RSCSI(1) Schily´s USER COMMANDS RSCSI(1)NAMErscsi - remote generic SCSI transport protocol server
SYNOPSIS
/opt/schily/sbin/rscsi
DESCRIPTION
The rscsi command is a remote generic SCSI transport server program.
rscsi is a program that is run locally on the machine with SCSI
devices, it is used by remote programs like cdrecord(1), cdda2wav(1),
readcd(1), and sformat(1) that like to access SCSI devices through an
interprocess communication connection via libscg. rscsi is normally
started up with an rexec(3) or rcmd(3) call but it may also be con‐
nected via an internal pipe to an ssh(1) session that was set up by the
remote user.
The rscsi program accepts scg_open, scg_close, scg_cmd and similar
requests that are all related to the interface of libscg. rscsi per‐
forms the commands and then responds with a status indication.
The rscsi program is prepared to be installed as a user shell in the
passwd file to create remote SCSI specific logins and security check‐
ing.
All requests are send to the rscsi program in ASCII and thus are byte
order and machine independent.
All responses are send back in ASCII and in one of the following two
forms.
All successful commands (except for the "S" command that sends SCSI
commands) have responses of
Anumber\n
where number is the ASCII representation of a decimal number that usu‐
ally is the return code of the corresponding system call or function.
All unsuccessful commands are responded to with
Eerror-number\nerror-message\nxerror-len\nxerror-txt
where error-number is one of the possible error numbers described in
intro(2), and error-message is the corresponding error string as
retrieved by strerror(3), xerror-len is the length of the additional
error text xerror-txt and may be 0. In case xerror-len is 0, no xerror-
txt is send. Note that a failed SCSI command that returned SCSI sense
data counts as a successful command and does not use the default error
format.
The rscsi protocol implements the following commands:
Vwhat\n Return the version for several instances of the
software in the rscsi server. The parameter what
may have the following values:
0 Return SCG_VERSION from libscg on the rscsi
server. This returns the version string for
the low level SCSI transport adaptation
layer.
1 Return SCG_AUTHOR from libscg on the rscsi
server. This returns the author name for the
low level SCSI transport adaptation layer.
2 Return SCG_SCCS_ID from libscg on the rscsi
server. This returns the SCCS version string
for the low level SCSI transport adaptation
layer.
20 Return SCG_KVERSION from libscg on the rscsi
server. This returns the version of kernel
instance of the driver that is underneath the
low level SCSI transport adaptation layer.
This call may not be supported for all oper‐
ating systems.
This command corresponds to the scg_version(3) func‐
tion from libscg.
Odevice\n Open the specified SCSI device.
See the description of the dev= option in
cdrecord(1) for more information on possible values
of the device parameter.
If a device is already open, it is closed before a
new open is performed.
This command corresponds to the scg_open(3) function
from libscg.
The return value in case of success is 0.
Cdevice\n Close the currently open device or file. The argu‐
ment device is ignored.
This command corresponds to the scg_close(3) func‐
tion from libscg.
The return value is the return value from the
scg_close(3) function.
Dsize\n Set up the maximum DMA size for the currently open
SCSI device. The size parameter is the desired DMA
size in bytes.
This command corresponds to the scg_bufsize(3) func‐
tion from libscg.
The returned value is the actual DMA size that could
be set up. This value may be lower than the size
parameter.
Msize\n Allocate a buffer suitable for SCSI DMA transfers.
This command corresponds to the scg_getbuf(3) func‐
tion from libscg.
The returned value is the actual DMA size that could
be set up. This value may be lower than the size
parameter.
F\n Free a previously allocated buffer.
This command corresponds to the scg_freebuf(3) func‐
tion from libscg.
The return value in case of success is 0.
N\n Retrieve the maximum permitted value for the SCSI
bus number.
This command corresponds to the scg_numbus(3) func‐
tion from libscg.
The return value is the return value from the
scg_numbus(3) function.
Bbusno\nchan\n
Checks whether there is a SCSI bus with a busnumber
that is equal to busno. The chan parameter is cur‐
rently ignored.
This command corresponds to the scg_havebus(3) func‐
tion from libscg.
The return value is the return value from the
scg_havebus(3) function.
Tbusno\nchan\ntarget\nlun\n
Set the SCSI target address to busno, target, lun.
The parameter chan is currently ignored.
This command corresponds to the scg_settarget(3)
function from libscg.
The return value is the return value from the
scg_havebus(3) function.
I\n Retrieve the SCSI initiator ID for the current SCSI
bus.
This command corresponds to the scg_initiator_id(3)
function from libscg.
The return value is the return value from the
scg_initiator_id(3) function.
A\n Check whether the current target is or may be an
ATAPI device.
This command corresponds to the scg_isatapi(3) func‐
tion from libscg.
The return value is the return value from the
scg_isatapi(3) function.
Rwhat\n Perform a SCSI reset. The parameter what may have
the following values:
0 Test whether a SCSI reset is supported as
with the SCG_RESET_NOP parameter.
1 Perform a SCSI target reset as with the
SCG_RESET_TGT parameter.
2 Perform a SCSI bus reset as with the
SCG_RESET_BUS parameter.
This command corresponds to the scg_reset(3) func‐
tion from libscg.
The return value is the return value from the
scg_reset(3) function.
