Plug-and-Play USB Networking

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Contents

Introduction

I provide here an example setup which are more complicated than your setup probably will be.

Use case

I have 1 laptop and 2 freerunners. Whenever I plug my freerunner, I want my laptop recognize which freerunner was plugged in and act accordingly. Also automagically set up the networking for me.

Prerequisites

You need a linux/unix computer with working NetworkManager setup. I have successfully use this method more than a month now, with Ubuntu 9.04 (jaunty), I will test it also on Ubuntu 8.10 (intrepid), and report back here.(I tested, and it does not work, however 9.10 works great)

Tested distributions

Distribution NetworkManager version Known to work
Ubuntu 8.10 (Intrepid) ? NO
Ubuntu 9.04 (Jaunty) 0.7.1~rc4-0ubuntu1 YES
Ubuntu 9.10 (Karmic) ? YES


The NetworkManager on jaunty is:

ii  network-manager                            0.7.1~rc4-0ubuntu1 
ii  network-manager-gnome                      0.7.1~rc4.1-0ubuntu1

File/directory structure

/etc/NetworkManager/system-connections/freerunner_bob   (owner: root, rights: 600)
/etc/NetworkManager/system-connections/freerunner_bobek (owner: root, rights: 600)
/etc/NetworkManager/dispatcher.d/10myiptables           (owner: root, rights: 755)

File contents

/etc/NetworkManager/system-connections/freerunner_bob:

[connection]
id=Bob's moko
uuid=27afa607-ee36-43f0-b8c3-9d245cdc4bb4
type=802-3-ethernet
autoconnect=true
timestamp=0
[ipv4]
method=manual
never-default=true
address1=192.168.0.200;24
[802-3-ethernet]
mac-address=00:1f:11:01:5d:13  

/etc/NetworkManager/system-connections/freerunner_bobek:

[connection]
id=Bobek's moko
uuid=27afa607-ee36-43f0-b8c3-9d245cdc4bb3
type=802-3-ethernet
autoconnect=true
timestamp=0
[ipv4]
method=manual
never-default=true
address1=192.168.0.200;24
[802-3-ethernet]
mac-address=00:1f:11:01:6e:12

/etc/NetworkManager/dispatcher.d/10myiptables:

#!/bin/sh -e
# Script to dispatch NetworkManager events
#
# Runs ifupdown scripts when NetworkManager fiddles with interfaces.

# Bobek's freerunner
export MYUUID1="27afa607-ee36-43f0-b8c3-9d245cdc4bb3"

# Bob's freerunner
export MYUUID2="27afa607-ee36-43f0-b8c3-9d245cdc4bb4"

# The computer's username
export USERNAME="lolza"

if [ -z "$1" ]; then
    echo "$0: called with no interface" 1>&2
    exit 1;
fi

# Fake ifupdown environment
export IFACE="$1"
export LOGICAL="$1"
export ADDRFAM="NetworkManager"
export METHOD="NetworkManager"
export VERBOSITY="0"

# Run the right scripts
case "$2" in
    up)
	export MODE="start"
	export PHASE="up"

	if [ -f /sys/class/net/$IFACE/address ] ; then
		tmpfile=`mktemp -t`
		echo $CONNECTION_UUID > $tmpfile
		if [ "X${CONNECTION_UUID}" = "X${MYUUID1}" ] ; then
			echo "Bobek's Freerunner connected..." >> $tmpfile
			date >> $tmpfile
			iptables -A POSTROUTING -t nat -j MASQUERADE -s 192.168.0.0/24
			iptables -P FORWARD ACCEPT
			sysctl -w net.ipv4.ip_forward=1
			sudo -u ${USERNAME} ssh-keygen -R 192.168.0.202
		else
			if [ "X${CONNECTION_UUID}" = "X${MYUUID2}" ] ; then
				echo "Bob's Freerunner connected..." >> $tmpfile
				date >> $tmpfile
				iptables -A POSTROUTING -t nat -j MASQUERADE -s 192.168.0.0/24
				iptables -P FORWARD ACCEPT
				sysctl -w net.ipv4.ip_forward=1
				sudo -u ${USERNAME} ssh-keygen -R 192.168.0.202
			fi
		fi
	fi
	;;
    down)
	export MODE="stop"
	export PHASE="down"

	tmpfile=`mktemp -t`
	echo "down called..." >> $tmpfile
	tmpfile=`mktemp -t`
	echo $CONNECTION_UUID > $tmpfile
	if [ "X${CONNECTION_UUID}" = "X${MYUUID1}" ] ; then
		echo "Bobek's Freerunner disconnected..." >> $tmpfile
		iptables -D POSTROUTING -t nat -j MASQUERADE -s 192.168.0.0/24
		iptables -P FORWARD ACCEPT
		sysctl -w net.ipv4.ip_forward=0
	else
		if [ "X${CONNECTION_UUID}" = "X${MYUUID2}" ] ; then
			echo "Bob's Freerunner disconnected..." >> $tmpfile
			iptables -D POSTROUTING -t nat -j MASQUERADE -s 192.168.0.0/24
			iptables -P FORWARD ACCEPT
			sysctl -w net.ipv4.ip_forward=0
		fi
	fi
	;;
    *)
	echo "$0: called with unknown action \`$2'" 1>&2
	exit 1
	;;
esac
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