From mboxrd@z Thu Jan  1 00:00:00 1970
Date: Tue, 26 Sep 1995 18:09:57 -0400
From: forsyth@plan9.cs.york.ac.uk forsyth@plan9.cs.york.ac.uk
Subject: seq_within
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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]