net: use jump label patching for ingress qdisc in __netif_receive_skb_core

Even if we make use of classifier and actions from the egress
path, we're going into handle_ing() executing additional code
on a per-packet cost for ingress qdisc, just to realize that
nothing is attached on ingress.

Instead, this can just be blinded out as a no-op entirely with
the use of a static key. On input fast-path, we already make
use of static keys in various places, e.g. skb time stamping,
in RPS, etc. It makes sense to not waste time when we're assured
that no ingress qdisc is attached anywhere.

Enabling/disabling of that code path is being done via two
helpers, namely net_{inc,dec}_ingress_queue(), that are being
invoked under RTNL mutex when a ingress qdisc is being either
initialized or destructed.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
index 5db76a32fcaba3d9656fa5de6d077780d1d07e46..2da5d1081ad990b57a07715ea0751ae10a80ac54 100644 (file)
--- a/include/linux/rtnetlink.h
+++ b/include/linux/rtnetlink.h
@@ -77,7 +77,20 @@ static inline struct netdev_queue *dev_ingress_queue(struct net_device *dev)
        return rtnl_dereference(dev->ingress_queue);
 }
 
-extern struct netdev_queue *dev_ingress_queue_create(struct net_device *dev);
+struct netdev_queue *dev_ingress_queue_create(struct net_device *dev);
+
+#ifdef CONFIG_NET_CLS_ACT
+void net_inc_ingress_queue(void);
+void net_dec_ingress_queue(void);
+#else
+static inline void net_inc_ingress_queue(void)
+{
+}
+
+static inline void net_dec_ingress_queue(void)
+{
+}
+#endif
 
 extern void rtnetlink_init(void);
 extern void __rtnl_unlock(void);

diff --git a/net/core/dev.c b/net/core/dev.c
index b2775f06c7102a00afbd170daae05468d660b5b1..af4a1b0adc104f626c65507b19bd99c6dc3dd0eb 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1630,6 +1630,22 @@ int call_netdevice_notifiers(unsigned long val, struct net_device *dev)
 }
 EXPORT_SYMBOL(call_netdevice_notifiers);
 
+#ifdef CONFIG_NET_CLS_ACT
+static struct static_key ingress_needed __read_mostly;
+
+void net_inc_ingress_queue(void)
+{
+       static_key_slow_inc(&ingress_needed);
+}
+EXPORT_SYMBOL_GPL(net_inc_ingress_queue);
+
+void net_dec_ingress_queue(void)
+{
+       static_key_slow_dec(&ingress_needed);
+}
+EXPORT_SYMBOL_GPL(net_dec_ingress_queue);
+#endif
+
 static struct static_key netstamp_needed __read_mostly;
 #ifdef HAVE_JUMP_LABEL
 /* We are not allowed to call static_key_slow_dec() from irq context
@@ -3547,7 +3563,7 @@ static inline struct sk_buff *handle_ing(struct sk_buff *skb,
        struct netdev_queue *rxq = rcu_dereference(skb->dev->ingress_queue);
 
        if (!rxq || rcu_access_pointer(rxq->qdisc) == &noop_qdisc)
-               goto out;
+               return skb;
 
        if (*pt_prev) {
                *ret = deliver_skb(skb, *pt_prev, orig_dev);
@@ -3561,8 +3577,6 @@ static inline struct sk_buff *handle_ing(struct sk_buff *skb,
                return NULL;
        }
 
-out:
-       skb->tc_verd = 0;
        return skb;
 }
 #endif
@@ -3698,12 +3712,15 @@ another_round:
 
 skip_taps:
 #ifdef CONFIG_NET_CLS_ACT
-       skb = handle_ing(skb, &pt_prev, &ret, orig_dev);
-       if (!skb)
-               goto unlock;
+       if (static_key_false(&ingress_needed)) {
+               skb = handle_ing(skb, &pt_prev, &ret, orig_dev);
+               if (!skb)
+                       goto unlock;
+       }
+
+       skb->tc_verd = 0;
 ncls:
 #endif
-
        if (pfmemalloc && !skb_pfmemalloc_protocol(skb))
                goto drop;
 

diff --git a/net/sched/sch_ingress.c b/net/sched/sch_ingress.c
index eb5b8445fef989c1f331fa1485fa39c649181a82..4cdbfb85686a7ee55d71d0a7c1ea5cdd7e789a22 100644 (file)
--- a/net/sched/sch_ingress.c
+++ b/net/sched/sch_ingress.c
@@ -88,11 +88,19 @@ static int ingress_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 
 /* ------------------------------------------------------------- */
 
+static int ingress_init(struct Qdisc *sch, struct nlattr *opt)
+{
+       net_inc_ingress_queue();
+
+       return 0;
+}
+
 static void ingress_destroy(struct Qdisc *sch)
 {
        struct ingress_qdisc_data *p = qdisc_priv(sch);
 
        tcf_destroy_chain(&p->filter_list);
+       net_dec_ingress_queue();
 }
 
 static int ingress_dump(struct Qdisc *sch, struct sk_buff *skb)
@@ -124,6 +132,7 @@ static struct Qdisc_ops ingress_qdisc_ops __read_mostly = {
        .id             =       "ingress",
        .priv_size      =       sizeof(struct ingress_qdisc_data),
        .enqueue        =       ingress_enqueue,
+       .init           =       ingress_init,
        .destroy        =       ingress_destroy,
        .dump           =       ingress_dump,
        .owner          =       THIS_MODULE,