1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * net/sched/act_skbmod.c  skb data modifier
  4 *
  5 * Copyright (c) 2016 Jamal Hadi Salim <jhs@mojatatu.com>
  6*/
  7
  8#include <linux/module.h>
  9#include <linux/if_arp.h>
 10#include <linux/init.h>
 11#include <linux/kernel.h>
 12#include <linux/skbuff.h>
 13#include <linux/rtnetlink.h>
 14#include <net/inet_ecn.h>
 15#include <net/netlink.h>
 16#include <net/pkt_sched.h>
 17#include <net/pkt_cls.h>
 18#include <net/tc_wrapper.h>
 19
 20#include <linux/tc_act/tc_skbmod.h>
 21#include <net/tc_act/tc_skbmod.h>
 22
 23static struct tc_action_ops act_skbmod_ops;
 24
 25TC_INDIRECT_SCOPE int tcf_skbmod_act(struct sk_buff *skb,
 26				     const struct tc_action *a,
 27				     struct tcf_result *res)
 28{
 29	struct tcf_skbmod *d = to_skbmod(a);
 30	int action, max_edit_len, err;
 31	struct tcf_skbmod_params *p;
 32	u64 flags;
 33
 34	tcf_lastuse_update(&d->tcf_tm);
 35	bstats_update(this_cpu_ptr(d->common.cpu_bstats), skb);
 36
 37	action = READ_ONCE(d->tcf_action);
 38	if (unlikely(action == TC_ACT_SHOT))
 39		goto drop;
 40
 41	max_edit_len = skb_mac_header_len(skb);
 42	p = rcu_dereference_bh(d->skbmod_p);
 43	flags = p->flags;
 44
 45	/* tcf_skbmod_init() guarantees "flags" to be one of the following:
 46	 *	1. a combination of SKBMOD_F_{DMAC,SMAC,ETYPE}
 47	 *	2. SKBMOD_F_SWAPMAC
 48	 *	3. SKBMOD_F_ECN
 49	 * SKBMOD_F_ECN only works with IP packets; all other flags only work with Ethernet
 50	 * packets.
 51	 */
 52	if (flags == SKBMOD_F_ECN) {
 53		switch (skb_protocol(skb, true)) {
 54		case cpu_to_be16(ETH_P_IP):
 55		case cpu_to_be16(ETH_P_IPV6):
 56			max_edit_len += skb_network_header_len(skb);
 57			break;
 58		default:
 59			goto out;
 60		}
 61	} else if (!skb->dev || skb->dev->type != ARPHRD_ETHER) {
 62		goto out;
 63	}
 64
 65	err = skb_ensure_writable(skb, max_edit_len);
 66	if (unlikely(err)) /* best policy is to drop on the floor */
 67		goto drop;
 68
 69	if (flags & SKBMOD_F_DMAC)
 70		ether_addr_copy(eth_hdr(skb)->h_dest, p->eth_dst);
 71	if (flags & SKBMOD_F_SMAC)
 72		ether_addr_copy(eth_hdr(skb)->h_source, p->eth_src);
 73	if (flags & SKBMOD_F_ETYPE)
 74		eth_hdr(skb)->h_proto = p->eth_type;
 75
 76	if (flags & SKBMOD_F_SWAPMAC) {
 77		u16 tmpaddr[ETH_ALEN / 2]; /* ether_addr_copy() requirement */
 78		/*XXX: I am sure we can come up with more efficient swapping*/
 79		ether_addr_copy((u8 *)tmpaddr, eth_hdr(skb)->h_dest);
 80		ether_addr_copy(eth_hdr(skb)->h_dest, eth_hdr(skb)->h_source);
 81		ether_addr_copy(eth_hdr(skb)->h_source, (u8 *)tmpaddr);
 82	}
 83
 84	if (flags & SKBMOD_F_ECN)
 85		INET_ECN_set_ce(skb);
 86
 87out:
 88	return action;
 89
 90drop:
 91	qstats_overlimit_inc(this_cpu_ptr(d->common.cpu_qstats));
 92	return TC_ACT_SHOT;
 93}
 94
 95static const struct nla_policy skbmod_policy[TCA_SKBMOD_MAX + 1] = {
 96	[TCA_SKBMOD_PARMS]		= { .len = sizeof(struct tc_skbmod) },
 97	[TCA_SKBMOD_DMAC]		= { .len = ETH_ALEN },
 98	[TCA_SKBMOD_SMAC]		= { .len = ETH_ALEN },
 99	[TCA_SKBMOD_ETYPE]		= { .type = NLA_U16 },
100};
101
