Chip 1996 November/Chip 11-96.iso/workshop/howto/ethernet

Text File | 1996-05-25 | 106.7 KB | 2,582 lines

Linux Ethernet HOWTO v1.03 -- Last updated June 22, 1994
=================================================================

NOTE 1:    This will (hopefully) be the last maintained ASCII version.
    The Ethernet-HOWTO will from then on be maintained in the
    SGML format, which can then generate ASCII, LaTeX, HTML (www)
    and other formats. Look for it in about a month from the above
    date.

NOTE 2:    Donald has a new e-mail address, and accordingly, a new ftp
    site. The e-mail addr is below, and the ftp site is in the
    FAQ section, under "I heard there is an alpha driver for my
    card - where do I get it?"

-------------------------------------------------------------

-- covers changes up to and including Linux kernel v1.1

INDEX:

0    Introduction.
0.01        How do I use this Guide?
0.01        Disclaimer and Copyright
0.02        Questions already?
0.03        Related Documentation
0.04        New Versions of this Document
0.05        Feedback

1    What card should I buy for Linux?
1.01        Eight bit vs 16 bit
1.02        Low price Ethernet cards
1.03        Vendors and brands to avoid.
1.04        Type of cable that your card should support

2    Status of various Ethernet cards under Linux.
2.01        3Com
2.02        Western Digital / SMC
2.03        NExxxx
2.04        Hewlett Packard Cards
2.05        D-Link
2.06        Cabletron
2.07        Allied Telesis
2.08        Arcnet
2.09        Digital / DEC
2.10        Intel
2.11        PureData
2.12        Xircom
2.13        Zenith
2.14        Racal-Interlan
2.15        AMD LANCE (79C960)
2.16        AT-Lan-Tec / RealTek Pocket adaptor
2.17        Ansel
2.18        DFI
2.19        IBM

3    Clones of popular Ethernet cards.
3.01        WD80x3 Clones
3.02        NE2000 Clones

4    Cables, coax, twisted pairs etc.
4.01        Thin Ethernet (thinnet)
4.02        Twisted Pair
4.03        Thick Ethernet

5    Technical information.
5.01        Probed addresses
5.02        Skeleton / prototype driver
5.03        Driver interface to the kernel
5.04        Interrupts and linux
5.05        Programmed I/O vs. shared mem. vs slave/master DMA
5.06        Programming the Intel chips (i82586 and i82593)
5.07        Programming information from 3Com
5.08        Notes on AMD PCnet-ISA / LANCE Based cards (79C960)
5.09        Multicast and Promiscuous mode
5.10        The Berkeley Packet Filter (BPF)
5.11        Unresolved questions / concerns

6    Possible problems, questions and troubleshooting.
6.01        Problems with NE2000 (and clones)
6.02        Problems with WD80*3 cards
6.03        Problems with 3Com cards
6.04        Problems with Hewlett Packard Cards

7    Networking with a laptop computer.
7.01        Option 1 -- using SLIP
7.02        Option 2 -- Built in NE2000 compatible or PCMCIA Ethercard.
7.03        Option 3 -- ISA Ethercard in the docking station.
7.04        Option 4 -- Pocket / parallel port adaptors.

8    Frequently asked questions.
8.01        Just the FAQ's ma'am -- just the FAQ's.

9    Miscellaneous.
9.01        Passing Ethernet Arguments to the Kernel via LILO
9.02        Bad Vendors
9.03        Closing

======================================================================

0. Introduction.

    This is the Ethernet-HOWTO, which is a compilation of information
    about which ethernet devices can be used for Linux, and how to
    set them up.

    This Ethernet-HOWTO is by:
        Donald J. Becker    <[e-mail]>
        Paul Gortmaker        <[e-mail]>

    It covers what cards you should and shouldn't buy; how to set
    them up, how to run more than one, and other common problems and
    questions. It does *not* cover the software end of things, as that
    is covered in the NET-2 HOWTO.

    Other people who have contributed (directly or indirectly) are,
    in alphabetical order:

    Peter Bauer        <[e-mail]>
    Ross Biro        <[e-mail]>
    Alan Cox        <[e-mail]>
    David C. Davies        <[e-mail]>
    Bjorn Ekwall        <[e-mail]>
    Charles Hedrick        <[e-mail]>
    Mike Jagdis        <[e-mail]>
    Duke Kamstra        <[e-mail]>
    Russell Nelson        <[e-mail]>
    Cameron Spitzer        <[e-mail]>
    Dave Roberts        <[e-mail]>
    Glenn Talbott        <[e-mail]>
    Miquel van Smoorenburg    <[e-mail]>

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

0.01 How Do I Use This Guide?

    As this guide is getting bigger and bigger, you probably don't want
    to spend the rest of your afternoon reading the whole thing. And you
    don't *have* to read it all. If you haven't got an ethernet card, then
    you will want to start with section one to see what you should buy,
    and what you should avoid. If you have already got an ethernet card,
    but are not sure if you can use it with Linux, then you will want to
    read section two, which contains specific information on each
    manufacturer, and their cards. If you are having trouble with your
    card, then you will want to read the specific information about
    your card in section two and the troubleshooting information in
    section six. If you are interested in some of the technical aspects
    of the device drivers, then you can find that information in
    section 5.

0.01 Disclaimer and Copyright

    This document is *not* gospel. However, it is probably the most
    up to date info that you will be able to find. Nobody is responsible
    for what happens to your hardware but yourself. If your ethercard
    or any other hardware goes up in smoke (...nearly impossible!)
    we take no responsibility. ie. THE AUTHORS ARE NOT RESPONSIBLE
    FOR ANY DAMAGES INCURRED DUE TO ACTIONS TAKEN BASED ON THE
    INFORMATION INCLUDED IN THIS DOCUMENT.

    This document is Copyright (c) 1994 by Donald Becker and
    Paul Gortmaker. Permission is granted to make and distribute
    verbatim copies of this manual provided the copyright notice
    and this permission notice are preserved on all copies.

    Permission is granted to copy and distribute modified versions
    of this document under the conditions for verbatim copying,
    provided that this copyright notice is included exactly as in
    the original, and that the entire resulting derived work is
    distributed under the terms of a permission notice identical
    to this one.

    Permission is granted to copy and distribute translations
    of this document into another language, under the above
    conditions for modified versions.

