From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mike Haertel <mike@ducky.net>
Message-Id: <200111011857.fA1Iv9701688@ducky.net>
To: 9fans@cse.psu.edu
Subject: [9fans] authentication protocol question
Date: Thu,  1 Nov 2001 10:57:09 -0800
Topicbox-Message-UUID: 11b12c16-eaca-11e9-9e20-41e7f4b1d025

I am puzzled by the following code in /sys/src/fs/port/auth.c.

	/*
	 *  the id must be in a valid range.  the range is specified by a
	 *  lower bount (idoffset) and a bit vector (idvec) where a
	 *  bit set to 1 means unusable
	 */
	lock(&cp->idlock);
	x = a.id - cp->idoffset;
	bit = 1<<x;
	if(x < 0 || x > 31 || (bit&cp->idvec)){
		unlock(&cp->idlock);
print("id out of range: idoff %ld idvec %lux id %ld\n", cp->idoffset, cp->idvec, a.id);
		return 0;
	}
	cp->idvec |= bit;

 From the auth(6) man page, I had the impression that the id
field was supposed to be a simple sequence number.  Is there a
race in some client in which the order of the sequence numbers
can get rearranged?  What is the race?