The action is not yet implemented for the datapath. I’ve made some changes in 
the ofproto-dpif-xlate. When I start the vswitchd the kernel module is loaded, 
but I unload it with modprobe -r openvswitch. When I start a communication, add 
flows via ofctl, actions are added and the packet mangling works on the first 
packet, however ovs-dpctl says no dapatath exists.

root@osv:~# ovs-dpctl dump-flows
ovs-dpctl: no datapaths exist
root@osv:~#

I’ve also set root@osv:~# ovs-vsctl set bridge br0 datapath_type=netdev, which 
I’m not quite sure what it does.

current changes I’ve made are here 
https://github.com/fr6nco/ovs/compare/v2.8.1...fr6nco:seq_ack_experimenter 
<https://github.com/fr6nco/ovs/compare/v2.8.1...fr6nco:seq_ack_experimenter>
I’ve forked it from v2.8.1 tag.

Does the userspace code have a fast_path too..or fast_path means it is 
processed in the kernel? Currently i get around 10Mbits of speed, so I assume 
the communication goes through the userspace, but my custom action in the 
lib/packets.c:inc_seq is not reached for subsequent packets.

Tomas


> On 11 Jan 2018, at 22:02, Ben Pfaff <[email protected]> wrote:
> 
> On Thu, Jan 11, 2018 at 09:47:16PM +0100, Thomas Boros wrote:
>> for my PhD studies Im implementing a new action, which modifies the
>> sequence number in the TCP header. I’ve managed to add the action,
>> however the action is applied only on the first packet. I’ve disabled
>> the kernel datapath during this development, however I have no idea
>> where to make changes to apply my modification on the fast path. I
>> see, when a first packet arrives a cache miss occurs in the
>> fast_path_processing (file lib/dpif-netdev.c). Could you give some
>> hints how to implement my custom action, so it will modify packets on
>> the fast_path too? Or how the switch behaves when the kernel module is
>> enabled? Do the packet processing goes through the fast_path or
>> remains in the kernel datapath?
> 
> Did you implement the action as a datapath action and make the
> translation code in ofproto-dpif-xlate emit that datapath action?

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