act_ipt.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * net/sched/act_ipt.c		iptables target interface
 *
 *TODO: Add other tables. For now we only support the ipv4 table targets
 *
 * Copyright:	Jamal Hadi Salim (2002-13)
 */

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/skbuff.h>
#include <linux/rtnetlink.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <net/netlink.h>
#include <net/pkt_sched.h>
#include <linux/tc_act/tc_ipt.h>
#include <net/tc_act/tc_ipt.h>
#include <net/tc_wrapper.h>
#include <net/ip.h>

#include <linux/netfilter_ipv4/ip_tables.h>


static struct tc_action_ops act_ipt_ops;
static struct tc_action_ops act_xt_ops;

static int ipt_init_target(struct net *net, struct xt_entry_target *t,
			   char *table, unsigned int hook)
{
	struct xt_tgchk_param par;
	struct xt_target *target;
	struct ipt_entry e = {};
	int ret = 0;

	target = xt_request_find_target(AF_INET, t->u.user.name,
					t->u.user.revision);
	if (IS_ERR(target))
		return PTR_ERR(target);

	t->u.kernel.target = target;
	memset(&par, 0, sizeof(par));
	par.net       = net;
	par.table     = table;
	par.entryinfo = &e;
	par.target    = target;
	par.targinfo  = t->data;
	par.hook_mask = 1 << hook;
	par.family    = NFPROTO_IPV4;

	ret = xt_check_target(&par, t->u.target_size - sizeof(*t), 0, false);
	if (ret < 0) {
		module_put(t->u.kernel.target->me);
		return ret;
	}
	return 0;
}

static void ipt_destroy_target(struct xt_entry_target *t, struct net *net)
{
	struct xt_tgdtor_param par = {
		.target   = t->u.kernel.target,
		.targinfo = t->data,
		.family   = NFPROTO_IPV4,
		.net      = net,
	};
	if (par.target->destroy != NULL)
		par.target->destroy(&par);
	module_put(par.target->me);
}

static void tcf_ipt_release(struct tc_action *a)
{
	struct tcf_ipt *ipt = to_ipt(a);

	if (ipt->tcfi_t) {
		ipt_destroy_target(ipt->tcfi_t, a->idrinfo->net);
		kfree(ipt->tcfi_t);
	}
	kfree(ipt->tcfi_tname);
}

static const struct nla_policy ipt_policy[TCA_IPT_MAX + 1] = {
	[TCA_IPT_TABLE]	= { .type = NLA_STRING, .len = IFNAMSIZ },
	[TCA_IPT_HOOK]	= NLA_POLICY_RANGE(NLA_U32, NF_INET_PRE_ROUTING,
					   NF_INET_NUMHOOKS),
	[TCA_IPT_INDEX]	= { .type = NLA_U32 },
	[TCA_IPT_TARG]	= { .len = sizeof(struct xt_entry_target) },
};

static int __tcf_ipt_init(struct net *net, unsigned int id, struct nlattr *nla,
			  struct nlattr *est, struct tc_action **a,
			  const struct tc_action_ops *ops,
			  struct tcf_proto *tp, u32 flags)
{
	struct tc_action_net *tn = net_generic(net, id);
	bool bind = flags & TCA_ACT_FLAGS_BIND;
	struct nlattr *tb[TCA_IPT_MAX + 1];
	struct tcf_ipt *ipt;
	struct xt_entry_target *td, *t;
	char *tname;
	bool exists = false;
	int ret = 0, err;
	u32 hook = 0;
	u32 index = 0;

	if (nla == NULL)
		return -EINVAL;

	err = nla_parse_nested_deprecated(tb, TCA_IPT_MAX, nla, ipt_policy,
					  NULL);
	if (err < 0)
		return err;

	if (tb[TCA_IPT_INDEX] != NULL)
		index = nla_get_u32(tb[TCA_IPT_INDEX]);

