xref: /openbmc/linux/net/core/xdp.c (revision e7f127b2) 
1 // SPDX-License-Identifier: GPL-2.0-only
2 /* net/core/xdp.c
3  *
4  * Copyright (c) 2017 Jesper Dangaard Brouer, Red Hat Inc.
5  */
6 #include <linux/bpf.h>
7 #include <linux/filter.h>
8 #include <linux/types.h>
9 #include <linux/mm.h>
10 #include <linux/netdevice.h>
11 #include <linux/slab.h>
12 #include <linux/idr.h>
13 #include <linux/rhashtable.h>
14 #include <linux/bug.h>
15 #include <net/page_pool.h>
16 
17 #include <net/xdp.h>
18 #include <net/xdp_priv.h> /* struct xdp_mem_allocator */
19 #include <trace/events/xdp.h>
20 #include <net/xdp_sock_drv.h>
21 
22 #define REG_STATE_NEW		0x0
23 #define REG_STATE_REGISTERED	0x1
24 #define REG_STATE_UNREGISTERED	0x2
25 #define REG_STATE_UNUSED	0x3
26 
27 static DEFINE_IDA(mem_id_pool);
28 static DEFINE_MUTEX(mem_id_lock);
29 #define MEM_ID_MAX 0xFFFE
30 #define MEM_ID_MIN 1
31 static int mem_id_next = MEM_ID_MIN;
32 
33 static bool mem_id_init; /* false */
34 static struct rhashtable *mem_id_ht;
35 
36 static u32 xdp_mem_id_hashfn(const void *data, u32 len, u32 seed)
37 {
38 	const u32 *k = data;
39 	const u32 key = *k;
40 
41 	BUILD_BUG_ON(sizeof_field(struct xdp_mem_allocator, mem.id)
42 		     != sizeof(u32));
43 
44 	/* Use cyclic increasing ID as direct hash key */
45 	return key;
46 }
47 
48 static int xdp_mem_id_cmp(struct rhashtable_compare_arg *arg,
49 			  const void *ptr)
50 {
51 	const struct xdp_mem_allocator *xa = ptr;
52 	u32 mem_id = *(u32 *)arg->key;
53 
54 	return xa->mem.id != mem_id;
55 }
56 
57 static const struct rhashtable_params mem_id_rht_params = {
58 	.nelem_hint = 64,
59 	.head_offset = offsetof(struct xdp_mem_allocator, node),
60 	.key_offset  = offsetof(struct xdp_mem_allocator, mem.id),
61 	.key_len = sizeof_field(struct xdp_mem_allocator, mem.id),
62 	.max_size = MEM_ID_MAX,
63 	.min_size = 8,
64 	.automatic_shrinking = true,
65 	.hashfn    = xdp_mem_id_hashfn,
66 	.obj_cmpfn = xdp_mem_id_cmp,
67 };
68 
69 static void __xdp_mem_allocator_rcu_free(struct rcu_head *rcu)
70 {
71 	struct xdp_mem_allocator *xa;
72 
73 	xa = container_of(rcu, struct xdp_mem_allocator, rcu);
74 
75 	/* Allow this ID to be reused */
76 	ida_simple_remove(&mem_id_pool, xa->mem.id);
77 
78 	kfree(xa);
79 }
80 
81 static void mem_xa_remove(struct xdp_mem_allocator *xa)
82 {
83 	trace_mem_disconnect(xa);
84 
85 	if (!rhashtable_remove_fast(mem_id_ht, &xa->node, mem_id_rht_params))
86 		call_rcu(&xa->rcu, __xdp_mem_allocator_rcu_free);
87 }
88 
89 static void mem_allocator_disconnect(void *allocator)
90 {
91 	struct xdp_mem_allocator *xa;
92 	struct rhashtable_iter iter;
93 
94 	mutex_lock(&mem_id_lock);
95 
96 	rhashtable_walk_enter(mem_id_ht, &iter);
97 	do {
98 		rhashtable_walk_start(&iter);
99 
100 		while ((xa = rhashtable_walk_next(&iter)) && !IS_ERR(xa)) {
101 			if (xa->allocator == allocator)
102 				mem_xa_remove(xa);
103 		}
104 
105 		rhashtable_walk_stop(&iter);
106 
107 	} while (xa == ERR_PTR(-EAGAIN));
108 	rhashtable_walk_exit(&iter);
109 
110 	mutex_unlock(&mem_id_lock);
111 }
112 
