[nf-next,v2] gtp: add initial driver for datapath of GPRS Tunneling Protocol (GTP-U)

diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index befd67d..0c5415b 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -192,6 +192,23 @@  config GENEVE
 	  To compile this driver as a module, choose M here: the module
 	  will be called geneve.
 
+config GTP
+	tristate "GPRS Tunneling Protocol datapath (GTP-U)"
+	depends on INET && NET_UDP_TUNNEL
+	select NET_IP_TUNNEL
+	---help---
+	  This allows one to create gtp virtual interfaces that provide
+	  the GPRS Tunneling Protocol datapath (GTP-U). This tunneling protocol
+	  is used to prevent subscribers from accessing mobile carrier core
+	  network infrastructure. This driver requires a userspace software that
+	  implements the signaling protocol (GTP-C) to update its PDP context
+	  base, such as OpenGGSN <http://git.osmocom.org/openggsn/). This
+	  tunneling protocol is implemented according to the GSM TS 09.60 and
+	  3GPP TS 29.060 standards.
+
+	  To compile this drivers as a module, choose M here: the module
+	  wil be called gtp.
+
 config MACSEC
 	tristate "IEEE 802.1AE MAC-level encryption (MACsec)"
 	select CRYPTO
diff --git a/drivers/net/Makefile b/drivers/net/Makefile
index 1aa7cb8..7336cbd 100644
--- a/drivers/net/Makefile
+++ b/drivers/net/Makefile
@@ -25,6 +25,7 @@  obj-$(CONFIG_VETH) += veth.o
 obj-$(CONFIG_VIRTIO_NET) += virtio_net.o
 obj-$(CONFIG_VXLAN) += vxlan.o
 obj-$(CONFIG_GENEVE) += geneve.o
+obj-$(CONFIG_GTP) += gtp.o
 obj-$(CONFIG_NLMON) += nlmon.o
 obj-$(CONFIG_NET_VRF) += vrf.o
 
diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c
new file mode 100644
index 0000000..8ce1104
--- /dev/null
+++ b/drivers/net/gtp.c
@@ -0,0 +1,1364 @@ 
+/* GTP according to GSM TS 09.60 / 3GPP TS 29.060
+ *
+ * (C) 2012-2014 by sysmocom - s.f.m.c. GmbH
+ * (C) 2016 by Pablo Neira Ayuso <pablo@netfilter.org>
+ *
+ * Author: Harald Welte <hwelte@sysmocom.de>
+ *	   Pablo Neira Ayuso <pablo@netfilter.org>
+ *	   Andreas Schultz <aschultz@travelping.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/version.h>
+#include <linux/skbuff.h>
+#include <linux/udp.h>
+#include <linux/rculist.h>
+#include <linux/jhash.h>
+#include <linux/if_tunnel.h>
+#include <linux/net.h>
+#include <linux/file.h>
+#include <linux/gtp.h>
+
+#include <net/net_namespace.h>
+#include <net/protocol.h>
+#include <net/ip.h>
+#include <net/udp.h>
+#include <net/udp_tunnel.h>
+#include <net/icmp.h>
+#include <net/xfrm.h>
+#include <net/genetlink.h>
+#include <net/netns/generic.h>
+#include <net/gtp.h>
+
+/* An active session for the subscriber. */
+struct pdp_ctx {
+	struct hlist_node	hlist_tid;
+	struct hlist_node	hlist_addr;
+
+	union {
+		u64		tid;
+		struct {
+			u64	tid;
+			u16	flow;
+		} v0;
+		struct {
+			u32	i_tei;
+			u32	o_tei;
+		} v1;
+	} u;
+	u8			gtp_version;
+	u16			af;
+
+	struct in_addr		ms_addr_ip4;
+	struct in_addr		sgsn_addr_ip4;
+
+	atomic_t		tx_seq;
+	struct rcu_head		rcu_head;
+};
+
+/* One instance of the GTP device. */
+struct gtp_dev {
+	struct list_head	list;
+
+	struct socket		*sock0;
+	struct socket		*sock1u;
+
+	struct net		*net;
+	struct net_device	*dev;
+
+	unsigned int		hash_size;
+	struct hlist_head	*tid_hash;
+	struct hlist_head	*addr_hash;
+};
+
+static int gtp_net_id __read_mostly;
+
+struct gtp_net {
+	struct list_head gtp_dev_list;
+};
+
+static u32 gtp_h_initval;
+
+static inline u32 gtp0_hashfn(u64 tid)
+{
+	u32 *tid32 = (u32 *) &tid;
+	return jhash_2words(tid32[0], tid32[1], gtp_h_initval);
+}
+
+static inline u32 gtp1u_hashfn(u32 tid)
+{
+	return jhash_1word(tid, gtp_h_initval);
+}
+
+static inline u32 ipv4_hashfn(__be32 ip)
+{
+	return jhash_1word((__force u32)ip, gtp_h_initval);
+}
+
+/* Resolve a PDP context structure based on the 64bit TID. */
+static struct pdp_ctx *gtp0_pdp_find(struct gtp_dev *gtp, u64 tid)
+{
+	struct hlist_head *head;
+	struct pdp_ctx *pdp;
+
+	head = &gtp->tid_hash[gtp0_hashfn(tid) % gtp->hash_size];
+
+	hlist_for_each_entry_rcu(pdp, head, hlist_tid) {
+		if (pdp->gtp_version == GTP_V0 &&
+		    pdp->u.v0.tid == tid)
+			return pdp;
+	}
+	return NULL;
+}
+
+/* Resolve a PDP context structure based on the 32bit TEI. */
+static struct pdp_ctx *gtp1_pdp_find(struct gtp_dev *gtp, u32 tid)
+{
+	struct hlist_head *head;
+	struct pdp_ctx *pdp;
+
+	head = &gtp->tid_hash[gtp1u_hashfn(tid) % gtp->hash_size];
+
+	hlist_for_each_entry_rcu(pdp, head, hlist_tid) {
+		if (pdp->gtp_version == GTP_V1 &&
+		    pdp->u.v1.i_tei == tid)
+			return pdp;
+	}
+	return NULL;
+}
+
+/* Resolve a PDP context based on IPv4 address of MS. */
+static struct pdp_ctx *ipv4_pdp_find(struct gtp_dev *gtp, __be32 ms_addr)
+{
+	struct hlist_head *head;
+	struct pdp_ctx *pdp;
+
+	head = &gtp->addr_hash[ipv4_hashfn(ms_addr) % gtp->hash_size];
+
+	hlist_for_each_entry_rcu(pdp, head, hlist_addr) {
+		if (pdp->af == AF_INET &&
+		    pdp->ms_addr_ip4.s_addr == ms_addr)
+			return pdp;
+	}
+
+	return NULL;
+}
+
+static bool gtp_check_src_ms_ipv4(struct sk_buff *skb, struct pdp_ctx *pctx,
+				  unsigned int hdrlen)
+{
+	struct iphdr *iph;
+
+	if (!pskb_may_pull(skb, hdrlen + sizeof(struct iphdr)))
+		return false;
+
+	iph = (struct iphdr *)(skb->data + hdrlen + sizeof(struct iphdr));
+
+	return iph->saddr != pctx->ms_addr_ip4.s_addr;
+}
+
+/* Check if the inner IP source address in this packet is assigned to any
+ * existing mobile subscriber.
