Introduction

l2mesh is a tinc based virtual switch, implemented as a puppet module.

It creates a new ethernet interface on the machine and connects it to the switch.

Here is how the situation looks like when dealing with physical machines and a hardware switch:

+----------------+                        +---------------+
|                |                        |               |
|          +-----+                        +-----+         |
| MACHINE  | eth0+---------+    +---------+eth0 | MACHINE |
|    A     +-----+         |    |         +-----+   C     |
|                |         |    |         |               |
+----------------+     +---+----+---+     +---------------+
                       |  SWITCH    |
                       +-----+------+
                             |
+----------------+           |
|                |           |
|          +-----+           |
| MACHINE  | eth0+-----------+
|    B     +-----+
|                |
+----------------+

Each of the three machines ( A, B, C ) have a physical ethernet connector which shows as eth0. They are connected with a cable to a SWITCH which transmits the packet coming from MACHINE A to MACHINE B or MACHINE C.

With l2mesh, a new virtual interface ( named L2M below ) is created on each machine and they are all connected by a TINC daemon. Packets go from MACHINE A to MACHINE B or MACHINE C as if they were connected to a physical switch.

+---------+-----+
|         |eth0 |
|         +-----+
| MACHINE | L2M |
|    A    +-----+
|           TINC+---
+--------------++   \-------
               |            \-------   +---------------+
               |                    X--+TINC           |
               |            /-------   +-----+         |
 +-------------+-+   /------           | L2M | MACHINE |
 |           TINC+---                  +-----+    C    |
 |         +-----+                     |eth0 |         |
 | MACHINE | L2M |                     +-----+---------+
 |    B    +-----+
 |         |eth0 |
 +---------+-----+

Here is how it looks on each machine:

$ ip link show eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
   link/ether fa:16:3e:48:ae:6f brd ff:ff:ff:ff:ff:ff

$ ip link show dev L2M
2: L2M: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast
   link/ether 72:75:6e:60:59:f0 brd ff:ff:ff:ff:ff:ff

Usage

l2mesh is a puppet module that should be installed in the puppet master as follows

git clone http://redmine.the.re/git/l2mesh.git /etc/puppet/modules/l2mesh

Here is an example usage that can be included in /etc/puppet/manifests/site.pp

node /MACHINE-A.example.com/, /MACHINE-B.example.com/ {
  include l2mesh::params
  
  l2mesh { 'L2M':
    ip                  => $::ipaddress_eth0,
    port                => 656,
  }
}

On both MACHINE-A and MACHINE-B, it will

• create the L2M ethernet interface
• run the tincd daemon to listen on port 656 and bind it to the $::ipaddress_eth0 IP address

In addition, both machines will try to reach each other:

• tincd on MACHINE-A will try to connect to tincd on MACHINE-B
• tincd on MACHINE-B will try to connect to tincd on MACHINE-A

Adding a new machine to the L2M virtual switch is done by adding the hostname of the machine to the node list. For instance, MACHINE-C.example.com can be added with:

node /MACHINE-A.example.com/, /MACHINE-B.example.com/, /MACHINE-C.example.com/  {
...

l2mesh is not

• l2mesh is not an equivalent to brctl : it is a switch made of tinc daemons running on multiple machines

• l2mesh does not know anything about IP addresses or L3 routing. Here is a puppet snippet that shows how to assign IP addresses to an interface created by l2mesh, using the hostname to figure it out. For instance, bm0001.the.re will have the IP 192.168.100.1, bm0002.the.re will have the IP 192.168.100.2 etc. This is done by creating a tinc-up script that is run by tincd each time the interface is up.

      $private_ip = regsubst($::fqdn, '^bm0+(\d+).*', '192.168.100.\1')
    
      file { '/etc/tinc':
        ensure      => 'directory',
        owner       => root,
        group       => root,
        mode        => '0755',
        before      => L2mesh['L2M'],
      }
    
      file { '/etc/tinc/L2M':
        ensure      => 'directory',
        owner       => root,
        group       => root,
        mode        => '0755',
        require     => File['/etc/tinc'],
      }
    
      file { '/etc/tinc/L2M/tinc-up':
        owner       => root,
        group       => root,
        mode        => '0544',
        content     => "#!/bin/bash                                                                                                                                         
    ifconfig L2M ${private_ip} netmask 255.255.255.0                                                                                                                      
    ",
        require     => File['/etc/tinc/L2M'],
      }
  

Implementation

See the implementation notes at the beginning of the file manifests/init.pp

License

Copyright (C) 2012 eNovance <licensing@enovance.com>

Author: Loic Dachary <loic@dachary.org>

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU Affero General Public License for more details.

You should have received a copy of the GNU Affero General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.

Running tests

GEM_HOME=$HOME/.gem-installed gem install --include-dependencies --no-rdoc --no-ri puppet  puppet-lint rspec-puppet rspec-expectations mocha puppetlabs_spec_helper rake
export PATH=$HOME/.gem-installed/bin:$PATH ; GEM_HOME=$HOME/.gem-installed rake spec