0.02 Questions already?

    If you have questions about your ethernet card, please READ this
    document first. You may also want to join the NET channel of the
    Linux-activists mailing list by sending mail to
        [e-mail]
    with the line
        X-Mn-Admin: join NET
    at the top of the message body (not the subject). If you want to
    learn how to use the mailing channels, then send an empty message
    to the above address, and you will get an instruction manual sent
    back to you in a few hours. However, it is worth noting that the NET
    channel is primarily used for discussion of the networking code, and
    you may not see much discussion about a particular driver.
    Furthermore keep in mind that the NET channel is for development
    discussions only. General questions on how to configure your system
    should be directed to comp.os.linux.help unless you are actively
    involved in the development of part of the networking for Linux.
    We ask that you *please* respect this general guideline for content.
    You can safely bet that neither of the authors will respond to
    any plea for help that *should* be posted to c.o.l.help, but is
    inappropriately placed elsewhere.

0.03 Related Documentation

    Much of this info came from saved postings from the comp.os.linux
    groups, which shows that it is a valuable resource of information.
    Other useful information came from a bunch of small files by Donald
    himself. Of course, if you are setting up an Ethernet card,
    then you will want to read the NET-2 HOWTO so that you can actually
    configure the software you will use.  And last but not least, the
    contributions from the individuals and companies listed above are
    greatly appreciated as well. Oh yeah, if you fancy yourself as
    a bit of a hacker, you can always scrounge some additional info
    from the driver source files as well. There is usually a paragraph
    in there describing any important points.

0.04 New versions of this document

    New versions of this document can be retrieved via anonymous
    FTP from sunsite.unc.edu:/pub/Linux/docs/HOWTO/* and various
    Linux ftp mirror sites. It will also be posted to the newsgroup
    comp.os.linux.announce at a regular interval. Updates will be made
    as new information / drivers becomes available. If this copy
    that you are reading is more than 2 months old, it is either out of
    date, or it means that I have been lazy and haven't updated it.
    Look for other formats in the future, as this will be the last
    maintained ASCII version. After that, the ASCII versions will be
    automatically generated from SGML source.

0.05 Feedback

    Any corrections can be sent to one of us ([e-mail]
    or [e-mail]) We will *attempt* to keep this
    up to date as more drivers become available, and as the networking
    code matures.

1 What card should I buy for Linux?

    For impatient users that just want a quick, cheap answer the
    summary is: get 16 bit thinnet 8013 cards. For more detail as
    to the who what where and why, read on.

1.01 Eight bit vs 16 bit

    Unless you are a light user, or are confined to using the smaller
    ISA slot, the use of the 8 bit cards like the wd8003 and the 3c503
    is really not worth the cost savings. Get the 8013 or the 3c503/16
    instead.

1.02 Low price Ethernet cards

    The lowest price seen so far was in the March '94 edition of LAN
    magazine. There was an ad for Addtron AE-200 cards (jumper settable
    NE2000 clones) for a measly $19 ea! (limit 2). Unfortunately this
    offer has since expired. However, you might want to check to see
    what their everyday price is.

    You can also call AT-LAN-TEC at 301-948-7070. Ask for their
    technical support person, "Vincent Bono". As with all purchases,
    you should indicate you are buying this for a Linux system.
    The last I checked the price for 10 NE2000s was $480, or $48 ea.!
    NB: Their current NE2000 clone is a model that "traps" other
    drivers that probe into their address space. AT-LAN-TEC also carries
    a clone, non-EEPROM 8013 board for somewhat more, and a NE2100 clone.
    Either is a better choice if the very lowest price isn't essential.

    Also, SMC has been offering an evaluation deal on their new Ultra
    cards, and the word is that you can get one for $50. You can ask
    them yourself by calling 1-800-SMC-4YOU in Canada and the USA.

    The Allied Telesis AT1500 is offered at a good price by many vendors.
    Even Inmac, known for their premium markup, has this card for under
    $100.

1.03 Vendors and Brands to Avoid

    These vendors have decided *not* to release programming information
    about their products, without signing a non-disclosure agreement.
    More information can be found in section two and 9.01. Hence it is
    strongly advised that you avoid buying products offered from
    these companies.

        (1) Cabletron
        (2) Xircom

    These particular cards should be avoided, as they are obsolete.
    The reasons as to why they have been classified as such can be
    found in section 2 of this document.

        (1) 3c501
        (2) Arcnet

1.04 Type of cable that your card should support

    Unless you have to conform to an existing network, you will want
    to use thinnet or thin ethernet cable. This is the style with the
    standard BNC connectors. See section 4 for other concerns with
    different types of ethernet cable.

    Most ethercards also come in a "Combo" version for only $10-$20 more.
    These have both twisted pair and thinnet transceiver built-in,
    allowing you to change your mind later.

2 Status of Various Ethernet Cards under Linux

    The only thing that one needs to use an ethernet card with Linux
    is the appropriate driver. For this, it is essential that the
    manufacturer will release the technical programming information to
    the general public without you (or anyone) having to sign your life
    away. A good guide for the likelihood of getting documentation
    (or, if you aren't writing code, the likelihood that someone
    else will write that driver you really, really need) is the
    availability of the Crynwr (nee Clarkson) packet driver. Russ
    Nelson (see the acknowledgements in the intro.) runs this
    operation, and has been very helpful in supporting the development
    of drivers for Linux.

    Given the documentation, you can write a driver for
    your card and use it for Linux, at least in theory. Keep in
    mind that some old hardware that was designed for XT type
    machines will not function very well in a multitasking
    environment such as Linux. Use of these will lead to major
    problems if your network sees a reasonable amount of traffic.

    Most cards come with drivers for MS-DOS interfaces such as
    NDIS and ODI, but these are useless for Linux. Many people
    have suggested directly linking them in or automatic
    translation, but this is nearly impossible. The MS-DOS
    drivers expect to be in 16 bit mode and hook into "software
    interrupts", both incompatible with the Linux kernel. This
    incompatibility is actually a feature, as some Linux drivers
    are considerably better than their MS-DOS counterparts. The
    "8390" series drivers, for instance, use ping-pong transmit
    buffers, which are only now being introduced in the MS-DOS world.