+ */
+static bool gtp_check_src_ms(struct sk_buff *skb, struct pdp_ctx *pctx,
+			     unsigned int hdrlen)
+{
+	switch (ntohs(skb->protocol)) {
+	case ETH_P_IP:
+		return gtp_check_src_ms_ipv4(skb, pctx, hdrlen);
+	}
+	return false;
+}
+
+/* 1 means pass up to the stack, -1 means drop and 0 means decapsulated. */
+static int gtp0_udp_encap_recv(struct gtp_dev *gtp, struct sk_buff *skb,
+			       bool xnet)
+{
+	unsigned int hdrlen = sizeof(struct udphdr) +
+			      sizeof(struct gtp0_header);
+	struct gtp0_header *gtp0;
+	struct pdp_ctx *pctx;
+	int ret = 0;
+
+	if (!pskb_may_pull(skb, hdrlen))
+		return -1;
+
+	gtp0 = (struct gtp0_header *)(skb->data + sizeof(struct udphdr));
+
+	if ((gtp0->flags >> 5) != GTP_V0)
+		return 1;
+
+	if (gtp0->type != GTP_TPDU)
+		return 1;
+
+	rcu_read_lock();
+	pctx = gtp0_pdp_find(gtp, be64_to_cpu(gtp0->tid));
+	if (!pctx) {
+		netdev_dbg(gtp->dev, "No PDP ctx to decap skb=%p\n", skb);
+		ret = -1;
+		goto out_rcu;
+	}
+
+	if (!gtp_check_src_ms(skb, pctx, hdrlen)) {
+		netdev_dbg(gtp->dev, "No PDP ctx for this MS\n");
+		ret = -1;
+		goto out_rcu;
+	}
+	rcu_read_unlock();
+
+	/* Get rid of the GTP + UDP headers. */
+	return iptunnel_pull_header(skb, hdrlen, skb->protocol, xnet);
+out_rcu:
+	rcu_read_unlock();
+	return ret;
+}
+
+static int gtp1u_udp_encap_recv(struct gtp_dev *gtp, struct sk_buff *skb,
+				bool xnet)
+{
+	unsigned int hdrlen = sizeof(struct udphdr) +
+			      sizeof(struct gtp1_header);
+	struct gtp1_header *gtp1;
+	struct pdp_ctx *pctx;
+	int ret = 0;
+
+	if (!pskb_may_pull(skb, hdrlen))
+		return -1;
+
+	gtp1 = (struct gtp1_header *)(skb->data + sizeof(struct udphdr));
+
+	if ((gtp1->flags >> 5) != GTP_V1)
+		return 1;
+
+	if (gtp1->type != GTP_TPDU)
+		return 1;
+
+	/* From 29.060: "This field shall be present if and only if any one or
+	 * more of the S, PN and E flags are set.".
+	 *
+	 * If any of the bit is set, then the remaining ones also have to be
+	 * set.
+	 */
+	if (gtp1->flags & GTP1_F_MASK)
+		hdrlen += 4;
+
+	/* Make sure the header is larger enough, including extensions. */
+	if (!pskb_may_pull(skb, hdrlen))
+		return -1;
+
+	rcu_read_lock();
+	pctx = gtp1_pdp_find(gtp, ntohl(gtp1->tid));
+	if (!pctx) {
+		netdev_dbg(gtp->dev, "No PDP ctx to decap skb=%p\n", skb);
+		ret = -1;
+		goto out_rcu;
+	}
+
+	if (!gtp_check_src_ms(skb, pctx, hdrlen)) {
+		netdev_dbg(gtp->dev, "No PDP ctx for this MS\n");
+		ret = -1;
+		goto out_rcu;
+	}
+	rcu_read_unlock();
+
+	/* Get rid of the GTP + UDP headers. */
+	return iptunnel_pull_header(skb, hdrlen, skb->protocol, xnet);
+out_rcu:
+	rcu_read_unlock();
+	return ret;
+}
+
+static void gtp_encap_disable(struct gtp_dev *gtp)
+{
+	if (gtp->sock0 && gtp->sock0->sk) {
+		udp_sk(gtp->sock0->sk)->encap_type = 0;
+		rcu_assign_sk_user_data(gtp->sock0->sk, NULL);
+	}
+	if (gtp->sock1u && gtp->sock1u->sk) {
+		udp_sk(gtp->sock1u->sk)->encap_type = 0;
+		rcu_assign_sk_user_data(gtp->sock1u->sk, NULL);
+	}
+
+	gtp->sock0 = NULL;
+	gtp->sock1u = NULL;
+}
+
+static void gtp_encap_destroy(struct sock *sk)
+{
+	struct gtp_dev *gtp;
+
+	gtp = rcu_dereference_sk_user_data(sk);
+	if (gtp)
+		gtp_encap_disable(gtp);
+}
+
+/* UDP encapsulation receive handler. See net/ipv4/udp.c.
+ * Return codes: 0: success, <0: error, >0: pass up to userspace UDP socket.
+ */
+static int gtp_encap_recv(struct sock *sk, struct sk_buff *skb)
+{
+	struct pcpu_sw_netstats *stats;
+	struct gtp_dev *gtp;
+	bool xnet;
+	int ret;
+
+	gtp = rcu_dereference_sk_user_data(sk);
+	if (!gtp)
+		return 1;
+
+	netdev_dbg(gtp->dev, "encap_recv sk=%p\n", sk);
+
+	xnet = !net_eq(gtp->net, dev_net(gtp->dev));
+
+	switch (udp_sk(sk)->encap_type) {
+	case UDP_ENCAP_GTP0:
+		netdev_dbg(gtp->dev, "received GTP0 packet\n");
+		ret = gtp0_udp_encap_recv(gtp, skb, xnet);
+		break;
+	case UDP_ENCAP_GTP1U:
+		netdev_dbg(gtp->dev, "received GTP1U packet\n");
+		ret = gtp1u_udp_encap_recv(gtp, skb, xnet);
+		break;
+	default:
+		ret = -1; /* Shouldn't happen. */
+	}
+
+	switch (ret) {
+	case 1:
+		netdev_dbg(gtp->dev, "pass up to the process\n");
+		return 1;
+	case 0:
+		netdev_dbg(gtp->dev, "forwarding packet from GGSN to uplink\n");
+		break;
+	case -1:
+		netdev_dbg(gtp->dev, "GTP packet has been dropped\n");
+		kfree_skb(skb);
+		return 0;
+	}
+
+	/* Now that the UDP and the GTP header have been removed, set up the
+	 * new network header. This is required by the upper layer to
+	 * calculate the transport header.
