Newsgroups: comp.os.linux.announce,comp.os.linux.admin,comp.answers,news.answers
From: Paul Gortmaker <gpg109@rsphysse.anu.edu.au>
Subject: Linux Ethernet HOWTO (part 2/2)
Message-ID: <Ethernet-HOWTO.2-8464.767302708@cs.cornell.edu>
Date: Mon, 25 Apr 1994 19:40:27 GMT
Approved: linux-announce@tc.cornell.edu (Matt Welsh)

Archive-Name: linux/howto/ethernet/part2
Last-modified: 15 Apr 94


---This is part 2/2---

5.06 Programming the Intel chips (i82586 and i82593)

	These chips are used on a number of cards, namely the 3c507 ('86),
	the Intel EtherExpress 16 ('86), Microdyne's exos205t ('86),
	the Z-Note ('93), and the Racal-Interlan ni5210 ('86).

	Russ Nelson writes:
	"Most boards based on the 82586 can reuse quite a bit of their code.
	More, in fact, than the 8390-based adapters. There are only three
	differences between them:

	  o The code to get the Ethernet address,
	  o The code to trigger CA on the 82586, and
	  o The code to reset the 82586.

	The Intel EtherExpress 16 is an exception, as it I/O maps the 82586.
	Yes, I/O maps it. Fairly clunky, but it works.

	Garrett Wollman did an AT&T driver for BSD that uses the BSD
	copyright. The latest version I have (Sep '92) only uses a single
	transmit buffer. You can and should do better than this if you've
	got the memory. The AT&T and 3c507 adapters do; the ni5210 doesn't.

	The people at Intel gave me a very big clue on how you queue up
	multiple transmit packets. You set up a list of
	NOP->XMIT->NOP->XMIT->NOP->XMIT->(beginning) blocks, then you set the
	"next" pointer of all the NOP blocks to themselves. Now you start
	the command unit on this chain. It continually processes the first
	NOP block. To transmit a packet, you stuff it into the next transmit
	block, then point the NOP to it. To transmit the next packet, you
	stuff the next transmit block and point the previous NOP to *it*. In
	this way, you don't have to wait for the previous transmit to finish,
	you can queue up multiple packets without any ambiguity as to whether
	it got accepted, and you can avoid the command unit start-up delay."

5.07	Technical information from 3Com

	From: Cameron Spitzer 764-6339 <camerons@nad.3com.com>
	Subject: getting 3Com Adapter manuals
	Date: Mon, 27 Sep 1993 21:17:07 +0200
	
	Since this is becoming a FAQ, I'm going to tread the thin
	ice of No Commercial Use and answer it here.

	3Com's Ethernet Adapters are documented for driver writers
	in our "Technical References" (TRs). These manuals describe
	the programmer interfaces to the boards but they don't talk
	about the diagnostics, installation programs, etc that end
	users can see.
	
	The Network Adapter Division marketing department has the
	TRs to give away. To keep this program efficient, we
	centralized it in a thing called "CardFacts." CardFacts is
	an automated phone system. You call it with a touch-tone
	phone and it faxes you stuff. To get a TR, call CardFacts
	at 408-727-7021. Ask it for Developer's Order Form,
	document number 9070. Have your fax number ready when you
	call. Fill out the order form and fax it to 408-764-5004.
	Manuals are shipped by Federal Express 2nd Day Service.
	
	If you don't have a fax and nobody you know has a fax,
	really and truly, *then* send mail to
	Terry_Murphy@3Mail.3Com.com and tell her about your problem.
	PLEASE use the fax thing if you possibly can.
	
	After you get a manual, if you still can't figure out how to
	program the board, try our "CardBoard" BBS at
	1-800-876-3266, and if you can't do that, write
	Andy_Chan@3Mail.3com.com and ask him for alternatives. If
	you have a real stumper that nobody has figured out yet, the
	fellow who needs to know about it is
	Steve_Lebus@3Mail.3com.com.
	
	There are people here who think we are too free with the
	manuals, and they are looking for evidence that the system
	is too expensive, or takes too much time and effort. That's
	why it's important to try to use CardFacts *before* you
	start calling and mailing the people I named here.
	
	There are even people who think we should be like Diamond
	and Xircom, requiring tight "partnership" with driver
	writers to prevent poorly performing drivers from getting
	written. So far, 3Com customers have been really good about
	this, and there's no problem with the level of requests
	we've been getting. We need your continued cooperation and
	restraint to keep it that way.
	
