xref: /openbmc/linux/net/ipv4/tcp_bpf.c (revision 9b358af7) 
1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2017 - 2018 Covalent IO, Inc. http://covalent.io */
3 
4 #include <linux/skmsg.h>
5 #include <linux/filter.h>
6 #include <linux/bpf.h>
7 #include <linux/init.h>
8 #include <linux/wait.h>
9 
10 #include <net/inet_common.h>
11 #include <net/tls.h>
12 
13 static int bpf_tcp_ingress(struct sock *sk, struct sk_psock *psock,
14 			   struct sk_msg *msg, u32 apply_bytes, int flags)
15 {
16 	bool apply = apply_bytes;
17 	struct scatterlist *sge;
18 	u32 size, copied = 0;
19 	struct sk_msg *tmp;
20 	int i, ret = 0;
21 
22 	tmp = kzalloc(sizeof(*tmp), __GFP_NOWARN | GFP_KERNEL);
23 	if (unlikely(!tmp))
24 		return -ENOMEM;
25 
26 	lock_sock(sk);
27 	tmp->sg.start = msg->sg.start;
28 	i = msg->sg.start;
29 	do {
30 		sge = sk_msg_elem(msg, i);
31 		size = (apply && apply_bytes < sge->length) ?
32 			apply_bytes : sge->length;
33 		if (!sk_wmem_schedule(sk, size)) {
34 			if (!copied)
35 				ret = -ENOMEM;
36 			break;
37 		}
38 
39 		sk_mem_charge(sk, size);
40 		sk_msg_xfer(tmp, msg, i, size);
41 		copied += size;
42 		if (sge->length)
43 			get_page(sk_msg_page(tmp, i));
44 		sk_msg_iter_var_next(i);
45 		tmp->sg.end = i;
46 		if (apply) {
47 			apply_bytes -= size;
48 			if (!apply_bytes)
49 				break;
50 		}
51 	} while (i != msg->sg.end);
52 
53 	if (!ret) {
54 		msg->sg.start = i;
55 		sk_psock_queue_msg(psock, tmp);
56 		sk_psock_data_ready(sk, psock);
57 	} else {
58 		sk_msg_free(sk, tmp);
59 		kfree(tmp);
60 	}
61 
62 	release_sock(sk);
63 	return ret;
64 }
65 
66 static int tcp_bpf_push(struct sock *sk, struct sk_msg *msg, u32 apply_bytes,
67 			int flags, bool uncharge)
68 {
69 	bool apply = apply_bytes;
70 	struct scatterlist *sge;
71 	struct page *page;
72 	int size, ret = 0;
73 	u32 off;
74 
75 	while (1) {
76 		bool has_tx_ulp;
77 
78 		sge = sk_msg_elem(msg, msg->sg.start);
79 		size = (apply && apply_bytes < sge->length) ?
80 			apply_bytes : sge->length;
81 		off  = sge->offset;
82 		page = sg_page(sge);
83 
84 		tcp_rate_check_app_limited(sk);
85 retry:
86 		has_tx_ulp = tls_sw_has_ctx_tx(sk);
87 		if (has_tx_ulp) {
88 			flags |= MSG_SENDPAGE_NOPOLICY;
89 			ret = kernel_sendpage_locked(sk,
90 						     page, off, size, flags);
91 		} else {
92 			ret = do_tcp_sendpages(sk, page, off, size, flags);
93 		}
94 
95 		if (ret <= 0)
96 			return ret;
97 		if (apply)
98 			apply_bytes -= ret;
99 		msg->sg.size -= ret;
100 		sge->offset += ret;
101 		sge->length -= ret;
102 		if (uncharge)
103 			sk_mem_uncharge(sk, ret);
104 		if (ret != size) {
105 			size -= ret;
106 			off  += ret;
107 			goto retry;
108 		}
109 		if (!sge->length) {
110 			put_page(page);
111 			sk_msg_iter_next(msg, start);
112 			sg_init_table(sge, 1);
113 			if (msg->sg.start == msg->sg.end)
114 				break;
115 		}
116 		if (apply && !apply_bytes)
117 			break;
118 	}
119 
120 	return 0;
121 }
122 