    Keep in mind that PC ethercards have the widest variety of
    interfaces (shared memory, programmed I/O, bus-master, or slave
    DMA) of any computer hardware for anything, and supporting a
    new ethercard sometimes requires re-thinking most of the lower-level
    networking code. (If you are interested in learning more about
    these different forms of interfaces, see section 5)

    Also, similar product numbers don't always indicate similar products.
    For instance, the 3c50* product line from 3Com varies wildly
    between different members.

    Enough talk. Let's get down to the information you want.

2.01 3Com

    If you are not sure what your card is, but you think it is a
    3Com card, you can probably figure it out from the assembly
    number. 3Com has a document "Identifying 3Com Adapters By
    Assembly Number" (ref 24500002) that would most likely clear
    things up. See section 5.07 for info on how to get documents
    from 3Com.

    Supported:

        3c503, 3c503/16
            3Com shared-memory ethercards. They also have a
            programmed I/O mode that doesn't use the 8390
            facilities (their engineers found too many bugs!)
            It should be about the same speed as the same bus
            width WD80x3, but I don't have a 16 bit version
            to benchmark. Unless you are a light user, spend
            the extra money and get the 16 bit model, as the
            price difference isn't significant. The 3c503 does not
            have "EEPROM setup", so the diagnostic/setup program
            isn't needed before running the card with Linux. The
            shared memory address of the 3c503 is set using jumpers
            that are shared with the boot PROM address. This is
            confusing to people familiar with other ISA cards,
            where you always leave the jumper set to "disable"
            unless you have a boot PROM.

            The Linux 3c503 driver can also work with the 3c503
            programmed-I/O mode, but this is slower and less
            reliable than shared memory mode. Also, programmed-I/O
            mode is not tested when updating the drivers, the
            deadman (deadcard?) check code may falsely timeout on
            some machines, and the probe for a 3c503 in
            programmed-I/O mode is turned off by default in some
            versions of the kernel. This was a panic reaction to
            the general device driver probe explosion; the 3c503
            shared memory probe is a safe read from memory, rather
            than an extensive scan through I/O space. As of pl13,
            the kernel has an I/O port registrar that makes I/O
            space probes safer, (see section 5.1 for more info.)
            and the programmed-I/O 3c503 probe has been re-enabled.
            You still shouldn't use the programmed-I/O mode though,
            unless you need it for MS-DOS compatibility.

            The 3c503's IRQ line is set in software, with no hints
            from an EEPROM. Unlike the MS-DOS drivers, the
            Linux driver has capability to autoIRQ: it uses the
            first available IRQ line in {5,2/9,3,4}, selected each
            time the card is 'ifconfig'ed. (Older driver versions
            selected the IRQ at boot time.) The ioctl() call
            in 'ifconfig' will return EAGAIN if no IRQ line is
            available at that time.

            Some common problems that people have with the 503
            are discussed in section 6.03.

        3c509
            A fairly new card from 3Com. It's inexpensive and has
            excellent performance for a non-bus-master design. The
            drawbacks are that it _requires_ very low interrupt
            latency, and it isn't rated for bus speeds greater than
            8Mhz.

            A working 3c509 driver was first included as an
            alpha-test version in the 0.99pl13 kernel sources.
            It is now in the standard kernel.

            The 3c509 has a tiny Rx buffer, causing the driver to
            occasionally drop a packet if interrupts are masked for
            too long. To minimize this problem, the driver should
            be completely rewritten to use predictive interrupts.
            (Note: performance re-writes of working drivers are low
            priority unless there is some particular incentive or
            need.)

            There is also an alpha version of a Linux 3c509
            diagnostic and EEPROM setup program, but for now
            users that don't like the defaults should use the
            MS-DOS EEPROM setup program.

        3c579
            The EISA version of the 509. The current EISA version
            uses the same 16 bit wide chip rather than a 32 bit
            interface, so the performance increase isn't stunning.
            The EISA probe code was added to 3c509.c for pl14.
            We would be interested in hearing progress reports
            from any 3c579 users. (Read the above 3c509
            section for info on the driver.)

            Cameron Spitzer writes:
            "The 3C579 (Etherlink III EISA) should be configured
            as an EISA card. The IO Base Address (window 0
            register 6 bits 4:0) should be 1f, which selects EISA
            addressing mode. Logic outside the ASIC decodes the
            IO address s000, where s is the slot number. I don't
            think it was documented real well. Except for its IO
            Base Address, the '579 should behave EXACTLY like the
            '509 (EL3 ISA), and if it doesn't, I want to hear
            about it (at my work address).

            I will leave it to the Real Programmers to suggest
            the right hack to /usr/src/linux/net/inet/3c509.c to
            take care of the EISA case.

            (Note that the drivers now reside in ./drivers/net/
             and *not* ./inet/net/ --- pg.)

            Beware that if you put a '509 in EISA addressing mode
            by mistake and save that in the EEPROM, you'll have
            to use an EISA machine or the infamous Test Via to
            get it back to normal, and it will conflict at IO
            location 0 which may hang your ISA machine. It's not
            my job to say whether this is a bug or feature, but I
            have heard loud and clear that customers don't like
            it and I don't think we'll do it that way again."

        3c589

            Look for support for this PCMCIA card in the near
            future. It already works, even with "hot-swapping"
            but the problem of separating the PCMCIA controller
            chipset code from the actual driver code is still
            being worked on. See the section on PCMCIA support
            (7.02) for more info. Brave PCMCIA hackers can
            check out the alpha driver found in the usual place.

    Unsupported:

        3c501
            Too brain-damaged to use. Available surplus from many
            places. Avoid it like the plague. Again, do not
            purchase this card, even as a joke. It's performance
            is horrible, and it breaks in many ways.

            (I have a standing offer: I'll pay $2 for each 3c501
            shipped to me postpaid, but only if you include the
            BNC 'T' connector and the jumpers. $2.50 if you just
            send the 'T', jumpers, and address PROM and promise to
            destroy the board. -djb)

            Cameron L. Spitzer of 3Com said:
            "I'm speaking only for myself here, of course, but I
            believe 3Com advises against installing a 3C501 in a
            new system, mostly for the same reasons Donald has
            discussed. You probably won't be happy with the
            3C501 in your Linux box. The data sheet is marked
            "(obsolete)" on 3Com's Developers' Order Form, and
            the board is not part of 3Com's program for sending
            free Technical Reference Manuals to people who need
            them. The decade-old things are nearly
            indestructible, but that's about all they've got
            going for them any more."