	Cameron Spitzer, 408-764-6339
	3Com NAD
	Santa Clara
	work: camerons@nad.3com.com
	home: cls@truffula.sj.ca.us

5.08 Notes on AMD PCnet-ISA / LANCE Based cards (79C960)

	The AMD LANCE (Local Area Network Controller for Ethernet)
	was the original offering, and has since been replaced by
	the "PCnet-ISA" chip, otherwise known as the 79C960.
	A relatively new chip from AMD, the 79C960, is the heart of many
	new cards being released at present. Note that the name "LANCE"
	has stuck, and some people will refer to the new chip by the old
	name. Dave Roberts of the Network Products Division of AMD was kind
	enough to contribute the following information regarding this chip:

	"As for the architecture itself, AMD developed it originally
	and reduced it to a single chip -- the PCnet(tm)-ISA -- over a year
	ago. It's been selling like hotcakes ever since.

	Functionally, it is equivalent to a NE1500. The register set
	is identical to the old LANCE with the 1500/2100 architecture
	additions. Older 1500/2100 drivers will work on the PCnet-ISA.
	The NE1500 and NE2100 architecture is basically the same.
	Initially Novell called it the 2100, but then tried to distinguish
	between coax and 10BASE-T cards. Anything that was 10BASE-T only was
	to be numbered in the 1500 range. That's the only difference.

	Many companies offer PCnet-ISA based products, including HP,
	Racal-Datacom, Allied Telesis, Boca Research, Kingston Technology, etc.
	The cards are basically the same except that some manufacturers
	have added "jumperless" features that allow the card to
	be configured in software. Most have not. AMD offers a standard
	design package for a card that uses the PCnet-ISA and many
	manufacturers use our design without change.
	What this means is that anybody who wants to write drivers for
	most PCnet-ISA based cards can just get the data-sheet from AMD. Call
	our literature distribution center at (800)222-9323 and ask for the
	Am79C960, PCnet-ISA data sheet. It's free.

	A quick way to understand whether the card is a "stock" card
	is to just look at it. If it's stock, it should just have one large
	chip on it, a crystal, a small IEEE address PROM, possibly a socket
	for a boot ROM, and a connector (1, 2, or 3, depending on the media
	options offered). Note that if it's a coax card, it will have some
	transceiver stuff built onto it as well, but that should be near the
	connector and away from the PCnet-ISA.

	The PCnet-ISA is faster than the original LANCE design and
	makes better use of the available bus bandwidth. Additionally, some
	LANCE bugs were corrected and many enhancements were made."

	There is also some info regarding the LANCE chip in the file
	lance.c which is included in the standard kernel.

5.09 Multicast and Promiscuous mode

	One of the things I've been working on recently is the
	major remaining item on the ethercard feature list:
	implementing multicast and promiscuous mode hooks.
	
	At first I was planning to do it while implementing either
	the /dev/* or DDI interface, but that's not really the
	correct way to do it. We should only enable multicast or
	promiscuous modes when something wants to look at the
	packets, and shut it down when that application is
	finished, neither of which is strongly related to when the
	hardware is opened or released.
	
	I'll start by discussing promiscuous mode, which is
	conceptually easy to implement. For most hardware you
	only have to set a register bit, and from then on you get
	every packet on the wire. Well, it's almost that easy;
	for some hardware you have to shut the board (potentially
	dropping a few packet), reconfigure it, and then re-enable
	the ethercard. This is grungy and risky, but the
	alternative seems to be to have every application register
	before you open the ethercard at boot-time.
	
	OK, so that's easy, so I'll move on something that's not
	quite so obvious: Multicast. It can be done two ways:
	
	1) Use promiscuous mode, and a packet filter like the
	   Berkeley packet filter (BPF). The BPF is a pattern matching
	   stack language, where you write a program that picks out the
	   addresses you are interested in. Its advantage is that it's
	   very general and programmable. Its disadvantage is that there
	   is no general way for the kernel to avoid turning on promiscuous
	   mode and running every packet on the wire through every registered
	   packet filter. See the next section for more information on BPF.
	
	2) Using the built-in multicast filter that most etherchips have.
	
	I guess I should list what a few ethercards/chips provide:
	
	Chip/card  Promiscuous	Multicast filter
	========================================
	Seeq8001/3c501	Yes	Binary filter (1)
	3Com/3c509	Yes	Binary filter (1)
	8390		Yes	Autodin II six bit hash (2) (3)
	LANCE		Yes	Autodin II six bit hash (2) (3)
	i82586		Yes	Hidden Autodin II six bit hash (2) (4)
	
	
	(1) These cards claim to have a filter, but it's a simple
	yes/no 'accept all multicast packets', or 'accept no
	multicast packets'.
	
