xref: /linux/net/sched/em_ipt.c (revision 8bc7c5e525584903ea83332e18a2118ed3b1985e) 
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * net/sched/em_ipt.c IPtables matches Ematch
4  *
5  * (c) 2018 Eyal Birger <eyal.birger@gmail.com>
6  */
7 
8 #include <linux/gfp.h>
9 #include <linux/module.h>
10 #include <linux/types.h>
11 #include <linux/kernel.h>
12 #include <linux/string.h>
13 #include <linux/skbuff.h>
14 #include <linux/tc_ematch/tc_em_ipt.h>
15 #include <linux/netfilter.h>
16 #include <linux/netfilter/x_tables.h>
17 #include <linux/netfilter_ipv4/ip_tables.h>
18 #include <linux/netfilter_ipv6/ip6_tables.h>
19 #include <net/pkt_cls.h>
20 
21 struct em_ipt_match {
22 	const struct xt_match *match;
23 	u32 hook;
24 	u8 nfproto;
25 	u8 match_data[] __aligned(8);
26 };
27 
28 struct em_ipt_xt_match {
29 	char *match_name;
30 	int (*validate_match_data)(struct nlattr **tb, u8 mrev);
31 };
32 
33 static const struct nla_policy em_ipt_policy[TCA_EM_IPT_MAX + 1] = {
34 	[TCA_EM_IPT_MATCH_NAME]		= { .type = NLA_STRING,
35 					    .len = XT_EXTENSION_MAXNAMELEN },
36 	[TCA_EM_IPT_MATCH_REVISION]	= { .type = NLA_U8 },
37 	[TCA_EM_IPT_HOOK]		= { .type = NLA_U32 },
38 	[TCA_EM_IPT_NFPROTO]		= { .type = NLA_U8 },
39 	[TCA_EM_IPT_MATCH_DATA]		= { .type = NLA_UNSPEC },
40 };
41 
42 static int check_match(struct net *net, struct em_ipt_match *im, int mdata_len)
43 {
44 	struct xt_mtchk_param mtpar = {};
45 	union {
46 		struct ipt_entry e4;
47 		struct ip6t_entry e6;
48 	} e = {};
49 
50 	mtpar.net	= net;
51 	mtpar.table	= "filter";
52 	mtpar.hook_mask	= 1 << im->hook;
53 	mtpar.family	= im->match->family;
54 	mtpar.match	= im->match;
55 	mtpar.entryinfo = &e;
56 	mtpar.matchinfo	= (void *)im->match_data;
57 	return xt_check_match(&mtpar, mdata_len, 0, 0);
58 }
59 
60 static int policy_validate_match_data(struct nlattr **tb, u8 mrev)
61 {
62 	if (mrev != 0) {
63 		pr_err("only policy match revision 0 supported");
64 		return -EINVAL;
65 	}
66 
67 	if (nla_get_u32(tb[TCA_EM_IPT_HOOK]) != NF_INET_PRE_ROUTING) {
68 		pr_err("policy can only be matched on NF_INET_PRE_ROUTING");
69 		return -EINVAL;
70 	}
71 
72 	return 0;
73 }
74 
75 static int addrtype_validate_match_data(struct nlattr **tb, u8 mrev)
76 {
77 	if (mrev != 1) {
78 		pr_err("only addrtype match revision 1 supported");
79 		return -EINVAL;
80 	}
81 
82 	return 0;
83 }
84 
85 static const struct em_ipt_xt_match em_ipt_xt_matches[] = {
86 	{
87 		.match_name = "policy",
88 		.validate_match_data = policy_validate_match_data
89 	},
90 	{
91 		.match_name = "addrtype",
92 		.validate_match_data = addrtype_validate_match_data
93 	},
94 	{}
95 };
96 
97 static struct xt_match *get_xt_match(struct nlattr **tb)
