Documentation/networking/6pack.txt - kernel/msm - Gitiles

 This is the 6pack-mini-HOWTO, written by

 Andreas Könsgen DG3KQ
 Internet: ajk@comnets.uni-bremen.de
 AMPR-net: dg3kq@db0pra.ampr.org
 AX.25:    dg3kq@db0ach.#nrw.deu.eu

 Last update: April 7, 1998

 1. What is 6pack, and what are the advantages to KISS?

 6pack is a transmission protocol for data exchange between the PC and
 the TNC over a serial line. It can be used as an alternative to KISS.

 6pack has two major advantages:
 - The PC is given full control over the radio
   channel. Special control data is exchanged between the PC and the TNC so
   that the PC knows at any time if the TNC is receiving data, if a TNC
   buffer underrun or overrun has occurred, if the PTT is
   set and so on. This control data is processed at a higher priority than
   normal data, so a data stream can be interrupted at any time to issue an
   important event. This helps to improve the channel access and timing
   algorithms as everything is computed in the PC. It would even be possible
   to experiment with something completely different from the known CSMA and
   DAMA channel access methods.
   This kind of real-time control is especially important to supply several
   TNCs that are connected between each other and the PC by a daisy chain
   (however, this feature is not supported yet by the Linux 6pack driver).

 - Each packet transferred over the serial line is supplied with a checksum,
   so it is easy to detect errors due to problems on the serial line.
   Received packets that are corrupt are not passed on to the AX.25 layer.
   Damaged packets that the TNC has received from the PC are not transmitted.

 More details about 6pack are described in the file 6pack.ps that is located
 in the doc directory of the AX.25 utilities package.

 2. Who has developed the 6pack protocol?

 The 6pack protocol has been developed by Ekki Plicht DF4OR, Henning Rech
 DF9IC and Gunter Jost DK7WJ. A driver for 6pack, written by Gunter Jost and
 Matthias Welwarsky DG2FEF, comes along with the PC version of FlexNet.
 They have also written a firmware for TNCs to perform the 6pack
 protocol (see section 4 below).

 3. Where can I get the latest version of 6pack for LinuX?

 At the moment, the 6pack stuff can obtained via anonymous ftp from
 db0bm.automation.fh-aachen.de. In the directory /incoming/dg3kq,
 there is a file named 6pack.tgz.

 4. Preparing the TNC for 6pack operation

 To be able to use 6pack, a special firmware for the TNC is needed. The EPROM
 of a newly bought TNC does not contain 6pack, so you will have to
 program an EPROM yourself. The image file for 6pack EPROMs should be
 available on any packet radio box where PC/FlexNet can be found. The name of
 the file is 6pack.bin. This file is copyrighted and maintained by the FlexNet
 team. It can be used under the terms of the license that comes along
 with PC/FlexNet. Please do not ask me about the internals of this file as I
 don't know anything about it. I used a textual description of the 6pack
 protocol to program the Linux driver.

 TNCs contain a 64kByte EPROM, the lower half of which is used for
 the firmware/KISS. The upper half is either empty or is sometimes
 programmed with software called TAPR. In the latter case, the TNC
 is supplied with a DIP switch so you can easily change between the
 two systems. When programming a new EPROM, one of the systems is replaced
 by 6pack. It is useful to replace TAPR, as this software is rarely used
 nowadays. If your TNC is not equipped with the switch mentioned above, you
 can build in one yourself that switches over the highest address pin
 of the EPROM between HIGH and LOW level. After having inserted the new EPROM
 and switched to 6pack, apply power to the TNC for a first test. The connect
 and the status LED are lit for about a second if the firmware initialises
 the TNC correctly.

 5. Building and installing the 6pack driver

 The driver has been tested with kernel version 2.1.90. Use with older
 kernels may lead to a compilation error because the interface to a kernel
 function has been changed in the 2.1.8x kernels.

 How to turn on 6pack support:

 - In the linux kernel configuration program, select the code maturity level
   options menu and turn on the prompting for development drivers.

 - Select the amateur radio support menu and turn on the serial port 6pack
   driver.

 - Compile and install the kernel and the modules.

 To use the driver, the kissattach program delivered with the AX.25 utilities
 has to be modified.

 - Do a cd to the directory that holds the kissattach sources. Edit the
   kissattach.c file. At the top, insert the following lines:

   #ifndef N_6PACK
   #define N_6PACK (N_AX25+1)
   #endif

   Then find the line

   int disc = N_AX25;

   and replace N_AX25 by N_6PACK.

 - Recompile kissattach. Rename it to spattach to avoid confusions.

 Installing the driver:

 - Do an insmod 6pack. Look at your /var/log/messages file to check if the
   module has printed its initialization message.

 - Do a spattach as you would launch kissattach when starting a KISS port.
   Check if the kernel prints the message '6pack: TNC found'.

