[ovs-discuss] Query related to invalid_ttl support

Ben Pfaff blp at ovn.org
Wed Sep 25 16:03:41 UTC 2019

On Mon, Sep 09, 2019 at 10:25:02PM +0530, bindiya Kurle wrote:
> Hi ,
> I was going through the code when ttl =0 and action is set as dec_ttl
> for ex:  TTL of the packet is 1 and rule in ovs is ,
> ovs-ofctl add-flow vnf-net0 "table=1,in_port=1 actions=dec_ttl,output:2"
>  from the 2.11 code.
> for this case it calls
>         for (i = 0; i < ids->n_controllers; i++) {
>             xlate_controller_action(ctx, UINT16_MAX, OFPR_INVALID_TTL,
>                                     ids->cnt_ids[i], UINT32_MAX, NULL, 0);
> this in turn calls,
> put_controller_user_action
> This in turn will create user-space action. I am not getting where in the
> code, it is generating message towards controller for invalid ttl.

The userspace action sends a Netlink message to userspace, which in turn
gets classified in classify_upcall() in ofproto-dpif-upcall.c as a
CONTROLLER_UPCALL, which gets handled in process_upcall() by appending
to the async message queue, which run() in ofproto-dpif.c eventually
processes via connmgr_send_async_msg().

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