compat: support 3.16

6 files changed, 573 insertions, 109 deletions

diff --git a/src/compat/Kbuild.include b/src/compat/Kbuild.include
index ceffb84..ebd5aaf 100644
--- a/src/compat/Kbuild.include
+++ b/src/compat/Kbuild.include
@@ -17,3 +17,8 @@ endif
 ifeq ($(wildcard $(srctree)/arch/x86/include/asm/fpu/api.h),)
 ccflags-y += -I$(src)/compat/i387/include
 endif
+
+ifeq ($(wildcard $(srctree)/include/net/udp_tunnel.h),)
+ccflags-y += -I$(src)/compat/udp_tunnel/include
+wireguard-y += compat/udp_tunnel/udp_tunnel.o
+endif
diff --git a/src/compat/compat.h b/src/compat/compat.h
index 4e6010f..cf344f7 100644
--- a/src/compat/compat.h
+++ b/src/compat/compat.h
@@ -7,8 +7,8 @@
 #include <linux/version.h>
 #include <linux/types.h>
 
-#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 18, 0)
-#error "WireGuard requires Linux >= 3.18"
+#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 16, 0)
+#error "WireGuard requires Linux >= 3.16"
 #endif
 
 /* These conditionals can't be enforced by an out of tree module very easily,
@@ -20,6 +20,15 @@
 #error "WireGuard requires CONFIG_IP6_NF_IPTABLES when using CONFIG_IPV6."
 #endif
 
+#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 18, 0)
+#define headers_start data
+#define headers_end data
+#endif
+
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 17, 0)
+#include "udp_tunnel/udp_tunnel_partial_compat.h"
+#endif
+
 #if LINUX_VERSION_CODE < KERNEL_VERSION(4, 3, 0) && !defined(DEBUG) && defined(net_dbg_ratelimited)
 #undef net_dbg_ratelimited
 #define net_dbg_ratelimited(fmt, ...) do { if (0) no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__); } while (0)
@@ -29,120 +38,17 @@
 #define RCU_LOCKDEP_WARN(cond, message) rcu_lockdep_assert(!(cond), message)
 #endif
 
-#if (LINUX_VERSION_CODE > KERNEL_VERSION(3, 19, 0) && LINUX_VERSION_CODE < KERNEL_VERSION(3, 19, 6)) || LINUX_VERSION_CODE < KERNEL_VERSION(3, 18, 12)
+#if (LINUX_VERSION_CODE > KERNEL_VERSION(3, 19, 0) && LINUX_VERSION_CODE < KERNEL_VERSION(3, 19, 6)) || (LINUX_VERSION_CODE < KERNEL_VERSION(3, 18, 12) && LINUX_VERSION_CODE > KERNEL_VERSION(3, 17, 0)) || LINUX_VERSION_CODE < KERNEL_VERSION(3, 16, 8)
 #define dev_recursion_level() 0
 #endif
 
-#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 0, 0)
-#include <linux/if.h>
-#include <net/udp_tunnel.h>
-#define udp_tunnel_xmit_skb(a, b, c, d, e, f, g, h, i, j, k, l) do { struct net_device *dev__ = (c)->dev; int ret__; ret__ = udp_tunnel_xmit_skb((b)->sk_socket, a, c, d, e, f, g, h, i, j, k); iptunnel_xmit_stats(ret__, &dev__->stats, dev__->tstats); } while (0)
-#if IS_ENABLED(CONFIG_IPV6)
-#define udp_tunnel6_xmit_skb(a, b, c, d, e, f, g, h, i, j, k, l) udp_tunnel6_xmit_skb((b)->sk_socket, a, c, d, e, f, g, h, j, k);
-#endif
-#elif LINUX_VERSION_CODE < KERNEL_VERSION(4, 1, 0)
-#include <linux/if.h>
