1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * INET		An implementation of the TCP/IP protocol suite for the LINUX
4  *		operating system.  INET is implemented using the  BSD Socket
5  *		interface as the means of communication with the user level.
6  *
7  *		Support for INET connection oriented protocols.
8  *
9  * Authors:	See the TCP sources
10  */
11 
12 #include <linux/module.h>
13 #include <linux/jhash.h>
14 
15 #include <net/inet_connection_sock.h>
16 #include <net/inet_hashtables.h>
17 #include <net/inet_timewait_sock.h>
18 #include <net/ip.h>
19 #include <net/route.h>
20 #include <net/tcp_states.h>
21 #include <net/xfrm.h>
22 #include <net/tcp.h>
23 #include <net/sock_reuseport.h>
24 #include <net/addrconf.h>
25 
26 #if IS_ENABLED(CONFIG_IPV6)
27 /* match_sk*_wildcard == true:  IPV6_ADDR_ANY equals to any IPv6 addresses
28  *				if IPv6 only, and any IPv4 addresses
29  *				if not IPv6 only
30  * match_sk*_wildcard == false: addresses must be exactly the same, i.e.
31  *				IPV6_ADDR_ANY only equals to IPV6_ADDR_ANY,
32  *				and 0.0.0.0 equals to 0.0.0.0 only
33  */
34 static bool ipv6_rcv_saddr_equal(const struct in6_addr *sk1_rcv_saddr6,
35 				 const struct in6_addr *sk2_rcv_saddr6,
36 				 __be32 sk1_rcv_saddr, __be32 sk2_rcv_saddr,
37 				 bool sk1_ipv6only, bool sk2_ipv6only,
38 				 bool match_sk1_wildcard,
39 				 bool match_sk2_wildcard)
40 {
41 	int addr_type = ipv6_addr_type(sk1_rcv_saddr6);
42 	int addr_type2 = sk2_rcv_saddr6 ? ipv6_addr_type(sk2_rcv_saddr6) : IPV6_ADDR_MAPPED;
43 
44 	/* if both are mapped, treat as IPv4 */
45 	if (addr_type == IPV6_ADDR_MAPPED && addr_type2 == IPV6_ADDR_MAPPED) {
46 		if (!sk2_ipv6only) {
47 			if (sk1_rcv_saddr == sk2_rcv_saddr)
48 				return true;
49 			return (match_sk1_wildcard && !sk1_rcv_saddr) ||
50 				(match_sk2_wildcard && !sk2_rcv_saddr);
51 		}
52 		return false;
53 	}
54 
55 	if (addr_type == IPV6_ADDR_ANY && addr_type2 == IPV6_ADDR_ANY)
56 		return true;
57 
58 	if (addr_type2 == IPV6_ADDR_ANY && match_sk2_wildcard &&
59 	    !(sk2_ipv6only && addr_type == IPV6_ADDR_MAPPED))
60 		return true;
61 
62 	if (addr_type == IPV6_ADDR_ANY && match_sk1_wildcard &&
63 	    !(sk1_ipv6only && addr_type2 == IPV6_ADDR_MAPPED))
64 		return true;
65 
66 	if (sk2_rcv_saddr6 &&
67 	    ipv6_addr_equal(sk1_rcv_saddr6, sk2_rcv_saddr6))
68 		return true;
69 
70 	return false;
71 }
72 #endif
73 
74 /* match_sk*_wildcard == true:  0.0.0.0 equals to any IPv4 addresses
75  * match_sk*_wildcard == false: addresses must be exactly the same, i.e.
76  *				0.0.0.0 only equals to 0.0.0.0
77  */
78 static bool ipv4_rcv_saddr_equal(__be32 sk1_rcv_saddr, __be32 sk2_rcv_saddr,
79 				 bool sk2_ipv6only, bool match_sk1_wildcard,
80 				 bool match_sk2_wildcard)
81 {
82 	if (!sk2_ipv6only) {
83 		if (sk1_rcv_saddr == sk2_rcv_saddr)
84 			return true;
85 		return (match_sk1_wildcard && !sk1_rcv_saddr) ||
86 			(match_sk2_wildcard && !sk2_rcv_saddr);
87 	}
88 	return false;
89 }
90 
91 bool inet_rcv_saddr_equal(const struct sock *sk, const struct sock *sk2,
92 			  bool match_wildcard)
93 {
94 #if IS_ENABLED(CONFIG_IPV6)
95 	if (sk->sk_family == AF_INET6)
96 		return ipv6_rcv_saddr_equal(&sk->sk_v6_rcv_saddr,
97 					    inet6_rcv_saddr(sk2),
98 					    sk->sk_rcv_saddr,
99 					    sk2->sk_rcv_saddr,
100 					    ipv6_only_sock(sk),
101 					    ipv6_only_sock(sk2),
102 					    match_wildcard,
103 					    match_wildcard);
104 #endif
105 	return ipv4_rcv_saddr_equal(sk->sk_rcv_saddr, sk2->sk_rcv_saddr,
106 				    ipv6_only_sock(sk2), match_wildcard,
107 				    match_wildcard);
108 }
109 EXPORT_SYMBOL(inet_rcv_saddr_equal);
110 
111 bool inet_rcv_saddr_any(const struct sock *sk)
112 {
113 #if IS_ENABLED(CONFIG_IPV6)
114 	if (sk->sk_family == AF_INET6)
115 		return ipv6_addr_any(&sk->sk_v6_rcv_saddr);
116 #endif
117 	return !sk->sk_rcv_saddr;
118 }
119 
120 void inet_get_local_port_range(struct net *net, int *low, int *high)
121 {
122 	unsigned int seq;
123 
124 	do {
125 		seq = read_seqbegin(&net->ipv4.ip_local_ports.lock);
126 
127 		*low = net->ipv4.ip_local_ports.range[0];
128 		*high = net->ipv4.ip_local_ports.range[1];
129 	} while (read_seqretry(&net->ipv4.ip_local_ports.lock, seq));
130 }
131 EXPORT_SYMBOL(inet_get_local_port_range);
132 
133 static bool inet_use_bhash2_on_bind(const struct sock *sk)
134 {
135 #if IS_ENABLED(CONFIG_IPV6)
136 	if (sk->sk_family == AF_INET6) {
137 		int addr_type = ipv6_addr_type(&sk->sk_v6_rcv_saddr);
138 
139 		return addr_type != IPV6_ADDR_ANY &&
140 			addr_type != IPV6_ADDR_MAPPED;
141 	}
142 #endif
143 	return sk->sk_rcv_saddr != htonl(INADDR_ANY);
144 }
145 
146 static bool inet_bind_conflict(const struct sock *sk, struct sock *sk2,
147 			       kuid_t sk_uid, bool relax,
148 			       bool reuseport_cb_ok, bool reuseport_ok)
149 {
150 	int bound_dev_if2;
151 
152 	if (sk == sk2)
153 		return false;
154 
155 	bound_dev_if2 = READ_ONCE(sk2->sk_bound_dev_if);
156 
157 	if (!sk->sk_bound_dev_if || !bound_dev_if2 ||
158 	    sk->sk_bound_dev_if == bound_dev_if2) {
159 		if (sk->sk_reuse && sk2->sk_reuse &&
160 		    sk2->sk_state != TCP_LISTEN) {
161 			if (!relax || (!reuseport_ok && sk->sk_reuseport &&
162 				       sk2->sk_reuseport && reuseport_cb_ok &&
163 				       (sk2->sk_state == TCP_TIME_WAIT ||
164 					uid_eq(sk_uid, sock_i_uid(sk2)))))
165 				return true;
166 		} else if (!reuseport_ok || !sk->sk_reuseport ||
167 			   !sk2->sk_reuseport || !reuseport_cb_ok ||
168 			   (sk2->sk_state != TCP_TIME_WAIT &&
169 			    !uid_eq(sk_uid, sock_i_uid(sk2)))) {
170 			return true;
171 		}
172 	}
173 	return false;
174 }
175 
176 static bool inet_bhash2_conflict(const struct sock *sk,
177 				 const struct inet_bind2_bucket *tb2,
178 				 kuid_t sk_uid,
179 				 bool relax, bool reuseport_cb_ok,
180 				 bool reuseport_ok)
181 {
182 	struct sock *sk2;
183 
184 	sk_for_each_bound_bhash2(sk2, &tb2->owners) {
185 		if (sk->sk_family == AF_INET && ipv6_only_sock(sk2))
186 			continue;
187 
188 		if (inet_bind_conflict(sk, sk2, sk_uid, relax,
189 				       reuseport_cb_ok, reuseport_ok))
190 			return true;
191 	}
192 	return false;
193 }
194 
195 /* This should be called only when the tb and tb2 hashbuckets' locks are held */
196 static int inet_csk_bind_conflict(const struct sock *sk,
197 				  const struct inet_bind_bucket *tb,
198 				  const struct inet_bind2_bucket *tb2, /* may be null */
199 				  bool relax, bool reuseport_ok)
200 {
201 	bool reuseport_cb_ok;
202 	struct sock_reuseport *reuseport_cb;
203 	kuid_t uid = sock_i_uid((struct sock *)sk);
204 
205 	rcu_read_lock();
206 	reuseport_cb = rcu_dereference(sk->sk_reuseport_cb);
207 	/* paired with WRITE_ONCE() in __reuseport_(add|detach)_closed_sock */
208 	reuseport_cb_ok = !reuseport_cb || READ_ONCE(reuseport_cb->num_closed_socks);
209 	rcu_read_unlock();
210 
211 	/*
212 	 * Unlike other sk lookup places we do not check
213 	 * for sk_net here, since _all_ the socks listed
214 	 * in tb->owners and tb2->owners list belong
215 	 * to the same net - the one this bucket belongs to.
