xref: /openbmc/linux/net/ipv6/rpl_iptunnel.c (revision 0f9b4c3ca5fdf3e177266ef994071b1a03f07318)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Authors:
4  * (C) 2020 Alexander Aring <alex.aring@gmail.com>
5  */
6 
7 #include <linux/rpl_iptunnel.h>
8 
9 #include <net/dst_cache.h>
10 #include <net/ip6_route.h>
11 #include <net/lwtunnel.h>
12 #include <net/ipv6.h>
13 #include <net/rpl.h>
14 
15 struct rpl_iptunnel_encap {
16 	DECLARE_FLEX_ARRAY(struct ipv6_rpl_sr_hdr, srh);
17 };
18 
19 struct rpl_lwt {
20 	struct dst_cache cache;
21 	struct rpl_iptunnel_encap tuninfo;
22 };
23 
rpl_lwt_lwtunnel(struct lwtunnel_state * lwt)24 static inline struct rpl_lwt *rpl_lwt_lwtunnel(struct lwtunnel_state *lwt)
25 {
26 	return (struct rpl_lwt *)lwt->data;
27 }
28 
29 static inline struct rpl_iptunnel_encap *
rpl_encap_lwtunnel(struct lwtunnel_state * lwt)30 rpl_encap_lwtunnel(struct lwtunnel_state *lwt)
31 {
32 	return &rpl_lwt_lwtunnel(lwt)->tuninfo;
33 }
34 
35 static const struct nla_policy rpl_iptunnel_policy[RPL_IPTUNNEL_MAX + 1] = {
36 	[RPL_IPTUNNEL_SRH]	= { .type = NLA_BINARY },
37 };
38 
rpl_validate_srh(struct net * net,struct ipv6_rpl_sr_hdr * srh,size_t seglen)39 static bool rpl_validate_srh(struct net *net, struct ipv6_rpl_sr_hdr *srh,
40 			     size_t seglen)
41 {
42 	int err;
43 
44 	if ((srh->hdrlen << 3) != seglen)
45 		return false;
46 
47 	/* check at least one segment and seglen fit with segments_left */
48 	if (!srh->segments_left ||
49 	    (srh->segments_left * sizeof(struct in6_addr)) != seglen)
50 		return false;
51 
52 	if (srh->cmpri || srh->cmpre)
53 		return false;
54 
55 	err = ipv6_chk_rpl_srh_loop(net, srh->rpl_segaddr,
56 				    srh->segments_left);
57 	if (err)
58 		return false;
59 
60 	if (ipv6_addr_type(&srh->rpl_segaddr[srh->segments_left - 1]) &
61 	    IPV6_ADDR_MULTICAST)
62 		return false;
63 
64 	return true;
65 }
66 
rpl_build_state(struct net * net,struct nlattr * nla,unsigned int family,const void * cfg,struct lwtunnel_state ** ts,struct netlink_ext_ack * extack)67 static int rpl_build_state(struct net *net, struct nlattr *nla,
68 			   unsigned int family, const void *cfg,
69 			   struct lwtunnel_state **ts,
70 			   struct netlink_ext_ack *extack)
71 {
72 	struct nlattr *tb[RPL_IPTUNNEL_MAX + 1];
73 	struct lwtunnel_state *newts;
74 	struct ipv6_rpl_sr_hdr *srh;
75 	struct rpl_lwt *rlwt;
76 	int err, srh_len;
77 
78 	if (family != AF_INET6)
79 		return -EINVAL;
80 
81 	err = nla_parse_nested(tb, RPL_IPTUNNEL_MAX, nla,
82 			       rpl_iptunnel_policy, extack);
83 	if (err < 0)
84 		return err;
85 
86 	if (!tb[RPL_IPTUNNEL_SRH])
87 		return -EINVAL;
88 
89 	srh = nla_data(tb[RPL_IPTUNNEL_SRH]);
