1.. SPDX-License-Identifier: GPL-2.0 2 3========================================= 4Linux DECnet Networking Layer Information 5========================================= 6 71. Other documentation.... 8========================== 9 10 - Project Home Pages 11 - http://www.chygwyn.com/ - Kernel info 12 - http://linux-decnet.sourceforge.net/ - Userland tools 13 - http://www.sourceforge.net/projects/linux-decnet/ - Status page 14 152. Configuring the kernel 16========================= 17 18Be sure to turn on the following options: 19 20 - CONFIG_DECNET (obviously) 21 - CONFIG_PROC_FS (to see what's going on) 22 - CONFIG_SYSCTL (for easy configuration) 23 24if you want to try out router support (not properly debugged yet) 25you'll need the following options as well... 26 27 - CONFIG_DECNET_ROUTER (to be able to add/delete routes) 28 - CONFIG_NETFILTER (will be required for the DECnet routing daemon) 29 30Don't turn on SIOCGIFCONF support for DECnet unless you are really sure 31that you need it, in general you won't and it can cause ifconfig to 32malfunction. 33 34Run time configuration has changed slightly from the 2.4 system. If you 35want to configure an endnode, then the simplified procedure is as follows: 36 37 - Set the MAC address on your ethernet card before starting _any_ other 38 network protocols. 39 40As soon as your network card is brought into the UP state, DECnet should 41start working. If you need something more complicated or are unsure how 42to set the MAC address, see the next section. Also all configurations which 43worked with 2.4 will work under 2.5 with no change. 44 453. Command line options 46======================= 47 48You can set a DECnet address on the kernel command line for compatibility 49with the 2.4 configuration procedure, but in general it's not needed any more. 50If you do st a DECnet address on the command line, it has only one purpose 51which is that its added to the addresses on the loopback device. 52 53With 2.4 kernels, DECnet would only recognise addresses as local if they 54were added to the loopback device. In 2.5, any local interface address 55can be used to loop back to the local machine. Of course this does not 56prevent you adding further addresses to the loopback device if you 57want to. 58 59N.B. Since the address list of an interface determines the addresses for 60which "hello" messages are sent, if you don't set an address on the loopback 61interface then you won't see any entries in /proc/net/neigh for the local 62host until such time as you start a connection. This doesn't affect the 63operation of the local communications in any other way though. 64 65The kernel command line takes options looking like the following:: 66 67 decnet.addr=1,2 68 69the two numbers are the node address 1,2 = 1.2 For 2.2.xx kernels 70and early 2.3.xx kernels, you must use a comma when specifying the 71DECnet address like this. For more recent 2.3.xx kernels, you may 72use almost any character except space, although a `.` would be the most 73obvious choice :-) 74 75There used to be a third number specifying the node type. This option 76has gone away in favour of a per interface node type. This is now set 77using /proc/sys/net/decnet/conf/<dev>/forwarding. This file can be 78set with a single digit, 0=EndNode, 1=L1 Router and 2=L2 Router. 79 80There are also equivalent options for modules. The node address can 81also be set through the /proc/sys/net/decnet/ files, as can other system 82parameters. 83 84Currently the only supported devices are ethernet and ip_gre. The 85ethernet address of your ethernet card has to be set according to the DECnet 86address of the node in order for it to be autoconfigured (and then appear in 87/proc/net/decnet_dev). There is a utility available at the above 88FTP sites called dn2ethaddr which can compute the correct ethernet 89address to use. The address can be set by ifconfig either before or 90at the time the device is brought up. If you are using RedHat you can 91add the line:: 92 93 MACADDR=AA:00:04:00:03:04 94 95or something similar, to /etc/sysconfig/network-scripts/ifcfg-eth0 or 96wherever your network card's configuration lives. Setting the MAC address 97of your ethernet card to an address starting with "hi-ord" will cause a 98DECnet address which matches to be added to the interface (which you can 99verify with iproute2). 100 101The default device for routing can be set through the /proc filesystem 102by setting /proc/sys/net/decnet/default_device to the 103device you want DECnet to route packets out of when no specific route 104is available. Usually this will be eth0, for example:: 105 106 echo -n "eth0" >/proc/sys/net/decnet/default_device 107 108If you don't set the default device, then it will default to the first 109ethernet card which has been autoconfigured as described above. You can 110confirm that by looking in the default_device file of course. 111 112There is a list of what the other files under /proc/sys/net/decnet/ do 113on the kernel patch web site (shown above). 114 1154. Run time kernel configuration 116================================ 117 118 119This is either done through the sysctl/proc interface (see the kernel web 120pages for details on what the various options do) or through the iproute2 121package in the same way as IPv4/6 configuration is performed. 122 123Documentation for iproute2 is included with the package, although there is 124as yet no specific section on DECnet, most of the features apply to both 125IP and DECnet, albeit with DECnet addresses instead of IP addresses and 126a reduced functionality. 