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Date: Tue, 9 Nov 2004 20:40:21 GMT
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From: Maxim Konovalov <maxim@FreeBSD.org>
Subject: Re: kern/73719: Page fault in bpf_mtap ()
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The following reply was made to PR kern/73719; it has been noted by GNATS.

From: Maxim Konovalov <maxim@FreeBSD.org>
To: Vladimir Ivanov <wawa@yandex-team.ru>
Cc: rwatson@FreeBSD.org, bug-followup@FreeBSD.org
Subject: Re: kern/73719: Page fault in bpf_mtap ()
Date: Tue, 9 Nov 2004 23:35:41 +0300 (MSK)

 On Tue, 9 Nov 2004, 20:10-0000, Vladimir Ivanov wrote:
 
 > The following reply was made to PR kern/73719; it has been noted by GNATS.
 >
 > From: Vladimir Ivanov <wawa@yandex-team.ru>
 > To: freebsd-gnats-submit@FreeBSD.org, wawa@yandex-team.ru
 > Cc:
 > Subject: Re: kern/73719: Page fault in bpf_mtap ()
 > Date: Tue, 09 Nov 2004 23:02:26 +0300
 >
 >  Ok,
 >  The bpf_mtap () seems to be little enough to make a look.
 >
 >  We suppose that most probable reason to panic is zero value of "bp" pointer.
 >  Also, I know that bpf open/close are frequent on my system.
 >  We can see (look at BPF_MTAP definition) that the value may be changed
 >  from another thread after verification but before bpf_mtap call because
 >  "ifp" points to global variable. The patch does not change the logic of
 >  program as you can see but garantee "bp" is not NULL. The only side
 >  effect is hypotetic pushing extra packet to just detached bpf device.
 >  It's not very big price I seem
 >
 >  I've commited the patch to the system and awaiting results.
 
 I can't believe this technique is a right way to fix things.
 
 Robert, is bpf(4) MP safe already?
 
 -- 
 Maxim Konovalov