216 	 */
217 
218 	if (!inet_use_bhash2_on_bind(sk)) {
219 		struct sock *sk2;
220 
221 		sk_for_each_bound(sk2, &tb->owners)
222 			if (inet_bind_conflict(sk, sk2, uid, relax,
223 					       reuseport_cb_ok, reuseport_ok) &&
224 			    inet_rcv_saddr_equal(sk, sk2, true))
225 				return true;
226 
227 		return false;
228 	}
229 
230 	/* Conflicts with an existing IPV6_ADDR_ANY (if ipv6) or INADDR_ANY (if
231 	 * ipv4) should have been checked already. We need to do these two
232 	 * checks separately because their spinlocks have to be acquired/released
233 	 * independently of each other, to prevent possible deadlocks
234 	 */
235 	return tb2 && inet_bhash2_conflict(sk, tb2, uid, relax, reuseport_cb_ok,
236 					   reuseport_ok);
237 }
238 
239 /* Determine if there is a bind conflict with an existing IPV6_ADDR_ANY (if ipv6) or
240  * INADDR_ANY (if ipv4) socket.
241  *
242  * Caller must hold bhash hashbucket lock with local bh disabled, to protect
243  * against concurrent binds on the port for addr any
244  */
245 static bool inet_bhash2_addr_any_conflict(const struct sock *sk, int port, int l3mdev,
246 					  bool relax, bool reuseport_ok)
247 {
248 	kuid_t uid = sock_i_uid((struct sock *)sk);
249 	const struct net *net = sock_net(sk);
250 	struct sock_reuseport *reuseport_cb;
251 	struct inet_bind_hashbucket *head2;
252 	struct inet_bind2_bucket *tb2;
253 	bool reuseport_cb_ok;
254 
255 	rcu_read_lock();
256 	reuseport_cb = rcu_dereference(sk->sk_reuseport_cb);
257 	/* paired with WRITE_ONCE() in __reuseport_(add|detach)_closed_sock */
258 	reuseport_cb_ok = !reuseport_cb || READ_ONCE(reuseport_cb->num_closed_socks);
259 	rcu_read_unlock();
260 
261 	head2 = inet_bhash2_addr_any_hashbucket(sk, net, port);
262 
263 	spin_lock(&head2->lock);
264 
265 	inet_bind_bucket_for_each(tb2, &head2->chain)
266 		if (inet_bind2_bucket_match_addr_any(tb2, net, port, l3mdev, sk))
267 			break;
268 
269 	if (tb2 && inet_bhash2_conflict(sk, tb2, uid, relax, reuseport_cb_ok,
270 					reuseport_ok)) {
271 		spin_unlock(&head2->lock);
272 		return true;
273 	}
274 
275 	spin_unlock(&head2->lock);
276 	return false;
277 }
278 
279 /*
280  * Find an open port number for the socket.  Returns with the
281  * inet_bind_hashbucket locks held if successful.
282  */
283 static struct inet_bind_hashbucket *
284 inet_csk_find_open_port(const struct sock *sk, struct inet_bind_bucket **tb_ret,
285 			struct inet_bind2_bucket **tb2_ret,
286 			struct inet_bind_hashbucket **head2_ret, int *port_ret)
287 {
288 	struct inet_hashinfo *hinfo = tcp_or_dccp_get_hashinfo(sk);
289 	int i, low, high, attempt_half, port, l3mdev;
290 	struct inet_bind_hashbucket *head, *head2;
291 	struct net *net = sock_net(sk);
292 	struct inet_bind2_bucket *tb2;
293 	struct inet_bind_bucket *tb;
294 	u32 remaining, offset;
295 	bool relax = false;
296 
297 	l3mdev = inet_sk_bound_l3mdev(sk);
298 ports_exhausted:
299 	attempt_half = (sk->sk_reuse == SK_CAN_REUSE) ? 1 : 0;
300 other_half_scan:
301 	inet_get_local_port_range(net, &low, &high);
302 	high++; /* [32768, 60999] -> [32768, 61000[ */
303 	if (high - low < 4)
304 		attempt_half = 0;
305 	if (attempt_half) {
306 		int half = low + (((high - low) >> 2) << 1);
307 
308 		if (attempt_half == 1)
309 			high = half;
310 		else
311 			low = half;
312 	}
313 	remaining = high - low;
314 	if (likely(remaining > 1))
315 		remaining &= ~1U;
316 
317 	offset = get_random_u32_below(remaining);
318 	/* __inet_hash_connect() favors ports having @low parity
319 	 * We do the opposite to not pollute connect() users.
