ioam6_iptunnel.c

  1// SPDX-License-Identifier: GPL-2.0+
  2/*
  3 *  IPv6 IOAM Lightweight Tunnel implementation
  4 *
  5 *  Author:
  6 *  Justin Iurman <justin.iurman@uliege.be>
  7 */
  8
  9#include <linux/kernel.h>
 10#include <linux/skbuff.h>
 11#include <linux/net.h>
 12#include <linux/in6.h>
 13#include <linux/ioam6.h>
 14#include <linux/ioam6_iptunnel.h>
 15#include <net/dst.h>
 16#include <net/sock.h>
 17#include <net/lwtunnel.h>
 18#include <net/ioam6.h>
 19#include <net/netlink.h>
 20#include <net/ipv6.h>
 21#include <net/dst_cache.h>
 22#include <net/ip6_route.h>
 23#include <net/addrconf.h>
 24
 25struct ioam6_lwt_encap {
 26	struct ipv6_hopopt_hdr eh;
 27	u8 pad[2];			/* 2-octet padding for 4n-alignment */
 28	struct ioam6_hdr ioamh;
 29	struct ioam6_trace_hdr traceh;
 30} __packed;
 31
 32struct ioam6_lwt_freq {
 33	u32 k;
 34	u32 n;
 35};
 36
 37struct ioam6_lwt {
 38	struct dst_entry null_dst;
 39	struct dst_cache cache;
 40	struct ioam6_lwt_freq freq;
 41	atomic_t pkt_cnt;
 42	u8 mode;
 43	bool has_tunsrc;
 44	struct in6_addr tunsrc;
 45	struct in6_addr tundst;
 46	struct ioam6_lwt_encap tuninfo;
 47};
 48
 49static const struct netlink_range_validation freq_range = {
 50	.min = IOAM6_IPTUNNEL_FREQ_MIN,
 51	.max = IOAM6_IPTUNNEL_FREQ_MAX,
 52};
 53
 54static struct ioam6_lwt *ioam6_lwt_state(struct lwtunnel_state *lwt)
 55{
 56	return (struct ioam6_lwt *)lwt->data;
 57}
 58
 59static struct ioam6_lwt_encap *ioam6_lwt_info(struct lwtunnel_state *lwt)
 60{
 61	return &ioam6_lwt_state(lwt)->tuninfo;
 62}
 63
 64static struct ioam6_trace_hdr *ioam6_lwt_trace(struct lwtunnel_state *lwt)
 65{
 66	return &(ioam6_lwt_state(lwt)->tuninfo.traceh);
 67}
 68
 69static const struct nla_policy ioam6_iptunnel_policy[IOAM6_IPTUNNEL_MAX + 1] = {
 70	[IOAM6_IPTUNNEL_FREQ_K] = NLA_POLICY_FULL_RANGE(NLA_U32, &freq_range),
 71	[IOAM6_IPTUNNEL_FREQ_N] = NLA_POLICY_FULL_RANGE(NLA_U32, &freq_range),
 72	[IOAM6_IPTUNNEL_MODE]	= NLA_POLICY_RANGE(NLA_U8,
 73						   IOAM6_IPTUNNEL_MODE_MIN,
 74						   IOAM6_IPTUNNEL_MODE_MAX),
 75	[IOAM6_IPTUNNEL_SRC]	= NLA_POLICY_EXACT_LEN(sizeof(struct in6_addr)),
 76	[IOAM6_IPTUNNEL_DST]	= NLA_POLICY_EXACT_LEN(sizeof(struct in6_addr)),
 77	[IOAM6_IPTUNNEL_TRACE]	= NLA_POLICY_EXACT_LEN(
 78					sizeof(struct ioam6_trace_hdr)),
 79};
 80
 81static bool ioam6_validate_trace_hdr(struct ioam6_trace_hdr *trace)
 82{
 83	u32 fields;
 84
 85	if (!trace->type_be32 || !trace->remlen ||
 86	    trace->remlen > IOAM6_TRACE_DATA_SIZE_MAX / 4 ||
 87	    trace->type.bit12 | trace->type.bit13 | trace->type.bit14 |
 88	    trace->type.bit15 | trace->type.bit16 | trace->type.bit17 |
 89	    trace->type.bit18 | trace->type.bit19 | trace->type.bit20 |
 90	    trace->type.bit21 | trace->type.bit23)
 91		return false;
 92
