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Subject: Linux Ethernet HOWTO (part 2/2) Newsgroups: comp.os.linux.announce,comp.os.linux.admin,comp.answers,news.answers,comp.dcoms.lan.ethernet,comp.sys.ibm.pc.hardware.networking,aus.computers.linux From: Paul Gortmaker <gpg109@rsphysse.anu.edu.au> Date: Fri, 18 Nov 1994 17:05:21 GMT Archive-Name: linux/howto/ethernet/part2 Last-modified: 20 Oct 94 ---This is part 2/2--- And if you just want to verify that this is the case, you can reach Xircom at 1-800-874-7875 or +1-818-878-7600. 3.25.1. PE1, PE2, PE3-10B* Status -- Not Supported Not to get your hopes up, but if you have one of these parallel port adaptors, you may be able to use it in the DOS emulator with the Xircom-supplied DOS drivers. You will have to allow DOSEMU access to your parallel port, and will probably have to play with SIG (DOSEMU's Silly Interrupt Generator). I have no idea if this will work, but if you have any success with it, let me know, and I will include it here. 3.26. Zenith 3.26.1. Z-Note Status -- Supported The built-in Z-Note network adaptor is based on the Intel i82593 using two DMA channels. There is an (alpha?) driver available in the present kernel version. As with all notebook and pocket adaptors, it is under the `Pocket and portable adaptors' section when running make config. See ``Programming the Intel chips'' for more technical information. Also note that the IBM ThinkPad 300 is compatible with the Z-Note. 4. Clones of popular Ethernet cards. Due to the popular design of some cards, different companies will make `clones' or replicas of the original card. However, one must be careful, as some of these clones are not 100 % compatible, and can be troublesome. Some common problems with `not-quite-clones' are noted in ``the FAQ section''. This section used to have a listing of a whole bunch of clones that were reported to work, but seeing as nearly all clones will work, it makes more sense to list the ones that don't work 100 % . 4.1. NE2000 Clones with Problems Here is a list of some of the NE-2000 clones that are known to have various problems. Most of them aren't fatal. In the case of the ones listed as `bad clones' -- this usually indicates that the cards don't have the two NE2000 identifier bytes. NEx000-clones have a Station Address PROM (SAPROM) in the packet buffer memory space. NE2000 clones have 0x57,0x57 in bytes 0x0e,0x0f of the SAPROM, while other supposed NE2000 clones must be detected by their SA prefix. Accton NE2000 -- might not get detected at boot, see ``ne2000 problems''. Aritsoft LANtastic AE-2 -- OK, but has flawed error-reporting registers. AT-LAN-TEC NE2000 -- clone uses Winbond chip that traps SCSI drivers Cabletron E10**, E20**, E10**-x, E20**-x -- bad clones, but the driver checks for them. See ``E10**''. D-Link Ethernet II -- bad clones, but the driver checks for them. See ``DE-100 / DE-200''. DFI DFINET-300, DFINET-400 -- bad clones, but the driver checks for them. See ``DFI-300 / DFI-400'' 4.2. WD8013 Clones with Problems I haven't heard of any bad clones of these cards, except for some chamelion-type cards that can be set to look like a ne2000 card or a wd8013 card. There is really no need to purchase one of these `double- identity' cards anyway. 5. Cables, Coax, Twisted Pair If you are starting a network from scratch, it's considerably less expensive to use thin ethernet, RG58 co-ax cable with BNC connectors, than old-fashioned thick ethernet, RG-5 cable with N connectors, or 10baseT, twisted pair telco-style cables with RJ-45 eight wire `phone' connectors. See ``Type of cable...'' for an introductory look at cables. 5.1. Thin Ethernet (thinnet) Thin ethernet is the `ether of choice'. The cable is inexpensive. If you are making your own cables solid-core RG58A is $0.09/ft. and stranded RG58AU is $0.15/ft. Twist-on BNC connectors are < $2 ea., and other misc. pieces are similarly inexpensive. It is essential that you properly terminate each end of the cable with 50 ohm terminators, so budget $2 ea. for a pair. It's also vital that your cable have no `stubs' -- the `T' connectors must be attached directly to the ethercards. The only drawback is that if you have a big loop of machines connected together, and some bonehead breaks the loop by taking one cable off the side of his tee, the whole network goes down because it sees an infinite impedance (open circuit) instead of the required 50 ohm termination. Note that you can remove the tee piece from the card itself without killing the whole subnet, as long as you don't remove the cables from the tee itself. Of course this will disturb the machine that you pull the actual tee off of. 8-) And if you are doing a small network of two machines, you *still* need the tees and the 50 ohm terminators -- you *can't* just cable them together! 5.2. Twisted Pair Twisted pair networks require active hubs, which start around $200, and the raw cable cost can actually be higher than thinnet. They are usually sold using the claim that you can use your existing telephone wiring, but it's a rare installation where that turns out to be the case. The claim that you can upgrade to higher speeds is also suspect, as most proposed schemes use higher-grade (read $$) cable and more sophisticated termination ($$$) than you would likely install on speculation. New gizmos are floating around which allow you to daisy- chain machines together, and the like. For example, Falleron sells EtherWave adaptors and transceivers. This device allows multiple 10baseT devices to be daisy-chained. They also sell a 3c509 clone that includes the EtherWave transceiver. The drawback is that it's more expensive and less reliable than a cheap ($100-$150) mini-hub and another ethercard. IMO, you should either go for the hub approach or switch over to 10base2 thinnet. On the other hand, hubs are rapidly dropping in price, all 100Mb/sec ethernet proposals use twisted pair, and most new business installations use twisted pair. (This is probably to avoid the problem with idiots messing with the BNC's as described above.) If you are only connecting two machines, it is possible to avoid using a hub, by swapping the Rx and Tx pairs (1-2 and 3-6). Also, Russ Nelson adds that `New installations should use Category 5 wiring. Anything else is a waste of your installer's time, as 100Base- whatever is going to require Cat 5.' 5.3. Thick Ethernet Thick ethernet is mostly obsolete, and is usually used only to remain compatible with an existing implementation. You can stretch the rules and connect short spans of thick and thin ethernet together with a passive $3 N-to-BNC connector, and that's often the best solution to expanding an existing thicknet. A correct (but expensive) solution is to use a repeater in this case. 6. Technical Information For those who want to play with the present drivers, or try to make up their own driver for a card that is presently unsupported, this information should be useful. If you do not fall into this category, then perhaps you will want to skip this section. 