lwtunnel: infrastructure for handling light weight tunnels like mpls

Provides infrastructure to parse/dump/store encap information for
light weight tunnels like mpls. Encap information for such tunnels
is associated with fib routes.

This infrastructure is based on previous suggestions from
Eric Biederman to follow the xfrm infrastructure.

Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 187 insertions, 0 deletions

diff --git a/net/Kconfig b/net/Kconfig
index 57a7c5af3175..7021c1bf44d6 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -374,6 +374,13 @@ source "net/caif/Kconfig"
 source "net/ceph/Kconfig"
 source "net/nfc/Kconfig"
 
+config LWTUNNEL
+	bool "Network light weight tunnels"
+	---help---
+	  This feature provides an infrastructure to support light weight
+	  tunnels like mpls. There is no netdevice associated with a light
+	  weight tunnel endpoint. Tunnel encapsulation parameters are stored
+	  with light weight tunnel state associated with fib routes.
 
 endif   # if NET
 
diff --git a/net/core/Makefile b/net/core/Makefile
index fec0856dd6c0..086b01fbe1bd 100644
--- a/net/core/Makefile
+++ b/net/core/Makefile
@@ -23,3 +23,4 @@ obj-$(CONFIG_NETWORK_PHY_TIMESTAMPING) += timestamping.o
 obj-$(CONFIG_NET_PTP_CLASSIFY) += ptp_classifier.o
 obj-$(CONFIG_CGROUP_NET_PRIO) += netprio_cgroup.o
 obj-$(CONFIG_CGROUP_NET_CLASSID) += netclassid_cgroup.o
+obj-$(CONFIG_LWTUNNEL) += lwtunnel.o
diff --git a/net/core/lwtunnel.c b/net/core/lwtunnel.c
new file mode 100644
index 000000000000..d7ae3a235b4b
--- /dev/null
+++ b/net/core/lwtunnel.c
@@ -0,0 +1,179 @@
+/*
+ * lwtunnel	Infrastructure for light weight tunnels like mpls
+ *
+ * Authors:	Roopa Prabhu, <roopa@cumulusnetworks.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.
+ *
+ */
+
+#include <linux/capability.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/skbuff.h>
+#include <linux/netdevice.h>
+#include <linux/lwtunnel.h>
+#include <linux/in.h>
+#include <linux/init.h>
+#include <linux/err.h>
+
+#include <net/lwtunnel.h>
+#include <net/rtnetlink.h>
+
+struct lwtunnel_state *lwtunnel_state_alloc(int encap_len)
+{
+	struct lwtunnel_state *lws;
+
+	lws = kzalloc(sizeof(*lws) + encap_len, GFP_ATOMIC);
+
+	return lws;
+}
+EXPORT_SYMBOL(lwtunnel_state_alloc);
+
+const struct lwtunnel_encap_ops __rcu *
+		lwtun_encaps[LWTUNNEL_ENCAP_MAX + 1] __read_mostly;
+
+int lwtunnel_encap_add_ops(const struct lwtunnel_encap_ops *ops,
+			   unsigned int num)
+{
+	if (num > LWTUNNEL_ENCAP_MAX)
+		return -ERANGE;
+
+	return !cmpxchg((const struct lwtunnel_encap_ops **)
+			&lwtun_encaps[num],
+			NULL, ops) ? 0 : -1;
+}
+EXPORT_SYMBOL(lwtunnel_encap_add_ops);
+
+int lwtunnel_encap_del_ops(const struct lwtunnel_encap_ops *ops,
+			   unsigned int encap_type)
+{