            For those not yet convinced, the 3c501 can only do one
            thing at a time -- while you are removing one packet
            from the single-packet buffer it cannot receive
            another packet, nor can it receive a packet while are
            loading a transmit packet. This was fine for a
            network between two 8088-based computers where
            processing each packet and replying took 10's of
            msecs, but modern networks send back-to-back
            packets for almost every transaction.

            Having read this far, you must be persistent, so you
            get let in on a secret. As of pl13, some more of
            the hardware problems were "compensated for".

            Ie. in a fit of madness I wasted a whole day updating
            my 3c501 driver and then trying to track down a few
            more of the 3c501 glitches. It now works well enough
            to NFS mount filesystems, but the receiver still
            occasionally hangs. I'm mostly certain that this is
            a hardware bug. When it hangs, the next set of
            outgoing packets will reset the board, but that's
            only useful if you have something occasionally
            generating outgoing packets.

            The driver is now in the std. kernel, but under the
            following conditions: This is unsupported code. I
            know my usual copyright says all the code is
            unsupported, but this is _really_ unsupported. I
            DON'T want to see bug reports, and I'll accept bug
            fixes only if I'm in a good mood that day.

            I don't want to see a fest of "Linux ethercards for
            sale" postings. A bunch of people have bought dozens
            of "dumpster special" 3c501s, and they hope to sell
            them at rip-off prices. A 3c501 is barely worth the
            shipping cost, and if I see people trying to sell
            them here by claiming "supported by Linux" I _will_
            flame them. They are _not_ supported by Linux.

            I don't want to be flamed later for putting out bad
            software. I don't know all all of the 3c501 bugs,
            and I know this driver only handles a few that I've
            been able to figure out. It has taken a long
            intense effort just to get the driver working this
            well.

            That said, you will find it included in "config.in"
            No special mods are needed to use it with pl15
            or greater kernels. Jumper your card to 0x280.

            AutoIRQ works, DMA isn't used, the autoprobe only
            looks at 0x280, the debug level is set with the third
            boot-time argument. You'll probably want to change
            the default EL_DEBUG to '2'.

            Once again, THE USE OF A 3c501 IS STRONGLY DISCOURAGED
            and it is NOT SUPPORTED BY LINUX.


        3c505
            An Intel-based ethercard with no driver available
            at present. (Not a very common card.)

        3c507
            This card uses one of the Intel chips, and the
            development of the driver is closely related to
            the development of the Intel Ether Express driver.
            The driver has been included in the standard
            release of pl15. You will have to un-comment
            the 3c507 line in "config.in" -- in case you
            didn't figure it out already, it is commented
            out because it is still being tested.

            Technical information is available in section 5.06,
            and if you have experience in writing drivers, see
            section 5.07 as well.

2.02 Western Digital / SMC

    The ethernet part of Western Digital has been bought by SMC. The
    SMC Elite and SMC Elite Plus are the same as late-model WD8003
    and WD8013 cards. Note that the SMC Elite Ultra is *not* the
    same as the plain SMC Elite / WD8013 card. (see below)

    Supported:

        WD8003, WD8013, SMC Elite, SMC Elite Plus
            A shared memory design by Western Digital. The
            8 bit 8003 is slightly less expensive, but only
            worth the savings for light use. Over the
            years the design has added more registers and an
            EEPROM. Clones usually go by the '8013' name, and
            usually use a non-EEPROM (jumpered) design. This part
            of WD has been sold to SMC, so you'll usually see
            something like SMC/WD8013 or SMC Elite Plus (WD8013).
            The shared memory makes the cards 10-20% faster,
            especially with larger packets. More importantly
            (to me at least) it avoids a few bugs in the
            programmed-I/O mode of the 8390, allows safe
            multi-threaded access to the packet buffer, and
            doesn't have a programmed-I/O data register that
            hangs your machine during warm-boot probes.

        SMC Elite 16 ULTRA
            This ethercard is based on a new chip from SMC, with
            a few new features. While it has a mode that is
            similar to the older SMC ethercards, it's not
            compatible with the old WD80*3 drivers. However, in
            this mode it shares most of its code with the other
            8390 drivers, while operating somewhat faster than a
            WD8013 clone.

            Some of the device probe checks in pl14 were too
            too strict, causing some cards to not be detected
            every time. This was fixed for pl14a, and hence is
            fine for pl15. Since part of the Ultra "looks" like
            an 8013, the Ultra probe is supposed to find an
            Ultra before the wd8013 probe has a chance to
            mistakenly identify it.

            Std. as of pl14, and made possible by documentation
            and ethercard loan from [e-mail],
            Duke Kamstra. If you plan on using an Ultra with Linux
            send him a note of thanks to let him know that there
            are Linux users out there!

            I'm considering writing a separate driver for the
            Ultra's "Altego" mode which allows chaining transmits
            at the cost of inefficient use of receive buffers,
            but that will probably not happen right away.
            Performance re-writes of working drivers are low
            priority unless there is some particular incentive
            or need.

2.03 NExxxx

    The prefix "NE" came from Novell Ethernet. Novell followed the
    cheapest NatSemi databook design and sold the manufacturing rights
    (spun off?) Eagle, just to get reasonably-priced ethercards into
    the market.

    Supported:

        NE1000, NE2000
            The now-generic name for a bare-bones design around
            the NatSemi 8390. They use programmed I/O rather than
            shared memory, leading to easier installation but
            slightly lower performance and a few problems. Again,
            the savings of using an 8 bit NE1000 over the NE2000
            are only warranted if you expect light use. Some
            recently introduced NE2000 clones use the National
            Semiconductor "AT/LANTic" 83905 chip, which offers
            a shared memory mode similar to the 8013 and EEPROM
            or software configuration. Some problems can arise
            with poor clones. See the question and answer section
            later in this document, and the section on clones.
            I have written a NE2000 diagnostic program, but it
            is still presently in alpha test. (ne2k)

        NE1500, NE2100
            The AT1500 driver, recently added to the list of
            supported cards, also supports the NE1500, NE2100 and
            clones. The driver shipped with pl12 kernel doesn't
            detect non-AT1500 cards with autoprobe, but will work
            fine if you specify the base address explicitly and
            jumper for DMA channel 5. Read the Allied Telesis
            section for more information on LANCE based cards.

