🚀 go-pugleaf

Archive-Name: linux/howto/ethernet/part2
Last-modified: 20 Oct 94


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

  And if you just want to verify that this is the case, you can reach
  Xircom at 1-800-874-7875 or +1-818-878-7600.


  3.25.1.  PE1, PE2, PE3-10B*


  Status -- Not Supported

  Not to get your hopes up, but if you have one of these parallel port
  adaptors, you may be able to use it in the DOS emulator with the
  Xircom-supplied DOS drivers. You will have to allow DOSEMU access to
  your parallel port, and will probably have to play with SIG (DOSEMU's
  Silly Interrupt Generator). I have no idea if this will work, but if
  you have any success with it, let me know, and I will include it here.


  3.26.  Zenith



  3.26.1.  Z-Note


  Status -- Supported

  The built-in Z-Note network adaptor is based on the Intel i82593 using
  two DMA channels. There is an (alpha?) driver available in the present
  kernel version. As with all notebook and pocket adaptors, it is under
  the `Pocket and portable adaptors' section when running make config.
  See ``Programming the Intel chips'' for more technical information.
  Also note that the IBM ThinkPad 300 is compatible with the Z-Note.


  4.  Clones of popular Ethernet cards.


  Due to the popular design of some cards, different companies will make
  `clones' or replicas of the original card. However, one must be
  careful, as some of these clones are not 100 % compatible, and can be
  troublesome. Some common problems with `not-quite-clones' are noted in
  ``the FAQ section''.

  This section used to have a listing of a whole bunch of clones that
  were reported to work, but seeing as nearly all clones will work, it
  makes more sense to list the ones that don't work 100 % .


  4.1.  NE2000 Clones with Problems


  Here is a list of some of the NE-2000 clones that are known to have
  various problems. Most of them aren't fatal. In the case of the ones
  listed as `bad clones' -- this usually indicates that the cards don't
  have the two NE2000 identifier bytes. NEx000-clones have a Station
  Address PROM (SAPROM) in the packet buffer memory space.  NE2000
  clones have 0x57,0x57 in bytes 0x0e,0x0f of the SAPROM, while other
  supposed NE2000 clones must be detected by their SA prefix.

  Accton NE2000 -- might not get detected at boot, see ``ne2000
  problems''.

  Aritsoft LANtastic AE-2 -- OK, but has flawed error-reporting
  registers.

  AT-LAN-TEC NE2000 -- clone uses Winbond chip that traps SCSI drivers

  Cabletron E10**, E20**, E10**-x, E20**-x -- bad clones, but the driver
  checks for them. See ``E10**''.

  D-Link Ethernet II -- bad clones, but the driver checks for them. See
  ``DE-100 / DE-200''.

  DFI DFINET-300, DFINET-400 -- bad clones, but the driver checks for
  them. See ``DFI-300 / DFI-400''


  4.2.  WD8013 Clones with Problems


  I haven't heard of any bad clones of these cards, except for some
  chamelion-type cards that can be set to look like a ne2000 card or a
  wd8013 card. There is really no need to purchase one of these `double-
  identity' cards anyway.


  5.  Cables, Coax, Twisted Pair

  If you are starting a network from scratch, it's considerably less
  expensive to use thin ethernet, RG58 co-ax cable with BNC connectors,
  than old-fashioned thick ethernet, RG-5 cable with N connectors, or
  10baseT, twisted pair telco-style cables with RJ-45 eight wire `phone'
  connectors. See ``Type of cable...'' for an introductory look at
  cables.


  5.1.  Thin Ethernet (thinnet)


  Thin ethernet is the `ether of choice'. The cable is inexpensive. If
  you are making your own cables solid-core RG58A is $0.09/ft. and
  stranded RG58AU is $0.15/ft. Twist-on BNC connectors are < $2 ea., and
  other misc. pieces are similarly inexpensive. It is essential that you
  properly terminate each end of the cable with 50 ohm terminators, so
  budget $2 ea. for a pair. It's also vital that your cable have no
  `stubs' -- the `T' connectors must be attached directly to the
  ethercards. The only drawback is that if you have a big loop of
  machines connected together, and some bonehead breaks the loop by
  taking one cable off the side of his tee, the whole network goes down
  because it sees an infinite impedance (open circuit) instead of the
  required 50 ohm termination. Note that you can remove the tee piece
  from the card itself without killing the whole subnet, as long as you
  don't remove the cables from the tee itself. Of course this will
  disturb the machine that you pull the actual tee off of. 8-) And if
  you are doing a small network of two machines, you *still* need the
  tees and the 50 ohm terminators -- you *can't* just cable them
  together!


