xref: /openbmc/linux/net/ipv4/inet_fragment.c (revision f4877225)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * inet fragments management
4  *
5  * 		Authors:	Pavel Emelyanov <xemul@openvz.org>
6  *				Started as consolidation of ipv4/ip_fragment.c,
7  *				ipv6/reassembly. and ipv6 nf conntrack reassembly
8  */
9 
10 #include <linux/list.h>
11 #include <linux/spinlock.h>
12 #include <linux/module.h>
13 #include <linux/timer.h>
14 #include <linux/mm.h>
15 #include <linux/random.h>
16 #include <linux/skbuff.h>
17 #include <linux/rtnetlink.h>
18 #include <linux/slab.h>
19 #include <linux/rhashtable.h>
20 
21 #include <net/sock.h>
22 #include <net/inet_frag.h>
23 #include <net/inet_ecn.h>
24 #include <net/ip.h>
25 #include <net/ipv6.h>
26 
27 #include "../core/sock_destructor.h"
28 
29 /* Use skb->cb to track consecutive/adjacent fragments coming at
30  * the end of the queue. Nodes in the rb-tree queue will
31  * contain "runs" of one or more adjacent fragments.
32  *
33  * Invariants:
34  * - next_frag is NULL at the tail of a "run";
35  * - the head of a "run" has the sum of all fragment lengths in frag_run_len.
36  */
37 struct ipfrag_skb_cb {
38 	union {
39 		struct inet_skb_parm	h4;
40 		struct inet6_skb_parm	h6;
41 	};
42 	struct sk_buff		*next_frag;
43 	int			frag_run_len;
44 	int			ip_defrag_offset;
45 };
46 
47 #define FRAG_CB(skb)		((struct ipfrag_skb_cb *)((skb)->cb))
48 
fragcb_clear(struct sk_buff * skb)49 static void fragcb_clear(struct sk_buff *skb)
50 {
51 	RB_CLEAR_NODE(&skb->rbnode);
52 	FRAG_CB(skb)->next_frag = NULL;
53 	FRAG_CB(skb)->frag_run_len = skb->len;
54 }
55 
56 /* Append skb to the last "run". */
fragrun_append_to_last(struct inet_frag_queue * q,struct sk_buff * skb)57 static void fragrun_append_to_last(struct inet_frag_queue *q,
58 				   struct sk_buff *skb)
59 {
60 	fragcb_clear(skb);
61 
62 	FRAG_CB(q->last_run_head)->frag_run_len += skb->len;
63 	FRAG_CB(q->fragments_tail)->next_frag = skb;
64 	q->fragments_tail = skb;
65 }
66 
67 /* Create a new "run" with the skb. */
fragrun_create(struct inet_frag_queue * q,struct sk_buff * skb)68 static void fragrun_create(struct inet_frag_queue *q, struct sk_buff *skb)
69 {
70 	BUILD_BUG_ON(sizeof(struct ipfrag_skb_cb) > sizeof(skb->cb));
71 	fragcb_clear(skb);
72 
73 	if (q->last_run_head)
74 		rb_link_node(&skb->rbnode, &q->last_run_head->rbnode,
75 			     &q->last_run_head->rbnode.rb_right);
76 	else
77 		rb_link_node(&skb->rbnode, NULL, &q->rb_fragments.rb_node);
78 	rb_insert_color(&skb->rbnode, &q->rb_fragments);
79 
80 	q->fragments_tail = skb;
81 	q->last_run_head = skb;
82 }
83 
84 /* Given the OR values of all fragments, apply RFC 3168 5.3 requirements
85  * Value : 0xff if frame should be dropped.
