root/net/sched/act_simple.c
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * net/sched/act_simple.c       Simple example of an action
 *
 * Authors:     Jamal Hadi Salim (2005-8)
 */

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/rtnetlink.h>
#include <net/netlink.h>
#include <net/pkt_sched.h>
#include <net/pkt_cls.h>
#include <net/tc_wrapper.h>

#include <linux/tc_act/tc_defact.h>
#include <net/tc_act/tc_defact.h>

static struct tc_action_ops act_simp_ops;

#define SIMP_MAX_DATA   32
TC_INDIRECT_SCOPE int tcf_simp_act(struct sk_buff *skb,
                                   const struct tc_action *a,
                                   struct tcf_result *res)
{
        struct tcf_defact *d = to_defact(a);

        spin_lock(&d->tcf_lock);
        tcf_lastuse_update(&d->tcf_tm);
        bstats_update(&d->tcf_bstats, skb);

        /* print policy string followed by _ then packet count
         * Example if this was the 3rd packet and the string was "hello"
         * then it would look like "hello_3" (without quotes)
         */
        pr_info("simple: %s_%llu\n",
                (char *)d->tcfd_defdata,
                u64_stats_read(&d->tcf_bstats.packets));
        spin_unlock(&d->tcf_lock);
        return d->tcf_action;
}

static void tcf_simp_release(struct tc_action *a)
{
        struct tcf_defact *d = to_defact(a);
        kfree(d->tcfd_defdata);
}

static int alloc_defdata(struct tcf_defact *d, const struct nlattr *defdata)
{
        d->tcfd_defdata = kzalloc(SIMP_MAX_DATA, GFP_KERNEL);
        if (unlikely(!d->tcfd_defdata))
                return -ENOMEM;
        nla_strscpy(d->tcfd_defdata, defdata, SIMP_MAX_DATA);
        return 0;
}

static int reset_policy(struct tc_action *a, const struct nlattr *defdata,
                        struct tc_defact *p, struct tcf_proto *tp,
                        struct netlink_ext_ack *extack)
{
        struct tcf_chain *goto_ch = NULL;
        struct tcf_defact *d;
        int err;

        err = tcf_action_check_ctrlact(p->action, tp, &goto_ch, extack);
        if (err < 0)
                return err;
        d = to_defact(a);
        spin_lock_bh(&d->tcf_lock);
        goto_ch = tcf_action_set_ctrlact(a, p->action, goto_ch);
        nla_strscpy(d->tcfd_defdata, defdata, SIMP_MAX_DATA);
        spin_unlock_bh(&d->tcf_lock);
        if (goto_ch)
                tcf_chain_put_by_act(goto_ch);
        return 0;
}

static const struct nla_policy simple_policy[TCA_DEF_MAX + 1] = {
        [TCA_DEF_PARMS] = { .len = sizeof(struct tc_defact) },
        [TCA_DEF_DATA]  = { .type = NLA_STRING, .len = SIMP_MAX_DATA },
};

static int tcf_simp_init(struct net *net, struct nlattr *nla,
                         struct nlattr *est, struct tc_action **a,
                         struct tcf_proto *tp, u32 flags,
                         struct netlink_ext_ack *extack)
{
        struct tc_action_net *tn = net_generic(net, act_simp_ops.net_id);
        bool bind = flags & TCA_ACT_FLAGS_BIND;
        struct nlattr *tb[TCA_DEF_MAX + 1];
        struct tcf_chain *goto_ch = NULL;
        struct tc_defact *parm;
        struct tcf_defact *d;
        bool exists = false;
        int ret = 0, err;
        u32 index;

        if (nla == NULL)
                return -EINVAL;

        err = nla_parse_nested_deprecated(tb, TCA_DEF_MAX, nla, simple_policy,
                                          NULL);
        if (err < 0)
                return err;

        if (tb[TCA_DEF_PARMS] == NULL)
                return -EINVAL;

        parm = nla_data(tb[TCA_DEF_PARMS]);
        index = parm->index;
        err = tcf_idr_check_alloc(tn, &index, a, bind);
        if (err < 0)
                return err;
        exists = err;
        if (exists && bind)
                return ACT_P_BOUND;