+	 */
+	skb_reset_network_header(skb);
+
+	skb->dev = gtp->dev;
+
+	stats = this_cpu_ptr(gtp->dev->tstats);
+	u64_stats_update_begin(&stats->syncp);
+	stats->rx_packets++;
+	stats->rx_bytes += skb->len;
+	u64_stats_update_end(&stats->syncp);
+
+	netif_rx(skb);
+
+	return 0;
+}
+
+static int gtp_dev_init(struct net_device *dev)
+{
+	struct gtp_dev *gtp = netdev_priv(dev);
+
+	gtp->dev = dev;
+
+	dev->tstats = alloc_percpu(struct pcpu_sw_netstats);
+	if (!dev->tstats)
+		return -ENOMEM;
+
+	return 0;
+}
+
+static void gtp_dev_uninit(struct net_device *dev)
+{
+	struct gtp_dev *gtp = netdev_priv(dev);
+
+	gtp_encap_disable(gtp);
+	free_percpu(dev->tstats);
+}
+
+static struct rtable *ip4_route_output_gtp(struct net *net, struct flowi4 *fl4,
+					   const struct sock *sk, __be32 daddr)
+{
+	memset(fl4, 0, sizeof(*fl4));
+	fl4->flowi4_oif		= sk->sk_bound_dev_if;
+	fl4->daddr		= daddr;
+	fl4->saddr		= inet_sk(sk)->inet_saddr;
+	fl4->flowi4_tos		= RT_CONN_FLAGS(sk);
+	fl4->flowi4_proto	= sk->sk_protocol;
+
+	return ip_route_output_key(net, fl4);
+}
+
+static inline void gtp0_push_header(struct sk_buff *skb, struct pdp_ctx *pctx)
+{
+	int payload_len = skb->len;
+	struct gtp0_header *gtp0;
+
+	gtp0 = (struct gtp0_header *) skb_push(skb, sizeof(*gtp0));
+
+	gtp0->flags	= 0x1e; /* v0, GTP-non-prime. */
+	gtp0->type	= GTP_TPDU;
+	gtp0->length	= htons(payload_len);
+	gtp0->seq	= htons((atomic_inc_return(&pctx->tx_seq) - 1) % 0xffff);
+	gtp0->flow	= htons(pctx->u.v0.flow);
+	gtp0->number	= 0xff;
+	gtp0->spare[0]	= gtp0->spare[1] = gtp0->spare[2] = 0xff;
+	gtp0->tid	= cpu_to_be64(pctx->u.v0.tid);
+}
+
+static inline void gtp1_push_header(struct sk_buff *skb, struct pdp_ctx *pctx)
+{
+	int payload_len = skb->len;
+	struct gtp1_header *gtp1;
+
+	gtp1 = (struct gtp1_header *) skb_push(skb, sizeof(*gtp1));
+
+	/* Bits    8  7  6  5  4  3  2	1
+	 *	  +--+--+--+--+--+--+--+--+
+	 *	  |version |PT| 1| E| S|PN|
+	 *	  +--+--+--+--+--+--+--+--+
+	 *	    0  0  1  1	1  0  0  0
+	 */
+	gtp1->flags	= 0x38; /* v1, GTP-non-prime. */
+	gtp1->type	= GTP_TPDU;
+	gtp1->length	= htons(payload_len);
+	gtp1->tid	= htonl(pctx->u.v1.o_tei);
+
+	/* TODO: Suppport for extension header, sequence number and N-PDU.
+	 *	 Update the length field if any of them is available.
+	 */
+}
+
+struct gtp_pktinfo {
+	struct sock		*sk;
+	struct iphdr		*iph;
+	struct flowi4		fl4;
+	struct rtable		*rt;
+	struct pdp_ctx		*pctx;
+	struct net_device	*dev;
+	__be16			gtph_port;
+};
+
+static void gtp_push_header(struct sk_buff *skb, struct gtp_pktinfo *pktinfo)
+{
+	switch (pktinfo->pctx->gtp_version) {
+	case GTP_V0:
+		pktinfo->gtph_port = htons(GTP0_PORT);
+		gtp0_push_header(skb, pktinfo->pctx);
+		break;
+	case GTP_V1:
+		pktinfo->gtph_port = htons(GTP1U_PORT);
+		gtp1_push_header(skb, pktinfo->pctx);
+		break;
+	}
+}
+
+static inline void gtp_set_pktinfo_ipv4(struct gtp_pktinfo *pktinfo,
+					struct sock *sk, struct iphdr *iph,
+					struct pdp_ctx *pctx, struct rtable *rt,
+					struct flowi4 *fl4,
+					struct net_device *dev)
+{
+	pktinfo->sk	= sk;
+	pktinfo->iph	= iph;
+	pktinfo->pctx	= pctx;
+	pktinfo->rt	= rt;
+	pktinfo->fl4	= *fl4;
+	pktinfo->dev	= dev;
+}
+
+static int gtp_build_skb_ip4(struct sk_buff *skb, struct net_device *dev,
+			     struct gtp_pktinfo *pktinfo)
+{
+	struct gtp_dev *gtp = netdev_priv(dev);
+	struct pdp_ctx *pctx;
+	struct rtable *rt;
+	struct flowi4 fl4;
+	struct iphdr *iph;
+	struct sock *sk;
+	__be16 df;
+	int mtu;
+
+	/* Read the IP destination address and resolve the PDP context.
+	 * Prepend PDP header with TEI/TID from PDP ctx.
