Add an example of LXC bridging

README.md

@@ -296,6 +296,52 @@ Then connect over the tunnel to the second node:
     ping 10.10.10.2
     ssh 10.10.10.2
 
+### Bridging
+
+`br` is an example of a simple bridge that floods frames to all the switch
+ports. `br` uses a tap device plugged into a Linux bridge as an
+uplink port and 1 or more tap devices as the switch ports.
+
+This example uses the tap devices as interfaces for Linux containers
+(LXC).
+
+* Create a bridge and attach the physical ethernet interface
+```
+# /etc/network/interfaces
+iface br0 inet dhcp
+    bridge_ports eth0
+    bridge_stp off
+    bridge_fd 0
+    bridge_maxwait 0
+```
+
+* Start the bridge:
+
+    * `erlbr0` is the name of the tap device connected to the bridge
+    * `["erl0", "erl1", "erl2"]` are the tap devices used by the containers
+
+```
+br:start("erlbr0", ["erl0", "erl1", "erl2"]).
+```
+
+* In another shell, as root, bring up the uplink and attach it to the bridge:
+
+```
+# ifconfig erlbr0 up
+# brctl addif br0 erlbr0
+# brctl show br0
+bridge name     bridge id               STP enabled     interfaces
+br0             8000.4aec6d3a44d1       no              erlbr0
+                                                        eth0
+```
+
+* Move the switch port interface into the container. The interface name inside the container will be known as "erl0".
+
+```
+lxc.network.type=phys
+lxc.network.link=erl0
+lxc.network.flags=up
+```
 
 ## TODO
 

examples/br.erl

@@ -0,0 +1,64 @@
+%% Copyright (c) 2013, Michael Santos <michael.santos@gmail.com>
+%% All rights reserved.
+%%
+%% Redistribution and use in source and binary forms, with or without
+%% modification, are permitted provided that the following conditions
+%% are met:
+%%
+%% Redistributions of source code must retain the above copyright
+%% notice, this list of conditions and the following disclaimer.
+%%
+%% Redistributions in binary form must reproduce the above copyright
+%% notice, this list of conditions and the following disclaimer in the
+%% documentation and/or other materials provided with the distribution.
+%%
+%% Neither the name of the author nor the names of its contributors
+%% may be used to endorse or promote products derived from this software
+%% without specific prior written permission.
+%%
+%% THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+%% "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+%% LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+%% FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+%% COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+%% INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+%% BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+%% LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+%% CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+%% LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+%% ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+%% POSSIBILITY OF SUCH DAMAGE.
+-module(br).
+-export([start/0, start/2]).
+
+
+start() ->
+    start("erlbr0", ["erl0"]).
+
+start(Uplink, Ifaces) ->
+    % Switch uplink
+    {ok, Br} = tuncer:create(Uplink, [tap, no_pi, {active, true}]),
+
+    % Switch ports
+    Dev = [ begin
+        {ok, N} = tuncer:create(Iface, [tap, no_pi, {active, true}]),
+        N
+      end || Iface <- Ifaces ],
+
+    switch(Br, Dev).
+
+switch(Br, Dev) ->
+    receive
+        {tuntap, Br, Data} ->
+            % Data received on uplink: flood to ports
+            error_logger:info_report([{br, Br}, {data, Data}]),
+            [ ok = tuncer:send(N, Data) || N <- Dev ],
+            switch(Br, Dev);
+        {tuntap, Port, Data} ->
+            % Data received on port: flood to all other ports and uplink
+            error_logger:info_report([{dev, Port}, {data, Data}]),
+            [ ok = tuncer:send(N, Data) || N <- Dev ++ [Br], N =/= Port ],
+            switch(Br, Dev);
+        Error ->
+            error_logger:error_report([{error, Error}])
+    end.