  5.2.  Twisted Pair


  Twisted pair networks require active hubs, which start around $200,
  and the raw cable cost can actually be higher than thinnet. They are
  usually sold using the claim that you can use your existing telephone
  wiring, but it's a rare installation where that turns out to be the
  case. The claim that you can upgrade to higher speeds is also suspect,
  as most proposed schemes use higher-grade (read $$) cable and more
  sophisticated termination ($$$) than you would likely install on
  speculation. New gizmos are floating around which allow you to daisy-
  chain machines together, and the like. For example, Falleron sells
  EtherWave adaptors and transceivers. This device allows multiple
  10baseT devices to be daisy-chained. They also sell a 3c509 clone that
  includes the EtherWave transceiver.  The drawback is that it's more
  expensive and less reliable than a cheap ($100-$150) mini-hub and
  another ethercard.  IMO, you should either go for the hub approach or
  switch over to 10base2 thinnet.

  On the other hand, hubs are rapidly dropping in price, all 100Mb/sec
  ethernet proposals use twisted pair, and most new business
  installations use twisted pair. (This is probably to avoid the problem
  with idiots messing with the BNC's as described above.)

  If you are only connecting two machines, it is possible to avoid using
  a hub, by swapping the Rx and Tx pairs (1-2 and 3-6).

  Also, Russ Nelson adds that `New installations should use Category 5
  wiring. Anything else is a waste of your installer's time, as 100Base-
  whatever is going to require Cat 5.'
  5.3.  Thick Ethernet

  Thick ethernet is mostly obsolete, and is usually used only to remain
  compatible with an existing implementation. You can stretch the rules
  and connect short spans of thick and thin ethernet together with a
  passive $3 N-to-BNC connector, and that's often the best solution to
  expanding an existing thicknet. A correct (but expensive) solution is
  to use a repeater in this case.

  6.  Technical Information


  For those who want to play with the present drivers, or try to make up
  their own driver for a card that is presently unsupported, this
  information should be useful. If you do not fall into this category,
  then perhaps you will want to skip this section.


  6.1.  Probed Addresses



  While trying to determine what ethernet card is there, the following
  addresses are autoprobed, assuming the type and specs of the card have
  not been set in the kernel. The file names below are in
  /usr/src/linux/drivers/net/


  ______________________________________________________________________
          3c501.c         0x280, 0x300
          3c503.c:        0x300, 0x310, 0x330, 0x350, 0x250, 0x280, 0x2a0, 0x2e0
          3c505.c:        0x300, 0x280, 0x310
          3c507.c:        0x300, 0x320, 0x340, 0x280
          3c509.c:        Special ID Port probe
          apricot.c       0x300
          at1700.c:       0x300, 0x280, 0x380, 0x320, 0x340, 0x260, 0x2a0, 0x240
          atp.c:          0x378, 0x278, 0x3bc
          depca.c         0x300, 0x200
          d_link.c:       0x378
          eexpress.c:     0x300, 0x270, 0x320, 0x340
          hp.c:           0x300, 0x320, 0x340, 0x280, 0x2C0, 0x200, 0x240
          hp-plus.c       0x200, 0x240, 0x280, 0x2C0, 0x300, 0x320, 0x340
          lance.c:        0x300, 0x320, 0x340, 0x360
          ne.c:           0x300, 0x280, 0x320, 0x340, 0x360
          ni52.c          0x300, 0x280, 0x360, 0x320, 0x340
          ni65.c          0x300, 0x320, 0x340, 0x360
          smc-ultra.c:    0x200, 0x220, 0x240, 0x280, 0x300, 0x340, 0x380
          wd.c:           0x300, 0x280, 0x380, 0x240
  ______________________________________________________________________



  There are some NE2000 clone ethercards out there that are waiting
  black holes for autoprobe drivers. While many NE2000 clones are safe
  until they are enabled, some can't be reset to a safe mode.  These
  dangerous ethercards will hang any I/O access to their `dataports'.
  The typical dangerous locations are:

  ______________________________________________________________________
          Ethercard jumpered base     Dangerous locations (base + 0x10 - 0x1f)
                  0x300 *                         0x310-0x317
                  0x320                           0x330-0x337
                  0x340                           0x350-0x357
                  0x360                           0x370-0x377
  ______________________________________________________________________

  * The 0x300 location is the traditional place to put an ethercard, but
  it's also a popular place to put other devices (often SCSI
  controllers). The 0x320 location is often the next one chosen, but
  that's bad for for the AHA1542 driver probe. The 0x360 location is
  bad, because it conflicts with the parallel port at 0x378.