2.04 Hewlett Packard

    The 272** cards use programmed I/O, similar to the NE*000 boards,
    but the data transfer port can be "turned off" when you aren't
    accessing it, avoiding problems with autoprobing drivers.

    Thanks to Glenn Talbott for cleaning up the confusion in this
    section regarding the version numbers of the HP hardware, and
    adding lots of new info.

    Supported:

        27245A
            8 Bit 8390 based 10BaseT, not recommended for all the
            8 bit reasons. It was re-designed a couple years
            ago to be highly integrated which caused some
            changes in initialization timing which only
            affected testing programs, not LAN drivers. (The
            new card is not 'ready' as soon after switching
            into and out of loopback mode.)

        27247B, 27252A
            The 47B is a 16 Bit 8390 based 10BaseT w/AUI, and
            the 52A is a 16 Bit 8390 based ThinLAN w/AUI.
            These cards are high performers (3c509 speed) without
            the interrupt latency problems (32K onboard RAM for TX
            or RX packet buffering). They both offer LAN
            connector autosense, data I/O in I/O space (simpler) or
            memory mapped (faster), and soft configuration. 27247B
            was rated Best for ISA Servers by PC Mag this year.

        27247A
            This is the older model that existed before the "B".
            Two versions 27247-60001 or 27247-60002 have part
            numbers marked on the card. Functionally the same to
            the LAN driver, except bits in ROM to identify
            boards differ. -60002 has a jumper to allow
            operation in non-standard ISA busses (chipsets
            that expect IOCHRDY early.)

        HP J2405A
            These are lower priced, and slightly faster than the
            27247B/27252A, but are missing some features, such
            as AUI, ThinLAN connectivity, and boot PROM socket.
            This is a fairly generic LANCE design, but a minor
            design decision makes it incompatible with a generic
            "NE2100" driver. Special support for it (including
            reading the DMA channel from the board) is in pl14
            and up, thanks to information provided by HP's Glenn
            Talbott, [e-mail]. Note that the pre pl14
            driver should not be used with this card.

            More information on LANCE based cards can be found in
            section 5.08.

2.05 D-Link

    Supported:

        DE-600
            Laptop users and other folk who might want a quick
            way to put their computer onto the ethernet may want
            to use this. The driver was included with the default
            kernel source tree as of pl12 and possibly earlier.
            Bjorn Ekwall <[e-mail]> wrote the original.
            Expect about 80kb/s transfer speed from this via the
            parallel port. You should read the README.DLINK
            file in the kernel source tree. The latest release
            of this driver is v0.32, and it is included in the
            standard kernel of pl15

        DE-620
            Same as the DE-600, only with two output formats.
            (BNC and RJ-45, I would assume... ????)
            Bjorn has just finished a driver for this model,
            for kernel versions 1.1.X -- but it can be patched
            into 1.0.X kernels if you _really_ wanted to.

        DE-650
            Some people have been using this PCMCIA card for
            some time now with their notebooks. Note however,
            that using a PCMCIA card with Linux is not trivial.
            See the section on networking with a notebook for
            more information on PCMCIA cards. This driver is
            *not* part of the standard kernel.

        DE-100, DE-200, DE-220-T
            The manual says that it is 100% compatible with the
            NE2000. This is not true. You should call them and
            tell them you are using their card with Linux, and they
            should correct their documentation. Some pre-0.99pl12
            driver versions may have trouble recognizing the DE2**
            series as 16 bit cards, and these cards are the most
            widely reported as having the spurious transfer address
            mismatch errors. Note that there are cards from
            Digital (DEC) that are also named DE100 and DE200,
            but the similarity stops there.

2.06 Cabletron

    Yes, another one of these companies that won't release its
    programming information. They waited for months before actually
    confirming that all their information was proprietary, deliberately
    wasting my time. Avoid their cards like the plague if you can.
    Also note that some people have phoned Cabletron, and have been
    told things like "a D. Becker is working on a driver
    for linux" -- making it sound like I work for them. This is
    NOT the case. Anyway, if I were working for them, or even if
    I had signed a ND agreement, I wouldn't be able to tell
    everyone what a sleazy design the E2100 is. (See below.)

    If you feel like asking them why they don't want to release their
    info so that people can use their cards, write to [e-mail]
    Tell them that you are using Linux, and are disappointed that they
    don't support open systems. (See section 9.01)

    Supported: (...well, not *really* supported)

        E10**, E10**-x, E20**, E20**-x
            These are NEx000 almost-clones that are reported to
            work with the standard NEx000 drivers, thanks to a
            ctron-specific check during the probe. If there are
            any problems, they are unlikely to be fixed, as the
            programming information is unavailable.


        E21**
            Again, there is not much one can do when the
            programming information is proprietary.
            The E2100 is a poor design. Whenever it maps its
            shared memory in during a packet transfer, it
            maps it into the *whole 128K region*! That means you
            *can't* safely use another interrupt-driven shared
            memory device in that region, including another E2100.
            It will work _most_ of the time, but every once in
            a while it will bite you. (Yes, this problem can
            be avoided by turning off interrupts while
            transferring packets, but that will almost certainly
            lose clock ticks.

            Also, don't confuse the E2100 for a NE2100 clone.
            The E2100 is a shared memory NatSemi DP8390 design,
            roughly similar to a brain-damaged WD8013, whereas
            the NE2100 (and NE1500) use a bus-mastering AMD
            LANCE design.

            There is an alpha test driver available (even though
            I shouldn't have bothered) in the normal place
            (see the FAQ section) -- e2100.c -- let me know if
            you use it, and how it works. Don't forget to
            un-comment the line in config.in.

2.07    Allied Telesis

    Allied Telesis is the worlds largest maker of separate
    transceivers thanks to their low prices, and they now have a
    series of low-cost ethercards using the 79C960 version of the AMD
    LANCE. These are bus-master cards, and thus probably the fastest
    ISA bus ethercards available (although the 3c509 has lower latency
    thanks to predictive interrupts).

