xref: /openbmc/linux/net/sched/act_skbmod.c (revision 6aa7de05)
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 static unsigned int skbmod_net_id;
24 static struct tc_action_ops act_skbmod_ops;
25 
26 #define MAX_EDIT_LEN ETH_HLEN
27 static int tcf_skbmod_run(struct sk_buff *skb, const struct tc_action *a,
28 			  struct tcf_result *res)
29 {
30 	struct tcf_skbmod *d = to_skbmod(a);
31 	int action;
32 	struct tcf_skbmod_params *p;
33 	u64 flags;
34 	int err;
35 
36 	tcf_lastuse_update(&d->tcf_tm);
37 	bstats_cpu_update(this_cpu_ptr(d->common.cpu_bstats), skb);
38 
39 	/* XXX: if you are going to edit more fields beyond ethernet header
40 	 * (example when you add IP header replacement or vlan swap)
41 	 * then MAX_EDIT_LEN needs to change appropriately
42 	*/
43 	err = skb_ensure_writable(skb, MAX_EDIT_LEN);
44 	if (unlikely(err)) { /* best policy is to drop on the floor */
45 		qstats_overlimit_inc(this_cpu_ptr(d->common.cpu_qstats));
46 		return TC_ACT_SHOT;
47 	}
48 
49 	rcu_read_lock();
50 	action = READ_ONCE(d->tcf_action);
51 	if (unlikely(action == TC_ACT_SHOT)) {
52 		qstats_overlimit_inc(this_cpu_ptr(d->common.cpu_qstats));
53 		rcu_read_unlock();
54 		return action;
55 	}
56 
57 	p = rcu_dereference(d->skbmod_p);
58 	flags = p->flags;
59 	if (flags & SKBMOD_F_DMAC)
60 		ether_addr_copy(eth_hdr(skb)->h_dest, p->eth_dst);
61 	if (flags & SKBMOD_F_SMAC)
62 		ether_addr_copy(eth_hdr(skb)->h_source, p->eth_src);
63 	if (flags & SKBMOD_F_ETYPE)
64 		eth_hdr(skb)->h_proto = p->eth_type;
65 	rcu_read_unlock();
66 
67 	if (flags & SKBMOD_F_SWAPMAC) {
68 		u16 tmpaddr[ETH_ALEN / 2]; /* ether_addr_copy() requirement */
69 		/*XXX: I am sure we can come up with more efficient swapping*/
70 		ether_addr_copy((u8 *)tmpaddr, eth_hdr(skb)->h_dest);
71 		ether_addr_copy(eth_hdr(skb)->h_dest, eth_hdr(skb)->h_source);
72 		ether_addr_copy(eth_hdr(skb)->h_source, (u8 *)tmpaddr);
73 	}
74 
75 	return action;
76 }
77 
78 static const struct nla_policy skbmod_policy[TCA_SKBMOD_MAX + 1] = {
79 	[TCA_SKBMOD_PARMS]		= { .len = sizeof(struct tc_skbmod) },
80 	[TCA_SKBMOD_DMAC]		= { .len = ETH_ALEN },
81 	[TCA_SKBMOD_SMAC]		= { .len = ETH_ALEN },
82 	[TCA_SKBMOD_ETYPE]		= { .type = NLA_U16 },
83 };
84 
85 static int tcf_skbmod_init(struct net *net, struct nlattr *nla,
86 			   struct nlattr *est, struct tc_action **a,
87 			   int ovr, int bind)
88 {
89 	struct tc_action_net *tn = net_generic(net, skbmod_net_id);
90 	struct nlattr *tb[TCA_SKBMOD_MAX + 1];
91 	struct tcf_skbmod_params *p, *p_old;
92 	struct tc_skbmod *parm;
93 	struct tcf_skbmod *d;
94 	bool exists = false;
95 	u8 *daddr = NULL;
96 	u8 *saddr = NULL;
97 	u16 eth_type = 0;
98 	u32 lflags = 0;
