Based on kernel version 4.15. Page generated on 2018-01-29 10:00 EST.
1 Linux DECnet Networking Layer Information 2 =========================================== 3 4 1) Other documentation.... 5 6 o Project Home Pages 7 http://www.chygwyn.com/ - Kernel info 8 http://linux-decnet.sourceforge.net/ - Userland tools 9 http://www.sourceforge.net/projects/linux-decnet/ - Status page 10 11 2) Configuring the kernel 12 13 Be sure to turn on the following options: 14 15 CONFIG_DECNET (obviously) 16 CONFIG_PROC_FS (to see what's going on) 17 CONFIG_SYSCTL (for easy configuration) 18 19 if you want to try out router support (not properly debugged yet) 20 you'll need the following options as well... 21 22 CONFIG_DECNET_ROUTER (to be able to add/delete routes) 23 CONFIG_NETFILTER (will be required for the DECnet routing daemon) 24 25 CONFIG_DECNET_ROUTE_FWMARK is optional 26 27 Don't turn on SIOCGIFCONF support for DECnet unless you are really sure 28 that you need it, in general you won't and it can cause ifconfig to 29 malfunction. 30 31 Run time configuration has changed slightly from the 2.4 system. If you 32 want to configure an endnode, then the simplified procedure is as follows: 33 34 o Set the MAC address on your ethernet card before starting _any_ other 35 network protocols. 36 37 As soon as your network card is brought into the UP state, DECnet should 38 start working. If you need something more complicated or are unsure how 39 to set the MAC address, see the next section. Also all configurations which 40 worked with 2.4 will work under 2.5 with no change. 41 42 3) Command line options 43 44 You can set a DECnet address on the kernel command line for compatibility 45 with the 2.4 configuration procedure, but in general it's not needed any more. 46 If you do st a DECnet address on the command line, it has only one purpose 47 which is that its added to the addresses on the loopback device. 48 49 With 2.4 kernels, DECnet would only recognise addresses as local if they 50 were added to the loopback device. In 2.5, any local interface address 51 can be used to loop back to the local machine. Of course this does not 52 prevent you adding further addresses to the loopback device if you 53 want to. 54 55 N.B. Since the address list of an interface determines the addresses for 56 which "hello" messages are sent, if you don't set an address on the loopback 57 interface then you won't see any entries in /proc/net/neigh for the local 58 host until such time as you start a connection. This doesn't affect the 59 operation of the local communications in any other way though. 60 61 The kernel command line takes options looking like the following: 62 63 decnet.addr=1,2 64 65 the two numbers are the node address 1,2 = 1.2 For 2.2.xx kernels 66 and early 2.3.xx kernels, you must use a comma when specifying the 67 DECnet address like this. For more recent 2.3.xx kernels, you may 68 use almost any character except space, although a `.` would be the most 69 obvious choice :-) 70 71 There used to be a third number specifying the node type. This option 72 has gone away in favour of a per interface node type. This is now set 73 using /proc/sys/net/decnet/conf/<dev>/forwarding. This file can be 74 set with a single digit, 0=EndNode, 1=L1 Router and 2=L2 Router. 75 76 There are also equivalent options for modules. The node address can 77 also be set through the /proc/sys/net/decnet/ files, as can other system 78 parameters. 79 80 Currently the only supported devices are ethernet and ip_gre. The 81 ethernet address of your ethernet card has to be set according to the DECnet 82 address of the node in order for it to be autoconfigured (and then appear in 83 /proc/net/decnet_dev). There is a utility available at the above 84 FTP sites called dn2ethaddr which can compute the correct ethernet 85 address to use. The address can be set by ifconfig either before or 86 at the time the device is brought up. If you are using RedHat you can 87 add the line: 88 89 MACADDR=AA:00:04:00:03:04 90 91 or something similar, to /etc/sysconfig/network-scripts/ifcfg-eth0 or 92 wherever your network card's configuration lives. Setting the MAC address 93 of your ethernet card to an address starting with "hi-ord" will cause a 94 DECnet address which matches to be added to the interface (which you can 95 verify with iproute2). 96 97 The default device for routing can be set through the /proc filesystem 98 by setting /proc/sys/net/decnet/default_device to the 99 device you want DECnet to route packets out of when no specific route 100 is available. Usually this will be eth0, for example: 101 102 echo -n "eth0" >/proc/sys/net/decnet/default_device 103 104 If you don't set the default device, then it will default to the first 105 ethernet card which has been autoconfigured as described above. You can 106 confirm that by looking in the default_device file of course. 107 108 There is a list of what the other files under /proc/sys/net/decnet/ do 109 on the kernel patch web site (shown above). 110 111 4) Run time kernel configuration 112 113 This is either done through the sysctl/proc interface (see the kernel web 114 pages for details on what the various options do) or through the iproute2 115 package in the same way as IPv4/6 configuration is performed. 116 117 Documentation for iproute2 is included with the package, although there is 118 as yet no specific section on DECnet, most of the features apply to both 119 IP and DECnet, albeit with DECnet addresses instead of IP addresses and 120 a reduced functionality. 