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Date:      Sat, 9 Oct 2004 00:34:34 +0400
From:      Gleb Smirnoff <glebius@freebsd.org>
To:        Giorgos Keramidas <keramida@freebsd.org>
Cc:        freebsd-net@freebsd.org
Subject:   Re: Calling m_pullup in ether_input
Message-ID:  <20041008203434.GA2770@cell.sick.ru>
In-Reply-To: <20041008151515.GA3136@orion.daedalusnetworks.priv>
References:  <20041008151515.GA3136@orion.daedalusnetworks.priv>

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On Fri, Oct 08, 2004 at 06:15:15PM +0300, Giorgos Keramidas wrote:
G> In ether_input() we unconditionaly discard the mbufs whose m_len is less than
G> ETHER_HDR_LEN.  A bit higher M_PKTHDR has been checked but the check made
G> before discarding the frame doesn't pay attention to the m->m_pkthdr.len (the
G> total packet length).

In my humble opinion, all Ethernet device drivers are intentionally written
in such a way that they always pass an mbuf with contigous Ethernet header
to ether_input().

Why did you write this patch? Do you really have packet loss?

G> I am trying to find out how often this happens, by using the attached patch to
G> count the number of small frames received in ether_input() and the number of
G> failed m_pullup() attempts that result from that.

And what results do you have?

G> Does this change seem reasonable as an instrumentation  of the particular
G> problem or am I unknowingly breaking something in the way ether_input() is
G> supposed to work?

AFAIK, this patch does not break anything but just adds more processing.

-- 
Totus tuus, Glebius.
GLEBIUS-RIPN GLEB-RIPE



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