6.1. Probed Addresses While trying to determine what ethernet card is there, the following addresses are autoprobed, assuming the type and specs of the card have not been set in the kernel. The file names below are in /usr/src/linux/drivers/net/ ______________________________________________________________________ 3c501.c 0x280, 0x300 3c503.c: 0x300, 0x310, 0x330, 0x350, 0x250, 0x280, 0x2a0, 0x2e0 3c505.c: 0x300, 0x280, 0x310 3c507.c: 0x300, 0x320, 0x340, 0x280 3c509.c: Special ID Port probe apricot.c 0x300 at1700.c: 0x300, 0x280, 0x380, 0x320, 0x340, 0x260, 0x2a0, 0x240 atp.c: 0x378, 0x278, 0x3bc depca.c 0x300, 0x200 d_link.c: 0x378 eexpress.c: 0x300, 0x270, 0x320, 0x340 hp.c: 0x300, 0x320, 0x340, 0x280, 0x2C0, 0x200, 0x240 hp-plus.c 0x200, 0x240, 0x280, 0x2C0, 0x300, 0x320, 0x340 lance.c: 0x300, 0x320, 0x340, 0x360 ne.c: 0x300, 0x280, 0x320, 0x340, 0x360 ni52.c 0x300, 0x280, 0x360, 0x320, 0x340 ni65.c 0x300, 0x320, 0x340, 0x360 smc-ultra.c: 0x200, 0x220, 0x240, 0x280, 0x300, 0x340, 0x380 wd.c: 0x300, 0x280, 0x380, 0x240 ______________________________________________________________________ There are some NE2000 clone ethercards out there that are waiting black holes for autoprobe drivers. While many NE2000 clones are safe until they are enabled, some can't be reset to a safe mode. These dangerous ethercards will hang any I/O access to their `dataports'. The typical dangerous locations are: ______________________________________________________________________ Ethercard jumpered base Dangerous locations (base + 0x10 - 0x1f) 0x300 * 0x310-0x317 0x320 0x330-0x337 0x340 0x350-0x357 0x360 0x370-0x377 ______________________________________________________________________ * The 0x300 location is the traditional place to put an ethercard, but it's also a popular place to put other devices (often SCSI controllers). The 0x320 location is often the next one chosen, but that's bad for for the AHA1542 driver probe. The 0x360 location is bad, because it conflicts with the parallel port at 0x378. To avoid these lurking ethercards, here are the things you can do: o Probe for the device's BIOS in memory space. This is easy and always safe, but it only works for cards that always have BIOSes, like primary SCSI controllers. o Avoid probing any of the above locations until you think you've located your device. The NE2000 clones have a reset range from <base>+0x18 to <base>+0x1f that will read as 0xff, so probe there first if possible. It's also safe to probe in the 8390 space at <base>+0x00 - <base>+0x0f, but that area will return quasi-random values o If you must probe in the dangerous range, for instance if your target device has only a few port locations, first check that there isn't an NE2000 there. You can see how to do this by looking at the probe code in /usr/src/linux/net/inet/ne.c o Use the `reserve' boot time argument to protect volatile areas from being probed. See the information on using boot time arguments with LILO in ``The reserve command'' 6.2. Skeleton / prototype driver OK. So you have decided that you want to write a driver for the Foobar Ethernet card, as you have the programming information, and it hasn't been done yet. (...these are the two main requirements ;-) You can use the skeleton network driver that is provided with the Linux kernel source tree. It can be found in the file /usr/src/linux/drivers/net/skeleton.c as of 0.99pl15, and later. It's also very useful to look at the Crynwr (nee Clarkson) driver for your target ethercard, if it's available. Russ Nelson nelson@crynwr.com has been actively updating and writing these, and he has been very helpful with his code reviews of the current Linux drivers. 6.3. Driver interface to the kernel Here are some notes that may help when trying to figure out what the code in the driver segments is doing, or perhaps what it is supposed to be doing. ______________________________________________________________________ int ethif_init(struct device *dev) { ... dev->send_packet = &ei_send_packet; dev->open = &ei_open; dev->stop = &ei_close; dev->hard_start_xmit = &ei_start_xmit; ... } int ethif_init(struct device *dev) ______________________________________________________________________ This function is put into the device structure in Space.c. It is called only at boot time, and returns `0' iff the ethercard `dev' exists. ______________________________________________________________________ static int ei_open(struct device *dev) static int ei_close(struct device *dev) ______________________________________________________________________ This routine opens and initializes the board in response to an socket ioctl() usually called by `ifconfig'. It is commonly stuffed into the `struct device' by ethif_init(). The inverse routine is ei_close(), which should shut down the ethercard, free the IRQs and DMA channels if the hardware permits, and turn off anything that will save power (like the transceiver). ______________________________________________________________________ static int ei_start_xmit(struct sk_buff *skb, struct device *dev) dev->hard_start_xmit = &ei_start_xmit; ______________________________________________________________________ This routine puts packets to be transmitted into the hardware. It is usually stuffed into the `struct device' by ethif_init(). When the hardware can't accept additional packets it should set the dev->tbusy flag. When additional room is available, usually during a transmit-complete interrupt, dev->tbusy should be cleared and the higher levels informed with mark_bh(INET_BH). ______________________________________________________________________ if (dev_rint(buffer, length, is_skb ? IN_SKBUFF : 0, dev)) stats->rx_dropped++; ______________________________________________________________________ A received packet is passed to the higher levels using dev_rint(). If the unadorned packet data in a memory buffer, dev_rint will copy it into a `skbuff' for you. Otherwise a new skbuff should be kmalloc()ed, filled, and passed to dev_rint() with the IN_SKBUFF flag. ______________________________________________________________________ int s=socket(AF_INET,SOCK_PACKET,htons(ETH_P_ALL)); ______________________________________________________________________ Gives you a socket receving every protocol type. Do recvfrom() calls to it and it will fill the sockaddr with device type in sa_family and the device name in the sa_data array. I don't know who originally invented SOCK_PACKET for Linux (its been in for ages) but its superb stuff. You can use it to send stuff raw too (both only as root). 