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Commit 447167bf authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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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: default avatarEric Dumazet <eric.dumazet@gmail.com>
Cc: Simon Horman <horms@verge.net.au>
Cc: dev@openvswitch.org
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 77577bf9

include/net/udp.h

+1 −0
Original line number Diff line number Diff line
@@ -267,4 +267,5 @@ extern void udp_init(void); 
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 */

net/ipv4/udp.c

+11 −1
Original line number Diff line number Diff line
@@ -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 int __udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb) 


}



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 @@ int udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb) 
		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 @@ int udp_lib_setsockopt(struct sock *sk, int level, int optname, 
			/* FALLTHROUGH */

		case UDP_ENCAP_L2TPINUDP:

			up->encap_type = val;

			udp_encap_enable();

			break;

		default:

			err = -ENOPROTOOPT;

net/l2tp/l2tp_core.c

+1 −0
Original line number Diff line number Diff line
@@ -1424,6 +1424,7 @@ int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id, u32 
		/* 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;