DP Tool Club 15/CD_ASCQ_15_070894.iso/vrac/how_to.zip/ETHER2.HOW

Text File | 1994-04-29 | 38KB | 846 lines

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


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

5.06 Programming the Intel chips (i82586 and i82593)

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

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

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

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

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

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

5.07 Technical information from 3Com

 From: Cameron Spitzer 764-6339 <[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."

 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

7 Networking with a laptop computer

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

7.01 Option 1 -- using SLIP

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

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

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

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

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

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

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

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

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

7.04 Option 4 -- Pocket / parallel port adaptors.

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

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

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

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

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

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

8.01 Just the FAQ's ma'am -- just the FAQ's.

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

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

 Q: Is there token ring support for Linux?

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

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

 Q: Is there FDDI support for Linux?

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

9 Miscellaneous.

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

9.01 Bad Vendors

 #define SOAPBOX

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

 #undef SOAPBOX

9.02 Closing

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

 Paul Gortmaker  <[e-mail]>
 Donald J. Becker <[e-mail]>