1
2
3
4
5#include <linux/kernel.h>
6#include <linux/module.h>
7#include <linux/skbuff.h>
8#include <linux/types.h>
9#include <linux/bpf.h>
10#include <net/lwtunnel.h>
11#include <net/gre.h>
12#include <net/ip6_route.h>
13#include <net/ipv6_stubs.h>
14
15struct bpf_lwt_prog {
16 struct bpf_prog *prog;
17 char *name;
18};
19
20struct bpf_lwt {
21 struct bpf_lwt_prog in;
22 struct bpf_lwt_prog out;
23 struct bpf_lwt_prog xmit;
24 int family;
25};
26
27#define MAX_PROG_NAME 256
28
29static inline struct bpf_lwt *bpf_lwt_lwtunnel(struct lwtunnel_state *lwt)
30{
31 return (struct bpf_lwt *)lwt->data;
32}
33
34#define NO_REDIRECT false
35#define CAN_REDIRECT true
36
37static int run_lwt_bpf(struct sk_buff *skb, struct bpf_lwt_prog *lwt,
38 struct dst_entry *dst, bool can_redirect)
39{
40 int ret;
41
42
43
44
45
46
47 preempt_disable();
48 bpf_compute_data_pointers(skb);
49 ret = bpf_prog_run_save_cb(lwt->prog, skb);
50
51 switch (ret) {
52 case BPF_OK:
53 case BPF_LWT_REROUTE:
54 break;
55
56 case BPF_REDIRECT:
57 if (unlikely(!can_redirect)) {
58 pr_warn_once("Illegal redirect return code in prog %s\n",
59 lwt->name ? : "<unknown>");
60 ret = BPF_OK;
61 } else {
62 skb_reset_mac_header(skb);
63 ret = skb_do_redirect(skb);
64 if (ret == 0)
65 ret = BPF_REDIRECT;
66 }
67 break;
68
69 case BPF_DROP:
70 kfree_skb(skb);
71 ret = -EPERM;
72 break;
73
74 default:
75 pr_warn_once("bpf-lwt: Illegal return value %u, expect packet loss\n", ret);
76 kfree_skb(skb);
77 ret = -EINVAL;
78 break;
79 }
80
81 preempt_enable();
82
83 return ret;
84}
85
86static int bpf_lwt_input_reroute(struct sk_buff *skb)
87{
88 int err = -EINVAL;
89
90 if (skb->protocol == htons(ETH_P_IP)) {
91 struct iphdr *iph = ip_hdr(skb);
92
93 err = ip_route_input_noref(skb, iph->daddr, iph->saddr,
94 iph->tos, skb_dst(skb)->dev);
95 } else if (skb->protocol == htons(ETH_P_IPV6)) {
96 err = ipv6_stub->ipv6_route_input(skb);
97 } else {
98 err = -EAFNOSUPPORT;
99 }
100
101 if (err)
102 goto err;
103 return dst_input(skb);
104
105err:
106 kfree_skb(skb);
107 return err;
108}
109
110static int bpf_input(struct sk_buff *skb)
111{
112 struct dst_entry *dst = skb_dst(skb);
113 struct bpf_lwt *bpf;
114 int ret;
115
116 bpf = bpf_lwt_lwtunnel(dst->lwtstate);
117 if (bpf->in.prog) {
118 ret = run_lwt_bpf(skb, &bpf->in, dst, NO_REDIRECT);
119 if (ret < 0)
120 return ret;
121 if (ret == BPF_LWT_REROUTE)
122 return bpf_lwt_input_reroute(skb);
123 }
124
125 if (unlikely(!dst->lwtstate->orig_input)) {
126 kfree_skb(skb);
127 return -EINVAL;
128 }
129
130 return dst->lwtstate->orig_input(skb);
131}
132
133static int bpf_output(struct net *net, struct sock *sk, struct sk_buff *skb)
134{
135 struct dst_entry *dst = skb_dst(skb);
136 struct bpf_lwt *bpf;
137 int ret;
138
139 bpf = bpf_lwt_lwtunnel(dst->lwtstate);
140 if (bpf->out.prog) {
141 ret = run_lwt_bpf(skb, &bpf->out, dst, NO_REDIRECT);
142 if (ret < 0)
143 return ret;
144 }
145
146 if (unlikely(!dst->lwtstate->orig_output)) {
147 pr_warn_once("orig_output not set on dst for prog %s\n",
