Merge branch 'udp-tunnel-common'

Andy Zhou says:

====================
Refactor vxlan and l2tp to use new common UDP tunnel APIs

This patch series add a few more UDP tunnel APIs and refactoring current
UDP tunnel based protocols, vxlan and l2tp to make use of the new APIs.

The added APIs are setup_udp_tunnel_sock(), udp_tunnel_xmit_skb() and
udp_tunnel_sock_release(). Those implementation logics already exist in
current vxlan and l2tp implementation. Move them to common APIs to reduce
code duplications.

Also split udp_tunnel.c into net/ipv4/udp_tunnel.c and
net/ipv6/ip6_udp_tunnel.c to maintain proper IP protocol separation.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/vxlan.c

@@ -42,6 +42,7 @@
 #include <net/netns/generic.h>
 #include <net/vxlan.h>
 #include <net/protocol.h>
+#include <net/udp_tunnel.h>
 #if IS_ENABLED(CONFIG_IPV6)
 #include <net/ipv6.h>
 #include <net/addrconf.h>
@@ -1062,7 +1063,6 @@ void vxlan_sock_release(struct vxlan_sock *vs)
 
 	spin_lock(&vn->sock_lock);
 	hlist_del_rcu(&vs->hlist);
-	rcu_assign_sk_user_data(vs->sock->sk, NULL);
 	vxlan_notify_del_rx_port(vs);
 	spin_unlock(&vn->sock_lock);
 
@@ -1336,7 +1336,6 @@ static int arp_reduce(struct net_device *dev, struct sk_buff *skb)
 }
 
 #if IS_ENABLED(CONFIG_IPV6)
-
 static struct sk_buff *vxlan_na_create(struct sk_buff *request,
 	struct neighbour *n, bool isrouter)
 {
@@ -1570,13 +1569,6 @@ static bool route_shortcircuit(struct net_device *dev, struct sk_buff *skb)
 	return false;
 }
 
-static inline struct sk_buff *vxlan_handle_offloads(struct sk_buff *skb,
-						    bool udp_csum)
-{
-	int type = udp_csum ? SKB_GSO_UDP_TUNNEL_CSUM : SKB_GSO_UDP_TUNNEL;
-	return iptunnel_handle_offloads(skb, udp_csum, type);
-}
-
 #if IS_ENABLED(CONFIG_IPV6)
 static int vxlan6_xmit_skb(struct vxlan_sock *vs,
 			   struct dst_entry *dst, struct sk_buff *skb,
@@ -1585,13 +1577,12 @@ static int vxlan6_xmit_skb(struct vxlan_sock *vs,
 			   __be16 src_port, __be16 dst_port, __be32 vni,
 			   bool xnet)
 {
-	struct ipv6hdr *ip6h;
 	struct vxlanhdr *vxh;
-	struct udphdr *uh;
 	int min_headroom;
 	int err;
+	bool udp_sum = !udp_get_no_check6_tx(vs->sock->sk);
 
-	skb = vxlan_handle_offloads(skb, !udp_get_no_check6_tx(vs->sock->sk));
+	skb = udp_tunnel_handle_offloads(skb, udp_sum);
 	if (IS_ERR(skb))
 		return -EINVAL;
 
@@ -1619,38 +1610,8 @@ static int vxlan6_xmit_skb(struct vxlan_sock *vs,
 	vxh->vx_flags = htonl(VXLAN_FLAGS);
 	vxh->vx_vni = vni;
 