 93	fields = be32_to_cpu(trace->type_be32);
 94	trace->nodelen = ioam6_trace_compute_nodelen(fields);
 95
 96	return true;
 97}
 98
 99static int ioam6_build_state(struct net *net, struct nlattr *nla,
100			     unsigned int family, const void *cfg,
101			     struct lwtunnel_state **ts,
102			     struct netlink_ext_ack *extack)
103{
104	struct nlattr *tb[IOAM6_IPTUNNEL_MAX + 1];
105	struct ioam6_lwt_encap *tuninfo;
106	struct ioam6_trace_hdr *trace;
107	struct lwtunnel_state *lwt;
108	struct ioam6_lwt *ilwt;
109	int len_aligned, err;
110	u32 freq_k, freq_n;
111	u8 mode;
112
113	if (family != AF_INET6)
114		return -EINVAL;
115
116	err = nla_parse_nested(tb, IOAM6_IPTUNNEL_MAX, nla,
117			       ioam6_iptunnel_policy, extack);
118	if (err < 0)
119		return err;
120
121	if ((!tb[IOAM6_IPTUNNEL_FREQ_K] && tb[IOAM6_IPTUNNEL_FREQ_N]) ||
122	    (tb[IOAM6_IPTUNNEL_FREQ_K] && !tb[IOAM6_IPTUNNEL_FREQ_N])) {
123		NL_SET_ERR_MSG(extack, "freq: missing parameter");
124		return -EINVAL;
125	} else if (!tb[IOAM6_IPTUNNEL_FREQ_K] && !tb[IOAM6_IPTUNNEL_FREQ_N]) {
126		freq_k = IOAM6_IPTUNNEL_FREQ_MIN;
127		freq_n = IOAM6_IPTUNNEL_FREQ_MIN;
128	} else {
129		freq_k = nla_get_u32(tb[IOAM6_IPTUNNEL_FREQ_K]);
130		freq_n = nla_get_u32(tb[IOAM6_IPTUNNEL_FREQ_N]);
131
132		if (freq_k > freq_n) {
133			NL_SET_ERR_MSG(extack, "freq: k > n is forbidden");
134			return -EINVAL;
135		}
136	}
137
138	mode = nla_get_u8_default(tb[IOAM6_IPTUNNEL_MODE],
139				  IOAM6_IPTUNNEL_MODE_INLINE);
140
141	if (tb[IOAM6_IPTUNNEL_SRC] && mode == IOAM6_IPTUNNEL_MODE_INLINE) {
142		NL_SET_ERR_MSG(extack, "no tunnel src expected with this mode");
143		return -EINVAL;
144	}
145
146	if (!tb[IOAM6_IPTUNNEL_DST] && mode != IOAM6_IPTUNNEL_MODE_INLINE) {
147		NL_SET_ERR_MSG(extack, "this mode needs a tunnel destination");
148		return -EINVAL;
149	}
150
151	if (!tb[IOAM6_IPTUNNEL_TRACE]) {
152		NL_SET_ERR_MSG(extack, "missing trace");
153		return -EINVAL;
154	}
155
156	trace = nla_data(tb[IOAM6_IPTUNNEL_TRACE]);
157	if (!ioam6_validate_trace_hdr(trace)) {
158		NL_SET_ERR_MSG_ATTR(extack, tb[IOAM6_IPTUNNEL_TRACE],
159				    "invalid trace validation");
160		return -EINVAL;
161	}
162
163	len_aligned = ALIGN(trace->remlen * 4, 8);
164	lwt = lwtunnel_state_alloc(sizeof(*ilwt) + len_aligned);
165	if (!lwt)
166		return -ENOMEM;
167
168	ilwt = ioam6_lwt_state(lwt);
169	err = dst_cache_init(&ilwt->cache, GFP_ATOMIC);
170	if (err)
171		goto free_lwt;
172
173	/* This "fake" dst_entry will be stored in a dst_cache, which will call
174	 * dst_hold() and dst_release() on it. We must ensure that dst_destroy()
175	 * will never be called. For that, its initial refcount is 1 and +1 when
176	 * it is stored in the cache. Then, +1/-1 each time we read the cache
177	 * and release it. Long story short, we're fine.