113 void xdp_unreg_mem_model(struct xdp_mem_info *mem)
114 {
115 	struct xdp_mem_allocator *xa;
116 	int type = mem->type;
117 	int id = mem->id;
118 
119 	/* Reset mem info to defaults */
120 	mem->id = 0;
121 	mem->type = 0;
122 
123 	if (id == 0)
124 		return;
125 
126 	if (type == MEM_TYPE_PAGE_POOL) {
127 		rcu_read_lock();
128 		xa = rhashtable_lookup(mem_id_ht, &id, mem_id_rht_params);
129 		page_pool_destroy(xa->page_pool);
130 		rcu_read_unlock();
131 	}
132 }
133 EXPORT_SYMBOL_GPL(xdp_unreg_mem_model);
134 
135 void xdp_rxq_info_unreg_mem_model(struct xdp_rxq_info *xdp_rxq)
136 {
137 	if (xdp_rxq->reg_state != REG_STATE_REGISTERED) {
138 		WARN(1, "Missing register, driver bug");
139 		return;
140 	}
141 
142 	xdp_unreg_mem_model(&xdp_rxq->mem);
143 }
144 EXPORT_SYMBOL_GPL(xdp_rxq_info_unreg_mem_model);
145 
146 void xdp_rxq_info_unreg(struct xdp_rxq_info *xdp_rxq)
147 {
148 	/* Simplify driver cleanup code paths, allow unreg "unused" */
149 	if (xdp_rxq->reg_state == REG_STATE_UNUSED)
150 		return;
151 
152 	xdp_rxq_info_unreg_mem_model(xdp_rxq);
153 
154 	xdp_rxq->reg_state = REG_STATE_UNREGISTERED;
155 	xdp_rxq->dev = NULL;
156 }
157 EXPORT_SYMBOL_GPL(xdp_rxq_info_unreg);
158 
159 static void xdp_rxq_info_init(struct xdp_rxq_info *xdp_rxq)
160 {
161 	memset(xdp_rxq, 0, sizeof(*xdp_rxq));
162 }
163 
164 /* Returns 0 on success, negative on failure */
165 int xdp_rxq_info_reg(struct xdp_rxq_info *xdp_rxq,
166 		     struct net_device *dev, u32 queue_index, unsigned int napi_id)
167 {
168 	if (!dev) {
169 		WARN(1, "Missing net_device from driver");
170 		return -ENODEV;
171 	}
172 
173 	if (xdp_rxq->reg_state == REG_STATE_UNUSED) {
174 		WARN(1, "Driver promised not to register this");
175 		return -EINVAL;
176 	}
177 
178 	if (xdp_rxq->reg_state == REG_STATE_REGISTERED) {
179 		WARN(1, "Missing unregister, handled but fix driver");
180 		xdp_rxq_info_unreg(xdp_rxq);
181 	}
182 
183 	/* State either UNREGISTERED or NEW */
184 	xdp_rxq_info_init(xdp_rxq);
185 	xdp_rxq->dev = dev;
186 	xdp_rxq->queue_index = queue_index;
187 	xdp_rxq->napi_id = napi_id;
188 
189 	xdp_rxq->reg_state = REG_STATE_REGISTERED;
190 	return 0;
191 }
192 EXPORT_SYMBOL_GPL(xdp_rxq_info_reg);
193 
194 void xdp_rxq_info_unused(struct xdp_rxq_info *xdp_rxq)
195 {
196 	xdp_rxq->reg_state = REG_STATE_UNUSED;
197 }
198 EXPORT_SYMBOL_GPL(xdp_rxq_info_unused);
199 
200 bool xdp_rxq_info_is_reg(struct xdp_rxq_info *xdp_rxq)
201 {
202 	return (xdp_rxq->reg_state == REG_STATE_REGISTERED);
203 }
204 EXPORT_SYMBOL_GPL(xdp_rxq_info_is_reg);
205 
206 static int __mem_id_init_hash_table(void)
207 {
208 	struct rhashtable *rht;
209 	int ret;
210 
211 	if (unlikely(mem_id_init))
212 		return 0;
213 
214 	rht = kzalloc(sizeof(*rht), GFP_KERNEL);
215 	if (!rht)
216 		return -ENOMEM;
217 
218 	ret = rhashtable_init(rht, &mem_id_rht_params);
219 	if (ret < 0) {
220 		kfree(rht);
221 		return ret;
222 	}
223 	mem_id_ht = rht;
224 	smp_mb(); /* mutex lock should provide enough pairing */
225 	mem_id_init = true;
226 
227 	return 0;
228 }
229 
230 /* Allocate a cyclic ID that maps to allocator pointer.