6.4. Interrupts and Linux There are two kinds of interrupt handlers in Linux: fast ones and slow ones. You decide what kind you are installing by the flags you pass to irqaction(). The fast ones, such as the serial interrupt handler, run with _all_ interrupts disabled. The normal interrupt handlers, such as the one for ethercard drivers, runs with other interrupts enabled. There is a two-level interrupt structure. The `fast' part handles the device register, removes the packets, and perhaps sets a flag. After it is done, and interrupts are re-enabled, the slow part is run if the flag is set. The flag between the two parts is set by: mark_bh(INET_BH); Usually this flag is set within dev_rint() during a received-packet interrupt, and set directly by the device driver during a transmit- complete interrupt. You might wonder why all interrupt handlers cannot run in `normal mode' with other interrupts enabled. Ross Biro uses this scenario to illustrate the problem: o You get a serial interrupt, and start processing it. The serial interrupt is now masked. o You get a network interrupt, and you start transferring a maximum- sized 1500 byte packet from the card. o Another character comes in, but this time the interrupts are masked! The `fast' interrupt structure solves this problem by allowing bounded-time interrupt handlers to run without the risk of leaving their interrupt lines masked by another interrupt request. There is an additional distinction between fast and slow interrupt handlers -- the arguments passed to the handler. A `slow' handler is defined as ______________________________________________________________________ static void handle_interrupt(int reg_ptr) { int irq = -(((struct pt_regs *)reg_ptr)->orig_eax+2); struct device *dev = irq2dev_map[irq]; ... ______________________________________________________________________ While a fast handler gets the interrupt number directly ______________________________________________________________________ static void handle_fast_interrupt(int irq) { ... ______________________________________________________________________ A final aspect of network performance is latency. The only board that really addresses this is the 3c509, which allows a predictive interrupt to be posted. It provides an interrupt response timer so that the driver can fine-tune how early an interrupt is generated. Alan Cox has some advice for anyone wanting to write drivers that are to be used with pl14 kernels and newer. He says: `Any driver intended for pl14 should use the new alloc_skb() and kfree_skbmem() functions rather than using kmalloc() to obtain a sk_buff. The new pl14 skeleton does this correctly. For drivers wishing to remain compatible with both sets the define `HAVE_ALLOC_SKB' indicates these functions must be used. In essence replace skb=(struct sk_buff *)kmalloc(size) with skb=alloc_skb(size) and kfree_s(skb,size) with kfree_skbmem(skb,size) /* Only sk_buff memory though */ Any questions should I guess be directed to me (Alan Cox) since I made the change. This is a change to allow tracking of sk_buff's and sanity checks on buffers and stack behaviour. If a driver produces the message'File: ??? Line: ??? passed a non skb!' then it is probable the driver is not using the new sk_buff allocators.' 6.5. Programmed I/O vs. Shared Memory vs. DMA Ethernet is 10Mbs. (Don't be pedantic, 3Mbs and 100Mbs don't count.) If you can already send and receive back-to-back packets, you just can't put more bits over the wire. Every modern ethercard can receive back-to-back packets. The Linux DP8390 drivers come pretty close to sending back-to-back packets (depending on the current interrupt latency) and the 3c509 and AT1500 hardware has no problem at all automatically sending back-to-back packets. The ISA bus can do 5.3MB/sec (42Mb/sec), which sounds like more than enough. You can use that bandwidth in several ways: 6.5.1. Programmed I/O Pro: Doesn't use any constrained system resources, just a few I/O registers, and has no 16M limit. Con: Usually the slowest transfer rate, the CPU is waiting the whole time, and interleaved packet access is usually difficult to impossible. 6.5.2. Shared memory Pro: Simple, faster than programmed I/O, and allows random access to packets. Con: Uses up memory space (a big one for DOS users, only a minor issue under Linux), and it still ties up the CPU. 6.5.3. Slave (normal) Direct Memory Access Pro: Frees up the CPU during the actual data transfer. Con: Checking boundary conditions, allocating contiguous buffers, and programming the DMA registers makes it the slowest of all techniques. It also uses up a scarce DMA channel, and requires aligned low memory buffers. 6.5.4. Master Direct Memory Access (bus-master) Pro: Frees up the CPU during the data transfer, can string together buffers, can require little or no CPU time lost on the ISA bus. Con: Requires low-memory buffers and a DMA channel. Any bus-master will have problems with other bus-masters that are bus-hogs, such as some primitive SCSI adaptors. A few badly-designed motherboard chipsets have problems with bus-masters. And a reason for not using any type of DMA device is using a Cyrix 486 processor designed for plug-in replacement of a 386: these processors must flush their cache with each DMA cycle. (This includes the Cx486DLC, Ti486DLC, Cx486SLC, Ti486SLC, etc.) 6.6. Programming the Intel chips (i82586 and i82593) These chips are used on a number of cards, namely the 3c507 ('86), the Intel EtherExpress 16 ('86), Microdyne's exos205t ('86), the Z-Note ('93), and the Racal-Interlan ni5210 ('86). Russ Nelson writes: `Most boards based on the 82586 can reuse quite a bit of their code. More, in fact, than the 8390-based adapters. There are only three differences between them: o The code to get the Ethernet address, o The code to trigger CA on the 82586, and o The code to reset the 82586. The Intel EtherExpress 16 is an exception, as it I/O maps the 82586. Yes, I/O maps it. Fairly clunky, but it works. Garrett Wollman did an AT&T driver for BSD that uses the BSD copyright. The latest version I have (Sep '92) only uses a single transmit buffer. You can and should do better than this if you've got the memory. The AT&T and 3c507 adapters do; the ni5210 doesn't. The people at Intel gave me a very big clue on how you queue up multiple transmit packets. You set up a list of NOP- > XMIT- > NOP- > XMIT- > NOP- > XMIT- > beginning) blocks, then you set the `next' pointer of all the NOP blocks to themselves. Now you start the command unit on this chain. It continually processes the first NOP block. To transmit a packet, you stuff it into the next transmit block, then point the NOP to it. To transmit the next packet, you stuff the next transmit block and point the previous NOP to *it*. In this way, you don't have to wait for the previous transmit to finish, you can queue up multiple packets without any ambiguity as to whether it got accepted, and you can avoid the command unit start-up delay.' 6.7. Technical information from 3Com From: Cameron Spitzer 764-6339 <camerons@nad.3com.com >Subject: getting 3Com Adapter manuals Date: Mon, 27 Sep 1993 21:17:07 +0200 Since this is becoming a FAQ, I'm going to tread the thin ice of No Commercial Use and answer it here. 3Com's Ethernet Adapters are documented for driver writers in our `Technical References' (TRs). These manuals describe the programmer interfaces to the boards but they don't talk about the diagnostics, installation programs, etc that end users can see. The Network Adapter Division marketing department has the TRs to give away. To keep this program efficient, we centralized it in a thing called `CardFacts.' CardFacts is an automated phone system. You call it with a touch-tone phone and it faxes you stuff. To get a TR, call CardFacts at 408-727-7021. Ask it for Developer's Order Form, document number 9070. Have your fax number ready when you call. Fill out the order form and fax it to 408-764-5004. Manuals are shipped by Federal Express 2nd Day Service. If you don't have a fax and nobody you know has a fax, really and truly, *then* send mail to Terry_Murphy@3Mail.3Com.com and tell her about your problem. PLEASE use the fax thing if you possibly