178	 */
179	dst_init(&ilwt->null_dst, NULL, NULL, DST_OBSOLETE_NONE, DST_NOCOUNT);
180
181	atomic_set(&ilwt->pkt_cnt, 0);
182	ilwt->freq.k = freq_k;
183	ilwt->freq.n = freq_n;
184
185	ilwt->mode = mode;
186
187	if (!tb[IOAM6_IPTUNNEL_SRC]) {
188		ilwt->has_tunsrc = false;
189	} else {
190		ilwt->has_tunsrc = true;
191		ilwt->tunsrc = nla_get_in6_addr(tb[IOAM6_IPTUNNEL_SRC]);
192
193		if (ipv6_addr_any(&ilwt->tunsrc)) {
194			NL_SET_ERR_MSG_ATTR(extack, tb[IOAM6_IPTUNNEL_SRC],
195					    "invalid tunnel source address");
196			err = -EINVAL;
197			goto free_cache;
198		}
199	}
200
201	if (tb[IOAM6_IPTUNNEL_DST]) {
202		ilwt->tundst = nla_get_in6_addr(tb[IOAM6_IPTUNNEL_DST]);
203
204		if (ipv6_addr_any(&ilwt->tundst)) {
205			NL_SET_ERR_MSG_ATTR(extack, tb[IOAM6_IPTUNNEL_DST],
206					    "invalid tunnel dest address");
207			err = -EINVAL;
208			goto free_cache;
209		}
210	}
211
212	tuninfo = ioam6_lwt_info(lwt);
213	tuninfo->eh.hdrlen = ((sizeof(*tuninfo) + len_aligned) >> 3) - 1;
214	tuninfo->pad[0] = IPV6_TLV_PADN;
215	tuninfo->ioamh.type = IOAM6_TYPE_PREALLOC;
216	tuninfo->ioamh.opt_type = IPV6_TLV_IOAM;
217	tuninfo->ioamh.opt_len = sizeof(tuninfo->ioamh) - 2 + sizeof(*trace)
218					+ trace->remlen * 4;
219
220	memcpy(&tuninfo->traceh, trace, sizeof(*trace));
221
222	if (len_aligned - trace->remlen * 4) {
223		tuninfo->traceh.data[trace->remlen * 4] = IPV6_TLV_PADN;
224		tuninfo->traceh.data[trace->remlen * 4 + 1] = 2;
225	}
226
227	lwt->type = LWTUNNEL_ENCAP_IOAM6;
228	lwt->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT;
229
230	*ts = lwt;
231
232	return 0;
233free_cache:
234	dst_cache_destroy(&ilwt->cache);
235free_lwt:
236	kfree(lwt);
237	return err;
238}
239
240static int ioam6_do_fill(struct net *net, struct sk_buff *skb)
241{
242	struct ioam6_trace_hdr *trace;
243	struct ioam6_namespace *ns;
244
245	trace = (struct ioam6_trace_hdr *)(skb_transport_header(skb)
246					   + sizeof(struct ipv6_hopopt_hdr) + 2
247					   + sizeof(struct ioam6_hdr));
248
249	ns = ioam6_namespace(net, trace->namespace_id);
250	if (ns)
251		ioam6_fill_trace_data(skb, ns, trace, false);
252
253	return 0;
254}
255
256static int ioam6_do_inline(struct net *net, struct sk_buff *skb,
257			   struct ioam6_lwt_encap *tuninfo,
258			   struct dst_entry *cache_dst)
259{
260	struct ipv6hdr *oldhdr, *hdr;
261	int hdrlen, err;
262
263	hdrlen = (tuninfo->eh.hdrlen + 1) << 3;
264
265	err = skb_cow_head(skb, hdrlen + dst_dev_overhead(cache_dst, skb));
266	if (unlikely(err))
267		return err;
268
269	oldhdr = ipv6_hdr(skb);
270	skb_pull(skb, sizeof(*oldhdr));
271	skb_postpull_rcsum(skb, skb_network_header(skb), sizeof(*oldhdr));
272
273	skb_push(skb, sizeof(*oldhdr) + hdrlen);
274	skb_reset_network_header(skb);
275	skb_mac_header_rebuild(skb);
276