	(2) AUTODIN II is the standard ethernet CRC (checksum)
	polynomial. In this scheme multicast addresses are hashed
	and looked up in a hash table. If the corresponding bit
	is enabled, this packet is accepted. Ethernet packets are
	laid out so that the hardware to do this is trivial -- you
	just latch six (usually) bits from the CRC circuit (needed
	anyway for error checking) after the first six octets (the
	destination address), and use them as an index into the
	hash table (six bits == a 64-bit table).
	
	(3) These chips use the six bit hash, and must have the
	table computed and loaded by the host. This means the
	kernel must include the CRC code.
	
	(4) The 82586 uses the six bit hash internally, but it
	computes the hash table itself from a list of multicast
	addresses to accept.

	Note that none of these chips do perfect filtering, and we
	still need a middle-level module to do the final
	filtering. Also note that in every case we must keep a
	complete list of accepted multicast addresses to recompute
	the hash table when it changes.
	
	My first pass at device-level support is detailed in the
	new outline driver skeleton.c (pl14 and up.)

	It looks like the following:
	
	#ifdef HAVE_MULTICAST
	static void set_multicast_list(struct device *dev, int num_addrs,
					 void *addrs);
	#endif
	.
	.
	
	ethercard_open() {
	...
#ifdef HAVE_MULTICAST
		dev->set_multicast_list = &set_multicast_list;
	#endif
	...
	
	#ifdef HAVE_MULTICAST
	/* Set or clear the multicast filter for this adaptor.
	   num_addrs == -1	Promiscuous mode, receive all packets
	   num_addrs == 0	Normal mode, clear multicast list
	   num_addrs > 0	Multicast mode, receive normal and
				MC packets, and do best-effort filtering.
	 */
	static void
	set_multicast_list(struct device *dev, int num_addrs, void *addrs)
	{
	...

	Any comments, criticism, etc. are welcome.

	Alan Cox adds that "...in pl14, user programs can access promiscuous
	mode but not multicast mode, even though the drivers support both.
	The ifconfig program allows you to mark an interface 'promisc'."
	
5.10 The Berkeley Packet Filter (BPF)

	I'm not bitterly opposed to it, but I'm coming to the
	conclusion that the 'bpf' functionality should not be provided
	by the kernel, but should be in a (hopefully little-used)
	compatibility library.
	
	For those not in the know: 'bpf' (the Berkeley Packet Filter)
	is an mechanism for specifying to the kernel networking layers
	what packets you are interested in. It's implemented as a
	specialized stack language interpreter built into a low level
	of the networking code. An application passes a program
	written in this language to the kernel, and the kernel runs the
	program on each incoming packet. If the kernel has multiple
	'bpf' applications, each program is run on each packet.
	
	The problem is that it's difficult to deduce what kind of
	packets the application is really interested in from the packet
	filter program, so the general solution is to always run the
	filter. Imagine a program that registers a 'bpf' program to
	pick up a low data-rate stream sent to a multicast address.
	Most ethernet cards have a hardware multicast address filter
	implemented as a 64 entry hash table that ignores most unwanted
	multicast packets, so the capability exists to make this a very
	inexpensive operation. But with the BFP the kernel must switch
	the interface to promiscuous mode, receive _all_ packets, and
	run them through this filter. This is work, BTW, that's very
	difficult to account back to the process requesting the packets.

5.11 Unresolved questions / concerns

	There may be some benefit from processing packet data as it is
	transferred to and from the ethercard, especially with very fast
	processors transferring data to a slow ethercard. As I see it this
	question has multiple parts:
		1) Is there any useful processing power available, perhaps
		   during the ISA bus recovery period, or while the 8390
		   remote DMA is preparing for another transfer??
		2) Is there any useful but simple work that can be done
		   between/during each word of the copy, such as calculating
		   a CRC, or discarding obviously unwanted packets??
		3) would the complexity of an interface to do this make future
		   ethercard drivers impossible??

	There should be a better structure than Space.c - Drivers should be
	able to autoprobe for all installed ethercards rather than just
	quitting after finding the first.  I've written code to do this,
	but the constant promise (threat?) of DDI has prevented me from
	making it standard.

