Establishing a Mesh Portal

It's not entirely automatic quite yet; we'll get a more automatic solution in place soon.

Requirements

• http://www.cozybit.com/projects/mpp-utils/mpp-utils.tar.gz
• A USB ethernet adapter
• One OLPC laptop (XO)

What to do

• Plug the USB ethernet adapter into the XO

• Un-gzip and un-tar that somewhere on your mesh portal machine

• in masquerade.sh from the mpp-utils, change EXTIF to your USB wired interface. If the USB ethernet adapter is plugged in at at boot, this will usually be "eth0".

• In masquerade.sh, make the following changes (shown here in patch-style form):

    # This line results in iptables: Unknown error 4294967295
-    #$IPTABLES -A FORWARD -i $EXTIF -o $INTIF -m state --state ESTABLISHED,RELATED -j ACCEPT
+    $IPTABLES -A FORWARD -i $EXTIF -o $INTIF -m state --state ESTABLISHED,RELATED -j ACCEPT
    $IPTABLES -A FORWARD -i $EXTIF -o $INTIF  -j ACCEPT
    $IPTABLES -A FORWARD -i $INTIF -o $EXTIF -j ACCEPT
-    $IPTABLES -A FORWARD -j LOG
+    #$IPTABLES -A FORWARD -j LOG

• Stop NetworkManager and the 'network' scripts

chkconfig --level 2345 NetworkManager stop
chkconfig --level 2345 network stop
chkconfig --level 2345 dhcdbd stop

• Set your init level to '3'; stopping Sugar and X from starting again.

nano /etc/inittab

find the line with:

id:5:initdefault:

and change the '5' to a '3' so it looks like this instead:

id:3:initdefault:

• reboot

• Create an ifcfg file for your USB wired interface. For example, if your wired interface is eth0, create /etc/sysconfig/network-scripts/ifcfg-eth0, which should contain:

DEVICE=eth0
ONBOOT=no
BOOTPROTO=dhcp

This file will already exist for 'eth0', but if your USB wired interface is _not_ 'eth0', you need to create this file for whatever interface name your wired USB device is.

• Start the wired interface

ifup eth0

• Install the DHCP daemon

yum -y install dhcp

You may have to try this command twice; yum sometimes runs out of memory doing dependency solving, and terminates before actually installing the RPM.

• Configure DHCP to serve on the mesh interface. Edit /etc/sysconfig/dhcpd so it looks like this:

# Command line options here
DHCPDARGS=msh0

• Set up DHCP to provide leases on the mesh interface. Edit /etc/dhcpd.conf to look like the following. For the "option domain-name-servers", use the domain name servers that your USB Ethernet device returned via DHCP, which should be found in /etc/resolv.conf. Don't leave "option domain-name-servers with the "x.x.x.x" values. If you only have one DNS server, omit the second value from at line.

subnet 10.0.0.0 netmask 255.255.255.0 {
  range 10.0.0.5 10.0.0.254;
  default-lease-time 3600;
  max-lease-time 7200;
  option subnet-mask 255.255.255.0;
  option broadcast-address 10.0.0.255;
  option routers 10.0.0.1;
  option domain-name-servers x.x.x.x, x.x.x.x;
}

• Set DHCP to run on startup

chkconfig --level 345 dhcpd on

• Configure the mesh interface

iwconfig msh0 mode ad-hoc channel 11 essid "olpc-mesh"

• Assign the address to the mesh interface

ifconfig msh0 10.0.0.1 up

• run the mpp.py script

python mpp.py

and it should all work

Further Reading

More information is available on these topics:

• Mesh Portal discovery protocol
• How things work in Trial1
• Cozybit's MPP Utils