277	hdr = ipv6_hdr(skb);
278	memmove(hdr, oldhdr, sizeof(*oldhdr));
279	tuninfo->eh.nexthdr = hdr->nexthdr;
280
281	skb_set_transport_header(skb, sizeof(*hdr));
282	skb_postpush_rcsum(skb, hdr, sizeof(*hdr) + hdrlen);
283
284	memcpy(skb_transport_header(skb), (u8 *)tuninfo, hdrlen);
285
286	hdr->nexthdr = NEXTHDR_HOP;
287	hdr->payload_len = cpu_to_be16(skb->len - sizeof(*hdr));
288
289	return ioam6_do_fill(net, skb);
290}
291
292static int ioam6_do_encap(struct net *net, struct sk_buff *skb,
293			  struct ioam6_lwt_encap *tuninfo,
294			  bool has_tunsrc,
295			  struct in6_addr *tunsrc,
296			  struct in6_addr *tundst,
297			  struct dst_entry *cache_dst)
298{
299	struct dst_entry *dst = skb_dst(skb);
300	struct ipv6hdr *hdr, *inner_hdr;
301	int hdrlen, len, err;
302
303	hdrlen = (tuninfo->eh.hdrlen + 1) << 3;
304	len = sizeof(*hdr) + hdrlen;
305
306	err = skb_cow_head(skb, len + dst_dev_overhead(cache_dst, skb));
307	if (unlikely(err))
308		return err;
309
310	inner_hdr = ipv6_hdr(skb);
311
312	skb_push(skb, len);
313	skb_reset_network_header(skb);
314	skb_mac_header_rebuild(skb);
315	skb_set_transport_header(skb, sizeof(*hdr));
316
317	tuninfo->eh.nexthdr = NEXTHDR_IPV6;
318	memcpy(skb_transport_header(skb), (u8 *)tuninfo, hdrlen);
319
320	hdr = ipv6_hdr(skb);
321	memcpy(hdr, inner_hdr, sizeof(*hdr));
322
323	hdr->nexthdr = NEXTHDR_HOP;
324	hdr->payload_len = cpu_to_be16(skb->len - sizeof(*hdr));
325	hdr->daddr = *tundst;
326
327	if (has_tunsrc)
328		memcpy(&hdr->saddr, tunsrc, sizeof(*tunsrc));
329	else
330		ipv6_dev_get_saddr(net, dst_dev(dst), &hdr->daddr,
331				   IPV6_PREFER_SRC_PUBLIC, &hdr->saddr);
332
333	skb_postpush_rcsum(skb, hdr, len);
334
335	return ioam6_do_fill(net, skb);
336}
337
338static int ioam6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
339{
340	struct dst_entry *orig_dst = skb_dst(skb);
341	struct dst_entry *dst = NULL;
342	struct ioam6_lwt *ilwt;
343	int err = -EINVAL;
344	u32 pkt_cnt;
345
346	if (skb->protocol != htons(ETH_P_IPV6))
347		goto drop;
348
349	ilwt = ioam6_lwt_state(orig_dst->lwtstate);
350
351	/* Check for insertion frequency (i.e., "k over n" insertions) */
352	pkt_cnt = atomic_fetch_inc(&ilwt->pkt_cnt);
353	if (pkt_cnt % ilwt->freq.n >= ilwt->freq.k)
354		goto out;
355
356	local_bh_disable();
357	dst = dst_cache_get(&ilwt->cache);
358	local_bh_enable();
359
360	/* This is how we notify that the destination does not change after
361	 * transformation and that we need to use orig_dst instead of the cache
362	 */
363	if (dst == &ilwt->null_dst) {
364		dst_release(dst);
365
366		dst = orig_dst;
367		/* keep refcount balance: dst_release() is called at the end */
368		dst_hold(dst);
369	}
370
371	switch (ilwt->mode) {
372	case IOAM6_IPTUNNEL_MODE_INLINE:
373do_inline:
