// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2016 Pablo Neira Ayuso <pablo@netfilter.org>
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/atomic.h>
#include <linux/netlink.h>
#include <linux/netfilter.h>
#include <linux/netfilter/nf_tables.h>
#include <net/netfilter/nf_tables.h>

struct nft_quota {
        atomic64_t      quota;
        unsigned long   flags;
        atomic64_t      *consumed;
};

static inline bool nft_overquota(struct nft_quota *priv,
                                 const struct sk_buff *skb,
                                 bool *report)
{
        u64 consumed = atomic64_add_return(skb->len, priv->consumed);
        u64 quota = atomic64_read(&priv->quota);

        if (report)
                *report = consumed >= quota;

        return consumed > quota;
}

static inline bool nft_quota_invert(struct nft_quota *priv)
{
        return priv->flags & NFT_QUOTA_F_INV;
}

static inline void nft_quota_do_eval(struct nft_quota *priv,
                                     struct nft_regs *regs,
                                     const struct nft_pktinfo *pkt)
{
        if (nft_overquota(priv, pkt->skb, NULL) ^ nft_quota_invert(priv))
                regs->verdict.code = NFT_BREAK;
}

static const struct nla_policy nft_quota_policy[NFTA_QUOTA_MAX + 1] = {
        [NFTA_QUOTA_BYTES]      = { .type = NLA_U64 },
        [NFTA_QUOTA_FLAGS]      = { .type = NLA_U32 },
        [NFTA_QUOTA_CONSUMED]   = { .type = NLA_U64 },
};

#define NFT_QUOTA_DEPLETED_BIT  1       /* From NFT_QUOTA_F_DEPLETED. */

static void nft_quota_obj_eval(struct nft_object *obj,
                               struct nft_regs *regs,
                               const struct nft_pktinfo *pkt)
{
        struct nft_quota *priv = nft_obj_data(obj);
        bool overquota, report;

        overquota = nft_overquota(priv, pkt->skb, &report);
        if (overquota ^ nft_quota_invert(priv))
                regs->verdict.code = NFT_BREAK;

        if (report &&
            !test_and_set_bit(NFT_QUOTA_DEPLETED_BIT, &priv->flags))
                nft_obj_notify(nft_net(pkt), obj->key.table, obj, 0, 0,
                               NFT_MSG_NEWOBJ, 0, nft_pf(pkt), 0, GFP_ATOMIC);
}

static int nft_quota_do_init(const struct nlattr * const tb[],
                             struct nft_quota *priv)
{
        unsigned long flags = 0;
        u64 quota, consumed = 0;

        if (!tb[NFTA_QUOTA_BYTES])
                return -EINVAL;

        quota = be64_to_cpu(nla_get_be64(tb[NFTA_QUOTA_BYTES]));
        if (quota > S64_MAX)
                return -EOVERFLOW;

        if (tb[NFTA_QUOTA_CONSUMED]) {
                consumed = be64_to_cpu(nla_get_be64(tb[NFTA_QUOTA_CONSUMED]));
                if (consumed > quota)
                        return -EINVAL;
        }

        if (tb[NFTA_QUOTA_FLAGS]) {
                flags = ntohl(nla_get_be32(tb[NFTA_QUOTA_FLAGS]));
                if (flags & ~NFT_QUOTA_F_INV)
                        return -EINVAL;
                if (flags & NFT_QUOTA_F_DEPLETED)
                        return -EOPNOTSUPP;
        }

        priv->consumed = kmalloc_obj(*priv->consumed, GFP_KERNEL_ACCOUNT);
        if (!priv->consumed)
                return -ENOMEM;

        atomic64_set(&priv->quota, quota);
        priv->flags = flags;
        atomic64_set(priv->consumed, consumed);

        return 0;
}

static void nft_quota_do_destroy(const struct nft_ctx *ctx,
                                 struct nft_quota *priv)
{
        kfree(priv->consumed);
}

static int nft_quota_obj_init(const struct nft_ctx *ctx,
                              const struct nlattr * const tb[],
                              struct nft_object *obj)
{
        struct nft_quota *priv = nft_obj_data(obj);

        return nft_quota_do_init(tb, priv);
}

static void nft_quota_obj_update(struct nft_object *obj,
                                 struct nft_object *newobj)
{
        struct nft_quota *newpriv = nft_obj_data(newobj);
        struct nft_quota *priv = nft_obj_data(obj);
        u64 newquota;

        newquota = atomic64_read(&newpriv->quota);
        atomic64_set(&priv->quota, newquota);
        priv->flags = newpriv->flags;
}

static int nft_quota_do_dump(struct sk_buff *skb, struct nft_quota *priv,
                             bool reset)
{
        u64 consumed, consumed_cap, quota;
        u32 flags = priv->flags;

