Driver-Taper protocol

Communication method

driver talks via two pipes connected to taper's stdin and stdout. The commands and responses are plain text.

Command sequence during backup operation

• driver initialises taper with: START-TAPER <datestamp> to which taper replies with: TAPE-OK or, for fatal errors, with: TAPE-ERROR [<message>]

• driver will ask the taper to start a new tape with the NEW-TAPE command.

• driver can ask taper to copy a file from the holding disk to tape: FILE-WRITE <handle> <filename> <host> <disk> <level> or directly from a dumper: PORT-WRITE <handle> <host> <disk> <level> or exit at the end of the run: QUIT

• taper responds to the PORT-WRITE command with: PORT <port> which driver should then hand on to dumper in a PORT-DUMP command.

• If the copy to tape finishes correctly taper replies with: DONE <handle> [<message>]

• If something goes wrong with the tape, taper can ask to continue on a new tape SPLIT-NEEDNEXT (for splited dump only) or it can abort that dump with PARTIAL or FAILED reply

• After any dump that finished in PARTIAL or FAILED with a TAPE-ERROR, the driver must send a NEW-TAPE before issuing another *-WRITE command.

Other commands

• If driver says something that taper doesn't recognise it responds with: BAD-COMMAND <message>
• taper responds to the QUIT command with: QUITING

Protocol data

data	description
<datestamp>	Date as "yymmdd"
<handle>	Request ID
<filename>	Name of file on the holding disk where backup will be written to
<port>	Taper port to send the backup data to
<host>	Hostname of the client
<disk>	Disk on the client being backed up
<level>	Dump level being used for backup
<message>	Error or Status message

Protocol command reference

Taper command reply

Reply	Description
TAPE-OK	taper is setup correctly
TAPE-ERROR	Error in setup of the driver
PORT	Reply sent in response to PORT-WRITE command
DONE	Full dump is on the media
PARTIAL	Dump was partially written to the media.
FAILED	Nothing was written to the media
SPLIT-CONTINUE	A complete part is written to tape
SPLIT-NEEDNEXT	Ask driver if it should continue on a new tape
NEW-TAPE	Will continue on a new found tape
NO-NEW-TAPE	Will not continue on a new tape

DONE/PARTIAL and FAILED reply also contains an INPUT-* an TAPE-* message to denote any error:

Reply	Description
INPUT-GOOD	There was no error with the input.
INPUT-ERROR	There was error with the input.

Reply	Description
TAPE-GOOD	This tape can be use to write another dump.
TAPE-ERROR	Nothing more can fit on that tape.

A result for a successful dump should be: DONE INPUT-GOOD TAPE-GOOD

Driver/Taper Requests/Replies

Driver request		Taper reply	Description
initail setup
START-TAPER	--->
	<---	TAPE-OK	normal taper setup (a tape is available, nothing is written on it)
	<---	TAPE-ERROR	failed taper setup (no tape are available or something else is broken)
ask for new tape
NEW-TAPE	--->		driver tell the taper to use a new tape
	<---	GOT-NEW-TAPE	taper found one
	<---	NO-NEW-TAPE	no tape are available
file-write setup
FILE-WRITE	--->
			Will get one part-result for each part written and one global result
port-write setup
PORT-WRITE	--->
	<---	PORT
			WIll continue with one part-result for each part written and one global result
global-result
	<---	DONE INPUT-GOOD TAPE-GOOD	normal protocol for a success
	<---	PARTIAL INPUT-* TAPE-*	protocol for error in data phase (something written to tape)
	<---	FAILED INPUT-* TAPE-*	protocol for error in setup (before something is written to tape)
part-result
	<---	SPLIT-CONTINUE	successfully part written to tape
	<---	SPLIT-NEEDNEXT	failed PART (only for tape-error) (driver will send a NEW-TAPE or NO-NEW-TAPE command)
no new tape
NO-NEW-TAPE	--->		driver doesn't want the taper to use a new tape (continue with global-result)