OpenVMS Hobbyist Program



#!/bin/zsh

## A script to set up a bridge and TUNTAP interfaces for use with

## SIMH simulator. Taps 0-4 (5 total) will be set up, and

## master set to the bridge. The bridge lladdr will be set to 

## DECNET equal of node 1.1 for use with DECNET.

##

## Assumes: There is no br0 created currently. Iproute2 installed. $PATH

## set to sane value. Root user able to make devices running script.

## Kernel will load bridge module on its own, if needed.

##



## [Sanity check, to make sure there's not already a bridge.] ----------



# Color codes for fancy output.

RED='\033[0;31m'

GREEN='\033[0;32m'

BLUE='\033[0;34m'

NC='\033[0m'



if $(ip link show | grep -q br0); then

printf "${RED}Not making another br0, one already exists.${NC}\\n"

exit 1

fi





## [Link creation/setup section] ----------------------------------------

# The ip4 address you want the bridge to have. We will place

# hosts on 192.168.c.d.

bridge_addr="192.168.20.1"



# A function to make a TUNTAP device and assign it to the br0 interface

function make_set_tuntap() {

printf "${BLUE}Adding TUNTAP %s to bridge.${NC}\\n" "${1}"

# Create the device

ip -c tuntap add dev tap${1} mode tap

# Stuff it into the bridge

ip -c link set dev tap${1} master br0

# Set it up. Note, it will still show "down" until used

ip -c link set tap${1} up

}



# First, make the bridge, then turn on spanning tree protocol,

# set the lladdr for DECNET node 1.1. This is in case you want

# to (try to - code broke between 3.x-4.x kernels) use Linux 

# DECENT. Node 1.1 can be the Linux executor.

printf "${GREEN}Making the bridge, br0.${NC} \\n"

ip -c link add name br0 type bridge

ip -c link set br0 type bridge stp_state 1

ip -c link set dev br0 address AA:00:04:00:01:04

ip -c link set br0 up

ip -c addr add ${bridge_addr}/24 broadcast + dev br0



# Error out if something went wrong and no br0. Exit script.

$(ip link show | grep -q br0) || {

printf "${RED}Bridge not created. Cannot continue.${NC}\\n"

exit 1

}



# Make and add TUNTAPs to the brige. You can change this number for 

# more (or less) devices. Ex: seq 0 7 for six taps.

printf "${GREEN}Setting up the TUNTAPs now...${NC} \\n"

for taps in $( seq 0 4 ); do

make_set_tuntap ${taps}

done



# Finished. Show links/addresses.

ip -c addr show

printf "\\n${GREEN}Done.${NC}\\n"





## [SIMH .ini file configuration tips] ------------------------------------

# SIMH .ini file part for a microvax3900 might go like so, attached to

# tap3, node 1.13.

#

# SET XQ MAC=AA:00:04:00:0D:04

# SET XQ TYPE=DELQA

# ATT XQ tap:tap3



# Decnet MAC addresses are tied to node address.

# AA:00:04:00:01:04 = 1.1

# AA:00:04:00:0A:04 = 1.10

# AA:00:04:00:0B:04 = 1.11

# AA:00:04:00:0C:04 = 1.12

# AA:00:04:00:0D:04 = 1.13

# AA:00:04:00:0E:04 = 1.14





## [VMS Routing tips] ------------------------------------------------------

# In VMS, set 192.168.20.1 (the bridge ip4 address) as static gateway. Set

# static ip4 address for VMS node. On Linux host, forward traffic for interfaces:

# net.ipv4.conf.all.forwarding = 1

# Masquerade all private address space traffic:

# iptables -t nat -A POSTROUTING -m comment --comment "Masquerade all rfc1918 addresses" -s 192.168.0.0/16 -j MASQUERADE

# In VMS, add name servers, and assign host addresses. Match tcpip host name and node name for

# simplicity (6 character limit to DECNET node names).

# TCPIP> SET NAME_SERVICE /SERVER=208.67.222.222 /enable /system

# TCPIP> set host teostr /address=192.168.20.2 /alias=teostr.lan

# TCPIP> set host lunast /address=192.168.20.3 /alias=lunast.lan



##EOF