-	__skb_push(skb, sizeof(*uh));
-	skb_reset_transport_header(skb);
-	uh = udp_hdr(skb);
-
-	uh->dest = dst_port;
-	uh->source = src_port;
-
-	uh->len = htons(skb->len);
-
-	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
-	IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED |
-			      IPSKB_REROUTED);
-	skb_dst_set(skb, dst);
-
-	udp6_set_csum(udp_get_no_check6_tx(vs->sock->sk), skb,
-		      saddr, daddr, skb->len);
-
-	__skb_push(skb, sizeof(*ip6h));
-	skb_reset_network_header(skb);
-	ip6h		  = ipv6_hdr(skb);
-	ip6h->version	  = 6;
-	ip6h->priority	  = prio;
-	ip6h->flow_lbl[0] = 0;
-	ip6h->flow_lbl[1] = 0;
-	ip6h->flow_lbl[2] = 0;
-	ip6h->payload_len = htons(skb->len);
-	ip6h->nexthdr     = IPPROTO_UDP;
-	ip6h->hop_limit   = ttl;
-	ip6h->daddr	  = *daddr;
-	ip6h->saddr	  = *saddr;
-
-	ip6tunnel_xmit(skb, dev);
+	udp_tunnel6_xmit_skb(vs->sock, dst, skb, dev, saddr, daddr, prio,
+			     ttl, src_port, dst_port);
 	return 0;
 }
 #endif
@@ -1661,11 +1622,11 @@ int vxlan_xmit_skb(struct vxlan_sock *vs,
 		   __be16 src_port, __be16 dst_port, __be32 vni, bool xnet)
 {
 	struct vxlanhdr *vxh;
-	struct udphdr *uh;
 	int min_headroom;
 	int err;
+	bool udp_sum = !vs->sock->sk->sk_no_check_tx;
 
-	skb = vxlan_handle_offloads(skb, !vs->sock->sk->sk_no_check_tx);
+	skb = udp_tunnel_handle_offloads(skb, udp_sum);
 	if (IS_ERR(skb))
 		return -EINVAL;
 
@@ -1691,20 +1652,8 @@ int vxlan_xmit_skb(struct vxlan_sock *vs,
 	vxh->vx_flags = htonl(VXLAN_FLAGS);
 	vxh->vx_vni = vni;
 
-	__skb_push(skb, sizeof(*uh));
-	skb_reset_transport_header(skb);
-	uh = udp_hdr(skb);
-
-	uh->dest = dst_port;
-	uh->source = src_port;
-
-	uh->len = htons(skb->len);
-
-	udp_set_csum(vs->sock->sk->sk_no_check_tx, skb,
-		     src, dst, skb->len);
-
-	return iptunnel_xmit(vs->sock->sk, rt, skb, src, dst, IPPROTO_UDP,
-			     tos, ttl, df, xnet);
+	return udp_tunnel_xmit_skb(vs->sock, rt, skb, src, dst, tos,
+				   ttl, df, src_port, dst_port, xnet);
 }
 EXPORT_SYMBOL_GPL(vxlan_xmit_skb);
 
@@ -1829,11 +1778,11 @@ static void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,
 		tos = ip_tunnel_ecn_encap(tos, old_iph, skb);
 		ttl = ttl ? : ip4_dst_hoplimit(&rt->dst);
 
-		err = vxlan_xmit_skb(vxlan->vn_sock, rt, skb,
-				     fl4.saddr, dst->sin.sin_addr.s_addr,
-				     tos, ttl, df, src_port, dst_port,
-				     htonl(vni << 8),
-				     !net_eq(vxlan->net, dev_net(vxlan->dev)));
+		err = udp_tunnel_xmit_skb(vxlan->vn_sock->sock, rt, skb,
+					  fl4.saddr, dst->sin.sin_addr.s_addr,
+					  tos, ttl, df, src_port, dst_port,
+					  !net_eq(vxlan->net,
+						  dev_net(vxlan->dev)));
 
 		if (err < 0)
 			goto rt_tx_error;
@@ -2333,8 +2282,7 @@ static const struct ethtool_ops vxlan_ethtool_ops = {
 static void vxlan_del_work(struct work_struct *work)
 {
 	struct vxlan_sock *vs = container_of(work, struct vxlan_sock, del_work);
-
-	sk_release_kernel(vs->sock->sk);
+	udp_tunnel_sock_release(vs->sock);
 	kfree_rcu(vs, rcu);
 }
 
