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: TAPER-OK or, for fatal errors, with: TAPER-ERROR [<message>]

• driver can ask taper to 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 request that the dump be retried at a later time with: TRY-AGAIN <handle> [<message>] or, for fatal errors, be abandoned with: TAPE-ERROR <handle> [<message>]

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
DONE	Full dump is on the media
PARTIAL	Dump was partially written to the media. PARTIAL responses also contain TRYAGAIN - The dump should retried NOTRYAGAIN - Should not retry (Example: If there is missing chunk in the holding disk)
FAILED	Nothing was written to the media
SAME-TAPE	This tape can be use for another dump
TAPE-ERROR	No more space in the current tape
PORT	Reply sent in response to PORT-WRITE command

Driver/Taper Requests/Replies

Driver request	Taper reply	Description
START-TAPER	TAPE-OK	normal taper setup (a tape is available, nothing is written on it)
START-TAPER	TAPE-ERROR	failed taper setup (no tape are available or something else is broken)
NEW-TAPE	NEW-TAPE	The driver tell the taper to use a new tape, the taper found one
NEW-TAPE	NO-NEW-TAPE	The driver tell the taper to use a new tape, no tape are available
FILE-WRITE	DONE	normal protocol for a success
	SAME-TAPE	Continue using the same tape
FILE-WRITE	FAILED	protocol for error in setup (before something is written to tape)
	TRYAGAIN or NOTRYAGAIN	Information on whether the command should be retried
	SAMETAPE or TAPE-ERROR	Continue using the same tape for next dump or not
FILE-WRITE	PARTIAL or FAILED	protocol for error in data phase
	TRYAGAIN or NOTRYAGAIN	Information on whether the command should be retried
	SAMETAPE or TAPE-ERROR	Continue using the same tape for next dump or not
PORT-WRITE	PORT	Normal port establishment protocol and dumper status
DONE	DONE or PARTIAL	Dumper can send DONE reply to driver but, dumper can fail to write everything to the tape (PARTIAL)
	TRYAGAIN or NOTRYAGAIN
	SAME-TAPE or TAPE-ERROR
PORT-WRITE	FAILED	Protocol error in port setup
	TRYAGAIN or NOTRYAGAIN
	SAME-TAPE or TAPE-ERROR
PORT-WRITE	PORT	Protocol for error in data phase (dumper errors)
FAILED	PARTIAL or FAILED	result of the dumper
	TRYAGAIN or NOTRYAGAIN
	SAME-TAPE or TAPE-ERROR
<Split dump handling>	SPLIT_CONTINUE	if it's a split dump, then taper send this after each chunk is written to tape.
	SPLIT_NEED_NEXT	it it hit end of tape
NEW-TAPE	NEW-TAPE	driver tells the taper to use a new tape, taper found one
	NO-NEW-TAPE	driver tell the taper to use a new, no tape are available. Continues with a PARTIAL result
NO-NEW-TAPE		Taper continues with PARTIAL result