+	 */
+	iph = ip_hdr(skb);
+	pctx = ipv4_pdp_find(gtp, iph->daddr);
+	if (!pctx) {
+		netdev_dbg(dev, "no PDP ctx found for %pI4, skip\n",
+			   &iph->daddr);
+		return -ENOENT;
+	}
+	netdev_dbg(dev, "found PDP context %p\n", pctx);
+
+	switch (pctx->gtp_version) {
+	case GTP_V0:
+		if (gtp->sock0)
+			sk = gtp->sock0->sk;
+		else
+			sk = NULL;
+		break;
+	case GTP_V1:
+		if (gtp->sock1u)
+			sk = gtp->sock1u->sk;
+		else
+			sk = NULL;
+		break;
+	default:
+		return -ENOENT;
+	}
+
+	if (!sk) {
+		netdev_dbg(dev, "no userspace socket is available, skip\n");
+		return -ENOENT;
+	}
+
+	rt = ip4_route_output_gtp(sock_net(sk), &fl4, gtp->sock0->sk,
+				  pctx->sgsn_addr_ip4.s_addr);
+	if (IS_ERR(rt)) {
+		netdev_dbg(dev, "no route to SSGN %pI4\n",
+			   &pctx->sgsn_addr_ip4.s_addr);
+		dev->stats.tx_carrier_errors++;
+		goto err;
+	}
+
+	if (rt->dst.dev == dev) {
+		netdev_dbg(dev, "circular route to SSGN %pI4\n",
+			   &pctx->sgsn_addr_ip4.s_addr);
+		dev->stats.collisions++;
+		goto err_rt;
+	}
+
+	skb_dst_drop(skb);
+
+	/* This is similar to tnl_update_pmtu(). */
+	df = iph->frag_off;
+	if (df) {
+		mtu = dst_mtu(&rt->dst) - dev->hard_header_len -
+			sizeof(struct iphdr) - sizeof(struct udphdr);
+		switch (pctx->gtp_version) {
+		case GTP_V0:
+			mtu -= sizeof(struct gtp0_header);
+			break;
+		case GTP_V1:
+			mtu -= sizeof(struct gtp1_header);
+			break;
+		}
+	} else {
+		mtu = dst_mtu(&rt->dst);
+	}
+
+	rt->dst.ops->update_pmtu(&rt->dst, NULL, skb, mtu);
+
+	if (!skb_is_gso(skb) && (iph->frag_off & htons(IP_DF)) &&
+	    mtu < ntohs(iph->tot_len)) {
+		netdev_dbg(dev, "packet too big, fragmentation needed\n");
+		memset(IPCB(skb), 0, sizeof(*IPCB(skb)));
+		icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
+			  htonl(mtu));
+		goto err_rt;
+	}
+
+	gtp_set_pktinfo_ipv4(pktinfo, sk, iph, pctx, rt, &fl4, dev);
+	gtp_push_header(skb, pktinfo);
+
+	return 0;
+err_rt:
+	ip_rt_put(rt);
+err:
+	return -EBADMSG;
+}
+
+static netdev_tx_t gtp_dev_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	unsigned int proto = ntohs(skb->protocol);
+	struct gtp_pktinfo pktinfo;
+	int err;
+
+	/* Ensure there is sufficient headroom. */
+	if (skb_cow_head(skb, dev->needed_headroom))
+		goto tx_err;
+
+	skb_reset_inner_headers(skb);
+
+	/* PDP context lookups in gtp_build_skb_*() need rcu read-side lock. */
+	rcu_read_lock();
+	switch (proto) {
+	case ETH_P_IP:
+		err = gtp_build_skb_ip4(skb, dev, &pktinfo);
+		break;
+	default:
+		err = -EOPNOTSUPP;
+		break;
+	}
+	rcu_read_unlock();
+
+	if (err < 0)
+		goto tx_err;
+
+	switch (proto) {
+	case ETH_P_IP:
+		netdev_dbg(pktinfo.dev, "gtp -> IP src: %pI4 dst: %pI4\n",
+			   &pktinfo.iph->saddr, &pktinfo.iph->daddr);
+		udp_tunnel_xmit_skb(pktinfo.rt, pktinfo.sk, skb,
+				    pktinfo.fl4.saddr, pktinfo.fl4.daddr,
+				    pktinfo.iph->tos,
+				    ip4_dst_hoplimit(&pktinfo.rt->dst),
+				    htons(IP_DF),
+				    pktinfo.gtph_port, pktinfo.gtph_port,
+				    true, false);
+		break;
+	}
+
+	return NETDEV_TX_OK;
+tx_err:
+	dev->stats.tx_errors++;
+	dev_kfree_skb(skb);
+	return NETDEV_TX_OK;
+}
+
+static const struct net_device_ops gtp_netdev_ops = {
+	.ndo_init		= gtp_dev_init,
+	.ndo_uninit		= gtp_dev_uninit,
+	.ndo_start_xmit		= gtp_dev_xmit,
+	.ndo_get_stats64	= ip_tunnel_get_stats64,
+};
+
+static void gtp_link_setup(struct net_device *dev)
+{
+	dev->netdev_ops		= &gtp_netdev_ops;
+	dev->destructor		= free_netdev;
+
+	dev->hard_header_len = 0;
+	dev->addr_len = 0;
+
+	/* Zero header length. */
+	dev->type = ARPHRD_NONE;
+	dev->flags = IFF_POINTOPOINT | IFF_NOARP | IFF_MULTICAST;
+
+	dev->priv_flags	|= IFF_NO_QUEUE;
+	dev->features	|= NETIF_F_LLTX;
+	netif_keep_dst(dev);
+
+	/* Assume largest header, ie. GTPv0. */
+	dev->needed_headroom	= LL_MAX_HEADER +
+				  sizeof(struct iphdr) +
+				  sizeof(struct udphdr) +
+				  sizeof(struct gtp0_header);
+}
+
+static int gtp_hashtable_new(struct gtp_dev *gtp, int hsize);
+static void gtp_hashtable_free(struct gtp_dev *gtp);
+static int gtp_encap_enable(struct net_device *dev, struct gtp_dev *gtp,
+			    int fd_gtp0, int fd_gtp1, struct net *src_net);
+
+static int gtp_newlink(struct net *src_net, struct net_device *dev,
+			struct nlattr *tb[], struct nlattr *data[])
+{
+	int hashsize, err, fd0, fd1;
+	struct gtp_dev *gtp;
+	struct gtp_net *gn;
+
+	if (!data[IFLA_GTP_FD0] || !data[IFLA_GTP_FD1])
+		return -EINVAL;
+
+	gtp = netdev_priv(dev);
+
+	fd0 = nla_get_u32(data[IFLA_GTP_FD0]);
+	fd1 = nla_get_u32(data[IFLA_GTP_FD1]);
+
+	err = gtp_encap_enable(dev, gtp, fd0, fd1, src_net);
+	if (err < 0)
+		goto out_err;
+
+	if (!data[IFLA_GTP_PDP_HASHSIZE])
+		hashsize = 1024;
+	else
+		hashsize = nla_get_u32(data[IFLA_GTP_PDP_HASHSIZE]);
+
+	err = gtp_hashtable_new(gtp, hashsize);
+	if (err < 0)
+		goto out_encap;
+
+	err = register_netdevice(dev);
+	if (err < 0) {
+		netdev_dbg(dev, "failed to register new netdev %d\n", err);
+		goto out_hashtable;
+	}
+
+	gn = net_generic(dev_net(dev), gtp_net_id);
+	list_add_rcu(&gtp->list, &gn->gtp_dev_list);
+
+	netdev_dbg(dev, "registered new GTP interface\n");
+
+	return 0;
+
+out_hashtable:
+	gtp_hashtable_free(gtp);
+out_encap:
+	gtp_encap_disable(gtp);
+out_err:
+	return err;
+}
+
+static void gtp_dellink(struct net_device *dev, struct list_head *head)
+{
+	struct gtp_dev *gtp = netdev_priv(dev);
+
+	gtp_encap_disable(gtp);
+	gtp_hashtable_free(gtp);
+	list_del_rcu(&gtp->list);
+	unregister_netdevice_queue(dev, head);
+}
+
+static const struct nla_policy gtp_policy[IFLA_GTP_MAX + 1] = {
+	[IFLA_GTP_FD0]			= { .type = NLA_U32 },
+	[IFLA_GTP_FD1]			= { .type = NLA_U32 },
+	[IFLA_GTP_PDP_HASHSIZE]		= { .type = NLA_U32 },
+};
+
+static int gtp_validate(struct nlattr *tb[], struct nlattr *data[])
+{
+	if (!data)
+		return -EINVAL;
+
+	return 0;
+}
+
+static size_t gtp_get_size(const struct net_device *dev)
+{
+	return nla_total_size(sizeof(__u32));	/* IFLA_GTP_PDP_HASHSIZE */
+}
+
+static int gtp_fill_info(struct sk_buff *skb, const struct net_device *dev)
+{
+	struct gtp_dev *gtp = netdev_priv(dev);
+
+	if (nla_put_u32(skb, IFLA_GTP_PDP_HASHSIZE, gtp->hash_size))
+		goto nla_put_failure;
+
+	return 0;
+
+nla_put_failure:
+	return -EMSGSIZE;
+}
+
+static struct rtnl_link_ops gtp_link_ops __read_mostly = {
+	.kind		= "gtp",
+	.maxtype	= IFLA_GTP_MAX,
+	.policy		= gtp_policy,
+	.priv_size	= sizeof(struct gtp_dev),
+	.setup		= gtp_link_setup,
+	.validate	= gtp_validate,
+	.newlink	= gtp_newlink,
+	.dellink	= gtp_dellink,
+	.get_size	= gtp_get_size,
+	.fill_info	= gtp_fill_info,
+};
+
+static struct net *gtp_genl_get_net(struct net *src_net, struct nlattr *tb[])
+{
+	struct net *net;
+
+	/* Examine the link attributes and figure out which network namespace
+	 * we are talking about.
