pfcp: add PFCP module

Packet Forwarding Control Protocol (PFCP) is a 3GPP Protocol
used between the control plane and the user plane function.
It is specified in TS 29.244[1].

Note that this module is not designed to support this Protocol
in the kernel space. There is no support for parsing any PFCP messages.
There is no API that could be used by any userspace daemon.
Basically it does not support PFCP. This protocol is sophisticated
and there is no need for implementing it in the kernel. The purpose
of this module is to allow users to setup software and hardware offload
of PFCP packets using tc tool.

When user requests to create a PFCP device, a new socket is created.
The socket is set up with port number 8805 which is specific for
PFCP [29.244 4.2.2]. This allow to receive PFCP request messages,
response messages use other ports.

Note that only one PFCP netdev can be created.

Only IPv4 is supported at this time.

[1] https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=3111

Signed-off-by: Wojciech Drewek <wojciech.drewek@intel.com>
Signed-off-by: Marcin Szycik <marcin.szycik@linux.intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/Kconfig

@@ -290,6 +290,19 @@ config GTP
 	  To compile this drivers as a module, choose M here: the module
 	  will be called gtp.
 
+config PFCP
+	tristate "Packet Forwarding Control Protocol (PFCP)"
+	depends on INET
+	select NET_UDP_TUNNEL
+	help
+	  This allows one to create PFCP virtual interfaces that allows to
+	  set up software and hardware offload of PFCP packets.
+	  Note that this module does not support PFCP protocol in the kernel space.
+	  There is no support for parsing any PFCP messages.
+
+	  To compile this drivers as a module, choose M here: the module
+	  will be called pfcp.
+
 config AMT
 	tristate "Automatic Multicast Tunneling (AMT)"
 	depends on INET && IP_MULTICAST

drivers/net/Makefile

@@ -38,6 +38,7 @@ obj-$(CONFIG_GENEVE) += geneve.o
 obj-$(CONFIG_BAREUDP) += bareudp.o
 obj-$(CONFIG_GTP) += gtp.o
 obj-$(CONFIG_NLMON) += nlmon.o
+obj-$(CONFIG_PFCP) += pfcp.o
 obj-$(CONFIG_NET_VRF) += vrf.o
 obj-$(CONFIG_VSOCKMON) += vsockmon.o
 obj-$(CONFIG_MHI_NET) += mhi_net.o