98 {
99 	const struct em_ipt_xt_match *m;
100 	struct nlattr *mname_attr;
101 	u8 nfproto, mrev = 0;
102 	int ret;
103 
104 	mname_attr = tb[TCA_EM_IPT_MATCH_NAME];
105 	for (m = em_ipt_xt_matches; m->match_name; m++) {
106 		if (!nla_strcmp(mname_attr, m->match_name))
107 			break;
108 	}
109 
110 	if (!m->match_name) {
111 		pr_err("Unsupported xt match");
112 		return ERR_PTR(-EINVAL);
113 	}
114 
115 	if (tb[TCA_EM_IPT_MATCH_REVISION])
116 		mrev = nla_get_u8(tb[TCA_EM_IPT_MATCH_REVISION]);
117 
118 	ret = m->validate_match_data(tb, mrev);
119 	if (ret < 0)
120 		return ERR_PTR(ret);
121 
122 	nfproto = nla_get_u8(tb[TCA_EM_IPT_NFPROTO]);
123 	return xt_request_find_match(nfproto, m->match_name, mrev);
124 }
125 
126 static int em_ipt_change(struct net *net, void *data, int data_len,
127 			 struct tcf_ematch *em)
128 {
129 	struct nlattr *tb[TCA_EM_IPT_MAX + 1];
130 	struct em_ipt_match *im = NULL;
131 	struct xt_match *match;
132 	int mdata_len, ret;
133 	u8 nfproto;
134 
135 	ret = nla_parse_deprecated(tb, TCA_EM_IPT_MAX, data, data_len,
136 				   em_ipt_policy, NULL);
137 	if (ret < 0)
138 		return ret;
139 
140 	if (!tb[TCA_EM_IPT_HOOK] || !tb[TCA_EM_IPT_MATCH_NAME] ||
141 	    !tb[TCA_EM_IPT_MATCH_DATA] || !tb[TCA_EM_IPT_NFPROTO])
142 		return -EINVAL;
143 
144 	nfproto = nla_get_u8(tb[TCA_EM_IPT_NFPROTO]);
145 	switch (nfproto) {
146 	case NFPROTO_IPV4:
147 	case NFPROTO_IPV6:
148 		break;
149 	default:
150 		return -EINVAL;
151 	}
152 
153 	match = get_xt_match(tb);
154 	if (IS_ERR(match)) {
155 		pr_err("unable to load match\n");
156 		return PTR_ERR(match);
157 	}
158 
159 	mdata_len = XT_ALIGN(nla_len(tb[TCA_EM_IPT_MATCH_DATA]));
160 	im = kzalloc(sizeof(*im) + mdata_len, GFP_KERNEL);
161 	if (!im) {
162 		ret = -ENOMEM;
163 		goto err;
164 	}
165 
166 	im->match = match;
167 	im->hook = nla_get_u32(tb[TCA_EM_IPT_HOOK]);
168 	im->nfproto = nfproto;
169 	nla_memcpy(im->match_data, tb[TCA_EM_IPT_MATCH_DATA], mdata_len);
170 
171 	ret = check_match(net, im, mdata_len);
172 	if (ret)
173 		goto err;
174 
175 	em->datalen = sizeof(*im) + mdata_len;
176 	em->data = (unsigned long)im;
177 	return 0;
178 
179 err:
180 	kfree(im);
181 	module_put(match->me);
182 	return ret;
183 }
184 
185 static void em_ipt_destroy(struct tcf_ematch *em)
186 {
187 	struct em_ipt_match *im = (void *)em->data;
188 
189 	if (!im)
190 		return;
191 
192 	if (im->match->destroy) {
193 		struct xt_mtdtor_param par = {
194 			.net = em->net,
195 			.match = im->match,
196 			.matchinfo = im->match_data,
197 			.family = im->match->family
198 		};
199 		im->match->destroy(&par);
200 	}
201 	module_put(im->match->me);
