dhcp: document timeout flag

Related to containernetworking/plugins#565

Signed-off-by: tlwr <[email protected]>

content/plugins/ipam/dhcp.md

@@ -24,13 +24,15 @@ $ ./dhcp daemon
 ```
 
 If given `-pidfile <path>` arguments after 'daemon', the dhcp plugin will write
-its PID to the given file.  
+its PID to the given file.
 If given `-hostprefix <prefix>` arguments after 'daemon', the dhcp plugin will
 use this prefix for DHCP socket as `<prefix>/run/cni/dhcp.sock`. You can use
 this prefix for references to the host filesystem, e.g. to access netns and the
-unix socket.  
+unix socket.
 If given `-broadcast=true` argument after 'daemon', the dhcp plugin will
 enable the broadcast flag on DHCP packets.
+If given `-timeout <duration>` arguments after 'daemon', the dhcp daemon will
+time out unanswered dhcp requests after this duration, defaults to `10s`.
 
 Alternatively, you can use systemd socket activation protocol.
 Be sure that the .socket file uses /run/cni/dhcp.sock as the socket path.