On 7/20/23 17:06, Mike Pattrick wrote: > When the a revalidator thread is updating statistics for an XC_LEARN > xcache entry in xlate_push_stats_entry it uses ofproto_flow_mod_learn. > The revalidator will update stats for rules even if they are in a > removed state or marked as invisible. However, ofproto_flow_mod_learn > will detect if a flow has been removed and re-add it in that case. This > can result in an old learn action replacing the new learn action that > had replaced it in the first place. > > This change adds a new parameter to ofproto_flow_mod_learn allowing the > caller to specify an action to take if temp_rule is removed. If it is > removed and the caller is xlate_push_stats_entry, then a new rule will > not be replaced.
Hi, Mike. That's an interesting issue, though I'm not sure that is a correct way to fix it. It is important to re-install removed learned flows during stats update. The logic is the following, AFAIU: 1. Packet hits the OF rule (1) with a learning action. 2. Handler translates OF and creates a datapath flow for it, creating a learned rule (2) in the process and filling the translation cache. 3. Datapath flow for the rule (1) is installed into the datapath. 4. Time goes by and timeout on the learned rule (2) hits. Learned rule is removed now. 5. A packet hits the datapath flow for rule (1). 6. Revalidator updates flow stats for the rule (1). 7. Since the packet hit the learning rule (1), the rule (2) has to be added back. IIUC, the step 7 will not happen with the change proposed in this patch. Flow will not be re-translated, so the only way to re-install it is to execute side effects when we see stats update on a parent datapath flow in the revalidator. One potential way to avoid breaking this scenario is to check the removal reason, but it's not bulletproof either as we do still need to reinstate the flow even if it was manually deleted or evicted. It also seems like we may hold the reference to this deleted rule for a long time in the cache until the parent datapath flow is deleted. What is triggering the deletion of the learned rule in your case? Is it deletion or modification of the parent rule? And does it have 'delete_learned' flag? Best regards, Ilya Maximets. _______________________________________________ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev
