netdev - Re: [net-next PATCH 4/4] net: sched: create hardware only classifier filter

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Date:	Wed, 24 Feb 2016 09:47:28 +0100
From:	Jiri Pirko <jiri@...nulli.us>
To:	John Fastabend <john.fastabend@...il.com>
Cc:	daniel@...earbox.net, netdev@...r.kernel.org,
	alexei.starovoitov@...il.com, davem@...emloft.net, jhs@...atatu.com
Subject: Re: [net-next PATCH 4/4] net: sched: create hardware only classifier
 filter

Tue, Feb 23, 2016 at 08:03:56PM CET, john.fastabend@...il.com wrote:
>If users want to run filters specifically in hardware without software
>running the classifiers we need to use a special handler for this.
>By using a new classifier list we are able to add filters in hardware
>and keep all the same semantics in the core module. So the core code
>will continue to block duplicate entries, incorrect usage of flags
>such as exclusive, and all the other cases software already handles.
>
>Additionally by having a filter list that is not run by software in
>the datapath we avoid any overhead related to adding these rules in
>the hot path.
>
>The new filter list TC_H_MIN_INGRESS_HW is logically run in front
>of the TC_H_MIN_INGRESS filter list. Driver writers can avoid aborting
>on many cases that would potentially conflict with software rules in
>the TC_H_MIN_INGRESS filter list this way.

Oh, although it looks straightforward to implement this, I don't like it.
User should be able to do the same thing he did before, only extension
would be to allow to pass 2 flags for adding rules:
SKIP_HW
SKIP_SW

Default would be to add rule to both.
u32 and other classifiers should take care of processing this flags
internaly and act accordingly. The implementation can be just to skip
rule in sw processing or it can maintain hw-only structures.


>
>Signed-off-by: John Fastabend <john.r.fastabend@...el.com>
>---
> include/linux/netdevice.h      |    1 +
> include/uapi/linux/pkt_sched.h |    1 +
> net/sched/sch_ingress.c        |    5 +++++
> 3 files changed, 7 insertions(+)
>
>diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
>index 47671ce0..df0ca01 100644
>--- a/include/linux/netdevice.h
>+++ b/include/linux/netdevice.h
>@@ -1741,6 +1741,7 @@ struct net_device {
> 
> #ifdef CONFIG_NET_CLS_ACT
> 	struct tcf_proto __rcu  *ingress_cl_list;
>+	struct tcf_proto __rcu  *ingress_hw_cl_list;
> #endif
> 	struct netdev_queue __rcu *ingress_queue;
> #ifdef CONFIG_NETFILTER_INGRESS
>diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h
>index 8cb18b4..e2899c2 100644
>--- a/include/uapi/linux/pkt_sched.h
>+++ b/include/uapi/linux/pkt_sched.h
>@@ -76,6 +76,7 @@ struct tc_estimator {
> 
> #define TC_H_MIN_INGRESS	0xFFF2U
> #define TC_H_MIN_EGRESS		0xFFF3U
>+#define TC_H_MIN_INGRESS_HW	0xFFF4U
> 
> /* Need to corrospond to iproute2 tc/tc_core.h "enum link_layer" */
> enum tc_link_layer {
>diff --git a/net/sched/sch_ingress.c b/net/sched/sch_ingress.c
>index 10adbc6..792b85c 100644
>--- a/net/sched/sch_ingress.c
>+++ b/net/sched/sch_ingress.c
>@@ -104,6 +104,7 @@ static unsigned long clsact_get(struct Qdisc *sch, u32 classid)
> 	switch (TC_H_MIN(classid)) {
> 	case TC_H_MIN(TC_H_MIN_INGRESS):
> 	case TC_H_MIN(TC_H_MIN_EGRESS):
>+	case TC_H_MIN(TC_H_MIN_INGRESS_HW):
> 		return TC_H_MIN(classid);
> 	default:
> 		return 0;
>@@ -126,6 +127,8 @@ static struct tcf_proto __rcu **clsact_find_tcf(struct Qdisc *sch,
> 		return &dev->ingress_cl_list;
> 	case TC_H_MIN(TC_H_MIN_EGRESS):
> 		return &dev->egress_cl_list;
>+	case TC_H_MIN(TC_H_MIN_INGRESS_HW):
>+		return &dev->ingress_hw_cl_list;
> 	default:
> 		return NULL;
> 	}
>@@ -148,6 +151,8 @@ static void clsact_destroy(struct Qdisc *sch)
> 	tcf_destroy_chain(&dev->ingress_cl_list);
> 	tcf_destroy_chain(&dev->egress_cl_list);
> 
>+	tcf_destroy_chain(&dev->ingress_hw_cl_list);
>+
> 	net_dec_ingress_queue();
> 	net_dec_egress_queue();
> }
>