From: forsyth@plan9.cs.york.ac.uk forsyth@plan9.cs.york.ac.uk
Subject: seq_within
Date: Tue, 26 Sep 1995 18:09:57 -0400 [thread overview]
Message-ID: <19950926220957.35haFcNhFuo0-Zf4MTME9GnIu-U2JneyKb_zLdvRL4k@z> (raw)
does anyone else think the definition of seq_within in /sys/src/9/port/tcpinput.c
is wrong? i think the test when low > high should be
if(x >= low || x <= high)
not
if(low >= x && x >= high)
i think as it stands it is checking the wrong interval. consider its application in
seq_within(seg.ack, tcb->snd.una+1, tcb->snd.nxt)
tcb->snd.una+1 > tcb->snd.nxt when the sequence numbers have wrapped round zero,
increasing from tcb->snd.una+1 past ~0 to 0 then on to tcb->snd.nxt.
in other words, the valid ack sequence numbers are those in
[tcb->snd.una+1, ~0] ∪ [0, tcb->snd.nxt]
not (as seq_within currently has it) those in
[tcb->snd.nxt, tcb->snd.una+1]
next reply other threads:[~1995-09-26 22:09 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
1995-09-26 22:09 forsyth [this message]
1995-09-27 15:51 seq_within Michael
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