  To avoid these lurking ethercards, here are the things you can do:


  o  Probe for the device's BIOS in memory space. This is easy and
     always safe, but it only works for cards that always have BIOSes,
     like primary SCSI controllers.

  o  Avoid probing any of the above locations until you think you've
     located your device. The NE2000 clones have a reset range from
     <base>+0x18 to <base>+0x1f that will read as 0xff, so probe there
     first if possible. It's also safe to probe in the 8390 space at
     <base>+0x00 - <base>+0x0f, but that area will return quasi-random
     values

  o  If you must probe in the dangerous range, for instance if your
     target device has only a few port locations, first check that there
     isn't an NE2000 there. You can see how to do this by looking at the
     probe code in /usr/src/linux/net/inet/ne.c

  o  Use the `reserve' boot time argument to protect volatile areas from
     being probed. See the information on using boot time arguments with
     LILO in ``The reserve command''


  6.2.  Skeleton / prototype driver



  OK. So you have decided that you want to write a driver for the Foobar
  Ethernet card, as you have the programming information, and it hasn't
  been done yet. (...these are the two main requirements ;-) You can use
  the skeleton network driver that is provided with the Linux kernel
  source tree. It can be found in the file
  /usr/src/linux/drivers/net/skeleton.c as of 0.99pl15, and later.

  It's also very useful to look at the Crynwr (nee Clarkson) driver for
  your target ethercard, if it's available. Russ Nelson
  nelson@crynwr.com has been actively updating and writing these, and he
  has been very helpful with his code reviews of the current Linux
  drivers.


  6.3.  Driver interface to the kernel


  Here are some notes that may help when trying to figure out what the
  code in the driver segments is doing, or perhaps what it is supposed
  to be doing.












  ______________________________________________________________________
          int ethif_init(struct device *dev)
          {
              ...
                  dev->send_packet = &ei_send_packet;
                  dev->open = &ei_open;
                  dev->stop = &ei_close;
                  dev->hard_start_xmit = &ei_start_xmit;
                  ...
          }

          int ethif_init(struct device *dev)
  ______________________________________________________________________



  This function is put into the device structure in Space.c. It is
  called only at boot time, and returns `0' iff the ethercard `dev'
  exists.


  ______________________________________________________________________
          static int ei_open(struct device *dev)
          static int ei_close(struct device *dev)
  ______________________________________________________________________



  This routine opens and initializes the board in response to an socket
  ioctl() usually called by `ifconfig'. It is commonly stuffed into the
  `struct device' by ethif_init().

  The inverse routine is ei_close(), which should shut down the
  ethercard, free the IRQs and DMA channels if the hardware permits, and
  turn off anything that will save power (like the transceiver).


  ______________________________________________________________________
          static int ei_start_xmit(struct sk_buff *skb, struct device *dev)
                  dev->hard_start_xmit = &ei_start_xmit;
  ______________________________________________________________________



  This routine puts packets to be transmitted into the hardware. It is
  usually stuffed into the `struct device' by ethif_init().

  When the hardware can't accept additional packets it should set the
  dev->tbusy flag. When additional room is available, usually during a
  transmit-complete interrupt, dev->tbusy should be cleared and the
  higher levels informed with mark_bh(INET_BH).


  ______________________________________________________________________
              if (dev_rint(buffer, length, is_skb ? IN_SKBUFF : 0, dev))
                     stats->rx_dropped++;
  ______________________________________________________________________



  A received packet is passed to the higher levels using dev_rint().  If
  the unadorned packet data in a memory buffer, dev_rint will copy it
  into a `skbuff' for you. Otherwise a new skbuff should be kmalloc()ed,
  filled, and passed to dev_rint() with the IN_SKBUFF flag.


  ______________________________________________________________________
          int s=socket(AF_INET,SOCK_PACKET,htons(ETH_P_ALL));
  ______________________________________________________________________



  Gives you a socket receving every protocol type. Do recvfrom() calls
  to it and it will fill the sockaddr with device type in sa_family and
  the device name in the sa_data array. I don't know who originally
  invented SOCK_PACKET for Linux (its been in for ages) but its superb
  stuff.  You can use it to send stuff raw too (both only as root).



