Historical interest only: A Dataspace-like language and system that led to "Network Calculus" (ESOP 2014) and minimart-2014, in turn a predecessor to Syndicate. https://syndicate-lang.org/papers#gjthf-esop14
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#lang racket/base
;; TCP drivers, ported from os2.rkt directly
(require racket/set)
(require racket/match)
(require (prefix-in tcp: racket/tcp))
(require racket/port)
(require "../sugar.rkt")
(require "../support/dump-bytes.rkt")
(require "../unify.rkt")
(provide (struct-out tcp-address)
(struct-out tcp-handle)
(struct-out tcp-listener)
(struct-out tcp-channel)
(struct-out tcp-credit)
(struct-out tcp-mode)
;; A TcpAddress is one of
;; -- a (tcp-address String Uint16), representing a remote socket
;; -- a (tcp-handle Any), representing a local socket on a kernel-assigned port
;; -- a (tcp-listener Uint16), representing a local socket on a user-assigned port
;; Note that tcp-handle-ids must be chosen carefully: they are scoped
;; to the local VM, i.e. shared between processes in that VM, so
;; processes must make sure not to accidentally clash in handle ID
;; selection. They are also used in TcpChannel to mean a specific
;; *instance* of a TCP connection, so if you are likely to want to
;; reconnect individual flows, use different tcp-handle-ids.
(struct tcp-address (host port) #:prefab)
(struct tcp-handle (id) #:prefab)
(struct tcp-listener (port) #:prefab)
;; A TcpChannel is a (tcp-channel TcpAddress TcpAddress TcpSubPacket),
;; and represents a section of a unidirectional TCP flow appearing on
;; our local "subnet" of the full TCP network, complete with source,
;; destination and subpacket.
(struct tcp-channel (source destination subpacket) #:prefab)
;; A TcpSubPacket is either
;; -- a Bytes, representing a section of the data carried by a
;; TcpChannel. In principle, this should also have a sequence
;; number field, but for simplicity we rely on os2.rkt's
;; preservation of ordering.
;; -- an EndOfFile, representing the end of a the channel's stream.
;; -- a (tcp-credit NonNegativeInteger), for flow control.
;; -- a (tcp-mode TcpModeName), for mode selection.
(struct tcp-credit (amount) #:prefab)
(struct tcp-mode (name) #:prefab)
;; A TcpModeName is either
;; -- 'lines, for reading line-at-a-time, or
;; -- 'bytes, for reading chunks of bytes.
;; TODO: BUG?: Routing packets between two local sockets won't work
;; because the patterns aren't set up to recognise that situation.
;; A TcpConnectionState is a (tcp-connection-state TcpModeName
;; Integer), representing the current input mode and issued credit.
(struct tcp-connection-state (mode credit) #:prefab)
;; TcpAddress TcpAddress NonNegativeInteger -> Preaction
;; Sends a credit message on a channel using the correct (subscriber) role.
(define (send-tcp-credit source-addr sink-addr amount)
(send-feedback (tcp-channel source-addr sink-addr (tcp-credit amount))))
;; TcpAddress TcpAddress TcpModeName -> Preaction
;; Sends a mode selection message on a channel using the correct (subscriber) role.
(define (send-tcp-mode source-addr sink-addr mode-name)
(send-feedback (tcp-channel source-addr sink-addr (tcp-mode mode-name))))
;; TcpAddresses; represents various wildcard addresses
(define any-remote (tcp-address (wild) (wild)))
(define any-handle (tcp-handle (wild)))
(define any-listener (tcp-listener (wild)))
;; Spawn
;; Process acting as a TCP socket factory.
