From owner-cvs-src@FreeBSD.ORG  Wed Mar 26 06:37:13 2003
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Date: Wed, 26 Mar 2003 06:37:13 -0800
From: Eivind Eklund <eivind@FreeBSD.org>
To: Maxime Henrion <mux@freebsd.org>
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Subject: Re: cvs commit: src/sys/conf options src/sys/netinet ip_output.c
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On Tue, Mar 25, 2003 at 11:20:16PM +0100, Maxime Henrion wrote:
> I think we should have some code like this before handing a packet to a
> network driver :
> 
> KASSERT(m0->m_pkthdr.len == m_length(m0, NULL), ("Bad packet header"));

This is a structure invariant check, and I'm strongly in favour of those -
however, I'd prefer if the logic for the invariant itself was located in
only one place.

Ie, define in a header (use of inline function instead of #define to avoid
problems with multiple evaluation of m):
static inline mbuf_invariant(struct mbuf *m) {
	return m->m.pkthdr.len == m_length(m, NULL);
}

then do
KASSERT(mbuf_invariant(m), ("Bad packet header");

Eivind.