99 	int ret = 0, err;
100 
101 	if (!nla)
102 		return -EINVAL;
103 
104 	err = nla_parse_nested(tb, TCA_SKBMOD_MAX, nla, skbmod_policy, NULL);
105 	if (err < 0)
106 		return err;
107 
108 	if (!tb[TCA_SKBMOD_PARMS])
109 		return -EINVAL;
110 
111 	if (tb[TCA_SKBMOD_DMAC]) {
112 		daddr = nla_data(tb[TCA_SKBMOD_DMAC]);
113 		lflags |= SKBMOD_F_DMAC;
114 	}
115 
116 	if (tb[TCA_SKBMOD_SMAC]) {
117 		saddr = nla_data(tb[TCA_SKBMOD_SMAC]);
118 		lflags |= SKBMOD_F_SMAC;
119 	}
120 
121 	if (tb[TCA_SKBMOD_ETYPE]) {
122 		eth_type = nla_get_u16(tb[TCA_SKBMOD_ETYPE]);
123 		lflags |= SKBMOD_F_ETYPE;
124 	}
125 
126 	parm = nla_data(tb[TCA_SKBMOD_PARMS]);
127 	if (parm->flags & SKBMOD_F_SWAPMAC)
128 		lflags = SKBMOD_F_SWAPMAC;
129 
130 	exists = tcf_idr_check(tn, parm->index, a, bind);
131 	if (exists && bind)
132 		return 0;
133 
134 	if (!lflags)
135 		return -EINVAL;
136 
137 	if (!exists) {
138 		ret = tcf_idr_create(tn, parm->index, est, a,
139 				     &act_skbmod_ops, bind, true);
140 		if (ret)
141 			return ret;
142 
143 		ret = ACT_P_CREATED;
144 	} else {
145 		tcf_idr_release(*a, bind);
146 		if (!ovr)
147 			return -EEXIST;
148 	}
149 
150 	d = to_skbmod(*a);
151 
152 	ASSERT_RTNL();
153 	p = kzalloc(sizeof(struct tcf_skbmod_params), GFP_KERNEL);
154 	if (unlikely(!p)) {
155 		if (ovr)
156 			tcf_idr_release(*a, bind);
157 		return -ENOMEM;
158 	}
159 
160 	p->flags = lflags;
161 	d->tcf_action = parm->action;
162 
163 	p_old = rtnl_dereference(d->skbmod_p);
164 
165 	if (ovr)
166 		spin_lock_bh(&d->tcf_lock);
167 
168 	if (lflags & SKBMOD_F_DMAC)
169 		ether_addr_copy(p->eth_dst, daddr);
170 	if (lflags & SKBMOD_F_SMAC)
171 		ether_addr_copy(p->eth_src, saddr);
172 	if (lflags & SKBMOD_F_ETYPE)
173 		p->eth_type = htons(eth_type);
174 
175 	rcu_assign_pointer(d->skbmod_p, p);
176 	if (ovr)
177 		spin_unlock_bh(&d->tcf_lock);
178 
179 	if (p_old)
180 		kfree_rcu(p_old, rcu);
181 
182 	if (ret == ACT_P_CREATED)
183 		tcf_idr_insert(tn, *a);
184 	return ret;
185 }
186 
187 static void tcf_skbmod_cleanup(struct tc_action *a, int bind)
188 {
189 	struct tcf_skbmod *d = to_skbmod(a);
190 	struct tcf_skbmod_params  *p;
191 
192 	p = rcu_dereference_protected(d->skbmod_p, 1);
193 	kfree_rcu(p, rcu);
194 }
195 
196 static int tcf_skbmod_dump(struct sk_buff *skb, struct tc_action *a,
197 			   int bind, int ref)
198 {
199 	struct tcf_skbmod *d = to_skbmod(a);
200 	unsigned char *b = skb_tail_pointer(skb);
201 	struct tcf_skbmod_params  *p = rtnl_dereference(d->skbmod_p);
202 	struct tc_skbmod opt = {
203 		.index   = d->tcf_index,
204 		.refcnt  = d->tcf_refcnt - ref,
205 		.bindcnt = d->tcf_bindcnt - bind,
206 		.action  = d->tcf_action,
207 	};
208 	struct tcf_t t;