can. After you get a manual, if you still can't figure out how to program the board, try our `CardBoard' BBS at 1-800-876-3266, and if you can't do that, write Andy_Chan@3Mail.3com.com and ask him for alternatives. If you have a real stumper that nobody has figured out yet, the fellow who needs to know about it is Steve_Lebus@3Mail.3com.com. There are people here who think we are too free with the manuals, and they are looking for evidence that the system is too expensive, or takes too much time and effort. That's why it's important to try to use CardFacts *before* you start calling and mailing the people I named here. There are even people who think we should be like Diamond and Xircom, requiring tight `partnership' with driver writers to prevent poorly performing drivers from getting written. So far, 3Com customers have been really good about this, and there's no problem with the level of requests we've been getting. We need your continued cooperation and restraint to keep it that way. Cameron Spitzer, 408-764-6339 3Com NAD Santa Clara work: camerons@nad.3com.com home: cls@truffula.sj.ca.us 6.8. Notes on AMD PCnet / LANCE Based cards The AMD LANCE (Local Area Network Controller for Ethernet) was the original offering, and has since been replaced by the `PCnet-ISA' chip, otherwise known as the 79C960. A relatively new chip from AMD, the 79C960, is the heart of many new cards being released at present. Note that the name `LANCE' has stuck, and some people will refer to the new chip by the old name. Dave Roberts of the Network Products Division of AMD was kind enough to contribute the following information regarding this chip: `As for the architecture itself, AMD developed it originally and reduced it to a single chip -- the PCnet(tm)-ISA -- over a year ago. It's been selling like hotcakes ever since. Functionally, it is equivalent to a NE1500. The register set is identical to the old LANCE with the 1500/2100 architecture additions. Older 1500/2100 drivers will work on the PCnet-ISA. The NE1500 and NE2100 architecture is basically the same. Initially Novell called it the 2100, but then tried to distinguish between coax and 10BASE-T cards. Anything that was 10BASE-T only was to be numbered in the 1500 range. That's the only difference. Many companies offer PCnet-ISA based products, including HP, Racal- Datacom, Allied Telesis, Boca Research, Kingston Technology, etc. The cards are basically the same except that some manufacturers have added `jumperless' features that allow the card to be configured in software. Most have not. AMD offers a standard design package for a card that uses the PCnet-ISA and many manufacturers use our design without change. What this means is that anybody who wants to write drivers for most PCnet-ISA based cards can just get the data-sheet from AMD. Call our literature distribution center at (800)222-9323 and ask for the Am79C960, PCnet-ISA data sheet. It's free. A quick way to understand whether the card is a `stock' card is to just look at it. If it's stock, it should just have one large chip on it, a crystal, a small IEEE address PROM, possibly a socket for a boot ROM, and a connector (1, 2, or 3, depending on the media options offered). Note that if it's a coax card, it will have some transceiver stuff built onto it as well, but that should be near the connector and away from the PCnet-ISA.' There is also some info regarding the LANCE chip in the file lance.c which is included in the standard kernel. 6.9. Multicast and Promiscuous Mode One of the things Donald has been working on recently is the major remaining item on the ethercard feature list: implementing multicast and promiscuous mode hooks. All of the released (i.e. not ALPHA) ISA drivers now support promiscuous mode. There was a minor problem with 8390 based cards with capturing multicast packets, in that the promiscuous mode setting in 8390.c around line 574 should be 0x18 and not 0x10. If you have an up to date kernel, this will already be fixed. Donald writes: `At first I was planning to do it while implementing either the /dev/* or DDI interface, but that's not really the correct way to do it. We should only enable multicast or promiscuous modes when something wants to look at the packets, and shut it down when that application is finished, neither of which is strongly related to when the hardware is opened or released. I'll start by discussing promiscuous mode, which is conceptually easy to implement. For most hardware you only have to set a register bit, and from then on you get every packet on the wire. Well, it's almost that easy; for some hardware you have to shut the board (potentially dropping a few packet), reconfigure it, and then re-enable the ethercard. This is grungy and risky, but the alternative seems to be to have every application register before you open the ethercard at boot-time. OK, so that's easy, so I'll move on something that's not quite so obvious: Multicast. It can be done two ways: 1. Use promiscuous mode, and a packet filter like the Berkeley packet filter (BPF). The BPF is a pattern matching stack language, where you write a program that picks out the addresses you are interested in. Its advantage is that it's very general and programmable. Its disadvantage is that there is no general way for the kernel to avoid turning on promiscuous mode and running every packet on the wire through every registered packet filter. See ``The Berkeley Packet Filter'' for more info. 2. Using the built-in multicast filter that most etherchips have. I guess I should list what a few ethercards/chips provide: Chip/card Promiscuous Multicast filter ---------------------------------------- Seeq8001/3c501 Yes Binary filter (1) 3Com/3c509 Yes Binary filter (1) 8390 Yes Autodin II six bit hash (2) (3) LANCE Yes Autodin II six bit hash (2) (3) i82586 Yes Hidden Autodin II six bit hash (2) (4) 1. These cards claim to have a filter, but it's a simple yes/no `accept all multicast packets', or `accept no multicast packets'. 2. AUTODIN II is the standard ethernet CRC (checksum) polynomial. In this scheme multicast addresses are hashed and looked up in a hash table. If the corresponding bit is enabled, this packet is accepted. Ethernet packets are laid out so that the hardware to do this is trivial -- you just latch six (usually) bits from the CRC circuit (needed anyway for error checking) after the first six octets (the destination address), and use them as an index into the hash table (six bits -- a 64-bit table). 3. These chips use the six bit hash, and must have the table computed and loaded by the host. This means the kernel must include the CRC code. 4. The 82586 uses the six bit hash internally, but it computes the hash table itself from a list of multicast addresses to accept. Note that none of these chips do perfect filtering, and we still need a middle-level module to do the final filtering. Also note that in every case we must keep a complete list of accepted multicast addresses to recompute the hash table when it changes. My first pass at device-level support is detailed in the new outline driver skeleton.c It looks like the following: ______________________________________________________________________ #ifdef HAVE_MULTICAST static void set_multicast_list(struct device *dev, int num_addrs, void *addrs); #endif . . ethercard_open() { ... #ifdef HAVE_MULTICAST dev->set_multicast_list = &set_multicast_list; #endif ... #ifdef HAVE_MULTICAST /* Set or clear the multicast filter for this adaptor. num_addrs -- -1 Promiscuous mode, receive all packets num_addrs -- 0 Normal mode, clear multicast list num_addrs > 0 Multicast mode, receive normal and MC packets, and do best-effort filtering. */ static void set_multicast_list(struct device *dev, int num_addrs, void *addrs) { ... ______________________________________________________________________ Any comments, criticism, etc. are welcome.' 