@@ -2367,11 +2315,6 @@ static struct socket *vxlan_create_sock(struct net *net, bool ipv6,
 	if (err < 0)
 		return ERR_PTR(err);
 
-	/* Disable multicast loopback */
-	inet_sk(sock->sk)->mc_loop = 0;
-
-	udp_set_convert_csum(sock->sk, true);
-
 	return sock;
 }
 
@@ -2383,9 +2326,9 @@ static struct vxlan_sock *vxlan_socket_create(struct net *net, __be16 port,
 	struct vxlan_net *vn = net_generic(net, vxlan_net_id);
 	struct vxlan_sock *vs;
 	struct socket *sock;
-	struct sock *sk;
 	unsigned int h;
 	bool ipv6 = !!(flags & VXLAN_F_IPV6);
+	struct udp_tunnel_sock_cfg tunnel_cfg;
 
 	vs = kzalloc(sizeof(*vs), GFP_KERNEL);
 	if (!vs)
@@ -2403,11 +2346,9 @@ static struct vxlan_sock *vxlan_socket_create(struct net *net, __be16 port,
 	}
 
 	vs->sock = sock;
-	sk = sock->sk;
 	atomic_set(&vs->refcnt, 1);
 	vs->rcv = rcv;
 	vs->data = data;
-	rcu_assign_sk_user_data(vs->sock->sk, vs);
 
 	/* Initialize the vxlan udp offloads structure */
 	vs->udp_offloads.port = port;
@@ -2420,14 +2361,12 @@ static struct vxlan_sock *vxlan_socket_create(struct net *net, __be16 port,
 	spin_unlock(&vn->sock_lock);
 
 	/* Mark socket as an encapsulation socket. */
-	udp_sk(sk)->encap_type = 1;
-	udp_sk(sk)->encap_rcv = vxlan_udp_encap_recv;
-#if IS_ENABLED(CONFIG_IPV6)
-	if (ipv6)
-		ipv6_stub->udpv6_encap_enable();
-	else
-#endif
-		udp_encap_enable();
+	tunnel_cfg.sk_user_data = vs;
+	tunnel_cfg.encap_type = 1;
+	tunnel_cfg.encap_rcv = vxlan_udp_encap_recv;
+	tunnel_cfg.encap_destroy = NULL;
+
+	setup_udp_tunnel_sock(net, sock, &tunnel_cfg);
 
 	return vs;
 }

include/net/udp_tunnel.h

 #ifndef __NET_UDP_TUNNEL_H
 #define __NET_UDP_TUNNEL_H
 
+#include <net/ip_tunnels.h>
+#include <net/udp.h>
+
+#if IS_ENABLED(CONFIG_IPV6)
+#include <net/ipv6.h>
+#include <net/addrconf.h>
+#endif
+
 struct udp_port_cfg {
 	u8			family;
 
@@ -26,7 +34,80 @@ struct udp_port_cfg {
 				use_udp6_rx_checksums:1;
 };
 