drivers/net/pfcp.c

@@ -0,0 +1,223 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * PFCP according to 3GPP TS 29.244
+ *
+ * Copyright (C) 2022, Intel Corporation.
+ */
+
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <linux/rculist.h>
+#include <linux/skbuff.h>
+#include <linux/types.h>
+
+#include <net/udp.h>
+#include <net/udp_tunnel.h>
+#include <net/pfcp.h>
+
+struct pfcp_dev {
+	struct list_head	list;
+
+	struct socket		*sock;
+	struct net_device	*dev;
+	struct net		*net;
+};
+
+static unsigned int pfcp_net_id __read_mostly;
+
+struct pfcp_net {
+	struct list_head	pfcp_dev_list;
+};
+
+static void pfcp_del_sock(struct pfcp_dev *pfcp)
+{
+	udp_tunnel_sock_release(pfcp->sock);
+	pfcp->sock = NULL;
+}
+
+static void pfcp_dev_uninit(struct net_device *dev)
+{
+	struct pfcp_dev *pfcp = netdev_priv(dev);
+
+	pfcp_del_sock(pfcp);
+}
+
+static int pfcp_dev_init(struct net_device *dev)
+{
+	struct pfcp_dev *pfcp = netdev_priv(dev);
+
+	pfcp->dev = dev;
+
+	return 0;
+}
+
+static const struct net_device_ops pfcp_netdev_ops = {
+	.ndo_init		= pfcp_dev_init,
+	.ndo_uninit		= pfcp_dev_uninit,
+	.ndo_get_stats64	= dev_get_tstats64,
+};
+
+static const struct device_type pfcp_type = {
+	.name = "pfcp",
+};
+
+static void pfcp_link_setup(struct net_device *dev)
+{
+	dev->netdev_ops = &pfcp_netdev_ops;
+	dev->needs_free_netdev = true;
+	SET_NETDEV_DEVTYPE(dev, &pfcp_type);
+
+	dev->hard_header_len = 0;
+	dev->addr_len = 0;
+
+	dev->type = ARPHRD_NONE;
+	dev->flags = IFF_POINTOPOINT | IFF_NOARP | IFF_MULTICAST;
+	dev->priv_flags |= IFF_NO_QUEUE;
+
+	netif_keep_dst(dev);
+}
+
+static struct socket *pfcp_create_sock(struct pfcp_dev *pfcp)
+{
+	struct udp_tunnel_sock_cfg tuncfg = {};
+	struct udp_port_cfg udp_conf = {
+		.local_ip.s_addr	= htonl(INADDR_ANY),
+		.family			= AF_INET,
+	};
+	struct net *net = pfcp->net;
+	struct socket *sock;
+	int err;
+
+	udp_conf.local_udp_port = htons(PFCP_PORT);
+
+	err = udp_sock_create(net, &udp_conf, &sock);
+	if (err)
+		return ERR_PTR(err);
+
+	setup_udp_tunnel_sock(net, sock, &tuncfg);
+
+	return sock;
+}
+
+static int pfcp_add_sock(struct pfcp_dev *pfcp)
+{
+	pfcp->sock = pfcp_create_sock(pfcp);
+
+	return PTR_ERR_OR_ZERO(pfcp->sock);
+}
+
+static int pfcp_newlink(struct net *net, struct net_device *dev,
+			struct nlattr *tb[], struct nlattr *data[],
+			struct netlink_ext_ack *extack)
+{
+	struct pfcp_dev *pfcp = netdev_priv(dev);
+	struct pfcp_net *pn;
+	int err;
+
+	pfcp->net = net;
+
+	err = pfcp_add_sock(pfcp);
+	if (err) {
+		netdev_dbg(dev, "failed to add pfcp socket %d\n", err);
+		goto exit_err;
+	}
+
+	err = register_netdevice(dev);
+	if (err) {
+		netdev_dbg(dev, "failed to register pfcp netdev %d\n", err);
+		goto exit_del_pfcp_sock;
+	}
+
+	pn = net_generic(dev_net(dev), pfcp_net_id);
+	list_add_rcu(&pfcp->list, &pn->pfcp_dev_list);
+
+	netdev_dbg(dev, "registered new PFCP interface\n");
+
+	return 0;
+
+exit_del_pfcp_sock:
+	pfcp_del_sock(pfcp);
+exit_err:
+	pfcp->net = NULL;
+	return err;
+}
+
+static void pfcp_dellink(struct net_device *dev, struct list_head *head)
+{
+	struct pfcp_dev *pfcp = netdev_priv(dev);
+
+	list_del_rcu(&pfcp->list);
+	unregister_netdevice_queue(dev, head);
+}
+
+static struct rtnl_link_ops pfcp_link_ops __read_mostly = {
+	.kind		= "pfcp",
+	.priv_size	= sizeof(struct pfcp_dev),
+	.setup		= pfcp_link_setup,
+	.newlink	= pfcp_newlink,
+	.dellink	= pfcp_dellink,
+};
+
+static int __net_init pfcp_net_init(struct net *net)
+{
+	struct pfcp_net *pn = net_generic(net, pfcp_net_id);
+
+	INIT_LIST_HEAD(&pn->pfcp_dev_list);
+	return 0;
+}
+
+static void __net_exit pfcp_net_exit(struct net *net)
+{
+	struct pfcp_net *pn = net_generic(net, pfcp_net_id);
+	struct pfcp_dev *pfcp;
+	LIST_HEAD(list);
+
+	rtnl_lock();
+	list_for_each_entry(pfcp, &pn->pfcp_dev_list, list)
+		pfcp_dellink(pfcp->dev, &list);
+
+	unregister_netdevice_many(&list);
+	rtnl_unlock();
+}
+
+static struct pernet_operations pfcp_net_ops = {
+	.init	= pfcp_net_init,
+	.exit	= pfcp_net_exit,
+	.id	= &pfcp_net_id,
+	.size	= sizeof(struct pfcp_net),
+};
+
+static int __init pfcp_init(void)
+{
+	int err;
+
+	err = register_pernet_subsys(&pfcp_net_ops);
+	if (err)
+		goto exit_err;
+
+	err = rtnl_link_register(&pfcp_link_ops);
+	if (err)
+		goto exit_unregister_subsys;
+	return 0;
+
+exit_unregister_subsys:
+	unregister_pernet_subsys(&pfcp_net_ops);
+exit_err:
+	pr_err("loading PFCP module failed: err %d\n", err);
+	return err;
+}
+late_initcall(pfcp_init);
+
+static void __exit pfcp_exit(void)
+{
+	rtnl_link_unregister(&pfcp_link_ops);
+	unregister_pernet_subsys(&pfcp_net_ops);
+
+	pr_info("PFCP module unloaded\n");
+}
+module_exit(pfcp_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Wojciech Drewek <wojciech.drewek@intel.com>");
+MODULE_DESCRIPTION("Interface driver for PFCP encapsulated traffic");
+MODULE_ALIAS_RTNL_LINK("pfcp");

include/net/pfcp.h

@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _PFCP_H_
+#define _PFCP_H_
+
+#include <linux/netdevice.h>
+#include <linux/string.h>
+#include <linux/types.h>
+
+#define PFCP_PORT 8805
+
+static inline bool netif_is_pfcp(const struct net_device *dev)
+{
+	return dev->rtnl_link_ops &&
+	       !strcmp(dev->rtnl_link_ops->kind, "pfcp");
+}
+
+#endif