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

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

	td = (struct xt_entry_target *)nla_data(tb[TCA_IPT_TARG]);
	if (nla_len(tb[TCA_IPT_TARG]) != td->u.target_size) {
		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, ops, bind,
				     false, flags);
		if (ret) {
			tcf_idr_cleanup(tn, index);
			return ret;
		}
		ret = ACT_P_CREATED;
	} else {
		if (bind)/* dont override defaults */
			return 0;

		if (!(flags & TCA_ACT_FLAGS_REPLACE)) {
			tcf_idr_release(*a, bind);
			return -EEXIST;
		}
	}

	err = -EINVAL;
	hook = nla_get_u32(tb[TCA_IPT_HOOK]);
	switch (hook) {
	case NF_INET_PRE_ROUTING:
		break;
	case NF_INET_POST_ROUTING:
		break;
	default:
		goto err1;
	}

	if (tb[TCA_IPT_TABLE]) {
		/* mangle only for now */
		if (nla_strcmp(tb[TCA_IPT_TABLE], "mangle"))
			goto err1;
	}

	tname = kstrdup("mangle", GFP_KERNEL);
	if (unlikely(!tname))
		goto err1;

	t = kmemdup(td, td->u.target_size, GFP_KERNEL);
	if (unlikely(!t))
		goto err2;

	err = ipt_init_target(net, t, tname, hook);
	if (err < 0)
		goto err3;

	ipt = to_ipt(*a);

	spin_lock_bh(&ipt->tcf_lock);
	if (ret != ACT_P_CREATED) {
		ipt_destroy_target(ipt->tcfi_t, net);
		kfree(ipt->tcfi_tname);
		kfree(ipt->tcfi_t);
	}
	ipt->tcfi_tname = tname;
	ipt->tcfi_t     = t;
	ipt->tcfi_hook  = hook;
	spin_unlock_bh(&ipt->tcf_lock);
	return ret;

err3:
	kfree(t);
err2:
	kfree(tname);
err1:
	tcf_idr_release(*a, bind);
	return err;
}

static int tcf_ipt_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)
{
	return __tcf_ipt_init(net, act_ipt_ops.net_id, nla, est,
			      a, &act_ipt_ops, tp, flags);
}

static int tcf_xt_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)
{
	return __tcf_ipt_init(net, act_xt_ops.net_id, nla, est,
			      a, &act_xt_ops, tp, flags);
}

static bool tcf_ipt_act_check(struct sk_buff *skb)
{
	const struct iphdr *iph;
	unsigned int nhoff, len;

	if (!pskb_may_pull(skb, sizeof(struct iphdr)))
		return false;

	nhoff = skb_network_offset(skb);
	iph = ip_hdr(skb);
	if (iph->ihl < 5 || iph->version != 4)
		return false;

	len = skb_ip_totlen(skb);
	if (skb->len < nhoff + len || len < (iph->ihl * 4u))
		return false;

	return pskb_may_pull(skb, iph->ihl * 4u);
}

TC_INDIRECT_SCOPE int tcf_ipt_act(struct sk_buff *skb,
				  const struct tc_action *a,
				  struct tcf_result *res)
{
	char saved_cb[sizeof_field(struct sk_buff, cb)];
	int ret = 0, result = 0;
	struct tcf_ipt *ipt = to_ipt(a);
	struct xt_action_param par;
	struct nf_hook_state state = {
		.net	= dev_net(skb->dev),
		.in	= skb->dev,
		.hook	= ipt->tcfi_hook,
		.pf	= NFPROTO_IPV4,
	};

	if (skb_protocol(skb, false) != htons(ETH_P_IP))
		return TC_ACT_UNSPEC;

	if (skb_unclone(skb, GFP_ATOMIC))
		return TC_ACT_UNSPEC;

	if (!tcf_ipt_act_check(skb))
		return TC_ACT_UNSPEC;

	if (state.hook == NF_INET_POST_ROUTING) {
		if (!skb_dst(skb))
			return TC_ACT_UNSPEC;

		state.out = skb->dev;
	}

	memcpy(saved_cb, skb->cb, sizeof(saved_cb));

	spin_lock(&ipt->tcf_lock);

	tcf_lastuse_update(&ipt->tcf_tm);
	bstats_update(&ipt->tcf_bstats, skb);

	/* yes, we have to worry about both in and out dev
	 * worry later - danger - this API seems to have changed
	 * from earlier kernels
	 */
	par.state    = &state;
	par.target   = ipt->tcfi_t->u.kernel.target;
	par.targinfo = ipt->tcfi_t->data;

	memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));

	ret = par.target->target(skb, &par);

	switch (ret) {
	case NF_ACCEPT:
		result = TC_ACT_OK;
		break;
	case NF_DROP:
		result = TC_ACT_SHOT;
		ipt->tcf_qstats.drops++;
		break;
	case XT_CONTINUE:
		result = TC_ACT_PIPE;
		break;
	default:
		net_notice_ratelimited("tc filter: Bogus netfilter code %d assume ACCEPT\n",
				       ret);
		result = TC_ACT_OK;
		break;
	}
	spin_unlock(&ipt->tcf_lock);

	memcpy(skb->cb, saved_cb, sizeof(skb->cb));

	return result;