320 	 */
321 	offset |= 1U;
322 
323 other_parity_scan:
324 	port = low + offset;
325 	for (i = 0; i < remaining; i += 2, port += 2) {
326 		if (unlikely(port >= high))
327 			port -= remaining;
328 		if (inet_is_local_reserved_port(net, port))
329 			continue;
330 		head = &hinfo->bhash[inet_bhashfn(net, port,
331 						  hinfo->bhash_size)];
332 		spin_lock_bh(&head->lock);
333 		if (inet_use_bhash2_on_bind(sk)) {
334 			if (inet_bhash2_addr_any_conflict(sk, port, l3mdev, relax, false))
335 				goto next_port;
336 		}
337 
338 		head2 = inet_bhashfn_portaddr(hinfo, sk, net, port);
339 		spin_lock(&head2->lock);
340 		tb2 = inet_bind2_bucket_find(head2, net, port, l3mdev, sk);
341 		inet_bind_bucket_for_each(tb, &head->chain)
342 			if (inet_bind_bucket_match(tb, net, port, l3mdev)) {
343 				if (!inet_csk_bind_conflict(sk, tb, tb2,
344 							    relax, false))
345 					goto success;
346 				spin_unlock(&head2->lock);
347 				goto next_port;
348 			}
349 		tb = NULL;
350 		goto success;
351 next_port:
352 		spin_unlock_bh(&head->lock);
353 		cond_resched();
354 	}
355 
356 	offset--;
357 	if (!(offset & 1))
358 		goto other_parity_scan;
359 
360 	if (attempt_half == 1) {
361 		/* OK we now try the upper half of the range */
362 		attempt_half = 2;
363 		goto other_half_scan;
364 	}
365 
366 	if (READ_ONCE(net->ipv4.sysctl_ip_autobind_reuse) && !relax) {
367 		/* We still have a chance to connect to different destinations */
368 		relax = true;
369 		goto ports_exhausted;
370 	}
371 	return NULL;
372 success:
373 	*port_ret = port;
374 	*tb_ret = tb;
375 	*tb2_ret = tb2;
376 	*head2_ret = head2;
377 	return head;
378 }
379 
380 static inline int sk_reuseport_match(struct inet_bind_bucket *tb,
381 				     struct sock *sk)
382 {
383 	kuid_t uid = sock_i_uid(sk);
384 
385 	if (tb->fastreuseport <= 0)
386 		return 0;
387 	if (!sk->sk_reuseport)
388 		return 0;
389 	if (rcu_access_pointer(sk->sk_reuseport_cb))
390 		return 0;
391 	if (!uid_eq(tb->fastuid, uid))
392 		return 0;
393 	/* We only need to check the rcv_saddr if this tb was once marked
394 	 * without fastreuseport and then was reset, as we can only know that
395 	 * the fast_*rcv_saddr doesn't have any conflicts with the socks on the
396 	 * owners list.
397 	 */
398 	if (tb->fastreuseport == FASTREUSEPORT_ANY)
399 		return 1;
400 #if IS_ENABLED(CONFIG_IPV6)
401 	if (tb->fast_sk_family == AF_INET6)
402 		return ipv6_rcv_saddr_equal(&tb->fast_v6_rcv_saddr,
403 					    inet6_rcv_saddr(sk),
404 					    tb->fast_rcv_saddr,
405 					    sk->sk_rcv_saddr,
406 					    tb->fast_ipv6_only,
407 					    ipv6_only_sock(sk), true, false);
408 #endif
409 	return ipv4_rcv_saddr_equal(tb->fast_rcv_saddr, sk->sk_rcv_saddr,
410 				    ipv6_only_sock(sk), true, false);
411 }
412 
413 void inet_csk_update_fastreuse(struct inet_bind_bucket *tb,
414 			       struct sock *sk)
415 {
416 	kuid_t uid = sock_i_uid(sk);
417 	bool reuse = sk->sk_reuse && sk->sk_state != TCP_LISTEN;
418 
419 	if (hlist_empty(&tb->owners)) {
420 		tb->fastreuse = reuse;
421 		if (sk->sk_reuseport) {
422 			tb->fastreuseport = FASTREUSEPORT_ANY;
423 			tb->fastuid = uid;
424 			tb->fast_rcv_saddr = sk->sk_rcv_saddr;
425 			tb->fast_ipv6_only = ipv6_only_sock(sk);
426 			tb->fast_sk_family = sk->sk_family;
427 #if IS_ENABLED(CONFIG_IPV6)
428 			tb->fast_v6_rcv_saddr = sk->sk_v6_rcv_saddr;
429 #endif
430 		} else {
431 			tb->fastreuseport = 0;
432 		}
433 	} else {
434 		if (!reuse)
435 			tb->fastreuse = 0;
436 		if (sk->sk_reuseport) {
437 			/* We didn't match or we don't have fastreuseport set on
438 			 * the tb, but we have sk_reuseport set on this socket
439 			 * and we know that there are no bind conflicts with
440 			 * this socket in this tb, so reset our tb's reuseport
441 			 * settings so that any subsequent sockets that match
442 			 * our current socket will be put on the fast path.
443 			 *
444 			 * If we reset we need to set FASTREUSEPORT_STRICT so we
445 			 * do extra checking for all subsequent sk_reuseport
446 			 * socks.
447 			 */
448 			if (!sk_reuseport_match(tb, sk)) {
449 				tb->fastreuseport = FASTREUSEPORT_STRICT;
450 				tb->fastuid = uid;
451 				tb->fast_rcv_saddr = sk->sk_rcv_saddr;
452 				tb->fast_ipv6_only = ipv6_only_sock(sk);
453 				tb->fast_sk_family = sk->sk_family;
454 #if IS_ENABLED(CONFIG_IPV6)
455 				tb->fast_v6_rcv_saddr = sk->sk_v6_rcv_saddr;
456 #endif
457 			}
458 		} else {
459 			tb->fastreuseport = 0;
460 		}
461 	}
462 }
463 
464 /* Obtain a reference to a local port for the given sock,
465  * if snum is zero it means select any available local port.
466  * We try to allocate an odd port (and leave even ports for connect())
467  */
468 int inet_csk_get_port(struct sock *sk, unsigned short snum)
469 {
470 	struct inet_hashinfo *hinfo = tcp_or_dccp_get_hashinfo(sk);
471 	bool reuse = sk->sk_reuse && sk->sk_state != TCP_LISTEN;
472 	bool found_port = false, check_bind_conflict = true;
473 	bool bhash_created = false, bhash2_created = false;
474 	int ret = -EADDRINUSE, port = snum, l3mdev;
475 	struct inet_bind_hashbucket *head, *head2;
476 	struct inet_bind2_bucket *tb2 = NULL;
477 	struct inet_bind_bucket *tb = NULL;
478 	bool head2_lock_acquired = false;
479 	struct net *net = sock_net(sk);
480 
481 	l3mdev = inet_sk_bound_l3mdev(sk);
482 
483 	if (!port) {
484 		head = inet_csk_find_open_port(sk, &tb, &tb2, &head2, &port);
485 		if (!head)
486 			return ret;
487 
488 		head2_lock_acquired = true;
489 
490 		if (tb && tb2)
491 			goto success;
492 		found_port = true;
493 	} else {
494 		head = &hinfo->bhash[inet_bhashfn(net, port,
495 						  hinfo->bhash_size)];
496 		spin_lock_bh(&head->lock);
497 		inet_bind_bucket_for_each(tb, &head->chain)
498 			if (inet_bind_bucket_match(tb, net, port, l3mdev))
499 				break;
500 	}
501 
502 	if (!tb) {
503 		tb = inet_bind_bucket_create(hinfo->bind_bucket_cachep, net,
504 					     head, port, l3mdev);
505 		if (!tb)
506 			goto fail_unlock;
507 		bhash_created = true;
508 	}
509 
510 	if (!found_port) {
511 		if (!hlist_empty(&tb->owners)) {
512 			if (sk->sk_reuse == SK_FORCE_REUSE ||
513 			    (tb->fastreuse > 0 && reuse) ||
514 			    sk_reuseport_match(tb, sk))
515 				check_bind_conflict = false;
516 		}
517 
518 		if (check_bind_conflict && inet_use_bhash2_on_bind(sk)) {
519 			if (inet_bhash2_addr_any_conflict(sk, port, l3mdev, true, true))
520 				goto fail_unlock;
521 		}
522 
523 		head2 = inet_bhashfn_portaddr(hinfo, sk, net, port);
524 		spin_lock(&head2->lock);
525 		head2_lock_acquired = true;
526 		tb2 = inet_bind2_bucket_find(head2, net, port, l3mdev, sk);
527 	}
528 
529 	if (!tb2) {
530 		tb2 = inet_bind2_bucket_create(hinfo->bind2_bucket_cachep,
531 					       net, head2, port, l3mdev, sk);
532 		if (!tb2)
533 			goto fail_unlock;
534 		bhash2_created = true;
535 	}
536 
537 	if (!found_port && check_bind_conflict) {
538 		if (inet_csk_bind_conflict(sk, tb, tb2, true, true))
539 			goto fail_unlock;
540 	}
541 
542 success:
543 	inet_csk_update_fastreuse(tb, sk);
544 
545 	if (!inet_csk(sk)->icsk_bind_hash)
546 		inet_bind_hash(sk, tb, tb2, port);
547 	WARN_ON(inet_csk(sk)->icsk_bind_hash != tb);
548 	WARN_ON(inet_csk(sk)->icsk_bind2_hash != tb2);
549 	ret = 0;
550 
551 fail_unlock:
552 	if (ret) {
553 		if (bhash_created)
554 			inet_bind_bucket_destroy(hinfo->bind_bucket_cachep, tb);
555 		if (bhash2_created)
556 			inet_bind2_bucket_destroy(hinfo->bind2_bucket_cachep,
557 						  tb2);
558 	}
559 	if (head2_lock_acquired)
560 		spin_unlock(&head2->lock);
561 	spin_unlock_bh(&head->lock);
562 	return ret;
563 }
564 EXPORT_SYMBOL_GPL(inet_csk_get_port);
565 
566 /*
567  * Wait for an incoming connection, avoid race conditions. This must be called
568  * with the socket locked.