6.10. The Berkeley Packet Filter (BPF) I'm not bitterly opposed to it, but I'm coming to the conclusion that the BPF functionality should not be provided by the kernel, but should be in a (hopefully little-used) compatibility library. For those not in the know: BPF (the Berkeley Packet Filter) is an mechanism for specifying to the kernel networking layers what packets you are interested in. It's implemented as a specialized stack language interpreter built into a low level of the networking code. An application passes a program written in this language to the kernel, and the kernel runs the program on each incoming packet. If the kernel has multiple BPF applications, each program is run on each packet. The problem is that it's difficult to deduce what kind of packets the application is really interested in from the packet filter program, so the general solution is to always run the filter. Imagine a program that registers a BPF program to pick up a low data-rate stream sent to a multicast address. Most ethernet cards have a hardware multicast address filter implemented as a 64 entry hash table that ignores most unwanted multicast packets, so the capability exists to make this a very inexpensive operation. But with the BFP the kernel must switch the interface to promiscuous mode, receive _all_ packets, and run them through this filter. This is work, BTW, that's very difficult to account back to the process requesting the packets. 7. Networking with a Laptop/Notebook Computer There are currently only a few ways to put your laptop on a network. You can use the SLIP code (and run at serial line speeds); you can buy one of the few laptops that come with a NE2000-compatible ethercard; you can get a notebook with a supported PCMCIA slot built-in; you can get a laptop with a docking station and plug in an ISA ethercard; or you can use a parallel port Ethernet adapter such as the D-Link DE-600. 7.1. Using SLIP This is the cheapest solution, but by far the most difficult. Also, you will not get very high transmission rates. Since SLIP is not really related to ethernet cards, it will not be discussed further here. See the NET-2 Howto. 7.2. Built in NE2000 This solution severely limits your laptop choices and is fairly expensive. Be sure to read the specifications carefully, as you may find that you will have to buy an additional non-standard transceiver to actually put the machine on a network. A good idea might be to boot the notebook with a kernel that has ne2000 support, and make sure it gets detected and works before you lay down your cash. 7.3. PCMCIA Support As this area of Linux development is fairly young, I'd suggest that you join the LAPTOPS mailing channel. See ``Mailing lists...'' which describes how to join a mailing list channel. Try and determine exactly what hardware you have (ie. card manufacturer, PCMCIA chip controller manufacturer) and then ask on the LAPTOPS channel. Regardless, don't expect things to be all that simple. Expect to have to fiddle around a bit, and patch kernels, etc. Maybe someday you will be able to type `make config' 8-) At present, the two PCMCIA chipsets that are supported are the TCIC/2 and the intel i82365. There is a number of programs on tsx-11.mit.edu in /pub/linux/packages/laptops/ that you may find useful. These range from PCMCIA Ethercard drivers to programs that communicate with the PCMCIA controller chip. Note that these drivers are usually tied to a specific PCMCIA chip (ie. the intel 82365 or the TCIC/2) For NE2000 compatible cards, some people have had success with just configuring the card under DOS, and then booting linux from the DOS command prompt via loadlin. For those that are net-surfing you can try: Don's PCMCIA Stuff (http://cesdis.gsfc.nasa.gov/linux/pcmcia.html) Anyway, the PCMCIA driver problem isn't specific to the Linux world. It's been a real disaster in the MS-DOS world. In that world people expect the hardware to work if they just follow the manual. They might not expect it to interoperate with any other hardware or software, or operate optimally, but they do expect that the software shipped with the product will function. Many PCMCIA adaptors don't even pass this test. Things are looking up for Linux users that want PCMCIA support, as substantial progress is being made. Pioneering this effort is David Hinds. 7.4. ISA Ethercard in the Docking Station. Docking stations for laptops typically cost about $250 and provide two full-size ISA slots, two serial and one parallel port. Most docking stations are powered off of the laptop's batteries, and a few allow adding extra batteries in the docking station if you use short ISA cards. You can add an inexpensive ethercard and enjoy full-speed ethernet performance. 7.5. Pocket / parallel port adaptors. The `pocket' ethernet adaptors may also fit your need. Until recently they actually costed more than a docking station and cheap ethercard, and most tie you down with a wall-brick power supply. At present, you can choose from the D-Link, or the RealTek adaptor. Most other companies, especially Xircom, (see ``Xircom'') treat the programming information as a trade secret, so support will likely be slow in coming. (if ever!) Note that the transfer speed will not be all that great (perhaps 100kB/s tops?) due to the limitations of the parallel port interface. See ``DE-600 / DE-620'' and ``RealTek'' for supported pocket adaptors. You can sometimes avoid the wall-brick with the adaptors by buying or making a cable that draws power from the laptop's keyboard port. (See ``keyboard power'') 8. Frequently Asked Questions Here are some of the more frequently asked questions about using Linux with an Ethernet connection. Some of the more specific questions are sorted on a `per manufacturer basis'. However, since this document is basically `old' by the time you get it, any `new' problems will not appear here instantly. For these, I suggest that you make efficient use of your newsreader. For example, nn users would type nn -xX -s'3c' to get all the news articles in your subscribed list that have `3c' in the subject. (ie. 3com, 3c509, 3c503, etc.) The moral: Read the man page for your newsreader. 