  6.4.  Interrupts and Linux


  There are two kinds of interrupt handlers in Linux: fast ones and slow
  ones. You decide what kind you are installing by the flags you pass to
  irqaction(). The fast ones, such as the serial interrupt handler, run
  with _all_ interrupts disabled. The normal interrupt handlers, such as
  the one for ethercard drivers, runs with other interrupts enabled.

  There is a two-level interrupt structure. The `fast' part handles the
  device register, removes the packets, and perhaps sets a flag.  After
  it is done, and interrupts are re-enabled, the slow part is run if the
  flag is set.

  The flag between the two parts is set by:


       mark_bh(INET_BH);


  Usually this flag is set within dev_rint() during a received-packet
  interrupt, and set directly by the device driver during a transmit-
  complete interrupt.

  You might wonder why all interrupt handlers cannot run in `normal
  mode' with other interrupts enabled. Ross Biro uses this scenario to
  illustrate the problem:


  o  You get a serial interrupt, and start processing it.  The serial
     interrupt is now masked.

  o  You get a network interrupt, and you start transferring a maximum-
     sized 1500 byte packet from the card.

  o  Another character comes in, but this time the interrupts are
     masked!

  The `fast' interrupt structure solves this problem by allowing
  bounded-time interrupt handlers to run without the risk of leaving
  their interrupt lines masked by another interrupt request.

  There is an additional distinction between fast and slow interrupt
  handlers -- the arguments passed to the handler. A `slow' handler is
  defined as







  ______________________________________________________________________

                  static void
                  handle_interrupt(int reg_ptr)
                  {
                      int irq = -(((struct pt_regs *)reg_ptr)->orig_eax+2);
                      struct device *dev = irq2dev_map[irq];
                  ...
  ______________________________________________________________________



  While a fast handler gets the interrupt number directly


  ______________________________________________________________________

                  static void
                  handle_fast_interrupt(int irq)
                  {
                  ...
  ______________________________________________________________________



  A final aspect of network performance is latency. The only board that
  really addresses this is the 3c509, which allows a predictive
  interrupt to be posted. It provides an interrupt response timer so
  that the driver can fine-tune how early an interrupt is generated.

  Alan Cox has some advice for anyone wanting to write drivers that are
  to be used with pl14 kernels and newer. He says:

  `Any driver intended for pl14 should use the new alloc_skb() and
  kfree_skbmem() functions rather than using kmalloc() to obtain a
  sk_buff. The new pl14 skeleton does this correctly. For drivers
  wishing to remain compatible with both sets the define
  `HAVE_ALLOC_SKB' indicates these functions must be used.

  In essence replace


       skb=(struct sk_buff *)kmalloc(size)


  with


       skb=alloc_skb(size)


  and


       kfree_s(skb,size)


  with


       kfree_skbmem(skb,size)  /* Only sk_buff memory though */


  Any questions should I guess be directed to me (Alan Cox) since I made
  the change.  This is a change to allow tracking of sk_buff's and
  sanity checks on buffers and stack behaviour. If a driver produces the
  message'File: ??? Line: ??? passed a non skb!' then it is probable the
  driver is not using the new sk_buff allocators.'



  6.5.  Programmed I/O vs. Shared Memory vs. DMA


  Ethernet is 10Mbs. (Don't be pedantic, 3Mbs and 100Mbs don't count.)
  If you can already send and receive back-to-back packets, you just
  can't put more bits over the wire. Every modern ethercard can receive
  back-to-back packets. The Linux DP8390 drivers come pretty close to
  sending back-to-back packets (depending on the current interrupt
  latency) and the 3c509 and AT1500 hardware has no problem at all
  automatically sending back-to-back packets.

  The ISA bus can do 5.3MB/sec (42Mb/sec), which sounds like more than
  enough. You can use that bandwidth in several ways:


  6.5.1.  Programmed I/O


  Pro: Doesn't use any constrained system resources, just a few I/O
  registers, and has no 16M limit.

  Con: Usually the slowest transfer rate, the CPU is waiting the whole
  time, and interleaved packet access is usually difficult to
  impossible.


  6.5.2.  Shared memory


  Pro: Simple, faster than programmed I/O, and allows random access to
  packets.

  Con: Uses up memory space (a big one for DOS users, only a minor issue
  under Linux), and it still ties up the CPU.


