// SPDX-License-Identifier: GPL-2.0-or-later

  /*
   * lwtunnel	Infrastructure for light weight tunnels like mpls
   *
   * Authors:	Roopa Prabhu, <roopa@cumulusnetworks.com>

   */
  
  #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>

  #include <net/ip6_fib.h>

  #include <net/rtnh.h>

  #ifdef CONFIG_MODULES
  
  static const char *lwtunnel_encap_str(enum lwtunnel_encap_types encap_type)
  {
  	/* Only lwt encaps implemented without using an interface for
  	 * the encap need to return a string here.
  	 */
  	switch (encap_type) {
  	case LWTUNNEL_ENCAP_MPLS:
  		return "MPLS";
  	case LWTUNNEL_ENCAP_ILA:
  		return "ILA";

  	case LWTUNNEL_ENCAP_SEG6:
  		return "SEG6";

  	case LWTUNNEL_ENCAP_BPF:
  		return "BPF";

  	case LWTUNNEL_ENCAP_SEG6_LOCAL:
  		return "SEG6LOCAL";

  	case LWTUNNEL_ENCAP_RPL:
  		return "RPL";

  	case LWTUNNEL_ENCAP_IP6:
  	case LWTUNNEL_ENCAP_IP:
  	case LWTUNNEL_ENCAP_NONE:
  	case __LWTUNNEL_ENCAP_MAX:
  		/* should not have got here */
  		WARN_ON(1);
  		break;
  	}
  	return NULL;
  }
  
  #endif /* CONFIG_MODULES */

  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_GPL(lwtunnel_state_alloc);

  static 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_GPL(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_GPL(lwtunnel_encap_del_ops);

  int lwtunnel_build_state(struct net *net, u16 encap_type,

  			 struct nlattr *encap, unsigned int family,

  			 const void *cfg, struct lwtunnel_state **lws,
  			 struct netlink_ext_ack *extack)

  {
  	const struct lwtunnel_encap_ops *ops;

  	bool found = false;

  	int ret = -EINVAL;
  
  	if (encap_type == LWTUNNEL_ENCAP_NONE ||

  	    encap_type > LWTUNNEL_ENCAP_MAX) {
  		NL_SET_ERR_MSG_ATTR(extack, encap,
  				    "Unknown LWT encapsulation type");

  		return ret;

  	}

  
  	ret = -EOPNOTSUPP;
  	rcu_read_lock();
  	ops = rcu_dereference(lwtun_encaps[encap_type]);

  	if (likely(ops && ops->build_state && try_module_get(ops->owner)))

  		found = true;

  	rcu_read_unlock();
  
  	if (found) {

  		ret = ops->build_state(net, encap, family, cfg, lws, extack);

  		if (ret)
  			module_put(ops->owner);

  	} else {
  		/* don't rely on -EOPNOTSUPP to detect match as build_state
  		 * handlers could return it
  		 */

  		NL_SET_ERR_MSG_ATTR(extack, encap,
  				    "LWT encapsulation type not supported");
  	}

  	return ret;
  }

  EXPORT_SYMBOL_GPL(lwtunnel_build_state);

  int lwtunnel_valid_encap_type(u16 encap_type, struct netlink_ext_ack *extack)

  {
  	const struct lwtunnel_encap_ops *ops;
  	int ret = -EINVAL;
  
  	if (encap_type == LWTUNNEL_ENCAP_NONE ||

  	    encap_type > LWTUNNEL_ENCAP_MAX) {
  		NL_SET_ERR_MSG(extack, "Unknown lwt encapsulation type");

  		return ret;

  	}

  
  	rcu_read_lock();
  	ops = rcu_dereference(lwtun_encaps[encap_type]);
  	rcu_read_unlock();

  #ifdef CONFIG_MODULES
  	if (!ops) {
  		const char *encap_type_str = lwtunnel_encap_str(encap_type);
  
  		if (encap_type_str) {

  			__rtnl_unlock();

  			request_module("rtnl-lwt-%s", encap_type_str);

  			rtnl_lock();

  			rcu_read_lock();
  			ops = rcu_dereference(lwtun_encaps[encap_type]);

  			rcu_read_unlock();

  		}
  	}
  #endif

  	ret = ops ? 0 : -EOPNOTSUPP;
  	if (ret < 0)
  		NL_SET_ERR_MSG(extack, "lwt encapsulation type not supported");
  
  	return ret;

  }

  EXPORT_SYMBOL_GPL(lwtunnel_valid_encap_type);

  int lwtunnel_valid_encap_type_attr(struct nlattr *attr, int remaining,
  				   struct netlink_ext_ack *extack)

