// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * (C) 2011 Pablo Neira Ayuso <pablo@netfilter.org>
 * (C) 2011 Intra2net AG <https://www.intra2net.com>
 */
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/atomic.h>
#include <linux/refcount.h>
#include <linux/netlink.h>
#include <linux/rculist.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <net/netlink.h>
#include <net/sock.h>
#include <net/netns/generic.h>

#include <linux/netfilter.h>
#include <linux/netfilter/nfnetlink.h>
#include <linux/netfilter/nfnetlink_acct.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
MODULE_DESCRIPTION("nfacct: Extended Netfilter accounting infrastructure");

struct nf_acct {
        atomic64_t              pkts;
        atomic64_t              bytes;
        unsigned long           flags;
        struct list_head        head;
        refcount_t              refcnt;
        char                    name[NFACCT_NAME_MAX];
        struct rcu_head         rcu_head;
        char                    data[];
};

struct nfacct_filter {
        u32 value;
        u32 mask;
};

struct nfnl_acct_net {
        struct list_head        nfnl_acct_list;
};

static unsigned int nfnl_acct_net_id __read_mostly;

static inline struct nfnl_acct_net *nfnl_acct_pernet(struct net *net)
{
        return net_generic(net, nfnl_acct_net_id);
}

#define NFACCT_F_QUOTA (NFACCT_F_QUOTA_PKTS | NFACCT_F_QUOTA_BYTES)
#define NFACCT_OVERQUOTA_BIT    2       /* NFACCT_F_OVERQUOTA */

static int nfnl_acct_new(struct sk_buff *skb, const struct nfnl_info *info,
                         const struct nlattr * const tb[])
{
        struct nfnl_acct_net *nfnl_acct_net = nfnl_acct_pernet(info->net);
        struct nf_acct *nfacct, *matching = NULL;
        unsigned int size = 0;
        char *acct_name;
        u32 flags = 0;

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

        acct_name = nla_data(tb[NFACCT_NAME]);
        if (strlen(acct_name) == 0)
                return -EINVAL;

        list_for_each_entry(nfacct, &nfnl_acct_net->nfnl_acct_list, head) {
                if (strncmp(nfacct->name, acct_name, NFACCT_NAME_MAX) != 0)
                        continue;

                if (info->nlh->nlmsg_flags & NLM_F_EXCL)
                        return -EEXIST;

                matching = nfacct;
                break;
        }

        if (matching) {
                if (info->nlh->nlmsg_flags & NLM_F_REPLACE) {
                        /* reset counters if you request a replacement. */
                        atomic64_set(&matching->pkts, 0);
                        atomic64_set(&matching->bytes, 0);
                        smp_mb__before_atomic();
                        /* reset overquota flag if quota is enabled. */
                        if ((matching->flags & NFACCT_F_QUOTA))
                                clear_bit(NFACCT_OVERQUOTA_BIT,
                                          &matching->flags);
                        return 0;
                }
                return -EBUSY;
        }

        if (tb[NFACCT_FLAGS]) {
                flags = ntohl(nla_get_be32(tb[NFACCT_FLAGS]));
                if (flags & ~NFACCT_F_QUOTA)
                        return -EOPNOTSUPP;
                if ((flags & NFACCT_F_QUOTA) == NFACCT_F_QUOTA)
                        return -EINVAL;
                if (flags & NFACCT_F_OVERQUOTA)
                        return -EINVAL;
                if ((flags & NFACCT_F_QUOTA) && !tb[NFACCT_QUOTA])
                        return -EINVAL;

                size += sizeof(u64);
        }

        nfacct = kzalloc(sizeof(struct nf_acct) + size, GFP_KERNEL);
        if (nfacct == NULL)
                return -ENOMEM;

        if (flags & NFACCT_F_QUOTA) {
                u64 *quota = (u64 *)nfacct->data;

