When printing a flow, there were two references to "port": one the
interface the packet arrived on and the other the L4 ports. This could
be a bit confusing to new users looking at the output of a command such
as "ovs-ofctl dump-flows". This commit changes the incoming interface
field from "port" to "in_port".
The ability to match the IP addresses in ARP packets allows for fine-grained
control of ARP processing. Some forthcoming changes to allow in-band
control to operate over L3 requires this support if we don't want to
allow overly broad rules regarding ARPs to always be white-listed.
Unfortunately, OpenFlow does not support this sort of processing yet, so
we must treat OpenFlow ARP rules as having wildcarded those L3 fields.