  6.5.3.  Slave (normal) Direct Memory Access


  Pro: Frees up the CPU during the actual data transfer.

  Con: Checking boundary conditions, allocating contiguous buffers, and
  programming the DMA registers makes it the slowest of all techniques.
  It also uses up a scarce DMA channel, and requires aligned low memory
  buffers.


  6.5.4.  Master Direct Memory Access (bus-master)


  Pro: Frees up the CPU during the data transfer, can string together
  buffers, can require little or no CPU time lost on the ISA bus.

  Con: Requires low-memory buffers and a DMA channel. Any bus-master
  will have problems with other bus-masters that are bus-hogs, such as
  some primitive SCSI adaptors. A few badly-designed motherboard
  chipsets have problems with bus-masters. And a reason for not using
  any type of DMA device is using a Cyrix 486 processor designed for
  plug-in replacement of a 386: these processors must flush their cache
  with each DMA cycle. (This includes the Cx486DLC, Ti486DLC, Cx486SLC,
  Ti486SLC, etc.)
  6.6.  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.'


  6.7.  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



  6.8.  Notes on AMD PCnet / LANCE Based cards


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


  6.9.  Multicast and Promiscuous Mode


  One of the things Donald has been working on recently is the major
  remaining item on the ethercard feature list: implementing multicast
  and promiscuous mode hooks.  All of the released (i.e. not ALPHA) ISA
  drivers now support promiscuous mode. There was a minor problem with
  8390 based cards with capturing multicast packets, in that the
  promiscuous mode setting in 8390.c around line 574 should be 0x18 and
  not 0x10. If you have an up to date kernel, this will already be
  fixed.

  Donald writes: `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 Berkeley
     Packet Filter'' for more info.


  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

  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.'


  6.10.  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.


  7.  Networking with a Laptop/Notebook 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;
  you can get a notebook with a supported 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.


  7.1.  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.


  7.2.  Built in NE2000


  This solution severely limits your laptop choices and is fairly
  expensive. Be sure to read the specifications carefully, as you may
  find that you will have to buy an additional non-standard transceiver
  to actually put the machine on a network. A good idea might be to boot
  the notebook with a kernel that has ne2000 support, and make sure it
  gets detected and works before you lay down your cash.



  7.3.  PCMCIA Support


  As this area of Linux development is fairly young, I'd suggest that
  you join the LAPTOPS mailing channel. See ``Mailing lists...''  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-)

  At present, the two PCMCIA chipsets that are supported are the TCIC/2
  and the intel i82365.

  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)

  For NE2000 compatible cards, some people have had success with just
  configuring the card under DOS, and then booting linux from the DOS
  command prompt via loadlin.

  For those that are net-surfing you can try:

  Don's PCMCIA Stuff (http://cesdis.gsfc.nasa.gov/linux/pcmcia.html)

  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
  even pass this test.

  Things are looking up for Linux users that want PCMCIA support, as
  substantial progress is being made. Pioneering this effort is David
  Hinds.


  7.4.  ISA Ethercard in the Docking Station.


  Docking stations for laptops typically cost about $250 and provide two
  full-size ISA slots, two serial and one parallel port. Most 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.


  7.5.  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, (see ``Xircom'') treat the programming
  information as a trade secret, so support will likely be slow in
  coming. (if ever!)

  Note that the transfer speed will not be all that great (perhaps
  100kB/s tops?) due to the limitations of the parallel port interface.

  See ``DE-600 / DE-620'' and ``RealTek'' for supported pocket adaptors.

  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. (See
  ``keyboard power'')
  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'.  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.


  8.1.  Alpha Drivers -- Getting and Using them


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

  The newest of the `new' drivers can be found on Donald's new ftp site:
  cesdis.gsfc.nasa.gov in the /pub/linux/ area. Things change here quite
  frequently, so just look around for it.  There is still all the stuff
  on the old ftp site ftp.super.org in /pub/linux, but this is not being
  actively maintained, and hence will be of limited value to most
  people.

  As of recent v1.1 kernels, the `useable' alpha drivers have been
  included in the standard kernel source tree. When running make config
  you will be asked if you want to be offered ALPHA test drivers.

  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!

  People reading this while net-surfing may want to check out:

  Don's Linux Home Page
  (http://cesdis.gsfc.nasa.gov/pub/linux/linux.html)

  for the latest dirt on what is new and upcoming.