        if (tb[TCA_DEF_DATA] == NULL) {
                if (exists)
                        tcf_idr_release(*a, bind);
                else
                        tcf_idr_cleanup(tn, index);
                return -EINVAL;
        }

        if (!exists) {
                ret = tcf_idr_create(tn, index, est, a,
                                     &act_simp_ops, bind, false, flags);
                if (ret) {
                        tcf_idr_cleanup(tn, index);
                        return ret;
                }

                d = to_defact(*a);
                err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch,
                                               extack);
                if (err < 0)
                        goto release_idr;

                err = alloc_defdata(d, tb[TCA_DEF_DATA]);
                if (err < 0)
                        goto put_chain;

                tcf_action_set_ctrlact(*a, parm->action, goto_ch);
                ret = ACT_P_CREATED;
        } else {
                if (!(flags & TCA_ACT_FLAGS_REPLACE)) {
                        err = -EEXIST;
                        goto release_idr;
                }

                err = reset_policy(*a, tb[TCA_DEF_DATA], parm, tp, extack);
                if (err)
                        goto release_idr;
        }

        return ret;
put_chain:
        if (goto_ch)
                tcf_chain_put_by_act(goto_ch);
release_idr:
        tcf_idr_release(*a, bind);
        return err;
}

static int tcf_simp_dump(struct sk_buff *skb, struct tc_action *a,
                         int bind, int ref)
{
        unsigned char *b = skb_tail_pointer(skb);
        struct tcf_defact *d = to_defact(a);
        struct tc_defact opt = {
                .index   = d->tcf_index,
                .refcnt  = refcount_read(&d->tcf_refcnt) - ref,
                .bindcnt = atomic_read(&d->tcf_bindcnt) - bind,
        };
        struct tcf_t t;

        spin_lock_bh(&d->tcf_lock);
        opt.action = d->tcf_action;
        if (nla_put(skb, TCA_DEF_PARMS, sizeof(opt), &opt) ||
            nla_put_string(skb, TCA_DEF_DATA, d->tcfd_defdata))
                goto nla_put_failure;

        tcf_tm_dump(&t, &d->tcf_tm);
        if (nla_put_64bit(skb, TCA_DEF_TM, sizeof(t), &t, TCA_DEF_PAD))
                goto nla_put_failure;
        spin_unlock_bh(&d->tcf_lock);

        return skb->len;

nla_put_failure:
        spin_unlock_bh(&d->tcf_lock);
        nlmsg_trim(skb, b);
        return -1;
}

static struct tc_action_ops act_simp_ops = {
        .kind           =       "simple",
        .id             =       TCA_ID_SIMP,
        .owner          =       THIS_MODULE,
        .act            =       tcf_simp_act,
        .dump           =       tcf_simp_dump,
        .cleanup        =       tcf_simp_release,
        .init           =       tcf_simp_init,
        .size           =       sizeof(struct tcf_defact),
};
MODULE_ALIAS_NET_ACT("simple");

static __net_init int simp_init_net(struct net *net)
{
        struct tc_action_net *tn = net_generic(net, act_simp_ops.net_id);

        return tc_action_net_init(net, tn, &act_simp_ops);
}

static void __net_exit simp_exit_net(struct list_head *net_list)
{
        tc_action_net_exit(net_list, act_simp_ops.net_id);
}

static struct pernet_operations simp_net_ops = {
        .init = simp_init_net,
        .exit_batch = simp_exit_net,
        .id   = &act_simp_ops.net_id,
        .size = sizeof(struct tc_action_net),
};

MODULE_AUTHOR("Jamal Hadi Salim(2005)");
MODULE_DESCRIPTION("Simple example action");
MODULE_LICENSE("GPL");

static int __init simp_init_module(void)
{
        int ret = tcf_register_action(&act_simp_ops, &simp_net_ops);
        if (!ret)
                pr_info("Simple TC action Loaded\n");
        return ret;
}

static void __exit simp_cleanup_module(void)
{
        tcf_unregister_action(&act_simp_ops, &simp_net_ops);
}

module_init(simp_init_module);
module_exit(simp_cleanup_module);