Date: Wed, 30 Apr 2008 11:41:57 GMT From: Eugenio Maffione <eugenio.maffione@telecomitalia.it> To: freebsd-gnats-submit@FreeBSD.org Subject: kern/123255: mistake in ng_bpf manpage Message-ID: <200804301141.m3UBfvaK041105@www.freebsd.org> Resent-Message-ID: <200804301150.m3UBo153028396@freefall.freebsd.org>
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>Number: 123255
>Category: kern
>Synopsis: mistake in ng_bpf manpage
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: doc-bug
>Submitter-Id: current-users
>Arrival-Date: Wed Apr 30 11:50:01 UTC 2008
>Closed-Date:
>Last-Modified:
>Originator: Eugenio Maffione
>Release: 6.2
>Organization:
Telecomitalia
>Environment:
GENERIC!
>Description:
I'm writing to you because I think to have found a little mistake in the ng_bpf man page.
Actually the mistake is in the script proposed in the manpage.
I notice that in some cases the statement
printf " { code=%d jt=%d jf=%d k=%d }", \$1, \$2, \$3, \$4;
causes an incorrect programming of the bpf filter.
This happens when the "k" value exceed the MAX_INTEGER value as when, for example, the tcpdump expression refers a network where the the first octect is greater than 128.
In that case the awk generates a negative value for "k" and the bpf matches always (I don't understand why, but it happens).
>How-To-Repeat:
This happens when the "k" value exceed the MAX_INTEGER value as when, for example, the tcpdump expression refers a network where the the first octect is greater than 128. (e.g . PATTERN="udp and dst net 255.255.0.0/16")
>Fix:
I tried to change the printf statement changing the format for using a conversion to unsigned (%u) but the poor result is to have the absolute value of "k" (so just deleting the minus) [this probably is a problem in awk].
Finallly, I've found that the working one format for the printg in the manpage is " { code=%d jt=%d jf=%d k=%s }" that preserves the right unsigned integer values.
Hopefully this help some other novice...
>Release-Note:
>Audit-Trail:
>Unformatted:
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