1/*
  2 * net/sched/act_skbmod.c  skb data modifier
  3 *
  4 * Copyright (c) 2016 Jamal Hadi Salim <jhs@mojatatu.com>
  5 *
  6 * This program is free software; you can redistribute it and/or modify
  7 * it under the terms of the GNU General Public License as published by
  8 * the Free Software Foundation; either version 2 of the License, or
  9 * (at your option) any later version.
 10*/
 11
 12#include <linux/module.h>
 13#include <linux/init.h>
 14#include <linux/kernel.h>
 15#include <linux/skbuff.h>
 16#include <linux/rtnetlink.h>
 17#include <net/netlink.h>
 18#include <net/pkt_sched.h>
 19
 20#include <linux/tc_act/tc_skbmod.h>
 21#include <net/tc_act/tc_skbmod.h>
 22
 23#define SKBMOD_TAB_MASK     15
 24
 25static unsigned int skbmod_net_id;
 26static struct tc_action_ops act_skbmod_ops;
 27
 28#define MAX_EDIT_LEN ETH_HLEN
 29static int tcf_skbmod_run(struct sk_buff *skb, const struct tc_action *a,
 30			  struct tcf_result *res)
 31{
 32	struct tcf_skbmod *d = to_skbmod(a);
 33	int action;
 34	struct tcf_skbmod_params *p;
 35	u64 flags;
 36	int err;
 37
 38	tcf_lastuse_update(&d->tcf_tm);
 39	bstats_cpu_update(this_cpu_ptr(d->common.cpu_bstats), skb);
 40
 41	/* XXX: if you are going to edit more fields beyond ethernet header
 42	 * (example when you add IP header replacement or vlan swap)
 43	 * then MAX_EDIT_LEN needs to change appropriately
 44	*/
 45	err = skb_ensure_writable(skb, MAX_EDIT_LEN);
 46	if (unlikely(err)) { /* best policy is to drop on the floor */
 47		qstats_overlimit_inc(this_cpu_ptr(d->common.cpu_qstats));
 48		return TC_ACT_SHOT;
 49	}
 50
 51	rcu_read_lock();
 52	action = READ_ONCE(d->tcf_action);
 53	if (unlikely(action == TC_ACT_SHOT)) {
 54		qstats_overlimit_inc(this_cpu_ptr(d->common.cpu_qstats));
 55		rcu_read_unlock();
 56		return action;
 57	}
 58
 59	p = rcu_dereference(d->skbmod_p);
 60	flags = p->flags;
 61	if (flags & SKBMOD_F_DMAC)
 62		ether_addr_copy(eth_hdr(skb)->h_dest, p->eth_dst);
 63	if (flags & SKBMOD_F_SMAC)
 64		ether_addr_copy(eth_hdr(skb)->h_source, p->eth_src);
 65	if (flags & SKBMOD_F_ETYPE)
 66		eth_hdr(skb)->h_proto = p->eth_type;
 67	rcu_read_unlock();
 68
 69	if (flags & SKBMOD_F_SWAPMAC) {
 70		u16 tmpaddr[ETH_ALEN / 2]; /* ether_addr_copy() requirement */
 71		/*XXX: I am sure we can come up with more efficient swapping*/
 72		ether_addr_copy((u8 *)tmpaddr, eth_hdr(skb)->h_dest);
 73		ether_addr_copy(eth_hdr(skb)->h_dest, eth_hdr(skb)->h_source);
 74		ether_addr_copy(eth_hdr(skb)->h_source, (u8 *)tmpaddr);
 75	}
 76
 77	return action;
 78}
 79
 80static const struct nla_policy skbmod_policy[TCA_SKBMOD_MAX + 1] = {
 81	[TCA_SKBMOD_PARMS]		= { .len = sizeof(struct tc_skbmod) },
 82	[TCA_SKBMOD_DMAC]		= { .len = ETH_ALEN },
 83	[TCA_SKBMOD_SMAC]		= { .len = ETH_ALEN },
 84	[TCA_SKBMOD_ETYPE]		= { .type = NLA_U16 },
 85};
 86