    Supported:

        AT1500
            The driver for the AT1500 series is new in the
            0.99pl12 kernel, but it won't work "out-of-the-box"
            with >16M machines. (NB This isn't a fundamental
            limitation, so stop pointing and laughing at the ISA
            bus. The driver just needs a hook to allocate
            low-memory buffers for the bus-master DMA, and should
            be just as fast on >16M systems. It can be easily
            fixed by initializing the LANCE driver with the
            character devices, but this fix depends on the
            resolution of the networking code uncertainty.)

            For the ISA bus master mode all structures used
            directly by the LANCE, the initialization block,
            Rx and Tx rings, and data buffers, must be accessible
            from the ISA bus, i.e. in the lower 16M of real memory.
            This is a problem for current Linux kernels on >16M
            machines. The network devices are initialized after
            memory initialization, and the kernel doles out memory
            from the top of memory downward. The current solution
            is to have a special network initialization routine
            that's called before memory initialization; this will
            eventually be generalized for all network devices.
            Low-memory "bounce-buffers" are used when needed.

            This driver should also work with NE1500 and NE2100
            clones.

            Future driver versions may figure out a way to
            autoDMA. Although there is no autoDMA (until I verify
            that autoDMA is safe and reliable), some versions
            (pl13) allow passing the DMA channel at boot-time via
            LILO. (Boot-time parameters can be made permanent in
            LILO v13+, read the docs.) The DMA channel otherwise
            defaults to DMA5.

            In pl14, there was a buglet that would hang some
            machines with AT1500 like cards. Either get pl15
            or newer, or go into ./init/main.c and move the
            sti(); and claibrate_delay(); (near line 366) in
            *front of* the #ifdef CONFIG_INET, instead of
            after it.

            Please report the exact chip used by your ethercard,
            and any success or failure you have. This driver is
            still young, and I've gotten few reports.

            More information on AMD LANCE based Ethernet cards
            can be found in section 5.08.

        AT1700
            The Allied Telesis AT1700 series ethercards are based
            on the Fujitsu MB86965. This chip uses a programmed
            I/O interface, and a pair of fixed-size transmit
            buffers. This allows small groups of packets to sent
            be sent back-to-back, with a short pause while
            switching buffers.

            A unique feature is the ability to drive 150ohm STP
            (Shielded Twisted Pair) cable commonly installed for
            Token Ring, in addition to 10baseT 100ohm UTP
            (unshielded twisted pair).

            A mis-feature to watch out for is that the current
            production version silently wires to DMA channel 5,
            rendering it useless. No device driver will be
            written using DMA if installing a second card into
            the machine breaks both, and the only way to disable
            the DMA is with a knife.

            The at1700 driver is included in the standard pl15
            kernel source tree.

2.08 Arcnet

    There is no Arcnet driver for Linux. Feel free to write a driver. With
    the very low cost and better performance of ethernet, I expect that
    most places will be giving away their Arcnet hardware for free,
    resulting in a lot of home systems with Arcnet.

    An advantage of Arcnet is that all of the cards have identical
    interfaces, so once a driver is available it will work for everyone.

    If you are feeling brave, there is "arcnet.c" in the usual place
    (see the FAQ section if you don't know where that is) that you
    can play with. Don't expect to just plug in this file and have
    everything work. However it may prove to be a good starting point
    for a bored driver-hacker. Also look at Russ Nelson's "arcether"
    packet driver.

2.09 Digital / DEC

    Supported: DE200, DE210, DE202, DE100, DEPCA rev E

        As of linux v1.0, there is a driver included as standard
        for these cards. It was written by David C. Davies.
        There is documentation included in the source file
        "depca.c", which includes info on how to use more than
        one of these cards in a machine.

        If you have / want to use the pl15 kernel or older,
        then you will have to use Peter Bauer's driver.
        It can be found as a separate patch called depca-0.8.tar.gz.
        You will have to un-comment the DEPCA line in "config.in"
        after installing the patch. You can find the patch on
        ftp.funet.fi, /pub/OS/Linux/BETA/depca/depca-0.8.tar.gz
        This version resets the card upon close so that you can
        use it with broken DOS drivers after a warm boot.


    Unsupported: Digital Etherlink III

        Peter Bauer said that "the new etherlink III seems to
        be a break: No official docu from DEC as far as today,
        other (incompatible??) hardware used, and (no joke) (at least
        for the first delivered cards) also a sharp knife necessary
        to get the card working (needs cut of some irq lines ...)
        As far as I know, lots of DEC Employees use Linux (at least
        for hobby purposes) and the depca-driver, because its a
        de-facto standard in DEC, so I encourage any DEC-employee
        reading this to check wether my writing is true, and to
        support sources of information about the etherworks-III."

2.10 Intel Ethernet Cards

    Supported: Ether Express

        This card uses the intel i82586. (Surprise, huh?)
        The driver is in the standard release of pl15.
        However, you will have to uncomment the line in
        "config.in" to use it. -- yes, this line is
        commented out for a reason. The driver is still
        in the testing phases, as of v1.0 as well.

        There is some technical information available on
        the i82586 in section 5.06, and also in the
        source code for the driver "eexpress.c". Don't
        be afraid to read it. ;-)

        The rason is that the driver works well with slow machines,
        but the i82586 occasionally hangs from the packet buffer
        contention that a fast machine can cause. I'll have
        to find a work-around before releasing the driver.
        One reported hack fix is to change all of the outw()
        calls to outw_p().


        If you do try the driver please post or send a report.
        Include the kind of machine you are trying it with,
        and how heavily loaded your network is.


2.11 PureData

    Supported: PDUC8028, PDI8023

        The PureData PDUC8028 and PDI8023 series of cards are reported
        to work, thanks to special probe code contributed by Mike
        Jagdis <[e-mail]>. The support is integrated
        with the WD driver.

2.12 Xircom

    Another group that won't release documentation. No cards
    supported. Don't look for any support in the future unless
    they release their programming information. And this is
    highly unlikely, as they *forbid* you from even reverse-
    engineering their drivers. If you are already stuck with one,
    see if you can trade it off on some DOS (l)user. Read section
    9.01 if you are bored.

    And if you just want to verify that this is the case, you can
    reach Xircom at 1-800-874-7875 or [phone].

2.13 Zenith

    The built-in Z-Note network adaptor is based on the Intel
    i82593 using two DMA channels. There is an alpha driver
    available at the moment. Look for "znet.c" in the usual
    place. (See the FAQ section if you don't know where that
    is.) See section 5.06 for more technical information.
    Also note that the IBM ThinkPad 300 is compatible with the Z-Note.