+	int ret;
+
+	if (encap_type == LWTUNNEL_ENCAP_NONE ||
+	    encap_type > LWTUNNEL_ENCAP_MAX)
+		return -ERANGE;
+
+	ret = (cmpxchg((const struct lwtunnel_encap_ops **)
+		       &lwtun_encaps[encap_type],
+		       ops, NULL) == ops) ? 0 : -1;
+
+	synchronize_net();
+
+	return ret;
+}
+EXPORT_SYMBOL(lwtunnel_encap_del_ops);
+
+int lwtunnel_build_state(struct net_device *dev, u16 encap_type,
+			 struct nlattr *encap, struct lwtunnel_state **lws)
+{
+	const struct lwtunnel_encap_ops *ops;
+	int ret = -EINVAL;
+
+	if (encap_type == LWTUNNEL_ENCAP_NONE ||
+	    encap_type > LWTUNNEL_ENCAP_MAX)
+		return ret;
+
+	ret = -EOPNOTSUPP;
+	rcu_read_lock();
+	ops = rcu_dereference(lwtun_encaps[encap_type]);
+	if (likely(ops && ops->build_state))
+		ret = ops->build_state(dev, encap, lws);
+	rcu_read_unlock();
+
+	return ret;
+}
+EXPORT_SYMBOL(lwtunnel_build_state);
+
+int lwtunnel_fill_encap(struct sk_buff *skb, struct lwtunnel_state *lwtstate)
+{
+	const struct lwtunnel_encap_ops *ops;
+	struct nlattr *nest;
+	int ret = -EINVAL;
+
+	if (!lwtstate)
+		return 0;
+
+	if (lwtstate->type == LWTUNNEL_ENCAP_NONE ||
+	    lwtstate->type > LWTUNNEL_ENCAP_MAX)
+		return 0;
+
+	ret = -EOPNOTSUPP;
+	nest = nla_nest_start(skb, RTA_ENCAP);
+	rcu_read_lock();
+	ops = rcu_dereference(lwtun_encaps[lwtstate->type]);
+	if (likely(ops && ops->fill_encap))
+		ret = ops->fill_encap(skb, lwtstate);
+	rcu_read_unlock();
+
+	if (ret)
+		goto nla_put_failure;
+	nla_nest_end(skb, nest);
+	ret = nla_put_u16(skb, RTA_ENCAP_TYPE, lwtstate->type);
+	if (ret)
+		goto nla_put_failure;
+
+	return 0;
+
+nla_put_failure:
+	nla_nest_cancel(skb, nest);
+
+	return (ret == -EOPNOTSUPP ? 0 : ret);
+}
+EXPORT_SYMBOL(lwtunnel_fill_encap);
+
+int lwtunnel_get_encap_size(struct lwtunnel_state *lwtstate)
+{
+	const struct lwtunnel_encap_ops *ops;
+	int ret = 0;
+
+	if (!lwtstate)
+		return 0;
+
+	if (lwtstate->type == LWTUNNEL_ENCAP_NONE ||
+	    lwtstate->type > LWTUNNEL_ENCAP_MAX)
+		return 0;
+
+	rcu_read_lock();
+	ops = rcu_dereference(lwtun_encaps[lwtstate->type]);
+	if (likely(ops && ops->get_encap_size))
+		ret = nla_total_size(ops->get_encap_size(lwtstate));
+	rcu_read_unlock();
+
+	return ret;
+}
+EXPORT_SYMBOL(lwtunnel_get_encap_size);
+
+int lwtunnel_cmp_encap(struct lwtunnel_state *a, struct lwtunnel_state *b)
+{
+	const struct lwtunnel_encap_ops *ops;
+	int ret = 0;
+
+	if (!a && !b)
+		return 0;
+
+	if (!a || !b)
+		return 1;
+
+	if (a->type != b->type)
+		return 1;
+
+	if (a->type == LWTUNNEL_ENCAP_NONE ||
+	    a->type > LWTUNNEL_ENCAP_MAX)
+		return 0;
+
+	rcu_read_lock();
+	ops = rcu_dereference(lwtun_encaps[a->type]);
+	if (likely(ops && ops->cmp_encap))
+		ret = ops->cmp_encap(a, b);
+	rcu_read_unlock();
+
+	return ret;
+}
+EXPORT_SYMBOL(lwtunnel_cmp_encap);