+	 */
+	if (tb[GTPA_NET_NS_FD])
+		net = get_net_ns_by_fd(nla_get_u32(tb[GTPA_NET_NS_FD]));
+	else
+		net = get_net(src_net);
+
+	return net;
+}
+
+static int gtp_hashtable_new(struct gtp_dev *gtp, int hsize)
+{
+	int i;
+
+	gtp->addr_hash = kmalloc(sizeof(struct hlist_head) * hsize, GFP_KERNEL);
+	if (gtp->addr_hash == NULL)
+		return -ENOMEM;
+
+	gtp->tid_hash = kmalloc(sizeof(struct hlist_head) * hsize, GFP_KERNEL);
+	if (gtp->tid_hash == NULL)
+		goto err1;
+
+	gtp->hash_size = hsize;
+
+	for (i = 0; i < hsize; i++) {
+		INIT_HLIST_HEAD(&gtp->addr_hash[i]);
+		INIT_HLIST_HEAD(&gtp->tid_hash[i]);
+	}
+	return 0;
+err1:
+	kfree(gtp->addr_hash);
+	return -ENOMEM;
+}
+
+static void gtp_hashtable_free(struct gtp_dev *gtp)
+{
+	struct pdp_ctx *pctx;
+	int i;
+
+	for (i = 0; i < gtp->hash_size; i++) {
+		hlist_for_each_entry_rcu(pctx, &gtp->tid_hash[i], hlist_tid) {
+			hlist_del_rcu(&pctx->hlist_tid);
+			hlist_del_rcu(&pctx->hlist_addr);
+			kfree_rcu(pctx, rcu_head);
+		}
+	}
+	synchronize_rcu();
+	kfree(gtp->addr_hash);
+	kfree(gtp->tid_hash);
+}
+
+static int gtp_encap_enable(struct net_device *dev, struct gtp_dev *gtp,
+			    int fd_gtp0, int fd_gtp1, struct net *src_net)
+{
+	struct udp_tunnel_sock_cfg tuncfg = {NULL};
+	struct socket *sock0, *sock1u;
+	int err;
+
+	netdev_dbg(dev, "enable gtp on %d, %d\n", fd_gtp0, fd_gtp1);
+
+	sock0 = sockfd_lookup(fd_gtp0, &err);
+	if (sock0 == NULL) {
+		netdev_dbg(dev, "socket fd=%d not found (gtp0)\n", fd_gtp0);
+		return -ENOENT;
+	}
+
+	if (sock0->sk->sk_protocol != IPPROTO_UDP) {
+		netdev_dbg(dev, "socket fd=%d not UDP\n", fd_gtp0);
+		err = -EINVAL;
+		goto err1;
+	}
+
+	sock1u = sockfd_lookup(fd_gtp1, &err);
+	if (sock1u == NULL) {
+		netdev_dbg(dev, "socket fd=%d not found (gtp1u)\n", fd_gtp1);
+		err = -ENOENT;
+		goto err1;
+	}
+
+	if (sock1u->sk->sk_protocol != IPPROTO_UDP) {
+		netdev_dbg(dev, "socket fd=%d not UDP\n", fd_gtp1);
+		err = -EINVAL;
+		goto err2;
+	}
+
+	netdev_dbg(dev, "enable gtp on %p, %p\n", sock0, sock1u);
+
+	gtp->sock0 = sock0;
+	gtp->sock1u = sock1u;
+	gtp->net = src_net;
+
+	tuncfg.sk_user_data = gtp;
+	tuncfg.encap_rcv = gtp_encap_recv;
+	tuncfg.encap_destroy = gtp_encap_destroy;
+
+	tuncfg.encap_type = UDP_ENCAP_GTP0;
+	setup_udp_tunnel_sock(sock_net(gtp->sock0->sk), gtp->sock0, &tuncfg);
+
+	tuncfg.encap_type = UDP_ENCAP_GTP1U;
+	setup_udp_tunnel_sock(sock_net(gtp->sock1u->sk), gtp->sock1u, &tuncfg);
+
+	err = 0;
+err2:
+	sockfd_put(sock1u);
+err1:
+	sockfd_put(sock0);
+	return err;
+}
+
+static struct net_device *gtp_find_dev(struct net *net, int ifindex)
+{
+	struct gtp_net *gn = net_generic(net, gtp_net_id);
+	struct gtp_dev *gtp;
+
+	list_for_each_entry_rcu(gtp, &gn->gtp_dev_list, list) {
+		if (ifindex == gtp->dev->ifindex)
+			return gtp->dev;
+	}
+	return NULL;
+}
+
+static void ipv4_pdp_fill(struct pdp_ctx *pctx, struct genl_info *info)
+{
+	pctx->gtp_version = nla_get_u32(info->attrs[GTPA_VERSION]);
+	pctx->af = AF_INET;
+	pctx->sgsn_addr_ip4.s_addr =
+		nla_get_be32(info->attrs[GTPA_SGSN_ADDRESS]);
+	pctx->ms_addr_ip4.s_addr =
+		nla_get_be32(info->attrs[GTPA_MS_ADDRESS]);
+
+	switch (pctx->gtp_version) {
+	case GTP_V0:
+		/* According to TS 09.60, sections 7.5.1 and 7.5.2, the flow
+		 * label needs to be the same for uplink and downlink packets,
+		 * so let's annotate this.