-int udp_sock_create(struct net *net, struct udp_port_cfg *cfg,
-		    struct socket **sockp);
+int udp_sock_create4(struct net *net, struct udp_port_cfg *cfg,
+		     struct socket **sockp);
+
+#if IS_ENABLED(CONFIG_IPV6)
+int udp_sock_create6(struct net *net, struct udp_port_cfg *cfg,
+		     struct socket **sockp);
+#else
+static inline int udp_sock_create6(struct net *net, struct udp_port_cfg *cfg,
+				   struct socket **sockp)
+{
+	return 0;
+}
+#endif
+
+static inline int udp_sock_create(struct net *net,
+				  struct udp_port_cfg *cfg,
+				  struct socket **sockp)
+{
+	if (cfg->family == AF_INET)
+		return udp_sock_create4(net, cfg, sockp);
+
+	if (cfg->family == AF_INET6)
+		return udp_sock_create6(net, cfg, sockp);
+
+	return -EPFNOSUPPORT;
+}
+
+typedef int (*udp_tunnel_encap_rcv_t)(struct sock *sk, struct sk_buff *skb);
+typedef void (*udp_tunnel_encap_destroy_t)(struct sock *sk);
+
+struct udp_tunnel_sock_cfg {
+	void *sk_user_data;     /* user data used by encap_rcv call back */
+	/* Used for setting up udp_sock fields, see udp.h for details */
+	__u8  encap_type;
+	udp_tunnel_encap_rcv_t encap_rcv;
+	udp_tunnel_encap_destroy_t encap_destroy;
+};
+
+/* Setup the given (UDP) sock to receive UDP encapsulated packets */
+void setup_udp_tunnel_sock(struct net *net, struct socket *sock,
+			   struct udp_tunnel_sock_cfg *sock_cfg);
+
+/* Transmit the skb using UDP encapsulation. */
+int udp_tunnel_xmit_skb(struct socket *sock, struct rtable *rt,
+			struct sk_buff *skb, __be32 src, __be32 dst,
+			__u8 tos, __u8 ttl, __be16 df, __be16 src_port,
+			__be16 dst_port, bool xnet);
+
+#if IS_ENABLED(CONFIG_IPV6)
+int udp_tunnel6_xmit_skb(struct socket *sock, struct dst_entry *dst,
+			 struct sk_buff *skb, struct net_device *dev,
+			 struct in6_addr *saddr, struct in6_addr *daddr,
+			 __u8 prio, __u8 ttl, __be16 src_port,
+			 __be16 dst_port);
+#endif
+
+void udp_tunnel_sock_release(struct socket *sock);
+
+static inline struct sk_buff *udp_tunnel_handle_offloads(struct sk_buff *skb,
+							 bool udp_csum)
+{
+	int type = udp_csum ? SKB_GSO_UDP_TUNNEL_CSUM : SKB_GSO_UDP_TUNNEL;
+
+	return iptunnel_handle_offloads(skb, udp_csum, type);
+}
+
+static inline void udp_tunnel_encap_enable(struct socket *sock)
+{
+#if IS_ENABLED(CONFIG_IPV6)
+	if (sock->sk->sk_family == PF_INET6)
+		ipv6_stub->udpv6_encap_enable();
+	else
+#endif
+		udp_encap_enable();
+}
 
 #endif

net/ipv4/udp_tunnel.c

@@ -8,83 +8,40 @@
 #include <net/udp_tunnel.h>
 #include <net/net_namespace.h>
 
-int udp_sock_create(struct net *net, struct udp_port_cfg *cfg,
-		    struct socket **sockp)
+int udp_sock_create4(struct net *net, struct udp_port_cfg *cfg,
+		     struct socket **sockp)
 {
-	int err = -EINVAL;
+	int err;
 	struct socket *sock = NULL;
+	struct sockaddr_in udp_addr;
 
-#if IS_ENABLED(CONFIG_IPV6)
-	if (cfg->family == AF_INET6) {
-		struct sockaddr_in6 udp6_addr;
+	err = sock_create_kern(AF_INET, SOCK_DGRAM, 0, &sock);
+	if (err < 0)
+		goto error;
 