202 	kfree(im);
203 }
204 
205 static int em_ipt_match(struct sk_buff *skb, struct tcf_ematch *em,
206 			struct tcf_pkt_info *info)
207 {
208 	const struct em_ipt_match *im = (const void *)em->data;
209 	struct xt_action_param acpar = {};
210 	struct net_device *indev = NULL;
211 	u8 nfproto = im->match->family;
212 	struct nf_hook_state state;
213 	int ret;
214 
215 	switch (skb_protocol(skb, true)) {
216 	case htons(ETH_P_IP):
217 		if (!pskb_network_may_pull(skb, sizeof(struct iphdr)))
218 			return 0;
219 		if (nfproto == NFPROTO_UNSPEC)
220 			nfproto = NFPROTO_IPV4;
221 		break;
222 	case htons(ETH_P_IPV6):
223 		if (!pskb_network_may_pull(skb, sizeof(struct ipv6hdr)))
224 			return 0;
225 		if (nfproto == NFPROTO_UNSPEC)
226 			nfproto = NFPROTO_IPV6;
227 		break;
228 	default:
229 		return 0;
230 	}
231 
232 	rcu_read_lock();
233 
234 	if (skb->skb_iif)
235 		indev = dev_get_by_index_rcu(em->net, skb->skb_iif);
236 
237 	nf_hook_state_init(&state, im->hook, nfproto,
238 			   indev ?: skb->dev, skb->dev, NULL, em->net, NULL);
239 
240 	acpar.match = im->match;
241 	acpar.matchinfo = im->match_data;
242 	acpar.state = &state;
243 
244 	ret = im->match->match(skb, &acpar);
245 
246 	rcu_read_unlock();
247 	return ret;
248 }
249 
250 static int em_ipt_dump(struct sk_buff *skb, struct tcf_ematch *em)
251 {
252 	struct em_ipt_match *im = (void *)em->data;
253 
254 	if (nla_put_string(skb, TCA_EM_IPT_MATCH_NAME, im->match->name) < 0)
255 		return -EMSGSIZE;
256 	if (nla_put_u32(skb, TCA_EM_IPT_HOOK, im->hook) < 0)
257 		return -EMSGSIZE;
258 	if (nla_put_u8(skb, TCA_EM_IPT_MATCH_REVISION, im->match->revision) < 0)
259 		return -EMSGSIZE;
260 	if (nla_put_u8(skb, TCA_EM_IPT_NFPROTO, im->nfproto) < 0)
261 		return -EMSGSIZE;
262 	if (nla_put(skb, TCA_EM_IPT_MATCH_DATA,
263 		    im->match->usersize ?: im->match->matchsize,
264 		    im->match_data) < 0)
265 		return -EMSGSIZE;
266 
267 	return 0;
268 }
269 
270 static struct tcf_ematch_ops em_ipt_ops = {
271 	.kind	  = TCF_EM_IPT,
272 	.change	  = em_ipt_change,
273 	.destroy  = em_ipt_destroy,
274 	.match	  = em_ipt_match,
275 	.dump	  = em_ipt_dump,
276 	.owner	  = THIS_MODULE,
277 	.link	  = LIST_HEAD_INIT(em_ipt_ops.link)
278 };
279 
280 static int __init init_em_ipt(void)
281 {
282 	return tcf_em_register(&em_ipt_ops);
283 }
284 
285 static void __exit exit_em_ipt(void)
286 {
287 	tcf_em_unregister(&em_ipt_ops);
288 }
289 
290 MODULE_LICENSE("GPL");
291 MODULE_AUTHOR("Eyal Birger <eyal.birger@gmail.com>");
292 MODULE_DESCRIPTION("TC extended match for IPtables matches");
293 
294 module_init(init_em_ipt);
295 module_exit(exit_em_ipt);
296 
297 MODULE_ALIAS_TCF_EMATCH(TCF_EM_IPT);
298