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diff --git a/Documentation/faq/openflow.rst b/Documentation/faq/openflow.rst index 7cd6161dd..f722f9e78 100644 --- a/Documentation/faq/openflow.rst +++ b/Documentation/faq/openflow.rst @@ -516,44 +516,6 @@ but the packets are getting dropped instead. Why? See also the preceding question. -Q: The "learn" action can't learn the action I want, can you improve it? - - A: By itself, the "learn" action can only put two kinds of actions into the - flows that it creates: "load" and "output" actions. If "learn" is used in - isolation, these are severe limits. - - However, "learn" is not meant to be used in isolation. It is a primitive - meant to be used together with other Open vSwitch features to accomplish a - task. Its existing features are enough to accomplish most tasks. - - Here is an outline of a typical pipeline structure that allows for - versatile behavior using "learn": - - - Flows in table A contain a "learn" action, that populates flows in table - L, that use a "load" action to populate register R with information about - what was learned. - - - Flows in table B contain two sequential resubmit actions: one to table L - and another one to table B+1. - - - Flows in table B+1 match on register R and act differently depending on - what the flows in table L loaded into it. - - This approach can be used to implement many "learn"-based features. For - example: - - - Resubmit to a table selected based on learned information, e.g. see: - https://mail.openvswitch.org/pipermail/ovs-discuss/2016-June/021694.html - - - MAC learning in the middle of a pipeline, as described in - :doc:`/tutorials/ovs-advanced` - - - TCP state based firewalling, by learning outgoing connections based on - SYN packets and matching them up with incoming packets. - - - At least some of the features described in T. A. Hoff, "Extending Open - vSwitch to Facilitate Creation of Stateful SDN Applications". - Q: When using the "ct" action with FTP connections, it doesn't seem to matter if I set the "alg=ftp" parameter in the action. Is this required? |