569  */
570 static int inet_csk_wait_for_connect(struct sock *sk, long timeo)
571 {
572 	struct inet_connection_sock *icsk = inet_csk(sk);
573 	DEFINE_WAIT(wait);
574 	int err;
575 
576 	/*
577 	 * True wake-one mechanism for incoming connections: only
578 	 * one process gets woken up, not the 'whole herd'.
579 	 * Since we do not 'race & poll' for established sockets
580 	 * anymore, the common case will execute the loop only once.
581 	 *
582 	 * Subtle issue: "add_wait_queue_exclusive()" will be added
583 	 * after any current non-exclusive waiters, and we know that
584 	 * it will always _stay_ after any new non-exclusive waiters
585 	 * because all non-exclusive waiters are added at the
586 	 * beginning of the wait-queue. As such, it's ok to "drop"
587 	 * our exclusiveness temporarily when we get woken up without
588 	 * having to remove and re-insert us on the wait queue.
589 	 */
590 	for (;;) {
591 		prepare_to_wait_exclusive(sk_sleep(sk), &wait,
592 					  TASK_INTERRUPTIBLE);
593 		release_sock(sk);
594 		if (reqsk_queue_empty(&icsk->icsk_accept_queue))
595 			timeo = schedule_timeout(timeo);
596 		sched_annotate_sleep();
597 		lock_sock(sk);
598 		err = 0;
599 		if (!reqsk_queue_empty(&icsk->icsk_accept_queue))
600 			break;
601 		err = -EINVAL;
602 		if (sk->sk_state != TCP_LISTEN)
603 			break;
604 		err = sock_intr_errno(timeo);
605 		if (signal_pending(current))
606 			break;
607 		err = -EAGAIN;
608 		if (!timeo)
609 			break;
610 	}
611 	finish_wait(sk_sleep(sk), &wait);
612 	return err;
613 }
614 
615 /*
616  * This will accept the next outstanding connection.
617  */
618 struct sock *inet_csk_accept(struct sock *sk, int flags, int *err, bool kern)
619 {
620 	struct inet_connection_sock *icsk = inet_csk(sk);
621 	struct request_sock_queue *queue = &icsk->icsk_accept_queue;
622 	struct request_sock *req;
623 	struct sock *newsk;
624 	int error;
625 
626 	lock_sock(sk);
627 
628 	/* We need to make sure that this socket is listening,
629 	 * and that it has something pending.
630 	 */
631 	error = -EINVAL;
632 	if (sk->sk_state != TCP_LISTEN)
633 		goto out_err;
634 
635 	/* Find already established connection */
636 	if (reqsk_queue_empty(queue)) {
637 		long timeo = sock_rcvtimeo(sk, flags & O_NONBLOCK);
638 
639 		/* If this is a non blocking socket don't sleep */
640 		error = -EAGAIN;
641 		if (!timeo)
642 			goto out_err;
643 
644 		error = inet_csk_wait_for_connect(sk, timeo);
645 		if (error)
646 			goto out_err;
647 	}
648 	req = reqsk_queue_remove(queue, sk);
649 	newsk = req->sk;
650 
651 	if (sk->sk_protocol == IPPROTO_TCP &&
652 	    tcp_rsk(req)->tfo_listener) {
653 		spin_lock_bh(&queue->fastopenq.lock);
654 		if (tcp_rsk(req)->tfo_listener) {
655 			/* We are still waiting for the final ACK from 3WHS
656 			 * so can't free req now. Instead, we set req->sk to
657 			 * NULL to signify that the child socket is taken
658 			 * so reqsk_fastopen_remove() will free the req
659 			 * when 3WHS finishes (or is aborted).
660 			 */
661 			req->sk = NULL;
662 			req = NULL;
663 		}
664 		spin_unlock_bh(&queue->fastopenq.lock);
665 	}
666 
667 out:
668 	release_sock(sk);
669 	if (newsk && mem_cgroup_sockets_enabled) {
670 		int amt;
671 
672 		/* atomically get the memory usage, set and charge the
673 		 * newsk->sk_memcg.
674 		 */
675 		lock_sock(newsk);
676 
677 		/* The socket has not been accepted yet, no need to look at
678 		 * newsk->sk_wmem_queued.
679 		 */
680 		amt = sk_mem_pages(newsk->sk_forward_alloc +
681 				   atomic_read(&newsk->sk_rmem_alloc));
682 		mem_cgroup_sk_alloc(newsk);
683 		if (newsk->sk_memcg && amt)
684 			mem_cgroup_charge_skmem(newsk->sk_memcg, amt,
685 						GFP_KERNEL | __GFP_NOFAIL);
686 
687 		release_sock(newsk);
688 	}
689 	if (req)
690 		reqsk_put(req);
691 	return newsk;
692 out_err:
693 	newsk = NULL;
694 	req = NULL;
695 	*err = error;
696 	goto out;
697 }
698 EXPORT_SYMBOL(inet_csk_accept);
699 
700 /*
701  * Using different timers for retransmit, delayed acks and probes
702  * We may wish use just one timer maintaining a list of expire jiffies
703  * to optimize.