86  *         0 or INET_ECN_CE value, to be ORed in to final iph->tos field
87  */
88 const u8 ip_frag_ecn_table[16] = {
89 	/* at least one fragment had CE, and others ECT_0 or ECT_1 */
90 	[IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0]			= INET_ECN_CE,
91 	[IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1]			= INET_ECN_CE,
92 	[IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1]	= INET_ECN_CE,
93 
94 	/* invalid combinations : drop frame */
95 	[IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE] = 0xff,
96 	[IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0] = 0xff,
97 	[IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_1] = 0xff,
98 	[IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff,
99 	[IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0] = 0xff,
100 	[IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1] = 0xff,
101 	[IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff,
102 };
103 EXPORT_SYMBOL(ip_frag_ecn_table);
104 
inet_frags_init(struct inet_frags * f)105 int inet_frags_init(struct inet_frags *f)
106 {
107 	f->frags_cachep = kmem_cache_create(f->frags_cache_name, f->qsize, 0, 0,
108 					    NULL);
109 	if (!f->frags_cachep)
110 		return -ENOMEM;
111 
112 	refcount_set(&f->refcnt, 1);
113 	init_completion(&f->completion);
114 	return 0;
115 }
116 EXPORT_SYMBOL(inet_frags_init);
117 
inet_frags_fini(struct inet_frags * f)118 void inet_frags_fini(struct inet_frags *f)
119 {
120 	if (refcount_dec_and_test(&f->refcnt))
121 		complete(&f->completion);
122 
123 	wait_for_completion(&f->completion);
124 
125 	kmem_cache_destroy(f->frags_cachep);
126 	f->frags_cachep = NULL;
127 }
128 EXPORT_SYMBOL(inet_frags_fini);
129 
130 /* called from rhashtable_free_and_destroy() at netns_frags dismantle */
inet_frags_free_cb(void * ptr,void * arg)131 static void inet_frags_free_cb(void *ptr, void *arg)
132 {
133 	struct inet_frag_queue *fq = ptr;
134 	int count;
135 
136 	count = del_timer_sync(&fq->timer) ? 1 : 0;
137 
138 	spin_lock_bh(&fq->lock);
139 	fq->flags |= INET_FRAG_DROP;
140 	if (!(fq->flags & INET_FRAG_COMPLETE)) {
141 		fq->flags |= INET_FRAG_COMPLETE;
142 		count++;
143 	} else if (fq->flags & INET_FRAG_HASH_DEAD) {
144 		count++;
145 	}
146 	spin_unlock_bh(&fq->lock);
147 
148 	if (refcount_sub_and_test(count, &fq->refcnt))
149 		inet_frag_destroy(fq);
150 }
151 
152 static LLIST_HEAD(fqdir_free_list);
153 
fqdir_free_fn(struct work_struct * work)154 static void fqdir_free_fn(struct work_struct *work)
155 {
156 	struct llist_node *kill_list;
157 	struct fqdir *fqdir, *tmp;
158 	struct inet_frags *f;
159 
160 	/* Atomically snapshot the list of fqdirs to free */
161 	kill_list = llist_del_all(&fqdir_free_list);
162 
163 	/* We need to make sure all ongoing call_rcu(..., inet_frag_destroy_rcu)
164 	 * have completed, since they need to dereference fqdir.
