[ovs-discuss] ovs code flow

Amit Tewari Amit.Tewari at nechclst.in
Tue Jan 10 17:17:23 UTC 2012


hi,

I am currently into analyzing ovs code flow for rule matching in flow tables when a packet arrives.
1.when a packet arrives and no matching exact match flow is found in datapath then a facet is created in userspace. this facet has follwing members
facet->rule and facet->flow.
facet->flow is exact match flow that is installed in datapath using facet->install 

2. Now if the facet->rule (matched with packet flow) has modifying actions for example strip_vlan, then as per do_xlate_actions routine i found that all modifying actions are applied on facet->flow.

3. Now this modified facet->flow is installed in datapath.

Im confused why facet->flow is modified for modifying actions, as per me these actions should be applied on packet. 

Is modifying actions like stip_vlan or set_nw_destination address etc are applied on flow but these actions should be applied on packet.

Now since flow is modified and then inserted in datapath, that means next time if same packet arrives it will have no matching flow in datapath and hence again it will go to user space.

please let me know if i am missing something in code.






Regards,
Amit Tewari
NEC-HCL ST

















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