arcnet.txt

嵌入式系统设计与实验教材二源码linux内核移植与编译

	networks.
	
Windows 95: Tools are included with Win95 that let you use either the LANMAN
	style network drivers (NDIS) or Novell drivers (ODI) to handle your
	ARCnet packets.  If you use ODI, you'll need to use the 'arc0'
	device with Linux.  If you use NDIS, then try the 'arc0e' device. 
	See the "Multiprotocol Support" section below if you need arc0e,
	you're completely insane, and/or you need to build some kind of
	hybrid network that uses both encapsulation types.

OS/2: I've been told it works under Warp Connect with an ARCnet driver from
	SMC.  You need to use the 'arc0e' interface for this.  If you get
	the SMC driver to work with the TCP/IP stuff included in the
	"normal" Warp Bonus Pack, let me know.

	ftp.microsoft.com also has a freeware "Lan Manager for OS/2" client
	which should use the same protocol as WfWg does.  I had no luck
	installing it under Warp, however.  Please mail me with any results.

NetBSD/AmiTCP: These use an old version of the Internet standard ARCnet
	protocol (RFC1051) which is compatible with the Linux driver v2.10
	ALPHA and above using the arc0s device. (See "Multiprotocol ARCnet"
	below.)  ** Newer versions of NetBSD apparently support RFC1201.


Using Multiprotocol ARCnet
--------------------------

The ARCnet driver v2.10 ALPHA supports three protocols, each on its own
"virtual network device":

	arc0  - RFC1201 protocol, the official Internet standard which just
		happens to be 100% compatible with Novell's TRXNET driver. 
		Version 1.00 of the ARCnet driver supported _only_ this
		protocol.  arc0 is the fastest of the three protocols (for
		whatever reason), and allows larger packets to be used
		because it supports RFC1201 "packet splitting" operations. 
		Unless you have a specific need to use a different protocol,
		I strongly suggest that you stick with this one.
		
	arc0e - "Ethernet-Encapsulation" which sends packets over ARCnet
		that are actually a lot like Ethernet packets, including the
		6-byte hardware addresses.  This protocol is compatible with
		Microsoft's NDIS ARCnet driver, like the one in WfWg and
		LANMAN.  Because the MTU of 493 is actually smaller than the
		one "required" by TCP/IP (576), there is a chance that some
		network operations will not function properly.  The Linux
		TCP/IP layer can compensate in most cases, however, by
		automatically fragmenting the TCP/IP packets to make them
		fit.  arc0e also works slightly more slowly than arc0, for
		reasons yet to be determined.  (Probably it's the smaller
		MTU that does it.)
		
	arc0s - The "[s]imple" RFC1051 protocol is the "previous" Internet
		standard that is completely incompatible with the new
		standard.  Some software today, however, continues to
		support the old standard (and only the old standard)
		including NetBSD and AmiTCP.  RFC1051 also does not support
		RFC1201's packet splitting, and the MTU of 507 is still
		smaller than the Internet "requirement," so it's quite
		possible that you may run into problems.  It's also slower
		than RFC1201 by about 25%, for the same reason as arc0e.
		
		The arc0s support was contributed by Tomasz Motylewski
		and modified somewhat by me.  Bugs are probably my fault.

You can choose not to compile arc0e and arc0s into the driver if you want -
this will save you a bit of memory and avoid confusion when eg. trying to
use the "NFS-root" stuff in recent Linux kernels.

The arc0e and arc0s devices are created automatically when you first
ifconfig the arc0 device.  To actually use them, though, you need to also
ifconfig the other virtual devices you need.  There are a number of ways you
can set up your network then:


1. Single Protocol.

   This is the simplest way to configure your network: use just one of the
   two available protocols.  As mentioned above, it's a good idea to use
   only arc0 unless you have a good reason (like some other software, ie.
   WfWg, that only works with arc0e).
   