123 static int tcp_bpf_push_locked(struct sock *sk, struct sk_msg *msg,
124 			       u32 apply_bytes, int flags, bool uncharge)
125 {
126 	int ret;
127 
128 	lock_sock(sk);
129 	ret = tcp_bpf_push(sk, msg, apply_bytes, flags, uncharge);
130 	release_sock(sk);
131 	return ret;
132 }
133 
134 int tcp_bpf_sendmsg_redir(struct sock *sk, struct sk_msg *msg,
135 			  u32 bytes, int flags)
136 {
137 	bool ingress = sk_msg_to_ingress(msg);
138 	struct sk_psock *psock = sk_psock_get(sk);
139 	int ret;
140 
141 	if (unlikely(!psock)) {
142 		sk_msg_free(sk, msg);
143 		return 0;
144 	}
145 	ret = ingress ? bpf_tcp_ingress(sk, psock, msg, bytes, flags) :
146 			tcp_bpf_push_locked(sk, msg, bytes, flags, false);
147 	sk_psock_put(sk, psock);
148 	return ret;
149 }
150 EXPORT_SYMBOL_GPL(tcp_bpf_sendmsg_redir);
151 
152 #ifdef CONFIG_BPF_SYSCALL
153 static bool tcp_bpf_stream_read(const struct sock *sk)
154 {
155 	struct sk_psock *psock;
156 	bool empty = true;
157 
158 	rcu_read_lock();
159 	psock = sk_psock(sk);
160 	if (likely(psock))
161 		empty = list_empty(&psock->ingress_msg);
162 	rcu_read_unlock();
163 	return !empty;
164 }
165 
166 static int tcp_bpf_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
167 		    int nonblock, int flags, int *addr_len)
168 {
169 	struct sk_psock *psock;
170 	int copied, ret;
171 
172 	if (unlikely(flags & MSG_ERRQUEUE))
173 		return inet_recv_error(sk, msg, len, addr_len);
174 
175 	psock = sk_psock_get(sk);
176 	if (unlikely(!psock))
177 		return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len);
178 	if (!skb_queue_empty(&sk->sk_receive_queue) &&
179 	    sk_psock_queue_empty(psock)) {
180 		sk_psock_put(sk, psock);
181 		return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len);
182 	}
183 	lock_sock(sk);
184 msg_bytes_ready:
185 	copied = sk_msg_recvmsg(sk, psock, msg, len, flags);
186 	if (!copied) {
187 		int data, err = 0;
188 		long timeo;
189 
190 		timeo = sock_rcvtimeo(sk, nonblock);
191 		data = sk_msg_wait_data(sk, psock, flags, timeo, &err);
192 		if (data) {
193 			if (!sk_psock_queue_empty(psock))
194 				goto msg_bytes_ready;
195 			release_sock(sk);
196 			sk_psock_put(sk, psock);
197 			return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len);
198 		}
199 		if (err) {
200 			ret = err;
201 			goto out;
202 		}
203 		copied = -EAGAIN;
204 	}
205 	ret = copied;
206 out:
207 	release_sock(sk);
208 	sk_psock_put(sk, psock);
209 	return ret;
210 }
211 
212 static int tcp_bpf_send_verdict(struct sock *sk, struct sk_psock *psock,
213 				struct sk_msg *msg, int *copied, int flags)
214 {
215 	bool cork = false, enospc = sk_msg_full(msg);
216 	struct sock *sk_redir;
217 	u32 tosend, delta = 0;
218 	int ret;
219 
220 more_data:
221 	if (psock->eval == __SK_NONE) {
222 		/* Track delta in msg size to add/subtract it on SK_DROP from
223 		 * returned to user copied size. This ensures user doesn't
224 		 * get a positive return code with msg_cut_data and SK_DROP
225 		 * verdict.
