204 lines
7.3 KiB
Racket
204 lines
7.3 KiB
Racket
#lang imperative-syndicate
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;; TCP/IP driver interface.
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;;
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;; A nice refinement would be to introduce something like a
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;; `(tcp-error id _)` assertion, for when something goes wrong
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;; listening or connecting. At present, for example, if connecting to
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;; some other host that isn't listening, the driver pretends the
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;; connection is open for an infinitesimal instant before closing.
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;; This would be nicer if it never signalled "open" at all, instead
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;; asserting something like `tcp-error` until interest in the
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;; connection goes away.
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;;
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;; TODO: This protocol is overly simplified.
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;; a) no flow control
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;; b) no facility for separate shutdown of inbound/outbound streams
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(provide (struct-out tcp-connection)
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(struct-out tcp-connection-peer)
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(struct-out tcp-accepted)
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(struct-out tcp-rejected)
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(struct-out tcp-out)
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(struct-out tcp-in)
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(struct-out tcp-in-line)
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(struct-out tcp-address)
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(struct-out tcp-listener))
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(define-logger syndicate/tcp)
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(require racket/exn)
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(require (prefix-in tcp: racket/tcp))
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(require (only-in racket/port read-bytes-avail!-evt))
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(require racket/unit)
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(require net/tcp-sig)
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(require net/tcp-unit)
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(require syndicate/support/bytes)
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Protocol messages
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(assertion-struct tcp-connection (id spec))
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(assertion-struct tcp-connection-peer (id addr))
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(assertion-struct tcp-accepted (id))
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(assertion-struct tcp-rejected (id exn))
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(message-struct tcp-out (id bytes))
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(message-struct tcp-in (id bytes))
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(message-struct tcp-in-line (id bytes))
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(assertion-struct tcp-address (host port))
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(assertion-struct tcp-listener (port))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Ground-level communication messages
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(message-struct raw-tcp-accepted (local-addr remote-addr cin cout))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Driver
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(spawn #:name 'drivers/tcp
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(during/spawn (observe (tcp-connection _ (tcp-listener $port)))
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#:name (list 'drivers/tcp 'listener port)
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(run-listener port))
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(during/spawn (tcp-connection $id (tcp-address $host $port))
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#:name (list 'drivers/tcp 'outbound id host port)
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(match (with-handlers ([exn:fail? (lambda (e) (list e))])
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(define-values (cin cout) (tcp:tcp-connect host port))
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(list cin cout))
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[(list e) (assert (tcp-rejected id e))]
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[(list cin cout)
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(assert (tcp-accepted id))
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(define unblock! (run-connection id cin cout))
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(unblock!)]))
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(during/spawn (observe (tcp-in-line $id _))
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#:name (list 'drivers/tcp 'line-reader id)
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(field [buffer #""])
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(on (message (tcp-in id $bs)) (buffer (bytes-append (buffer) bs)))
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(begin/dataflow
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(define newline-pos (bytes-index (buffer) (char->integer #\newline)))
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(when newline-pos
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(define line (subbytes (buffer) 0 newline-pos))
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(buffer (subbytes (buffer) (+ newline-pos 1)))
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(send! (tcp-in-line id line))))))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Listener
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(define (run-listener port)
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(define server-addr (tcp-listener port))
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(define listener (tcp:tcp-listen port 128 #t))
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(define control-ch (make-channel))
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(thread (lambda ()
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(let loop ((blocked? #t))
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(sync (handle-evt control-ch
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(match-lambda
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['unblock (loop #f)]
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['quit (void)]))
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(if blocked?
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never-evt
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(handle-evt (tcp:tcp-accept-evt listener)
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(lambda (cin+cout)
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(match-define (list cin cout) cin+cout)
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(define-values
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(local-hostname local-port remote-hostname remote-port)
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(tcp:tcp-addresses cin #t))
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(ground-send!
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(inbound
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(raw-tcp-accepted server-addr
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(tcp-address remote-hostname remote-port)
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cin
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cout)))
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(loop blocked?))))))
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(tcp:tcp-close listener)
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(signal-background-activity! -1)))
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(signal-background-activity! +1)
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(on-start (channel-put control-ch 'unblock))
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(on-stop (channel-put control-ch 'quit))
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(on (message (inbound (raw-tcp-accepted server-addr $remote-addr $cin $cout)))
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(define id (seal (list port remote-addr)))
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(spawn #:name (list 'drivers/tcp 'inbound id)
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(assert (tcp-connection id server-addr))
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(assert (tcp-connection-peer id remote-addr))
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(define unblock! (run-connection id cin cout))
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(on (asserted (tcp-accepted id)) (unblock!))
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(stop-when (asserted (tcp-rejected id _)))
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(stop-when (retracted (tcp-accepted id))))))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Connection
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(define (run-connection id cin cout)
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(define control-ch (make-channel))
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(thread (lambda () (connection-thread control-ch id cin)))
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(signal-background-activity! +1)
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(define (shutdown-connection!)
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(when control-ch
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(channel-put control-ch 'quit)
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(set! control-ch #f))
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(when cout
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(close-output-port cout)
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(set! cout #f)))
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(on-stop (shutdown-connection!))
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(on (message (inbound (tcp-in id $eof-or-bs)))
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(if (eof-object? eof-or-bs)
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(stop-current-facet)
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(send! (tcp-in id eof-or-bs))))
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(define-syntax-rule (trap-exns body ...)
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(with-handlers ([(lambda (e) (not (exn:break? e)))
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(lambda (e)
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(shutdown-connection!)
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(raise e))])
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body ...))
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(on (message (tcp-out id $bs))
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(trap-exns
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(if (string? bs)
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(write-string bs cout)
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(write-bytes bs cout))
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(flush-output cout)))
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(let ((unblocked? #f))
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(lambda ()
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(when (not unblocked?)
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(set! unblocked? #t)
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(when control-ch (channel-put control-ch 'unblock))))))
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(define (connection-thread control-ch id cin)
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(let loop ((blocked? #t))
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(sync (handle-evt control-ch
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(match-lambda
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['unblock (loop #f)]
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['quit (void)]))
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(if blocked?
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never-evt
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(handle-evt (read-bytes-avail-evt 32768 cin)
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(lambda (eof-or-bs)
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(ground-send! (inbound (tcp-in id eof-or-bs)))
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(loop (or blocked? (eof-object? eof-or-bs))))))))
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(close-input-port cin)
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(signal-background-activity! -1))
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(define (read-bytes-avail-evt len input-port)
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(guard-evt
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(lambda ()
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(let ([bstr (make-bytes len)])
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(handle-evt
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(read-bytes-avail!-evt bstr input-port)
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(lambda (v)
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(if (number? v)
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(if (= v len) bstr (subbytes bstr 0 v))
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v)))))))
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