-#include <net/udp_tunnel.h>
-static inline void fake_destructor(struct sk_buff *skb)
-{
-}
-#define udp_tunnel_xmit_skb(a, b, c, d, e, f, g, h, i, j, k, l) do { struct net_device *dev__ = (c)->dev; int ret__; (c)->destructor = fake_destructor; (c)->sk = (b); ret__ = udp_tunnel_xmit_skb(a, c, d, e, f, g, h, i, j, k, l); iptunnel_xmit_stats(ret__, &dev__->stats, dev__->tstats); } while (0)
-#if IS_ENABLED(CONFIG_IPV6)
-#define udp_tunnel6_xmit_skb(a, b, c, d, e, f, g, h, i, j, k, l) do { (c)->destructor = fake_destructor; (c)->sk = (b); udp_tunnel6_xmit_skb(a, c, d, e, f, g, h, j, k, l); } while(0)
-#endif
-#else
-
-#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 5, 0)
-#include <linux/if.h>
-#include <net/udp_tunnel.h>
-#define udp_tunnel_xmit_skb(a, b, c, d, e, f, g, h, i, j, k, l) do { struct net_device *dev__ = (c)->dev; int ret__ = udp_tunnel_xmit_skb(a, b, c, d, e, f, g, h, i, j, k, l);  iptunnel_xmit_stats(ret__, &dev__->stats, dev__->tstats); } while (0)
-#endif
-
-#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 6, 0) && IS_ENABLED(CONFIG_IPV6)
-#include <linux/if.h>
-#include <net/udp_tunnel.h>
-#define udp_tunnel6_xmit_skb(a, b, c, d, e, f, g, h, i, j, k, l) udp_tunnel6_xmit_skb(a, b, c, d, e, f, g, h, j, k, l)
-#endif
-
-#endif
-
-#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 3, 0)
-#include <linux/if.h>
-#include <net/udp_tunnel.h>
-struct udp_port_cfg_new {
-	u8 family;
-	union {
-		struct in_addr local_ip;
-#if IS_ENABLED(CONFIG_IPV6)
-		struct in6_addr local_ip6;
-#endif
-	};
-	union {
-		struct in_addr peer_ip;
-#if IS_ENABLED(CONFIG_IPV6)
-		struct in6_addr peer_ip6;
-#endif
-	};
-	__be16 local_udp_port;
-	__be16 peer_udp_port;
-	unsigned int use_udp_checksums:1, use_udp6_tx_checksums:1, use_udp6_rx_checksums:1, ipv6_v6only:1;
-};
-static inline int __maybe_unused udp_sock_create_new(struct net *net, struct udp_port_cfg_new *cfg, struct socket **sockp)
-{
-	struct udp_port_cfg old_cfg = {
-		.family = cfg->family,
-		.local_ip = cfg->local_ip,
-#if IS_ENABLED(CONFIG_IPV6)
-		.local_ip6 = cfg->local_ip6,
-#endif
-		.peer_ip = cfg->peer_ip,
-#if IS_ENABLED(CONFIG_IPV6)
-		.peer_ip6 = cfg->peer_ip6,
-#endif
-		.local_udp_port = cfg->local_udp_port,
-		.peer_udp_port = cfg->peer_udp_port,
-		.use_udp_checksums = cfg->use_udp_checksums,
-		.use_udp6_tx_checksums = cfg->use_udp6_tx_checksums,
-		.use_udp6_rx_checksums = cfg->use_udp6_rx_checksums
-	};
-	if (cfg->family == AF_INET)
-		return udp_sock_create4(net, &old_cfg, sockp);
-
-#if IS_ENABLED(CONFIG_IPV6)
-	if (cfg->family == AF_INET6) {
-		int ret;
-		int old_bindv6only;
-		struct net *nobns;
-
-		if (cfg->ipv6_v6only) {
-#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 2, 0)
-			nobns = &init_net;
-#else
-			nobns = net;
-#endif
-			/* Since udp_port_cfg only learned of ipv6_v6only in 4.3, we do this horrible