704  */
705 void inet_csk_init_xmit_timers(struct sock *sk,
706 			       void (*retransmit_handler)(struct timer_list *t),
707 			       void (*delack_handler)(struct timer_list *t),
708 			       void (*keepalive_handler)(struct timer_list *t))
709 {
710 	struct inet_connection_sock *icsk = inet_csk(sk);
711 
712 	timer_setup(&icsk->icsk_retransmit_timer, retransmit_handler, 0);
713 	timer_setup(&icsk->icsk_delack_timer, delack_handler, 0);
714 	timer_setup(&sk->sk_timer, keepalive_handler, 0);
715 	icsk->icsk_pending = icsk->icsk_ack.pending = 0;
716 }
717 EXPORT_SYMBOL(inet_csk_init_xmit_timers);
718 
719 void inet_csk_clear_xmit_timers(struct sock *sk)
720 {
721 	struct inet_connection_sock *icsk = inet_csk(sk);
722 
723 	icsk->icsk_pending = icsk->icsk_ack.pending = 0;
724 
725 	sk_stop_timer(sk, &icsk->icsk_retransmit_timer);
726 	sk_stop_timer(sk, &icsk->icsk_delack_timer);
727 	sk_stop_timer(sk, &sk->sk_timer);
728 }
729 EXPORT_SYMBOL(inet_csk_clear_xmit_timers);
730 
731 void inet_csk_delete_keepalive_timer(struct sock *sk)
732 {
733 	sk_stop_timer(sk, &sk->sk_timer);
734 }
735 EXPORT_SYMBOL(inet_csk_delete_keepalive_timer);
736 
737 void inet_csk_reset_keepalive_timer(struct sock *sk, unsigned long len)
738 {
739 	sk_reset_timer(sk, &sk->sk_timer, jiffies + len);
740 }
741 EXPORT_SYMBOL(inet_csk_reset_keepalive_timer);
742 
743 struct dst_entry *inet_csk_route_req(const struct sock *sk,
744 				     struct flowi4 *fl4,
745 				     const struct request_sock *req)
746 {
747 	const struct inet_request_sock *ireq = inet_rsk(req);
748 	struct net *net = read_pnet(&ireq->ireq_net);
749 	struct ip_options_rcu *opt;
750 	struct rtable *rt;
751 
752 	rcu_read_lock();
753 	opt = rcu_dereference(ireq->ireq_opt);
754 
755 	flowi4_init_output(fl4, ireq->ir_iif, ireq->ir_mark,
756 			   RT_CONN_FLAGS(sk), RT_SCOPE_UNIVERSE,
757 			   sk->sk_protocol, inet_sk_flowi_flags(sk),
758 			   (opt && opt->opt.srr) ? opt->opt.faddr : ireq->ir_rmt_addr,
759 			   ireq->ir_loc_addr, ireq->ir_rmt_port,
760 			   htons(ireq->ir_num), sk->sk_uid);
761 	security_req_classify_flow(req, flowi4_to_flowi_common(fl4));
762 	rt = ip_route_output_flow(net, fl4, sk);
763 	if (IS_ERR(rt))
764 		goto no_route;
765 	if (opt && opt->opt.is_strictroute && rt->rt_uses_gateway)
766 		goto route_err;
767 	rcu_read_unlock();
768 	return &rt->dst;
769 
770 route_err:
771 	ip_rt_put(rt);
772 no_route:
773 	rcu_read_unlock();
774 	__IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);
775 	return NULL;
776 }
777 EXPORT_SYMBOL_GPL(inet_csk_route_req);
778 
779 struct dst_entry *inet_csk_route_child_sock(const struct sock *sk,
780 					    struct sock *newsk,
781 					    const struct request_sock *req)
782 {
783 	const struct inet_request_sock *ireq = inet_rsk(req);
784 	struct net *net = read_pnet(&ireq->ireq_net);
785 	struct inet_sock *newinet = inet_sk(newsk);
786 	struct ip_options_rcu *opt;
787 	struct flowi4 *fl4;
788 	struct rtable *rt;
789 
790 	opt = rcu_dereference(ireq->ireq_opt);
791 	fl4 = &newinet->cork.fl.u.ip4;
792 
793 	flowi4_init_output(fl4, ireq->ir_iif, ireq->ir_mark,
794 			   RT_CONN_FLAGS(sk), RT_SCOPE_UNIVERSE,
795 			   sk->sk_protocol, inet_sk_flowi_flags(sk),
796 			   (opt && opt->opt.srr) ? opt->opt.faddr : ireq->ir_rmt_addr,
797 			   ireq->ir_loc_addr, ireq->ir_rmt_port,
798 			   htons(ireq->ir_num), sk->sk_uid);
799 	security_req_classify_flow(req, flowi4_to_flowi_common(fl4));
800 	rt = ip_route_output_flow(net, fl4, sk);
801 	if (IS_ERR(rt))
802 		goto no_route;
803 	if (opt && opt->opt.is_strictroute && rt->rt_uses_gateway)
804 		goto route_err;
805 	return &rt->dst;
806 
807 route_err:
808 	ip_rt_put(rt);
809 no_route:
810 	__IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);
811 	return NULL;
812 }
813 EXPORT_SYMBOL_GPL(inet_csk_route_child_sock);
814 
815 /* Decide when to expire the request and when to resend SYN-ACK */
816 static void syn_ack_recalc(struct request_sock *req,
817 			   const int max_syn_ack_retries,
818 			   const u8 rskq_defer_accept,
819 			   int *expire, int *resend)
820 {
821 	if (!rskq_defer_accept) {
822 		*expire = req->num_timeout >= max_syn_ack_retries;
823 		*resend = 1;
824 		return;
825 	}
826 	*expire = req->num_timeout >= max_syn_ack_retries &&
827 		  (!inet_rsk(req)->acked || req->num_timeout >= rskq_defer_accept);
828 	/* Do not resend while waiting for data after ACK,
829 	 * start to resend on end of deferring period to give
830 	 * last chance for data or ACK to create established socket.
831 	 */
832 	*resend = !inet_rsk(req)->acked ||
833 		  req->num_timeout >= rskq_defer_accept - 1;
834 }
835 
836 int inet_rtx_syn_ack(const struct sock *parent, struct request_sock *req)
837 {
838 	int err = req->rsk_ops->rtx_syn_ack(parent, req);
839 
840 	if (!err)
841 		req->num_retrans++;
842 	return err;
843 }
844 EXPORT_SYMBOL(inet_rtx_syn_ack);
845 
846 static struct request_sock *inet_reqsk_clone(struct request_sock *req,
847 					     struct sock *sk)
848 {
849 	struct sock *req_sk, *nreq_sk;
850 	struct request_sock *nreq;
851 
852 	nreq = kmem_cache_alloc(req->rsk_ops->slab, GFP_ATOMIC | __GFP_NOWARN);
853 	if (!nreq) {
854 		__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMIGRATEREQFAILURE);
855 
856 		/* paired with refcount_inc_not_zero() in reuseport_migrate_sock() */
857 		sock_put(sk);
858 		return NULL;
859 	}
860 
861 	req_sk = req_to_sk(req);
862 	nreq_sk = req_to_sk(nreq);
863 
864 	memcpy(nreq_sk, req_sk,
865 	       offsetof(struct sock, sk_dontcopy_begin));
866 	memcpy(&nreq_sk->sk_dontcopy_end, &req_sk->sk_dontcopy_end,
867 	       req->rsk_ops->obj_size - offsetof(struct sock, sk_dontcopy_end));
868 
869 	sk_node_init(&nreq_sk->sk_node);
870 	nreq_sk->sk_tx_queue_mapping = req_sk->sk_tx_queue_mapping;
871 #ifdef CONFIG_SOCK_RX_QUEUE_MAPPING
872 	nreq_sk->sk_rx_queue_mapping = req_sk->sk_rx_queue_mapping;
873 #endif
874 	nreq_sk->sk_incoming_cpu = req_sk->sk_incoming_cpu;
875 
876 	nreq->rsk_listener = sk;
877 
878 	/* We need not acquire fastopenq->lock
879 	 * because the child socket is locked in inet_csk_listen_stop().
