On Jul 9, 2012, at 1:42 PM, Weiyun Mao wrote:
> Logically, when a packet comes into the controller, first, the ethernet
> header needs to be parsed,
> if it can’t be deliverd in L2, then parse the IP header, and then,
> TCP/UDP/ICMP header. Right?
Actually, it will get parsed as deeply as it can figure out how to and create a
linked list of parsed packet objects.
In a typical example, you'll have ethernet holding IP holding TCP:
ether_packet = packet
ip_packet = packet.next
tcp_packet = packet.next.next
You might be better searching for the packet type you want, since there may be
unexpected encapsulations.
ip_packet = packet.find("ipv4")
Hope that helps clear things up.
As a sidenote, it looks like you're using NOX-Classic, which we're not really
maintaining now. If you're writing controllers in Python, you might look at
POX (which, among other things, has an improved version of the packet library).
-- Murphy