	A related topic is the problem of driver probes corrupting
	unrelated hardware. Even worse is a probe into a dataport that
	isn't set up to transfer data, which will freeze the machine. The
	common suggestion is a boot-time device registry that records
	already-used I/O ports and shared memory. This has been implemented
	as of pl13, see section 5.01.

6 Possible problems, and troubleshooting.

	This section tries to answer any unresolved questions, and not so
	common solutions to common problems. They are sorted on a "per
	manufacturer basis". You should have also read the relevant info.
	from section 1 about your specific card. Section 8 contains more
	general FAQ's.

6.01 Problems with NE2000 (and clones)

	"DMA address mismatch"
	======================

	Is the chip a real NatSemi 8390? (DP8390, DP83901, DP83902 or DP83905)?
	If not, some clone chips don't correctly implement the transfer
	verification register. MS-DOS drivers never do error checking,
	so it doesn't matter to them.

	Are most of the messages off by a factor of 2?
	If so:	Are you using the NE2000 in a 16 bit slot?
		Is it jumpered to use only 8 bit transfers?

	The Linux driver expects a NE2000 to be a 16 bit slot. A NE1000 can
	be in either size slot. This problem can also occur with some clones,
	notably D-Link 16 bit cards, that don't have the correct ID bytes
	in the station address PROM. [[ This should be fixed in pl12.]]

	Are you running the bus faster than 8Mhz?
	If you can change the speed (faster or slower), see if that
	makes a difference. Most NE2000 clones will run at 16Mhz, but
	some may not. Changing speed can also mask a noisy bus.

	What other devices are on the bus?
	If moving the devices around changes the reliability, then you
	have a bus noise problem -- just what that error message was
	designed to detect. Congratulations, you've probably found the
	source of other problems as well.

	Machine Hangs during Boot.
	==========================

	Problem:  The machine hangs during boot right after the "8390..."  or
		  "WD...." message. Removing the NE2000 fixes the problem.

	Solution: Change your NE2000 base address to 0x360 (or 0x340 for
		  pl12 or later kernels.) Alternatively, you can use the new
		  device registrar implemented in pl13 (see section 5.1)

	Reason:   Your NE2000 clone isn't a good enough clone. An active
		  NE2000 is a bottomless pit that will trap any driver
		  autoprobing in its space. The other ethercard drivers take
		  great pain to reset the NE2000 so that it's safe, but some
		  clones cannot be reset. Clone chips to watch out for:
		  Winbond 83C901. Changing the NE2000 to a less-popular
		  address will move it out of the way of other autoprobes,
		  allowing your machine to boot.

	Problem:  The machine hangs during the SCSI probe at boot.

	Solution: It's the same problem as above, change the
		  ethercard's address, or use the device registrar.

	Problem:  The machine hangs during the soundcard probe at boot.

	Solution: No, that's really during the silent SCSI probe, and it's
		  the same problem as above.

	"eth0: DMAing conflict in ne_block_input"
	=========================================

	This bug came from timer-based packet retransmissions. If you got a
	timer tick _during_ a ethercard RX interrupt, and timer tick tried to
	retransmit a timed-out packet, you could get a conflict. Because of
	the design of the NE2000 you would have the machine hang (exactly the
	same the NE2000-clone boot hangs).

	Early versions of the driver disabled interrupts for a long time,
	and didn't have this problem. Later versions are fixed. (ie. kernels
	after 0.99p9 should be OK.)

	NE2000 not detected at boot.
	============================

	A few people have reported a problem with detecting the Accton NE2000.
	This problem occurs only at boot-time, and the card is later detected
	at run-time by the identical code my (alpha-test) ne2k diagnostic
	program. Accton has been very responsive, but I still haven't tracked
	down what is going on. I've been unable to reproduce this problem
	with the Accton cards we purchased. If you are having this problem,
	please send me an immediate bug report. For that matter, if you have
	an Accton card send me a success report, including the type of the
	motherboard. I'm especially interested in finding out if this problem
	moves with the particular ethercard, or stays with the motherboard.
	
