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Date: Mon, 11 Dec 2000 01:48:37 -0800
From: Alfred Perlstein <bright@wintelcom.net>
To: bmilekic@freebsd.org
Cc: net@freebsd.org
Subject: Abusing m_ext for a worthy goal.
Message-ID: <20001211014837.W16205@fw.wintelcom.net>
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Ok, part of the mp cleanup got me looking at af_unix sockets.

Here's the deal, descriptors can be called "in-flight" meaning they
have been passed from one application to another via
CMG_DATA but not picked up on the other side yet.

The kernel does a bunch of hokey stuff to garbage collect them.

Instead of doing that I'd like to abuse MEXTADD to setup a callback
to remove the references automagicaly when the mbuf it free'd.

Here's the problem:

  I want to use the mbuf clusters, I don't want to use any special
  external storage.  I want my callback to free the cluster.

Any hints on how to do this?

here's what I have so far:

    MEXTADD(control, mtod(control, char *), control->m_len, unp_mbfree,
        cm, M_RDONLY, EXT_CMSG_DATA);

control is a mbuf with a cluster attached the has fd's written in it.
cm is a pointer to the mbuf cluster.

static void
unp_mbfree(caddr_t mm, void *claddr)
{
    struct mbuf *m = (struct mbuf *)mm;

    unp_scan(m, unp_discard);
    _MCLFREE(claddr);
}

does this look right?  would you like to abstract the mbuf
clusters further before i started using the _ macros?

--
-Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org]
"I have the heart of a child; I keep it in a jar on my desk."


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