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Date:      Fri, 18 Jan 2002 16:46:18 -0800
From:      Skye Poier <skye@ffwd.cx>
To:        hackers@freebsd.org
Subject:   mbuf chains
Message-ID:  <20020118164617.L99893@ffwd.cx>

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What are the rules around mbuf chain construction?
(I've read man mbuf, doesnt go into much detail)

In particular, I'm assuming:
- all mbufs must be same type
- the head mbuf must have M_PKTHDR set
- the head mbuf.m_pkthdr.len must be the len of the entire chain
Anything to add?

My confusion is around splitting/concatenating -

When splitting an mbuf chain, the two resultant chains must be as above
(heads have M_PKTHDR and mbuf.m_pkthdr.len set) right?

When concatenating chains, what do you do with the M_PKTHDR that is now
in the middle of the chain?  m_cat doesn't seem very sophisticated in
this regard.  And of course update head mbuf.m_pkthdr.len

Thanks
Skye


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