90 	srh_len = nla_len(tb[RPL_IPTUNNEL_SRH]);
91 
92 	if (srh_len < sizeof(*srh))
93 		return -EINVAL;
94 
95 	/* verify that SRH is consistent */
96 	if (!rpl_validate_srh(net, srh, srh_len - sizeof(*srh)))
97 		return -EINVAL;
98 
99 	newts = lwtunnel_state_alloc(srh_len + sizeof(*rlwt));
100 	if (!newts)
101 		return -ENOMEM;
102 
103 	rlwt = rpl_lwt_lwtunnel(newts);
104 
105 	err = dst_cache_init(&rlwt->cache, GFP_ATOMIC);
106 	if (err) {
107 		kfree(newts);
108 		return err;
109 	}
110 
111 	memcpy(&rlwt->tuninfo.srh, srh, srh_len);
112 
113 	newts->type = LWTUNNEL_ENCAP_RPL;
114 	newts->flags |= LWTUNNEL_STATE_INPUT_REDIRECT;
115 	newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT;
116 
117 	*ts = newts;
118 
119 	return 0;
120 }
121 
rpl_destroy_state(struct lwtunnel_state * lwt)122 static void rpl_destroy_state(struct lwtunnel_state *lwt)
123 {
124 	dst_cache_destroy(&rpl_lwt_lwtunnel(lwt)->cache);
125 }
126 
rpl_do_srh_inline(struct sk_buff * skb,const struct rpl_lwt * rlwt,const struct ipv6_rpl_sr_hdr * srh,struct dst_entry * cache_dst)127 static int rpl_do_srh_inline(struct sk_buff *skb, const struct rpl_lwt *rlwt,
128 			     const struct ipv6_rpl_sr_hdr *srh,
129 			     struct dst_entry *cache_dst)
130 {
131 	struct ipv6_rpl_sr_hdr *isrh, *csrh;
132 	const struct ipv6hdr *oldhdr;
133 	struct ipv6hdr *hdr;
134 	unsigned char *buf;
135 	size_t hdrlen;
136 	int err;
137 
138 	oldhdr = ipv6_hdr(skb);
139 
140 	buf = kcalloc(struct_size(srh, segments.addr, srh->segments_left), 2, GFP_ATOMIC);
141 	if (!buf)
142 		return -ENOMEM;
143 
144 	isrh = (struct ipv6_rpl_sr_hdr *)buf;
145 	csrh = (struct ipv6_rpl_sr_hdr *)(buf + ((srh->hdrlen + 1) << 3));
146 
147 	memcpy(isrh, srh, sizeof(*isrh));
148 	memcpy(isrh->rpl_segaddr, &srh->rpl_segaddr[1],
149 	       (srh->segments_left - 1) * 16);
150 	isrh->rpl_segaddr[srh->segments_left - 1] = oldhdr->daddr;
151 
152 	ipv6_rpl_srh_compress(csrh, isrh, &srh->rpl_segaddr[0],
153 			      isrh->segments_left - 1);
154 
155 	hdrlen = ((csrh->hdrlen + 1) << 3);
156 
157 	err = skb_cow_head(skb, hdrlen + dst_dev_overhead(cache_dst, skb));
158 	if (unlikely(err)) {
159 		kfree(buf);
160 		return err;
161 	}
162 
163 	skb_pull(skb, sizeof(struct ipv6hdr));
164 	skb_postpull_rcsum(skb, skb_network_header(skb),
165 			   sizeof(struct ipv6hdr));
166 
167 	skb_push(skb, sizeof(struct ipv6hdr) + hdrlen);
168 	skb_reset_network_header(skb);
169 	skb_mac_header_rebuild(skb);
170 
171 	hdr = ipv6_hdr(skb);
172 	memmove(hdr, oldhdr, sizeof(*hdr));
173 	isrh = (void *)hdr + sizeof(*hdr);
174 	memcpy(isrh, csrh, hdrlen);
175 
176 	isrh->nexthdr = hdr->nexthdr;
177 	hdr->nexthdr = NEXTHDR_ROUTING;