102static int tcf_skbmod_init(struct net *net, struct nlattr *nla,
103			   struct nlattr *est, struct tc_action **a,
104			   struct tcf_proto *tp, u32 flags,
105			   struct netlink_ext_ack *extack)
106{
107	struct tc_action_net *tn = net_generic(net, act_skbmod_ops.net_id);
108	bool ovr = flags & TCA_ACT_FLAGS_REPLACE;
109	bool bind = flags & TCA_ACT_FLAGS_BIND;
110	struct nlattr *tb[TCA_SKBMOD_MAX + 1];
111	struct tcf_skbmod_params *p, *p_old;
112	struct tcf_chain *goto_ch = NULL;
113	struct tc_skbmod *parm;
114	u32 lflags = 0, index;
115	struct tcf_skbmod *d;
116	bool exists = false;
117	u8 *daddr = NULL;
118	u8 *saddr = NULL;
119	u16 eth_type = 0;
120	int ret = 0, err;
121
122	if (!nla)
123		return -EINVAL;
124
125	err = nla_parse_nested_deprecated(tb, TCA_SKBMOD_MAX, nla,
126					  skbmod_policy, NULL);
127	if (err < 0)
128		return err;
129
130	if (!tb[TCA_SKBMOD_PARMS])
131		return -EINVAL;
132
133	if (tb[TCA_SKBMOD_DMAC]) {
134		daddr = nla_data(tb[TCA_SKBMOD_DMAC]);
135		lflags |= SKBMOD_F_DMAC;
136	}
137
138	if (tb[TCA_SKBMOD_SMAC]) {
139		saddr = nla_data(tb[TCA_SKBMOD_SMAC]);
140		lflags |= SKBMOD_F_SMAC;
141	}
142
143	if (tb[TCA_SKBMOD_ETYPE]) {
144		eth_type = nla_get_u16(tb[TCA_SKBMOD_ETYPE]);
145		lflags |= SKBMOD_F_ETYPE;
146	}
147
148	parm = nla_data(tb[TCA_SKBMOD_PARMS]);
149	index = parm->index;
150	if (parm->flags & SKBMOD_F_SWAPMAC)
151		lflags = SKBMOD_F_SWAPMAC;
152	if (parm->flags & SKBMOD_F_ECN)
153		lflags = SKBMOD_F_ECN;
154
155	err = tcf_idr_check_alloc(tn, &index, a, bind);
156	if (err < 0)
157		return err;
158	exists = err;
159	if (exists && bind)
160		return ACT_P_BOUND;
161
162	if (!lflags) {
163		if (exists)
164			tcf_idr_release(*a, bind);
165		else
166			tcf_idr_cleanup(tn, index);
167		return -EINVAL;
168	}
169
170	if (!exists) {
171		ret = tcf_idr_create(tn, index, est, a,
172				     &act_skbmod_ops, bind, true, flags);
173		if (ret) {
174			tcf_idr_cleanup(tn, index);
175			return ret;
176		}
177
178		ret = ACT_P_CREATED;
179	} else if (!ovr) {
180		tcf_idr_release(*a, bind);
181		return -EEXIST;
182	}
183	err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
184	if (err < 0)
185		goto release_idr;
186
187	d = to_skbmod(*a);
188
189	p = kzalloc(sizeof(struct tcf_skbmod_params), GFP_KERNEL);
190	if (unlikely(!p)) {
191		err = -ENOMEM;
192		goto put_chain;
193	}
194
195	p->flags = lflags;
196
197	if (ovr)
198		spin_lock_bh(&d->tcf_lock);
199	/* Protected by tcf_lock if overwriting existing action. */
200	goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
201	p_old = rcu_dereference_protected(d->skbmod_p, 1);
202
203	if (lflags & SKBMOD_F_DMAC)
204		ether_addr_copy(p->eth_dst, daddr);
205	if (lflags & SKBMOD_F_SMAC)
206		ether_addr_copy(p->eth_src, saddr);
207	if (lflags & SKBMOD_F_ETYPE)
208		p->eth_type = htons(eth_type);
209
210	rcu_assign_pointer(d->skbmod_p, p);
211	if (ovr)
212		spin_unlock_bh(&d->tcf_lock);
213
214	if (p_old)
215		kfree_rcu(p_old, rcu);
216	if (goto_ch)
217		tcf_chain_put_by_act(goto_ch);
218
219	return ret;
220put_chain:
221	if (goto_ch)