148 bpf->out.name);
149 kfree_skb(skb);
150 return -EINVAL;
151 }
152
153 return dst->lwtstate->orig_output(net, sk, skb);
154}
155
156static int xmit_check_hhlen(struct sk_buff *skb)
157{
158 int hh_len = skb_dst(skb)->dev->hard_header_len;
159
160 if (skb_headroom(skb) < hh_len) {
161 int nhead = HH_DATA_ALIGN(hh_len - skb_headroom(skb));
162
163 if (pskb_expand_head(skb, nhead, 0, GFP_ATOMIC))
164 return -ENOMEM;
165 }
166
167 return 0;
168}
169
170static int bpf_lwt_xmit_reroute(struct sk_buff *skb)
171{
172 struct net_device *l3mdev = l3mdev_master_dev_rcu(skb_dst(skb)->dev);
173 int oif = l3mdev ? l3mdev->ifindex : 0;
174 struct dst_entry *dst = NULL;
175 int err = -EAFNOSUPPORT;
176 struct sock *sk;
177 struct net *net;
178 bool ipv4;
179
180 if (skb->protocol == htons(ETH_P_IP))
181 ipv4 = true;
182 else if (skb->protocol == htons(ETH_P_IPV6))
183 ipv4 = false;
184 else
185 goto err;
186
187 sk = sk_to_full_sk(skb->sk);
188 if (sk) {
189 if (sk->sk_bound_dev_if)
190 oif = sk->sk_bound_dev_if;
191 net = sock_net(sk);
192 } else {
193 net = dev_net(skb_dst(skb)->dev);
194 }
195
196 if (ipv4) {
197 struct iphdr *iph = ip_hdr(skb);
198 struct flowi4 fl4 = {};
199 struct rtable *rt;
200
201 fl4.flowi4_oif = oif;
202 fl4.flowi4_mark = skb->mark;
203 fl4.flowi4_uid = sock_net_uid(net, sk);
204 fl4.flowi4_tos = RT_TOS(iph->tos);
205 fl4.flowi4_flags = FLOWI_FLAG_ANYSRC;
206 fl4.flowi4_proto = iph->protocol;
207 fl4.daddr = iph->daddr;
208 fl4.saddr = iph->saddr;
209
210 rt = ip_route_output_key(net, &fl4);
211 if (IS_ERR(rt)) {
212 err = PTR_ERR(rt);
213 goto err;
214 }
215 dst = &rt->dst;
216 } else {
217 struct ipv6hdr *iph6 = ipv6_hdr(skb);
218 struct flowi6 fl6 = {};
219
220 fl6.flowi6_oif = oif;
221 fl6.flowi6_mark = skb->mark;
222 fl6.flowi6_uid = sock_net_uid(net, sk);
223 fl6.flowlabel = ip6_flowinfo(iph6);
224 fl6.flowi6_proto = iph6->nexthdr;
225 fl6.daddr = iph6->daddr;
226 fl6.saddr = iph6->saddr;
227
228 err = ipv6_stub->ipv6_dst_lookup(net, skb->sk, &dst, &fl6);
229 if (unlikely(err))
230 goto err;
231 if (IS_ERR(dst)) {
232 err = PTR_ERR(dst);
233 goto err;
234 }
235 }
236 if (unlikely(dst->error)) {
237 err = dst->error;
238 dst_release(dst);
239 goto err;
240 }
241
242
243
244
245
246
247 err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
248 if (unlikely(err))
249 goto err;
250
251 skb_dst_drop(skb);
252 skb_dst_set(skb, dst);
253
254 err = dst_output(dev_net(skb_dst(skb)->dev), skb->sk, skb);
255 if (unlikely(err))
256 return err;
257
258
259 return LWTUNNEL_XMIT_DONE;
260
261err:
262 kfree_skb(skb);
263 return err;
264}
265
266static int bpf_xmit(struct sk_buff *skb)
267{
268 struct dst_entry *dst = skb_dst(skb);
269 struct bpf_lwt *bpf;
270
271 bpf = bpf_lwt_lwtunnel(dst->lwtstate);
272 if (bpf->xmit.prog) {
273 __be16 proto = skb->protocol;
274 int ret;
275
276 ret = run_lwt_bpf(skb, &bpf->xmit, dst, CAN_REDIRECT);
277 switch (ret) {
278 case BPF_OK:
279
280
281
282
283 if (skb->protocol != proto) {
284 kfree_skb(skb);
285 return -EINVAL;