 - From here, everything should work as if you were setting up a KISS port.
   The only difference is that the network device that represents
   the 6pack port is called sp instead of sl or ax. So, sp0 would be the
   first 6pack port.

 Although the driver has been tested on various platforms, I still declare it
 ALPHA. BE CAREFUL! Sync your disks before insmoding the 6pack module
 and spattaching. Watch out if your computer behaves strangely. Read section
 6 of this file about known problems.

 Note that the connect and status LEDs of the TNC are controlled in a
 different way than they are when the TNC is used with PC/FlexNet. When using
 FlexNet, the connect LED is on if there is a connection; the status LED is
 on if there is data in the buffer of the PC's AX.25 engine that has to be
 transmitted. Under Linux, the 6pack layer is beyond the AX.25 layer,
 so the 6pack driver doesn't know anything about connects or data that
 has not yet been transmitted. Therefore the LEDs are controlled
 as they are in KISS mode: The connect LED is turned on if data is transferred
 from the PC to the TNC over the serial line, the status LED if data is
 sent to the PC.

 6. Known problems

 When testing the driver with 2.0.3x kernels and
 operating with data rates on the radio channel of 9600 Baud or higher,
 the driver may, on certain systems, sometimes print the message '6pack:
 bad checksum', which is due to data loss if the other station sends two
 or more subsequent packets. I have been told that this is due to a problem
 with the serial driver of 2.0.3x kernels. I don't know yet if the problem
 still exists with 2.1.x kernels, as I have heard that the serial driver
 code has been changed with 2.1.x.

 When shutting down the sp interface with ifconfig, the kernel crashes if
 there is still an AX.25 connection left over which an IP connection was
 running, even if that IP connection is already closed. The problem does not
 occur when there is a bare AX.25 connection still running. I don't know if
 this is a problem of the 6pack driver or something else in the kernel.

 The driver has been tested as a module, not yet as a kernel-builtin driver.

 The 6pack protocol supports daisy-chaining of TNCs in a token ring, which is
 connected to one serial port of the PC. This feature is not implemented
 and at least at the moment I won't be able to do it because I do not have
 the opportunity to build a TNC daisy-chain and test it.

 Some of the comments in the source code are inaccurate. They are left from
 the SLIP/KISS driver, from which the 6pack driver has been derived.
 I haven't modified or removed them yet -- sorry! The code itself needs
 some cleaning and optimizing. This will be done in a later release.

 If you encounter a bug or if you have a question or suggestion concerning the
 driver, feel free to mail me, using the addresses given at the beginning of
 this file.

 Have fun!

 Andreas
	This is the 6pack-mini-HOWTO, written by

	Andreas Könsgen DG3KQ
	Internet: ajk@comnets.uni-bremen.de
	AMPR-net: dg3kq@db0pra.ampr.org
	AX.25: dg3kq@db0ach.#nrw.deu.eu

	Last update: April 7, 1998

	1. What is 6pack, and what are the advantages to KISS?

	6pack is a transmission protocol for data exchange between the PC and
	the TNC over a serial line. It can be used as an alternative to KISS.

	6pack has two major advantages:
	- The PC is given full control over the radio
	channel. Special control data is exchanged between the PC and the TNC so
	that the PC knows at any time if the TNC is receiving data, if a TNC
	buffer underrun or overrun has occurred, if the PTT is
	set and so on. This control data is processed at a higher priority than
	normal data, so a data stream can be interrupted at any time to issue an
	important event. This helps to improve the channel access and timing
	algorithms as everything is computed in the PC. It would even be possible
	to experiment with something completely different from the known CSMA and
	DAMA channel access methods.
	This kind of real-time control is especially important to supply several
	TNCs that are connected between each other and the PC by a daisy chain
	(however, this feature is not supported yet by the Linux 6pack driver).

	- Each packet transferred over the serial line is supplied with a checksum,
	so it is easy to detect errors due to problems on the serial line.
	Received packets that are corrupt are not passed on to the AX.25 layer.
	Damaged packets that the TNC has received from the PC are not transmitted.

	More details about 6pack are described in the file 6pack.ps that is located
	in the doc directory of the AX.25 utilities package.

	2. Who has developed the 6pack protocol?

	The 6pack protocol has been developed by Ekki Plicht DF4OR, Henning Rech
	DF9IC and Gunter Jost DK7WJ. A driver for 6pack, written by Gunter Jost and
	Matthias Welwarsky DG2FEF, comes along with the PC version of FlexNet.
	They have also written a firmware for TNCs to perform the 6pack
	protocol (see section 4 below).

	3. Where can I get the latest version of 6pack for LinuX?

	At the moment, the 6pack stuff can obtained via anonymous ftp from
	db0bm.automation.fh-aachen.de. In the directory /incoming/dg3kq,
	there is a file named 6pack.tgz.

