Adds flow to host port in its attached switch

Adds flow to host port in its attached switch.



An overall description of the CPM functionality is available in weekly report:
https://docs.google.com/document/d/1SRaaDnfsmpT5etjjAaqH1VTb5wxo4lvX4G8QE4ulruA/edit?usp=sharing

[Michail.Xirouchakis, 2017-10-03 15:20:47]

Hello everyone,

Pleare review my overall CPM implementation. You can read about its current
functionality in weekly report:

https://docs.google.com/document/d/1SRaaDnfsmpT5etjjAaqH1VTb5wxo4lvX4G8QE4ulr...

[Vasileios Papageorgiou, 2017-10-05 21:09:43]

Hi , Michail! 
I have just reviewed your code by adding some comments.

BR,

Vasileios Papageorgiou

https://codereview.appspot.com/330430043/diff/1/cpm/cpm_spf_13.py
File cpm/cpm_spf_13.py (right):

https://codereview.appspot.com/330430043/diff/1/cpm/cpm_spf_13.py#newcode64
cpm/cpm_spf_13.py:64: def _find_all_paths(self, neighbors, start, end, path=[]):
Is that method to find the shortest path or combinations of finding paths and
the calculate the shortest one ? IS def_run_spf(self,switch a, switch z) the
method that calculates the shortest path in the end?

https://codereview.appspot.com/330430043/diff/1/cpm/cpm_spf_13.py#newcode80
cpm/cpm_spf_13.py:80: hop_count = 1000  # Just an arbitrary high value
you can define this arbitrary high value in the beginning of the program so that
if you want to make a change on the number it would not affect the code. Eg.
hop_count = Arbitary_Value

https://codereview.appspot.com/330430043/diff/1/cpm/cpm_spf_13.py#newcode107
cpm/cpm_spf_13.py:107: self.add_flow(switchA_datapath, 100, matchA, actionsA)
what is number 100?

https://codereview.appspot.com/330430043/diff/1/cpm/cpm_spf_13.py#newcode131
cpm/cpm_spf_13.py:131: if pkt_arp.opcode != arp.ARP_REQUEST:
 Have you noticed going inside the if?

https://codereview.appspot.com/330430043/diff/1/cpm/cpm_spf_13.py#newcode146
cpm/cpm_spf_13.py:146: self.add_flow(datapath, 150, match, actions)
what is the number 150?

[engr.sikandar.iqbal, 2017-10-09 21:18:48]

Hi Michail, 
Your code is quite defined, I have made some comments on your code.
BR, 
Sikandar Iqbal

https://codereview.appspot.com/330430043/diff/1/cpm/cpm_spf_13.py
File cpm/cpm_spf_13.py (right):

https://codereview.appspot.com/330430043/diff/1/cpm/cpm_spf_13.py#newcode68
cpm/cpm_spf_13.py:68: if start not in neighbors.keys():
if start not in neighbors.keys():
&
if start not in neighbors.keys():
Are these in comments or part of the code?