Re: [PATCH v2 net-next 2/2] net/sched: allow flower to match tunnel options

Wed, Sep 27, 2017 at 03:50:44PM CEST, simon.horman@netronome.com wrote:

On Wed, Sep 27, 2017 at 03:47:50PM +0200, Jiri Pirko wrote:

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Wed, Sep 27, 2017 at 03:37:33PM CEST, simon.horman@netronome.com wrote:

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On Wed, Sep 27, 2017 at 02:56:03PM +0200, Jiri Pirko wrote:

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Wed, Sep 27, 2017 at 02:52:06PM CEST, simon.horman@netronome.com wrote:

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On Wed, Sep 27, 2017 at 01:08:22PM +0200, Jiri Pirko wrote:

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Wed, Sep 27, 2017 at 11:27:33AM CEST, simon.horman@netronome.com wrote:

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On Wed, Sep 27, 2017 at 11:10:05AM +0200, Jiri Pirko wrote:

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Wed, Sep 27, 2017 at 10:16:34AM CEST, simon.horman@netronome.com wrote:

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enum flow_dissector_key_id {
	FLOW_DISSECTOR_KEY_CONTROL, /* struct flow_dissector_key_control */
	FLOW_DISSECTOR_KEY_BASIC, /* struct flow_dissector_key_basic */

@@ -205,6 +217,7 @@ enum flow_dissector_key_id {

	FLOW_DISSECTOR_KEY_MPLS, /* struct flow_dissector_key_mpls */
	FLOW_DISSECTOR_KEY_TCP, /* struct flow_dissector_key_tcp */
	FLOW_DISSECTOR_KEY_IP, /* struct flow_dissector_key_ip */
+	FLOW_DISSECTOR_KEY_ENC_OPTS, /* struct flow_dissector_key_enc_opts */

I don't see the actual dissection implementation. Where is it?
Did you test the patchset?

Yes, I did test it. But it is also possible something went astray along the
way and I will retest.

I think that the code you are looking for is in
fl_classify() in this patch.

The dissection should be done in the flow_dissector. That's the whole
point in having it generic. You should move it there.

Coming back to this after lunch, I believe what I have done in this patch
is consistent with handling of other enc fields, which are set in
fl_classify() rather than the dissector. In particular the ip_tunnel_info,
which is used by this patch, is already used in fl_classify().

That means the current code is wrong. The dissection should be done in
flow_dissector, not in fl_classify.

Would an better approach be to move the fl_classify() below into, say,
skb_flow_dissect_tunnel_info() and call that from fl_classify().

No. There is one flow dissection function and you just set it up in a
way you need it. Makes no sense to me to split it up in any way.

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The reason I suggest this rather than moving the code into
__skb_flow_dissect() is that currently flower assumes that tunnel_info
is used if present. While I assume other users of () assume tunnel_info
is not used even if present.

__skb_flow_dissect should look at what caller wants, then check skb_tunnel_info
only in case it is needed.

Ok, do you think it is sufficient for __skb_flow_dissect to look at the
tunnel keys, say FLOW_DISSECTOR_KEY_ENC_*? I am a bit concerned this may
break flower as it look at the tunnel info unconditionally.

yeah. When flower needs that, it will get that from the flow dissector.
I don't see why it would break anything. Again, existing code is wrong:
commit bc3103f1ed405de587fa43d8b0671e615505a700
Author: Amir Vadai [off-list ref]
Date:   Thu Sep 8 16:23:47 2016 +0300

    net/sched: cls_flower: Classify packet in ip tunnels

The dissection has to be moved to flow dissector.