From owner-freebsd-net  Sun Jul  9 14: 4:49 2000
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Date: Sun, 9 Jul 2000 14:04:41 -0700
From: Alfred Perlstein <bright@wintelcom.net>
To: net@freebsd.org
Subject: weird things with M_EXT and large packets
Message-ID: <20000709140441.T25571@fw.wintelcom.net>
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I have some code here sending a mbuf via:

error = (*so->so_proto->pr_usrreqs->pru_send)(so, 0, m, 0, 0, p);

m is setup like so:

    m->m_ext.ext_free = kblob_mbuf_free;
    m->m_ext.ext_ref = kblob_mbuf_ref;
    m->m_ext.ext_buf = (void *)kb;
    m->m_ext.ext_size = kb->kb_len;
    m->m_data = (char *) kb->kb_data + uap->offset;
    m->m_flags |= M_EXT;
    m->m_pkthdr.len = m->m_len = uap->nbytes;

uap->nbytes is 59499.

It looks like the packet is being broken up or referenced to be sent,
but at a certain point it hangs.

this is a sort of trace going on:

kblob_mbuf_ref: size = 59499
kblob_mbuf_free: size = 59499
deref, id = 0, refcnt = 2
kblob_mbuf_ref: size = 59499
kblob_mbuf_ref: size = 59499
kblob_mbuf_ref: size = 59499
kblob_mbuf_free: size = 59499
deref, id = 0, refcnt = 4
kblob_mbuf_free: size = 59499
deref, id = 0, refcnt = 3
kblob_mbuf_free: size = 59499
deref, id = 0, refcnt = 2
kblob_mbuf_ref: size = 59499
kblob_mbuf_free: size = 59499
deref, id = 0, refcnt = 2
kblob_mbuf_ref: size = 59499
kblob_mbuf_ref: size = 59499
kblob_mbuf_ref: size = 59499
kblob_mbuf_free: size = 59499
deref, id = 0, refcnt = 4
kblob_mbuf_free: size = 59499
deref, id = 0, refcnt = 3
kblob_mbuf_free: size = 59499
deref, id = 0, refcnt = 2
kblob_mbuf_ref: size = 59499
kblob_mbuf_free: size = 59499
deref, id = 0, refcnt = 2
kblob_mbuf_ref: size = 59499
kblob_mbuf_free: size = 59499
deref, id = 0, refcnt = 2
kblob_mbuf_ref: size = 59499
kblob_mbuf_free: size = 59499

which is the output of the ext_free and ext_ref functions, after that
for a couple of seconds i get this as long as the remote side doesn't
close the connection:

kblob_mbuf_ref: size = 59499
kblob_mbuf_free: size = 59499
deref, id = 0, refcnt = 1
...
kblob_mbuf_ref: size = 59499
kblob_mbuf_free: size = 59499
deref, id = 0, refcnt = 1
kblob_mbuf_ref: size = 59499
kblob_mbuf_free: size = 59499
deref, id = 0, refcnt = 1

as if it's retrying.

after the remote side closes the connection, the mbuf is finally free'd
after a short delay.

Is there some weird limit i'm bumping into?  Will I have to break this
down into multiple mbufs with external storage?

FYI I'm using fxp and:

5.0-CURRENT FreeBSD 5.0-CURRENT #0: Sun Jul  2 11:59:25 PDT 2000

thanks,
-Alfred


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