286 }
287
288
289
290 ret = xmit_check_hhlen(skb);
291 if (unlikely(ret))
292 return ret;
293
294 return LWTUNNEL_XMIT_CONTINUE;
295 case BPF_REDIRECT:
296 return LWTUNNEL_XMIT_DONE;
297 case BPF_LWT_REROUTE:
298 return bpf_lwt_xmit_reroute(skb);
299 default:
300 return ret;
301 }
302 }
303
304 return LWTUNNEL_XMIT_CONTINUE;
305}
306
307static void bpf_lwt_prog_destroy(struct bpf_lwt_prog *prog)
308{
309 if (prog->prog)
310 bpf_prog_put(prog->prog);
311
312 kfree(prog->name);
313}
314
315static void bpf_destroy_state(struct lwtunnel_state *lwt)
316{
317 struct bpf_lwt *bpf = bpf_lwt_lwtunnel(lwt);
318
319 bpf_lwt_prog_destroy(&bpf->in);
320 bpf_lwt_prog_destroy(&bpf->out);
321 bpf_lwt_prog_destroy(&bpf->xmit);
322}
323
324static const struct nla_policy bpf_prog_policy[LWT_BPF_PROG_MAX + 1] = {
325 [LWT_BPF_PROG_FD] = { .type = NLA_U32, },
326 [LWT_BPF_PROG_NAME] = { .type = NLA_NUL_STRING,
327 .len = MAX_PROG_NAME },
328};
329
330static int bpf_parse_prog(struct nlattr *attr, struct bpf_lwt_prog *prog,
331 enum bpf_prog_type type)
332{
333 struct nlattr *tb[LWT_BPF_PROG_MAX + 1];
334 struct bpf_prog *p;
335 int ret;
336 u32 fd;
337
338 ret = nla_parse_nested_deprecated(tb, LWT_BPF_PROG_MAX, attr,
339 bpf_prog_policy, NULL);
340 if (ret < 0)
341 return ret;
342
343 if (!tb[LWT_BPF_PROG_FD] || !tb[LWT_BPF_PROG_NAME])
344 return -EINVAL;
345
346 prog->name = nla_memdup(tb[LWT_BPF_PROG_NAME], GFP_ATOMIC);
347 if (!prog->name)
348 return -ENOMEM;
349
350 fd = nla_get_u32(tb[LWT_BPF_PROG_FD]);
351 p = bpf_prog_get_type(fd, type);
352 if (IS_ERR(p))
353 return PTR_ERR(p);
354
355 prog->prog = p;
356
357 return 0;
358}
359
360static const struct nla_policy bpf_nl_policy[LWT_BPF_MAX + 1] = {
361 [LWT_BPF_IN] = { .type = NLA_NESTED, },
362 [LWT_BPF_OUT] = { .type = NLA_NESTED, },
363 [LWT_BPF_XMIT] = { .type = NLA_NESTED, },
364 [LWT_BPF_XMIT_HEADROOM] = { .type = NLA_U32 },
365};
366
367static int bpf_build_state(struct nlattr *nla,
368 unsigned int family, const void *cfg,
369 struct lwtunnel_state **ts,
370 struct netlink_ext_ack *extack)
371{
372 struct nlattr *tb[LWT_BPF_MAX + 1];
373 struct lwtunnel_state *newts;
374 struct bpf_lwt *bpf;
375 int ret;
376
377 if (family != AF_INET && family != AF_INET6)
378 return -EAFNOSUPPORT;
379
380 ret = nla_parse_nested_deprecated(tb, LWT_BPF_MAX, nla, bpf_nl_policy,
381 extack);
382 if (ret < 0)
383 return ret;
384
385 if (!tb[LWT_BPF_IN] && !tb[LWT_BPF_OUT] && !tb[LWT_BPF_XMIT])
386 return -EINVAL;
387
388 newts = lwtunnel_state_alloc(sizeof(*bpf));
389 if (!newts)
390 return -ENOMEM;
391
392 newts->type = LWTUNNEL_ENCAP_BPF;
393 bpf = bpf_lwt_lwtunnel(newts);
394
395 if (tb[LWT_BPF_IN]) {
396 newts->flags |= LWTUNNEL_STATE_INPUT_REDIRECT;
397 ret = bpf_parse_prog(tb[LWT_BPF_IN], &bpf->in,
398 BPF_PROG_TYPE_LWT_IN);
399 if (ret < 0)
400 goto errout;
401 }
402
403 if (tb[LWT_BPF_OUT]) {
404 newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT;
405 ret = bpf_parse_prog(tb[LWT_BPF_OUT], &bpf->out,
406 BPF_PROG_TYPE_LWT_OUT);