	4. Preparing the TNC for 6pack operation

	To be able to use 6pack, a special firmware for the TNC is needed. The EPROM
	of a newly bought TNC does not contain 6pack, so you will have to
	program an EPROM yourself. The image file for 6pack EPROMs should be
	available on any packet radio box where PC/FlexNet can be found. The name of
	the file is 6pack.bin. This file is copyrighted and maintained by the FlexNet
	team. It can be used under the terms of the license that comes along
	with PC/FlexNet. Please do not ask me about the internals of this file as I
	don't know anything about it. I used a textual description of the 6pack
	protocol to program the Linux driver.

	TNCs contain a 64kByte EPROM, the lower half of which is used for
	the firmware/KISS. The upper half is either empty or is sometimes
	programmed with software called TAPR. In the latter case, the TNC
	is supplied with a DIP switch so you can easily change between the
	two systems. When programming a new EPROM, one of the systems is replaced
	by 6pack. It is useful to replace TAPR, as this software is rarely used
	nowadays. If your TNC is not equipped with the switch mentioned above, you
	can build in one yourself that switches over the highest address pin
	of the EPROM between HIGH and LOW level. After having inserted the new EPROM
	and switched to 6pack, apply power to the TNC for a first test. The connect
	and the status LED are lit for about a second if the firmware initialises
	the TNC correctly.

	5. Building and installing the 6pack driver

	The driver has been tested with kernel version 2.1.90. Use with older
	kernels may lead to a compilation error because the interface to a kernel
	function has been changed in the 2.1.8x kernels.

	How to turn on 6pack support:

	- In the linux kernel configuration program, select the code maturity level
	options menu and turn on the prompting for development drivers.

	- Select the amateur radio support menu and turn on the serial port 6pack
	driver.

	- Compile and install the kernel and the modules.

	To use the driver, the kissattach program delivered with the AX.25 utilities
	has to be modified.

	- Do a cd to the directory that holds the kissattach sources. Edit the
	kissattach.c file. At the top, insert the following lines:

	#ifndef N_6PACK
	#define N_6PACK (N_AX25+1)
	#endif

	Then find the line

	int disc = N_AX25;

	and replace N_AX25 by N_6PACK.

	- Recompile kissattach. Rename it to spattach to avoid confusions.

	Installing the driver:

	- Do an insmod 6pack. Look at your /var/log/messages file to check if the
	module has printed its initialization message.

	- Do a spattach as you would launch kissattach when starting a KISS port.
	Check if the kernel prints the message '6pack: TNC found'.

	- From here, everything should work as if you were setting up a KISS port.
	The only difference is that the network device that represents
	the 6pack port is called sp instead of sl or ax. So, sp0 would be the
	first 6pack port.

	Although the driver has been tested on various platforms, I still declare it
	ALPHA. BE CAREFUL! Sync your disks before insmoding the 6pack module
	and spattaching. Watch out if your computer behaves strangely. Read section
	6 of this file about known problems.

	Note that the connect and status LEDs of the TNC are controlled in a
	different way than they are when the TNC is used with PC/FlexNet. When using
	FlexNet, the connect LED is on if there is a connection; the status LED is
	on if there is data in the buffer of the PC's AX.25 engine that has to be
	transmitted. Under Linux, the 6pack layer is beyond the AX.25 layer,
	so the 6pack driver doesn't know anything about connects or data that
	has not yet been transmitted. Therefore the LEDs are controlled
	as they are in KISS mode: The connect LED is turned on if data is transferred
	from the PC to the TNC over the serial line, the status LED if data is
	sent to the PC.

	6. Known problems

	When testing the driver with 2.0.3x kernels and
	operating with data rates on the radio channel of 9600 Baud or higher,
	the driver may, on certain systems, sometimes print the message '6pack:
	bad checksum', which is due to data loss if the other station sends two
	or more subsequent packets. I have been told that this is due to a problem
	with the serial driver of 2.0.3x kernels. I don't know yet if the problem
	still exists with 2.1.x kernels, as I have heard that the serial driver
	code has been changed with 2.1.x.

	When shutting down the sp interface with ifconfig, the kernel crashes if
	there is still an AX.25 connection left over which an IP connection was
	running, even if that IP connection is already closed. The problem does not
	occur when there is a bare AX.25 connection still running. I don't know if
	this is a problem of the 6pack driver or something else in the kernel.

	The driver has been tested as a module, not yet as a kernel-builtin driver.

	The 6pack protocol supports daisy-chaining of TNCs in a token ring, which is
	connected to one serial port of the PC. This feature is not implemented
	and at least at the moment I won't be able to do it because I do not have
	the opportunity to build a TNC daisy-chain and test it.

	Some of the comments in the source code are inaccurate. They are left from
	the SLIP/KISS driver, from which the 6pack driver has been derived.
	I haven't modified or removed them yet -- sorry! The code itself needs
	some cleaning and optimizing. This will be done in a later release.

	If you encounter a bug or if you have a question or suggestion concerning the
	driver, feel free to mail me, using the addresses given at the beginning of
	this file.

	Have fun!

	Andreas