  8.2.  Using More than one Ethernet Card per Machine


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

  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, and ``Passing
  Ethernet Arguments...''  where there are tips on using LILO to pass
  boot-time ethernet card arguments.

  Also note that only *one* ethercard is auto-probed for, and the second
  *must* be specified as above.  This avoids a lot of possible boot time
  hangs caused by probing sensitive cards. Probing for the second card
  can be achieved by using something as simple as ether=0,0,eth1. In
  this case eth0 and eth1 will be assigned in the order that the cards
  are found at boot. With the previous example, the user has forced the
  card at 0x300 to be eth0 and the card at 0x280 to be eth1.

  Note that if you are intending to use Linux as a gateway between two
  networks, you will have to re-compile a kernel with IP forwarding
  enabled. Usually using an old AT/286 with something like the `kbridge'
  software is a better solution.

  If you are viewing this while net-surfing, you may wish to look at a
  mini-howto Donald has on his WWW site. Check out Multiple Ethercards
  (http://cesdis.gsfc.nasa.gov/linux/misc/multicard.html).


  8.3.  Problems with NE1000 / NE2000 cards (and clones)

  Problem: Errors like 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 in 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.

  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

  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.

  Reason: 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.

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

  Problem: Errors like 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.)

  Problem: NE2000 not detected at boot.

  Donald writes: `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:


  o  Change the bus speed, or just move the card to a different slot.

  o  Change the `I/O recovery time' parameter in the BIOS chipset
     configuration.

  Problem: Network `goes away' every time I print something (NE2000)

  Reason: You have your NE2000 living at 0x360, and a NE2000 is 0x20
  ports wide, putting it to 0x380. Your parallel port is at 0x378 and is
  stepping on the NE2000 cards I/O space.  Jumper it to 0x300 or 0x340
  or something like that.


  8.4.  Problems with WD80*3 cards


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

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

  Solution: Update your ethercard driver: new versions include an
  additional sanity check. If it is the midi chip at 0x388 that is
  getting detected as a WD living at 0x380, then you could also use:

          LILO: linux reserve=0x380,8


  Problem: You get messages such as the following with your 80*3:


       eth0: bogus packet size, status = ........  kmalloc called with impos-
       sibly 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@cesdis.gsfc.nasa.gov - Take particular note of the shared
  memory location.

  Problem: WD80*3 will not get detected at boot.

  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 ``Probed Addresses'' You can also point the mcd driver off
  in another direction by a boot-time parameter (via LILO) such as:

       mcd=0x200,12



  8.5.  Problems with 3Com cards

  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.

  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


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

  Reason: Whoever built your kernel fixed the ethercard IRQ at XX.  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 as described above, or rebuild the kernel, enabling
  autoIRQ by not specifying the IRQ line.

  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


  Also note that kernel revisions 1.00 to 1.03 had an interesting
  `feature'. They would switch to the AUI port when the internal
  transciever failed. This is a problem, as it will *never* switch back
  if for example you momentarily disconnect the cable. Kernel versions
  1.04 and newer only switch if the very first Tx attempt fails.


  8.6.  Problems with Hewlett Packard Cards


  Problem: HP Vectra using built in AMD LANCE chip gets IRQ and DMA
  wrong.

  Solution: The HP Vectra uses a different implementation to the
  standard HP-J2405A. The `lance.c' driver used to always use the value
  in the setup register of an HP Lance implementation.  In the Vectra
  case it's reading an invalid 0xff value. Kernel versions newer than
  about 1.1.50 now handle the Vectra in an appropriate fashion.

  Problem: HP Card is not detected at boot, even though kernel was
  compiled with `HP PCLAN support'.

  Solution: You probably have a HP PCLAN+  -- note the `plus'. Support
  for the PCLAN+ was added to final versions of 1.1, but some of them
  didn't have the entry in `config.in'. If you have the file hp-plus.c
  in  /linux/drivers/net/ but no entry in config.in, then add the
  following line under the `HP PCLAN support' line:


          bool 'HP PCLAN Plus support' CONFIG_HPLAN_PLUS n



  Kernels up tp 1.1.54 are missing the line in `config.in' still.  Do a
  `make mrproper;make config;make dep;make zlilo' and you should be in
  business.

  8.7.  FAQs Not Specific to Any Card.




  8.7.1.  Token Ring

  Is there token ring support for 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. It is the source routing that would be the most time comsuming
  to write.

  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.'