 87static int tcf_skbmod_init(struct net *net, struct nlattr *nla,
 88			   struct nlattr *est, struct tc_action **a,
 89			   int ovr, int bind)
 90{
 91	struct tc_action_net *tn = net_generic(net, skbmod_net_id);
 92	struct nlattr *tb[TCA_SKBMOD_MAX + 1];
 93	struct tcf_skbmod_params *p, *p_old;
 94	struct tc_skbmod *parm;
 95	struct tcf_skbmod *d;
 96	bool exists = false;
 97	u8 *daddr = NULL;
 98	u8 *saddr = NULL;
 99	u16 eth_type = 0;
100	u32 lflags = 0;
101	int ret = 0, err;
102
103	if (!nla)
104		return -EINVAL;
105
106	err = nla_parse_nested(tb, TCA_SKBMOD_MAX, nla, skbmod_policy);
107	if (err < 0)
108		return err;
109
110	if (!tb[TCA_SKBMOD_PARMS])
111		return -EINVAL;
112
113	if (tb[TCA_SKBMOD_DMAC]) {
114		daddr = nla_data(tb[TCA_SKBMOD_DMAC]);
115		lflags |= SKBMOD_F_DMAC;
116	}
117
118	if (tb[TCA_SKBMOD_SMAC]) {
119		saddr = nla_data(tb[TCA_SKBMOD_SMAC]);
120		lflags |= SKBMOD_F_SMAC;
121	}
122
123	if (tb[TCA_SKBMOD_ETYPE]) {
124		eth_type = nla_get_u16(tb[TCA_SKBMOD_ETYPE]);
125		lflags |= SKBMOD_F_ETYPE;
126	}
127
128	parm = nla_data(tb[TCA_SKBMOD_PARMS]);
129	if (parm->flags & SKBMOD_F_SWAPMAC)
130		lflags = SKBMOD_F_SWAPMAC;
131
132	exists = tcf_hash_check(tn, parm->index, a, bind);
133	if (exists && bind)
134		return 0;
135
136	if (!lflags)
137		return -EINVAL;
138
139	if (!exists) {
140		ret = tcf_hash_create(tn, parm->index, est, a,
141				      &act_skbmod_ops, bind, true);
142		if (ret)
143			return ret;
144
145		ret = ACT_P_CREATED;
146	} else {
147		tcf_hash_release(*a, bind);
148		if (!ovr)
149			return -EEXIST;
150	}
151
152	d = to_skbmod(*a);
153
154	ASSERT_RTNL();
155	p = kzalloc(sizeof(struct tcf_skbmod_params), GFP_KERNEL);
156	if (unlikely(!p)) {
157		if (ovr)
158			tcf_hash_release(*a, bind);
159		return -ENOMEM;
160	}
161
162	p->flags = lflags;
163	d->tcf_action = parm->action;
164
165	p_old = rtnl_dereference(d->skbmod_p);
166
167	if (ovr)
168		spin_lock_bh(&d->tcf_lock);
169
170	if (lflags & SKBMOD_F_DMAC)
171		ether_addr_copy(p->eth_dst, daddr);
172	if (lflags & SKBMOD_F_SMAC)
173		ether_addr_copy(p->eth_src, saddr);
174	if (lflags & SKBMOD_F_ETYPE)
175		p->eth_type = htons(eth_type);
176
177	rcu_assign_pointer(d->skbmod_p, p);
178	if (ovr)
179		spin_unlock_bh(&d->tcf_lock);
180
181	if (p_old)
182		kfree_rcu(p_old, rcu);
183
184	if (ret == ACT_P_CREATED)
185		tcf_hash_insert(tn, *a);
186	return ret;
187}
188
189static void tcf_skbmod_cleanup(struct tc_action *a, int bind)
190{
191	struct tcf_skbmod *d = to_skbmod(a);
192	struct tcf_skbmod_params  *p;
193
194	p = rcu_dereference_protected(d->skbmod_p, 1);
195	kfree_rcu(p, rcu);
196}
197
198static int tcf_skbmod_dump(struct sk_buff *skb, struct tc_action *a,
199			   int bind, int ref)
200{
201	struct tcf_skbmod *d = to_skbmod(a);
202	unsigned char *b = skb_tail_pointer(skb);
203	struct tcf_skbmod_params  *p = rtnl_dereference(d->skbmod_p);
