From owner-freebsd-net@freebsd.org  Mon Aug 24 22:48:32 2015
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Date: Mon, 24 Aug 2015 18:48:31 -0400
Message-ID: <CACpH0Me_Nem9j30CdH=q4PUppKfFZegOuUQVxOR-1m4mdWXX9g@mail.gmail.com>
Subject: FreeBSD not properly padding vlan packets on several interface types.
From: Zaphod Beeblebrox <zbeeble@gmail.com>
To: FreeBSD Net <freebsd-net@freebsd.org>,
 FreeBSD Hackers <freebsd-hackers@freebsd.org>
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So, as background, the minimum packet size for ethernet packets is 64
bytes.  According to at least cisco, the minimum size, then, for 802.1q
(vlan, etc) packets is 68 bytes.  On at least BGE and BCE interfaces, it
seems (according to counters on my switch) that FreeBSD doesn't honour this.

"show interface counters error" is the cisco command to check.