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Date:      Wed, 21 Feb 2001 11:02:55 +0800
From:      Yusuf Goolamabbas <yusufg@outblaze.com>
To:        Luigi Rizzo <rizzo@aciri.org>
Cc:        jonny@jonny.eng.br, freebsd-net@FreeBSD.ORG, freebsd-stable@FreeBSD.ORG, phk@FreeBSD.ORG, dwmalone@FreeBSD.ORG
Subject:   Re: Solved: Bridging and dummynet seems to destroy dmesg output
Message-ID:  <20010221110255.A14313@outblaze.com>
In-Reply-To: <200102200330.f1K3UJC42482@iguana.aciri.org>; from rizzo@aciri.org on Mon, Feb 19, 2001 at 07:30:19PM -0800
References:  <20010220112154.A26373@outblaze.com> <200102200330.f1K3UJC42482@iguana.aciri.org>

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Luigi, PHK

In case you might not be on -stable

Thomas Moestl <tmoestl@gmx.net> just wrote a mesg to -stable trying to
explain "dmesg flakyness".

cut/paste from his message

Have you tried "dmesg -a"? It seems like the above message is from
syslog (if something is printed on into /dev/console, this is also
recorded in the message buffer). dmesg by default ignores messages
that are not from the kernel, but it cannot determine this if the first
characters of a line are missing. The missing characters get lost
when the oldest messages are partly overwritten by new ones (the
message buffer is a ring buffer).

> > Luigi, PHK
> > 
> > Any resolution on this ?
> 
> for sure there is no bug in ip_fw.c -- the change mentioned below just
> happens to change some symptoms but is no fix.
> 
> The message buffer is not "busted" as the report says, just has
> some NULs here and there that (probably) dmesg is not handling
> correctly. Poul, do you know more ?
> 
> 	cheers
> 	luigi
> 
> 
> > Regards, Yusuf
> > 
> > > Hi Yusuf,
> > > 
> > >     As described by cvsweb, the patches to IPFW did not change the behavior
> > > with log messages.  To be more exactly, either netinet/ip_fw.c either
> > > kern/subr_prf.c should be changed to match each other.  In my local setup I
> > > use a patch script after cvsup to fix ip_fw.c, removing all instances of
> > > "LOG_SECURITY |".
> > > 
> > >     Luigi/Poul, have you at least decided where the changes should be made? 
> > > There's no log(9) man page to decide which one is the correct syntax.  IMHO,
> > > -stable is not stable while this bug persists.
> > > 
> > > Yusuf Goolamabbas wrote:
> > > > 
> > > > Hi, I cvsupped today and got all of Luigi's commit [the one where he
> > > > does 1.16.2.13 of bridge.c alongwith a few others], I also have David
> > > > Malone's fix to syslogd.c [1.59.2.5]
> > > > 
> > > > If I don't have the following sysctl
> > > > 
> > > > net.inet.ip.fw.verbose_limit=10
> > > > 
> > > > then dmesg gets busted as mentioned earlier and if I do a sync;reboot
> > > > then I get a huge amount of ipfw messages scrolling on the console [It's
> > > > as if they were backlogged in some buffer somewhere] and after a few
> > > > seconds the syncing disk messages comes along
> > > > 
> > > > I have the following in my kernel config
> > > > 
> > > > options IPFIREWALL
> > > > options IPFIREWALL_DEFAULT_TO_ACCEPT
> > > > options BRIDGE
> > > > options DUMMYNET
> > > > 
> > > > my /etc/sysctl.conf is as follows
> > > > 
> > > > net.link.ether.bridge_ipfw=1
> > > > net.link.ether.bridge=1
> > > > net.inet.ip.fw.verbose=1
> > > > net.inet.ip.fw.verbose_limit=10
> > > > 
> > > > > Luigi Rizzo wrote:
> > > > > >
> > > > > > >     I tried only removing DUMMYNET from config, and the bug continues.  Should
> > > > > > > I try the changes below?
> > > > > >
> > > > > > no-they only affect dummynet. But this seems to suggest that
> > > > > > the problem is unrelated to my changes...
> > > > > >
> > > > > >         cheers
> > > > > >         luigi
> > > > >
> > > > > Hi,
> > > > >
> > > > >     I found the problem!
> > > > >
> > > > >     I started searching for the point where ipfw writes to the msgbuf, and
> > > > > like all other kernel modules, it uses the log(9) function.  But differently
> > > > > from the other modules, ip_fw.c uses a LOG_SECURITY argument.  I removed it,
> > > > > recompiled, reboot, and BINGO!  Probably the log(9) function does not expect a
> > > > > facility parameter, as it is assumed to be LOG_KERNEL.
> > > > >
> > > > >     Searching the cvsweb tree, I assume the changes that made it fail were
> > > > > made to kern/subr_prf.c, and not directly to netinet/ip_fw.c.  Probably a
> > > > > longer search should be made to detect if any other call to log(9) uses this
> > > > > approach.  (CC: to phk, who made the change to kern/subr_prf.c, 1.61.2.1, at
> > > > > 2000.01.16)
> > > > >
> > > > >     Hoping this is the final solution and waiting for the cvs commit, thanks
> > > > > to everybody,
> > > > >
> > > > >                                         Jonny
> > > > >
> > > > > --
> > > > > João Carlos Mendes Luís                 jonny@embratel.net.br
> > > > >   Networking Engineer                   jonny@jonny.eng.br
> > > > >  Internet via Embratel                        jcml@ieee.org
> > > > 
> > > > --
> > > > Yusuf Goolamabbas
> > > > yusufg@outblaze.com
> > > 
> > > -- 
> > > 
> > >                                         Jonny
> > > 
> > > -- 
> > > João Carlos Mendes Luís                 jonny@embratel.net.br
> > >   Networking Engineer                   jonny@jonny.eng.br
> > >  Internet via Embratel			jcml@ieee.org
> > 
> > -- 
> > Yusuf Goolamabbas
> > yusufg@outblaze.com
> > 
> 

-- 
Yusuf Goolamabbas
yusufg@outblaze.com

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