+		 */
+		pctx->u.v0.tid = nla_get_u64(info->attrs[GTPA_TID]);
+		pctx->u.v0.flow = nla_get_u16(info->attrs[GTPA_FLOW]);
+		break;
+	case GTP_V1:
+		pctx->u.v1.i_tei = nla_get_u32(info->attrs[GTPA_I_TEI]);
+		pctx->u.v1.o_tei = nla_get_u32(info->attrs[GTPA_O_TEI]);
+		break;
+	default:
+		break;
+	}
+}
+
+static int ipv4_pdp_add(struct net_device *dev, struct genl_info *info)
+{
+	struct gtp_dev *gtp = netdev_priv(dev);
+	u32 hash_ms, hash_tid = 0;
+	struct pdp_ctx *pctx;
+	bool found = false;
+	__be32 ms_addr;
+
+	ms_addr = nla_get_be32(info->attrs[GTPA_MS_ADDRESS]);
+	hash_ms = ipv4_hashfn(ms_addr) % gtp->hash_size;
+
+	hlist_for_each_entry_rcu(pctx, &gtp->addr_hash[hash_ms], hlist_addr) {
+		if (pctx->ms_addr_ip4.s_addr == ms_addr) {
+			found = true;
+			break;
+		}
+	}
+
+	if (found) {
+		if (info->nlhdr->nlmsg_flags & NLM_F_EXCL)
+			return -EEXIST;
+		if (info->nlhdr->nlmsg_flags & NLM_F_REPLACE)
+			return -EOPNOTSUPP;
+
+		ipv4_pdp_fill(pctx, info);
+
+		if (pctx->gtp_version == GTP_V0)
+			netdev_dbg(dev, "GTPv0-U: update tunnel id = %llx (pdp %p)\n",
+				   pctx->u.v0.tid, pctx);
+		else if (pctx->gtp_version == GTP_V1)
+			netdev_dbg(dev, "GTPv1-U: update tunnel id = %x/%x (pdp %p)\n",
+				   pctx->u.v1.i_tei, pctx->u.v1.o_tei, pctx);
+
+		return 0;
+
+	}
+
+	pctx = kmalloc(sizeof(struct pdp_ctx), GFP_KERNEL);
+	if (pctx == NULL)
+		return -ENOMEM;
+
+	ipv4_pdp_fill(pctx, info);
+	atomic_set(&pctx->tx_seq, 0);
+
+	switch (pctx->gtp_version) {
+	case GTP_V0:
+		/* TS 09.60: "The flow label identifies unambiguously a GTP
+		 * flow.". We use the tid for this instead, I cannot find a
+		 * situation in which this doesn't unambiguosly identify the
+		 * PDP context.
+		 */
+		hash_tid = gtp0_hashfn(pctx->u.v0.tid) % gtp->hash_size;
+		break;
+	case GTP_V1:
+		hash_tid = gtp1u_hashfn(pctx->u.v1.i_tei) % gtp->hash_size;
+		break;
+	}
+
+	hlist_add_head_rcu(&pctx->hlist_addr, &gtp->addr_hash[hash_ms]);
+	hlist_add_head_rcu(&pctx->hlist_tid, &gtp->tid_hash[hash_tid]);
+
+	switch (pctx->gtp_version) {
+	case GTP_V0:
+		netdev_dbg(dev, "GTPv0-U: new PDP ctx id=%llx ssgn=%pI4 ms=%pI4 (pdp=%p)\n",
+			   pctx->u.v0.tid, &pctx->sgsn_addr_ip4,
+			   &pctx->ms_addr_ip4, pctx);
+		break;
+	case GTP_V1:
+		netdev_dbg(dev, "GTPv1-U: new PDP ctx id=%x/%x ssgn=%pI4 ms=%pI4 (pdp=%p)\n",
+			   pctx->u.v1.i_tei, pctx->u.v1.o_tei,
+			   &pctx->sgsn_addr_ip4, &pctx->ms_addr_ip4, pctx);
+		break;
+	}
+
+	return 0;
+}
+
+static int gtp_genl_new_pdp(struct sk_buff *skb, struct genl_info *info)
+{
+	struct net_device *dev;
+	struct net *net;
+
+	if (!info->attrs[GTPA_VERSION] ||
+	    !info->attrs[GTPA_LINK] ||
+	    !info->attrs[GTPA_SGSN_ADDRESS] ||
+	    !info->attrs[GTPA_MS_ADDRESS])
+		return -EINVAL;
+
+	switch (nla_get_u32(info->attrs[GTPA_VERSION])) {
+	case GTP_V0:
+		if (!info->attrs[GTPA_TID] ||
+		    !info->attrs[GTPA_FLOW])
+			return -EINVAL;
+		break;
+	case GTP_V1:
+		if (!info->attrs[GTPA_I_TEI] ||
+		    !info->attrs[GTPA_O_TEI])
+			return -EINVAL;
+		break;
+
+	default:
+		return -EINVAL;
+	}
+
+	net = gtp_genl_get_net(sock_net(skb->sk), info->attrs);
+	if (IS_ERR(net))
+		return PTR_ERR(net);
+
+	/* Check if there's an existing gtpX device to configure */
+	dev = gtp_find_dev(net, nla_get_u32(info->attrs[GTPA_LINK]));
+	if (dev == NULL)
+		return -ENODEV;
+
+	return ipv4_pdp_add(dev, info);
+}
+
+static int gtp_genl_del_pdp(struct sk_buff *skb, struct genl_info *info)
+{
+	struct net_device *dev;
+	struct pdp_ctx *pctx;
+	struct gtp_dev *gtp;
+	struct net *net;
+
+	if (!info->attrs[GTPA_VERSION] ||
+	    !info->attrs[GTPA_LINK])
+		return -EINVAL;
+
+	net = gtp_genl_get_net(sock_net(skb->sk), info->attrs);
+	if (IS_ERR(net))
+		return PTR_ERR(net);
+
+	/* Check if there's an existing gtpX device to configure */
+	dev = gtp_find_dev(net, nla_get_u32(info->attrs[GTPA_LINK]));
+	if (dev == NULL)
+		return -ENODEV;
+
+	gtp = netdev_priv(dev);
+
+	switch (nla_get_u32(info->attrs[GTPA_VERSION])) {
+	case GTP_V0:
+		if (!info->attrs[GTPA_TID])
+			return -EINVAL;
+		pctx = gtp0_pdp_find(gtp, nla_get_u64(info->attrs[GTPA_TID]));
+		break;
+	case GTP_V1:
+		if (!info->attrs[GTPA_I_TEI])
+			return -EINVAL;
+		pctx = gtp1_pdp_find(gtp, nla_get_u64(info->attrs[GTPA_I_TEI]));
+		break;
+
+	default:
+		return -EINVAL;
+	}
+
+	if (pctx == NULL)
+		return -ENOENT;
+
+	if (pctx->gtp_version == GTP_V0)
+		netdev_dbg(dev, "GTPv0-U: deleting tunnel id = %llx (pdp %p)\n",
+			   pctx->u.v0.tid, pctx);
+	else if (pctx->gtp_version == GTP_V1)
+		netdev_dbg(dev, "GTPv1-U: deleting tunnel id = %x/%x (pdp %p)\n",
+			   pctx->u.v1.i_tei, pctx->u.v1.o_tei, pctx);
+
+	hlist_del_rcu(&pctx->hlist_tid);
+	hlist_del_rcu(&pctx->hlist_addr);
+	kfree_rcu(pctx, rcu_head);