	Here are some things to try, as they have fixed it for some people:
	1) Change the bus speed, or just move the card to a different slot (!).
	2) Change the "I/O recovery time" parameter in the BIOS
	   chipset configuration.
	3) Make the following code change suggested by David Cutler,
	   <dave@dmitri.ucdavis.edu> to ne.c around line 150:

	    for(i = 0; i < 32 /*sizeof(SA_prom)*/; i+=2) {
	-        SA_prom[i] = inb_p(ioaddr + NE_DATAPORT);
	-        SA_prom[i+1] = inb_p(ioaddr + NE_DATAPORT);
	+        SA_prom[i] = inb(ioaddr + NE_DATAPORT);
	+        SA_prom[i+1] = inb(ioaddr + NE_DATAPORT);
	        if (SA_prom[i] != SA_prom[i+1])
	            wordlength = 1;
	    }

	Yes, this removes the delay between board accesses, something that
	would normally increase the likelihood of data corruption rather
	than decreasing it. Note that this change is already incorporated
	into pl15. If you have an older kernel, you may have to do it
	yourself.

6.02 Problems with WD80*3 cards

	Detected Non-existent Ethercard
	===============================

	Problem:  A WD80*3 is falsely detected. Removing the sound or
		  MIDI card eliminates the "detected" message.

	Solution: Update your ethercard driver: new versions include an
		  additional sanity check.

	Reason:   Some MIDI ports happen to produce the same checksum as a
		  WD ethercard.

	Error messages from the 80*3
	============================

	Problem:  You get messages such as the following with your 80*3:
			eth0: bogus packet size, status = ........
			kmalloc called with impossibly large argument (65400)
			eth0: Couldn't allocate sk_buff of size 65400
			eth0: receiver overrun

	Reason:   There is a shared memory problem.

	Solution: If the problem is sporadic, you have hardware problems.
		  Typical problems that are easy to fix are board conflicts,
		  having cache or "shadow ROM" enabled for that region, or
		  running your bus faster than 8Mhz. There are also a
		  surprising number of memory failures on ethernet cards,
		  so run a diagnostic program if you have one for your
		  ethercard.

		  If the problem is continual, and you have have to reboot
		  to fix the problem, record the boot-time probe message
		  and mail it to becker@super.org - Take particular note of
		  the shared memory location.

	Will not detect my 80x3
	=======================

	Reason:   The Mitsumi CD-ROM (mcd) driver probe at 0x300 will
		  succeed if just about *anything* is that I/O location.
		  This is bad news and needs to be a bit more robust. (pl15)
		  Once another driver registers that it "owns" an I/O
		  location, other drivers (incl. the wd80x3) are "locked
		  out" and can not probe that addr for a card.

	Solution: Recompile a new kernel without any excess drivers that
		  you aren't using, including the above mcd driver.
		  Or try moving your ethercard to a new I/O addr. Valid
		  I/O addr. for all the cards are listed in section 5.1
		  You can also point the mcd driver off in another direction
		  by a boot-time parameter (via LILO) such as:
			"mcd=0x200,12"

6.03 Problems with 3Com cards

	Choosing the Interrupt of the 3c503
	===================================

	Problem:  The 3c503 picks IRQ n at boot, but this is needed for some
		  other device which needs IRQ n. (eg. CD ROM driver, etc.)
		  Can this be fixed without compiling this into the kernel?

	Solution: The 3c503 driver probes for a free IRQ line in the order
		  {5, 9/2, 3, 4}, and it should pick a line which isn't being
		  used. The pre-pl12 (SLS 1.02) driver picked the IRQ line
		  at boot-time, and the current driver (pl12) chooses when
		  the card is open()/'ifconfig'ed. Note the "bug" noted in
		  the 3c503 section in 1.01

		  Alternately, you can fix the IRQ at boot by passing
		  parameters via LILO. The following selects IRQ9, base
		  location 0x300, <ignored value>, and if_port #1 (the
		  external transceiver).
			lilo: linux ether=9,0x300,0,1,eth0

		  The following selects IRQ3, probes for the base location,
		  <ignored value>, and the default if_port #0 (the internal
		  transceiver)
			lilo: linux ether=3,0,0,0,eth0

	"3c503: Configured interrupt number XX is out of range."
	========================================================

	Problem:  Whoever built your kernel fixed the ethercard IRQ at XX.

	Reason:   The above is truly evil, and worse than that, it is
		  not necessary. The 3c503 will autoIRQ when it gets
		  "ifconfig"ed, and pick one of IRQ{5, 2/9, 3, 4}.

	Solution: Use lilo to set the IRQ, or rebuild the kernel, enabling
		  autoIRQ by not specifying the IRQ line.

	Choosing the output of the 3c503
	================================

	Problem:  The supplied 3c503 drivers don't use the AUI (thicknet) port.
		  How does one choose it over the default thinnet port?

