udp: intoduce udp_encap_needed static_key
Most machines dont use UDP encapsulation (L2TP)
Adds a static_key so that udp_queue_rcv_skb() doesnt have to perform a
test if L2TP never setup the encap_rcv on a socket.
Idea of this patch came after Simon Horman proposal to add a hook on TCP
as well.
If static_key is not yet enabled, the fast path does a single JMP .
When static_key is enabled, JMP destination is patched to reach the real
encap_type/encap_rcv logic, possibly adding cache misses.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Simon Horman <horms@verge.net.au>
Cc: dev@openvswitch.org
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/udp.h b/include/net/udp.h
index 5d606d9..9671f5f 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -267,4 +267,5 @@
extern int udp4_ufo_send_check(struct sk_buff *skb);
extern struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb,
netdev_features_t features);
+extern void udp_encap_enable(void);
#endif /* _UDP_H */
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index fe14105..ad1e0dd 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -107,6 +107,7 @@
#include <net/checksum.h>
#include <net/xfrm.h>
#include <trace/events/udp.h>
+#include <linux/static_key.h>
#include "udp_impl.h"
struct udp_table udp_table __read_mostly;
@@ -1379,6 +1380,14 @@
}
+static struct static_key udp_encap_needed __read_mostly;
+void udp_encap_enable(void)
+{
+ if (!static_key_enabled(&udp_encap_needed))
+ static_key_slow_inc(&udp_encap_needed);
+}
+EXPORT_SYMBOL(udp_encap_enable);
+
/* returns:
* -1: error
* 0: success
@@ -1400,7 +1409,7 @@
goto drop;
nf_reset(skb);
- if (up->encap_type) {
+ if (static_key_false(&udp_encap_needed) && up->encap_type) {
int (*encap_rcv)(struct sock *sk, struct sk_buff *skb);
/*
@@ -1760,6 +1769,7 @@
/* FALLTHROUGH */
case UDP_ENCAP_L2TPINUDP:
up->encap_type = val;
+ udp_encap_enable();
break;
default:
err = -ENOPROTOOPT;
diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index 89ff8c6..f6732b6 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -1424,6 +1424,7 @@
/* Mark socket as an encapsulation socket. See net/ipv4/udp.c */
udp_sk(sk)->encap_type = UDP_ENCAP_L2TPINUDP;
udp_sk(sk)->encap_rcv = l2tp_udp_encap_recv;
+ udp_encap_enable();
}
sk->sk_user_data = tunnel;