   If you need only arc0, then the following commands should get you going:
   	ifconfig arc0 MY.IP.ADD.RESS
   	route add MY.IP.ADD.RESS arc0
   	route add -net SUB.NET.ADD.RESS arc0
   	[add other local routes here]
   	
   If you need arc0e (and only arc0e), it's a little different:
   	ifconfig arc0 MY.IP.ADD.RESS
   	ifconfig arc0e MY.IP.ADD.RESS
   	route add MY.IP.ADD.RESS arc0e
   	route add -net SUB.NET.ADD.RESS arc0e
   
   arc0s works much the same way as arc0e.


2. More than one protocol on the same wire.

   Now things start getting confusing.  To even try it, you may need to be
   partly crazy.  Here's what *I* did. :) Note that I don't include arc0s in
   my home network; I don't have any NetBSD or AmiTCP computers, so I only
   use arc0s during limited testing.

   I have three computers on my home network; two Linux boxes (which prefer
   RFC1201 protocol, for reasons listed above), and one XT that can't run
   Linux but runs the free Microsoft LANMAN Client instead.

   Worse, one of the Linux computers (freedom) also has a modem and acts as
   a router to my Internet provider.  The other Linux box (insight) also has
   its own IP address and needs to use freedom as its default gateway.  The
   XT (patience), however, does not have its own Internet IP address and so
   I assigned it one on a "private subnet" (as defined by RFC1597).

   To start with, take a simple network with just insight and freedom. 
   Insight needs to:
   	- talk to freedom via RFC1201 (arc0) protocol, because I like it
	  more and it's faster.
	- use freedom as its Internet gateway.
	
   That's pretty easy to do.  Set up insight like this:
   	ifconfig arc0 insight
   	route add insight arc0
   	route add freedom arc0	/* I would use the subnet here (like I said
					to to in "single protocol" above),
   					but the rest of the subnet
   					unfortunately lies across the PPP
   					link on freedom, which confuses
   					things. */
   	route add default gw freedom
   	
   And freedom gets configured like so:
   	ifconfig arc0 freedom
   	route add freedom arc0
   	route add insight arc0
   	/* and default gateway is configured by pppd */
   	
   Great, now insight talks to freedom directly on arc0, and sends packets
   to the Internet through freedom.  If you didn't know how to do the above,
   you should probably stop reading this section now because it only gets
   worse.

   Now, how do I add patience into the network?  It will be using LANMAN
   Client, which means I need the arc0e device.  It needs to be able to talk
   to both insight and freedom, and also use freedom as a gateway to the
   Internet.  (Recall that patience has a "private IP address" which won't
   work on the Internet; that's okay, I configured Linux IP masquerading on
   freedom for this subnet).
   
   So patience (necessarily; I don't have another IP number from my
   provider) has an IP address on a different subnet than freedom and
   insight, but needs to use freedom as an Internet gateway.  Worse, most
   DOS networking programs, including LANMAN, have braindead networking
   schemes that rely completely on the netmask and a 'default gateway' to
   determine how to route packets.  This means that to get to freedom or
   insight, patience WILL send through its default gateway, regardless of
   the fact that both freedom and insight (courtesy of the arc0e device)
   could understand a direct transmission.
   
   I compensate by giving freedom an extra IP address - aliased 'gatekeeper'
   - that is on my private subnet, the same subnet that patience is on.  I
   then define gatekeeper to be the default gateway for patience.
   
   To configure freedom (in addition to the commands above):
   	ifconfig arc0e gatekeeper
   	route add gatekeeper arc0e
   	route add patience arc0e
   
   This way, freedom will send all packets for patience through arc0e,
   giving its IP address as gatekeeper (on the private subnet).  When it
   talks to insight or the Internet, it will use its "freedom" Internet IP
   address.
   
   You will notice that we haven't configured the arc0e device on insight. 
   This would work, but is not really necessary, and would require me to
   assign insight another special IP number from my private subnet.  Since
   both insight and patience are using freedom as their default gateway, the
   two can already talk to each other.
   