  Peter De Schrijver has been spending some time on Token Ring lately,
  and has patches that are available for IBM ISA and MCA token ring
  cards. Don't expect miracles here, as he has just started on this as
  of 1.1.42. You can get the patch from:

  aix13ps2.cc.kuleuven.ac.be:/pub/Linux/TokenRing.patch-1.1.49.gz



  8.7.2.  32 Bit / VLB / PCI Ethernet Cards


  What is the selection for 32 bit ethernet cards?

  There aren't many 32 bit ethercard device drivers because there aren't
  that many 32 bit ethercards.

  There aren't many 32 bit ethercards out there because a 10Mbs network
  doesn't justify spending the 5x price increment for the 32 bit
  interface.  See ``Programmed I/O vs. ...'' as to why having an
  ethercard on an 8MHz ISA bus is really not a bottleneck.

  This might change now that AMD has introduced the 32 bit PCnet-VLB and
  PCnet-PCI chips.  The street price of the Boca PCnet-VLB board should
  be under $70 from a place like CMO (see Computer Shopper).  See ``Boca
  PCI/VLB'' for info on these cards.

  See ``AMD PCnet-32'' for info on the 32 bit versions of the LANCE /
  PCnet-ISA chip.

  In the future, the DEC 21040 PCI chip will probably be supported as
  well, but don't hold your breath.


  8.7.3.  FDDI

  Is there FDDI support for Linux?

  Donald writes: `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?)'


  8.7.4.  Linking 10BaseT without a Hub


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

  You can link 2 machines easily, but no more than that, without extra
  devices/gizmos. See ``Twisted Pair'' -- 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.


  8.7.5.  SIOCSFFLAGS: Try again


  I get `SIOCSFFLAGS: Try again' when I run `ifconfig' -- Huh?

  Some other device has taken the IRQ that your ethercard is trying to
  use, and so the ethercard can't use the IRQ.  You don't necessairly
  need to reboot to resolve this, as some devices only grab the IRQs
  when they need them and then release them when they are done. Examples
  are some sound cards, serial ports, floppy disk driver, etc. You can
  type cat /proc/interrupts to see which interrupts are presently in
  use. Those marked with a `+' are ones that are not taken on a
  permanent basis. Most of the Linux ethercard drivers only grab the IRQ
  when they are opened for use via `ifconfig'. If you can get the other
  device to `let go' of the required IRQ line, then you should be able
  to `Try again' with ifconfig.


  8.7.6.  Link UNSPEC and HW-addr of 00-00-00-00-00-00


  When I run ifconfig with no arguments, it reports that LINK is UNSPEC
  (instead of 10Mbs Ethernet) and it also says that my hardware address
  is all zeros.

  This is because people are running a newer version of the `ifconfig'
  program than their kernel version. This new version of ifconfig is not
  able to report these properties when used in conjunction with an older
  kernel. You can either upgrade your kernel, `downgrade' ifconfig, or
  simply ignore it. The kernel knows your hardware address, so it really
  doesn't matter if ifconfig can't read it.


  8.7.7.  Huge Number of RX and TX Errors


  When I run ifconfig with no arguments, it reports that I have a huge
  error count in both rec'd and transmitted packets. It all seems to
  work ok -- What is wrong?

  Look again. It says RX packets big number PAUSE errors 0 PAUSE dropped
  0 PAUSE overrun 0.  And the same for the TX column.  Hence the big
  numbers you are seeing are the total number of packets that your
  machine has rec'd and transmitted.  If you still find it confusing,
  try typing cat /proc/net/dev instead.


  8.7.8.  Entries in /dev/ for Ethercards


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

  Contrary to what you have heard, the files in /dev/* are not used.
  You can delete any /dev/wd0, /dev/ne0 and similar entries.
  8.7.9.  Linux and ``trailers''


  Should I disable trailers when I `ifconfig' my ethercard?

  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 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.


  9.1.  Passing Ethernet Arguments to the Kernel via LILO


  Here are two generic kernel commands that would be typed after the
  name of your configuration in your lilo.conf file (usually `linux')
  For exmaple, if the command was `blah' and it expected 3 arguments
  (say 123, 456, and 789) then you would use:

  LILO: linux blah=123,456,789


  9.1.1.  The ether command


  In its most generic form, it looks something like this:


       ether=IRQ,BASE_ADDR,PARAM_1,PARAM_2,NAME


  All arguments are optional.  The first non-numeric argument is taken
  as the NAME.