+
+	return 0;
+}
+
+static struct genl_family gtp_genl_family = {
+	.id		= GENL_ID_GENERATE,
+	.name		= "gtp",
+	.version	= 0,
+	.hdrsize	= 0,
+	.maxattr	= GTPA_MAX,
+	.netnsok	= true,
+};
+
+static int gtp_genl_fill_info(struct sk_buff *skb, u32 snd_portid, u32 snd_seq,
+			      u32 type, struct pdp_ctx *pctx)
+{
+	void *genlh;
+
+	genlh = genlmsg_put(skb, snd_portid, snd_seq, &gtp_genl_family, 0,
+			    type);
+	if (genlh == NULL)
+		goto nlmsg_failure;
+
+	if (nla_put_u32(skb, GTPA_VERSION, pctx->gtp_version) ||
+	    nla_put_be32(skb, GTPA_SGSN_ADDRESS, pctx->sgsn_addr_ip4.s_addr) ||
+	    nla_put_be32(skb, GTPA_MS_ADDRESS, pctx->ms_addr_ip4.s_addr))
+		goto nla_put_failure;
+
+	switch (pctx->gtp_version) {
+	case GTP_V0:
+		if (nla_put_u64_64bit(skb, GTPA_TID, pctx->u.v0.tid, GTPA_PAD) ||
+		    nla_put_u16(skb, GTPA_FLOW, pctx->u.v0.flow))
+			goto nla_put_failure;
+		break;
+	case GTP_V1:
+		if (nla_put_u32(skb, GTPA_I_TEI, pctx->u.v1.i_tei) ||
+		    nla_put_u32(skb, GTPA_O_TEI, pctx->u.v1.o_tei))
+			goto nla_put_failure;
+		break;
+	}
+	genlmsg_end(skb, genlh);
+	return 0;
+
+nlmsg_failure:
+nla_put_failure:
+	genlmsg_cancel(skb, genlh);
+	return -EMSGSIZE;
+}
+
+static int gtp_genl_get_pdp(struct sk_buff *skb, struct genl_info *info)
+{
+	struct pdp_ctx *pctx = NULL;
+	struct net_device *dev;
+	struct sk_buff *skb2;
+	struct gtp_dev *gtp;
+	u32 gtp_version;
+	struct net *net;
+	int err;
+
+	if (!info->attrs[GTPA_VERSION] ||
+	    !info->attrs[GTPA_LINK])
+		return -EINVAL;
+
+	gtp_version = nla_get_u32(info->attrs[GTPA_VERSION]);
+	switch (gtp_version) {
+	case GTP_V0:
+	case GTP_V1:
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	net = gtp_genl_get_net(sock_net(skb->sk), info->attrs);
+	if (IS_ERR(net))
+		return PTR_ERR(net);
+
+	/* Check if there's an existing gtpX device to configure */
+	dev = gtp_find_dev(net, nla_get_u32(info->attrs[GTPA_LINK]));
+	if (dev == NULL)
+		return -ENODEV;
+
+	gtp = netdev_priv(dev);
+
+	rcu_read_lock();
+	if (gtp_version == GTP_V0 &&
+	    info->attrs[GTPA_TID]) {
+		u64 tid = nla_get_u64(info->attrs[GTPA_TID]);
+
+		pctx = gtp0_pdp_find(gtp, tid);
+	} else if (gtp_version == GTP_V1 &&
+		 info->attrs[GTPA_I_TEI]) {
+		u32 tid = nla_get_u32(info->attrs[GTPA_I_TEI]);
+
+		pctx = gtp1_pdp_find(gtp, tid);
+	} else if (info->attrs[GTPA_MS_ADDRESS]) {
+		__be32 ip = nla_get_be32(info->attrs[GTPA_MS_ADDRESS]);
+
+		pctx = ipv4_pdp_find(gtp, ip);
+	}
+
+	if (pctx == NULL) {
+		err = -ENOENT;
+		goto err_unlock;
+	}
+
+	skb2 = genlmsg_new(NLMSG_GOODSIZE, GFP_ATOMIC);
+	if (skb2 == NULL) {
+		err = -ENOMEM;
+		goto err_unlock;
+	}
+
+	err = gtp_genl_fill_info(skb2, NETLINK_CB(skb).portid,
+				 info->snd_seq, info->nlhdr->nlmsg_type, pctx);
+	if (err < 0)
+		goto err_unlock_free;
+
+	rcu_read_unlock();
+	return genlmsg_unicast(genl_info_net(info), skb2, info->snd_portid);
+
+err_unlock_free:
+	kfree_skb(skb2);
+err_unlock:
+	rcu_read_unlock();
+	return err;
+}
+
+static int gtp_genl_dump_pdp(struct sk_buff *skb,
+				struct netlink_callback *cb)
+{
+	struct gtp_dev *last_gtp = (struct gtp_dev *)cb->args[2], *gtp;
+	struct net *net = sock_net(skb->sk);
+	struct gtp_net *gn = net_generic(net, gtp_net_id);
+	unsigned long tid = cb->args[1];
+	int i, k = cb->args[0], ret;
+	struct pdp_ctx *pctx;
+
+	if (cb->args[4])
+		return 0;
+
+	list_for_each_entry_rcu(gtp, &gn->gtp_dev_list, list) {
+		if (last_gtp && last_gtp != gtp)
+			continue;
+		else
+			last_gtp = NULL;
+
+		for (i = k; i < gtp->hash_size; i++) {
+			hlist_for_each_entry_rcu(pctx, &gtp->tid_hash[i], hlist_tid) {
+				if (tid && tid != pctx->u.tid)
+					continue;
+				else
+					tid = 0;
+
+				ret = gtp_genl_fill_info(skb,
+							 NETLINK_CB(cb->skb).portid,
+							 cb->nlh->nlmsg_seq,
+							 cb->nlh->nlmsg_type, pctx);
+				if (ret < 0) {
+					cb->args[0] = i;
+					cb->args[1] = pctx->u.tid;
+					cb->args[2] = (unsigned long)gtp;
+					goto out;
+				}
+			}
+		}
+	}
+	cb->args[4] = 1;
+out:
+	return skb->len;
+}
+
+static struct nla_policy gtp_genl_policy[GTPA_MAX + 1] = {
+	[GTPA_LINK]		= { .type = NLA_U32, },
+	[GTPA_VERSION]		= { .type = NLA_U32, },
+	[GTPA_TID]		= { .type = NLA_U64, },
+	[GTPA_SGSN_ADDRESS]	= { .type = NLA_U32, },
+	[GTPA_MS_ADDRESS]	= { .type = NLA_U32, },
+	[GTPA_FLOW]		= { .type = NLA_U16, },
+	[GTPA_NET_NS_FD]	= { .type = NLA_U32, },
+	[GTPA_I_TEI]		= { .type = NLA_U32, },
+	[GTPA_O_TEI]		= { .type = NLA_U32, },
+};
+
+static const struct genl_ops gtp_genl_ops[] = {
+	{
+		.cmd = GTP_CMD_NEWPDP,
+		.doit = gtp_genl_new_pdp,
+		.policy = gtp_genl_policy,
+		.flags = GENL_ADMIN_PERM,
+	},
+	{
+		.cmd = GTP_CMD_DELPDP,
+		.doit = gtp_genl_del_pdp,
+		.policy = gtp_genl_policy,
+		.flags = GENL_ADMIN_PERM,
+	},
+	{