  {
  	struct rtnexthop *rtnh = (struct rtnexthop *)attr;
  	struct nlattr *nla_entype;
  	struct nlattr *attrs;

  	u16 encap_type;
  	int attrlen;
  
  	while (rtnh_ok(rtnh, remaining)) {
  		attrlen = rtnh_attrlen(rtnh);
  		if (attrlen > 0) {
  			attrs = rtnh_attrs(rtnh);

  			nla_entype = nla_find(attrs, attrlen, RTA_ENCAP_TYPE);
  
  			if (nla_entype) {
  				encap_type = nla_get_u16(nla_entype);

  				if (lwtunnel_valid_encap_type(encap_type,
  							      extack) != 0)

  					return -EOPNOTSUPP;
  			}
  		}
  		rtnh = rtnh_next(rtnh, &remaining);
  	}
  
  	return 0;

  }

  EXPORT_SYMBOL_GPL(lwtunnel_valid_encap_type_attr);

  void lwtstate_free(struct lwtunnel_state *lws)
  {
  	const struct lwtunnel_encap_ops *ops = lwtun_encaps[lws->type];
  
  	if (ops->destroy_state) {
  		ops->destroy_state(lws);
  		kfree_rcu(lws, rcu);
  	} else {
  		kfree(lws);
  	}

  	module_put(ops->owner);

  }

  EXPORT_SYMBOL_GPL(lwtstate_free);

  int lwtunnel_fill_encap(struct sk_buff *skb, struct lwtunnel_state *lwtstate,
  			int encap_attr, int encap_type_attr)

  {
  	const struct lwtunnel_encap_ops *ops;
  	struct nlattr *nest;

  	int ret;

  
  	if (!lwtstate)
  		return 0;
  
  	if (lwtstate->type == LWTUNNEL_ENCAP_NONE ||
  	    lwtstate->type > LWTUNNEL_ENCAP_MAX)
  		return 0;

  	nest = nla_nest_start_noflag(skb, encap_attr);

  	if (!nest)

  		return -EMSGSIZE;
  
  	ret = -EOPNOTSUPP;

  	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, encap_type_attr, 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_GPL(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_GPL(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_GPL(lwtunnel_cmp_encap);

  int lwtunnel_output(struct net *net, struct sock *sk, struct sk_buff *skb)

  {

  	struct dst_entry *dst = skb_dst(skb);

  	const struct lwtunnel_encap_ops *ops;

  	struct lwtunnel_state *lwtstate;

  	int ret = -EINVAL;

  	if (!dst)

  		goto drop;

  	lwtstate = dst->lwtstate;

  
  	if (lwtstate->type == LWTUNNEL_ENCAP_NONE ||
  	    lwtstate->type > LWTUNNEL_ENCAP_MAX)
  		return 0;
  
  	ret = -EOPNOTSUPP;
  	rcu_read_lock();
  	ops = rcu_dereference(lwtun_encaps[lwtstate->type]);
  	if (likely(ops && ops->output))

  		ret = ops->output(net, sk, skb);

  	rcu_read_unlock();
  
  	if (ret == -EOPNOTSUPP)
  		goto drop;
  
  	return ret;
  
  drop:

  	kfree_skb(skb);

  
  	return ret;
  }

  EXPORT_SYMBOL_GPL(lwtunnel_output);

  int lwtunnel_xmit(struct sk_buff *skb)
  {
  	struct dst_entry *dst = skb_dst(skb);
  	const struct lwtunnel_encap_ops *ops;
  	struct lwtunnel_state *lwtstate;
  	int ret = -EINVAL;
  
  	if (!dst)
  		goto drop;
  
  	lwtstate = dst->lwtstate;
  
  	if (lwtstate->type == LWTUNNEL_ENCAP_NONE ||
  	    lwtstate->type > LWTUNNEL_ENCAP_MAX)
  		return 0;
  
  	ret = -EOPNOTSUPP;
  	rcu_read_lock();
  	ops = rcu_dereference(lwtun_encaps[lwtstate->type]);
  	if (likely(ops && ops->xmit))
  		ret = ops->xmit(skb);
  	rcu_read_unlock();
  
  	if (ret == -EOPNOTSUPP)
  		goto drop;
  
  	return ret;
  
  drop:
  	kfree_skb(skb);
  
  	return ret;
  }

  EXPORT_SYMBOL_GPL(lwtunnel_xmit);

  int lwtunnel_input(struct sk_buff *skb)

  {

  	struct dst_entry *dst = skb_dst(skb);

  	const struct lwtunnel_encap_ops *ops;

  	struct lwtunnel_state *lwtstate;

  	int ret = -EINVAL;

  	if (!dst)

  		goto drop;

  	lwtstate = dst->lwtstate;

  
  	if (lwtstate->type == LWTUNNEL_ENCAP_NONE ||
  	    lwtstate->type > LWTUNNEL_ENCAP_MAX)
  		return 0;
  
  	ret = -EOPNOTSUPP;
  	rcu_read_lock();
  	ops = rcu_dereference(lwtun_encaps[lwtstate->type]);
  	if (likely(ops && ops->input))
  		ret = ops->input(skb);
  	rcu_read_unlock();
  
  	if (ret == -EOPNOTSUPP)
  		goto drop;
  
  	return ret;
  
  drop:
  	kfree_skb(skb);
  
  	return ret;
  }

  EXPORT_SYMBOL_GPL(lwtunnel_input);