407 if (ret < 0)
408 goto errout;
409 }
410
411 if (tb[LWT_BPF_XMIT]) {
412 newts->flags |= LWTUNNEL_STATE_XMIT_REDIRECT;
413 ret = bpf_parse_prog(tb[LWT_BPF_XMIT], &bpf->xmit,
414 BPF_PROG_TYPE_LWT_XMIT);
415 if (ret < 0)
416 goto errout;
417 }
418
419 if (tb[LWT_BPF_XMIT_HEADROOM]) {
420 u32 headroom = nla_get_u32(tb[LWT_BPF_XMIT_HEADROOM]);
421
422 if (headroom > LWT_BPF_MAX_HEADROOM) {
423 ret = -ERANGE;
424 goto errout;
425 }
426
427 newts->headroom = headroom;
428 }
429
430 bpf->family = family;
431 *ts = newts;
432
433 return 0;
434
435errout:
436 bpf_destroy_state(newts);
437 kfree(newts);
438 return ret;
439}
440
441static int bpf_fill_lwt_prog(struct sk_buff *skb, int attr,
442 struct bpf_lwt_prog *prog)
443{
444 struct nlattr *nest;
445
446 if (!prog->prog)
447 return 0;
448
449 nest = nla_nest_start_noflag(skb, attr);
450 if (!nest)
451 return -EMSGSIZE;
452
453 if (prog->name &&
454 nla_put_string(skb, LWT_BPF_PROG_NAME, prog->name))
455 return -EMSGSIZE;
456
457 return nla_nest_end(skb, nest);
458}
459
460static int bpf_fill_encap_info(struct sk_buff *skb, struct lwtunnel_state *lwt)
461{
462 struct bpf_lwt *bpf = bpf_lwt_lwtunnel(lwt);
463
464 if (bpf_fill_lwt_prog(skb, LWT_BPF_IN, &bpf->in) < 0 ||
465 bpf_fill_lwt_prog(skb, LWT_BPF_OUT, &bpf->out) < 0 ||
466 bpf_fill_lwt_prog(skb, LWT_BPF_XMIT, &bpf->xmit) < 0)
467 return -EMSGSIZE;
468
469 return 0;
470}
471
472static int bpf_encap_nlsize(struct lwtunnel_state *lwtstate)
473{
474 int nest_len = nla_total_size(sizeof(struct nlattr)) +
475 nla_total_size(MAX_PROG_NAME) +
476 0;
477
478 return nest_len +
479 nest_len +
480 nest_len +
481 0;
482}
483
484static int bpf_lwt_prog_cmp(struct bpf_lwt_prog *a, struct bpf_lwt_prog *b)
485{
486
487
488
489
490 if (!a->name && !b->name)
491 return 0;
492
493 if (!a->name || !b->name)
494 return 1;
495
496 return strcmp(a->name, b->name);
497}
498
499static int bpf_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
500{
501 struct bpf_lwt *a_bpf = bpf_lwt_lwtunnel(a);
502 struct bpf_lwt *b_bpf = bpf_lwt_lwtunnel(b);
503
504 return bpf_lwt_prog_cmp(&a_bpf->in, &b_bpf->in) ||
505 bpf_lwt_prog_cmp(&a_bpf->out, &b_bpf->out) ||
506 bpf_lwt_prog_cmp(&a_bpf->xmit, &b_bpf->xmit);
507}
508
509static const struct lwtunnel_encap_ops bpf_encap_ops = {
510 .build_state = bpf_build_state,
511 .destroy_state = bpf_destroy_state,
512 .input = bpf_input,
513 .output = bpf_output,
514 .xmit = bpf_xmit,
515 .fill_encap = bpf_fill_encap_info,
516 .get_encap_size = bpf_encap_nlsize,
517 .cmp_encap = bpf_encap_cmp,
518 .owner = THIS_MODULE,
519};
520
521static int handle_gso_type(struct sk_buff *skb, unsigned int gso_type,
522 int encap_len)
523{
524 struct skb_shared_info *shinfo = skb_shinfo(skb);
525
526 gso_type |= SKB_GSO_DODGY;
527 shinfo->gso_type |= gso_type;
528 skb_decrease_gso_size(shinfo, encap_len);
529 shinfo->gso_segs = 0;
530 return 0;
531}
532
533static int handle_gso_encap(struct sk_buff *skb, bool ipv4, int encap_len)
534{
535 int next_hdr_offset;
536 void *next_hdr;