  IRQ: Obvious.  An IRQ value of `0' (usually the default) means to
  autoIRQ.  It's a historical accident that the IRQ setting is first
  rather than the base_addr -- this will be fixed whenever something
  else changes.

  BASE_ADDR: Also obvious.  A value of `0' (usually the default) means
  to probe a card-type-specific address list for an ethercard.

  PARAM_1: It was orginally used as an override value for the memory
  start for a shared-memory ethercard, like the WD80*3.  Some drivers
  use the low four bits of this value to set the debug message level.  0
  -- default, 1-7 -- level 1..7, (7 is maximum verbosity)  8 -- level 0
  (no messages).

  PARAM_2: The 3c503 driver uses this select between the internal and
  external transceivers.  0 -- default/internal, 1 -- AUI external.

  NAME: Selects the network device the values refer to.  The standard
  kernel uses the names `eth0', `eth1', `eth2' and `eth3' for bus-
  attached ethercards, and `atp0/dl0' for parallel port `pocket'
  ethernet adaptors.  The default setting is for a single ethercard to
  be probed for as `eth0'.  Multiple cards can only be enabled by
  explicitly setting up their base address using these LILO parameters.
  The 1.0 kernel has LANCE-based ethercards as a special case.  LILO
  arguments are ignored, and LANCE cards are always assigned `eth<n>'
  names starting at `eth0'.  Additional non-LANCE ethercards must be
  explicitly assigned to `eth<n+1>', and the usual `eth0' probe disabled
  with something like  `ether=0,-1,eth0'.  ( Yes, this is bug. )


  9.1.2.  The reserve command


  This next lilo command is used just like `ether=' above, ie. it is
  appended to the name of the boot select specified in lilo.conf


       reserve=IO-base,extent{,IO-base,extent...}


  In some machines it may be necessary to prevent device drivers from
  checking for devices (auto-probing) in a specific region. This may be
  because of poorly designed hardware that causes the boot to freeze
  (such as some ethercards), hardware that is mistakenly identified,
  hardware whose state is changed by an earlier probe, or merely
  hardware you don't want the kernel to initialize.

  The reserve boot-time argument addresses this problem by specifying an
  I/O port region that shouldn't be probed. That region is reserved in
  the kernel's port registration table as if a device has already been
  found in that region. Note that this mechanism shouldn't be necessary
  on most machine, only when there is a problem or special case.

  The I/O ports in the specified region are protected against device
  probes. This was put in to be used when some driver was hanging on
  e.g. a NE2000, or misidentifying some other device as its own.  A
  correct device driver shouldn't probe a reserved region, unless
  another boot argument explicitly specifies that it do so.  This
  implies that reserve will most often be used with some other boot
  argument. Hence if you specify a reserve region to protect a specific
  device, you must generally specify an explicit probe for that device.
  Most drivers ignore the port registration table if they are given an
  explicit address.

  For example, the boot line


       LILO: linux  reserve=0x300,32  ether=0,0x300,eth0


  keeps all device drivers except the ethercard drivers from probing
  0x300-0x31f.

  As usual with boot-time specifiers there is an 11 parameter limit,
  thus you can only specify 5 reserved regions per reserve keyword.
  Multiple reserve specifiers will work if you have an usually
  complicated request.


  9.2.  Contributors


  Other people who have contributed (directly or indirectly) to the
  Ethernet-Howto are, in alphabetical order:

          Peter Bauer             <pbauer@rnivh.rni.sub.org>
          Ross Biro               <bir7@leland.Stanford.EDU>
          Alan Cox                <iiitac@pyr.swan.ac.uk>
          David C. Davies         <davies@wanton.enet.dec.com>
          Bjorn Ekwall            <bj0rn@blox.se>
          David Hinds             <dhinds@allegro.stanford.edu>
          Michael Hipp            <mhipp@student.uni-tuebingen.de>
          Mike Jagdis             <jaggy@purplet.demon.co.uk>
          Duke Kamstra            <kamstra@ccmail.west.smc.com>
          Russell Nelson          <nelson@crynwr.com>
          Cameron Spitzer         <camerons@NAD.3Com.com>
          Dave Roberts            <david.roberts@amd.com>
          Glenn Talbott           <gt@hprnd.rose.hp.com>




  Many thanks to the above people, and all the other unmentioned testers
  out there.


  9.3.  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.

  Thanks,

  Paul Gortmaker, Paul.Gortmaker@anu.edu.au

  Donald J. Becker, becker@cesdis.gsfc.nasa.gov