-			 * hack here and set the sysctl variable temporarily to something that will
-			 * set the right option for us in sock_create. It's super racey! */
-			old_bindv6only = nobns->ipv6.sysctl.bindv6only;
-			nobns->ipv6.sysctl.bindv6only = 1;
-		}
-		ret = udp_sock_create6(net, &old_cfg, sockp);
-		if (cfg->ipv6_v6only)
-			nobns->ipv6.sysctl.bindv6only = old_bindv6only;
-		return ret;
-	}
-#endif
-	return -EPFNOSUPPORT;
-}
-#define udp_port_cfg udp_port_cfg_new
-#define udp_sock_create(a, b, c) udp_sock_create_new(a, b, c)
-#endif
-
 #if LINUX_VERSION_CODE < KERNEL_VERSION(4, 3, 0)
 #define ipv6_dst_lookup(a, b, c, d) ipv6_dst_lookup(b, c, d)
 #endif
 
-#if (LINUX_VERSION_CODE < KERNEL_VERSION(4, 3, 5) && LINUX_VERSION_CODE >= KERNEL_VERSION(4, 2, 0)) || (LINUX_VERSION_CODE < KERNEL_VERSION(4, 1, 17) && LINUX_VERSION_CODE > KERNEL_VERSION(3, 19, 0)) || LINUX_VERSION_CODE < KERNEL_VERSION(3, 18, 27)
+#if (LINUX_VERSION_CODE < KERNEL_VERSION(4, 3, 5) && LINUX_VERSION_CODE >= KERNEL_VERSION(4, 2, 0)) || (LINUX_VERSION_CODE < KERNEL_VERSION(4, 1, 17) && LINUX_VERSION_CODE > KERNEL_VERSION(3, 19, 0)) || (LINUX_VERSION_CODE < KERNEL_VERSION(3, 18, 27) && LINUX_VERSION_CODE >= KERNEL_VERSION(3, 17, 0)) || LINUX_VERSION_CODE < KERNEL_VERSION(3, 16, 8)
+#include <linux/if.h>
+#include <net/ip_tunnels.h>
 #define IP6_ECN_set_ce(a, b) IP6_ECN_set_ce(b)
 #endif
 
@@ -190,6 +96,13 @@ static inline u32 get_random_u32(void)
 }
 #endif
 
+#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 18, 0)
+static inline void netif_keep_dst(struct net_device *dev)
+{
+	dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
+}
+#endif
+
 /* https://lkml.org/lkml/2015/6/12/415 */
 #include <linux/netdevice.h>
 static inline struct net_device *netdev_pub(void *dev)
diff --git a/src/compat/dst_cache/dst_cache.c b/src/compat/dst_cache/dst_cache.c
index 145f112..24f1e90 100644
--- a/src/compat/dst_cache/dst_cache.c
+++ b/src/compat/dst_cache/dst_cache.c
@@ -152,8 +152,13 @@ EXPORT_SYMBOL_GPL(dst_cache_get_ip6);
 
 int dst_cache_init(struct dst_cache *dst_cache, gfp_t gfp)
 {
+#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 18, 0)
+	BUG_ON(gfp & GFP_ATOMIC);
+	dst_cache->cache = alloc_percpu(struct dst_cache_pcpu);
+#else
 	dst_cache->cache = alloc_percpu_gfp(struct dst_cache_pcpu,
 					    gfp | __GFP_ZERO);
+#endif
 	if (!dst_cache->cache)
 		return -ENOMEM;
 
diff --git a/src/compat/udp_tunnel/include/net/udp_tunnel.h b/src/compat/udp_tunnel/include/net/udp_tunnel.h
new file mode 100644
index 0000000..b80f1f5
--- /dev/null
+++ b/src/compat/udp_tunnel/include/net/udp_tunnel.h
@@ -0,0 +1,94 @@
+#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;
+
+	/* Used only for kernel-created sockets */
+	union {
+		struct in_addr		local_ip;
+#if IS_ENABLED(CONFIG_IPV6)
+		struct in6_addr		local_ip6;
+#endif