+		.cmd = GTP_CMD_GETPDP,
+		.doit = gtp_genl_get_pdp,
+		.dumpit = gtp_genl_dump_pdp,
+		.policy = gtp_genl_policy,
+		.flags = GENL_ADMIN_PERM,
+	},
+};
+
+static int __net_init gtp_net_init(struct net *net)
+{
+	struct gtp_net *gn = net_generic(net, gtp_net_id);
+
+	INIT_LIST_HEAD(&gn->gtp_dev_list);
+	return 0;
+}
+
+static void __net_exit gtp_net_exit(struct net *net)
+{
+	struct gtp_net *gn = net_generic(net, gtp_net_id);
+	struct gtp_dev *gtp;
+	LIST_HEAD(list);
+
+	rtnl_lock();
+	list_for_each_entry(gtp, &gn->gtp_dev_list, list)
+		gtp_dellink(gtp->dev, &list);
+
+	unregister_netdevice_many(&list);
+	rtnl_unlock();
+}
+
+static struct pernet_operations gtp_net_ops = {
+	.init	= gtp_net_init,
+	.exit	= gtp_net_exit,
+	.id	= &gtp_net_id,
+	.size	= sizeof(struct gtp_net),
+};
+
+static int __init gtp_init(void)
+{
+	int err;
+
+	get_random_bytes(&gtp_h_initval, sizeof(gtp_h_initval));
+
+	err = rtnl_link_register(&gtp_link_ops);
+	if (err < 0)
+		goto error_out;
+
+	err = genl_register_family_with_ops(&gtp_genl_family, gtp_genl_ops);
+	if (err < 0)
+		goto unreg_rtnl_link;
+
+	err = register_pernet_subsys(&gtp_net_ops);
+	if (err < 0)
+		goto unreg_genl_family;
+
+	pr_info("GTP module loaded (pdp ctx size %Zd bytes)\n",
+		sizeof(struct pdp_ctx));
+	return 0;
+
+unreg_genl_family:
+	genl_unregister_family(&gtp_genl_family);
+unreg_rtnl_link:
+	rtnl_link_unregister(&gtp_link_ops);
+error_out:
+	pr_err("error loading GTP module loaded\n");
+	return err;
+}
+late_initcall(gtp_init);
+
+static void __exit gtp_fini(void)
+{
+	unregister_pernet_subsys(&gtp_net_ops);
+	genl_unregister_family(&gtp_genl_family);
+	rtnl_link_unregister(&gtp_link_ops);
+
+	pr_info("GTP module unloaded\n");
+}
+module_exit(gtp_fini);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Harald Welte <hwelte@sysmocom.de>");
+MODULE_DESCRIPTION("Interface driver for GTP encapsulated traffic");
+MODULE_ALIAS_RTNL_LINK("gtp");
diff --git a/include/net/gtp.h b/include/net/gtp.h
new file mode 100644
index 0000000..894a37b
--- /dev/null
+++ b/include/net/gtp.h
@@ -0,0 +1,34 @@ 
+#ifndef _GTP_H_
+#define _GTP_H
+
+/* General GTP protocol related definitions. */
+
+#define GTP0_PORT	3386
+#define GTP1U_PORT	2152
+
+#define GTP_TPDU	255
+
+struct gtp0_header {	/* According to GSM TS 09.60. */
+	__u8	flags;
+	__u8	type;
+	__be16	length;
+	__be16	seq;
+	__be16	flow;
+	__u8	number;
+	__u8	spare[3];
+	__be64	tid;
+} __attribute__ ((packed));
+
+struct gtp1_header {	/* According to 3GPP TS 29.060. */
+	__u8	flags;
+	__u8	type;
+	__be16	length;
+	__be32	tid;
+} __attribute__ ((packed));
+
+#define GTP1_F_NPDU	0x01
+#define GTP1_F_SEQ	0x02
+#define GTP1_F_EXTHDR	0x04
+#define GTP1_F_MASK	0x07
+
+#endif
diff --git a/include/uapi/linux/Kbuild b/include/uapi/linux/Kbuild
index 813ffb2e..8bdae34 100644
--- a/include/uapi/linux/Kbuild
+++ b/include/uapi/linux/Kbuild
@@ -141,6 +141,7 @@  header-y += gfs2_ondisk.h
 header-y += gigaset_dev.h
 header-y += gpio.h
 header-y += gsmmux.h
+header-y += gtp.h
 header-y += hdlcdrv.h
 header-y += hdlc.h
 header-y += hdreg.h
diff --git a/include/uapi/linux/gtp.h b/include/uapi/linux/gtp.h
new file mode 100644
index 0000000..ca1054d
--- /dev/null
+++ b/include/uapi/linux/gtp.h
@@ -0,0 +1,33 @@ 
+#ifndef _UAPI_LINUX_GTP_H_
+#define _UAPI_LINUX_GTP_H__
+
+enum gtp_genl_cmds {
+	GTP_CMD_NEWPDP,
+	GTP_CMD_DELPDP,
+	GTP_CMD_GETPDP,
+
+	GTP_CMD_MAX,
+};
+
+enum gtp_version {
+	GTP_V0 = 0,
+	GTP_V1,
+};
+
+enum gtp_attrs {
+	GTPA_UNSPEC = 0,
+	GTPA_LINK,
+	GTPA_VERSION,
+	GTPA_TID,	/* for GTPv0 only */
+	GTPA_SGSN_ADDRESS,
+	GTPA_MS_ADDRESS,
+	GTPA_FLOW,
+	GTPA_NET_NS_FD,
+	GTPA_I_TEI,	/* for GTPv1 only */
+	GTPA_O_TEI,	/* for GTPv1 only */
+	GTPA_PAD,
+	__GTPA_MAX,
+};
+#define GTPA_MAX (__GTPA_MAX + 1)
+
+#endif /* _UAPI_LINUX_GTP_H_ */
diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
index d2d7fd4..bb36bd5 100644
--- a/include/uapi/linux/if_link.h
+++ b/include/uapi/linux/if_link.h
@@ -529,6 +529,16 @@  enum {
 };
 #define IFLA_PPP_MAX (__IFLA_PPP_MAX - 1)
 
+/* GTP section */
+enum {
+	IFLA_GTP_UNSPEC,
+	IFLA_GTP_FD0,
+	IFLA_GTP_FD1,
+	IFLA_GTP_PDP_HASHSIZE,
+	__IFLA_GTP_MAX,
+};
+#define IFLA_GTP_MAX (__IFLA_GTP_MAX - 1)
+
 /* Bonding section */
 
 enum {
diff --git a/include/uapi/linux/udp.h b/include/uapi/linux/udp.h
index 16574ea..2c8180f 100644
--- a/include/uapi/linux/udp.h
+++ b/include/uapi/linux/udp.h
@@ -36,6 +36,7 @@  struct udphdr {
 #define UDP_ENCAP_ESPINUDP_NON_IKE	1 /* draft-ietf-ipsec-nat-t-ike-00/01 */
 #define UDP_ENCAP_ESPINUDP	2 /* draft-ietf-ipsec-udp-encaps-06 */
 #define UDP_ENCAP_L2TPINUDP	3 /* rfc2661 */
-
+#define UDP_ENCAP_GTP0		4 /* GSM TS 09.60 */
+#define UDP_ENCAP_GTP1U		5 /* 3GPP TS 29.060 */
 
 #endif /* _UAPI_LINUX_UDP_H */