Re: mbuf doubts

From: Giovanni P. Tirloni (gpt_at_tirloni.org)
Date: 09/24/03

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    Date: Wed, 24 Sep 2003 13:55:35 -0300
To: freebsd-hackers@freebsd.org

    * Jerry Toung (jtoung@arc.nasa.gov) wrote:
    > Giovani,
    >
    > you will find the answer to your question in "tcp/ip illustrated, volume 2:
    > the implementation" in chapter 2.
    >
    > But to briefly answer your question, yes, there are 4 different types of
    > mbufs, depending on the m_flags value.
    > 1) m_flags = 0 and mbuf contains only data up to 108 bytes.
    > 2) m_flags = M_PKTHDR to designate a packet header.
    > 3)m_flags = M_EXT. In a situation where a user process write() in a buffer >
    > 256 bytes, the system allocates a cluster to hold that data.
    > 4) m_flags = M_EXT|M_PKTHDR
    >
    > and yes when using clusters, the memory in the mbuf is unsed.
    >
    > hop that helped.

     Thank you very much Justin and Jerry for the answers. They were very
     helpful.

     I'm already getting my copy of Steven's :-)

     --
     Giovanni P. Tirloni <gpt at tirloni.org>
     Fingerprint: 8C3F BEC5 79BD 3E9B EDB8 72F4 16E8 BA5E D031 5C26
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