165 	 * Would it not be nice to have kfree_rcu_barrier() ? :)
166 	 */
167 	rcu_barrier();
168 
169 	llist_for_each_entry_safe(fqdir, tmp, kill_list, free_list) {
170 		f = fqdir->f;
171 		if (refcount_dec_and_test(&f->refcnt))
172 			complete(&f->completion);
173 
174 		kfree(fqdir);
175 	}
176 }
177 
178 static DECLARE_WORK(fqdir_free_work, fqdir_free_fn);
179 
fqdir_work_fn(struct work_struct * work)180 static void fqdir_work_fn(struct work_struct *work)
181 {
182 	struct fqdir *fqdir = container_of(work, struct fqdir, destroy_work);
183 
184 	rhashtable_free_and_destroy(&fqdir->rhashtable, inet_frags_free_cb, NULL);
185 
186 	if (llist_add(&fqdir->free_list, &fqdir_free_list))
187 		queue_work(system_wq, &fqdir_free_work);
188 }
189 
fqdir_init(struct fqdir ** fqdirp,struct inet_frags * f,struct net * net)190 int fqdir_init(struct fqdir **fqdirp, struct inet_frags *f, struct net *net)
191 {
192 	struct fqdir *fqdir = kzalloc(sizeof(*fqdir), GFP_KERNEL);
193 	int res;
194 
195 	if (!fqdir)
196 		return -ENOMEM;
197 	fqdir->f = f;
198 	fqdir->net = net;
199 	res = rhashtable_init(&fqdir->rhashtable, &fqdir->f->rhash_params);
200 	if (res < 0) {
201 		kfree(fqdir);
202 		return res;
203 	}
204 	refcount_inc(&f->refcnt);
205 	*fqdirp = fqdir;
206 	return 0;
207 }
208 EXPORT_SYMBOL(fqdir_init);
209 
210 static struct workqueue_struct *inet_frag_wq;
211 
inet_frag_wq_init(void)212 static int __init inet_frag_wq_init(void)
213 {
214 	inet_frag_wq = create_workqueue("inet_frag_wq");
215 	if (!inet_frag_wq)
216 		panic("Could not create inet frag workq");
217 	return 0;
218 }
219 
220 pure_initcall(inet_frag_wq_init);
221 
fqdir_exit(struct fqdir * fqdir)222 void fqdir_exit(struct fqdir *fqdir)
223 {
224 	INIT_WORK(&fqdir->destroy_work, fqdir_work_fn);
225 	queue_work(inet_frag_wq, &fqdir->destroy_work);
226 }
227 EXPORT_SYMBOL(fqdir_exit);
228 
inet_frag_kill(struct inet_frag_queue * fq)229 void inet_frag_kill(struct inet_frag_queue *fq)
230 {
231 	if (del_timer(&fq->timer))
232 		refcount_dec(&fq->refcnt);
233 
234 	if (!(fq->flags & INET_FRAG_COMPLETE)) {
235 		struct fqdir *fqdir = fq->fqdir;
236 
237 		fq->flags |= INET_FRAG_COMPLETE;
238 		rcu_read_lock();
239 		/* The RCU read lock provides a memory barrier
240 		 * guaranteeing that if fqdir->dead is false then
241 		 * the hash table destruction will not start until
242 		 * after we unlock.  Paired with fqdir_pre_exit().
243 		 */
244 		if (!READ_ONCE(fqdir->dead)) {
245 			rhashtable_remove_fast(&fqdir->rhashtable, &fq->node,
246 					       fqdir->f->rhash_params);
247 			refcount_dec(&fq->refcnt);
248 		} else {
249 			fq->flags |= INET_FRAG_HASH_DEAD;
250 		}
251 		rcu_read_unlock();
252 	}
253 }
254 EXPORT_SYMBOL(inet_frag_kill);
255 
inet_frag_destroy_rcu(struct rcu_head * head)256 static void inet_frag_destroy_rcu(struct rcu_head *head)
257 {
258 	struct inet_frag_queue *q = container_of(head, struct inet_frag_queue,
259 						 rcu);
260 	struct inet_frags *f = q->fqdir->f;
261 
262 	if (f->destructor)
263 		f->destructor(q);
264 	kmem_cache_free(f->frags_cachep, q);
265 }
266 
inet_frag_rbtree_purge(struct rb_root * root,enum skb_drop_reason reason)267 unsigned int inet_frag_rbtree_purge(struct rb_root *root,
268 				    enum skb_drop_reason reason)
269 {
270 	struct rb_node *p = rb_first(root);
271 	unsigned int sum = 0;
272 
273 	while (p) {
274 		struct sk_buff *skb = rb_entry(p, struct sk_buff, rbnode);
275 
276 		p = rb_next(p);
277 		rb_erase(&skb->rbnode, root);
278 		while (skb) {
279 			struct sk_buff *next = FRAG_CB(skb)->next_frag;
280 
281 			sum += skb->truesize;
282 			kfree_skb_reason(skb, reason);
283 			skb = next;
284 		}
285 	}
286 	return sum;
287 }
288 EXPORT_SYMBOL(inet_frag_rbtree_purge);
289 
inet_frag_destroy(struct inet_frag_queue * q)290 void inet_frag_destroy(struct inet_frag_queue *q)
291 {
292 	unsigned int sum, sum_truesize = 0;
293 	enum skb_drop_reason reason;
294 	struct inet_frags *f;
295 	struct fqdir *fqdir;
296 
297 	WARN_ON(!(q->flags & INET_FRAG_COMPLETE));
298 	reason = (q->flags & INET_FRAG_DROP) ?
