Re: [PATCH] libmultipath: Handle SCSI-2 style vpd page 0x83 descriptors

[Benjamin Marzinski <bmarzins@redhat.com>]

On Mon, Apr 13, 2026 at 01:11:33PM +0200, Martin Wilck wrote:
> On Thu, 2026-03-26 at 23:41 -0400, Benjamin Marzinski wrote:
> > Some older SCSI devices return a SCSI-2 style vpd page 0x83, instead
> > of
> > a SPC-2/3 format one. The SCSI-2 page 83 format returns an IEEE WWN
> > in
> > binary encoded hexi-decimal in the 16 bytes following the initial
> > 4-byte page 83 reply header.
> > 
> > Check the 7th byte of the vpd page 83 buffer to determine whether
> > this
> > is a SCSI-2 or SPC-2/3 confomant one. Byte 7 is the 3rd byte of first
> > Identification descriptor in a SPC-2/3 confromant vpd page 83. This
> > is a
> > reserved field, and is guaranteed to be 0. If it is not zero, then it
> > is
> > likely the 3rd byte of a SCSI-2 Identifier (The first 3 bytes of the
> > ID
> > are the Organizationally Unique Identifier). Both the sg_inq and
> > scsi_id
> > commands handle vpd page 83 this way. To make sure that the WWID
> > which
> > multipath reads directly from the device matches, it should handle
> > this
> > format as well.
> > 
> > Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
> > ---
> >  libmultipath/discovery.c | 13 +++++++++
> >  tests/vpd.c              | 58
> > ++++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 71 insertions(+)
> > 
> > diff --git a/libmultipath/discovery.c b/libmultipath/discovery.c
> > index 0efb8213..057ff45f 100644
> > --- a/libmultipath/discovery.c
> > +++ b/libmultipath/discovery.c
> > @@ -1208,6 +1208,18 @@ parse_vpd_pg83(const unsigned char *in, size_t
> > in_len,
> >  	if (out_len <= 1)
> >  		return 0;
> >  
> > +	/*
> > +	 * Not a valid SPC-2/3 vpd page 83. Assume it's a SCSI-2
> > style
> > +	 * descriptor.
> > +	 */
> > +	if (in[6] != 0) {
> 
> Make sure that if in_len is > 6 (or actually, large enough to hold the
> SCSI-2 ID)?
>  

Good call.

-Ben

> > +		len = 0;
> > +		vpd_type = 0x3;
> > +		vpd_len = in_len - 4;
> > +		vpd = in + 4;
> > +		goto decode;
> > +	}
> > +
> 
> Regards,
> Martin