On Mon, Nov 28, 2011 at 09:02:34AM -0500, Jamal Hadi Salim wrote:
> On Mon, 2011-11-28 at 21:04 +0800, Herbert Xu wrote:
> > However, what's more worrying for me right now is the gaping
> > DoS opportunities that exist in the patch as is.
> >
> > In particular, the whole design principle of punting all new
> > flows to user-space is an excellent way of attacking the system.
>
> Indeed this is an issue with openflow in general.
> The general solution is to rate limit how much goes to the controller
> but even that is insufficient.
Regarding OpenFlow rate limiting, in addition to Martin's response, Open
vSwitch has implemented controller rate limiting since day one. It is
documented in ovs-vswitchd.conf.db(5):
OpenFlow Rate Limiting:
controller_rate_limit: optional integer, at least 100
The maximum rate at which packets in unknown flows will be for-
warded to the OpenFlow controller, in packets per second. This
feature prevents a single bridge from overwhelming the con-
troller. If not specified, the default is implementation-spe-
cific.
In addition, when a high rate triggers rate-limiting, Open
vSwitch queues controller packets for each port and transmits
them to the controller at the configured rate. The number of
queued packets is limited by the controller_burst_limit value.
The packet queue is shared fairly among the ports on a bridge.
Open vSwitch maintains two such packet rate-limiters per bridge.
One of these applies to packets sent up to the controller
because they do not correspond to any flow. The other applies
to packets sent up to the controller by request through flow
actions. When both rate-limiters are filled with packets, the
actual rate that packets are sent to the controller is up to
twice the specified rate.
controller_burst_limit: optional integer, at least 25
In conjunction with controller_rate_limit, the maximum number of
unused packet credits that the bridge will allow to accumulate,
in packets. If not specified, the default is implementation-
specific.
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