                *quota = be64_to_cpu(nla_get_be64(tb[NFACCT_QUOTA]));
                nfacct->flags = flags;
        }

        nla_strscpy(nfacct->name, tb[NFACCT_NAME], NFACCT_NAME_MAX);

        if (tb[NFACCT_BYTES]) {
                atomic64_set(&nfacct->bytes,
                             be64_to_cpu(nla_get_be64(tb[NFACCT_BYTES])));
        }
        if (tb[NFACCT_PKTS]) {
                atomic64_set(&nfacct->pkts,
                             be64_to_cpu(nla_get_be64(tb[NFACCT_PKTS])));
        }
        refcount_set(&nfacct->refcnt, 1);
        list_add_tail_rcu(&nfacct->head, &nfnl_acct_net->nfnl_acct_list);
        return 0;
}

static int
nfnl_acct_fill_info(struct sk_buff *skb, u32 portid, u32 seq, u32 type,
                   int event, struct nf_acct *acct)
{
        struct nlmsghdr *nlh;
        unsigned int flags = portid ? NLM_F_MULTI : 0;
        u64 pkts, bytes;
        u32 old_flags;

        event = nfnl_msg_type(NFNL_SUBSYS_ACCT, event);
        nlh = nfnl_msg_put(skb, portid, seq, event, flags, AF_UNSPEC,
                           NFNETLINK_V0, 0);
        if (!nlh)
                goto nlmsg_failure;

        if (nla_put_string(skb, NFACCT_NAME, acct->name))
                goto nla_put_failure;

        old_flags = acct->flags;
        if (type == NFNL_MSG_ACCT_GET_CTRZERO) {
                pkts = atomic64_xchg(&acct->pkts, 0);
                bytes = atomic64_xchg(&acct->bytes, 0);
                smp_mb__before_atomic();
                if (acct->flags & NFACCT_F_QUOTA)
                        clear_bit(NFACCT_OVERQUOTA_BIT, &acct->flags);
        } else {
                pkts = atomic64_read(&acct->pkts);
                bytes = atomic64_read(&acct->bytes);
        }
        if (nla_put_be64(skb, NFACCT_PKTS, cpu_to_be64(pkts),
                         NFACCT_PAD) ||
            nla_put_be64(skb, NFACCT_BYTES, cpu_to_be64(bytes),
                         NFACCT_PAD) ||
            nla_put_be32(skb, NFACCT_USE, htonl(refcount_read(&acct->refcnt))))
                goto nla_put_failure;
        if (acct->flags & NFACCT_F_QUOTA) {
                u64 *quota = (u64 *)acct->data;

                if (nla_put_be32(skb, NFACCT_FLAGS, htonl(old_flags)) ||
                    nla_put_be64(skb, NFACCT_QUOTA, cpu_to_be64(*quota),
                                 NFACCT_PAD))
                        goto nla_put_failure;
        }
        nlmsg_end(skb, nlh);
        return skb->len;

nlmsg_failure:
nla_put_failure:
        nlmsg_cancel(skb, nlh);
        return -1;
}

static int
nfnl_acct_dump(struct sk_buff *skb, struct netlink_callback *cb)
{
        struct net *net = sock_net(skb->sk);
        struct nfnl_acct_net *nfnl_acct_net = nfnl_acct_pernet(net);
        struct nf_acct *cur, *last;
        const struct nfacct_filter *filter = cb->data;

        if (cb->args[2])
                return 0;

        last = (struct nf_acct *)cb->args[1];
        if (cb->args[1])
                cb->args[1] = 0;

        rcu_read_lock();
        list_for_each_entry_rcu(cur, &nfnl_acct_net->nfnl_acct_list, head) {
                if (last) {
                        if (cur != last)
                                continue;