880 	 */
881 	if (sk->sk_protocol == IPPROTO_TCP && tcp_rsk(nreq)->tfo_listener)
882 		rcu_assign_pointer(tcp_sk(nreq->sk)->fastopen_rsk, nreq);
883 
884 	return nreq;
885 }
886 
887 static void reqsk_queue_migrated(struct request_sock_queue *queue,
888 				 const struct request_sock *req)
889 {
890 	if (req->num_timeout == 0)
891 		atomic_inc(&queue->young);
892 	atomic_inc(&queue->qlen);
893 }
894 
895 static void reqsk_migrate_reset(struct request_sock *req)
896 {
897 	req->saved_syn = NULL;
898 #if IS_ENABLED(CONFIG_IPV6)
899 	inet_rsk(req)->ipv6_opt = NULL;
900 	inet_rsk(req)->pktopts = NULL;
901 #else
902 	inet_rsk(req)->ireq_opt = NULL;
903 #endif
904 }
905 
906 /* return true if req was found in the ehash table */
907 static bool reqsk_queue_unlink(struct request_sock *req)
908 {
909 	struct sock *sk = req_to_sk(req);
910 	bool found = false;
911 
912 	if (sk_hashed(sk)) {
913 		struct inet_hashinfo *hashinfo = tcp_or_dccp_get_hashinfo(sk);
914 		spinlock_t *lock = inet_ehash_lockp(hashinfo, req->rsk_hash);
915 
916 		spin_lock(lock);
917 		found = __sk_nulls_del_node_init_rcu(sk);
918 		spin_unlock(lock);
919 	}
920 	if (timer_pending(&req->rsk_timer) && del_timer_sync(&req->rsk_timer))
921 		reqsk_put(req);
922 	return found;
923 }
924 
925 bool inet_csk_reqsk_queue_drop(struct sock *sk, struct request_sock *req)
926 {
927 	bool unlinked = reqsk_queue_unlink(req);
928 
929 	if (unlinked) {
930 		reqsk_queue_removed(&inet_csk(sk)->icsk_accept_queue, req);
931 		reqsk_put(req);
932 	}
933 	return unlinked;
934 }
935 EXPORT_SYMBOL(inet_csk_reqsk_queue_drop);
936 
937 void inet_csk_reqsk_queue_drop_and_put(struct sock *sk, struct request_sock *req)
938 {
939 	inet_csk_reqsk_queue_drop(sk, req);
940 	reqsk_put(req);
941 }
942 EXPORT_SYMBOL(inet_csk_reqsk_queue_drop_and_put);
943 
944 static void reqsk_timer_handler(struct timer_list *t)
945 {
946 	struct request_sock *req = from_timer(req, t, rsk_timer);
947 	struct request_sock *nreq = NULL, *oreq = req;
948 	struct sock *sk_listener = req->rsk_listener;
949 	struct inet_connection_sock *icsk;
950 	struct request_sock_queue *queue;
951 	struct net *net;
952 	int max_syn_ack_retries, qlen, expire = 0, resend = 0;
953 
954 	if (inet_sk_state_load(sk_listener) != TCP_LISTEN) {
955 		struct sock *nsk;
956 
957 		nsk = reuseport_migrate_sock(sk_listener, req_to_sk(req), NULL);
958 		if (!nsk)
959 			goto drop;
960 
961 		nreq = inet_reqsk_clone(req, nsk);
962 		if (!nreq)
963 			goto drop;
964 
965 		/* The new timer for the cloned req can decrease the 2
966 		 * by calling inet_csk_reqsk_queue_drop_and_put(), so
967 		 * hold another count to prevent use-after-free and
968 		 * call reqsk_put() just before return.
969 		 */
970 		refcount_set(&nreq->rsk_refcnt, 2 + 1);
971 		timer_setup(&nreq->rsk_timer, reqsk_timer_handler, TIMER_PINNED);
972 		reqsk_queue_migrated(&inet_csk(nsk)->icsk_accept_queue, req);
973 
974 		req = nreq;
975 		sk_listener = nsk;
976 	}
977 
978 	icsk = inet_csk(sk_listener);
979 	net = sock_net(sk_listener);
980 	max_syn_ack_retries = icsk->icsk_syn_retries ? :
981 		READ_ONCE(net->ipv4.sysctl_tcp_synack_retries);
982 	/* Normally all the openreqs are young and become mature
983 	 * (i.e. converted to established socket) for first timeout.
984 	 * If synack was not acknowledged for 1 second, it means
985 	 * one of the following things: synack was lost, ack was lost,
986 	 * rtt is high or nobody planned to ack (i.e. synflood).
987 	 * When server is a bit loaded, queue is populated with old
988 	 * open requests, reducing effective size of queue.
989 	 * When server is well loaded, queue size reduces to zero
990 	 * after several minutes of work. It is not synflood,
991 	 * it is normal operation. The solution is pruning
992 	 * too old entries overriding normal timeout, when
993 	 * situation becomes dangerous.
994 	 *
995 	 * Essentially, we reserve half of room for young
996 	 * embrions; and abort old ones without pity, if old
997 	 * ones are about to clog our table.
998 	 */
999 	queue = &icsk->icsk_accept_queue;
1000 	qlen = reqsk_queue_len(queue);
1001 	if ((qlen << 1) > max(8U, READ_ONCE(sk_listener->sk_max_ack_backlog))) {
1002 		int young = reqsk_queue_len_young(queue) << 1;
1003 
1004 		while (max_syn_ack_retries > 2) {
1005 			if (qlen < young)
1006 				break;
1007 			max_syn_ack_retries--;
1008 			young <<= 1;
1009 		}
1010 	}
1011 	syn_ack_recalc(req, max_syn_ack_retries, READ_ONCE(queue->rskq_defer_accept),
1012 		       &expire, &resend);
1013 	req->rsk_ops->syn_ack_timeout(req);
1014 	if (!expire &&
1015 	    (!resend ||
1016 	     !inet_rtx_syn_ack(sk_listener, req) ||
1017 	     inet_rsk(req)->acked)) {
1018 		if (req->num_timeout++ == 0)
1019 			atomic_dec(&queue->young);
1020 		mod_timer(&req->rsk_timer, jiffies + reqsk_timeout(req, TCP_RTO_MAX));
1021 
1022 		if (!nreq)
1023 			return;
1024 
1025 		if (!inet_ehash_insert(req_to_sk(nreq), req_to_sk(oreq), NULL)) {
1026 			/* delete timer */
1027 			inet_csk_reqsk_queue_drop(sk_listener, nreq);
1028 			goto no_ownership;
1029 		}
1030 
1031 		__NET_INC_STATS(net, LINUX_MIB_TCPMIGRATEREQSUCCESS);
1032 		reqsk_migrate_reset(oreq);
1033 		reqsk_queue_removed(&inet_csk(oreq->rsk_listener)->icsk_accept_queue, oreq);
1034 		reqsk_put(oreq);
1035 
1036 		reqsk_put(nreq);
1037 		return;
1038 	}
1039 
1040 	/* Even if we can clone the req, we may need not retransmit any more
1041 	 * SYN+ACKs (nreq->num_timeout > max_syn_ack_retries, etc), or another
1042 	 * CPU may win the "own_req" race so that inet_ehash_insert() fails.
1043 	 */
1044 	if (nreq) {
1045 		__NET_INC_STATS(net, LINUX_MIB_TCPMIGRATEREQFAILURE);
1046 no_ownership:
1047 		reqsk_migrate_reset(nreq);
1048 		reqsk_queue_removed(queue, nreq);
1049 		__reqsk_free(nreq);
1050 	}
1051 
1052 drop:
1053 	inet_csk_reqsk_queue_drop_and_put(oreq->rsk_listener, oreq);
1054 }
1055 
1056 static void reqsk_queue_hash_req(struct request_sock *req,
1057 				 unsigned long timeout)
1058 {
1059 	timer_setup(&req->rsk_timer, reqsk_timer_handler, TIMER_PINNED);
1060 	mod_timer(&req->rsk_timer, jiffies + timeout);
1061 
1062 	inet_ehash_insert(req_to_sk(req), NULL, NULL);
1063 	/* before letting lookups find us, make sure all req fields
1064 	 * are committed to memory and refcnt initialized.