Scount\nflags\ncdb_len\nsense_len\ntimeout\n
Send a SCSI command to the currently selected tar‐
get. This command takes the following parameters:
count The DMA count for this command. If the com‐
mand is a command that transfers data to the
target, the related data is send directly
after the SCSI command descriptor block.
that is described above.
flags The flags that apply to this SCSI command:
1 Tell the kernel that the SCSI command
will transfer data from the target to
the host. This corresponds to the
flag value SCG_RECV_DATA.
2 Tell the kernel to send the SCSI com‐
mand with disconnect/reconnect
enabled. This corresponds to the flag
value SCG_DISRE_ENA. This flag is not
supported on all platforms.
4 Make the kernel silent on SCSI errors.
This corresponds to the flag value
SCG_SILENT. This flag is not sup‐
ported on all platforms.
8 Tell the kernel to retry the SCSI com‐
mand in case of a retryable SCSI
transport error. This corresponds to
the flag value SCG_CMD_RETRY. This
flag is not supported on all plat‐
forms.
16 Tell the kernel to send the SCSI com‐
mand with parity disabled. This cor‐
responds to the flag value SCG_NOPAR‐
ITY. This flag is not supported on
all platforms.
cdb_len
The SCSI command descriptor length for this
command. The SCSI command descriptor has to
be send with the correct length directly
after the new line past the timeout value.
sense_len
The amount of sense data that is expected in
return of a failed SCSI command that produces
SCSI sense data.
timeout
The timeout for the SCSI command in seconds.
Fractions of a second may be specified by
sending a floating point number.
The reply for a SCSI command that could be send to
the target is:
Acount\nerror\nerrno\nscb\nsense_count\n
count The DMA count of any data returned from the
target. If this count is nonzero, the data
is send back directly after the reply block
mentioned above.
error A SCSI error classification from one of the
following values:
0 No error occurred. This value corre‐
sponds to the value SCG_NO_ERROR .
1 A retryable error occurred while try‐
ing to transport the SCSI command to
the target. This value corresponds to
the value SCG_RETRYABLE .
2 A fatal error occurred while trying to
transport the SCSI command to the tar‐
get. This value corresponds to the
value SCG_FATAL .
3 A SCSI timeout occurred. This value
corresponds to the value SCG_TIMEOUT .
errno Any possible UNIX errno value for the SCSI
command.
scb The SCSI status byte
sense_count
The sense count returned for the SCSI com‐
mand. The SCSI sense data is send back
directly after any possible SCSI DMA data
received from the target.
This command corresponds to the scg_cmd(3)
function from libscg.
The return value is the return value from the
scg_cmd(3) function.
Any other command causes rscsi to exit.
FILES
/etc/default/rscsi
Default values can be set for the following options in
/etc/default/rscsi. For example:
DEBUG=/tmp/rscsi.debug
USER=rscsi
ACCESS=rscsi myhost.mydomain.org 1 -1 3 0
All keywords must be on the beginning of a line.
DEBUG If you like to get debug information, set this to a file
name where rscsi should put debug information.
USER The name of a user (local to the RSCSI server) that may
use the services of the rscsi server. More than one
USER=name line is possible. A line USER=* grants access
to all users.
ACCESS This keyword is followed by six parameters separated by a
TAB. The name of a user (local to the RSCSI server host)
that may use the services of the rscsi server followed by
the name of a host from where operation is granted fol‐
lowed by a SCSI device specification that is made of bus-
number channel (ignored for now) target-id and lun that
specify a SCSI device that may be accessed if this ACCESS
line matches. If one or more entries of the bus-number
channel target-id lun specification is set to -1, this
matches any possible value for the related part of the
SCSI device specification. More than one ACCESS=name
host SCSI-device line is possible.
If standard input of rscsi is not a socket from a remote
host, rscsi will compare the host entry from
/etc/default/rscsi with the following strings:
PIPE If stdin is a UNIX pipe.
If you like to allow remote connections that
use the ssh protocol, you need to use the word
PIPE instead of the real hostname in the match‐
ing ACCESS= line.
ILLEGAL_SOCKET
If getpeername() does not work for stdin.
NOT_IP If getpeername() works for stdin but is not
connected to an internet socket.
SEE ALSOcdrecord(1), cdda2wav(1), readcd(1), sformat(1), ssh(1), intro(2),
open(2), close(2), read(2), write(2), ioctl(2), getpeername(3)rcmd(3),
rexec(3), strerror(3)DIAGNOSTICS
All responses are send to the network connection. They use the form
described above.
NOTES
The possibility to create a debug file by calling rscsi file has been
disabled for security reasons. If you like to debug rscsi edit
/etc/default/rscsi and insert a DEBUG entry.
BUGS
None known.
HISTORY
The rscsi command has been developed by Joerg Schilling in June 2000.
AUTHOR
Joerg Schilling
Seestr. 110
D-13353 Berlin
Germany
Mail bugs and suggestions to:
joerg.schilling@fokus.fraunhofer.de or js@cs.tu-berlin.de or
joerg@schily.isdn.cs.tu-berlin.de
INTERFACE STABILITY
The interfaces provided by rscsi are designed for long term stability.
As rscsi depends on interfaces provided by the underlying operating
system, the stability of the interfaces offered by rscsi depends on the
interface stability of the OS interfaces. Modified interfaces in the
OS may enforce modified interfaces in rscsi.
Joerg Schilling Release 3.0 RSCSI(1)