	Solution: The 3c503 AUI port can be selected at boot-time with 0.99pl12
		  and later. The selection is overloaded onto the low bit of
		  the currently-unused dev->rmem_start variable, so a boot-time
		  parameter of:
			lilo: linux ether=0,0,0,1,eth0
		  should work. A boot line to force IRQ 5, port base 0x300,
		  and use an external transceiver is:
			lilo: linux ether=5,0x300,0,1,eth0

7 Networking with a laptop computer

	There are currently only a few ways to put your laptop on a network.
	You can use the SLIP code (and run at serial line speeds);
	you can buy one of the few laptops that come with a NE2000-compatible
	ethercard or PCMCIA slot built-in; you can get a laptop with a
	docking station and plug in an ISA ethercard; or you can use a
	parallel port Ethernet adapter such as the D-Link DE-600.

7.01 Option 1 -- using SLIP

	This is the cheapest solution, but by far the most difficult. Also,
	you will not get very high transmission rates. Since SLIP is not
	really related to ethernet cards, it will not be discussed further
	here. See the NET-2 HOWTO.

7.02 Option 2 -- Built in NE2000 compatible or PCMCIA Ethercard.

	The second solution severely limits your laptop choices and is fairly
	expensive. Be sure to read the specifications carefully, you may find
	that you will have to buy an additional non-standard transceiver to
	actually put the machine on a network.

	As this area of Linux development is fairly young, I'd suggest
	that you join the LAPTOPS mailing channel. See section 0.02
	which describes how to join a mailing list channel. Try and
	determine exactly what hardware you have (ie. card manufacturer,
	PCMCIA chip controller manufacturer) and then ask on the LAPTOPS
	channel. Regardless, don't expect things to be all that simple.
	Expect to have to fiddle around a bit, and patch kernels, etc.
	Maybe someday you will be able to type "make config" 8-)

	There is a number of programs on tsx-11.mit.edu in
	/pub/linux/packages/laptops/ that you may find useful. These
	range from PCMCIA Ethercard drivers to programs that communicate
	with the PCMCIA controller chip. Note that these drivers are
	usually tied to a specific PCMCIA chip (ie. the intel 82365
	or the TCIC/2) On a brighter note, I know that people have used the
	Linksys/D-Link 650 PCMCIA Ethernet PC Card with both controller
	chipsets, so it *can* be done. I have also seen reports of
	people using the IBM Credit Card Adapter for Ethernet with the
	intel 82365 chip. This is all just from following the LAPTOPS
	channel.

	The 3c589 from 3Com is supposed to look a lot like a 3c509.

	Anyway, the PCMCIA driver problem isn't specific to the Linux world.
	It's been a real disaster in the MS-DOS world. In that world
	people expect the hardware to work if they just follow the manual.
	They might not expect it to interoperate with any other hardware
	or software, or operate optimally, but they do expect that the
	software shipped with the product will function. Many PCMCIA
	adaptors don't pass this test.

7.03 Option 3 -- ISA Ethercard in the Docking Station.

	I recommend the third solution. Docking stations for laptops typically
	cost about $250 and provide two full-size ISA slots, two serial and one
	parallel port. Most (all?) docking stations are powered off of the
	laptop's batteries, and a few allow adding extra batteries in the
	docking station if you use short ISA cards. You can add an inexpensive
	ethercard and enjoy full-speed ethernet performance.

7.04 Option 4 -- Pocket / parallel port adaptors.

	The "pocket" ethernet adaptors may also fit your need.
	Until recently they actually costed more than a docking station and
	cheap ethercard, and most tie you down with a wall-brick power supply.
	At present, you can choose from the D-Link, or the RealTek adaptor.
	Most other companies, especially Xircom, treat the programming
	information as a trade secret, so support will likely be slow in
	coming.

	You can sometimes avoid the wall-brick with the adaptors by buying
	or making a cable that draws power from the laptop's keyboard
	port. (This is mentioned in the info. for the AT-Lan-Tec unit.)

	The keyboard pinouts (5 pin DIN) are as follows:

		Signal/Function			Pin #
		---------------			-----
		KEYCLK (clock)			1
		KEYDAT (data)			2
		N/C				3
		Ground				4
		+5 V				5

	A quick check with a voltmeter will verify which pins are 4 and 5
	if you are not sure.
8 Frequently asked questions

	Here are some of the more frequently asked questions about using
	Linux with an Ethernet connection. Some of the more specific
	questions are sorted on a "per manufacturer basis" and are listed
	in the "Troubleshooting" section. (section 6). However, since this
	document is basically "old" by the time you get it, any "new" problems
	will not appear here instantly. For these, I suggest that you make
	efficient use of your newsreader. For example, nn users would type
		nn -xX -s'3c'
	to get all the news articles in your subscribed list that have
	"3c" in the subject. (ie. 3com, 3c509, 3c503, etc.)
	The moral: Read the man page for your newsreader.
	
