// SPDX-License-Identifier: GPL-2.0

  #include <linux/kernel.h>
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/skbuff.h>
  #include <linux/netfilter.h>

  #include <linux/mutex.h>

  #include <net/sock.h>
  
  #include "nf_internals.h"
  
  /* Sockopts only registered and called from user context, so
     net locking would be overkill.  Also, [gs]etsockopt calls may
     sleep. */

  static DEFINE_MUTEX(nf_sockopt_mutex);

  static LIST_HEAD(nf_sockopts);
  
  /* Do exclusive ranges overlap? */
  static inline int overlap(int min1, int max1, int min2, int max2)
  {
  	return max1 > min2 && min1 < max2;
  }
  
  /* Functions to register sockopt ranges (exclusive). */
  int nf_register_sockopt(struct nf_sockopt_ops *reg)
  {

  	struct nf_sockopt_ops *ops;

  	int ret = 0;

  	mutex_lock(&nf_sockopt_mutex);

  	list_for_each_entry(ops, &nf_sockopts, list) {

  		if (ops->pf == reg->pf

  		    && (overlap(ops->set_optmin, ops->set_optmax,

  				reg->set_optmin, reg->set_optmax)

  			|| overlap(ops->get_optmin, ops->get_optmax,

  				   reg->get_optmin, reg->get_optmax))) {

  			pr_debug("nf_sock overlap: %u-%u/%u-%u v %u-%u/%u-%u
  ",

  				ops->set_optmin, ops->set_optmax,
  				ops->get_optmin, ops->get_optmax,

  				reg->set_optmin, reg->set_optmax,
  				reg->get_optmin, reg->get_optmax);
  			ret = -EBUSY;
  			goto out;
  		}
  	}
  
  	list_add(&reg->list, &nf_sockopts);
  out:

  	mutex_unlock(&nf_sockopt_mutex);

  	return ret;
  }
  EXPORT_SYMBOL(nf_register_sockopt);
  
  void nf_unregister_sockopt(struct nf_sockopt_ops *reg)
  {

  	mutex_lock(&nf_sockopt_mutex);

  	list_del(&reg->list);

  	mutex_unlock(&nf_sockopt_mutex);

  }
  EXPORT_SYMBOL(nf_unregister_sockopt);

  static struct nf_sockopt_ops *nf_sockopt_find(struct sock *sk, u_int8_t pf,

  		int val, int get)

  {

  	struct nf_sockopt_ops *ops;

  	mutex_lock(&nf_sockopt_mutex);

  	list_for_each_entry(ops, &nf_sockopts, list) {

  		if (ops->pf == pf) {

  			if (!try_module_get(ops->owner))
  				goto out_nosup;

  			if (get) {

  				if (val >= ops->get_optmin &&
  						val < ops->get_optmax)

  					goto out;

  			} else {

  				if (val >= ops->set_optmin &&
  						val < ops->set_optmax)

  					goto out;

  			}

  			module_put(ops->owner);

  		}
  	}

  out_nosup:
  	ops = ERR_PTR(-ENOPROTOOPT);
  out:

  	mutex_unlock(&nf_sockopt_mutex);

  	return ops;
  }

  int nf_setsockopt(struct sock *sk, u_int8_t pf, int val, sockptr_t opt,

  		  unsigned int len)

  {
  	struct nf_sockopt_ops *ops;
  	int ret;

  	ops = nf_sockopt_find(sk, pf, val, 0);

  	if (IS_ERR(ops))
  		return PTR_ERR(ops);

  	ret = ops->set(sk, val, opt, len);

  	module_put(ops->owner);

  	return ret;
  }

  EXPORT_SYMBOL(nf_setsockopt);

  int nf_getsockopt(struct sock *sk, u_int8_t pf, int val, char __user *opt,
  		  int *len)

  {

  	struct nf_sockopt_ops *ops;
  	int ret;
  
  	ops = nf_sockopt_find(sk, pf, val, 1);
  	if (IS_ERR(ops))
  		return PTR_ERR(ops);
  	ret = ops->get(sk, val, opt, len);
  	module_put(ops->owner);
  	return ret;

  }
  EXPORT_SYMBOL(nf_getsockopt);