+	};
+
+	union {
+		struct in_addr		peer_ip;
+#if IS_ENABLED(CONFIG_IPV6)
+		struct in6_addr		peer_ip6;
+#endif
+	};
+
+	__be16			local_udp_port;
+	__be16			peer_udp_port;
+	unsigned int		use_udp_checksums:1,
+				use_udp6_tx_checksums:1,
+				use_udp6_rx_checksums:1,
+				ipv6_v6only:1;
+};
+
+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);
+
+struct udp_tunnel_sock_cfg {
+	void *sk_user_data;
+	__u8  encap_type;
+	udp_tunnel_encap_rcv_t encap_rcv;
+};
+
+/* 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. */
+void udp_tunnel_xmit_skb(struct rtable *rt, struct sock *sk, struct sk_buff *skb,
+			 __be32 src, __be32 dst, __u8 tos, __u8 ttl,
+			 __be16 df, __be16 src_port, __be16 dst_port,
+			 bool xnet, bool nocheck);
+
+#if IS_ENABLED(CONFIG_IPV6)
+int udp_tunnel6_xmit_skb(struct dst_entry *dst, struct sock *sk,
+			 struct sk_buff *skb,
+			 struct net_device *dev, struct in6_addr *saddr,
+			 struct in6_addr *daddr,
+			 __u8 prio, __u8 ttl, __be32 label,
+			 __be16 src_port, __be16 dst_port, bool nocheck);
+#endif
+
+void udp_tunnel_sock_release(struct socket *sock);
+
+#endif
diff --git a/src/compat/udp_tunnel/udp_tunnel.c b/src/compat/udp_tunnel/udp_tunnel.c
new file mode 100644
index 0000000..35e54e0
--- /dev/null
+++ b/src/compat/udp_tunnel/udp_tunnel.c
@@ -0,0 +1,232 @@
+#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 <net/net_namespace.h>
+#include <net/inet_common.h>
+#include <net/udp.h>
+#include <net/udp_tunnel.h>
+
+/* This is global so, uh, only one real call site... This is the kind of horrific hack you'd expect to see in compat code. */
+static udp_tunnel_encap_rcv_t encap_rcv = NULL;
+static void our_sk_data_ready(struct sock *sk)
+{
+	struct sk_buff *skb;
+	while ((skb = skb_dequeue(&sk->sk_receive_queue)) != NULL) {
+		skb_orphan(skb);
+		sk_mem_reclaim(sk);
+		encap_rcv(sk, skb);
+	}
+}
+
+int udp_sock_create4(struct net *net, struct udp_port_cfg *cfg,
+		     struct socket **sockp)
+{
+	int err;
+	struct socket *sock = NULL;
+	struct sockaddr_in udp_addr;
+
+	err = __sock_create(net, AF_INET, SOCK_DGRAM, 0, &sock, 1);
+	if (err < 0)
+		goto error;
+
+	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->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;
+
+	*sockp = sock;
+	return 0;
+
+error:
+	if (sock) {
+		kernel_sock_shutdown(sock, SHUT_RDWR);
+		sock_release(sock);
+	}
+	*sockp = NULL;
+	return err;
+}
+EXPORT_SYMBOL(udp_sock_create4);
+
+void setup_udp_tunnel_sock(struct net *net, struct socket *sock,
+			   struct udp_tunnel_sock_cfg *cfg)
+{
+	inet_sk(sock->sk)->mc_loop = 0;
+	encap_rcv = cfg->encap_rcv;
+	rcu_assign_sk_user_data(sock->sk, cfg->sk_user_data);
+	sock->sk->sk_data_ready = our_sk_data_ready;
+}
+EXPORT_SYMBOL_GPL(setup_udp_tunnel_sock);
+
+static void fake_destructor(struct sk_buff *skb)
+{
+}
+
