Improvements from codewalk with Sam and Matthias
This commit is contained in:
Tony Garnock-Jones
parent
1058f0e96f
commit
9501a73fc5
203
new-server.rkt
203
new-server.rkt
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@ -14,6 +14,36 @@
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(define server-addr (tcp-listener 2322))
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(define (main)
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(ground-vm
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(transition 'no-state
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(spawn (timer-driver 'timer-driver))
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;; PAPER NOTE: remove #:debug-name for presentation economy
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(spawn tcp-driver #:debug-name 'tcp-driver)
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(spawn tcp-spy #:debug-name 'tcp-spy)
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(spawn listener))))
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(define listener
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(transition 'no-state
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(role 'connection-waiter (topic-subscriber (tcp-channel (wild) server-addr (wild))
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#:virtual? #t)
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#:state state
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#:topic t
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#:on-presence (match t
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[(topic 'publisher (tcp-channel remote-addr (== server-addr) _) #f)
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(transition state
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(spawn (session-vm server-addr remote-addr)
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#:debug-name (list 'ssh-session-vm remote-addr)))]
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;; PAPER NOTE: This second clause can be replaced with
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;; [_ state] for presentation economy
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[(topic 'publisher (tcp-channel remote-addr (== server-addr) _) #t)
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;; Ignore virtual flows. They just mean there's
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;; someone willing to supply connections to us
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;; at some point in the future.
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state]))))
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;;---------------------------------------------------------------------------
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(define (check-remote-identification! peer-identification-string)
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(define required-peer-identification-regex #rx"^SSH-2\\.0-.*")
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;; Each identification string is both a cleartext indicator that
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@ -88,105 +118,102 @@
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SSH_OPEN_UNKNOWN_CHANNEL_TYPE
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(bytes-append #"Unknown channel type " type))))))]))
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(define (connection-handler local-addr remote-addr)
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(define (spy marker)
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(role 'spy (or (topic-subscriber (wild) #:virtual? #t)
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(topic-publisher (wild) #:virtual? #t))
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#:state state
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[message
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(write `(,marker ,message))
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(newline)
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(flush-output)
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state]))
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(define (session-vm local-addr remote-addr)
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(define local-identification #"SSH-2.0-RacketSSH_0.0")
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(define (issue-identification-string)
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(at-meta-level
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(send-message (tcp-channel local-addr
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remote-addr
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(bytes-append local-identification #"\r\n")))))
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(define (read-handshake-and-become-reader)
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(transition 'handshake-is-stateless ;; but, crucially, the ssh-reader proper isn't!
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(at-meta-level
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(role 'socket-reader (topic-subscriber (tcp-channel remote-addr local-addr (wild)))
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#:state state
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[(tcp-channel _ _ (? eof-object?))
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(transition state (kill))]
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[(tcp-channel _ _ (? bytes? remote-identification))
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(check-remote-identification! remote-identification)
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;; First, set the incoming mode to bytes. Then
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;; initialise the reader, switching to packet-reading
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;; mode. Finally, spawn the remaining processes and
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;; issue the initial credit to the reader.
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(extend-transition
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(prefix-transition (ssh-reader local-addr remote-addr)
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(at-meta-level (send-tcp-mode remote-addr local-addr 'bytes)))
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(spawn/monitor (ssh-writer local-addr remote-addr) #:debug-name 'ssh-writer)
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;; Wait for a cycle to let the reader and writer get
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;; started, then tell the reader we are ready for a
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;; single packet and spawn the session manager.
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(yield #:state state
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(transition state
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(send-message (inbound-credit 1))
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(spawn/monitor (ssh-session local-identification
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remote-identification
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repl-boot
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'server)
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#:debug-name 'ssh-session))))]))))
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(define (exn->outbound-packet reason)
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(outbound-packet (ssh-msg-disconnect (exn:fail:contract:protocol-reason-code reason)
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(string->bytes/utf-8 (exn-message reason))
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#"")))
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(define (disconnect-message-required? reason)
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(and (exn:fail:contract:protocol? reason)
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(not (exn:fail:contract:protocol-originated-at-peer? reason))))
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(define (active-exception-handler reason)
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;; This is kind of gross: because the absence handler gets invoked
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;; several times in a row because of multiple flows intersecting
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;; this role, we have to be careful to make the transmission of
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;; the disconnection packet idempotent.
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;; TODO: this is likely no longer true now we're using monitors %%%
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(define interesting? (disconnect-message-required? reason))
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(transition inert-exception-handler
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(when interesting? (send-message (exn->outbound-packet reason)))
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(yield #:state state ;; gross
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(transition state (at-meta-level (kill #:reason (and interesting? reason)))))))
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(define (inert-exception-handler reason)
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inert-exception-handler)
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(nested-vm
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(list 'ssh-session-vm remote-addr)
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;; TODO: use (not-yet-existing) macro variant of nested-vm to avoid
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;; spuriously binding nested-boot-pid without blaming the wrong
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;; process in case of error.
