/* Kernel module to match connection tracking byte counter.
 * GPL (C) 2002 Martin Devera (devik@cdi.cz).
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/bitops.h>
#include <linux/skbuff.h>
#include <linux/math64.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_connbytes.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_acct.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
MODULE_DESCRIPTION("Xtables: Number of packets/bytes per connection matching");
MODULE_ALIAS("ipt_connbytes");
MODULE_ALIAS("ip6t_connbytes");

static bool
connbytes_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
        const struct xt_connbytes_info *sinfo = par->matchinfo;
        const struct nf_conn *ct;
        enum ip_conntrack_info ctinfo;
        u_int64_t what = 0;     /* initialize to make gcc happy */
        u_int64_t bytes = 0;
        u_int64_t pkts = 0;
        const struct nf_conn_acct *acct;
        const struct nf_conn_counter *counters;

        ct = nf_ct_get(skb, &ctinfo);
        if (!ct)
                return false;

        acct = nf_conn_acct_find(ct);
        if (!acct)
                return false;

        counters = acct->counter;
        switch (sinfo->what) {
        case XT_CONNBYTES_PKTS:
                switch (sinfo->direction) {
                case XT_CONNBYTES_DIR_ORIGINAL:
                        what = atomic64_read(&counters[IP_CT_DIR_ORIGINAL].packets);
                        break;
                case XT_CONNBYTES_DIR_REPLY:
                        what = atomic64_read(&counters[IP_CT_DIR_REPLY].packets);
                        break;
                case XT_CONNBYTES_DIR_BOTH:
                        what = atomic64_read(&counters[IP_CT_DIR_ORIGINAL].packets);
                        what += atomic64_read(&counters[IP_CT_DIR_REPLY].packets);
                        break;
                }
                break;
        case XT_CONNBYTES_BYTES:
                switch (sinfo->direction) {
                case XT_CONNBYTES_DIR_ORIGINAL:
                        what = atomic64_read(&counters[IP_CT_DIR_ORIGINAL].bytes);
                        break;
                case XT_CONNBYTES_DIR_REPLY:
                        what = atomic64_read(&counters[IP_CT_DIR_REPLY].bytes);
                        break;
                case XT_CONNBYTES_DIR_BOTH:
                        what = atomic64_read(&counters[IP_CT_DIR_ORIGINAL].bytes);
                        what += atomic64_read(&counters[IP_CT_DIR_REPLY].bytes);
                        break;
                }
                break;
        case XT_CONNBYTES_AVGPKT:
                switch (sinfo->direction) {
                case XT_CONNBYTES_DIR_ORIGINAL:
                        bytes = atomic64_read(&counters[IP_CT_DIR_ORIGINAL].bytes);
                        pkts  = atomic64_read(&counters[IP_CT_DIR_ORIGINAL].packets);
                        break;
                case XT_CONNBYTES_DIR_REPLY:
                        bytes = atomic64_read(&counters[IP_CT_DIR_REPLY].bytes);
                        pkts  = atomic64_read(&counters[IP_CT_DIR_REPLY].packets);
                        break;
                case XT_CONNBYTES_DIR_BOTH:
                        bytes = atomic64_read(&counters[IP_CT_DIR_ORIGINAL].bytes) +
                                atomic64_read(&counters[IP_CT_DIR_REPLY].bytes);
                        pkts  = atomic64_read(&counters[IP_CT_DIR_ORIGINAL].packets) +
                                atomic64_read(&counters[IP_CT_DIR_REPLY].packets);
                        break;
                }
                if (pkts != 0)
                        what = div64_u64(bytes, pkts);
                break;
        }

        if (sinfo->count.to >= sinfo->count.from)
                return what <= sinfo->count.to && what >= sinfo->count.from;
        else /* inverted */
                return what < sinfo->count.to || what > sinfo->count.from;
}

static int connbytes_mt_check(const struct xt_mtchk_param *par)
{
        const struct xt_connbytes_info *sinfo = par->matchinfo;
        int ret;

        if (sinfo->what != XT_CONNBYTES_PKTS &&
            sinfo->what != XT_CONNBYTES_BYTES &&
            sinfo->what != XT_CONNBYTES_AVGPKT)
                return -EINVAL;

        if (sinfo->direction != XT_CONNBYTES_DIR_ORIGINAL &&
            sinfo->direction != XT_CONNBYTES_DIR_REPLY &&
            sinfo->direction != XT_CONNBYTES_DIR_BOTH)
                return -EINVAL;

        ret = nf_ct_netns_get(par->net, par->family);
        if (ret < 0) {
                pr_info_ratelimited("cannot load conntrack support for proto=%u\n",
                                    par->family);
                return ret;
        }

        /*
         * This filter cannot function correctly unless connection tracking
         * accounting is enabled, so complain in the hope that someone notices.
         */
        if (!nf_ct_acct_enabled(par->net)) {
                pr_warn("Forcing CT accounting to be enabled\n");
                nf_ct_set_acct(par->net, true);
        }

        return ret;
}

static void connbytes_mt_destroy(const struct xt_mtdtor_param *par)
{
        nf_ct_netns_put(par->net, par->family);
}

static struct xt_match connbytes_mt_reg __read_mostly = {
        .name       = "connbytes",
        .revision   = 0,
        .family     = NFPROTO_UNSPEC,
        .checkentry = connbytes_mt_check,
        .match      = connbytes_mt,
        .destroy    = connbytes_mt_destroy,
        .matchsize  = sizeof(struct xt_connbytes_info),
        .me         = THIS_MODULE,
};

static int __init connbytes_mt_init(void)
{
        return xt_register_match(&connbytes_mt_reg);
}

static void __exit connbytes_mt_exit(void)
{
        xt_unregister_match(&connbytes_mt_reg);
}

module_init(connbytes_mt_init);
module_exit(connbytes_mt_exit);