374		/* Direct insertion - if there is no Hop-by-Hop yet */
375		if (ipv6_hdr(skb)->nexthdr == NEXTHDR_HOP)
376			goto out;
377
378		err = ioam6_do_inline(net, skb, &ilwt->tuninfo, dst);
379		if (unlikely(err))
380			goto drop;
381
382		break;
383	case IOAM6_IPTUNNEL_MODE_ENCAP:
384do_encap:
385		/* Encapsulation (ip6ip6) */
386		err = ioam6_do_encap(net, skb, &ilwt->tuninfo,
387				     ilwt->has_tunsrc, &ilwt->tunsrc,
388				     &ilwt->tundst, dst);
389		if (unlikely(err))
390			goto drop;
391
392		break;
393	case IOAM6_IPTUNNEL_MODE_AUTO:
394		/* Automatic (RFC8200 compliant):
395		 *  - local packets -> INLINE mode
396		 *  - in-transit packets -> ENCAP mode
397		 */
398		if (!skb->dev)
399			goto do_inline;
400
401		goto do_encap;
402	default:
403		goto drop;
404	}
405
406	if (unlikely(!dst)) {
407		struct ipv6hdr *hdr = ipv6_hdr(skb);
408		struct flowi6 fl6;
409
410		memset(&fl6, 0, sizeof(fl6));
411		fl6.daddr = hdr->daddr;
412		fl6.saddr = hdr->saddr;
413		fl6.flowlabel = ip6_flowinfo(hdr);
414		fl6.flowi6_mark = skb->mark;
415		fl6.flowi6_proto = hdr->nexthdr;
416
417		dst = ip6_route_output(net, NULL, &fl6);
418		if (dst->error) {
419			err = dst->error;
420			goto drop;
421		}
422
423		/* If the destination is the same after transformation (which is
424		 * a valid use case for IOAM), then we don't want to add it to
425		 * the cache in order to avoid a reference loop. Instead, we add
426		 * our fake dst_entry to the cache as a way to detect this case.
427		 * Otherwise, we add the resolved destination to the cache.
428		 */
429		local_bh_disable();
430		if (orig_dst->lwtstate == dst->lwtstate)
431			dst_cache_set_ip6(&ilwt->cache,
432					  &ilwt->null_dst, &fl6.saddr);
433		else
434			dst_cache_set_ip6(&ilwt->cache, dst, &fl6.saddr);
435		local_bh_enable();
436
437		err = skb_cow_head(skb, LL_RESERVED_SPACE(dst_dev(dst)));
438		if (unlikely(err))
439			goto drop;
440	}
441
442	/* avoid lwtunnel_output() reentry loop when destination is the same
443	 * after transformation (e.g., with the inline mode)
444	 */
445	if (orig_dst->lwtstate != dst->lwtstate) {
446		skb_dst_drop(skb);
447		skb_dst_set(skb, dst);
448		return dst_output(net, sk, skb);
449	}
450out:
451	dst_release(dst);
452	return orig_dst->lwtstate->orig_output(net, sk, skb);
453drop:
454	dst_release(dst);
455	kfree_skb(skb);
456	return err;
457}
458
459static void ioam6_destroy_state(struct lwtunnel_state *lwt)
460{
461	/* Since the refcount of per-cpu dst_entry caches will never be 0 (see
462	 * why above) when our "fake" dst_entry is used, it is not necessary to
463	 * remove them before calling dst_cache_destroy()
464	 */
465	dst_cache_destroy(&ioam6_lwt_state(lwt)->cache);
466}
467
468static int ioam6_fill_encap_info(struct sk_buff *skb,
469				 struct lwtunnel_state *lwtstate)