231  * See: https://www.kernel.org/doc/html/latest/core-api/idr.html
232  *
233  * Caller must lock mem_id_lock.
234  */
235 static int __mem_id_cyclic_get(gfp_t gfp)
236 {
237 	int retries = 1;
238 	int id;
239 
240 again:
241 	id = ida_simple_get(&mem_id_pool, mem_id_next, MEM_ID_MAX, gfp);
242 	if (id < 0) {
243 		if (id == -ENOSPC) {
244 			/* Cyclic allocator, reset next id */
245 			if (retries--) {
246 				mem_id_next = MEM_ID_MIN;
247 				goto again;
248 			}
249 		}
250 		return id; /* errno */
251 	}
252 	mem_id_next = id + 1;
253 
254 	return id;
255 }
256 
257 static bool __is_supported_mem_type(enum xdp_mem_type type)
258 {
259 	if (type == MEM_TYPE_PAGE_POOL)
260 		return is_page_pool_compiled_in();
261 
262 	if (type >= MEM_TYPE_MAX)
263 		return false;
264 
265 	return true;
266 }
267 
268 static struct xdp_mem_allocator *__xdp_reg_mem_model(struct xdp_mem_info *mem,
269 						     enum xdp_mem_type type,
270 						     void *allocator)
271 {
272 	struct xdp_mem_allocator *xdp_alloc;
273 	gfp_t gfp = GFP_KERNEL;
274 	int id, errno, ret;
275 	void *ptr;
276 
277 	if (!__is_supported_mem_type(type))
278 		return ERR_PTR(-EOPNOTSUPP);
279 
280 	mem->type = type;
281 
282 	if (!allocator) {
283 		if (type == MEM_TYPE_PAGE_POOL)
284 			return ERR_PTR(-EINVAL); /* Setup time check page_pool req */
285 		return NULL;
286 	}
287 
288 	/* Delay init of rhashtable to save memory if feature isn't used */
289 	if (!mem_id_init) {
290 		mutex_lock(&mem_id_lock);
291 		ret = __mem_id_init_hash_table();
292 		mutex_unlock(&mem_id_lock);
293 		if (ret < 0) {
294 			WARN_ON(1);
295 			return ERR_PTR(ret);
296 		}
297 	}
298 
299 	xdp_alloc = kzalloc(sizeof(*xdp_alloc), gfp);
300 	if (!xdp_alloc)
301 		return ERR_PTR(-ENOMEM);
302 
303 	mutex_lock(&mem_id_lock);
304 	id = __mem_id_cyclic_get(gfp);
305 	if (id < 0) {
306 		errno = id;
307 		goto err;
308 	}
309 	mem->id = id;
310 	xdp_alloc->mem = *mem;
311 	xdp_alloc->allocator = allocator;
312 
313 	/* Insert allocator into ID lookup table */
314 	ptr = rhashtable_insert_slow(mem_id_ht, &id, &xdp_alloc->node);
315 	if (IS_ERR(ptr)) {
316 		ida_simple_remove(&mem_id_pool, mem->id);
317 		mem->id = 0;
318 		errno = PTR_ERR(ptr);
319 		goto err;
320 	}
321 
322 	if (type == MEM_TYPE_PAGE_POOL)
323 		page_pool_use_xdp_mem(allocator, mem_allocator_disconnect, mem);
324 
325 	mutex_unlock(&mem_id_lock);
326 
327 	return xdp_alloc;
328 err:
329 	mutex_unlock(&mem_id_lock);
330 	kfree(xdp_alloc);
331 	return ERR_PTR(errno);
332 }
333 
334 int xdp_reg_mem_model(struct xdp_mem_info *mem,
335 		      enum xdp_mem_type type, void *allocator)
336 {
337 	struct xdp_mem_allocator *xdp_alloc;
338 
339 	xdp_alloc = __xdp_reg_mem_model(mem, type, allocator);
340 	if (IS_ERR(xdp_alloc))
341 		return PTR_ERR(xdp_alloc);
342 	return 0;
343 }
344 EXPORT_SYMBOL_GPL(xdp_reg_mem_model);
345 
