grow the README

README.md

@@ -1,5 +1,26 @@
-edit the list of game to your liking then run:
+go-broadcast is a small go utilities for repeating UDP broadcast packet accross linux interfaces.
+
+It will take a configuration file containing the list of port which broadcast should be mirrored. 
+This configuration is contained in games.csv. It will also take a list of the interfaces on which 
+it should listen for broadcast packet and mirror the packet.
+
+# Runing it
+
+Edit the list of game to your liking contained in games.csv. This list contains a name used for 
+documentation purpose and a port number used for selecting the udp broadcast packet that should be
+mirrored. Finally, define the set of interfaces used to receive udp broadcast. This set will also be 
+used as destination copy for the udp broadcast packet.
+For example, if eth0, eth1 and eth2 are the interface used to receive and mirror broadcast, then using:
 
 ```
-docker build -t proxy . && docker run --net=host proxy $INTERFACES
+docker build -t proxy . && docker run --net=host proxy eth1 eth1 eth2
 ```
+Will listen and mirror the broadcast received on any of the interface on all other interfaces.
+
+# Broadcast storm
+
+The naive approach of replicating packet would be to simply take any broadcast packet and copy it 
+on all but the interface it originated from. This would be a problem if two proxy would be active 
+on the same set of interface. One proxy would take the mirrored packet and mirror them again. This would
+create a broadcast storm. We use instead the TTL field of the UDP broadcast packet to mark a packet as 
+mirrored. Upon receiving a packet with this TTL, we will ignore it and not mirror it again.