127 128If you want to configure a DECnet router you'll need the iproute2 package 129since its the _only_ way to add and delete routes currently. Eventually 130there will be a routing daemon to send and receive routing messages for 131each interface and update the kernel routing tables accordingly. The 132routing daemon will use netfilter to listen to routing packets, and 133rtnetlink to update the kernels routing tables. 134 135The DECnet raw socket layer has been removed since it was there purely 136for use by the routing daemon which will now use netfilter (a much cleaner 137and more generic solution) instead. 138 1395. How can I tell if its working? 140================================= 141 142Here is a quick guide of what to look for in order to know if your DECnet 143kernel subsystem is working. 144 145 - Is the node address set (see /proc/sys/net/decnet/node_address) 146 - Is the node of the correct type 147 (see /proc/sys/net/decnet/conf/<dev>/forwarding) 148 - Is the Ethernet MAC address of each Ethernet card set to match 149 the DECnet address. If in doubt use the dn2ethaddr utility available 150 at the ftp archive. 151 - If the previous two steps are satisfied, and the Ethernet card is up, 152 you should find that it is listed in /proc/net/decnet_dev and also 153 that it appears as a directory in /proc/sys/net/decnet/conf/. The 154 loopback device (lo) should also appear and is required to communicate 155 within a node. 156 - If you have any DECnet routers on your network, they should appear 157 in /proc/net/decnet_neigh, otherwise this file will only contain the 158 entry for the node itself (if it doesn't check to see if lo is up). 159 - If you want to send to any node which is not listed in the 160 /proc/net/decnet_neigh file, you'll need to set the default device 161 to point to an Ethernet card with connection to a router. This is 162 again done with the /proc/sys/net/decnet/default_device file. 163 - Try starting a simple server and client, like the dnping/dnmirror 164 over the loopback interface. With luck they should communicate. 165 For this step and those after, you'll need the DECnet library 166 which can be obtained from the above ftp sites as well as the 167 actual utilities themselves. 168 - If this seems to work, then try talking to a node on your local 169 network, and see if you can obtain the same results. 170 - At this point you are on your own... :-) 171 1726. How to send a bug report 173=========================== 174 175If you've found a bug and want to report it, then there are several things 176you can do to help me work out exactly what it is that is wrong. Useful 177information (_most_ of which _is_ _essential_) includes: 178 179 - What kernel version are you running ? 180 - What version of the patch are you running ? 181 - How far though the above set of tests can you get ? 182 - What is in the /proc/decnet* files and /proc/sys/net/decnet/* files ? 183 - Which services are you running ? 184 - Which client caused the problem ? 185 - How much data was being transferred ? 186 - Was the network congested ? 187 - How can the problem be reproduced ? 188 - Can you use tcpdump to get a trace ? (N.B. Most (all?) versions of 189 tcpdump don't understand how to dump DECnet properly, so including 190 the hex listing of the packet contents is _essential_, usually the -x flag. 191 You may also need to increase the length grabbed with the -s flag. The 192 -e flag also provides very useful information (ethernet MAC addresses)) 193 1947. MAC FAQ 195========== 196 197A quick FAQ on ethernet MAC addresses to explain how Linux and DECnet 198interact and how to get the best performance from your hardware. 199 200Ethernet cards are designed to normally only pass received network frames 201to a host computer when they are addressed to it, or to the broadcast address. 202 203Linux has an interface which allows the setting of extra addresses for 204an ethernet card to listen to. If the ethernet card supports it, the 205filtering operation will be done in hardware, if not the extra unwanted packets 206received will be discarded by the host computer. In the latter case, 207significant processor time and bus bandwidth can be used up on a busy 208network (see the NAPI documentation for a longer explanation of these 209effects). 210 211DECnet makes use of this interface to allow running DECnet on an ethernet 212card which has already been configured using TCP/IP (presumably using the 213built in MAC address of the card, as usual) and/or to allow multiple DECnet 214addresses on each physical interface. If you do this, be aware that if your 215ethernet card doesn't support perfect hashing in its MAC address filter 216then your computer will be doing more work than required. Some cards 217will simply set themselves into promiscuous mode in order to receive 218packets from the DECnet specified addresses. So if you have one of these 219cards its better to set the MAC address of the card as described above 220to gain the best efficiency. Better still is to use a card which supports 221NAPI as well. 222 223 2248. Mailing list 225=============== 226 227If you are keen to get involved in development, or want to ask questions 228about configuration, or even just report bugs, then there is a mailing 229list that you can join, details are at: 230 231http://sourceforge.net/mail/?group_id=4993 232 2339. Legal Info 234============= 235 236The Linux DECnet project team have placed their code under the GPL. The 237software is provided "as is" and without warranty express or implied. 238DECnet is a trademark of Compaq. This software is not a product of 239Compaq. We acknowledge the help of people at Compaq in providing extra 240documentation above and beyond what was previously publicly available. 241 242Steve Whitehouse <SteveW@ACM.org> 243 244