346 int xdp_rxq_info_reg_mem_model(struct xdp_rxq_info *xdp_rxq,
347 			       enum xdp_mem_type type, void *allocator)
348 {
349 	struct xdp_mem_allocator *xdp_alloc;
350 
351 	if (xdp_rxq->reg_state != REG_STATE_REGISTERED) {
352 		WARN(1, "Missing register, driver bug");
353 		return -EFAULT;
354 	}
355 
356 	xdp_alloc = __xdp_reg_mem_model(&xdp_rxq->mem, type, allocator);
357 	if (IS_ERR(xdp_alloc))
358 		return PTR_ERR(xdp_alloc);
359 
360 	trace_mem_connect(xdp_alloc, xdp_rxq);
361 	return 0;
362 }
363 
364 EXPORT_SYMBOL_GPL(xdp_rxq_info_reg_mem_model);
365 
366 /* XDP RX runs under NAPI protection, and in different delivery error
367  * scenarios (e.g. queue full), it is possible to return the xdp_frame
368  * while still leveraging this protection.  The @napi_direct boolean
369  * is used for those calls sites.  Thus, allowing for faster recycling
370  * of xdp_frames/pages in those cases.
371  */
372 static void __xdp_return(void *data, struct xdp_mem_info *mem, bool napi_direct,
373 			 struct xdp_buff *xdp)
374 {
375 	struct xdp_mem_allocator *xa;
376 	struct page *page;
377 
378 	switch (mem->type) {
379 	case MEM_TYPE_PAGE_POOL:
380 		rcu_read_lock();
381 		/* mem->id is valid, checked in xdp_rxq_info_reg_mem_model() */
382 		xa = rhashtable_lookup(mem_id_ht, &mem->id, mem_id_rht_params);
383 		page = virt_to_head_page(data);
384 		if (napi_direct && xdp_return_frame_no_direct())
385 			napi_direct = false;
386 		page_pool_put_full_page(xa->page_pool, page, napi_direct);
387 		rcu_read_unlock();
388 		break;
389 	case MEM_TYPE_PAGE_SHARED:
390 		page_frag_free(data);
391 		break;
392 	case MEM_TYPE_PAGE_ORDER0:
393 		page = virt_to_page(data); /* Assumes order0 page*/
394 		put_page(page);
395 		break;
396 	case MEM_TYPE_XSK_BUFF_POOL:
397 		/* NB! Only valid from an xdp_buff! */
398 		xsk_buff_free(xdp);
399 		break;
400 	default:
401 		/* Not possible, checked in xdp_rxq_info_reg_mem_model() */
402 		WARN(1, "Incorrect XDP memory type (%d) usage", mem->type);
403 		break;
404 	}
405 }
406 
407 void xdp_return_frame(struct xdp_frame *xdpf)
408 {
409 	__xdp_return(xdpf->data, &xdpf->mem, false, NULL);
410 }
411 EXPORT_SYMBOL_GPL(xdp_return_frame);
412 
413 void xdp_return_frame_rx_napi(struct xdp_frame *xdpf)
414 {
415 	__xdp_return(xdpf->data, &xdpf->mem, true, NULL);
416 }
417 EXPORT_SYMBOL_GPL(xdp_return_frame_rx_napi);
418 
419 /* XDP bulk APIs introduce a defer/flush mechanism to return
420  * pages belonging to the same xdp_mem_allocator object
421  * (identified via the mem.id field) in bulk to optimize
422  * I-cache and D-cache.
423  * The bulk queue size is set to 16 to be aligned to how
424  * XDP_REDIRECT bulking works. The bulk is flushed when
425  * it is full or when mem.id changes.
426  * xdp_frame_bulk is usually stored/allocated on the function
427  * call-stack to avoid locking penalties.