8.01 Just the FAQ's ma'am -- just the FAQ's.

	Q: I heard that there is an alpha driver available for my card.
	   Where can I get it?

	A: Assuming that it is a djb driver, it will be on ftp.super.org
	   in the /pub/linux/ area. Things change here quite frequently,
	   so just look around for it. There is usually only about 3
	   subdirs, so you should be able to find it. Now, if it really
	   is an alpha, or pre-alpha driver, then please treat it as
	   such. In other words, don't complain because you can't figure
	   out what to do with it. If you can't figure out how to install
	   it, then you probably shouldn't be testing it. Also, if it brings
	   your machine down, don't complain. Instead, send us a well
	   documented bug report, or even better, a patch!

	Q: Is there token ring support for Linux?

	A: No, there is no token ring support in Linux. To support token ring
	   requires more than only a writing a device driver, it also requires
	   writing the source routing routines for token ring. Given that
	   token ring is expensive, not fast, and will probably be swept away
	   by 100baseVG in a few months, it doesn't seem worth it to write
	   a driver. In case anyone wants to, I looked at writing a token ring
	   device driver, and concluded that the hardware interface
	   wasn't too difficult to do, but writing the support for source
	   routing would take significantly longer than I was willing to spend
	   on an expensive and dying technology.

	   Alan Cox adds: "It will require [...] changes to the bottom socket
	   layer to support 802.2 and 802.2 based TCP/IP. Don't expect
	   anything soon."

	Q: Is there FDDI support for Linux?

	A: No, there is no Linux driver for any FDDI boards. I come from a
	   place with supercomputers, so an external observer might think
	   FDDI would be high on my list. But FDDI never delivered end-to-end
	   throughput that would justify its cost, and it seems to be a nearly
	   abandoned technology now that 100base{X,Anynet} seems imminent.
	   (And yes, I know you can now get FDDI boards for <$1K. That
	   seems to be a last-ditch effort to get some return on the
	   development investment. Where is the next generation of FDDI
	   going to come from?)

	Q: Can I link 10BaseT (RJ45) based systems together without a hub?

	A: You can link 2 machines easily, but no more than that, without
	   extra devices/gizmos. See section 4 on wiring -- it explains
	   how to do it. And no, you can't hack together a hub just by
	   crossing a few wires and stuff. It's pretty much impossible 
	   to do the collision signal right without duplicating a hub.

	Q: Is there IPX or Novell support available for Linux?

	A: Alan Cox writes: "The novell protocols are available from novell
	   for various amounts. IPX is freely documented. SPX is about $1000
	   but I'm told Xerox SPP is identical. _PLEASE_ has anyone got any
	   freely distributable Xerox SPP code/documentation? The novell
	   server spec costs you $15000 + royalties providing you only
	   want to write a client, or $30000 + royalties otherwise. Needless
	   to say the final output has to be binary only and subject to a
	   novell license. Reading their license rules by my interpretation
	   its also impossible for us to do because you would seem to have
	   to bar disassembly of your final result, which is not allowed
	   in the EEC.

	   Bits of NCP are known, and I hope eventually enough will be known
	   to write limited NCP support into Linux, for the moment I'm poking
	   around at IPX, tho this will have to wait until the new network
	   code is finished.

	   An Alpha test IPX protocol layer is available from me (Alan)
	   for pl14 or higher. People are also exploring the issue of NCP and
	   the new Dr Dobbs journal article on the innards of netware has
	   provided a core of good information."

	   As an alternative, Miquel van Smoorenburg suggests the following:
	   "It _is_ possible to set up a dedicated PC running both novell and
	   the PD SOSS server and let it gateway from NFS to novell. This way
	   it is possible to mount the Novell drives on the Unix client.

	   SOSS is a PD (perhaps with some restrictions, but freely available)
	   NFS server for DOS. It includes the PC/IP TCP/IP implementation
	   and runs on a packet driver. I have run both a Novell client
	   (with PDIPX, a Packet Driver IPX) and this SOSS server together
	   successfully."