204	struct tc_skbmod opt = {
205		.index   = d->tcf_index,
206		.refcnt  = d->tcf_refcnt - ref,
207		.bindcnt = d->tcf_bindcnt - bind,
208		.action  = d->tcf_action,
209	};
210	struct tcf_t t;
211
212	opt.flags  = p->flags;
213	if (nla_put(skb, TCA_SKBMOD_PARMS, sizeof(opt), &opt))
214		goto nla_put_failure;
215	if ((p->flags & SKBMOD_F_DMAC) &&
216	    nla_put(skb, TCA_SKBMOD_DMAC, ETH_ALEN, p->eth_dst))
217		goto nla_put_failure;
218	if ((p->flags & SKBMOD_F_SMAC) &&
219	    nla_put(skb, TCA_SKBMOD_SMAC, ETH_ALEN, p->eth_src))
220		goto nla_put_failure;
221	if ((p->flags & SKBMOD_F_ETYPE) &&
222	    nla_put_u16(skb, TCA_SKBMOD_ETYPE, ntohs(p->eth_type)))
223		goto nla_put_failure;
224
225	tcf_tm_dump(&t, &d->tcf_tm);
226	if (nla_put_64bit(skb, TCA_SKBMOD_TM, sizeof(t), &t, TCA_SKBMOD_PAD))
227		goto nla_put_failure;
228
229	return skb->len;
230nla_put_failure:
231	nlmsg_trim(skb, b);
232	return -1;
233}
234
235static int tcf_skbmod_walker(struct net *net, struct sk_buff *skb,
236			     struct netlink_callback *cb, int type,
237			     const struct tc_action_ops *ops)
238{
239	struct tc_action_net *tn = net_generic(net, skbmod_net_id);
240
241	return tcf_generic_walker(tn, skb, cb, type, ops);
242}
243
244static int tcf_skbmod_search(struct net *net, struct tc_action **a, u32 index)
245{
246	struct tc_action_net *tn = net_generic(net, skbmod_net_id);
247
248	return tcf_hash_search(tn, a, index);
249}
250
251static struct tc_action_ops act_skbmod_ops = {
252	.kind		=	"skbmod",
253	.type		=	TCA_ACT_SKBMOD,
254	.owner		=	THIS_MODULE,
255	.act		=	tcf_skbmod_run,
256	.dump		=	tcf_skbmod_dump,
257	.init		=	tcf_skbmod_init,
258	.cleanup	=	tcf_skbmod_cleanup,
259	.walk		=	tcf_skbmod_walker,
260	.lookup		=	tcf_skbmod_search,
261	.size		=	sizeof(struct tcf_skbmod),
262};
263
264static __net_init int skbmod_init_net(struct net *net)
265{
266	struct tc_action_net *tn = net_generic(net, skbmod_net_id);
267
268	return tc_action_net_init(tn, &act_skbmod_ops, SKBMOD_TAB_MASK);
269}
270
271static void __net_exit skbmod_exit_net(struct net *net)
272{
273	struct tc_action_net *tn = net_generic(net, skbmod_net_id);
274
275	tc_action_net_exit(tn);
276}
277
278static struct pernet_operations skbmod_net_ops = {
279	.init = skbmod_init_net,
280	.exit = skbmod_exit_net,
281	.id   = &skbmod_net_id,
282	.size = sizeof(struct tc_action_net),
283};
284
285MODULE_AUTHOR("Jamal Hadi Salim, <jhs@mojatatu.com>");
286MODULE_DESCRIPTION("SKB data mod-ing");
287MODULE_LICENSE("GPL");
288
289static int __init skbmod_init_module(void)
290{
291	return tcf_register_action(&act_skbmod_ops, &skbmod_net_ops);
292}
293
294static void __exit skbmod_cleanup_module(void)
295{
296	tcf_unregister_action(&act_skbmod_ops, &skbmod_net_ops);
297}
298
299module_init(skbmod_init_module);
300module_exit(skbmod_cleanup_module);