8.1. Alpha Drivers -- Getting and Using them I heard that there is an alpha driver available for my card. Where can I get it? The newest of the `new' drivers can be found on Donald's new ftp site: cesdis.gsfc.nasa.gov in the /pub/linux/ area. Things change here quite frequently, so just look around for it. There is still all the stuff on the old ftp site ftp.super.org in /pub/linux, but this is not being actively maintained, and hence will be of limited value to most people. As of recent v1.1 kernels, the `useable' alpha drivers have been included in the standard kernel source tree. When running make config you will be asked if you want to be offered ALPHA test drivers. Now, if it really is an alpha, or pre-alpha driver, then please treat it as such. In other words, don't complain because you can't figure out what to do with it. If you can't figure out how to install it, then you probably shouldn't be testing it. Also, if it brings your machine down, don't complain. Instead, send us a well documented bug report, or even better, a patch! People reading this while net-surfing may want to check out: Don's Linux Home Page (http://cesdis.gsfc.nasa.gov/pub/linux/linux.html) for the latest dirt on what is new and upcoming. 8.2. Using More than one Ethernet Card per Machine What needs to be done so that Linux can run two ethernet cards? The hooks for multiple ethercards are all there. You can enable additional ethercards with LILO parameters such as: LILO: linux ether=5,0x300,0,1,eth0 ether=15,0x280,eth1 These boot time arguments can be made permanent so that you don't have to re-enter them every time. See the LILO manual, and ``Passing Ethernet Arguments...'' where there are tips on using LILO to pass boot-time ethernet card arguments. Also note that only *one* ethercard is auto-probed for, and the second *must* be specified as above. This avoids a lot of possible boot time hangs caused by probing sensitive cards. Probing for the second card can be achieved by using something as simple as ether=0,0,eth1. In this case eth0 and eth1 will be assigned in the order that the cards are found at boot. With the previous example, the user has forced the card at 0x300 to be eth0 and the card at 0x280 to be eth1. Note that if you are intending to use Linux as a gateway between two networks, you will have to re-compile a kernel with IP forwarding enabled. Usually using an old AT/286 with something like the `kbridge' software is a better solution. If you are viewing this while net-surfing, you may wish to look at a mini-howto Donald has on his WWW site. Check out Multiple Ethercards (http://cesdis.gsfc.nasa.gov/linux/misc/multicard.html). 8.3. Problems with NE1000 / NE2000 cards (and clones) Problem: Errors like DMA address mismatch Is the chip a real NatSemi 8390? (DP8390, DP83901, DP83902 or DP83905)? If not, some clone chips don't correctly implement the transfer verification register. MS-DOS drivers never do error checking, so it doesn't matter to them. Are most of the messages off by a factor of 2? If so: Are you using the NE2000 in a 16 bit slot? Is it jumpered to use only 8 bit transfers? The Linux driver expects a NE2000 to be in a 16 bit slot. A NE1000 can be in either size slot. This problem can also occur with some clones, notably D-Link 16 bit cards, that don't have the correct ID bytes in the station address PROM. (This should be fixed in pl12.) Are you running the bus faster than 8Mhz? If you can change the speed (faster or slower), see if that makes a difference. Most NE2000 clones will run at 16MHz, but some may not. Changing speed can also mask a noisy bus. What other devices are on the bus? If moving the devices around changes the reliability, then you have a bus noise problem -- just what that error message was designed to detect. Congratulations, you've probably found the source of other problems as well. Problem: The machine hangs during boot right after the `8390...' or `WD....' message. Removing the NE2000 fixes the problem. Solution: Change your NE2000 base address to 0x360 (or 0x340 for pl12 or later kernels.) Alternatively, you can use the new device registrar implemented in pl13 Reason: Your NE2000 clone isn't a good enough clone. An active NE2000 is a bottomless pit that will trap any driver autoprobing in its space. The other ethercard drivers take great pain to reset the NE2000 so that it's safe, but some clones cannot be reset. Clone chips to watch out for: Winbond 83C901. Changing the NE2000 to a less-popular address will move it out of the way of other autoprobes, allowing your machine to boot. Problem: The machine hangs during the SCSI probe at boot. Reason: It's the same problem as above, change the ethercard's address, or use the device registrar. Problem: The machine hangs during the soundcard probe at boot. Reason: No, that's really during the silent SCSI probe, and it's the same problem as above. Problem: Errors like eth0: DMAing conflict in ne_block_input This bug came from timer-based packet retransmissions. If you got a timer tick _during_ a ethercard RX interrupt, and timer tick tried to retransmit a timed-out packet, you could get a conflict. Because of the design of the NE2000 you would have the machine hang (exactly the same the NE2000-clone boot hangs). Early versions of the driver disabled interrupts for a long time, and didn't have this problem. Later versions are fixed. (ie. kernels after 0.99p9 should be OK.) Problem: NE2000 not detected at boot. Donald writes: `A few people have reported a problem with detecting the Accton NE2000. This problem occurs only at boot-time, and the card is later detected at run-time by the identical code my (alpha- test) ne2k diagnostic program. Accton has been very responsive, but I still haven't tracked down what is going on. I've been unable to reproduce this problem with the Accton cards we purchased. If you are having this problem, please send me an immediate bug report. For that matter, if you have an Accton card send me a success report, including the type of the motherboard. I'm especially interested in finding out if this problem moves with the particular ethercard, or stays with the motherboard.' Here are some things to try, as they have fixed it for some people: o Change the bus speed, or just move the card to a different slot. o Change the `I/O recovery time' parameter in the BIOS chipset configuration. Problem: Network `goes away' every time I print something (NE2000) Reason: You have your NE2000 living at 0x360, and a NE2000 is 0x20 ports wide, putting it to 0x380. Your parallel port is at 0x378 and is stepping on the NE2000 cards I/O space. Jumper it to 0x300 or 0x340 or something like that. 8.4. Problems with WD80*3 cards Problem: A WD80*3 is falsely detected. Removing the sound or MIDI card eliminates the `detected' message. Reason: Some MIDI ports happen to produce the same checksum as a WD ethercard. Solution: Update your ethercard driver: new versions include an additional sanity check. If it is the midi chip at 0x388 that is getting detected as a WD living at 0x380, then you could also use: LILO: linux reserve=0x380,8 Problem: You get messages such as the following with your 80*3: eth0: bogus packet size, status = ........ kmalloc called with impos- sibly large argument (65400) eth0: Couldn't allocate sk_buff of size 65400 eth0: receiver overrun Reason: There is a shared memory problem. Solution: If the problem is sporadic, you have hardware problems. Typical problems that are easy to fix are board conflicts, having cache or `shadow ROM' enabled for that region, or running your bus faster than 8Mhz. There are also a surprising number of memory failures on ethernet cards, so run a diagnostic program if you have one for your ethercard. If the problem is continual, and you have have to reboot to fix the problem, record the boot-time probe message and mail it to becker@cesdis.gsfc.nasa.gov - Take particular note of the shared memory location. Problem: WD80*3 will not get detected at boot. Reason: The Mitsumi CD-ROM (mcd) driver probe at 0x300 will succeed if just about *anything* is that I/O location. This is bad news and needs to be a bit more robust. (pl15) Once another driver registers that it `owns' an I/O location, other drivers (incl. the wd80x3) are `locked out' and can not probe that addr for a card. Solution: Recompile a new kernel without any excess drivers that you aren't using, including the above mcd driver. Or try moving your ethercard to a new I/O addr. Valid I/O addr. for all the cards are listed in ``Probed Addresses'' You can also point the mcd driver off in another direction by a boot-time parameter (via LILO) such as: mcd=0x200,12 8.5. Problems with 3Com cards Problem: The 3c503 picks IRQ n at boot, but this is needed for some other device which needs IRQ n. (eg. CD ROM driver, etc.) Can this be fixed without compiling this into the kernel? Solution: The 3c503 driver probes for a free IRQ line in the order {5, 9/2, 3, 4}, and it should pick a line which isn't being used. The pre- pl12 (SLS 1.02) driver picked the IRQ line at boot-time, and the current driver (pl12) chooses when the card is open()/ifconfig'ed. Alternately, you can fix the IRQ at boot by passing parameters via LILO. The following selects IRQ9, base location 0x300, <ignored value>, and if_port #1 (the external transceiver). LILO: linux ether=9,0x300,0,1,eth0 The following selects IRQ3, probes for the base location, <ignored value>, and the default if_port #0 (the internal transceiver) LILO: linux ether=3,0,0,0,eth0 Problem: 3c503: Configured interrupt number XX is out of range. Reason: Whoever built your kernel fixed the ethercard IRQ at XX. The above is truly evil, and worse than that, it is not necessary. The 3c503 will autoIRQ when it gets ifconfig'ed, and pick one of IRQ{5, 2/9, 3, 4}. Solution: Use LILO as described above, or rebuild the kernel, enabling autoIRQ by not specifying the IRQ line. Problem: The supplied 3c503 drivers don't use the AUI (thicknet) port. How does one choose it over the default thinnet port? Solution: The 3c503 AUI port can be selected at boot-time with 0.99pl12 and later. The selection is overloaded onto the low bit of the currently-unused dev->rmem_start variable, so a boot-time parameter of: LILO: linux ether=0,0,0,1,eth0 should work. A boot line to force IRQ 5, port base 0x300, and use an external transceiver is: LILO: linux ether=5,0x300,0,1,eth0 Also note that kernel revisions 1.00 to 1.03 had an interesting `feature'. They would switch to the AUI port when the internal transciever failed. This is a problem, as it will *never* switch back if for example you momentarily disconnect the cable. Kernel versions 1.04 and newer only switch if the very first Tx attempt fails. 8.6. Problems with Hewlett Packard Cards Problem: HP Vectra using built in AMD LANCE chip gets IRQ and DMA wrong. Solution: The HP Vectra uses a different implementation to the standard HP-J2405A. The `lance.c' driver used to always use the value in the setup register of an HP Lance implementation. In the Vectra case it's reading an invalid 0xff value. Kernel versions newer than about 1.1.50 now handle the Vectra in an appropriate fashion. Problem: HP Card is not detected at boot, even though kernel was compiled with `HP PCLAN support'. Solution: You probably have a HP PCLAN+ -- note the `plus'. Support for the PCLAN+ was added to final versions of 1.1, but some of them didn't have the entry in `config.in'. If you have the file hp-plus.c in /linux/drivers/net/ but no entry in config.in, then add the following line under the `HP PCLAN support' line: bool 'HP PCLAN Plus support' CONFIG_HPLAN_PLUS n Kernels up tp 1.1.54 are missing the line in `config.in' still. Do a `make mrproper;make config;make dep;make zlilo' and you should be in business. 8.7. FAQs Not Specific to Any Card. 8.7.1. Token Ring Is there token ring support for Linux? To support token ring requires more than only a writing a device driver, it also requires writing the source routing routines for token ring. It is the source routing that would be the most time comsuming to write. Alan Cox adds: `It will require (...) changes to the bottom socket layer to support 802.2 and 802.2 based TCP/IP. Don't expect anything soon.' Peter De Schrijver has been spending some time on Token Ring lately, and has patches that are available for IBM ISA and MCA token ring cards. Don't expect miracles here, as he has just started on this as of 1.1.42. You can get the patch from: aix13ps2.cc.kuleuven.ac.be:/pub/Linux/TokenRing.patch-1.1.49.gz 8.7.2. 32 Bit / VLB / PCI Ethernet Cards What is the selection for 32 bit ethernet cards? There aren't many 32 bit ethercard device drivers because there aren't that many 32 bit ethercards. There aren't many 32 bit ethercards out there because a 10Mbs network doesn't justify spending the 5x price increment for the 32 bit interface. See ``Programmed I/O vs. ...'' as to why having an ethercard on an 8MHz ISA bus is really not a bottleneck. This might change now that AMD has introduced the 32 bit PCnet-VLB and PCnet-PCI chips. The street price of the Boca PCnet-VLB board should be under $70 from a place like CMO (see Computer Shopper). See ``Boca PCI/VLB'' for info on these cards. See ``AMD PCnet-32'' for info on the 32 bit versions of the LANCE / PCnet-ISA chip. In the future, the DEC 21040 PCI chip will probably be supported as well, but don't hold your breath. 8.7.3. FDDI Is there FDDI support for Linux? Donald writes: `No, there is no Linux driver for any FDDI boards. I come from a place with supercomputers, so an external observer might think FDDI would be high on my list. But FDDI never delivered end-to- end throughput that would justify its cost, and it seems to be a nearly abandoned technology now that 100base{X,Anynet} seems imminent. (And yes, I know you can now get FDDI boards for <$1K. That seems to be a last-ditch effort to get some return on the development investment. Where is the next generation of FDDI going to come from?)' 8.7.4. Linking 10BaseT without a Hub Can I link 10BaseT (RJ45) based systems together without a hub? You can link 2 machines easily, but no more than that, without extra devices/gizmos. See ``Twisted Pair'' -- it explains how to do it. And no, you can't hack together a hub just by crossing a few wires and stuff. It's pretty much impossible to do the collision signal right without duplicating a hub. 8.7.5. SIOCSFFLAGS: Try again I get `SIOCSFFLAGS: Try again' when I run `ifconfig' -- Huh? Some other device has taken the IRQ that your ethercard is trying to use, and so the ethercard can't use the IRQ. You don't necessairly need to reboot to resolve this, as some devices only grab the IRQs when they need them and then release them when they are done. Examples are some sound cards, serial ports, floppy disk driver, etc. You can type cat /proc/interrupts to see which interrupts are presently in use. Those marked with a `+' are ones that are not taken on a permanent basis. Most of the Linux ethercard drivers only grab the IRQ when they are opened for use via `ifconfig'. If you can get the other device to `let go' of the required IRQ line, then you should be able to `Try again' with ifconfig. 