        /* Since we unconditionally increment consumed quota for each packet
         * that we see, don't go over the quota boundary in what we send to
         * userspace.
         */
        if (reset) {
                consumed = atomic64_xchg(priv->consumed, 0);
                clear_bit(NFT_QUOTA_DEPLETED_BIT, &priv->flags);
        } else {
                consumed = atomic64_read(priv->consumed);
        }
        quota = atomic64_read(&priv->quota);
        if (consumed >= quota) {
                consumed_cap = quota;
                flags |= NFT_QUOTA_F_DEPLETED;
        } else {
                consumed_cap = consumed;
        }

        if (nla_put_be64(skb, NFTA_QUOTA_BYTES, cpu_to_be64(quota),
                         NFTA_QUOTA_PAD) ||
            nla_put_be64(skb, NFTA_QUOTA_CONSUMED, cpu_to_be64(consumed_cap),
                         NFTA_QUOTA_PAD) ||
            nla_put_be32(skb, NFTA_QUOTA_FLAGS, htonl(flags)))
                goto nla_put_failure;

        return 0;

nla_put_failure:
        return -1;
}

static int nft_quota_obj_dump(struct sk_buff *skb, struct nft_object *obj,
                              bool reset)
{
        struct nft_quota *priv = nft_obj_data(obj);

        return nft_quota_do_dump(skb, priv, reset);
}

static void nft_quota_obj_destroy(const struct nft_ctx *ctx,
                                  struct nft_object *obj)
{
        struct nft_quota *priv = nft_obj_data(obj);

        return nft_quota_do_destroy(ctx, priv);
}

static struct nft_object_type nft_quota_obj_type;
static const struct nft_object_ops nft_quota_obj_ops = {
        .type           = &nft_quota_obj_type,
        .size           = sizeof(struct nft_quota),
        .init           = nft_quota_obj_init,
        .destroy        = nft_quota_obj_destroy,
        .eval           = nft_quota_obj_eval,
        .dump           = nft_quota_obj_dump,
        .update         = nft_quota_obj_update,
};

static struct nft_object_type nft_quota_obj_type __read_mostly = {
        .type           = NFT_OBJECT_QUOTA,
        .ops            = &nft_quota_obj_ops,
        .maxattr        = NFTA_QUOTA_MAX,
        .policy         = nft_quota_policy,
        .owner          = THIS_MODULE,
};

static void nft_quota_eval(const struct nft_expr *expr,
                           struct nft_regs *regs,
                           const struct nft_pktinfo *pkt)
{
        struct nft_quota *priv = nft_expr_priv(expr);

        nft_quota_do_eval(priv, regs, pkt);
}

static int nft_quota_init(const struct nft_ctx *ctx,
                          const struct nft_expr *expr,
                          const struct nlattr * const tb[])
{
        struct nft_quota *priv = nft_expr_priv(expr);

        return nft_quota_do_init(tb, priv);
}

static int nft_quota_dump(struct sk_buff *skb,
                          const struct nft_expr *expr, bool reset)
{
        struct nft_quota *priv = nft_expr_priv(expr);

        return nft_quota_do_dump(skb, priv, reset);
}

static void nft_quota_destroy(const struct nft_ctx *ctx,
                              const struct nft_expr *expr)
{
        struct nft_quota *priv = nft_expr_priv(expr);

        return nft_quota_do_destroy(ctx, priv);
}

static int nft_quota_clone(struct nft_expr *dst, const struct nft_expr *src, gfp_t gfp)
{
        struct nft_quota *priv_dst = nft_expr_priv(dst);
        struct nft_quota *priv_src = nft_expr_priv(src);

        priv_dst->quota = priv_src->quota;
        priv_dst->flags = priv_src->flags;

        priv_dst->consumed = kmalloc_obj(*priv_dst->consumed, gfp);
        if (!priv_dst->consumed)
                return -ENOMEM;

        *priv_dst->consumed = *priv_src->consumed;

        return 0;
}

static struct nft_expr_type nft_quota_type;
static const struct nft_expr_ops nft_quota_ops = {
        .type           = &nft_quota_type,
        .size           = NFT_EXPR_SIZE(sizeof(struct nft_quota)),
        .eval           = nft_quota_eval,
        .init           = nft_quota_init,
        .destroy        = nft_quota_destroy,
        .clone          = nft_quota_clone,
        .dump           = nft_quota_dump,
        .reduce         = NFT_REDUCE_READONLY,
};

static struct nft_expr_type nft_quota_type __read_mostly = {
        .name           = "quota",
        .ops            = &nft_quota_ops,
        .policy         = nft_quota_policy,
        .maxattr        = NFTA_QUOTA_MAX,
        .flags          = NFT_EXPR_STATEFUL,
        .owner          = THIS_MODULE,
};

static int __init nft_quota_module_init(void)
{
        int err;

        err = nft_register_obj(&nft_quota_obj_type);
        if (err < 0)
                return err;

        err = nft_register_expr(&nft_quota_type);
        if (err < 0)
                goto err1;

        return 0;
err1:
        nft_unregister_obj(&nft_quota_obj_type);
        return err;
}

static void __exit nft_quota_module_exit(void)
{
        nft_unregister_expr(&nft_quota_type);
        nft_unregister_obj(&nft_quota_obj_type);
}

module_init(nft_quota_module_init);
module_exit(nft_quota_module_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
MODULE_ALIAS_NFT_EXPR("quota");
MODULE_ALIAS_NFT_OBJ(NFT_OBJECT_QUOTA);
MODULE_DESCRIPTION("Netfilter nftables quota module");