178 	hdr->daddr = srh->rpl_segaddr[0];
179 
180 	ipv6_hdr(skb)->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
181 	skb_set_transport_header(skb, sizeof(struct ipv6hdr));
182 
183 	skb_postpush_rcsum(skb, hdr, sizeof(struct ipv6hdr) + hdrlen);
184 
185 	kfree(buf);
186 
187 	return 0;
188 }
189 
rpl_do_srh(struct sk_buff * skb,const struct rpl_lwt * rlwt,struct dst_entry * cache_dst)190 static int rpl_do_srh(struct sk_buff *skb, const struct rpl_lwt *rlwt,
191 		      struct dst_entry *cache_dst)
192 {
193 	struct dst_entry *dst = skb_dst(skb);
194 	struct rpl_iptunnel_encap *tinfo;
195 
196 	if (skb->protocol != htons(ETH_P_IPV6))
197 		return -EINVAL;
198 
199 	tinfo = rpl_encap_lwtunnel(dst->lwtstate);
200 
201 	return rpl_do_srh_inline(skb, rlwt, tinfo->srh, cache_dst);
202 }
203 
rpl_output(struct net * net,struct sock * sk,struct sk_buff * skb)204 static int rpl_output(struct net *net, struct sock *sk, struct sk_buff *skb)
205 {
206 	struct dst_entry *orig_dst = skb_dst(skb);
207 	struct dst_entry *dst = NULL;
208 	struct rpl_lwt *rlwt;
209 	int err;
210 
211 	rlwt = rpl_lwt_lwtunnel(orig_dst->lwtstate);
212 
213 	local_bh_disable();
214 	dst = dst_cache_get(&rlwt->cache);
215 	local_bh_enable();
216 
217 	err = rpl_do_srh(skb, rlwt, dst);
218 	if (unlikely(err))
219 		goto drop;
220 
221 	if (unlikely(!dst)) {
222 		struct ipv6hdr *hdr = ipv6_hdr(skb);
223 		struct flowi6 fl6;
224 
225 		memset(&fl6, 0, sizeof(fl6));
226 		fl6.daddr = hdr->daddr;
227 		fl6.saddr = hdr->saddr;
228 		fl6.flowlabel = ip6_flowinfo(hdr);
229 		fl6.flowi6_mark = skb->mark;
230 		fl6.flowi6_proto = hdr->nexthdr;
231 
232 		dst = ip6_route_output(net, NULL, &fl6);
233 		if (dst->error) {
234 			err = dst->error;
235 			dst_release(dst);
236 			goto drop;
237 		}
238 
239 		local_bh_disable();
240 		dst_cache_set_ip6(&rlwt->cache, dst, &fl6.saddr);
241 		local_bh_enable();
242 
243 		err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
244 		if (unlikely(err))
245 			goto drop;
246 	}
247 
248 	skb_dst_drop(skb);
249 	skb_dst_set(skb, dst);
250 
251 	return dst_output(net, sk, skb);
252 
253 drop:
254 	kfree_skb(skb);
255 	return err;
256 }
257 
rpl_input(struct sk_buff * skb)258 static int rpl_input(struct sk_buff *skb)
259 {
260 	struct dst_entry *orig_dst = skb_dst(skb);
261 	struct dst_entry *dst = NULL;
262 	struct lwtunnel_state *lwtst;
263 	struct rpl_lwt *rlwt;
264 	int err;
265 
266 	/* We cannot dereference "orig_dst" once ip6_route_input() or
267 	 * skb_dst_drop() is called. However, in order to detect a dst loop, we
268 	 * need the address of its lwtstate. So, save the address of lwtstate
269 	 * now and use it later as a comparison.
