Packet generator for ICN

The packet generator for ICN requires at least 3 vpp nodes: an icn packet generator
client, an icn packet generator server and a third vpp node running the
cicn-plugin. Both icn packet generator client and server are are part of the
cicn-plugin for vpp. The topology should be similar to the following:

vpp1 (PG client) <--> vpp2 (cicn-plugin) <--> vpp3 (PG server)

vpp2 is the node that we are going to benchmark.

The current packet generator client requests subsequent content to the packet
generator server. Interest and content name is the following:

ccnx:/ccnxpg/<Chunk_number>

The Chunk number (u64) is iteratively incremented after an interest is issued.


CONFIGURATION
Vpp1 must contain a pg interface (e.g., pg0) configured
with the IP address 192.168.128.245 and be able to forward packet to
192.168.128.1. The following configuration takes care of setting the pg
interface, setting 192.168.128.1 reachable through the pg interface and the icn
pg client. It assume that the next cicn hop answer to the ip 192.168.128.2 and
it is reachable through a local interface with the ip address
192.168.128.3. There ip addresses can be set arbitrarily, modifications must be
done in both vpp1 and vpp2. IMPORTANT: In the following example, the port 33301
is used to pass packets to the icn pg client plugin. Modification to such port 
requires to change the packet definition on the icn-pg file.

vpp# exec <path-to>/icn-pg
vpp# set int ip addr pg0 192.168.128.245/24
vpp# cicn pgen client port 33301 src 192.168.128.3:33301 dest 192.168.128.2:6363

To run the icn_pg packet generator script configure vpp as follows.

vpp# packet-generator enable

Following the example, Vpp2 must be set to be reachable to the ip address
192.168.128.2 and have a face
192.168.128.2:6363<-->192.168.128.3:33301. Moreover vpp2 must be able to forward
packets (and interest) to the packet generator server.

Vpp3 configuration is simple. It must be configured to accept packets from
vpp2. The cicn packet generator plugin can be configured in this way:

vpp# cicn pgen server port 6363 size 1200