}

static int tcf_ipt_dump(struct sk_buff *skb, struct tc_action *a, int bind,
			int ref)
{
	unsigned char *b = skb_tail_pointer(skb);
	struct tcf_ipt *ipt = to_ipt(a);
	struct xt_entry_target *t;
	struct tcf_t tm;
	struct tc_cnt c;

	/* for simple targets kernel size == user size
	 * user name = target name
	 * for foolproof you need to not assume this
	 */

	spin_lock_bh(&ipt->tcf_lock);
	t = kmemdup(ipt->tcfi_t, ipt->tcfi_t->u.user.target_size, GFP_ATOMIC);
	if (unlikely(!t))
		goto nla_put_failure;

	c.bindcnt = atomic_read(&ipt->tcf_bindcnt) - bind;
	c.refcnt = refcount_read(&ipt->tcf_refcnt) - ref;
	strcpy(t->u.user.name, ipt->tcfi_t->u.kernel.target->name);

	if (nla_put(skb, TCA_IPT_TARG, ipt->tcfi_t->u.user.target_size, t) ||
	    nla_put_u32(skb, TCA_IPT_INDEX, ipt->tcf_index) ||
	    nla_put_u32(skb, TCA_IPT_HOOK, ipt->tcfi_hook) ||
	    nla_put(skb, TCA_IPT_CNT, sizeof(struct tc_cnt), &c) ||
	    nla_put_string(skb, TCA_IPT_TABLE, ipt->tcfi_tname))
		goto nla_put_failure;

	tcf_tm_dump(&tm, &ipt->tcf_tm);
	if (nla_put_64bit(skb, TCA_IPT_TM, sizeof(tm), &tm, TCA_IPT_PAD))
		goto nla_put_failure;

	spin_unlock_bh(&ipt->tcf_lock);
	kfree(t);
	return skb->len;

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

static struct tc_action_ops act_ipt_ops = {
	.kind		=	"ipt",
	.id		=	TCA_ID_IPT,
	.owner		=	THIS_MODULE,
	.act		=	tcf_ipt_act,
	.dump		=	tcf_ipt_dump,
	.cleanup	=	tcf_ipt_release,
	.init		=	tcf_ipt_init,
	.size		=	sizeof(struct tcf_ipt),
};

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

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

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

static struct pernet_operations ipt_net_ops = {
	.init = ipt_init_net,
	.exit_batch = ipt_exit_net,
	.id   = &act_ipt_ops.net_id,
	.size = sizeof(struct tc_action_net),
};

static struct tc_action_ops act_xt_ops = {
	.kind		=	"xt",
	.id		=	TCA_ID_XT,
	.owner		=	THIS_MODULE,
	.act		=	tcf_ipt_act,
	.dump		=	tcf_ipt_dump,
	.cleanup	=	tcf_ipt_release,
	.init		=	tcf_xt_init,
	.size		=	sizeof(struct tcf_ipt),
};

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

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

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

static struct pernet_operations xt_net_ops = {
	.init = xt_init_net,
	.exit_batch = xt_exit_net,
	.id   = &act_xt_ops.net_id,
	.size = sizeof(struct tc_action_net),
};

MODULE_AUTHOR("Jamal Hadi Salim(2002-13)");
MODULE_DESCRIPTION("Iptables target actions");
MODULE_LICENSE("GPL");
MODULE_ALIAS("act_xt");

static int __init ipt_init_module(void)
{
	int ret1, ret2;

	ret1 = tcf_register_action(&act_xt_ops, &xt_net_ops);
	if (ret1 < 0)
		pr_err("Failed to load xt action\n");

	ret2 = tcf_register_action(&act_ipt_ops, &ipt_net_ops);
	if (ret2 < 0)
		pr_err("Failed to load ipt action\n");

	if (ret1 < 0 && ret2 < 0) {
		return ret1;
	} else
		return 0;
}

static void __exit ipt_cleanup_module(void)
{
	tcf_unregister_action(&act_ipt_ops, &ipt_net_ops);
	tcf_unregister_action(&act_xt_ops, &xt_net_ops);
}

module_init(ipt_init_module);
module_exit(ipt_cleanup_module);