                        last = NULL;
                }

                if (filter && (cur->flags & filter->mask) != filter->value)
                        continue;

                if (nfnl_acct_fill_info(skb, NETLINK_CB(cb->skb).portid,
                                       cb->nlh->nlmsg_seq,
                                       NFNL_MSG_TYPE(cb->nlh->nlmsg_type),
                                       NFNL_MSG_ACCT_NEW, cur) < 0) {
                        cb->args[1] = (unsigned long)cur;
                        break;
                }
        }
        if (!cb->args[1])
                cb->args[2] = 1;
        rcu_read_unlock();
        return skb->len;
}

static int nfnl_acct_done(struct netlink_callback *cb)
{
        kfree(cb->data);
        return 0;
}

static const struct nla_policy filter_policy[NFACCT_FILTER_MAX + 1] = {
        [NFACCT_FILTER_MASK]    = { .type = NLA_U32 },
        [NFACCT_FILTER_VALUE]   = { .type = NLA_U32 },
};

static int nfnl_acct_start(struct netlink_callback *cb)
{
        const struct nlattr *const attr = cb->data;
        struct nlattr *tb[NFACCT_FILTER_MAX + 1];
        struct nfacct_filter *filter;
        int err;

        if (!attr)
                return 0;

        err = nla_parse_nested_deprecated(tb, NFACCT_FILTER_MAX, attr,
                                          filter_policy, NULL);
        if (err < 0)
                return err;

        if (!tb[NFACCT_FILTER_MASK] || !tb[NFACCT_FILTER_VALUE])
                return -EINVAL;

        filter = kzalloc_obj(struct nfacct_filter);
        if (!filter)
                return -ENOMEM;

        filter->mask = ntohl(nla_get_be32(tb[NFACCT_FILTER_MASK]));
        filter->value = ntohl(nla_get_be32(tb[NFACCT_FILTER_VALUE]));
        cb->data = filter;

        return 0;
}

static int nfnl_acct_get(struct sk_buff *skb, const struct nfnl_info *info,
                         const struct nlattr * const tb[])
{
        struct nfnl_acct_net *nfnl_acct_net = nfnl_acct_pernet(info->net);
        int ret = -ENOENT;
        struct nf_acct *cur;
        char *acct_name;

        if (info->nlh->nlmsg_flags & NLM_F_DUMP) {
                struct netlink_dump_control c = {
                        .dump = nfnl_acct_dump,
                        .start = nfnl_acct_start,
                        .done = nfnl_acct_done,
                        .data = (void *)tb[NFACCT_FILTER],
                };

                return netlink_dump_start(info->sk, skb, info->nlh, &c);
        }

        if (!tb[NFACCT_NAME])
                return -EINVAL;
        acct_name = nla_data(tb[NFACCT_NAME]);

        list_for_each_entry(cur, &nfnl_acct_net->nfnl_acct_list, head) {
                struct sk_buff *skb2;

                if (strncmp(cur->name, acct_name, NFACCT_NAME_MAX)!= 0)
                        continue;

                skb2 = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
                if (skb2 == NULL) {
                        ret = -ENOMEM;
                        break;
                }

                ret = nfnl_acct_fill_info(skb2, NETLINK_CB(skb).portid,
                                          info->nlh->nlmsg_seq,
                                          NFNL_MSG_TYPE(info->nlh->nlmsg_type),
                                          NFNL_MSG_ACCT_NEW, cur);
                if (ret <= 0) {
                        kfree_skb(skb2);
                        break;
                }

                ret = nfnetlink_unicast(skb2, info->net, NETLINK_CB(skb).portid);
                break;
        }

        return ret;
}

/* try to delete object, fail if it is still in use. */
static int nfnl_acct_try_del(struct nf_acct *cur)
{
        int ret = 0;