428  */
429 void xdp_flush_frame_bulk(struct xdp_frame_bulk *bq)
430 {
431 	struct xdp_mem_allocator *xa = bq->xa;
432 
433 	if (unlikely(!xa || !bq->count))
434 		return;
435 
436 	page_pool_put_page_bulk(xa->page_pool, bq->q, bq->count);
437 	/* bq->xa is not cleared to save lookup, if mem.id same in next bulk */
438 	bq->count = 0;
439 }
440 EXPORT_SYMBOL_GPL(xdp_flush_frame_bulk);
441 
442 /* Must be called with rcu_read_lock held */
443 void xdp_return_frame_bulk(struct xdp_frame *xdpf,
444 			   struct xdp_frame_bulk *bq)
445 {
446 	struct xdp_mem_info *mem = &xdpf->mem;
447 	struct xdp_mem_allocator *xa;
448 
449 	if (mem->type != MEM_TYPE_PAGE_POOL) {
450 		__xdp_return(xdpf->data, &xdpf->mem, false, NULL);
451 		return;
452 	}
453 
454 	xa = bq->xa;
455 	if (unlikely(!xa)) {
456 		xa = rhashtable_lookup(mem_id_ht, &mem->id, mem_id_rht_params);
457 		bq->count = 0;
458 		bq->xa = xa;
459 	}
460 
461 	if (bq->count == XDP_BULK_QUEUE_SIZE)
462 		xdp_flush_frame_bulk(bq);
463 
464 	if (unlikely(mem->id != xa->mem.id)) {
465 		xdp_flush_frame_bulk(bq);
466 		bq->xa = rhashtable_lookup(mem_id_ht, &mem->id, mem_id_rht_params);
467 	}
468 
469 	bq->q[bq->count++] = xdpf->data;
470 }
471 EXPORT_SYMBOL_GPL(xdp_return_frame_bulk);
472 
473 void xdp_return_buff(struct xdp_buff *xdp)
474 {
475 	__xdp_return(xdp->data, &xdp->rxq->mem, true, xdp);
476 }
477 
478 /* Only called for MEM_TYPE_PAGE_POOL see xdp.h */
479 void __xdp_release_frame(void *data, struct xdp_mem_info *mem)
480 {
481 	struct xdp_mem_allocator *xa;
482 	struct page *page;
483 
484 	rcu_read_lock();
485 	xa = rhashtable_lookup(mem_id_ht, &mem->id, mem_id_rht_params);
486 	page = virt_to_head_page(data);
487 	if (xa)
488 		page_pool_release_page(xa->page_pool, page);
489 	rcu_read_unlock();
490 }
491 EXPORT_SYMBOL_GPL(__xdp_release_frame);
492 
493 void xdp_attachment_setup(struct xdp_attachment_info *info,
494 			  struct netdev_bpf *bpf)
495 {
496 	if (info->prog)
497 		bpf_prog_put(info->prog);
498 	info->prog = bpf->prog;
499 	info->flags = bpf->flags;
500 }
501 EXPORT_SYMBOL_GPL(xdp_attachment_setup);
502 
503 struct xdp_frame *xdp_convert_zc_to_xdp_frame(struct xdp_buff *xdp)
504 {
505 	unsigned int metasize, totsize;
506 	void *addr, *data_to_copy;
507 	struct xdp_frame *xdpf;
508 	struct page *page;
509 
510 	/* Clone into a MEM_TYPE_PAGE_ORDER0 xdp_frame. */
511 	metasize = xdp_data_meta_unsupported(xdp) ? 0 :
512 		   xdp->data - xdp->data_meta;
513 	totsize = xdp->data_end - xdp->data + metasize;
514 
515 	if (sizeof(*xdpf) + totsize > PAGE_SIZE)
516 		return NULL;
517 
518 	page = dev_alloc_page();
519 	if (!page)
520 		return NULL;
521 
522 	addr = page_to_virt(page);
523 	xdpf = addr;
524 	memset(xdpf, 0, sizeof(*xdpf));
525 
526 	addr += sizeof(*xdpf);
527 	data_to_copy = metasize ? xdp->data_meta : xdp->data;
528 	memcpy(addr, data_to_copy, totsize);
529 
530 	xdpf->data = addr + metasize;
531 	xdpf->len = totsize - metasize;
532 	xdpf->headroom = 0;
533 	xdpf->metasize = metasize;
534 	xdpf->frame_sz = PAGE_SIZE;
535 	xdpf->mem.type = MEM_TYPE_PAGE_ORDER0;
