On 10/08/2019 03:20 PM, bodo.stroesser@xxxxxxxxxxxxxx wrote:
> Hi,
>
> We use TCMUser to run userspace tape and changer emulations.
>
> Current tests with a new version of backup SW failed, due to that application
> using SECURITY PROTOCOL IN / OUT SCSI commands.
> The CDBs of these commands in byte 1 contain relevant information that
> is overwritten in passthrough_parse_cdb() / target_core_device.c
>
> This is the related part of the code:
>
> /*
> * Clear a lun set in the cdb if the initiator talking to use spoke
> * and old standards version, as we can't assume the underlying device
> * won't choke up on it.
> */
> switch (cdb[0]) {
> case READ_10: /* SBC - RDProtect */
> case READ_12: /* SBC - RDProtect */
> case READ_16: /* SBC - RDProtect */
> case SEND_DIAGNOSTIC: /* SPC - SELF-TEST Code */
> case VERIFY: /* SBC - VRProtect */
> case VERIFY_16: /* SBC - VRProtect */
> case WRITE_VERIFY: /* SBC - VRProtect */
> case WRITE_VERIFY_12: /* SBC - VRProtect */
> case MAINTENANCE_IN: /* SPC - Parameter Data Format for SA RTPG */
> break;
> default:
> cdb[1] &= 0x1f; /* clear logical unit number */
> break;
> }
>
> Obviously the list of command codes for which bits 5,6,7 of byte 1 are _not_ reset
> is not complete. Now I'm wondering what would be the right fix:
>
> 1) Scan the SCSI specs and add all other missing command codes to the list of
> Codes to skip
>
> 2) Create a list of commands that definitely have the LUN field in byte 1 and
> reset the bits only in those. (Might be better than 1), because I expect new
> commands to not have the LUN field.)
>
> 3) Remove the code entirely, because it is no longer needed / useful (?)
>
My preference would be to remove it like Bart suggested. Maybe we should
make it configurable via a device attribute or backend module flag.
For the 2 users:
pscsi - It seems this code was there from the beginning via
transport_generic_prepare_cdb in the original commit. Nick must have
found some initiator where the workaround was needed and I am not sure
if we would break them or not now. Based on the original code's comment
about iscsi my guess is there was some misc iscsi initiator probably in
a boot firmware or some offload card that supported old commands.
tcmu - We want the raw cdb. I think masking out the above bits was an
accident. It looks like when Andy converted tcmu to use common code the
behavior got brought in for tcmu.