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(lambda (nested-boot-pid)
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(transition 'running
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(transition 'no-state
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(spawn (timer-relay 'ssh-timer-relay) #:debug-name 'ssh-timer-relay)
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(spy 'SSH)
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;; Issue identification string.
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(at-meta-level
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(send-message (tcp-channel local-addr
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remote-addr
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(bytes-append local-identification #"\r\n"))))
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(issue-identification-string)
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;; Expect identification string, then update (!) our inbound
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;; subscription handler to switch to packet mode.
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(at-meta-level (send-tcp-mode remote-addr local-addr 'lines))
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(at-meta-level (send-tcp-credit remote-addr local-addr 1))
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(spawn/monitor
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(transition 'handshake-is-stateless
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(at-meta-level
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(role 'socket-reader (topic-subscriber (tcp-channel remote-addr local-addr (wild)))
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#:state state
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[(tcp-channel _ _ (? eof-object?))
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(transition state (kill))]
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[(tcp-channel _ _ (? bytes? remote-identification))
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(check-remote-identification! remote-identification)
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;; First, set the incoming mode to bytes. Then
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;; initialise the reader, switching to packet-reading
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;; mode. Finally, spawn the remaining processes and
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;; issue the initial credit to the reader.
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(extend-transition
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(prefix-transition (ssh-reader local-addr remote-addr)
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(at-meta-level (send-tcp-mode remote-addr local-addr 'bytes)))
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(spawn/monitor (ssh-writer local-addr remote-addr) #:debug-name 'ssh-writer)
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;; Wait for a cycle to let the reader and writer get
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;; started, then tell the reader we are ready for a
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;; single packet and spawn the session manager.
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(yield #:state state
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(transition state
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(send-message (inbound-credit 1))
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(spawn/monitor (ssh-session local-identification
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remote-identification
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repl-boot
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'server)
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#:debug-name 'ssh-session))))])))
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#:debug-name 'ssh-reader)
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(spawn/monitor (read-handshake-and-become-reader) #:debug-name 'ssh-reader)
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(role 'spy (or (topic-subscriber (wild) #:virtual? #t)
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(topic-publisher (wild) #:virtual? #t))
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#:state state
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[message
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(write `(SSH ,message))
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(newline)
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(flush-output)
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state])
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(spawn (transition active-exception-handler
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(role 'monitor-listener (topic-subscriber (monitor (wild) (wild)))
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#:state current-handler
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#:reason reason
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#:on-absence (current-handler reason))))))))
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(role 'monitor-listener (topic-subscriber (monitor (wild) (wild)))
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#:state state
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#:reason reason
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#:on-absence
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;; This is kind of gross: because the absence handler gets
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;; invoked several times in a row because of multiple flows
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;; intersecting this role, we have to be careful to make the
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;; transmission of the disconnection packet idempotent.
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;; TODO: this is likely no longer true now we're using monitors %%%
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(if (eq? state 'running)
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(if (and (exn:fail:contract:protocol? reason)
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(not (exn:fail:contract:protocol-originated-at-peer? reason)))
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(transition 'error-packet-sent
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(send-message (outbound-packet (ssh-msg-disconnect
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(exn:fail:contract:protocol-reason-code reason)
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(string->bytes/utf-8 (exn-message reason))
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#"")))
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(yield #:state state
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(transition state (at-meta-level (kill)))))
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(transition state (at-meta-level (kill #:reason reason))))
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state))))))
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(ground-vm
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(transition 'no-state
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(spawn (timer-driver 'timer-driver))
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(spawn tcp-driver #:debug-name 'tcp-driver)
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(spawn tcp-spy #:debug-name 'tcp-spy)
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(spawn (transition 'no-state
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(role 'connection-waiter (topic-subscriber (tcp-channel (wild) server-addr (wild))
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#:virtual? #t)
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#:state state
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#:topic t
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#:on-presence (match t
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[(topic 'publisher (tcp-channel remote-addr (== server-addr) _) #t)
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;; Ignore virtual flows. They just mean there's
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;; someone willing to supply connections to us
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;; at some point in the future.
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state]
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[(topic 'publisher (tcp-channel remote-addr (== server-addr) _) #f)
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(transition state
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(spawn (connection-handler server-addr remote-addr)
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#:debug-name (list 'ssh-session-vm remote-addr)))]))))))
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;; TODO: module+
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(main)
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