+void udp_tunnel_xmit_skb(struct rtable *rt, struct sock *sk, struct sk_buff *skb,
+			 __be32 src, __be32 dst, __u8 tos, __u8 ttl,
+			 __be16 df, __be16 src_port, __be16 dst_port,
+			 bool xnet, bool nocheck)
+{
+	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);
+
+	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
+
+	udp_set_csum(nocheck, skb, src, dst, skb->len);
+
+	if (!skb->sk) {
+		skb->sk = sk;
+		skb->destructor = fake_destructor;
+	}
+
+	iptunnel_xmit(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);
+	sock_release(sock);
+}
+EXPORT_SYMBOL_GPL(udp_tunnel_sock_release);
+
+#if IS_ENABLED(CONFIG_IPV6)
+#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(net, AF_INET6, SOCK_DGRAM, 0, &sock, 1);
+	if (err < 0)
+		goto error;
+
+	if (cfg->ipv6_v6only) {
+		int val = 1;
+
+		err = kernel_setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY,
+					(char *) &val, sizeof(val));
+		if (err < 0)
+			goto error;
+	}
+
+	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);
+		sock_release(sock);
+	}
+	*sockp = NULL;
+	return err;
+}
+EXPORT_SYMBOL_GPL(udp_sock_create6);
+
+int udp_tunnel6_xmit_skb(struct dst_entry *dst, struct sock *sk,
+			 struct sk_buff *skb,
+			 struct net_device *dev, struct in6_addr *saddr,
+			 struct in6_addr *daddr,
+			 __u8 prio, __u8 ttl, __be32 label,
+			 __be16 src_port, __be16 dst_port, bool nocheck)
+{
+	struct udphdr *uh;
+	struct ipv6hdr *ip6h;
+
+	__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);
+
+	skb_dst_set(skb, dst);
+
+	udp6_set_csum(nocheck, skb, saddr, daddr, skb->len);
+
+	__skb_push(skb, sizeof(*ip6h));
+	skb_reset_network_header(skb);
+	ip6h		  = ipv6_hdr(skb);
+	ip6_flow_hdr(ip6h, prio, label);
+	ip6h->payload_len = htons(skb->len);
+	ip6h->nexthdr     = IPPROTO_UDP;
+	ip6h->hop_limit   = ttl;
+	ip6h->daddr	  = *daddr;
+	ip6h->saddr	  = *saddr;
+
+	if (!skb->sk) {
+		skb->sk = sk;
+		skb->destructor = fake_destructor;
+	}
+
+	ip6tunnel_xmit(skb, dev);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(udp_tunnel6_xmit_skb);
+#endif
diff --git a/src/compat/udp_tunnel/udp_tunnel_partial_compat.h b/src/compat/udp_tunnel/udp_tunnel_partial_compat.h
new file mode 100644
index 0000000..53ee6c3
--- /dev/null
+++ b/src/compat/udp_tunnel/udp_tunnel_partial_compat.h
@@ -0,0 +1,215 @@
+#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 18, 0)
+#define udp_sock_create4 udp_sock_create
+#define udp_sock_create6 udp_sock_create
+#include <linux/socket.h>
+#include <linux/if.h>
+#include <linux/in.h>
+#include <net/ip_tunnels.h>
+#include <net/udp.h>
+#include <net/inet_common.h>
+#if IS_ENABLED(CONFIG_IPV6)
+#include <linux/in6.h>
+#include <net/ipv6.h>
+#include <net/addrconf.h>
+#include <net/ip6_checksum.h>
+#include <net/ip6_tunnel.h>
+#endif
+static inline void fake_destructor(struct sk_buff *skb)
+{
+}