2.14 Racal-Interlan

    Note: I have been told that the following two drivers are
    for patchlevel 11, and hence are a bit dated. The original
    author is Michael Hipp, and can be reached at the following addr:
        [e-mail]

    NI52**

    There is an alpha driver for the NI5210 floating about.
    (last seen on tsx-11.mit.edu /pub/linux/ALPHA/ni/ni52.tar.gz)
    This card also uses one of the Intel chips. See section
    5.06 for more technical information.

    NI65**

    There is also a driver for the LANCE based NI6510, and it
    can be found in the same place as the NI5210 driver above.
    I am not sure how much work it would be to hack the current
    LANCE driver in the kernel to support this card. If anyone
    has done so, let me know.

2.15 AMD LANCE (79C960)

    There really is no AMD ethernet card. You are probably reading this
    because the only markings you could find on your card said AMD
    and the above number. The above number refers to a chip from AMD
    that is the heart of many ethernet cards. See the section on the
    Allied Telesis AT1500, the NE1500/2100 and the information in
    section 5.08. Chances are that the existing LANCE driver will work
    with all AMD LANCE based cards. (...except perhaps the above
    mentioned NI6510 ???)

2.16 AT-Lan-Tec / RealTek Pocket adaptor

    This is a generic, low-cost OEM pocket adaptor being sold by
    AT-Lan-Tec, and (likely) a number of other suppliers. A
    driver for it is included in the standard pl15 kernel.
    Note that there is substantial information contained in the
    driver source file "atp.c" which presently lives in ./drivers/net/
    BTW, the adaptor (AEP-100L) has both 10baseT and BNC connections!
    You can reach AT-Lan-Tec at 1-301-948-7070. Ask for the model
    that works with Linux, or ask for "Vincent Bono" in tech support.
    In the Netherlands a compatible adaptor is sold under the name SHI-TEC
    PE-NET/CT, and sells for about $125. The vendor was Megasellers.
    They state that they do not sell to private persons, but I just
    gave them the name of my home institute. No questions asked.
    They are: Megasellers, Vianen, The Netherlands. They always
    advertise in Dutch computer magazines. In Germany, a similar
    adaptor comes as a no-brand-name product. Prolan 890b, no
    brand on the casing, only a roman II. Resellers can get a price
    of about $130, including a small wall transformer for the power.

    Physical Description

    The adaptor is "normal size" for the product class, about 57mm wide,
    22mm high tapering to 15mm high at the DB25 connector, and 105mm long
    (120mm including the BNC socket). It's switchable between the RJ45
    and BNC jacks with a small slide switch positioned between the two:
    a very intuitive design.

    It's powered by a lightweight 5V "wall brick" adaptor that terminates
    in a standard 5.0mm power connector. I measured an unconnected
    quiescent power draw of 102ma for BNC and 84ma for 10baseT. I hooked
    the pocket adaptor up to my home thinnet and started FTPing a large
    file. The power measurements were:

        idle, connected        99ma @ 5.1V
        active, connected    107ma @ 5.1V

    This was measured using a Fluke 8026B true-RMS multimeter, so I'm
    pretty confident the numbers are good. This power draw is low enough
    that you could buy or build a cable to take the 5V directly from the
    keyboard/mouse port available on many laptops. (Bonus points here
    for using a standardized power connector instead of proprietary one.)

2.17 Ansel

    Supported: AC3200 EISA

        This driver is not included in the pl15 kernel. To
        *alpha* test it, get the files ac3200.[c,h] from
        where you usually get alpha drivers (see the FAQ in
        this document if you dont know) and uncomment the
        line in config.in for the ac3200. If you use it,
        please let me know how things work out.

2.18 DFI

    Supported: DFINET-300 (NE1000) and DFINET-400 (NE2000)

        These cards are now detected (as of pl15) thanks to
        Eberhard Moenkeberg <[e-mail]> who noted that
        they use "DFI" in the first 3 bytes of the prom, instead
        of using 0x57 in bytes 14 and 15, which is what all the
        NE1000 and NE2000 cards use.

2.19 IBM

    Supported: IBM Thinkpad 300

        This is compatible with the Intel based Zenith Z-note.
        See the above section on the Zenith for more info.

3. 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 question and answer section of this document.

    Also note that if your card isn't mentioned here, that really
    means nothing. Chances are that even if it is only a half decent
    clone of the original, then it will still work.

3.01 WD80x3 clones

    The following clones are reported to work with the standard
    WD80x3 driver:

    AT-LAN-TEC 8013
    PureData (not a 8013 clone, but the 8013 driver has special code)
    LANNET LEC-45
    PE-8013 (WD-8013 Compatible)

3.02 NE2000 clones

    The following clones are reported to work with the standard
    NE2000 driver:

    Accton NE2000 (might not get detected at boot, see section 6)
    Alta Combo NE2000 clone
    Aritsoft LANtastic AE-2 (OK, but has flawed error-reporting registers)
    Asante Etherpak 2001/2003
    AT-LAN-TEC NE2000 clone (uses Winbond chip that traps SCSI drivers)
    Cabletron products: E10**, E10**-x, E20**, E20**-x
    Cnet UTP 10baseT (NE 2000 emulation)
    D-Link Ethernet II (bad clones, but the driver checks for them)
    4-Dimension FD0490 EtherBoard16
    LTC E-NET/16 P/N: 8300-200-002 ([e-mail])
    Network Solutions HE-203
    SIIG Inc E-Lan/200 (NE 2000 comp.)
    SVEC 4 Dimension Ethernet

4. Cables, coax, twisted pairs etc.

    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.

4.01 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!


4.02 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."

4.03 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.

5 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.