226 		 */
227 		delta = msg->sg.size;
228 		psock->eval = sk_psock_msg_verdict(sk, psock, msg);
229 		delta -= msg->sg.size;
230 	}
231 
232 	if (msg->cork_bytes &&
233 	    msg->cork_bytes > msg->sg.size && !enospc) {
234 		psock->cork_bytes = msg->cork_bytes - msg->sg.size;
235 		if (!psock->cork) {
236 			psock->cork = kzalloc(sizeof(*psock->cork),
237 					      GFP_ATOMIC | __GFP_NOWARN);
238 			if (!psock->cork)
239 				return -ENOMEM;
240 		}
241 		memcpy(psock->cork, msg, sizeof(*msg));
242 		return 0;
243 	}
244 
245 	tosend = msg->sg.size;
246 	if (psock->apply_bytes && psock->apply_bytes < tosend)
247 		tosend = psock->apply_bytes;
248 
249 	switch (psock->eval) {
250 	case __SK_PASS:
251 		ret = tcp_bpf_push(sk, msg, tosend, flags, true);
252 		if (unlikely(ret)) {
253 			*copied -= sk_msg_free(sk, msg);
254 			break;
255 		}
256 		sk_msg_apply_bytes(psock, tosend);
257 		break;
258 	case __SK_REDIRECT:
259 		sk_redir = psock->sk_redir;
260 		sk_msg_apply_bytes(psock, tosend);
261 		if (psock->cork) {
262 			cork = true;
263 			psock->cork = NULL;
264 		}
265 		sk_msg_return(sk, msg, tosend);
266 		release_sock(sk);
267 		ret = tcp_bpf_sendmsg_redir(sk_redir, msg, tosend, flags);
268 		lock_sock(sk);
269 		if (unlikely(ret < 0)) {
270 			int free = sk_msg_free_nocharge(sk, msg);
271 
272 			if (!cork)
273 				*copied -= free;
274 		}
275 		if (cork) {
276 			sk_msg_free(sk, msg);
277 			kfree(msg);
278 			msg = NULL;
279 			ret = 0;
280 		}
281 		break;
282 	case __SK_DROP:
283 	default:
284 		sk_msg_free_partial(sk, msg, tosend);
285 		sk_msg_apply_bytes(psock, tosend);
286 		*copied -= (tosend + delta);
287 		return -EACCES;
288 	}
289 
290 	if (likely(!ret)) {
291 		if (!psock->apply_bytes) {
292 			psock->eval =  __SK_NONE;
293 			if (psock->sk_redir) {
294 				sock_put(psock->sk_redir);
295 				psock->sk_redir = NULL;
296 			}
297 		}
298 		if (msg &&
299 		    msg->sg.data[msg->sg.start].page_link &&
300 		    msg->sg.data[msg->sg.start].length)
301 			goto more_data;
302 	}
303 	return ret;
304 }
305 
306 static int tcp_bpf_sendmsg(struct sock *sk, struct msghdr *msg, size_t size)
307 {
308 	struct sk_msg tmp, *msg_tx = NULL;
309 	int copied = 0, err = 0;
310 	struct sk_psock *psock;
311 	long timeo;
312 	int flags;
313 
314 	/* Don't let internal do_tcp_sendpages() flags through */
315 	flags = (msg->msg_flags & ~MSG_SENDPAGE_DECRYPTED);
316 	flags |= MSG_NO_SHARED_FRAGS;
317 
318 	psock = sk_psock_get(sk);
319 	if (unlikely(!psock))
320 		return tcp_sendmsg(sk, msg, size);
321 
322 	lock_sock(sk);
323 	timeo = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT);
324 	while (msg_data_left(msg)) {
325 		bool enospc = false;
326 		u32 copy, osize;
327 
328 		if (sk->sk_err) {
329 			err = -sk->sk_err;
330 			goto out_err;
331 		}
332 
333 		copy = msg_data_left(msg);
334 		if (!sk_stream_memory_free(sk))
335 			goto wait_for_sndbuf;
336 		if (psock->cork) {
337 			msg_tx = psock->cork;
338 		} else {
339 			msg_tx = &tmp;
340 			sk_msg_init(msg_tx);
341 		}
342 
343 		osize = msg_tx->sg.size;
344 		err = sk_msg_alloc(sk, msg_tx, msg_tx->sg.size + copy, msg_tx->sg.end - 1);
345 		if (err) {