-		err = sock_create_kern(AF_INET6, SOCK_DGRAM, 0, &sock);
-		if (err < 0)
-			goto error;
-
-		sk_change_net(sock->sk, net);
-
-		udp6_addr.sin6_family = AF_INET6;
-		memcpy(&udp6_addr.sin6_addr, &cfg->local_ip6,
-		       sizeof(udp6_addr.sin6_addr));
-		udp6_addr.sin6_port = cfg->local_udp_port;
-		err = kernel_bind(sock, (struct sockaddr *)&udp6_addr,
-				  sizeof(udp6_addr));
-		if (err < 0)
-			goto error;
-
-		if (cfg->peer_udp_port) {
-			udp6_addr.sin6_family = AF_INET6;
-			memcpy(&udp6_addr.sin6_addr, &cfg->peer_ip6,
-			       sizeof(udp6_addr.sin6_addr));
-			udp6_addr.sin6_port = cfg->peer_udp_port;
-			err = kernel_connect(sock,
-					     (struct sockaddr *)&udp6_addr,
-					     sizeof(udp6_addr), 0);
-		}
-		if (err < 0)
-			goto error;
+	sk_change_net(sock->sk, net);
 
-		udp_set_no_check6_tx(sock->sk, !cfg->use_udp6_tx_checksums);
-		udp_set_no_check6_rx(sock->sk, !cfg->use_udp6_rx_checksums);
-	} else
-#endif
-	if (cfg->family == AF_INET) {
-		struct sockaddr_in udp_addr;
-
-		err = sock_create_kern(AF_INET, SOCK_DGRAM, 0, &sock);
-		if (err < 0)
-			goto error;
-
-		sk_change_net(sock->sk, net);
+	udp_addr.sin_family = AF_INET;
+	udp_addr.sin_addr = cfg->local_ip;
+	udp_addr.sin_port = cfg->local_udp_port;
+	err = kernel_bind(sock, (struct sockaddr *)&udp_addr,
+			  sizeof(udp_addr));
+	if (err < 0)
+		goto error;
 
+	if (cfg->peer_udp_port) {
 		udp_addr.sin_family = AF_INET;
-		udp_addr.sin_addr = cfg->local_ip;
-		udp_addr.sin_port = cfg->local_udp_port;
-		err = kernel_bind(sock, (struct sockaddr *)&udp_addr,
-				  sizeof(udp_addr));
+		udp_addr.sin_addr = cfg->peer_ip;
+		udp_addr.sin_port = cfg->peer_udp_port;
+		err = kernel_connect(sock, (struct sockaddr *)&udp_addr,
+				     sizeof(udp_addr), 0);
 		if (err < 0)
 			goto error;
-
-		if (cfg->peer_udp_port) {
-			udp_addr.sin_family = AF_INET;
-			udp_addr.sin_addr = cfg->peer_ip;
-			udp_addr.sin_port = cfg->peer_udp_port;
-			err = kernel_connect(sock,
-					     (struct sockaddr *)&udp_addr,
-					     sizeof(udp_addr), 0);
-			if (err < 0)
-				goto error;
-		}
-
-		sock->sk->sk_no_check_tx = !cfg->use_udp_checksums;
-	} else {
-		return -EPFNOSUPPORT;
 	}
 
+	sock->sk->sk_no_check_tx = !cfg->use_udp_checksums;
 
 	*sockp = sock;
-
 	return 0;
 
