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1 | Linux DECnet Networking Layer Information |
2 | =========================================== | |
3 | ||
4 | 1) Other documentation.... | |
5 | ||
6 | o Project Home Pages | |
0ea6e611 | 7 | http://www.chygwyn.com/ - Kernel info |
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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 | ||
2d27a966 | 63 | decnet.addr=1,2 |
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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 | |
670e9f34 | 85 | address to use. The address can be set by ifconfig either before or |
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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 ? | |
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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> | |
232 |