Re: pcap DLT request for virtio-scsi SCSI transport

[Stefan Hajnoczi <stefanha () gmail com>]

On Tue, Feb 28, 2012 at 11:05 AM, Stefan Hajnoczi <stefanha () gmail com> wrote:

Sorry for the delay, I didn't realize you had replied.  I am not
subscribed to this mailing list, please Reply-All and keep me CCed.

> > The QEMU system emulator now supports the virtio-scsi SCSI transport
> > for efficient virtualized SCSI I/O.  I would like to support
> > virtio-scsi debugging and analysis with pcap.
> >
> > The pcap data will include the virtio buffers containing SCSI command
> > metadata, CDB, and data-out buffer.  A similar structure is also used
> > for SCSI responses with the data-in buffer and a footer.
> >
> > You can find detailed information on virtio-scsi in Appendix H of the
> > virtio specification:
> > http://ozlabs.org/~rusty/virtio-spec/virtio-0.9.4.pdf
>
> OK, so what does a single packet look like?  Does each packet correspond to a single SCSI command or response?

There are SCSI commands and responses.  Commands and responses are
separate pcap packets because there can be multiple outstanding
commands to multiple targets/LUNs.

From the spec, commands have the following layout:

    u8 lun[8];
    u64 id;
    u8 task_attr;
    u8 prio;
    u8 crn;
    char cdb[cdb_size];
    char dataout[];

Responses have the following layout:

    u32 sense_len;
    u32 residual;
    u16 status_qualifier;
    u8 status;
    u8 response;
    u8 sense[sense_size];
    char datain[];

The pcap mapping of this layout should be straightforward.

Stefan
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