209 
210 	opt.flags  = p->flags;
211 	if (nla_put(skb, TCA_SKBMOD_PARMS, sizeof(opt), &opt))
212 		goto nla_put_failure;
213 	if ((p->flags & SKBMOD_F_DMAC) &&
214 	    nla_put(skb, TCA_SKBMOD_DMAC, ETH_ALEN, p->eth_dst))
215 		goto nla_put_failure;
216 	if ((p->flags & SKBMOD_F_SMAC) &&
217 	    nla_put(skb, TCA_SKBMOD_SMAC, ETH_ALEN, p->eth_src))
218 		goto nla_put_failure;
219 	if ((p->flags & SKBMOD_F_ETYPE) &&
220 	    nla_put_u16(skb, TCA_SKBMOD_ETYPE, ntohs(p->eth_type)))
221 		goto nla_put_failure;
222 
223 	tcf_tm_dump(&t, &d->tcf_tm);
224 	if (nla_put_64bit(skb, TCA_SKBMOD_TM, sizeof(t), &t, TCA_SKBMOD_PAD))
225 		goto nla_put_failure;
226 
227 	return skb->len;
228 nla_put_failure:
229 	nlmsg_trim(skb, b);
230 	return -1;
231 }
232 
233 static int tcf_skbmod_walker(struct net *net, struct sk_buff *skb,
234 			     struct netlink_callback *cb, int type,
235 			     const struct tc_action_ops *ops)
236 {
237 	struct tc_action_net *tn = net_generic(net, skbmod_net_id);
238 
239 	return tcf_generic_walker(tn, skb, cb, type, ops);
240 }
241 
242 static int tcf_skbmod_search(struct net *net, struct tc_action **a, u32 index)
243 {
244 	struct tc_action_net *tn = net_generic(net, skbmod_net_id);
245 
246 	return tcf_idr_search(tn, a, index);
247 }
248 
249 static struct tc_action_ops act_skbmod_ops = {
250 	.kind		=	"skbmod",
251 	.type		=	TCA_ACT_SKBMOD,
252 	.owner		=	THIS_MODULE,
253 	.act		=	tcf_skbmod_run,
254 	.dump		=	tcf_skbmod_dump,
255 	.init		=	tcf_skbmod_init,
256 	.cleanup	=	tcf_skbmod_cleanup,
257 	.walk		=	tcf_skbmod_walker,
258 	.lookup		=	tcf_skbmod_search,
259 	.size		=	sizeof(struct tcf_skbmod),
260 };
261 
262 static __net_init int skbmod_init_net(struct net *net)
263 {
264 	struct tc_action_net *tn = net_generic(net, skbmod_net_id);
265 
266 	return tc_action_net_init(tn, &act_skbmod_ops);
267 }
268 
269 static void __net_exit skbmod_exit_net(struct net *net)
270 {
271 	struct tc_action_net *tn = net_generic(net, skbmod_net_id);
272 
273 	tc_action_net_exit(tn);
274 }
275 
276 static struct pernet_operations skbmod_net_ops = {
277 	.init = skbmod_init_net,
278 	.exit = skbmod_exit_net,
279 	.id   = &skbmod_net_id,
280 	.size = sizeof(struct tc_action_net),
281 };
282 
283 MODULE_AUTHOR("Jamal Hadi Salim, <jhs@mojatatu.com>");
284 MODULE_DESCRIPTION("SKB data mod-ing");
285 MODULE_LICENSE("GPL");
286 
287 static int __init skbmod_init_module(void)
288 {
289 	return tcf_register_action(&act_skbmod_ops, &skbmod_net_ops);
290 }
291 
292 static void __exit skbmod_cleanup_module(void)
293 {
294 	tcf_unregister_action(&act_skbmod_ops, &skbmod_net_ops);
295 }
296 
297 module_init(skbmod_init_module);
298 module_exit(skbmod_cleanup_module);
299