// 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\n",
                                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);