537 __u8 protocol;
538
539
540
541
542
543 if (!(skb_shinfo(skb)->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6)))
544 return -ENOTSUPP;
545
546 if (ipv4) {
547 protocol = ip_hdr(skb)->protocol;
548 next_hdr_offset = sizeof(struct iphdr);
549 next_hdr = skb_network_header(skb) + next_hdr_offset;
550 } else {
551 protocol = ipv6_hdr(skb)->nexthdr;
552 next_hdr_offset = sizeof(struct ipv6hdr);
553 next_hdr = skb_network_header(skb) + next_hdr_offset;
554 }
555
556 switch (protocol) {
557 case IPPROTO_GRE:
558 next_hdr_offset += sizeof(struct gre_base_hdr);
559 if (next_hdr_offset > encap_len)
560 return -EINVAL;
561
562 if (((struct gre_base_hdr *)next_hdr)->flags & GRE_CSUM)
563 return handle_gso_type(skb, SKB_GSO_GRE_CSUM,
564 encap_len);
565 return handle_gso_type(skb, SKB_GSO_GRE, encap_len);
566
567 case IPPROTO_UDP:
568 next_hdr_offset += sizeof(struct udphdr);
569 if (next_hdr_offset > encap_len)
570 return -EINVAL;
571
572 if (((struct udphdr *)next_hdr)->check)
573 return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL_CSUM,
574 encap_len);
575 return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL, encap_len);
576
577 case IPPROTO_IP:
578 case IPPROTO_IPV6:
579 if (ipv4)
580 return handle_gso_type(skb, SKB_GSO_IPXIP4, encap_len);
581 else
582 return handle_gso_type(skb, SKB_GSO_IPXIP6, encap_len);
583
584 default:
585 return -EPROTONOSUPPORT;
586 }
587}
588
589int bpf_lwt_push_ip_encap(struct sk_buff *skb, void *hdr, u32 len, bool ingress)
590{
591 struct iphdr *iph;
592 bool ipv4;
593 int err;
594
595 if (unlikely(len < sizeof(struct iphdr) || len > LWT_BPF_MAX_HEADROOM))
596 return -EINVAL;
597
598
599 iph = (struct iphdr *)hdr;
600 if (iph->version == 4) {
601 ipv4 = true;
602 if (unlikely(len < iph->ihl * 4))
603 return -EINVAL;
604 } else if (iph->version == 6) {
605 ipv4 = false;
606 if (unlikely(len < sizeof(struct ipv6hdr)))
607 return -EINVAL;
608 } else {
609 return -EINVAL;
610 }
611
612 if (ingress)
613 err = skb_cow_head(skb, len + skb->mac_len);
614 else
615 err = skb_cow_head(skb,
616 len + LL_RESERVED_SPACE(skb_dst(skb)->dev));
617 if (unlikely(err))
618 return err;
619
620
621 skb_reset_inner_headers(skb);
622 skb_reset_inner_mac_header(skb);
623 skb_set_inner_protocol(skb, skb->protocol);
624 skb->encapsulation = 1;
625 skb_push(skb, len);
626 if (ingress)
627 skb_postpush_rcsum(skb, iph, len);
628 skb_reset_network_header(skb);
629 memcpy(skb_network_header(skb), hdr, len);
630 bpf_compute_data_pointers(skb);
631 skb_clear_hash(skb);
632
633 if (ipv4) {
634 skb->protocol = htons(ETH_P_IP);
635 iph = ip_hdr(skb);
636
637 if (!iph->check)
638 iph->check = ip_fast_csum((unsigned char *)iph,
639 iph->ihl);
640 } else {
641 skb->protocol = htons(ETH_P_IPV6);
642 }
643
644 if (skb_is_gso(skb))
645 return handle_gso_encap(skb, ipv4, len);
646
647 return 0;
648}
649
650static int __init bpf_lwt_init(void)
651{
652 return lwtunnel_encap_add_ops(&bpf_encap_ops, LWTUNNEL_ENCAP_BPF);
653}
654
655subsys_initcall(bpf_lwt_init)
656
