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

static unsigned int simp_net_id;
static struct tc_action_ops act_simp_ops;

#define SIMP_MAX_DATA	32
static 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_%d\n",
	       (char *)d->tcfd_defdata, 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_strlcpy(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);
	memset(d->tcfd_defdata, 0, SIMP_MAX_DATA);
	nla_strlcpy(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,
			 int ovr, int bind, bool rtnl_held,
			 struct tcf_proto *tp, struct netlink_ext_ack *extack)
{
	struct tc_action_net *tn = net_generic(net, simp_net_id);
	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;

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

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

	if (!exists) {
		ret = tcf_idr_create(tn, parm->index, est, a,
				     &act_simp_ops, bind, false);
		if (ret) {
			tcf_idr_cleanup(tn, parm->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 (!ovr) {
			err = -EEXIST;
			goto release_idr;
		}

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

	if (ret == ACT_P_CREATED)
		tcf_idr_insert(tn, *a);
	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 int tcf_simp_walker(struct net *net, struct sk_buff *skb,
			   struct netlink_callback *cb, int type,
			   const struct tc_action_ops *ops,
			   struct netlink_ext_ack *extack)
{
	struct tc_action_net *tn = net_generic(net, simp_net_id);

	return tcf_generic_walker(tn, skb, cb, type, ops, extack);
}

static int tcf_simp_search(struct net *net, struct tc_action **a, u32 index)
{
	struct tc_action_net *tn = net_generic(net, simp_net_id);

	return tcf_idr_search(tn, a, index);
}

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,
	.walk		=	tcf_simp_walker,
	.lookup		=	tcf_simp_search,
	.size		=	sizeof(struct tcf_defact),
};

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

	return tc_action_net_init(tn, &act_simp_ops);
}

static void __net_exit simp_exit_net(struct list_head *net_list)
{
	tc_action_net_exit(net_list, simp_net_id);
}

static struct pernet_operations simp_net_ops = {
	.init = simp_init_net,
	.exit_batch = simp_exit_net,
	.id   = &simp_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);