222		tcf_chain_put_by_act(goto_ch);
223release_idr:
224	tcf_idr_release(*a, bind);
225	return err;
226}
227
228static void tcf_skbmod_cleanup(struct tc_action *a)
229{
230	struct tcf_skbmod *d = to_skbmod(a);
231	struct tcf_skbmod_params  *p;
232
233	p = rcu_dereference_protected(d->skbmod_p, 1);
234	if (p)
235		kfree_rcu(p, rcu);
236}
237
238static int tcf_skbmod_dump(struct sk_buff *skb, struct tc_action *a,
239			   int bind, int ref)
240{
241	struct tcf_skbmod *d = to_skbmod(a);
242	unsigned char *b = skb_tail_pointer(skb);
243	struct tcf_skbmod_params  *p;
244	struct tc_skbmod opt;
245	struct tcf_t t;
246
247	memset(&opt, 0, sizeof(opt));
248	opt.index   = d->tcf_index;
249	opt.refcnt  = refcount_read(&d->tcf_refcnt) - ref;
250	opt.bindcnt = atomic_read(&d->tcf_bindcnt) - bind;
251	spin_lock_bh(&d->tcf_lock);
252	opt.action = d->tcf_action;
253	p = rcu_dereference_protected(d->skbmod_p,
254				      lockdep_is_held(&d->tcf_lock));
255	opt.flags  = p->flags;
256	if (nla_put(skb, TCA_SKBMOD_PARMS, sizeof(opt), &opt))
257		goto nla_put_failure;
258	if ((p->flags & SKBMOD_F_DMAC) &&
259	    nla_put(skb, TCA_SKBMOD_DMAC, ETH_ALEN, p->eth_dst))
260		goto nla_put_failure;
261	if ((p->flags & SKBMOD_F_SMAC) &&
262	    nla_put(skb, TCA_SKBMOD_SMAC, ETH_ALEN, p->eth_src))
263		goto nla_put_failure;
264	if ((p->flags & SKBMOD_F_ETYPE) &&
265	    nla_put_u16(skb, TCA_SKBMOD_ETYPE, ntohs(p->eth_type)))
266		goto nla_put_failure;
267
268	tcf_tm_dump(&t, &d->tcf_tm);
269	if (nla_put_64bit(skb, TCA_SKBMOD_TM, sizeof(t), &t, TCA_SKBMOD_PAD))
270		goto nla_put_failure;
271
272	spin_unlock_bh(&d->tcf_lock);
273	return skb->len;
274nla_put_failure:
275	spin_unlock_bh(&d->tcf_lock);
276	nlmsg_trim(skb, b);
277	return -1;
278}
279
280static struct tc_action_ops act_skbmod_ops = {
281	.kind		=	"skbmod",
282	.id		=	TCA_ACT_SKBMOD,
283	.owner		=	THIS_MODULE,
284	.act		=	tcf_skbmod_act,
285	.dump		=	tcf_skbmod_dump,
286	.init		=	tcf_skbmod_init,
287	.cleanup	=	tcf_skbmod_cleanup,
288	.size		=	sizeof(struct tcf_skbmod),
289};
290MODULE_ALIAS_NET_ACT("skbmod");
291
292static __net_init int skbmod_init_net(struct net *net)
293{
294	struct tc_action_net *tn = net_generic(net, act_skbmod_ops.net_id);
295
296	return tc_action_net_init(net, tn, &act_skbmod_ops);
297}
298
299static void __net_exit skbmod_exit_net(struct list_head *net_list)
300{
301	tc_action_net_exit(net_list, act_skbmod_ops.net_id);
302}
303
304static struct pernet_operations skbmod_net_ops = {
305	.init = skbmod_init_net,
306	.exit_batch = skbmod_exit_net,
307	.id   = &act_skbmod_ops.net_id,
308	.size = sizeof(struct tc_action_net),
309};
310
311MODULE_AUTHOR("Jamal Hadi Salim, <jhs@mojatatu.com>");
312MODULE_DESCRIPTION("SKB data mod-ing");
313MODULE_LICENSE("GPL");
314
315static int __init skbmod_init_module(void)
316{
317	return tcf_register_action(&act_skbmod_ops, &skbmod_net_ops);
318}
319
320static void __exit skbmod_cleanup_module(void)
321{
322	tcf_unregister_action(&act_skbmod_ops, &skbmod_net_ops);
323}
324
325module_init(skbmod_init_module);
326module_exit(skbmod_cleanup_module);