   It's quite fortunate that I set things up like this the first time (cough
   cough) because it's really handy when I boot insight into DOS.  There, it
   runs the Novell ODI protocol stack, which only works with RFC1201 ARCnet. 
   In this mode it would be impossible for insight to communicate directly
   with patience, since the Novell stack is incompatible with Microsoft's
   Ethernet-Encap.  Without changing any settings on freedom or patience, I
   simply set freedom as the default gateway for insight (now in DOS,
   remember) and all the forwarding happens "automagically" between the two
   hosts that would normally not be able to communicate at all.
   
   For those who like diagrams, I have created two "virtual subnets" on the
   same physical ARCnet wire.  You can picture it like this:
   
                                                    
          [RFC1201 NETWORK]                   [ETHER-ENCAP NETWORK]
      (registered Internet subnet)           (RFC1597 private subnet)
  
                             (IP Masquerade)
          /---------------\         *            /---------------\
          |               |         *            |               |
          |               +-Freedom-*-Gatekeeper-+               |
          |               |    |    *            |               |
          \-------+-------/    |    *            \-------+-------/
                  |            |                         |
               Insight         |                      Patience
                           (Internet)



It works: what now?
-------------------

Send mail describing your setup, preferably including driver version, kernel
version, ARCnet card model, CPU type, number of systems on your network, and
list of software in use to me at the following address:
	[e-mail]

I do send (sometimes automated) replies to all messages I receive.  My email
can be weird (and also usually gets forwarded all over the place along the
way to me), so if you don't get a reply within a reasonable time, please
resend.


It doesn't work: what now?
--------------------------

Do the same as above, but also include the output of the ifconfig and route
commands, as well as any pertinent log entries (ie. anything that starts
with "arcnet:" and has shown up since the last reboot) in your mail.

If you want to try fixing it yourself (I strongly recommend that you mail me
about the problem first, since it might already have been solved) you may
want to try some of the debug levels available.  For heavy testing on
D_DURING or more, it would be a REALLY good idea to kill your klogd daemon
first!  D_DURING displays 4-5 lines for each packet sent or received.  D_TX,
D_RX, and D_SKB actually DISPLAY each packet as it is sent or received,
which is obviously quite big.

Starting with v2.40 ALPHA, the autoprobe routines have changed
significantly.  In particular, they won't tell you why the card was not
found unless you turn on the D_INIT_REASONS debugging flag.

Once the driver is running, you can run the arcdump shell script (available
from me or in the full ARCnet package, if you have it) as root to list the
contents of the arcnet buffers at any time.  To make any sense at all out of
this, you should grab the pertinent RFCs. (some are listed near the top of
arcnet.c).  arcdump assumes your card is at 0xD0000.  If it isn't, edit the
script.

Buffers 0 and 1 are used for receiving, and Buffers 2 and 3 are for sending. 
Ping-pong buffers are implemented both ways.

If your debug level includes D_DURING and you did NOT define SLOW_XMIT_COPY,
the buffers are cleared to a constant value of 0x42 every time the card is
reset (which should only happen when you do an ifconfig up, or when Linux
decides that the driver is broken).  During a transmit, unused parts of the
buffer will be cleared to 0x42 as well.  This is to make it easier to figure
out which bytes are being used by a packet.

You can change the debug level without recompiling the kernel by typing:
	ifconfig arc0 down metric 1xxx
	/etc/rc.d/rc.inet1
where "xxx" is the debug level you want.  For example, "metric 1015" would put
you at debug level 15.  Debug level 7 is currently the default.

Note that the debug level is (starting with v1.90 ALPHA) a binary
combination of different debug flags; so debug level 7 is really 1+2+4 or
D_NORMAL+D_EXTRA+D_INIT.  To include D_DURING, you would add 16 to this,
resulting in debug level 23.

If you don't understand that, you probably don't want to know anyway. 
E-mail me about your problem.


I want to send money: what now?
-------------------------------

Go take a nap or something.  You'll feel better in the morning.