5.01 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. As of 0.99pl12, doing a "make config"
    will ask what cards are to be supported. The file names below are
    in /usr/src/linux/drivers/net/
    ----------------------------------------------------------------
    wd.c:        0x300, 0x280, 0x380, 0x240
    3c501.c        0x280
    3c503.c:    0x300, 0x310, 0x330, 0x350, 0x250, 0x280, 0x2a0, 0x2e0
    3c507.c:    0x300, 0x320, 0x340, 0x280
    3c509.c:    <Special "ID Port" probe>
    at1700.c:    0x300, 0x280, 0x380, 0x320, 0x340, 0x260, 0x2a0, 0x240
    atp.c:        0x378, 0x278, 0x3bc
    depca.c        0x300, 0x200
    d_link.c:    0x378
    ne.c:        0x300, 0x280, 0x320, 0x340, 0x360
    hp.c:        0x300, 0x320, 0x340, 0x280, 0x2C0, 0x200, 0x240
    lance.c:    0x300, 0x320, 0x340, 0x360
    smc-ultra.c:    0x200, 0x220, 0x240, 0x280, 0x300, 0x340, 0x380
    eexpress.c:    0x300, 0x270, 0x320, 0x340
    3c509.c:    <Special "ID Port" probe>
    ----------------------------------------------------------------
    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 Section 9

5.02 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 require-
    ments ;-) 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
    <[e-mail]> has been actively updating and writing these,
    and he has been very helpful with his code reviews of the current
    Linux drivers.

5.03 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 'config' or '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).

    (Note: As of NET-2, the relevant program is '/etc/ifconfig' - and
    the device *can* be turned off or on via passing 'up' or 'down'
    to 'ifconfig' from the command line with the device name.)

    =====================================================

    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).
    [[Note: pre0.99.4 kernels didn't use this interface for all packets.]]

    =====================================================

    ...
        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 sa_data[]. 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).

    =====================================================

5.04 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 an
    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 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."


5.05 Programmed I/O vs. shared mem. vs. slave/master 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:

    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.

    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.

    Slave (normal) DMA
    ==================
      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.

    Master (bus-master) DMA
    =======================
      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.

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 <[e-mail]>
    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
    [e-mail] 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
    [e-mail] 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
    [e-mail].

    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: [e-mail]
    home: [e-mail]

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 [phone] 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."

    AMD recently announced additional members of the PCnet(tm) family.
    The new parts are PCnet-ISA+ (Am79C961), PCnet-32 (Am79C965), and
    PCnet-PCI (Am79C970).

    PCnet-ISA+ is an update to the wildly successful PCnet-ISA, single
    chip Ethernet controller for ISA-bus.  It includes support for
    jumperless configuration and Microsoft Plug-and-Play for ISA.

    PCnet-32 is a high performance, 32-bit bus master, single chip
    Ethernet controller for VL-bus and 386/486 Local Bus.

    PCnet-PCI is similar to PCnet-32, but designed for the new PCI local
    bus.

    As always, all the members of the PCnet family are driver compatible,
    although new features have been added to these parts and drivers would
    have to be updated to take advantage of them.

    Expect to see both adapter cards and *motherboards* appearing soon
    from major networking and PC vendors with these parts on them."

    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,
       <[e-mail]> 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 [e-mail] - 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

          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.

6.04 Problems with Hewlett Packard Cards

    IRQ and DMA channel problems.
    =============================

    Problem:  HP Vectra using 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 *always* uses
          the value in the setup register of an HP Lance
          implementation.  In this case it's reading an invalid
          0xff value. You should either hardcode the proper IRQ
          and DMA into the driver, or pass them to the kernel
          via LILO. In the meantime I'll see if I can find someone
          at HP that knows how to tell the difference between a
          J2405A and a Vectra.  If there isn't an easy way, I'll
          just ignore a 0xff setup value and do autoIRQ/autoDMA
          instead.

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.

    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.

    Things are looking up for Linux users that want PCMCIA support, as
    H.J. Lu is also working on getting the PCMCIA chipset support
    issue sorted out. We have all seen the excellent work he has
    already done with the shared library and the gcc support for
    Linux. Thanks HJ!

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: 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.

       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: What can I do to communicate with DOS clients and DOS/Windows
       PCs on my network? Can I run any Novell stuff? Or how about
       Lan-Manager stuff?

    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." Note that the IPX stuff is
       incuded in the standard kernels as of about 1.1.X

       Other people have been running DOS packet drivers under the Linux
       DOSEMU to connect to LANs running Novell servers. It works but
       it is a bit clunky, and you can't then use the ethercard under
       Linux at the same time.

       I think the cleanest and nicest solution is for those running
       Lan-Manager compatible clients (e.g. Windows for Workgroups,
       Windows NT, etc.) -- there is a free Unix server available with
       very flexible functionality from nimbus.anu.edu, in the dir
       /pub/tridge/server  (thanks to [e-mail])
       This server also has a client part that allows you to connect
       to other servers from your Unix machine, allowing printing, etc.
       Also, you can also get *free* DOS clients from ftp.microsoft.com
       in the directory Advsys/MSclient/

       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. It has been hinted at that you need to
       be careful when installing SOSS so that you don't compromise
       the security of the Novell side of things. Make sure the
       admin of the Novell side of things knows what you are up to.

       I have also heard recently of a DOS shareware NFS *client*
       (DOS NFS *servers* are nothing new) that will allow you to
       access your Unix files via NFS. It is supposed to be on
       polyslo.calpoly.edu on /pub/mdurkin/nfs -- thats all I know.
       Again, be careful that you don't compromise the security of
       Linux NFS server.

       And don't forget good old NCSA telnet for DOS. It is mirrored
       on a zillion ftp sites, and the current version is 2.3.07
       As with Linux v1.0, NCSA telnet seems to work fine with the
       Linux networking code, without any strange hangs, etc. You
       can thank Alan and crew for that.

    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,
       and Section 9, where there are tips on using LILO to pass
       boot-time 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.

    Q: What is the selection for 32 bit ethernet cards?

    A: 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.

       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 well under $100 -- perhaps $70 from a place like CMO
       (see Computer Shopper).

       While this board has a backwards-compatible mode that should work
       with the existing LANCE driver, I might write a driver for the
       faster enhanced mode.  More on that story as it develops...

    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."

       Alan Cox also notes that you are usually much better off to use
       an old unused AT/286 and dedicated software like "kbridge"
       (the free of the commercial version). An old AT plus a couple
       of cheap ethernet cards, and you are in business.

    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 Passing Ethernet Arguments to the Kernel via LILO

    Here is a generic lilo command that would be typed after the name
    of your configuration in your lilo.conf file (usually "linux")

    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.]]

    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.

9.02 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

9.03 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        <[e-mail]>
    Donald J. Becker    <[e-mail]>

        =========== end of Ethernet HOWTO ============