 error:
@@ -95,6 +52,57 @@ int udp_sock_create(struct net *net, struct udp_port_cfg *cfg,
 	*sockp = NULL;
 	return err;
 }
-EXPORT_SYMBOL(udp_sock_create);
+EXPORT_SYMBOL(udp_sock_create4);
+
+void setup_udp_tunnel_sock(struct net *net, struct socket *sock,
+			   struct udp_tunnel_sock_cfg *cfg)
+{
+	struct sock *sk = sock->sk;
+
+	/* Disable multicast loopback */
+	inet_sk(sk)->mc_loop = 0;
+
+	/* Enable CHECKSUM_UNNECESSARY to CHECKSUM_COMPLETE conversion */
+	udp_set_convert_csum(sk, true);
+
+	rcu_assign_sk_user_data(sk, cfg->sk_user_data);
+
+	udp_sk(sk)->encap_type = cfg->encap_type;
+	udp_sk(sk)->encap_rcv = cfg->encap_rcv;
+	udp_sk(sk)->encap_destroy = cfg->encap_destroy;
+
+	udp_tunnel_encap_enable(sock);
+}
+EXPORT_SYMBOL_GPL(setup_udp_tunnel_sock);
+
+int udp_tunnel_xmit_skb(struct socket *sock, struct rtable *rt,
+			struct sk_buff *skb, __be32 src, __be32 dst,
+			__u8 tos, __u8 ttl, __be16 df, __be16 src_port,
+			__be16 dst_port, bool xnet)
+{
+	struct udphdr *uh;
+
+	__skb_push(skb, sizeof(*uh));
+	skb_reset_transport_header(skb);
+	uh = udp_hdr(skb);
+
+	uh->dest = dst_port;
+	uh->source = src_port;
+	uh->len = htons(skb->len);
+
+	udp_set_csum(sock->sk->sk_no_check_tx, skb, src, dst, skb->len);
+
+	return iptunnel_xmit(sock->sk, rt, skb, src, dst, IPPROTO_UDP,
+			     tos, ttl, df, xnet);
+}
+EXPORT_SYMBOL_GPL(udp_tunnel_xmit_skb);
+
+void udp_tunnel_sock_release(struct socket *sock)
+{
+	rcu_assign_sk_user_data(sock->sk, NULL);
+	kernel_sock_shutdown(sock, SHUT_RDWR);
+	sk_release_kernel(sock->sk);
+}
+EXPORT_SYMBOL_GPL(udp_tunnel_sock_release);
 
 MODULE_LICENSE("GPL");

net/ipv6/Makefile

@@ -35,6 +35,7 @@ obj-$(CONFIG_INET6_XFRM_MODE_ROUTEOPTIMIZATION) += xfrm6_mode_ro.o
 obj-$(CONFIG_INET6_XFRM_MODE_BEET) += xfrm6_mode_beet.o
 obj-$(CONFIG_IPV6_MIP6) += mip6.o
 obj-$(CONFIG_NETFILTER)	+= netfilter/
+obj-$(CONFIG_NET_UDP_TUNNEL) += ip6_udp_tunnel.o
 
