netdev - Re: [PATCH net-next 3/4] net/tc: introduce TC_ACT

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Message-ID: <20180719185600.GI2184@nanopsycho.orion>
Date:   Thu, 19 Jul 2018 20:56:00 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Eyal Birger <eyal.birger@...il.com>
Subject: Re: [PATCH net-next 3/4] net/tc: introduce TC_ACT_MIRRED.

Thu, Jul 19, 2018 at 03:02:28PM CEST, pabeni@...hat.com wrote:
>This is similar TC_ACT_REDIRECT, but with a slightly different
>semantic:
>- on ingress the mirred skbs are passed to the target device
>network stack without any additional check not scrubbing.
>- the rcu-protected stats provided via the tcf_result struct
>  are updated on error conditions.
>
>v1 -> v2: do not touch TC_ACT_REDIRECT code path, introduce
> a new action type instead
>
>Signed-off-by: Paolo Abeni <pabeni@...hat.com>
>---
> include/net/sch_generic.h    | 19 +++++++++++++++++++
> include/uapi/linux/pkt_cls.h |  3 ++-
> net/core/dev.c               |  4 ++++
> net/sched/act_api.c          |  6 ++++--
> 4 files changed, 29 insertions(+), 3 deletions(-)
>
>diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
>index 056dc1083aa3..667d7b66fee2 100644
>--- a/include/net/sch_generic.h
>+++ b/include/net/sch_generic.h
>@@ -235,6 +235,12 @@ struct tcf_result {
> 			u32		classid;
> 		};
> 		const struct tcf_proto *goto_tp;
>+
>+		/* used by the TC_ACT_MIRRED action */
>+		struct {
>+			bool		ingress;
>+			struct gnet_stats_queue *qstats;
>+		};
> 	};
> };
> 
>@@ -1091,4 +1097,17 @@ void mini_qdisc_pair_swap(struct mini_Qdisc_pair *miniqp,
> void mini_qdisc_pair_init(struct mini_Qdisc_pair *miniqp, struct Qdisc *qdisc,
> 			  struct mini_Qdisc __rcu **p_miniq);
> 
>+static inline void skb_tc_redirect(struct sk_buff *skb, struct tcf_result *res)
>+{
>+	struct gnet_stats_queue *stats = res->qstats;
>+	int ret;
>+
>+	if (res->ingress)
>+		ret = netif_receive_skb(skb);
>+	else
>+		ret = dev_queue_xmit(skb);
>+	if (ret && stats)
>+		qstats_overlimit_inc(res->qstats);
>+}
>+
> #endif
>diff --git a/include/uapi/linux/pkt_cls.h b/include/uapi/linux/pkt_cls.h
>index 7cdd62b51106..1a5e8a3217f3 100644
>--- a/include/uapi/linux/pkt_cls.h
>+++ b/include/uapi/linux/pkt_cls.h
>@@ -45,7 +45,8 @@ enum {
> 				   * the skb and act like everything
> 				   * is alright.
> 				   */
>-#define TC_ACT_LAST		TC_ACT_TRAP
>+#define TC_ACT_MIRRED		9
>+#define TC_ACT_LAST		TC_ACT_MIRRED
> 
> /* There is a special kind of actions called "extended actions",
>  * which need a value parameter. These have a local opcode located in
>diff --git a/net/core/dev.c b/net/core/dev.c
>index 14a748ee8cc9..3822f29d730f 100644
>--- a/net/core/dev.c
>+++ b/net/core/dev.c
>@@ -4602,6 +4602,10 @@ sch_handle_ingress(struct sk_buff *skb, struct packet_type **pt_prev, int *ret,
> 		__skb_push(skb, skb->mac_len);
> 		skb_do_redirect(skb);
> 		return NULL;
>+	case TC_ACT_MIRRED:
>+		/* this does not scrub the packet, and updates stats on error */
>+		skb_tc_redirect(skb, &cl_res);

REDIRECT does skb_do_redirect and MIRRED does skb_tc_redirect.
Confusing. I agree with Cong that the name is not correct.


>+		return NULL;
> 	default:
> 		break;
> 	}
>diff --git a/net/sched/act_api.c b/net/sched/act_api.c
>index f6438f246dab..029302e2813e 100644
>--- a/net/sched/act_api.c
>+++ b/net/sched/act_api.c
>@@ -895,8 +895,10 @@ struct tc_action *tcf_action_init_1(struct net *net, struct tcf_proto *tp,
> 		}
> 	}
> 
>-	if (a->tcfa_action == TC_ACT_REDIRECT) {
>-		net_warn_ratelimited("TC_ACT_REDIRECT can't be used directly");
>+	if (a->tcfa_action == TC_ACT_REDIRECT ||
>+	    a->tcfa_action == TC_ACT_MIRRED) {
>+		net_warn_ratelimited("action %d can't be used directly",
>+				     a->tcfa_action);
> 		a->tcfa_action = TC_ACT_LAST + 1;
> 	}
> 
>-- 
>2.17.1
>