299 			SKB_DROP_REASON_FRAG_REASM_TIMEOUT :
300 			SKB_CONSUMED;
301 	WARN_ON(del_timer(&q->timer) != 0);
302 
303 	/* Release all fragment data. */
304 	fqdir = q->fqdir;
305 	f = fqdir->f;
306 	sum_truesize = inet_frag_rbtree_purge(&q->rb_fragments, reason);
307 	sum = sum_truesize + f->qsize;
308 
309 	call_rcu(&q->rcu, inet_frag_destroy_rcu);
310 
311 	sub_frag_mem_limit(fqdir, sum);
312 }
313 EXPORT_SYMBOL(inet_frag_destroy);
314 
inet_frag_alloc(struct fqdir * fqdir,struct inet_frags * f,void * arg)315 static struct inet_frag_queue *inet_frag_alloc(struct fqdir *fqdir,
316 					       struct inet_frags *f,
317 					       void *arg)
318 {
319 	struct inet_frag_queue *q;
320 
321 	q = kmem_cache_zalloc(f->frags_cachep, GFP_ATOMIC);
322 	if (!q)
323 		return NULL;
324 
325 	q->fqdir = fqdir;
326 	f->constructor(q, arg);
327 	add_frag_mem_limit(fqdir, f->qsize);
328 
329 	timer_setup(&q->timer, f->frag_expire, 0);
330 	spin_lock_init(&q->lock);
331 	refcount_set(&q->refcnt, 3);
332 
333 	return q;
334 }
335 
inet_frag_create(struct fqdir * fqdir,void * arg,struct inet_frag_queue ** prev)336 static struct inet_frag_queue *inet_frag_create(struct fqdir *fqdir,
337 						void *arg,
338 						struct inet_frag_queue **prev)
339 {
340 	struct inet_frags *f = fqdir->f;
341 	struct inet_frag_queue *q;
342 
343 	q = inet_frag_alloc(fqdir, f, arg);
344 	if (!q) {
345 		*prev = ERR_PTR(-ENOMEM);
346 		return NULL;
347 	}
348 	mod_timer(&q->timer, jiffies + fqdir->timeout);
349 
350 	*prev = rhashtable_lookup_get_insert_key(&fqdir->rhashtable, &q->key,
351 						 &q->node, f->rhash_params);
352 	if (*prev) {
353 		q->flags |= INET_FRAG_COMPLETE;
354 		inet_frag_kill(q);
355 		inet_frag_destroy(q);
356 		return NULL;
357 	}
358 	return q;
359 }
360 
361 /* TODO : call from rcu_read_lock() and no longer use refcount_inc_not_zero() */
inet_frag_find(struct fqdir * fqdir,void * key)362 struct inet_frag_queue *inet_frag_find(struct fqdir *fqdir, void *key)
363 {
364 	/* This pairs with WRITE_ONCE() in fqdir_pre_exit(). */
365 	long high_thresh = READ_ONCE(fqdir->high_thresh);
366 	struct inet_frag_queue *fq = NULL, *prev;
367 
368 	if (!high_thresh || frag_mem_limit(fqdir) > high_thresh)
369 		return NULL;
370 
371 	rcu_read_lock();
372 
373 	prev = rhashtable_lookup(&fqdir->rhashtable, key, fqdir->f->rhash_params);
374 	if (!prev)
375 		fq = inet_frag_create(fqdir, key, &prev);
376 	if (!IS_ERR_OR_NULL(prev)) {
377 		fq = prev;
378 		if (!refcount_inc_not_zero(&fq->refcnt))
379 			fq = NULL;
380 	}
381 	rcu_read_unlock();
382 	return fq;
383 }
384 EXPORT_SYMBOL(inet_frag_find);
385 
inet_frag_queue_insert(struct inet_frag_queue * q,struct sk_buff * skb,int offset,int end)386 int inet_frag_queue_insert(struct inet_frag_queue *q, struct sk_buff *skb,
