xref: /openbmc/linux/net/ipv4/udp_offload.c (revision 165f2d28)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  *	IPV4 GSO/GRO offload support
4  *	Linux INET implementation
5  *
6  *	UDPv4 GSO support
7  */
8 
9 #include <linux/skbuff.h>
10 #include <net/udp.h>
11 #include <net/protocol.h>
12 #include <net/inet_common.h>
13 
14 static struct sk_buff *__skb_udp_tunnel_segment(struct sk_buff *skb,
15 	netdev_features_t features,
16 	struct sk_buff *(*gso_inner_segment)(struct sk_buff *skb,
17 					     netdev_features_t features),
18 	__be16 new_protocol, bool is_ipv6)
19 {
20 	int tnl_hlen = skb_inner_mac_header(skb) - skb_transport_header(skb);
21 	bool remcsum, need_csum, offload_csum, gso_partial;
22 	struct sk_buff *segs = ERR_PTR(-EINVAL);
23 	struct udphdr *uh = udp_hdr(skb);
24 	u16 mac_offset = skb->mac_header;
25 	__be16 protocol = skb->protocol;
26 	u16 mac_len = skb->mac_len;
27 	int udp_offset, outer_hlen;
28 	__wsum partial;
29 	bool need_ipsec;
30 
31 	if (unlikely(!pskb_may_pull(skb, tnl_hlen)))
32 		goto out;
33 
34 	/* Adjust partial header checksum to negate old length.
35 	 * We cannot rely on the value contained in uh->len as it is
36 	 * possible that the actual value exceeds the boundaries of the
37 	 * 16 bit length field due to the header being added outside of an
38 	 * IP or IPv6 frame that was already limited to 64K - 1.
39 	 */
40 	if (skb_shinfo(skb)->gso_type & SKB_GSO_PARTIAL)
41 		partial = (__force __wsum)uh->len;
42 	else
43 		partial = (__force __wsum)htonl(skb->len);
44 	partial = csum_sub(csum_unfold(uh->check), partial);
45 
46 	/* setup inner skb. */
47 	skb->encapsulation = 0;
48 	SKB_GSO_CB(skb)->encap_level = 0;
49 	__skb_pull(skb, tnl_hlen);
50 	skb_reset_mac_header(skb);
51 	skb_set_network_header(skb, skb_inner_network_offset(skb));
52 	skb->mac_len = skb_inner_network_offset(skb);
53 	skb->protocol = new_protocol;
54 
55 	need_csum = !!(skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL_CSUM);
56 	skb->encap_hdr_csum = need_csum;
57 
58 	remcsum = !!(skb_shinfo(skb)->gso_type & SKB_GSO_TUNNEL_REMCSUM);
59 	skb->remcsum_offload = remcsum;
60 
61 	need_ipsec = skb_dst(skb) && dst_xfrm(skb_dst(skb));
62 	/* Try to offload checksum if possible */
63 	offload_csum = !!(need_csum &&
64 			  !need_ipsec &&
65 			  (skb->dev->features &
66 			   (is_ipv6 ? (NETIF_F_HW_CSUM | NETIF_F_IPV6_CSUM) :
67 				      (NETIF_F_HW_CSUM | NETIF_F_IP_CSUM))));
68 
69 	features &= skb->dev->hw_enc_features;
70 
71 	/* The only checksum offload we care about from here on out is the
72 	 * outer one so strip the existing checksum feature flags and
73 	 * instead set the flag based on our outer checksum offload value.
74 	 */
75 	if (remcsum) {
76 		features &= ~NETIF_F_CSUM_MASK;
77 		if (!need_csum || offload_csum)
78 			features |= NETIF_F_HW_CSUM;
79 	}
80 
81 	/* segment inner packet. */
82 	segs = gso_inner_segment(skb, features);
83 	if (IS_ERR_OR_NULL(segs)) {
84 		skb_gso_error_unwind(skb, protocol, tnl_hlen, mac_offset,
85 				     mac_len);
86 		goto out;
87 	}
88 
89 	gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL);
90 
91 	outer_hlen = skb_tnl_header_len(skb);
92 	udp_offset = outer_hlen - tnl_hlen;
93 	skb = segs;
94 	do {
95 		unsigned int len;
96 
97 		if (remcsum)
98 			skb->ip_summed = CHECKSUM_NONE;
99 
100 		/* Set up inner headers if we are offloading inner checksum */
101 		if (skb->ip_summed == CHECKSUM_PARTIAL) {
102 			skb_reset_inner_headers(skb);
103 			skb->encapsulation = 1;
104 		}
105 
106 		skb->mac_len = mac_len;
107 		skb->protocol = protocol;
108 
109 		__skb_push(skb, outer_hlen);
110 		skb_reset_mac_header(skb);
111 		skb_set_network_header(skb, mac_len);
112 		skb_set_transport_header(skb, udp_offset);
113 		len = skb->len - udp_offset;
114 		uh = udp_hdr(skb);
115 
116 		/* If we are only performing partial GSO the inner header
117 		 * will be using a length value equal to only one MSS sized
118 		 * segment instead of the entire frame.