470{
471	struct ioam6_lwt *ilwt = ioam6_lwt_state(lwtstate);
472	int err;
473
474	err = nla_put_u32(skb, IOAM6_IPTUNNEL_FREQ_K, ilwt->freq.k);
475	if (err)
476		goto ret;
477
478	err = nla_put_u32(skb, IOAM6_IPTUNNEL_FREQ_N, ilwt->freq.n);
479	if (err)
480		goto ret;
481
482	err = nla_put_u8(skb, IOAM6_IPTUNNEL_MODE, ilwt->mode);
483	if (err)
484		goto ret;
485
486	if (ilwt->mode != IOAM6_IPTUNNEL_MODE_INLINE) {
487		if (ilwt->has_tunsrc) {
488			err = nla_put_in6_addr(skb, IOAM6_IPTUNNEL_SRC,
489					       &ilwt->tunsrc);
490			if (err)
491				goto ret;
492		}
493
494		err = nla_put_in6_addr(skb, IOAM6_IPTUNNEL_DST, &ilwt->tundst);
495		if (err)
496			goto ret;
497	}
498
499	err = nla_put(skb, IOAM6_IPTUNNEL_TRACE, sizeof(ilwt->tuninfo.traceh),
500		      &ilwt->tuninfo.traceh);
501ret:
502	return err;
503}
504
505static int ioam6_encap_nlsize(struct lwtunnel_state *lwtstate)
506{
507	struct ioam6_lwt *ilwt = ioam6_lwt_state(lwtstate);
508	int nlsize;
509
510	nlsize = nla_total_size(sizeof(ilwt->freq.k)) +
511		  nla_total_size(sizeof(ilwt->freq.n)) +
512		  nla_total_size(sizeof(ilwt->mode)) +
513		  nla_total_size(sizeof(ilwt->tuninfo.traceh));
514
515	if (ilwt->mode != IOAM6_IPTUNNEL_MODE_INLINE) {
516		if (ilwt->has_tunsrc)
517			nlsize += nla_total_size(sizeof(ilwt->tunsrc));
518
519		nlsize += nla_total_size(sizeof(ilwt->tundst));
520	}
521
522	return nlsize;
523}
524
525static int ioam6_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
526{
527	struct ioam6_trace_hdr *trace_a = ioam6_lwt_trace(a);
528	struct ioam6_trace_hdr *trace_b = ioam6_lwt_trace(b);
529	struct ioam6_lwt *ilwt_a = ioam6_lwt_state(a);
530	struct ioam6_lwt *ilwt_b = ioam6_lwt_state(b);
531
532	return (ilwt_a->freq.k != ilwt_b->freq.k ||
533		ilwt_a->freq.n != ilwt_b->freq.n ||
534		ilwt_a->mode != ilwt_b->mode ||
535		ilwt_a->has_tunsrc != ilwt_b->has_tunsrc ||
536		(ilwt_a->mode != IOAM6_IPTUNNEL_MODE_INLINE &&
537		 !ipv6_addr_equal(&ilwt_a->tundst, &ilwt_b->tundst)) ||
538		(ilwt_a->mode != IOAM6_IPTUNNEL_MODE_INLINE &&
539		 ilwt_a->has_tunsrc &&
540		 !ipv6_addr_equal(&ilwt_a->tunsrc, &ilwt_b->tunsrc)) ||
541		trace_a->namespace_id != trace_b->namespace_id);
542}
543
544static const struct lwtunnel_encap_ops ioam6_iptun_ops = {
545	.build_state		= ioam6_build_state,
546	.destroy_state		= ioam6_destroy_state,
547	.output			= ioam6_output,
548	.fill_encap		= ioam6_fill_encap_info,
549	.get_encap_size		= ioam6_encap_nlsize,
550	.cmp_encap		= ioam6_encap_cmp,
551	.owner			= THIS_MODULE,
552};
553
554int __init ioam6_iptunnel_init(void)
555{
556	return lwtunnel_encap_add_ops(&ioam6_iptun_ops, LWTUNNEL_ENCAP_IOAM6);
557}
558
559void ioam6_iptunnel_exit(void)
560{
561	lwtunnel_encap_del_ops(&ioam6_iptun_ops, LWTUNNEL_ENCAP_IOAM6);
562}