1065 	 */
1066 	smp_wmb();
1067 	refcount_set(&req->rsk_refcnt, 2 + 1);
1068 }
1069 
1070 void inet_csk_reqsk_queue_hash_add(struct sock *sk, struct request_sock *req,
1071 				   unsigned long timeout)
1072 {
1073 	reqsk_queue_hash_req(req, timeout);
1074 	inet_csk_reqsk_queue_added(sk);
1075 }
1076 EXPORT_SYMBOL_GPL(inet_csk_reqsk_queue_hash_add);
1077 
1078 static void inet_clone_ulp(const struct request_sock *req, struct sock *newsk,
1079 			   const gfp_t priority)
1080 {
1081 	struct inet_connection_sock *icsk = inet_csk(newsk);
1082 
1083 	if (!icsk->icsk_ulp_ops)
1084 		return;
1085 
1086 	if (icsk->icsk_ulp_ops->clone)
1087 		icsk->icsk_ulp_ops->clone(req, newsk, priority);
1088 }
1089 
1090 /**
1091  *	inet_csk_clone_lock - clone an inet socket, and lock its clone
1092  *	@sk: the socket to clone
1093  *	@req: request_sock
1094  *	@priority: for allocation (%GFP_KERNEL, %GFP_ATOMIC, etc)
1095  *
1096  *	Caller must unlock socket even in error path (bh_unlock_sock(newsk))
1097  */
1098 struct sock *inet_csk_clone_lock(const struct sock *sk,
1099 				 const struct request_sock *req,
1100 				 const gfp_t priority)
1101 {
1102 	struct sock *newsk = sk_clone_lock(sk, priority);
1103 
1104 	if (newsk) {
1105 		struct inet_connection_sock *newicsk = inet_csk(newsk);
1106 
1107 		inet_sk_set_state(newsk, TCP_SYN_RECV);
1108 		newicsk->icsk_bind_hash = NULL;
1109 		newicsk->icsk_bind2_hash = NULL;
1110 
1111 		inet_sk(newsk)->inet_dport = inet_rsk(req)->ir_rmt_port;
1112 		inet_sk(newsk)->inet_num = inet_rsk(req)->ir_num;
1113 		inet_sk(newsk)->inet_sport = htons(inet_rsk(req)->ir_num);
1114 
1115 		/* listeners have SOCK_RCU_FREE, not the children */
1116 		sock_reset_flag(newsk, SOCK_RCU_FREE);
1117 
1118 		inet_sk(newsk)->mc_list = NULL;
1119 
1120 		newsk->sk_mark = inet_rsk(req)->ir_mark;
1121 		atomic64_set(&newsk->sk_cookie,
1122 			     atomic64_read(&inet_rsk(req)->ir_cookie));
1123 
1124 		newicsk->icsk_retransmits = 0;
1125 		newicsk->icsk_backoff	  = 0;
1126 		newicsk->icsk_probes_out  = 0;
1127 		newicsk->icsk_probes_tstamp = 0;
1128 
1129 		/* Deinitialize accept_queue to trap illegal accesses. */
1130 		memset(&newicsk->icsk_accept_queue, 0, sizeof(newicsk->icsk_accept_queue));
1131 
1132 		inet_clone_ulp(req, newsk, priority);
1133 
1134 		security_inet_csk_clone(newsk, req);
1135 	}
1136 	return newsk;
1137 }
1138 EXPORT_SYMBOL_GPL(inet_csk_clone_lock);
1139 
1140 /*
1141  * At this point, there should be no process reference to this
1142  * socket, and thus no user references at all.  Therefore we
1143  * can assume the socket waitqueue is inactive and nobody will
1144  * try to jump onto it.
1145  */
1146 void inet_csk_destroy_sock(struct sock *sk)
1147 {
1148 	WARN_ON(sk->sk_state != TCP_CLOSE);
1149 	WARN_ON(!sock_flag(sk, SOCK_DEAD));
1150 
1151 	/* It cannot be in hash table! */
1152 	WARN_ON(!sk_unhashed(sk));
1153 
1154 	/* If it has not 0 inet_sk(sk)->inet_num, it must be bound */
1155 	WARN_ON(inet_sk(sk)->inet_num && !inet_csk(sk)->icsk_bind_hash);
1156 
1157 	sk->sk_prot->destroy(sk);
1158 
1159 	sk_stream_kill_queues(sk);
1160 
1161 	xfrm_sk_free_policy(sk);
1162 
1163 	sk_refcnt_debug_release(sk);
1164 
1165 	this_cpu_dec(*sk->sk_prot->orphan_count);
1166 
1167 	sock_put(sk);
1168 }
1169 EXPORT_SYMBOL(inet_csk_destroy_sock);
1170 
1171 /* This function allows to force a closure of a socket after the call to
1172  * tcp/dccp_create_openreq_child().
1173  */
1174 void inet_csk_prepare_forced_close(struct sock *sk)
1175 	__releases(&sk->sk_lock.slock)
1176 {
1177 	/* sk_clone_lock locked the socket and set refcnt to 2 */
1178 	bh_unlock_sock(sk);
1179 	sock_put(sk);
1180 	inet_csk_prepare_for_destroy_sock(sk);
1181 	inet_sk(sk)->inet_num = 0;
1182 }
1183 EXPORT_SYMBOL(inet_csk_prepare_forced_close);
1184 
1185 int inet_csk_listen_start(struct sock *sk)
1186 {
1187 	struct inet_connection_sock *icsk = inet_csk(sk);
1188 	struct inet_sock *inet = inet_sk(sk);
1189 	int err;
1190 
1191 	reqsk_queue_alloc(&icsk->icsk_accept_queue);
1192 
1193 	sk->sk_ack_backlog = 0;
1194 	inet_csk_delack_init(sk);
1195 
1196 	if (sk->sk_txrehash == SOCK_TXREHASH_DEFAULT)
1197 		sk->sk_txrehash = READ_ONCE(sock_net(sk)->core.sysctl_txrehash);
1198 
1199 	/* There is race window here: we announce ourselves listening,
1200 	 * but this transition is still not validated by get_port().
1201 	 * It is OK, because this socket enters to hash table only
1202 	 * after validation is complete.
1203 	 */
1204 	inet_sk_state_store(sk, TCP_LISTEN);
1205 	err = sk->sk_prot->get_port(sk, inet->inet_num);
1206 	if (!err) {
1207 		inet->inet_sport = htons(inet->inet_num);
1208 
1209 		sk_dst_reset(sk);
1210 		err = sk->sk_prot->hash(sk);
1211 
1212 		if (likely(!err))
1213 			return 0;
1214 	}
1215 
1216 	inet_sk_set_state(sk, TCP_CLOSE);
1217 	return err;
1218 }
1219 EXPORT_SYMBOL_GPL(inet_csk_listen_start);
1220 
1221 static void inet_child_forget(struct sock *sk, struct request_sock *req,
1222 			      struct sock *child)
1223 {
1224 	sk->sk_prot->disconnect(child, O_NONBLOCK);
1225 
1226 	sock_orphan(child);
1227 
1228 	this_cpu_inc(*sk->sk_prot->orphan_count);
1229 
1230 	if (sk->sk_protocol == IPPROTO_TCP && tcp_rsk(req)->tfo_listener) {
1231 		BUG_ON(rcu_access_pointer(tcp_sk(child)->fastopen_rsk) != req);
1232 		BUG_ON(sk != req->rsk_listener);
1233 
1234 		/* Paranoid, to prevent race condition if
1235 		 * an inbound pkt destined for child is
1236 		 * blocked by sock lock in tcp_v4_rcv().
1237 		 * Also to satisfy an assertion in
1238 		 * tcp_v4_destroy_sock().
1239 		 */
1240 		RCU_INIT_POINTER(tcp_sk(child)->fastopen_rsk, NULL);
1241 	}
1242 	inet_csk_destroy_sock(child);
1243 }
1244 
1245 struct sock *inet_csk_reqsk_queue_add(struct sock *sk,
1246 				      struct request_sock *req,
1247 				      struct sock *child)
1248 {
1249 	struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
1250 
1251 	spin_lock(&queue->rskq_lock);
1252 	if (unlikely(sk->sk_state != TCP_LISTEN)) {
1253 		inet_child_forget(sk, req, child);
1254 		child = NULL;
1255 	} else {
1256 		req->sk = child;
1257 		req->dl_next = NULL;
1258 		if (queue->rskq_accept_head == NULL)
1259 			WRITE_ONCE(queue->rskq_accept_head, req);
1260 		else
1261 			queue->rskq_accept_tail->dl_next = req;
1262 		queue->rskq_accept_tail = req;
1263 		sk_acceptq_added(sk);
1264 	}
1265 	spin_unlock(&queue->rskq_lock);
1266 	return child;
1267 }
1268 EXPORT_SYMBOL(inet_csk_reqsk_queue_add);
1269 
1270 struct sock *inet_csk_complete_hashdance(struct sock *sk, struct sock *child,
1271 					 struct request_sock *req, bool own_req)
1272 {
1273 	if (own_req) {
1274 		inet_csk_reqsk_queue_drop(req->rsk_listener, req);
1275 		reqsk_queue_removed(&inet_csk(req->rsk_listener)->icsk_accept_queue, req);
1276 
1277 		if (sk != req->rsk_listener) {
1278 			/* another listening sk has been selected,
1279 			 * migrate the req to it.
