syndicate-lang
/
syndicate-2017
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Correct ack sequence number on RST responding to SYN (i.e. closed port)

This commit is contained in:
Tony Garnock-Jones 2014-06-20 00:15:31 -04:00
parent 6a3bafe082
commit b497004f0b
1 changed files with 8 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
tcp.rkt
View File

@ -490,8 +490,8 @@
transmit-check-interval-msec transmit-check-interval-msec
'relative))) 'relative)))
;; ConnState -> Transition ;; SeqNum SeqNum ConnState -> Transition
(define (reset seqn ackn is-fin? s) (define (reset seqn ackn s)
(log-warning "Sending RST from ~a:~a to ~a:~a" (log-warning "Sending RST from ~a:~a to ~a:~a"
(ip-address->hostname dst-ip) (ip-address->hostname dst-ip)
dst-port dst-port
@ -501,7 +501,7 @@
(list (list
(send (tcp-packet #f dst-ip dst-port src-ip src-port (send (tcp-packet #f dst-ip dst-port src-ip src-port
seqn seqn
(seq+ ackn (if is-fin? 1 0)) ackn
(set 'ack 'rst) (set 'ack 'rst)
0 0
#"" #""
@ -536,12 +536,14 @@
[else (transition new-s '())])] [else (transition new-s '())])]
[(message (tcp-packet #t _ _ _ _ seqn ackn flags window options data) _ _) [(message (tcp-packet #t _ _ _ _ seqn ackn flags window options data) _ _)
(define expected (next-expected-seqn s)) (define expected (next-expected-seqn s))
(define is-syn? (set-member? flags 'syn))
(define is-fin? (set-member? flags 'fin))
(if (and (not expected) ;; no syn yet (if (and (not expected) ;; no syn yet
(or (not (set-member? flags 'syn)) ;; and this isn't it (or (not is-syn?) ;; and this isn't it
(not (conn-state-listener-listening? s)))) ;; or it is, but no-one local cares (not (conn-state-listener-listening? s)))) ;; or it is, but no-one local cares
(reset ackn ;; this is *our* seqn (reset ackn ;; this is *our* seqn
seqn ;; this is what we should acknowledge... (seq+ seqn (+ (if is-syn? 1 0) (if is-fin? 1 0)))
(set-member? flags 'fin) ;; ... +1, if fin is set ;; ^^ this is what we should acknowledge...
s) s)
(sequence-transitions (cond (sequence-transitions (cond
[(not expected) ;; haven't seen syn yet, but we know this is it [(not expected) ;; haven't seen syn yet, but we know this is it