270 	 */
271 	lwtst = orig_dst->lwtstate;
272 
273 	rlwt = rpl_lwt_lwtunnel(lwtst);
274 
275 	local_bh_disable();
276 	dst = dst_cache_get(&rlwt->cache);
277 	local_bh_enable();
278 
279 	err = rpl_do_srh(skb, rlwt, dst);
280 	if (unlikely(err))
281 		goto drop;
282 
283 	if (!dst) {
284 		ip6_route_input(skb);
285 		dst = skb_dst(skb);
286 
287 		/* cache only if we don't create a dst reference loop */
288 		if (!dst->error && lwtst != dst->lwtstate) {
289 			local_bh_disable();
290 			dst_cache_set_ip6(&rlwt->cache, dst,
291 					  &ipv6_hdr(skb)->saddr);
292 			local_bh_enable();
293 		}
294 
295 		err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
296 		if (unlikely(err))
297 			goto drop;
298 	} else {
299 		skb_dst_drop(skb);
300 		skb_dst_set(skb, dst);
301 	}
302 
303 	return dst_input(skb);
304 
305 drop:
306 	kfree_skb(skb);
307 	return err;
308 }
309 
nla_put_rpl_srh(struct sk_buff * skb,int attrtype,struct rpl_iptunnel_encap * tuninfo)310 static int nla_put_rpl_srh(struct sk_buff *skb, int attrtype,
311 			   struct rpl_iptunnel_encap *tuninfo)
312 {
313 	struct rpl_iptunnel_encap *data;
314 	struct nlattr *nla;
315 	int len;
316 
317 	len = RPL_IPTUNNEL_SRH_SIZE(tuninfo->srh);
318 
319 	nla = nla_reserve(skb, attrtype, len);
320 	if (!nla)
321 		return -EMSGSIZE;
322 
323 	data = nla_data(nla);
324 	memcpy(data, tuninfo->srh, len);
325 
326 	return 0;
327 }
328 
rpl_fill_encap_info(struct sk_buff * skb,struct lwtunnel_state * lwtstate)329 static int rpl_fill_encap_info(struct sk_buff *skb,
330 			       struct lwtunnel_state *lwtstate)
331 {
332 	struct rpl_iptunnel_encap *tuninfo = rpl_encap_lwtunnel(lwtstate);
333 
334 	if (nla_put_rpl_srh(skb, RPL_IPTUNNEL_SRH, tuninfo))
335 		return -EMSGSIZE;
336 
337 	return 0;
338 }
339 
rpl_encap_nlsize(struct lwtunnel_state * lwtstate)340 static int rpl_encap_nlsize(struct lwtunnel_state *lwtstate)
341 {
342 	struct rpl_iptunnel_encap *tuninfo = rpl_encap_lwtunnel(lwtstate);
343 
344 	return nla_total_size(RPL_IPTUNNEL_SRH_SIZE(tuninfo->srh));
345 }
346 
rpl_encap_cmp(struct lwtunnel_state * a,struct lwtunnel_state * b)347 static int rpl_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
348 {
349 	struct rpl_iptunnel_encap *a_hdr = rpl_encap_lwtunnel(a);
350 	struct rpl_iptunnel_encap *b_hdr = rpl_encap_lwtunnel(b);
351 	int len = RPL_IPTUNNEL_SRH_SIZE(a_hdr->srh);
352 
353 	if (len != RPL_IPTUNNEL_SRH_SIZE(b_hdr->srh))
354 		return 1;
355 
356 	return memcmp(a_hdr, b_hdr, len);
357 }
358 
359 static const struct lwtunnel_encap_ops rpl_ops = {
360 	.build_state	= rpl_build_state,
361 	.destroy_state	= rpl_destroy_state,
362 	.output		= rpl_output,
363 	.input		= rpl_input,
364 	.fill_encap	= rpl_fill_encap_info,
365 	.get_encap_size	= rpl_encap_nlsize,
366 	.cmp_encap	= rpl_encap_cmp,
367 	.owner		= THIS_MODULE,
368 };
369 
rpl_init(void)370 int __init rpl_init(void)
371 {
372 	int err;
373 
374 	err = lwtunnel_encap_add_ops(&rpl_ops, LWTUNNEL_ENCAP_RPL);
375 	if (err)
376 		goto out;
377 
378 	pr_info("RPL Segment Routing with IPv6\n");
379 
380 	return 0;
381 
382 out:
383 	return err;
384 }
385 
rpl_exit(void)386 void rpl_exit(void)
387 {
388 	lwtunnel_encap_del_ops(&rpl_ops, LWTUNNEL_ENCAP_RPL);
389 }
390