	   You can get "Stan's Own Server System" from the following location:
		hilbert.wharton.upenn.edu:pub/tcpip/soss.zip
	   Note that this version has the IP bugs fixed and the subdirs
	   with extensions bug fixed. Some of the soss.zoo archives do
	   not contain these fixes.

	Q: What needs to be done so that Linux can run two ethernet cards?

	A: The easiest solution is to get 0.99pl13 or newer, as the hooks for
	   multiple ethercards are all there.
	   You can enable additional ethercards with LILO parameters such as:

		lilo: linux ether=5,0x300,0,1,eth0 ether=15,0x280,eth1

	   These boot time arguments can be made permanent so that you
	   don't have to re-enter them every time. See the LILO manual.

	Q: Okay, I can run 2 cards -- can I run Linux as a gateway 
	   between two networks?

	A: This is really a question for the NET-HOWTO, but it is 
	   answered here anyways: Charles Hedrick (aka Mr. Slip)
	   had this to say:

	   "Yes, however I'm a bit nervous about doing it. The problem isn't
	   functionality -- there's IP forwarding code, and as far as I know,
	   it works. Some people do use it. However routers need to be
	   particularly careful to avoid creating network problems such as
	   "meltdowns." The Linux IP layer doesn't have quite enough of these
	   protective features. It will only cause trouble if other hosts on
	   your network are misconfigured, and even then it probably won't
	   cause much trouble (assuming that only systems actually acting as
	   gateways are built with IP_FORWARD enabled). But I'd still rather
	   use a router that met all of the requirements of the host and
	   router requirements in the RFC's. (Note that not all other Unix
	   implementations do either. I'm concerned about things like not
	   sending ICMP responses to messages that arrive as media 
	   broadcasts. 386BSD looks OK, but older BSD-based implementations
	   often didn't do all of these checks.)

	   It depends a lot on what the network is like and how critical it is.
	   For a home setup with a couple of hosts, I see no problem at all.
	   But I would not consider using Linux as a router on a large
	   campus network at the moment. I still think that by release 1.0,
	   Linux will be a reasonably well-behaved host. But I think use
	   as a router in critical situations should wait until somebody
	   has checked the ip and icmp modules for compliance with RFC 1009
	   and a few other specs."

	Q: I have /dev/eth0 as a link to /dev/xxx. Is this right?

	A: Contrary to what you have heard, the files in /dev/* are not used.
	   I originally thought that they might be an OK idea. I've since
	   concluded that they won't work, at least in the documented form.

	Q: Should I disable trailers when I "ifconfig" my ethercard?

	A: You can't disable trailers, and you shouldn't want to.
	   'Trailers' are a hack to avoid data copying in the
	   networking layers. The idea was to use a trivial 
	   fixed-size header of size 'H', put the variable-size header 
	   info at the end of the packet, and allocate all packets
	   'H' bytes before the start of a page. While it was a good
	   idea, it turned out to not work well in practice.
	   If someone suggests the use of '-trailers', note that it
	   is the equivalent of sacrificial goats blood. It won't do
	   anything to solve the problem, but if problem fixes itself then
	   someone can claim deep magical knowledge.

9 Miscellaneous.

	Any other associated stuff that didn't fit in anywhere else gets
	dumped here. It may not be relevant, and it may not be of general
	interest but it is here anyway.

9.01 Bad Vendors

	#define SOAPBOX

	There used to be some horror stories here about dealings with
	Cabletron and Xircom. They were pretty ugly and gruesome.
	Basically these companies are the ethernet equivalent of
	what Diamond is to XFree86. They do not want to release
	vital information on low-level programming of their hardware.
	For something like Linux, where the source code for everything
	is out in the open, this makes their hardware difficult or
	impossible to use. However, like Diamond, when confronted
	with the fact that they are losing sales from Linux/BSD users,
	they basically shrug it off, saying that it is only a small
	percentage of the total sales. If you can afford the time,
	drop these vendors a note (via e-mail or snail-mail) and tell
	them politely that the fact that they don't support open
	software systems such as Linux has forced you to exclude them
	from the vendors that you are purchasing hardware from. It may
	not make any immediate difference, but it might make you feel
	better. Besides, a few seconds of your time is a cheap price
	to pay for *all* that free Linux software you are using. 8-)

	#undef SOAPBOX

9.02 Closing

	If you have found any glaring typos, or outdated info in this
	document, please let one of us know. It's getting big, and it
	is easy to overlook stuff.

	Paul Gortmaker		<gpg109@rsphy1.anu.edu.au>
	Donald J. Becker	<becker@super.org>