+typedef int (*udp_tunnel_encap_rcv_t)(struct sock *sk, struct sk_buff *skb);
+struct udp_tunnel_sock_cfg {
+        void *sk_user_data;
+        __u8  encap_type;
+        udp_tunnel_encap_rcv_t encap_rcv;
+};
+/* This is global so, uh, only one real call site... This is the kind of horrific hack you'd expect to see in compat code. */
+static udp_tunnel_encap_rcv_t encap_rcv = NULL;
+static void our_sk_data_ready(struct sock *sk)
+{
+	struct sk_buff *skb;
+	while ((skb = skb_dequeue(&sk->sk_receive_queue)) != NULL) {
+		skb_orphan(skb);
+		sk_mem_reclaim(sk);
+		encap_rcv(sk, skb);
+	}
+}
+static inline void setup_udp_tunnel_sock(struct net *net, struct socket *sock,
+                           struct udp_tunnel_sock_cfg *cfg)
+{
+	struct sock *sk = sock->sk;
+	inet_sk(sk)->mc_loop = 0;
+	encap_rcv = cfg->encap_rcv;
+	rcu_assign_sk_user_data(sk, cfg->sk_user_data);
+	sk->sk_data_ready = our_sk_data_ready;
+}
+static inline 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);
+}
+static inline 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);
+}
+#if IS_ENABLED(CONFIG_IPV6)
+static inline 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);
+	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;
+}
+#endif
+#endif
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 0, 0) && LINUX_VERSION_CODE >= KERNEL_VERSION(3, 17, 0)
+#include <linux/in.h>
+#include <linux/in6.h>
+#include <linux/udp.h>
+#include <linux/skbuff.h>
+#include <linux/if.h>
+#include <net/udp_tunnel.h>
+#define udp_tunnel_xmit_skb(a, b, c, d, e, f, g, h, i, j, k, l) do { struct net_device *dev__ = (c)->dev; int ret__; ret__ = udp_tunnel_xmit_skb((b)->sk_socket, a, c, d, e, f, g, h, i, j, k); iptunnel_xmit_stats(ret__, &dev__->stats, dev__->tstats); } while (0)
+#if IS_ENABLED(CONFIG_IPV6)
+#define udp_tunnel6_xmit_skb(a, b, c, d, e, f, g, h, i, j, k, l) udp_tunnel6_xmit_skb((b)->sk_socket, a, c, d, e, f, g, h, j, k);
+#endif
+#elif LINUX_VERSION_CODE < KERNEL_VERSION(4, 1, 0) && LINUX_VERSION_CODE >= KERNEL_VERSION(3, 17, 0)
+#include <linux/if.h>
+#include <net/udp_tunnel.h>
+#if LINUX_VERISON_CODE >= KERNEL_VERSION(3, 18, 0)
+static inline void fake_destructor(struct sk_buff *skb)
+{
+}
+#endif
+#define udp_tunnel_xmit_skb(a, b, c, d, e, f, g, h, i, j, k, l) do { struct net_device *dev__ = (c)->dev; int ret__; (c)->destructor = fake_destructor; (c)->sk = (b); ret__ = udp_tunnel_xmit_skb(a, c, d, e, f, g, h, i, j, k, l); iptunnel_xmit_stats(ret__, &dev__->stats, dev__->tstats); } while (0)
+#if IS_ENABLED(CONFIG_IPV6)
+#define udp_tunnel6_xmit_skb(a, b, c, d, e, f, g, h, i, j, k, l) do { (c)->destructor = fake_destructor; (c)->sk = (b); udp_tunnel6_xmit_skb(a, c, d, e, f, g, h, j, k, l); } while(0)
+#endif
+#else
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 5, 0) && LINUX_VERSION_CODE >= KERNEL_VERSION(3, 17, 0)
