On Fri, Sep 29, 2017 at 05:54:23AM +0100, David Miller wrote: > From: Simon Horman <simon.hor...@netronome.com> > Date: Wed, 27 Sep 2017 10:16:32 +0200 > > > Users of options: > > > > * There are eBPF hooks to allow getting on and setting tunnel metadata: > > bpf_skb_set_tunnel_opt, bpf_skb_get_tunnel_opt. > > > > * Open vSwitch is able to match and set Geneve and VXLAN-GBP options. > > > > Neither of the above appear to assume any structure for the data. > > I really worry about this. > > These metadata option blobs are internal kernel datastructure which we > could change at any point in time. They are not exported to > userspace as a UAPI. > > It's kinda OK for eBPF programs to access this stuff since they are > expected to cope with changes to internal data-structures. > > But for anything user facing, this really doesn't work.
Hi Dave, Hi Jiri, the feedback I got from Jiri is that there needs to be some exposure of TLVs. What I have in mind is to describe Geneve option TLVs in the UAPI and for the kernel - most likely cls_flower, possibly using helpers, to translate between that encoding and the one used internally by the kernel - which currently happens to be the on-the-wire format. I believe that in order to avoid per-packet overhead and at the same time code complexity the TLVs should be described in-order. So matching on TLV-A,TLV-B,TLV-C would be a different match to TLV-C,TLV-A,TLV-B. An order-independent match could be added if desired in future. This would mean the feature is initially restricted to Geneve but could be expended to offer a similar feature for other encapsulation protocols as the need arises. Would this address your concerns?