8.7.6. Link UNSPEC and HW-addr of 00-00-00-00-00-00 When I run ifconfig with no arguments, it reports that LINK is UNSPEC (instead of 10Mbs Ethernet) and it also says that my hardware address is all zeros. This is because people are running a newer version of the `ifconfig' program than their kernel version. This new version of ifconfig is not able to report these properties when used in conjunction with an older kernel. You can either upgrade your kernel, `downgrade' ifconfig, or simply ignore it. The kernel knows your hardware address, so it really doesn't matter if ifconfig can't read it. 8.7.7. Huge Number of RX and TX Errors When I run ifconfig with no arguments, it reports that I have a huge error count in both rec'd and transmitted packets. It all seems to work ok -- What is wrong? Look again. It says RX packets big number PAUSE errors 0 PAUSE dropped 0 PAUSE overrun 0. And the same for the TX column. Hence the big numbers you are seeing are the total number of packets that your machine has rec'd and transmitted. If you still find it confusing, try typing cat /proc/net/dev instead. 8.7.8. Entries in /dev/ for Ethercards I have /dev/eth0 as a link to /dev/xxx. Is this right? Contrary to what you have heard, the files in /dev/* are not used. You can delete any /dev/wd0, /dev/ne0 and similar entries. 8.7.9. Linux and ``trailers'' Should I disable trailers when I `ifconfig' my ethercard? You can't disable trailers, and you shouldn't want to. `Trailers' are a hack to avoid data copying in the networking layers. The idea was to use a trivial fixed-size header of size `H', put the variable-size header info at the end of the packet, and allocate all packets packets `H' bytes before the start of a page. While it was a good idea, it turned out to not work well in practice. If someone suggests the use of `-trailers', note that it is the equivalent of sacrificial goats blood. It won't do anything to solve the problem, but if problem fixes itself then someone can claim deep magical knowledge. 9. Miscellaneous. Any other associated stuff that didn't fit in anywhere else gets dumped here. It may not be relevant, and it may not be of general interest but it is here anyway. 9.1. Passing Ethernet Arguments to the Kernel via LILO Here are two generic kernel commands that would be typed after the name of your configuration in your lilo.conf file (usually `linux') For exmaple, if the command was `blah' and it expected 3 arguments (say 123, 456, and 789) then you would use: LILO: linux blah=123,456,789 9.1.1. The ether command In its most generic form, it looks something like this: ether=IRQ,BASE_ADDR,PARAM_1,PARAM_2,NAME All arguments are optional. The first non-numeric argument is taken as the NAME. IRQ: Obvious. An IRQ value of `0' (usually the default) means to autoIRQ. It's a historical accident that the IRQ setting is first rather than the base_addr -- this will be fixed whenever something else changes. BASE_ADDR: Also obvious. A value of `0' (usually the default) means to probe a card-type-specific address list for an ethercard. PARAM_1: It was orginally used as an override value for the memory start for a shared-memory ethercard, like the WD80*3. Some drivers use the low four bits of this value to set the debug message level. 0 -- default, 1-7 -- level 1..7, (7 is maximum verbosity) 8 -- level 0 (no messages). PARAM_2: The 3c503 driver uses this select between the internal and external transceivers. 0 -- default/internal, 1 -- AUI external. NAME: Selects the network device the values refer to. The standard kernel uses the names `eth0', `eth1', `eth2' and `eth3' for bus- attached ethercards, and `atp0/dl0' for parallel port `pocket' ethernet adaptors. The default setting is for a single ethercard to be probed for as `eth0'. Multiple cards can only be enabled by explicitly setting up their base address using these LILO parameters. The 1.0 kernel has LANCE-based ethercards as a special case. LILO arguments are ignored, and LANCE cards are always assigned `eth<n>' names starting at `eth0'. Additional non-LANCE ethercards must be explicitly assigned to `eth<n+1>', and the usual `eth0' probe disabled with something like `ether=0,-1,eth0'. ( Yes, this is bug. ) 9.1.2. The reserve command This next lilo command is used just like `ether=' above, ie. it is appended to the name of the boot select specified in lilo.conf reserve=IO-base,extent{,IO-base,extent...} In some machines it may be necessary to prevent device drivers from checking for devices (auto-probing) in a specific region. This may be because of poorly designed hardware that causes the boot to freeze (such as some ethercards), hardware that is mistakenly identified, hardware whose state is changed by an earlier probe, or merely hardware you don't want the kernel to initialize. The reserve boot-time argument addresses this problem by specifying an I/O port region that shouldn't be probed. That region is reserved in the kernel's port registration table as if a device has already been found in that region. Note that this mechanism shouldn't be necessary on most machine, only when there is a problem or special case. The I/O ports in the specified region are protected against device probes. This was put in to be used when some driver was hanging on e.g. a NE2000, or misidentifying some other device as its own. A correct device driver shouldn't probe a reserved region, unless another boot argument explicitly specifies that it do so. This implies that reserve will most often be used with some other boot argument. Hence if you specify a reserve region to protect a specific device, you must generally specify an explicit probe for that device. Most drivers ignore the port registration table if they are given an explicit address. For example, the boot line LILO: linux reserve=0x300,32 ether=0,0x300,eth0 keeps all device drivers except the ethercard drivers from probing 0x300-0x31f. As usual with boot-time specifiers there is an 11 parameter limit, thus you can only specify 5 reserved regions per reserve keyword. Multiple reserve specifiers will work if you have an usually complicated request. 9.2. Contributors Other people who have contributed (directly or indirectly) to the Ethernet-Howto are, in alphabetical order: Peter Bauer <pbauer@rnivh.rni.sub.org> Ross Biro <bir7@leland.Stanford.EDU> Alan Cox <iiitac@pyr.swan.ac.uk> David C. Davies <davies@wanton.enet.dec.com> Bjorn Ekwall <bj0rn@blox.se> David Hinds <dhinds@allegro.stanford.edu> Michael Hipp <mhipp@student.uni-tuebingen.de> Mike Jagdis <jaggy@purplet.demon.co.uk> Duke Kamstra <kamstra@ccmail.west.smc.com> Russell Nelson <nelson@crynwr.com> Cameron Spitzer <camerons@NAD.3Com.com> Dave Roberts <david.roberts@amd.com> Glenn Talbott <gt@hprnd.rose.hp.com> Many thanks to the above people, and all the other unmentioned testers out there. 9.3. Closing If you have found any glaring typos, or outdated info in this document, please let one of us know. It's getting big, and it is easy to overlook stuff. Thanks, Paul Gortmaker, Paul.Gortmaker@anu.edu.au Donald J. Becker, becker@cesdis.gsfc.nasa.gov