        /* We want to avoid races with nfnl_acct_put. So only when the current
         * refcnt is 1, we decrease it to 0.
         */
        if (refcount_dec_if_one(&cur->refcnt)) {
                /* We are protected by nfnl mutex. */
                list_del_rcu(&cur->head);
                kfree_rcu(cur, rcu_head);
        } else {
                ret = -EBUSY;
        }
        return ret;
}

static int nfnl_acct_del(struct sk_buff *skb, const struct nfnl_info *info,
                         const struct nlattr * const tb[])
{
        struct nfnl_acct_net *nfnl_acct_net = nfnl_acct_pernet(info->net);
        struct nf_acct *cur, *tmp;
        int ret = -ENOENT;
        char *acct_name;

        if (!tb[NFACCT_NAME]) {
                list_for_each_entry_safe(cur, tmp, &nfnl_acct_net->nfnl_acct_list, head)
                        nfnl_acct_try_del(cur);

                return 0;
        }
        acct_name = nla_data(tb[NFACCT_NAME]);

        list_for_each_entry(cur, &nfnl_acct_net->nfnl_acct_list, head) {
                if (strncmp(cur->name, acct_name, NFACCT_NAME_MAX) != 0)
                        continue;

                ret = nfnl_acct_try_del(cur);
                if (ret < 0)
                        return ret;

                break;
        }
        return ret;
}

static const struct nla_policy nfnl_acct_policy[NFACCT_MAX+1] = {
        [NFACCT_NAME] = { .type = NLA_NUL_STRING, .len = NFACCT_NAME_MAX-1 },
        [NFACCT_BYTES] = { .type = NLA_U64 },
        [NFACCT_PKTS] = { .type = NLA_U64 },
        [NFACCT_FLAGS] = { .type = NLA_U32 },
        [NFACCT_QUOTA] = { .type = NLA_U64 },
        [NFACCT_FILTER] = {.type = NLA_NESTED },
};

static const struct nfnl_callback nfnl_acct_cb[NFNL_MSG_ACCT_MAX] = {
        [NFNL_MSG_ACCT_NEW] = {
                .call           = nfnl_acct_new,
                .type           = NFNL_CB_MUTEX,
                .attr_count     = NFACCT_MAX,
                .policy         = nfnl_acct_policy
        },
        [NFNL_MSG_ACCT_GET] = {
                .call           = nfnl_acct_get,
                .type           = NFNL_CB_MUTEX,
                .attr_count     = NFACCT_MAX,
                .policy         = nfnl_acct_policy
        },
        [NFNL_MSG_ACCT_GET_CTRZERO] = {
                .call           = nfnl_acct_get,
                .type           = NFNL_CB_MUTEX,
                .attr_count     = NFACCT_MAX,
                .policy         = nfnl_acct_policy
        },
        [NFNL_MSG_ACCT_DEL] = {
                .call           = nfnl_acct_del,
                .type           = NFNL_CB_MUTEX,
                .attr_count     = NFACCT_MAX,
                .policy         = nfnl_acct_policy
        },
};

static const struct nfnetlink_subsystem nfnl_acct_subsys = {
        .name                           = "acct",
        .subsys_id                      = NFNL_SUBSYS_ACCT,
        .cb_count                       = NFNL_MSG_ACCT_MAX,
        .cb                             = nfnl_acct_cb,
};

MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_ACCT);

struct nf_acct *nfnl_acct_find_get(struct net *net, const char *acct_name)
{
        struct nfnl_acct_net *nfnl_acct_net = nfnl_acct_pernet(net);
        struct nf_acct *cur, *acct = NULL;

        rcu_read_lock();
        list_for_each_entry_rcu(cur, &nfnl_acct_net->nfnl_acct_list, head) {
                if (strncmp(cur->name, acct_name, NFACCT_NAME_MAX)!= 0)
                        continue;

                if (!try_module_get(THIS_MODULE))
                        goto err;

                if (!refcount_inc_not_zero(&cur->refcnt)) {
                        module_put(THIS_MODULE);
                        goto err;
                }

                acct = cur;
                break;
        }
err:
        rcu_read_unlock();
        return acct;
}
EXPORT_SYMBOL_GPL(nfnl_acct_find_get);