+#include <linux/if.h>
+#include <net/udp_tunnel.h>
+#define udp_tunnel_xmit_skb(a, b, c, d, e, f, g, h, i, j, k, l) do { struct net_device *dev__ = (c)->dev; int ret__ = udp_tunnel_xmit_skb(a, b, c, d, e, f, g, h, i, j, k, l);  iptunnel_xmit_stats(ret__, &dev__->stats, dev__->tstats); } while (0)
+#endif
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 6, 0) && IS_ENABLED(CONFIG_IPV6) && LINUX_VERSION_CODE >= KERNEL_VERSION(3, 17, 0)
+#include <linux/if.h>
+#include <net/udp_tunnel.h>
+#define udp_tunnel6_xmit_skb(a, b, c, d, e, f, g, h, i, j, k, l) udp_tunnel6_xmit_skb(a, b, c, d, e, f, g, h, j, k, l)
+#endif
+
+#endif
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 3, 0) && LINUX_VERSION_CODE >= KERNEL_VERSION(3, 17, 0)
+#include <linux/skbuff.h>
+#include <linux/if.h>
+#include <net/udp_tunnel.h>
+struct udp_port_cfg_new {
+	u8 family;
+	union {
+		struct in_addr local_ip;
+#if IS_ENABLED(CONFIG_IPV6)
+		struct in6_addr local_ip6;
+#endif
+	};
+	union {
+		struct in_addr peer_ip;
+#if IS_ENABLED(CONFIG_IPV6)
+		struct in6_addr peer_ip6;
+#endif
+	};
+	__be16 local_udp_port;
+	__be16 peer_udp_port;
+	unsigned int use_udp_checksums:1, use_udp6_tx_checksums:1, use_udp6_rx_checksums:1, ipv6_v6only:1;
+};
+static inline int __maybe_unused udp_sock_create_new(struct net *net, struct udp_port_cfg_new *cfg, struct socket **sockp)
+{
+	struct udp_port_cfg old_cfg = {
+		.family = cfg->family,
+		.local_ip = cfg->local_ip,
+#if IS_ENABLED(CONFIG_IPV6)
+		.local_ip6 = cfg->local_ip6,
+#endif
+		.peer_ip = cfg->peer_ip,
+#if IS_ENABLED(CONFIG_IPV6)
+		.peer_ip6 = cfg->peer_ip6,
+#endif
+		.local_udp_port = cfg->local_udp_port,
+		.peer_udp_port = cfg->peer_udp_port,
+		.use_udp_checksums = cfg->use_udp_checksums,
+		.use_udp6_tx_checksums = cfg->use_udp6_tx_checksums,
+		.use_udp6_rx_checksums = cfg->use_udp6_rx_checksums
+	};
+	if (cfg->family == AF_INET)
+		return udp_sock_create4(net, &old_cfg, sockp);
+
+#if IS_ENABLED(CONFIG_IPV6)
+	if (cfg->family == AF_INET6) {
+		int ret;
+		int old_bindv6only;
+		struct net *nobns;
+
+		if (cfg->ipv6_v6only) {
+#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 2, 0)
+			nobns = &init_net;
+#else
+			nobns = net;
+#endif
+			/* Since udp_port_cfg only learned of ipv6_v6only in 4.3, we do this horrible
+			 * hack here and set the sysctl variable temporarily to something that will
+			 * set the right option for us in sock_create. It's super racey! */
+			old_bindv6only = nobns->ipv6.sysctl.bindv6only;
+			nobns->ipv6.sysctl.bindv6only = 1;
+		}
+		ret = udp_sock_create6(net, &old_cfg, sockp);
+		if (cfg->ipv6_v6only)
+			nobns->ipv6.sysctl.bindv6only = old_bindv6only;
+		return ret;
+	}
+#endif
+	return -EPFNOSUPPORT;
+}
+#define udp_port_cfg udp_port_cfg_new
+#define udp_sock_create(a, b, c) udp_sock_create_new(a, b, c)
+#endif