Tweak README and comments adding the SUBNET env var

README.md

@@ -74,9 +74,19 @@ is rooted.
 The topology used is `net30`, because it works on the widest range of OS.
 `p2p`, for instance, does not work on Windows.
 
-The TCP by default server uses `192.168.255.0/25` and the UDP server uses
-`192.168.255.128/25`. You can override subnet (three octets, for now you can't override mask) by `SUBNET` variable.  
-For example `docker run -d --privileged -p 1194:1194/udp -p 443:443/tcp -e SUBNET=192.168.13 jpetazzo/dockvpn`
+The TCP server uses `192.168.255.0/25` and the UDP server uses
+`192.168.255.128/25`. However, you can change these subnets by
+setting the `SUBNET` environment variable. Note that at the moment,
+you can only specify the first three octets of the subnet, and
+the TCP and UDP servers will use the lower /25 and upper /25
+subnets respectively.
+
+For instance, you can do:
+
+```bash
+docker run -d --privileged -p 1194:1194/udp -p 443:443/tcp \
+       -e SUBNET=192.168.13 jpetazzo/dockvpn
+```
 
 The client profile specifies `redirect-gateway def1`, meaning that after
 establishing the VPN connection, all traffic will go through the VPN.

bin/run

@@ -1,6 +1,7 @@
 #!/bin/sh
 
-VPN_SUBNET="${SUBNET:-192.168.255}" # You can override subnet of VPN
+# The subnet can be overridden with an environment variable
+VPN_SUBNET="${SUBNET:-192.168.255}"
 
 set -e