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Reask ARP questions periodically until we get answers or stop caring.

This commit is contained in:
Tony Garnock-Jones 2014-06-19 21:56:30 -04:00
parent 61c59250ee
commit 39b19ba624
1 changed files with 47 additions and 46 deletions
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93
arp.rkt
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@ -78,7 +78,7 @@
(cache-value-interface v)
(cache-value-address v)))))))
(define (build-packet s dest-mac ptype oper sender-ha sender-pa target-ha target-pa)
(define (build-packet dest-mac ptype oper sender-ha sender-pa target-ha target-pa)
(define hlen (bytes-length target-ha))
(define plen (bytes-length target-pa))
(define packet (bit-string->bytes
@ -118,12 +118,19 @@
(define sender-protocol-address (bit-string->bytes sender-protocol-address0))
(define sender-hardware-address (bit-string->bytes sender-hardware-address0))
(define target-protocol-address (bit-string->bytes target-protocol-address0))
;; (log-info "~a ARP Adding ~a = ~a to cache"
;; interface-name
;; (pretty-bytes sender-protocol-address)
;; (pretty-bytes sender-hardware-address))
(define learned-key (cache-key ptype sender-protocol-address))
(when (and (set-member? (state-queries s) learned-key) ;; it is relevant to our interests
(not (equal? sender-hardware-address
(cache-value-address (hash-ref (state-cache s)
learned-key
(lambda ()
(cache-value #f #f #f)))))))
(log-info "~a ARP Adding ~a = ~a to cache"
interface-name
(pretty-bytes sender-protocol-address)
(pretty-bytes sender-hardware-address)))
(define cache (hash-set (expire-cache (state-cache s))
(cache-key ptype sender-protocol-address)
learned-key
(cache-value (+ (current-inexact-milliseconds)
cache-entry-lifetime-msec)
interface
@ -135,8 +142,7 @@
[(1) ;; request
(if (set-member? (state-assertions s)
(cache-key ptype target-protocol-address))
(send (build-packet s
sender-hardware-address
(send (build-packet sender-hardware-address
ptype
2 ;; reply
hwaddr
@ -162,51 +168,19 @@
(cache-key ptype pa)))
(define (analyze-gestalt g s)
(define new-queries (gestalt->queries g))
(define new-assertions (gestalt->assertions g))
(define added-queries (set-subtract new-queries (state-queries s)))
(define added-assertions (set-subtract new-assertions (state-assertions s)))
(define unanswered-queries (set-subtract added-queries (list->set (hash-keys (state-cache s)))))
(define new-s (struct-copy state s [queries new-queries] [assertions new-assertions]))
(define (some-asserted-pa ptype)
(match (filter (lambda (k) (equal? (cache-key-protocol k) ptype))
(set->list new-assertions))
['() #f]
[(list* k _) (cache-key-address k)]))
;; (log-info "analyze-gestalt: g:\n~a" (gestalt->pretty-string g))
;; (log-info "analyze-gestalt: new-queries ~v" new-queries)
;; (log-info "analyze-gestalt: new-assertions ~v" new-assertions)
;; (log-info "analyze-gestalt: added-queries ~v" added-queries)
;; (log-info "analyze-gestalt: added-assertions ~v" added-assertions)
;; (log-info "analyze-gestalt: unanswered-queries ~v" unanswered-queries)
;; (log-info "analyze-gestalt: new-s ~v" new-s)
(define new-s (struct-copy state s [queries (gestalt->queries g)] [assertions new-assertions]))
(transition new-s
(list
(when (gestalt-empty? (gestalt-filter g (gestalt-for-supply interface-name)))
(quit))
(for/list [(q (in-set unanswered-queries))]
(define pa (some-asserted-pa (cache-key-protocol q)))
(log-info "~a ARP Asking for ~a from ~a"
interface-name
(pretty-bytes (cache-key-address q))
(and pa (pretty-bytes pa)))
(if pa
(send (build-packet new-s
broadcast-ethernet-address
(cache-key-protocol q)
1 ;; request
hwaddr
pa
zero-ethernet-address
(cache-key-address q)))
'()))
(for/list [(a (in-set added-assertions))]
(log-info "~a ARP Announcing ~a as ~a"
interface-name
(pretty-bytes (cache-key-address a))
(pretty-bytes hwaddr))
(send (build-packet new-s
broadcast-ethernet-address
(send (build-packet broadcast-ethernet-address
(cache-key-protocol a)
2 ;; reply -- gratuitous announcement
hwaddr
@ -214,20 +188,47 @@
hwaddr
(cache-key-address a)))))))
(define (send-questions s)
(define unanswered-queries
(set-subtract (state-queries s) (list->set (hash-keys (state-cache s)))))
(define (some-asserted-pa ptype)
(match (filter (lambda (k) (equal? (cache-key-protocol k) ptype))
(set->list (state-assertions s)))
['() #f]
[(list* k _) (cache-key-address k)]))
(transition s
(for/list [(q (in-set unanswered-queries))]
(define pa (some-asserted-pa (cache-key-protocol q)))
(log-info "~a ARP Asking for ~a from ~a"
interface-name
(pretty-bytes (cache-key-address q))
(and pa (pretty-bytes pa)))
(when pa
(send (build-packet broadcast-ethernet-address
(cache-key-protocol q)
1 ;; request
hwaddr
pa
zero-ethernet-address
(cache-key-address q)))))))
(list (set-wakeup-alarm)
(spawn (lambda (e s)
;; (log-info "ARP ~a ~a: ~v // ~v" interface-name (pretty-bytes hwaddr) e s)
(match e
[(routing-update g)
(analyze-gestalt g s)]
(sequence-transitions (analyze-gestalt g s)
send-questions)]
[(message (ethernet-packet _ _ source destination _ body) _ _)
(analyze-incoming-packet source destination body s)]
[(message (timer-expired _ _) _ _)
(define new-s (struct-copy state s
[cache (expire-cache (state-cache s))]))
(transition new-s
(list (set-wakeup-alarm)
(routing-update (compute-gestalt (state-cache new-s)))))]
(define new-g (compute-gestalt (state-cache new-s)))
(sequence-transitions (transition new-s
(list (set-wakeup-alarm)
(routing-update new-g)))
send-questions)]
[_ #f]))
(state (hash) (set) (set))
(compute-gestalt (hash)))))