346 			if (err != -ENOSPC)
347 				goto wait_for_memory;
348 			enospc = true;
349 			copy = msg_tx->sg.size - osize;
350 		}
351 
352 		err = sk_msg_memcopy_from_iter(sk, &msg->msg_iter, msg_tx,
353 					       copy);
354 		if (err < 0) {
355 			sk_msg_trim(sk, msg_tx, osize);
356 			goto out_err;
357 		}
358 
359 		copied += copy;
360 		if (psock->cork_bytes) {
361 			if (size > psock->cork_bytes)
362 				psock->cork_bytes = 0;
363 			else
364 				psock->cork_bytes -= size;
365 			if (psock->cork_bytes && !enospc)
366 				goto out_err;
367 			/* All cork bytes are accounted, rerun the prog. */
368 			psock->eval = __SK_NONE;
369 			psock->cork_bytes = 0;
370 		}
371 
372 		err = tcp_bpf_send_verdict(sk, psock, msg_tx, &copied, flags);
373 		if (unlikely(err < 0))
374 			goto out_err;
375 		continue;
376 wait_for_sndbuf:
377 		set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
378 wait_for_memory:
379 		err = sk_stream_wait_memory(sk, &timeo);
380 		if (err) {
381 			if (msg_tx && msg_tx != psock->cork)
382 				sk_msg_free(sk, msg_tx);
383 			goto out_err;
384 		}
385 	}
386 out_err:
387 	if (err < 0)
388 		err = sk_stream_error(sk, msg->msg_flags, err);
389 	release_sock(sk);
390 	sk_psock_put(sk, psock);
391 	return copied ? copied : err;
392 }
393 
394 static int tcp_bpf_sendpage(struct sock *sk, struct page *page, int offset,
395 			    size_t size, int flags)
396 {
397 	struct sk_msg tmp, *msg = NULL;
398 	int err = 0, copied = 0;
399 	struct sk_psock *psock;
400 	bool enospc = false;
401 
402 	psock = sk_psock_get(sk);
403 	if (unlikely(!psock))
404 		return tcp_sendpage(sk, page, offset, size, flags);
405 
406 	lock_sock(sk);
407 	if (psock->cork) {
408 		msg = psock->cork;
409 	} else {
410 		msg = &tmp;
411 		sk_msg_init(msg);
412 	}
413 
414 	/* Catch case where ring is full and sendpage is stalled. */
415 	if (unlikely(sk_msg_full(msg)))
416 		goto out_err;
417 
418 	sk_msg_page_add(msg, page, size, offset);
419 	sk_mem_charge(sk, size);
420 	copied = size;
421 	if (sk_msg_full(msg))
422 		enospc = true;
423 	if (psock->cork_bytes) {
424 		if (size > psock->cork_bytes)
425 			psock->cork_bytes = 0;
426 		else
427 			psock->cork_bytes -= size;
428 		if (psock->cork_bytes && !enospc)
429 			goto out_err;
430 		/* All cork bytes are accounted, rerun the prog. */
431 		psock->eval = __SK_NONE;
432 		psock->cork_bytes = 0;
433 	}
434 
435 	err = tcp_bpf_send_verdict(sk, psock, msg, &copied, flags);
436 out_err:
437 	release_sock(sk);
438 	sk_psock_put(sk, psock);
439 	return copied ? copied : err;
440 }
441 
442 enum {
443 	TCP_BPF_IPV4,
444 	TCP_BPF_IPV6,
445 	TCP_BPF_NUM_PROTS,
446 };
447 
448 enum {
449 	TCP_BPF_BASE,
450 	TCP_BPF_TX,
451 	TCP_BPF_NUM_CFGS,
452 };
453 
454 static struct proto *tcpv6_prot_saved __read_mostly;
455 static DEFINE_SPINLOCK(tcpv6_prot_lock);
456 static struct proto tcp_bpf_prots[TCP_BPF_NUM_PROTS][TCP_BPF_NUM_CFGS];
457 
458 static void tcp_bpf_rebuild_protos(struct proto prot[TCP_BPF_NUM_CFGS],
459 				   struct proto *base)
460 {
461 	prot[TCP_BPF_BASE]			= *base;
462 	prot[TCP_BPF_BASE].unhash		= sock_map_unhash;
463 	prot[TCP_BPF_BASE].close		= sock_map_close;