(define (tcp-driver)
(name-process 'tcp-driver
(transition (set)
(observe-publishers/everything (tcp-channel any-listener any-remote (wild))
(match-state active-handles
(match-conversation c
(on-presence (maybe-spawn-socket 'publisher c active-handles #f tcp-listener-manager))
(on-absence (maybe-forget-socket 'publisher c active-handles)))))
(observe-subscribers/everything (tcp-channel any-remote any-listener (wild))
(match-state active-handles
(match-conversation c
(on-presence (maybe-spawn-socket 'subscriber c active-handles #f tcp-listener-manager))
(on-absence (maybe-forget-socket 'subscriber c active-handles)))))
(observe-publishers (tcp-channel any-handle any-remote (wild))
(match-state active-handles
(match-conversation c
(maybe-spawn-socket 'publisher c active-handles #t tcp-connection-manager))
(on-absence (maybe-forget-socket 'publisher c active-handles)))))
(observe-subscribers (tcp-channel any-remote any-handle (wild))
(match-state active-handles
(match-conversation c
(maybe-spawn-socket 'subscriber c active-handles #t tcp-connection-manager))
(on-absence (maybe-forget-socket 'subscriber c active-handles)))))))))
;; Orientation Topic Set<HandleMapping> Boolean (TcpAddress TcpAddress -> BootK) -> Transition
(define (maybe-spawn-socket orientation c active-handles remote-should-be-ground driver-fun)
(match (list orientation c)
[(or (list 'publisher (tcp-channel local-addr remote-addr _))
(list 'subscriber (tcp-channel remote-addr local-addr _)))
[(not (eqv? remote-should-be-ground (ground? remote-addr))) (transition active-handles)]
[(not (ground? local-addr)) (transition active-handles)]
[(set-member? active-handles (cons local-addr remote-addr)) (transition active-handles)]
(transition (set-add active-handles (cons local-addr remote-addr))
(name-process (cons local-addr remote-addr)
(spawn (driver-fun local-addr remote-addr))))])]))
;; Orientation Topic Set<HandleMapping> -> Transition
(define (maybe-forget-socket orientation c active-handles)
(match (list orientation c)
[(or (list 'publisher (tcp-channel local-addr remote-addr _))
(list 'subscriber (tcp-channel remote-addr local-addr _)))
[(ground? remote-addr) (transition active-handles)]
[(not (ground? local-addr)) (transition active-handles)]
[else (transition (set-remove active-handles (cons local-addr remote-addr)))])]))
;; TcpAddress TcpAddress -> Transition
(define (tcp-listener-manager local-addr dummy-remote-addr)
(match-define (tcp-listener port) local-addr)
(define listener (tcp:tcp-listen port 4 #t))
(define (handle-absence orientation c state)
;; Hey, what if the presence we need went away between our manager
;; spawning us, and us getting to this point? Presence being
;; "edge-" rather than "level-triggered" means we'll hang around
;; sadly forever, accepting connections to nowhere. TODO
(match (list orientation c)
[(or (list 'publisher (tcp-channel (== local-addr) remote-addr _))
(list 'subscriber (tcp-channel remote-addr (== local-addr) _)))
(if (ground? remote-addr)
(transition state)
(transition 'listener-is-closed
(when (eq? state 'listener-is-running)
(name-process (list 'tcp-listener-closer local-addr)
(spawn (begin (tcp:tcp-close listener)
(transition 'dummy (quit))))))))]))
(transition 'listener-is-running
(observe-publishers/everything (tcp-channel local-addr any-remote (wild))
(match-state state
(match-conversation c
(on-absence (handle-absence 'publisher c state)))))
(observe-subscribers/everything (tcp-channel any-remote local-addr (wild))
(match-state state
(match-conversation c
(on-absence (handle-absence 'subscriber c state)))))
(subscriber (cons (tcp:tcp-accept-evt listener) (wild))
[(cons _ (list cin cout))
(let-values (((local-hostname local-port remote-hostname remote-port)
(tcp:tcp-addresses cin #t)))
(define remote-addr (tcp-address remote-hostname remote-port))
(name-process (cons local-addr remote-addr)
(spawn (tcp-connection-manager* local-addr remote-addr cin cout))))]))))
;; TcpAddress TcpAddress -> Transition
(define (tcp-connection-manager local-addr remote-addr)
(match-define (tcp-address remote-hostname remote-port) remote-addr)
(define-values (cin cout) (tcp:tcp-connect remote-hostname remote-port))
(tcp-connection-manager* local-addr remote-addr cin cout))
;; TcpAddress TcpAddress InputPort OutputPort -> Transition
;; Our process state here is a Maybe<TcpConnectionState>, representing
;; a shutting-down state if #f.
