Posted by under DECnet,HECnet,Linux,Networking on July 14 2013, 0 comments

Finally I’ve got around to tinkering with DECnet for Linux. DECnet has been in the Linux Kernel for a long time, but very few people use it.

So, my mission was to get one of my Linux machines to talk nicely to HECnet. Specifically, my Ubuntu 10.4 machine which I use as the server for my LAN, which for no logical reason is called servalan.

The first thing I had to do was move the HECnet bridging software off servalan and on to another machine that runs 24/7. The logical choice, in my case, was the Raspberry-Pi running RaspBMC that is taped to the back of my television.

So, with the bridging software moved, I came across a problem. DECnet names are 6 characters, and servalan is 8. As I use names of Sci-Fi characters and ideas for my various Unix machines, I picked DAVROS, purely because Servalan was the Big Bad of Blake’s Seven and Davros was a Big Bad on Doctor Who. (My Windows machines are named after the Istari from Tolkien’s works).

So, after agreeing that I would use the name DAVROS and number 1.252, and noting that DECnet was still included in the kernel that Ubuntu uses, the first step was to convice the network interface that it was using the appropriate DECnet hardware address (which for 1.252 would be AA-00-04-00-FC-04).

So, edit /etc/network/interfaces (as root) to have the following entry:

iface eth2 inet static
hwaddress ether AA:00:04:00:FC:04

(obviously those are my ip addresses and i’m using eth2 for some reason).

Next, my /etc/decnet.conf files looks like this:

#               DECnet hosts file
#Node           Node            Name            Node    Line    Line
#Type           Address         Tag             Name    Tag     Device
#-----          -------         -----           -----   -----   ------
executor        1.252           name            davros  line    eth2
node            1.250           name            tardis
node            1.251           name            sidrat

(TARDIS is an existing Simulated VAX, and SIDRAT will be a node clustered with TARDIS sometime soon)

My /etc/decnet.proxy looks like this:

 #     /etc/decnet.proxy
 # DECnet proxy database.
 # The format of this file is (one entry per line)
 # node::remoteuser localuser
 # ...
 # ^tramp$::^test$ chrissie # Explicitly convert 'test' on tramp to chrissie
 # ^zaphod$::.*   none     # Disable proxies from zaphod
 .*::.* */DEFAULT
 # associate all remote users with a
 # similarly named user on the local VMS machine

 #                              #   a user called 'none')
 # .*::.* decnet            # Like a default     DECnet account
 # .*::.* *                 #     Equivalent to VMS *::* * proxy (make this last
 #                              #   if you use it)

And my /etc/dnetd.conf looks like this:

# /etc/dnetd.conf
 # Define DECnet objects
 # Fields
 # name:    object name (or * for any named object, number must be     0)
 # number:  object number (or 0 for a named object)
 # options: auth[,auto accept]:
 #  auth:        Whether to authenticate users: Y     or N
 #  auto accept: Should we accept incoming connections
 #                This is needed for     non-decnet daemons
 #                (not calling     dnet_accept)
 # user:    If auth is N then use this user
 # daemon:  program to run or 'internal'
 # name         number    options  user           daemon
 FAL            17            Y,N      fal       fal
 MIRROR         25        Y,N          root     internal
 MAIL           27            N,N      vmsmail    vmsmaild
 CTERM          42            N,N      root       ctermd
 DTERM          23            N,N      root       rmtermd
 NML            19            N,N      nobody     dnetnml
 *              *            Y,R      none       internal

To install the DECnet tools:

# apt-get install dnet-progs

This will give you a whole load of DECnet tools. Some work, some crash spectacularly.

Getting the nodelist from HECnet and putting it into the /etc/decnet.conf file is a pain in the arse to do manually.

First copy is across (using the address 1.13:: as it won’t understant mim:: yet):

# dncopy 1.13::nodenames.dat nodenames.dat

Next you’ll need this badly written bit of C that I bodged up and call mkhecnodes.c:

#include <stdio.h>
#include <string.h>

int main(void)
char line[128];
char *nodenum, *nodename;
int i;
while (gets(line)!=NULL)
if (line[0] != ‘ ‘)
nodenum = strtok (line, ” \n”);
nodename = strtok (NULL, ” \n”);
for(i = 0; nodename[i]; i++)
nodename[i] = tolower(nodename[i]);

Compile it up and run it, giving it the node list as input and directing the output to the end of /etc/decnet.conf:

# gcc -o mkhecnodes mkhecnodes.c
# ./mkhecnodes < nodenames.dat >> /etc/decnet.conf

You might want to go through it and delete your duplicate node info, but I didn’t bother and it works fine. If you want your node names in upper case, remove the for loop.