464 	prot[TCP_BPF_BASE].recvmsg		= tcp_bpf_recvmsg;
465 	prot[TCP_BPF_BASE].stream_memory_read	= tcp_bpf_stream_read;
466 
467 	prot[TCP_BPF_TX]			= prot[TCP_BPF_BASE];
468 	prot[TCP_BPF_TX].sendmsg		= tcp_bpf_sendmsg;
469 	prot[TCP_BPF_TX].sendpage		= tcp_bpf_sendpage;
470 }
471 
472 static void tcp_bpf_check_v6_needs_rebuild(struct proto *ops)
473 {
474 	if (unlikely(ops != smp_load_acquire(&tcpv6_prot_saved))) {
475 		spin_lock_bh(&tcpv6_prot_lock);
476 		if (likely(ops != tcpv6_prot_saved)) {
477 			tcp_bpf_rebuild_protos(tcp_bpf_prots[TCP_BPF_IPV6], ops);
478 			smp_store_release(&tcpv6_prot_saved, ops);
479 		}
480 		spin_unlock_bh(&tcpv6_prot_lock);
481 	}
482 }
483 
484 static int __init tcp_bpf_v4_build_proto(void)
485 {
486 	tcp_bpf_rebuild_protos(tcp_bpf_prots[TCP_BPF_IPV4], &tcp_prot);
487 	return 0;
488 }
489 core_initcall(tcp_bpf_v4_build_proto);
490 
491 static int tcp_bpf_assert_proto_ops(struct proto *ops)
492 {
493 	/* In order to avoid retpoline, we make assumptions when we call
494 	 * into ops if e.g. a psock is not present. Make sure they are
495 	 * indeed valid assumptions.
496 	 */
497 	return ops->recvmsg  == tcp_recvmsg &&
498 	       ops->sendmsg  == tcp_sendmsg &&
499 	       ops->sendpage == tcp_sendpage ? 0 : -ENOTSUPP;
500 }
501 
502 int tcp_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore)
503 {
504 	int family = sk->sk_family == AF_INET6 ? TCP_BPF_IPV6 : TCP_BPF_IPV4;
505 	int config = psock->progs.msg_parser   ? TCP_BPF_TX   : TCP_BPF_BASE;
506 
507 	if (restore) {
508 		if (inet_csk_has_ulp(sk)) {
509 			/* TLS does not have an unhash proto in SW cases,
510 			 * but we need to ensure we stop using the sock_map
511 			 * unhash routine because the associated psock is being
512 			 * removed. So use the original unhash handler.
513 			 */
514 			WRITE_ONCE(sk->sk_prot->unhash, psock->saved_unhash);
515 			tcp_update_ulp(sk, psock->sk_proto, psock->saved_write_space);
516 		} else {
517 			sk->sk_write_space = psock->saved_write_space;
518 			/* Pairs with lockless read in sk_clone_lock() */
519 			WRITE_ONCE(sk->sk_prot, psock->sk_proto);
520 		}
521 		return 0;
522 	}
523 
524 	if (inet_csk_has_ulp(sk))
525 		return -EINVAL;
526 
527 	if (sk->sk_family == AF_INET6) {
528 		if (tcp_bpf_assert_proto_ops(psock->sk_proto))
529 			return -EINVAL;
530 
531 		tcp_bpf_check_v6_needs_rebuild(psock->sk_proto);
532 	}
533 
534 	/* Pairs with lockless read in sk_clone_lock() */
535 	WRITE_ONCE(sk->sk_prot, &tcp_bpf_prots[family][config]);
536 	return 0;
537 }
538 EXPORT_SYMBOL_GPL(tcp_bpf_update_proto);
539 
540 /* If a child got cloned from a listening socket that had tcp_bpf
541  * protocol callbacks installed, we need to restore the callbacks to
542  * the default ones because the child does not inherit the psock state
543  * that tcp_bpf callbacks expect.
544  */
545 void tcp_bpf_clone(const struct sock *sk, struct sock *newsk)
546 {
547 	int family = sk->sk_family == AF_INET6 ? TCP_BPF_IPV6 : TCP_BPF_IPV4;
548 	struct proto *prot = newsk->sk_prot;
549 
550 	if (prot == &tcp_bpf_prots[family][TCP_BPF_BASE])
551 		newsk->sk_prot = sk->sk_prot_creator;
552 }
553 #endif /* CONFIG_BPF_SYSCALL */
554