1280 			 */
1281 			struct request_sock *nreq;
1282 
1283 			/* hold a refcnt for the nreq->rsk_listener
1284 			 * which is assigned in inet_reqsk_clone()
1285 			 */
1286 			sock_hold(sk);
1287 			nreq = inet_reqsk_clone(req, sk);
1288 			if (!nreq) {
1289 				inet_child_forget(sk, req, child);
1290 				goto child_put;
1291 			}
1292 
1293 			refcount_set(&nreq->rsk_refcnt, 1);
1294 			if (inet_csk_reqsk_queue_add(sk, nreq, child)) {
1295 				__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMIGRATEREQSUCCESS);
1296 				reqsk_migrate_reset(req);
1297 				reqsk_put(req);
1298 				return child;
1299 			}
1300 
1301 			__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMIGRATEREQFAILURE);
1302 			reqsk_migrate_reset(nreq);
1303 			__reqsk_free(nreq);
1304 		} else if (inet_csk_reqsk_queue_add(sk, req, child)) {
1305 			return child;
1306 		}
1307 	}
1308 	/* Too bad, another child took ownership of the request, undo. */
1309 child_put:
1310 	bh_unlock_sock(child);
1311 	sock_put(child);
1312 	return NULL;
1313 }
1314 EXPORT_SYMBOL(inet_csk_complete_hashdance);
1315 
1316 /*
1317  *	This routine closes sockets which have been at least partially
1318  *	opened, but not yet accepted.
1319  */
1320 void inet_csk_listen_stop(struct sock *sk)
1321 {
1322 	struct inet_connection_sock *icsk = inet_csk(sk);
1323 	struct request_sock_queue *queue = &icsk->icsk_accept_queue;
1324 	struct request_sock *next, *req;
1325 
1326 	/* Following specs, it would be better either to send FIN
1327 	 * (and enter FIN-WAIT-1, it is normal close)
1328 	 * or to send active reset (abort).
1329 	 * Certainly, it is pretty dangerous while synflood, but it is
1330 	 * bad justification for our negligence 8)
1331 	 * To be honest, we are not able to make either
1332 	 * of the variants now.			--ANK
1333 	 */
1334 	while ((req = reqsk_queue_remove(queue, sk)) != NULL) {
1335 		struct sock *child = req->sk, *nsk;
1336 		struct request_sock *nreq;
1337 
1338 		local_bh_disable();
1339 		bh_lock_sock(child);
1340 		WARN_ON(sock_owned_by_user(child));
1341 		sock_hold(child);
1342 
1343 		nsk = reuseport_migrate_sock(sk, child, NULL);
1344 		if (nsk) {
1345 			nreq = inet_reqsk_clone(req, nsk);
1346 			if (nreq) {
1347 				refcount_set(&nreq->rsk_refcnt, 1);
1348 
1349 				if (inet_csk_reqsk_queue_add(nsk, nreq, child)) {
1350 					__NET_INC_STATS(sock_net(nsk),
1351 							LINUX_MIB_TCPMIGRATEREQSUCCESS);
1352 					reqsk_migrate_reset(req);
1353 				} else {
1354 					__NET_INC_STATS(sock_net(nsk),
1355 							LINUX_MIB_TCPMIGRATEREQFAILURE);
1356 					reqsk_migrate_reset(nreq);
1357 					__reqsk_free(nreq);
1358 				}
1359 
1360 				/* inet_csk_reqsk_queue_add() has already
1361 				 * called inet_child_forget() on failure case.
1362 				 */
1363 				goto skip_child_forget;
1364 			}
1365 		}
1366 
1367 		inet_child_forget(sk, req, child);
1368 skip_child_forget:
1369 		reqsk_put(req);
1370 		bh_unlock_sock(child);
1371 		local_bh_enable();
1372 		sock_put(child);
1373 
1374 		cond_resched();
1375 	}
1376 	if (queue->fastopenq.rskq_rst_head) {
1377 		/* Free all the reqs queued in rskq_rst_head. */
1378 		spin_lock_bh(&queue->fastopenq.lock);
1379 		req = queue->fastopenq.rskq_rst_head;
1380 		queue->fastopenq.rskq_rst_head = NULL;
1381 		spin_unlock_bh(&queue->fastopenq.lock);
1382 		while (req != NULL) {
1383 			next = req->dl_next;
1384 			reqsk_put(req);
1385 			req = next;
1386 		}
1387 	}
1388 	WARN_ON_ONCE(sk->sk_ack_backlog);
1389 }
1390 EXPORT_SYMBOL_GPL(inet_csk_listen_stop);
1391 
1392 void inet_csk_addr2sockaddr(struct sock *sk, struct sockaddr *uaddr)
1393 {
1394 	struct sockaddr_in *sin = (struct sockaddr_in *)uaddr;
1395 	const struct inet_sock *inet = inet_sk(sk);
1396 
1397 	sin->sin_family		= AF_INET;
1398 	sin->sin_addr.s_addr	= inet->inet_daddr;
1399 	sin->sin_port		= inet->inet_dport;
1400 }
1401 EXPORT_SYMBOL_GPL(inet_csk_addr2sockaddr);
1402 
1403 static struct dst_entry *inet_csk_rebuild_route(struct sock *sk, struct flowi *fl)
1404 {
1405 	const struct inet_sock *inet = inet_sk(sk);
1406 	const struct ip_options_rcu *inet_opt;
1407 	__be32 daddr = inet->inet_daddr;
1408 	struct flowi4 *fl4;
1409 	struct rtable *rt;
1410 
1411 	rcu_read_lock();
1412 	inet_opt = rcu_dereference(inet->inet_opt);
1413 	if (inet_opt && inet_opt->opt.srr)
1414 		daddr = inet_opt->opt.faddr;
1415 	fl4 = &fl->u.ip4;
1416 	rt = ip_route_output_ports(sock_net(sk), fl4, sk, daddr,
1417 				   inet->inet_saddr, inet->inet_dport,
1418 				   inet->inet_sport, sk->sk_protocol,
1419 				   RT_CONN_FLAGS(sk), sk->sk_bound_dev_if);
1420 	if (IS_ERR(rt))
1421 		rt = NULL;
1422 	if (rt)
1423 		sk_setup_caps(sk, &rt->dst);
1424 	rcu_read_unlock();
1425 
1426 	return &rt->dst;
1427 }
1428 
1429 struct dst_entry *inet_csk_update_pmtu(struct sock *sk, u32 mtu)
1430 {
1431 	struct dst_entry *dst = __sk_dst_check(sk, 0);
1432 	struct inet_sock *inet = inet_sk(sk);
1433 
1434 	if (!dst) {
1435 		dst = inet_csk_rebuild_route(sk, &inet->cork.fl);
1436 		if (!dst)
1437 			goto out;
1438 	}
1439 	dst->ops->update_pmtu(dst, sk, NULL, mtu, true);
1440 
1441 	dst = __sk_dst_check(sk, 0);
1442 	if (!dst)
1443 		dst = inet_csk_rebuild_route(sk, &inet->cork.fl);
1444 out:
1445 	return dst;
1446 }
1447 EXPORT_SYMBOL_GPL(inet_csk_update_pmtu);
1448