121 122 If you want to configure a DECnet router you'll need the iproute2 package 123 since its the _only_ way to add and delete routes currently. Eventually 124 there will be a routing daemon to send and receive routing messages for 125 each interface and update the kernel routing tables accordingly. The 126 routing daemon will use netfilter to listen to routing packets, and 127 rtnetlink to update the kernels routing tables. 128 129 The DECnet raw socket layer has been removed since it was there purely 130 for use by the routing daemon which will now use netfilter (a much cleaner 131 and more generic solution) instead. 132 133 5) How can I tell if its working ? 134 135 Here is a quick guide of what to look for in order to know if your DECnet 136 kernel subsystem is working. 137 138 - Is the node address set (see /proc/sys/net/decnet/node_address) 139 - Is the node of the correct type 140 (see /proc/sys/net/decnet/conf/<dev>/forwarding) 141 - Is the Ethernet MAC address of each Ethernet card set to match 142 the DECnet address. If in doubt use the dn2ethaddr utility available 143 at the ftp archive. 144 - If the previous two steps are satisfied, and the Ethernet card is up, 145 you should find that it is listed in /proc/net/decnet_dev and also 146 that it appears as a directory in /proc/sys/net/decnet/conf/. The 147 loopback device (lo) should also appear and is required to communicate 148 within a node. 149 - If you have any DECnet routers on your network, they should appear 150 in /proc/net/decnet_neigh, otherwise this file will only contain the 151 entry for the node itself (if it doesn't check to see if lo is up). 152 - If you want to send to any node which is not listed in the 153 /proc/net/decnet_neigh file, you'll need to set the default device 154 to point to an Ethernet card with connection to a router. This is 155 again done with the /proc/sys/net/decnet/default_device file. 156 - Try starting a simple server and client, like the dnping/dnmirror 157 over the loopback interface. With luck they should communicate. 158 For this step and those after, you'll need the DECnet library 159 which can be obtained from the above ftp sites as well as the 160 actual utilities themselves. 161 - If this seems to work, then try talking to a node on your local 162 network, and see if you can obtain the same results. 163 - At this point you are on your own... :-) 164 165 6) How to send a bug report 166 167 If you've found a bug and want to report it, then there are several things 168 you can do to help me work out exactly what it is that is wrong. Useful 169 information (_most_ of which _is_ _essential_) includes: 170 171 - What kernel version are you running ? 172 - What version of the patch are you running ? 173 - How far though the above set of tests can you get ? 174 - What is in the /proc/decnet* files and /proc/sys/net/decnet/* files ? 175 - Which services are you running ? 176 - Which client caused the problem ? 177 - How much data was being transferred ? 178 - Was the network congested ? 179 - How can the problem be reproduced ? 180 - Can you use tcpdump to get a trace ? (N.B. Most (all?) versions of 181 tcpdump don't understand how to dump DECnet properly, so including 182 the hex listing of the packet contents is _essential_, usually the -x flag. 183 You may also need to increase the length grabbed with the -s flag. The 184 -e flag also provides very useful information (ethernet MAC addresses)) 185 186 7) MAC FAQ 187 188 A quick FAQ on ethernet MAC addresses to explain how Linux and DECnet 189 interact and how to get the best performance from your hardware. 190 191 Ethernet cards are designed to normally only pass received network frames 192 to a host computer when they are addressed to it, or to the broadcast address. 193 194 Linux has an interface which allows the setting of extra addresses for 195 an ethernet card to listen to. If the ethernet card supports it, the 196 filtering operation will be done in hardware, if not the extra unwanted packets 197 received will be discarded by the host computer. In the latter case, 198 significant processor time and bus bandwidth can be used up on a busy 199 network (see the NAPI documentation for a longer explanation of these 200 effects). 201 202 DECnet makes use of this interface to allow running DECnet on an ethernet 203 card which has already been configured using TCP/IP (presumably using the 204 built in MAC address of the card, as usual) and/or to allow multiple DECnet 205 addresses on each physical interface. If you do this, be aware that if your 206 ethernet card doesn't support perfect hashing in its MAC address filter 207 then your computer will be doing more work than required. Some cards 208 will simply set themselves into promiscuous mode in order to receive 209 packets from the DECnet specified addresses. So if you have one of these 210 cards its better to set the MAC address of the card as described above 211 to gain the best efficiency. Better still is to use a card which supports 212 NAPI as well. 213 214 215 8) Mailing list 216 217 If you are keen to get involved in development, or want to ask questions 218 about configuration, or even just report bugs, then there is a mailing 219 list that you can join, details are at: 220 221 http://sourceforge.net/mail/?group_id=4993 222 223 9) Legal Info 224 225 The Linux DECnet project team have placed their code under the GPL. The 226 software is provided "as is" and without warranty express or implied. 227 DECnet is a trademark of Compaq. This software is not a product of 228 Compaq. We acknowledge the help of people at Compaq in providing extra 229 documentation above and beyond what was previously publicly available. 230 231 Steve Whitehouse <SteveW@ACM.org>