387 			   int offset, int end)
388 {
389 	struct sk_buff *last = q->fragments_tail;
390 
391 	/* RFC5722, Section 4, amended by Errata ID : 3089
392 	 *                          When reassembling an IPv6 datagram, if
393 	 *   one or more its constituent fragments is determined to be an
394 	 *   overlapping fragment, the entire datagram (and any constituent
395 	 *   fragments) MUST be silently discarded.
396 	 *
397 	 * Duplicates, however, should be ignored (i.e. skb dropped, but the
398 	 * queue/fragments kept for later reassembly).
399 	 */
400 	if (!last)
401 		fragrun_create(q, skb);  /* First fragment. */
402 	else if (FRAG_CB(last)->ip_defrag_offset + last->len < end) {
403 		/* This is the common case: skb goes to the end. */
404 		/* Detect and discard overlaps. */
405 		if (offset < FRAG_CB(last)->ip_defrag_offset + last->len)
406 			return IPFRAG_OVERLAP;
407 		if (offset == FRAG_CB(last)->ip_defrag_offset + last->len)
408 			fragrun_append_to_last(q, skb);
409 		else
410 			fragrun_create(q, skb);
411 	} else {
412 		/* Binary search. Note that skb can become the first fragment,
413 		 * but not the last (covered above).
414 		 */
415 		struct rb_node **rbn, *parent;
416 
417 		rbn = &q->rb_fragments.rb_node;
418 		do {
419 			struct sk_buff *curr;
420 			int curr_run_end;
421 
422 			parent = *rbn;
423 			curr = rb_to_skb(parent);
424 			curr_run_end = FRAG_CB(curr)->ip_defrag_offset +
425 					FRAG_CB(curr)->frag_run_len;
426 			if (end <= FRAG_CB(curr)->ip_defrag_offset)
427 				rbn = &parent->rb_left;
428 			else if (offset >= curr_run_end)
429 				rbn = &parent->rb_right;
430 			else if (offset >= FRAG_CB(curr)->ip_defrag_offset &&
431 				 end <= curr_run_end)
432 				return IPFRAG_DUP;
433 			else
434 				return IPFRAG_OVERLAP;
435 		} while (*rbn);
436 		/* Here we have parent properly set, and rbn pointing to
437 		 * one of its NULL left/right children. Insert skb.
438 		 */
439 		fragcb_clear(skb);
440 		rb_link_node(&skb->rbnode, parent, rbn);
441 		rb_insert_color(&skb->rbnode, &q->rb_fragments);
442 	}
443 
444 	FRAG_CB(skb)->ip_defrag_offset = offset;
445 
446 	return IPFRAG_OK;
447 }
448 EXPORT_SYMBOL(inet_frag_queue_insert);
449 
inet_frag_reasm_prepare(struct inet_frag_queue * q,struct sk_buff * skb,struct sk_buff * parent)450 void *inet_frag_reasm_prepare(struct inet_frag_queue *q, struct sk_buff *skb,
451 			      struct sk_buff *parent)
452 {
453 	struct sk_buff *fp, *head = skb_rb_first(&q->rb_fragments);
454 	void (*destructor)(struct sk_buff *);
455 	unsigned int orig_truesize = 0;
456 	struct sk_buff **nextp = NULL;
457 	struct sock *sk = skb->sk;
458 	int delta;
459 
460 	if (sk && is_skb_wmem(skb)) {
461 		/* TX: skb->sk might have been passed as argument to
462 		 * dst->output and must remain valid until tx completes.
