Schily's USER COMMANDS RSCSI(1)
NAME
rscsi - 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 connected 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 performs 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 checking.
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 fol-
lowing 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 usually 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 correspond-
ing 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
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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 ver-
sion 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 ver-
sion of kernel instance of the driver
that is underneath the low level SCSI
transport adaptation layer.
This call may not be supported for all
operating systems.
This command corresponds to the
scg_version(3) function from libscg.
Odevice\n Open the specified SCSI device.
See the description of the dev= option in
cdrecord(1) for more information on possi-
ble 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.
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Cdevice\n Close the currently open device or file.
The argument device is ignored.
This command corresponds to the
scg_close(3) function 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) function 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) function 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) function 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) function 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 currently ignored.
This command corresponds to the
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scg_havebus(3) function 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, tar-
get, 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) function 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) function from libscg.
The return value is the return value from
the scg_reset(3) function.
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Scount\nflags\ncdb_len\nsense_len\ntimeout\n
Send a SCSI command to the currently
selected target. This command takes the
following parameters:
count
The DMA count for this command. If the
command is a command that transfers
data to the target, the related data
is send directly after the SCSI com-
mand descriptor block. that is
described above.
flags
The flags that apply to this SCSI com-
mand:
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
command 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 supported on all plat-
forms.
8 Tell the kernel to retry the SCSI
command in case of a retryable
SCSI transport error. This
corresponds to the flag value
SCG_CMD_RETRY. This flag is not
supported on all platforms.
16 Tell the kernel to send the SCSI
command with parity disabled.
This corresponds to the flag
value SCG_NOPARITY. This flag is
not supported on all platforms.
cdb_len
The SCSI command descriptor length for
this command. The SCSI command
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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 men-
tioned above.
error
A SCSI error classification from one
of the following values:
0 No error occurred. This value
corresponds to the value
SCG_NO_ERROR .
1 A retryable error occurred while
trying to transport the SCSI com-
mand to the target. This value
corresponds to the value
SCG_RETRYABLE .
2 A fatal error occurred while try-
ing to transport the SCSI command
to the target. This value
corresponds to the value
SCG_FATAL .
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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
command. 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 informa-
tion.
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
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of the rscsi server followed by the name of a host
from where operation is granted followed 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 matching 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 ALSO
cdrecord(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
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The rscsi command has been developed by Joerg Schilling in
June 2000.
AUTHOR
Joerg Schilling
D-13353 Berlin
Germany
Mail bugs and suggestions to:
joerg@schily.net
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.
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