netdev - [RFC net-next 1/2] net: sched: refactor reinsert action

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Message-Id: <1560522831-23952-2-git-send-email-john.hurley@netronome.com>
Date:   Fri, 14 Jun 2019 15:33:50 +0100
From:   John Hurley <john.hurley@...ronome.com>
To:     netdev@...r.kernel.org
Cc:     davem@...emloft.net, fw@...len.de, jhs@...atatu.com,
        simon.horman@...ronome.com, jakub.kicinski@...ronome.com,
        oss-drivers@...ronome.com, John Hurley <john.hurley@...ronome.com>
Subject: [RFC net-next 1/2] net: sched: refactor reinsert action

The TC_ACT_REINSERT return type was added as an in-kernel only option to
allow a packet ingress or egress redirect. This is used to avoid
unnecessary skb clones in situations where they are not required. If a TC
hook returns this code then the packet is 'reinserted' and no skb consume
is carried out as no clone took place.

This return type is only used in act_mirred. Rather than have the reinsert
called from the main datapath, call it directly in act_mirred. Instead of
returning TC_ACT_REINSERT, change the type to the new TC_ACT_CONSUMED
which tells the caller that the packet has been stolen by another process
and that no consume call is required.

Moving all redirect calls to the act_mirred code is in preparation for
tracking recursion created by act_mirred.

Signed-off-by: John Hurley <john.hurley@...ronome.com>
Reviewed-by: Simon Horman <simon.horman@...ronome.com>
---
 include/net/pkt_cls.h     | 2 +-
 include/net/sch_generic.h | 2 +-
 net/core/dev.c            | 4 +---
 net/sched/act_mirred.c    | 3 ++-
 4 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/include/net/pkt_cls.h b/include/net/pkt_cls.h
index 514e3c8..3ecb5c2 100644
--- a/include/net/pkt_cls.h
+++ b/include/net/pkt_cls.h
@@ -9,7 +9,7 @@
 #include <net/flow_offload.h>
 
 /* TC action not accessible from user space */
-#define TC_ACT_REINSERT		(TC_ACT_VALUE_MAX + 1)
+#define TC_ACT_CONSUMED		(TC_ACT_VALUE_MAX + 1)
 
 /* Basic packet classifier frontend definitions. */
 
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 21f434f..855167b 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -279,7 +279,7 @@ struct tcf_result {
 		};
 		const struct tcf_proto *goto_tp;
 
-		/* used by the TC_ACT_REINSERT action */
+		/* used in the skb_tc_reinsert function */
 		struct {
 			bool		ingress;
 			struct gnet_stats_queue *qstats;
diff --git a/net/core/dev.c b/net/core/dev.c
index eb7fb6d..ed5eeb7 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4689,9 +4689,7 @@ 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_REINSERT:
-		/* this does not scrub the packet, and updates stats on error */
-		skb_tc_reinsert(skb, &cl_res);
+	case TC_ACT_CONSUMED:
 		return NULL;
 	default:
 		break;
diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c
index 58e7573d..8c1d736 100644
--- a/net/sched/act_mirred.c
+++ b/net/sched/act_mirred.c
@@ -277,7 +277,8 @@ static int tcf_mirred_act(struct sk_buff *skb, const struct tc_action *a,
 		if (use_reinsert) {
 			res->ingress = want_ingress;
 			res->qstats = this_cpu_ptr(m->common.cpu_qstats);
-			return TC_ACT_REINSERT;
+			skb_tc_reinsert(skb, res);
+			return TC_ACT_CONSUMED;
 		}
 	}
 
-- 
2.7.4