463 		 *
464 		 * Move sk to reassembled skb and fix up wmem accounting.
465 		 */
466 		orig_truesize = skb->truesize;
467 		destructor = skb->destructor;
468 	}
469 
470 	if (head != skb) {
471 		fp = skb_clone(skb, GFP_ATOMIC);
472 		if (!fp) {
473 			head = skb;
474 			goto out_restore_sk;
475 		}
476 		FRAG_CB(fp)->next_frag = FRAG_CB(skb)->next_frag;
477 		if (RB_EMPTY_NODE(&skb->rbnode))
478 			FRAG_CB(parent)->next_frag = fp;
479 		else
480 			rb_replace_node(&skb->rbnode, &fp->rbnode,
481 					&q->rb_fragments);
482 		if (q->fragments_tail == skb)
483 			q->fragments_tail = fp;
484 
485 		if (orig_truesize) {
486 			/* prevent skb_morph from releasing sk */
487 			skb->sk = NULL;
488 			skb->destructor = NULL;
489 		}
490 		skb_morph(skb, head);
491 		FRAG_CB(skb)->next_frag = FRAG_CB(head)->next_frag;
492 		rb_replace_node(&head->rbnode, &skb->rbnode,
493 				&q->rb_fragments);
494 		consume_skb(head);
495 		head = skb;
496 	}
497 	WARN_ON(FRAG_CB(head)->ip_defrag_offset != 0);
498 
499 	delta = -head->truesize;
500 
501 	/* Head of list must not be cloned. */
502 	if (skb_unclone(head, GFP_ATOMIC))
503 		goto out_restore_sk;
504 
505 	delta += head->truesize;
506 	if (delta)
507 		add_frag_mem_limit(q->fqdir, delta);
508 
509 	/* If the first fragment is fragmented itself, we split
510 	 * it to two chunks: the first with data and paged part
511 	 * and the second, holding only fragments.
512 	 */
513 	if (skb_has_frag_list(head)) {
514 		struct sk_buff *clone;
515 		int i, plen = 0;
516 
517 		clone = alloc_skb(0, GFP_ATOMIC);
518 		if (!clone)
519 			goto out_restore_sk;
520 		skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
521 		skb_frag_list_init(head);
522 		for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
523 			plen += skb_frag_size(&skb_shinfo(head)->frags[i]);
524 		clone->data_len = head->data_len - plen;
525 		clone->len = clone->data_len;
526 		head->truesize += clone->truesize;
527 		clone->csum = 0;
528 		clone->ip_summed = head->ip_summed;
529 		add_frag_mem_limit(q->fqdir, clone->truesize);
530 		skb_shinfo(head)->frag_list = clone;
531 		nextp = &clone->next;
532 	} else {
533 		nextp = &skb_shinfo(head)->frag_list;
534 	}
535 
536 out_restore_sk:
537 	if (orig_truesize) {
538 		int ts_delta = head->truesize - orig_truesize;
539 
540 		/* if this reassembled skb is fragmented later,
541 		 * fraglist skbs will get skb->sk assigned from head->sk,
542 		 * and each frag skb will be released via sock_wfree.
543 		 *
544 		 * Update sk_wmem_alloc.
