title: How to decrement the ttl/hoplimit of packets at OpenFlow switches?
body: <p>I know it is possible to add or modify single flows of OpenFlow switches to decrement the TTL(IPv4) or the hop limit (IPv6).</p>
  
  <p>I tested it with the floodlight controller and the following flow entry</p>
  
  <pre><code>ovs-ofctl -O OpenFlow13 add-flow s1 "priority=1,ip,in_port=2,dl_src=&lt;src_mac&gt;,dl_dst=&lt;dst-mac&gt;,nw_src=10.0.0.1,nw_dst=10.0.0.2 actions=dec_ttl,output:1"
  </code></pre>
  
  <p>But how can I do this for all UDP IPv6 packets passing a switch?
  I can not update all flows all the time.</p>
  
  <p>I want to simulate the decrementing of the ttl/hoplimit like it is done in IP routers with SDN switches. The testbed I am using is build with Mininet and Open vSwitch switches running in kernel mode.</p>
  
  <p>I don't want to write a whole SDN Controller and I also don't want to implement all flows by myself. I just want the switches to decrement the ttl/hop limit of every UDP IPv6 packet passing.</p>