void nfnl_acct_put(struct nf_acct *acct)
{
        if (refcount_dec_and_test(&acct->refcnt))
                kfree_rcu(acct, rcu_head);

        module_put(THIS_MODULE);
}
EXPORT_SYMBOL_GPL(nfnl_acct_put);

void nfnl_acct_update(const struct sk_buff *skb, struct nf_acct *nfacct)
{
        atomic64_inc(&nfacct->pkts);
        atomic64_add(skb->len, &nfacct->bytes);
}
EXPORT_SYMBOL_GPL(nfnl_acct_update);

static void nfnl_overquota_report(struct net *net, struct nf_acct *nfacct)
{
        int ret;
        struct sk_buff *skb;

        skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_ATOMIC);
        if (skb == NULL)
                return;

        ret = nfnl_acct_fill_info(skb, 0, 0, NFNL_MSG_ACCT_OVERQUOTA, 0,
                                  nfacct);
        if (ret <= 0) {
                kfree_skb(skb);
                return;
        }
        nfnetlink_broadcast(net, skb, 0, NFNLGRP_ACCT_QUOTA, GFP_ATOMIC);
}

int nfnl_acct_overquota(struct net *net, struct nf_acct *nfacct)
{
        u64 now;
        u64 *quota;
        int ret = NFACCT_UNDERQUOTA;

        /* no place here if we don't have a quota */
        if (!(nfacct->flags & NFACCT_F_QUOTA))
                return NFACCT_NO_QUOTA;

        quota = (u64 *)nfacct->data;
        now = (nfacct->flags & NFACCT_F_QUOTA_PKTS) ?
               atomic64_read(&nfacct->pkts) : atomic64_read(&nfacct->bytes);

        ret = now > *quota;

        if (now >= *quota &&
            !test_and_set_bit(NFACCT_OVERQUOTA_BIT, &nfacct->flags)) {
                nfnl_overquota_report(net, nfacct);
        }

        return ret;
}
EXPORT_SYMBOL_GPL(nfnl_acct_overquota);

static int __net_init nfnl_acct_net_init(struct net *net)
{
        INIT_LIST_HEAD(&nfnl_acct_pernet(net)->nfnl_acct_list);

        return 0;
}

static void __net_exit nfnl_acct_net_exit(struct net *net)
{
        struct nfnl_acct_net *nfnl_acct_net = nfnl_acct_pernet(net);
        struct nf_acct *cur, *tmp;

        list_for_each_entry_safe(cur, tmp, &nfnl_acct_net->nfnl_acct_list, head) {
                list_del_rcu(&cur->head);

                if (refcount_dec_and_test(&cur->refcnt))
                        kfree_rcu(cur, rcu_head);
        }
}

static struct pernet_operations nfnl_acct_ops = {
        .init   = nfnl_acct_net_init,
        .exit   = nfnl_acct_net_exit,
        .id     = &nfnl_acct_net_id,
        .size   = sizeof(struct nfnl_acct_net),
};

static int __init nfnl_acct_init(void)
{
        int ret;

        ret = register_pernet_subsys(&nfnl_acct_ops);
        if (ret < 0) {
                pr_err("nfnl_acct_init: failed to register pernet ops\n");
                goto err_out;
        }

        ret = nfnetlink_subsys_register(&nfnl_acct_subsys);
        if (ret < 0) {
                pr_err("nfnl_acct_init: cannot register with nfnetlink.\n");
                goto cleanup_pernet;
        }
        return 0;

cleanup_pernet:
        unregister_pernet_subsys(&nfnl_acct_ops);
err_out:
        return ret;
}

static void __exit nfnl_acct_exit(void)
{
        nfnetlink_subsys_unregister(&nfnl_acct_subsys);
        unregister_pernet_subsys(&nfnl_acct_ops);
}

module_init(nfnl_acct_init);
module_exit(nfnl_acct_exit);