545 		 */
546 		head->sk = sk;
547 		head->destructor = destructor;
548 		refcount_add(ts_delta, &sk->sk_wmem_alloc);
549 	}
550 
551 	return nextp;
552 }
553 EXPORT_SYMBOL(inet_frag_reasm_prepare);
554 
inet_frag_reasm_finish(struct inet_frag_queue * q,struct sk_buff * head,void * reasm_data,bool try_coalesce)555 void inet_frag_reasm_finish(struct inet_frag_queue *q, struct sk_buff *head,
556 			    void *reasm_data, bool try_coalesce)
557 {
558 	struct sock *sk = is_skb_wmem(head) ? head->sk : NULL;
559 	const unsigned int head_truesize = head->truesize;
560 	struct sk_buff **nextp = reasm_data;
561 	struct rb_node *rbn;
562 	struct sk_buff *fp;
563 	int sum_truesize;
564 
565 	skb_push(head, head->data - skb_network_header(head));
566 
567 	/* Traverse the tree in order, to build frag_list. */
568 	fp = FRAG_CB(head)->next_frag;
569 	rbn = rb_next(&head->rbnode);
570 	rb_erase(&head->rbnode, &q->rb_fragments);
571 
572 	sum_truesize = head->truesize;
573 	while (rbn || fp) {
574 		/* fp points to the next sk_buff in the current run;
575 		 * rbn points to the next run.
576 		 */
577 		/* Go through the current run. */
578 		while (fp) {
579 			struct sk_buff *next_frag = FRAG_CB(fp)->next_frag;
580 			bool stolen;
581 			int delta;
582 
583 			sum_truesize += fp->truesize;
584 			if (head->ip_summed != fp->ip_summed)
585 				head->ip_summed = CHECKSUM_NONE;
586 			else if (head->ip_summed == CHECKSUM_COMPLETE)
587 				head->csum = csum_add(head->csum, fp->csum);
588 
589 			if (try_coalesce && skb_try_coalesce(head, fp, &stolen,
590 							     &delta)) {
591 				kfree_skb_partial(fp, stolen);
592 			} else {
593 				fp->prev = NULL;
594 				memset(&fp->rbnode, 0, sizeof(fp->rbnode));
595 				fp->sk = NULL;
596 
597 				head->data_len += fp->len;
598 				head->len += fp->len;
599 				head->truesize += fp->truesize;
600 
601 				*nextp = fp;
602 				nextp = &fp->next;
603 			}
604 
605 			fp = next_frag;
606 		}
607 		/* Move to the next run. */
608 		if (rbn) {
609 			struct rb_node *rbnext = rb_next(rbn);
610 
611 			fp = rb_to_skb(rbn);
612 			rb_erase(rbn, &q->rb_fragments);
613 			rbn = rbnext;
614 		}
615 	}
616 	sub_frag_mem_limit(q->fqdir, sum_truesize);
617 
618 	*nextp = NULL;
619 	skb_mark_not_on_list(head);
620 	head->prev = NULL;
621 	head->tstamp = q->stamp;
622 	head->mono_delivery_time = q->mono_delivery_time;
623 
624 	if (sk)
625 		refcount_add(sum_truesize - head_truesize, &sk->sk_wmem_alloc);
626 }
627 EXPORT_SYMBOL(inet_frag_reasm_finish);
628 
inet_frag_pull_head(struct inet_frag_queue * q)629 struct sk_buff *inet_frag_pull_head(struct inet_frag_queue *q)
630 {
631 	struct sk_buff *head, *skb;
632 
633 	head = skb_rb_first(&q->rb_fragments);
634 	if (!head)
635 		return NULL;
636 	skb = FRAG_CB(head)->next_frag;
637 	if (skb)
638 		rb_replace_node(&head->rbnode, &skb->rbnode,
639 				&q->rb_fragments);
640 	else
641 		rb_erase(&head->rbnode, &q->rb_fragments);
642 	memset(&head->rbnode, 0, sizeof(head->rbnode));
643 	barrier();
644 
645 	if (head == q->fragments_tail)
646 		q->fragments_tail = NULL;
647 
648 	sub_frag_mem_limit(q->fqdir, head->truesize);
649 
650 	return head;
651 }
652 EXPORT_SYMBOL(inet_frag_pull_head);
653