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

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Date:   Thu, 19 Jul 2018 15:02:28 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     netdev@...r.kernel.org
Cc:     Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Daniel Borkmann <daniel@...earbox.net>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Eyal Birger <eyal.birger@...il.com>
Subject: [PATCH net-next 3/4] net/tc: introduce TC_ACT_MIRRED.

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);
+		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