(define (tcp-connection-manager* local-addr remote-addr cin cout)
(define (close-transition state send-eof?)
(transition #f
(when (not (eq? state #f))
(list (when send-eof?
(send-message (tcp-channel remote-addr local-addr eof)))
(name-process (list 'tcp-connection-closer local-addr remote-addr)
(spawn(begin (tcp:tcp-abandon-port cin)
(tcp:tcp-abandon-port cout)
(transition 'dummy (quit)))))))
(define (adjust-credit state amount)
(let ((new-credit (+ (tcp-connection-state-credit state) amount)))
(transition (struct-copy tcp-connection-state state [credit new-credit])
(delete-endpoint 'inbound-relay)
(when (positive? new-credit)
(case (tcp-connection-state-mode state)
(name-endpoint 'inbound-relay
(subscriber (cons (read-bytes-line-evt cin 'any) (wild))
(match-state state
[(cons _ (? eof-object?))
(close-transition state #t)]
[(cons _ (? bytes? bs))
(sequence-actions (adjust-credit state -1)
(send-message (tcp-channel remote-addr local-addr bs)))]))))]
(name-endpoint 'inbound-relay
(subscriber (cons (read-bytes-evt new-credit cin) (wild))
(match-state state
[(cons _ (? eof-object?))
(close-transition state #t)]
[(cons _ (? bytes? bs))
(let ((len (bytes-length bs)))
(sequence-actions (adjust-credit state (- len))
(tcp-channel remote-addr local-addr bs))))]))))])))))
(transition (tcp-connection-state 'bytes 0)
(subscriber (cons (eof-evt cin) (wild))
(match-state state
[(cons (? evt?) _)
(close-transition state #t)])))
(subscriber (tcp-channel local-addr remote-addr (wild))
(match-state state
(on-absence (close-transition state #f))
[(tcp-channel (== local-addr) (== remote-addr) subpacket)
(match subpacket
[(? eof-object?) (close-transition state #f)]
[(? bytes? bs)
(define len (bytes-length bs))
(write-bytes bs cout)
(flush-output cout)
(transition state (send-tcp-credit local-addr remote-addr len))]
(error 'tcp-connection-manager*
"Publisher on a channel isn't supposed to issue channel control messages")])])))
(publisher (tcp-channel remote-addr local-addr (wild))
(match-state state
(on-absence (close-transition state #f))
[(tcp-channel (== remote-addr) (== local-addr) subpacket)
(match subpacket
[(tcp-credit amount)
(if state (adjust-credit state amount) (transition state))]
[(tcp-mode new-mode)
;; Also resets credit to zero.
(if state (adjust-credit (tcp-connection-state new-mode 0) 0) (transition state))]
(error 'tcp-connection-manager*
"Subscriber on a channel may only send channel control messages")])])))))
;; Spawn
;; Debugging aid: produces pretty hex dumps of TCP traffic sent on
;; this network. Also prints out other messages without special
;; formatting.
(define (tcp-spy)
(define (display-message m)
(match m
[(tcp-channel source dest (? bytes? body))
(write `(TCPDATA ,source --> ,dest)) (newline)
(dump-bytes! body (bytes-length body))
[(tcp-channel source dest (? eof-object?))
(write `(TCPEOF ,source --> ,dest)) (newline)
[(tcp-channel source dest (tcp-credit amount))
(write `(TCPCREDIT ,source --> ,dest ,amount)) (newline)
(write `(TCPOTHER ,other)) (newline)
(name-process 'tcp-spy
(spawn (transition 'no-state
(observe-publishers (wild) (on-message [m (display-message m)]))
(observe-subscribers (wild) (on-message [m (display-message m)]))))))