absence (close-transition state #f))
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(on-message
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[(tcp-channel (== remote-addr) (== local-addr) subpacket)
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(match subpacket
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[(tcp-credit amount)
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(if state (adjust-credit state amount) (transition state))]
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[(tcp-mode new-mode)
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;; Also resets credit to zero.
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(if state (adjust-credit (tcp-connection-state new-mode 0) 0) (transition state))]
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[_
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(error 'tcp-connection-manager*
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"Subscriber on a channel may only send channel control messages")])])))))
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;; Spawn
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;; Debugging aid: produces pretty hex dumps of TCP traffic sent on
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;; this network. Also prints out other messages without special
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;; formatting.
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(define (tcp-spy)
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(define (display-message m)
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(match m
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[(tcp-channel source dest (? bytes? body))
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(write `(TCPDATA ,source --> ,dest)) (newline)
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(dump-bytes! body (bytes-length body))
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(void)]
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[(tcp-channel source dest (? eof-object?))
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(write `(TCPEOF ,source --> ,dest)) (newline)
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(void)]
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[(tcp-channel source dest (tcp-credit amount))
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(write `(TCPCREDIT ,source --> ,dest ,amount)) (newline)
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(void)]
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[other
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(write `(TCPOTHER ,other)) (newline)
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(void)]))
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(name-process 'tcp-spy
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(spawn (transition 'no-state
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(observe-publishers (wild) (on-message [m (display-message m)]))
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(observe-subscribers (wild) (on-message [m (display-message m)]))))))
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