536 
537 	xsk_buff_free(xdp);
538 	return xdpf;
539 }
540 EXPORT_SYMBOL_GPL(xdp_convert_zc_to_xdp_frame);
541 
542 /* Used by XDP_WARN macro, to avoid inlining WARN() in fast-path */
543 void xdp_warn(const char *msg, const char *func, const int line)
544 {
545 	WARN(1, "XDP_WARN: %s(line:%d): %s\n", func, line, msg);
546 };
547 EXPORT_SYMBOL_GPL(xdp_warn);
548 
549 int xdp_alloc_skb_bulk(void **skbs, int n_skb, gfp_t gfp)
550 {
551 	n_skb = kmem_cache_alloc_bulk(skbuff_head_cache, gfp,
552 				      n_skb, skbs);
553 	if (unlikely(!n_skb))
554 		return -ENOMEM;
555 
556 	return 0;
557 }
558 EXPORT_SYMBOL_GPL(xdp_alloc_skb_bulk);
559 
560 struct sk_buff *__xdp_build_skb_from_frame(struct xdp_frame *xdpf,
561 					   struct sk_buff *skb,
562 					   struct net_device *dev)
563 {
564 	unsigned int headroom, frame_size;
565 	void *hard_start;
566 
567 	/* Part of headroom was reserved to xdpf */
568 	headroom = sizeof(*xdpf) + xdpf->headroom;
569 
570 	/* Memory size backing xdp_frame data already have reserved
571 	 * room for build_skb to place skb_shared_info in tailroom.
572 	 */
573 	frame_size = xdpf->frame_sz;
574 
575 	hard_start = xdpf->data - headroom;
576 	skb = build_skb_around(skb, hard_start, frame_size);
577 	if (unlikely(!skb))
578 		return NULL;
579 
580 	skb_reserve(skb, headroom);
581 	__skb_put(skb, xdpf->len);
582 	if (xdpf->metasize)
583 		skb_metadata_set(skb, xdpf->metasize);
584 
585 	/* Essential SKB info: protocol and skb->dev */
586 	skb->protocol = eth_type_trans(skb, dev);
587 
588 	/* Optional SKB info, currently missing:
589 	 * - HW checksum info		(skb->ip_summed)
590 	 * - HW RX hash			(skb_set_hash)
591 	 * - RX ring dev queue index	(skb_record_rx_queue)
592 	 */
593 
594 	/* Until page_pool get SKB return path, release DMA here */
595 	xdp_release_frame(xdpf);
596 
597 	/* Allow SKB to reuse area used by xdp_frame */
598 	xdp_scrub_frame(xdpf);
599 
600 	return skb;
601 }
602 EXPORT_SYMBOL_GPL(__xdp_build_skb_from_frame);
603 
604 struct sk_buff *xdp_build_skb_from_frame(struct xdp_frame *xdpf,
605 					 struct net_device *dev)
606 {
607 	struct sk_buff *skb;
608 
609 	skb = kmem_cache_alloc(skbuff_head_cache, GFP_ATOMIC);
610 	if (unlikely(!skb))
611 		return NULL;
612 
613 	memset(skb, 0, offsetof(struct sk_buff, tail));
614 
615 	return __xdp_build_skb_from_frame(xdpf, skb, dev);
616 }
617 EXPORT_SYMBOL_GPL(xdp_build_skb_from_frame);
618 
619 struct xdp_frame *xdpf_clone(struct xdp_frame *xdpf)
620 {
621 	unsigned int headroom, totalsize;
622 	struct xdp_frame *nxdpf;
623 	struct page *page;
624 	void *addr;
625 
626 	headroom = xdpf->headroom + sizeof(*xdpf);
627 	totalsize = headroom + xdpf->len;
628 
629 	if (unlikely(totalsize > PAGE_SIZE))
630 		return NULL;
631 	page = dev_alloc_page();
632 	if (!page)
633 		return NULL;
634 	addr = page_to_virt(page);
635 
636 	memcpy(addr, xdpf, totalsize);
637 
638 	nxdpf = addr;
639 	nxdpf->data = addr + headroom;
640 	nxdpf->frame_sz = PAGE_SIZE;
641 	nxdpf->mem.type = MEM_TYPE_PAGE_ORDER0;
642 	nxdpf->mem.id = 0;
643 
644 	return nxdpf;
645 }
646