 obj-$(CONFIG_IPV6_VTI) += ip6_vti.o
 obj-$(CONFIG_IPV6_SIT) += sit.o

net/ipv6/ip6_udp_tunnel.c

+#include <linux/module.h>
+#include <linux/errno.h>
+#include <linux/socket.h>
+#include <linux/udp.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/in6.h>
+#include <net/udp.h>
+#include <net/udp_tunnel.h>
+#include <net/net_namespace.h>
+#include <net/netns/generic.h>
+#include <net/ip6_tunnel.h>
+#include <net/ip6_checksum.h>
+
+int udp_sock_create6(struct net *net, struct udp_port_cfg *cfg,
+		     struct socket **sockp)
+{
+	struct sockaddr_in6 udp6_addr;
+	int err;
+	struct socket *sock = NULL;
+
+	err = sock_create_kern(AF_INET6, SOCK_DGRAM, 0, &sock);
+	if (err < 0)
+		goto error;
+
+	sk_change_net(sock->sk, net);
+
+	udp6_addr.sin6_family = AF_INET6;
+	memcpy(&udp6_addr.sin6_addr, &cfg->local_ip6,
+	       sizeof(udp6_addr.sin6_addr));
+	udp6_addr.sin6_port = cfg->local_udp_port;
+	err = kernel_bind(sock, (struct sockaddr *)&udp6_addr,
+			  sizeof(udp6_addr));
+	if (err < 0)
+		goto error;
+
+	if (cfg->peer_udp_port) {
+		udp6_addr.sin6_family = AF_INET6;
+		memcpy(&udp6_addr.sin6_addr, &cfg->peer_ip6,
+		       sizeof(udp6_addr.sin6_addr));
+		udp6_addr.sin6_port = cfg->peer_udp_port;
+		err = kernel_connect(sock,
+				     (struct sockaddr *)&udp6_addr,
+				     sizeof(udp6_addr), 0);
+	}
+	if (err < 0)
+		goto error;
+
+	udp_set_no_check6_tx(sock->sk, !cfg->use_udp6_tx_checksums);
+	udp_set_no_check6_rx(sock->sk, !cfg->use_udp6_rx_checksums);
+
+	*sockp = sock;
+	return 0;
+
+error:
+	if (sock) {
+		kernel_sock_shutdown(sock, SHUT_RDWR);
+		sk_release_kernel(sock->sk);
+	}
+	*sockp = NULL;
+	return err;
+}
+EXPORT_SYMBOL_GPL(udp_sock_create6);
+
+int udp_tunnel6_xmit_skb(struct socket *sock, struct dst_entry *dst,
+			 struct sk_buff *skb, struct net_device *dev,
+			 struct in6_addr *saddr, struct in6_addr *daddr,
+			 __u8 prio, __u8 ttl, __be16 src_port, __be16 dst_port)
+{
+	struct udphdr *uh;
+	struct ipv6hdr *ip6h;
+	struct sock *sk = sock->sk;
+
+	__skb_push(skb, sizeof(*uh));
+	skb_reset_transport_header(skb);
+	uh = udp_hdr(skb);
+
+	uh->dest = dst_port;
+	uh->source = src_port;
+
+	uh->len = htons(skb->len);
+	uh->check = 0;
+
+	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
+	IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED
+			    | IPSKB_REROUTED);
+	skb_dst_set(skb, dst);
+
+	udp6_set_csum(udp_get_no_check6_tx(sk), skb, &inet6_sk(sk)->saddr,
+		      &sk->sk_v6_daddr, skb->len);
+
+	__skb_push(skb, sizeof(*ip6h));
+	skb_reset_network_header(skb);
+	ip6h		  = ipv6_hdr(skb);
+	ip6_flow_hdr(ip6h, prio, htonl(0));
+	ip6h->payload_len = htons(skb->len);
+	ip6h->nexthdr     = IPPROTO_UDP;
+	ip6h->hop_limit   = ttl;
+	ip6h->daddr	  = *daddr;
+	ip6h->saddr	  = *saddr;
+
+	ip6tunnel_xmit(skb, dev);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(udp_tunnel6_xmit_skb);

net/l2tp/l2tp_core.c

@@ -1392,8 +1392,6 @@ static int l2tp_tunnel_sock_create(struct net *net,
 		if (err < 0)
 			goto out;
 
-		udp_set_convert_csum(sock->sk, true);
-
 		break;
 
 	case L2TP_ENCAPTYPE_IP:
@@ -1584,19 +1582,17 @@ 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 */
 	tunnel->encap = encap;
 	if (encap == L2TP_ENCAPTYPE_UDP) {
-		/* 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_sk(sk)->encap_destroy = l2tp_udp_encap_destroy;
-#if IS_ENABLED(CONFIG_IPV6)
-		if (sk->sk_family == PF_INET6 && !tunnel->v4mapped)
-			udpv6_encap_enable();
-		else
-#endif
-		udp_encap_enable();
-	}
+		struct udp_tunnel_sock_cfg udp_cfg;
+
+		udp_cfg.sk_user_data = tunnel;
+		udp_cfg.encap_type = UDP_ENCAP_L2TPINUDP;
+		udp_cfg.encap_rcv = l2tp_udp_encap_recv;
+		udp_cfg.encap_destroy = l2tp_udp_encap_destroy;
 
-	sk->sk_user_data = tunnel;
+		setup_udp_tunnel_sock(net, sock, &udp_cfg);
+	} else {
+		sk->sk_user_data = tunnel;
+	}
 
 	/* Hook on the tunnel socket destructor so that we can cleanup
 	 * if the tunnel socket goes away.