udp: lockless UDP_ENCAP_L2TPINUDP / UDP_GRO

Move udp->encap_enabled to udp->udp_flags.

Add udp_test_and_set_bit() helper to allow lockless
udp_tunnel_encap_enable() implementation.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

include/linux/udp.h

@@ -39,6 +39,7 @@ enum {
 	UDP_FLAGS_GRO_ENABLED,	/* Request GRO aggregation */
 	UDP_FLAGS_ACCEPT_FRAGLIST,
 	UDP_FLAGS_ACCEPT_L4,
+	UDP_FLAGS_ENCAP_ENABLED, /* This socket enabled encap */
 };
 
 struct udp_sock {
@@ -52,11 +53,7 @@ struct udp_sock {
 
 	int		 pending;	/* Any pending frames ? */
 	__u8		 encap_type;	/* Is this an Encapsulation socket? */
-	unsigned char	 encap_enabled:1; /* This socket enabled encap
-					   * processing; UDP tunnels and
-					   * different encapsulation layer set
-					   * this
-					   */
+
 /* indicator bits used by pcflag: */
 #define UDPLITE_BIT      0x1  		/* set by udplite proto init function */
 #define UDPLITE_SEND_CC  0x2  		/* set via udplite setsockopt         */
@@ -104,6 +101,8 @@ struct udp_sock {
 	test_bit(UDP_FLAGS_##nr, &udp_sk(sk)->udp_flags)
 #define udp_set_bit(nr, sk)			\
 	set_bit(UDP_FLAGS_##nr, &udp_sk(sk)->udp_flags)
+#define udp_test_and_set_bit(nr, sk)		\
+	test_and_set_bit(UDP_FLAGS_##nr, &udp_sk(sk)->udp_flags)
 #define udp_clear_bit(nr, sk)			\
 	clear_bit(UDP_FLAGS_##nr, &udp_sk(sk)->udp_flags)
 #define udp_assign_bit(nr, sk, val)		\

include/net/udp_tunnel.h

@@ -174,16 +174,13 @@ static inline int udp_tunnel_handle_offloads(struct sk_buff *skb, bool udp_csum)
 }
 #endif
 
-static inline void udp_tunnel_encap_enable(struct socket *sock)
+static inline void udp_tunnel_encap_enable(struct sock *sk)
 {
-	struct udp_sock *up = udp_sk(sock->sk);
-
-	if (up->encap_enabled)
+	if (udp_test_and_set_bit(ENCAP_ENABLED, sk))
 		return;
 
-	up->encap_enabled = 1;
 #if IS_ENABLED(CONFIG_IPV6)
-	if (sock->sk->sk_family == PF_INET6)
+	if (READ_ONCE(sk->sk_family) == PF_INET6)
 		ipv6_stub->udpv6_encap_enable();
 #endif
 	udp_encap_enable();

net/ipv4/udp.c

@@ -2618,7 +2618,7 @@ void udp_destroy_sock(struct sock *sk)
 			if (encap_destroy)
 				encap_destroy(sk);
 		}
-		if (up->encap_enabled)
+		if (udp_test_bit(ENCAP_ENABLED, sk))
 			static_branch_dec(&udp_encap_needed_key);
 	}
 }
@@ -2685,9 +2685,7 @@ int udp_lib_setsockopt(struct sock *sk, int level, int optname,
 			fallthrough;
 		case UDP_ENCAP_L2TPINUDP:
 			up->encap_type = val;
-			lock_sock(sk);
-			udp_tunnel_encap_enable(sk->sk_socket);
-			release_sock(sk);
+			udp_tunnel_encap_enable(sk);
 			break;
 		default:
 			err = -ENOPROTOOPT;
@@ -2710,14 +2708,12 @@ int udp_lib_setsockopt(struct sock *sk, int level, int optname,
 		break;
 
 	case UDP_GRO:
-		lock_sock(sk);
 
 		/* when enabling GRO, accept the related GSO packet type */
 		if (valbool)
-			udp_tunnel_encap_enable(sk->sk_socket);
+			udp_tunnel_encap_enable(sk);
 		udp_assign_bit(GRO_ENABLED, sk, valbool);
 		udp_assign_bit(ACCEPT_L4, sk, valbool);
-		release_sock(sk);
 		break;
 
 	/*

net/ipv4/udp_tunnel_core.c

@@ -78,7 +78,7 @@ void setup_udp_tunnel_sock(struct net *net, struct socket *sock,
 	udp_sk(sk)->gro_receive = cfg->gro_receive;
 	udp_sk(sk)->gro_complete = cfg->gro_complete;
 
-	udp_tunnel_encap_enable(sock);
+	udp_tunnel_encap_enable(sk);
 }
 EXPORT_SYMBOL_GPL(setup_udp_tunnel_sock);
 

net/ipv6/udp.c

@@ -1670,7 +1670,7 @@ void udpv6_destroy_sock(struct sock *sk)
 			if (encap_destroy)
 				encap_destroy(sk);
 		}
-		if (up->encap_enabled) {
+		if (udp_test_bit(ENCAP_ENABLED, sk)) {
 			static_branch_dec(&udpv6_encap_needed_key);
 			udp_encap_disable();
 		}