[ovs-dev] [PATCH] [RFC] Add a new OVS action check_pkt_larger

Numan Siddique nusiddiq at redhat.com
Wed Nov 7 15:39:26 UTC 2018


On Tue, Nov 6, 2018, 2:26 AM Ben Pfaff <blp at ovn.org wrote:

> On Mon, Nov 05, 2018 at 09:45:10PM +0530, nusiddiq at redhat.com wrote:
> > From: Numan Siddique <nusiddiq at redhat.com>
> >
> > This patch adds a new action 'check_pkt_larger' which checks if the
> > packet is larger than the given size and stores the result in the
> > destination register.
> >
> > Usage: check_pkt_larger:len->REGISTER
> > Eg. match=...,actions=check_pkt_larger:1442->NXM_NX_REG0[0],next;
> >
> > When translating this action, SLOW_ACTION is set so that datapath
> > flow is not added.
> >
> > This action is intended to be used by OVN to check the packet length
> > and generate an ICMP packet with type 3, code 4 and next hop mtu
> > in the logical router pipeline if the MTU of the physical interface
> > is lesser than the packet length. More information can be found here [1]
> >
> > TODO:
> >  - Add test case.
> >  - Change the action format from check_pkt_larger:len to
> check_pkt_larger(len)
> >
> > Request to suggest a better name for the action in case
> 'check_pkt_larger'
> > seems odd.
> >
> > [1] -
> https://mail.openvswitch.org/pipermail/ovs-discuss/2018-July/047039.html
> >
> > Signed-off-by: Numan Siddique <nusiddiq at redhat.com>
>
> Thanks for working on this.
>
> It looks like this patch makes the assumption that every packet goes
> through userspace, but that isn't true.  The action needs to be
> implemented in the OVS datapaths so that the kernel or userspace can
> direct oversized packets to the slow path.
>
> Thanks,
>

Thanks for the comments. I'll address these before I submit a formal patch.

Thanks
Numan


> Ben.
>


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