Older versions of OpenFlow pre-defined a few different types of tables and the
Features Reply message would indicate how many of those entries existed. This
was very inflexible, so now the Features Reply just indicates how many tables
there are. The controller now sends a Table Stats request to find out how
many entries are supported and the fields that can be wildcarded.
This change also removes the "buffer_mb" field from the Features Reply, since
it was not being used and seemed to be of limited value.
The original packet-out format allowed multiple actions to be specified for
buffered packets, but only a destination port for messages including data.
This change makes packet-out more consistent by allowing multiple actions
regardless of how the packet is stored.
This change also disallows sending packets through the incoming port without
explicitly using the OFPP_IN_PORT virtual port.
Now it helps clients track the number of in-flight messages, but lets the
clients do the limiting themselves. This will come in handy for packet-in
rate limiting (in an upcoming commit), in which we want to track in-flight
packet-in messages separately from other in-flight messages.
Checking the current time only when a periodic timer expires allows us
to reduce the number of system calls to obtain the current time to 10 per
second (from an arbitrary number) plus one per poll loop.
This fixes poll_block() to properly handle being interrupted.
Otherwise, a timeout longer than the interval between signals will never
complete (because it will restart from the beginning after every
signal).
This updates the OpenFlow protocol version and changes the names of
structure members, so any software that uses OpenFlow will need to be
updated to match.
Before, if a hub connected a number of OpenFlow switches and the controller,
then in-band control traffic from one of the OpenFlow switches would be
seen by each of the other switches and forwarded up to the controller as
an ofp_packet_in message. That message would then be seen by all of the
other OpenFlow switches and also forwarded, and so on in an infinite loop.
This change prevents this situation by keeping secchan from forwarding
ofp_packet_in messages for a packet destined to the controller that
arrives on the port where the controller is located.
This code has at least two weaknesses. First, if the controller's port
changes, then the flows set up to drop packets will not be deleted. This
should not be a major problem: if this inadvertently kills a switch's
connection to the controller, then the switch will realize it after it
stops receiving data and re-connect. Its new connection will have new
flow data and therefore its packets will not be dropped.
Second, the notion of the "controller's port" does not take into account
the possibility of loops in the network topology. We need spanning tree
protocol for that.
Ben Pfaff
Justin Pettit