Based on the following patch:
From: Isaku Yamahata <yamahata@valinux.co.jp>
Subject: dpset: add port{add, delete, modify} event for convenience and helper functions
It is sometimes commonly interesting to track datapath/port
appearance/disappearance. The applications usually want to see that ports
appear after datapath becomes ready, and ports disappear when datapath is dead.
It requires to handle properly events, hand shaking, port_mod event,
switch_feature_reply. So introduce a common layer to handle them.
GRE tunnel is interested in datapath/port appearance/disappearance.
With this, tunnel app doesn't have to handle those conditions.
Discovery is interested only in datapath/port appearance/disappearance.
With this, discovery app would not have to handle OFP events directly.
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
978f3e5c0d