119 		 */
120 		if (gso_partial && skb_is_gso(skb)) {
121 			uh->len = htons(skb_shinfo(skb)->gso_size +
122 					SKB_GSO_CB(skb)->data_offset +
123 					skb->head - (unsigned char *)uh);
124 		} else {
125 			uh->len = htons(len);
126 		}
127 
128 		if (!need_csum)
129 			continue;
130 
131 		uh->check = ~csum_fold(csum_add(partial,
132 				       (__force __wsum)htonl(len)));
133 
134 		if (skb->encapsulation || !offload_csum) {
135 			uh->check = gso_make_checksum(skb, ~uh->check);
136 			if (uh->check == 0)
137 				uh->check = CSUM_MANGLED_0;
138 		} else {
139 			skb->ip_summed = CHECKSUM_PARTIAL;
140 			skb->csum_start = skb_transport_header(skb) - skb->head;
141 			skb->csum_offset = offsetof(struct udphdr, check);
142 		}
143 	} while ((skb = skb->next));
144 out:
145 	return segs;
146 }
147 
148 struct sk_buff *skb_udp_tunnel_segment(struct sk_buff *skb,
149 				       netdev_features_t features,
150 				       bool is_ipv6)
151 {
152 	__be16 protocol = skb->protocol;
153 	const struct net_offload **offloads;
154 	const struct net_offload *ops;
155 	struct sk_buff *segs = ERR_PTR(-EINVAL);
156 	struct sk_buff *(*gso_inner_segment)(struct sk_buff *skb,
157 					     netdev_features_t features);
158 
159 	rcu_read_lock();
160 
161 	switch (skb->inner_protocol_type) {
162 	case ENCAP_TYPE_ETHER:
163 		protocol = skb->inner_protocol;
164 		gso_inner_segment = skb_mac_gso_segment;
165 		break;
166 	case ENCAP_TYPE_IPPROTO:
167 		offloads = is_ipv6 ? inet6_offloads : inet_offloads;
168 		ops = rcu_dereference(offloads[skb->inner_ipproto]);
169 		if (!ops || !ops->callbacks.gso_segment)
170 			goto out_unlock;
171 		gso_inner_segment = ops->callbacks.gso_segment;
172 		break;
173 	default:
174 		goto out_unlock;
175 	}
176 
177 	segs = __skb_udp_tunnel_segment(skb, features, gso_inner_segment,
178 					protocol, is_ipv6);
179 
180 out_unlock:
181 	rcu_read_unlock();
182 
183 	return segs;
184 }
185 EXPORT_SYMBOL(skb_udp_tunnel_segment);
186 
187 static struct sk_buff *__udp_gso_segment_list(struct sk_buff *skb,
188 					      netdev_features_t features)
189 {
190 	unsigned int mss = skb_shinfo(skb)->gso_size;
191 
192 	skb = skb_segment_list(skb, features, skb_mac_header_len(skb));
193 	if (IS_ERR(skb))
194 		return skb;
195 
196 	udp_hdr(skb)->len = htons(sizeof(struct udphdr) + mss);
197 
198 	return skb;
199 }
200 
201 struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
202 				  netdev_features_t features)
203 {
204 	struct sock *sk = gso_skb->sk;
205 	unsigned int sum_truesize = 0;
206 	struct sk_buff *segs, *seg;
207 	struct udphdr *uh;
208 	unsigned int mss;
209 	bool copy_dtor;
210 	__sum16 check;
211 	__be16 newlen;
212 
213 	if (skb_shinfo(gso_skb)->gso_type & SKB_GSO_FRAGLIST)
214 		return __udp_gso_segment_list(gso_skb, features);
215 
216 	mss = skb_shinfo(gso_skb)->gso_size;
217 	if (gso_skb->len <= sizeof(*uh) + mss)
218 		return ERR_PTR(-EINVAL);
219 
220 	skb_pull(gso_skb, sizeof(*uh));
221 
222 	/* clear destructor to avoid skb_segment assigning it to tail */
223 	copy_dtor = gso_skb->destructor == sock_wfree;
224 	if (copy_dtor)
225 		gso_skb->destructor = NULL;
226 
227 	segs = skb_segment(gso_skb, features);
228 	if (IS_ERR_OR_NULL(segs)) {
229 		if (copy_dtor)
230 			gso_skb->destructor = sock_wfree;
231 		return segs;
232 	}
233 
234 	/* GSO partial and frag_list segmentation only requires splitting
235 	 * the frame into an MSS multiple and possibly a remainder, both
236 	 * cases return a GSO skb. So update the mss now.
237 	 */
238 	if (skb_is_gso(segs))
239 		mss *= skb_shinfo(segs)->gso_segs;
240 
241 	seg = segs;
242 	uh = udp_hdr(seg);
243 
244 	/* preserve TX timestamp flags and TS key for first segment */
245 	skb_shinfo(seg)->tskey = skb_shinfo(gso_skb)->tskey;
246 	skb_shinfo(seg)->tx_flags |=
247 			(skb_shinfo(gso_skb)->tx_flags & SKBTX_ANY_TSTAMP);
248 
249 	/* compute checksum adjustment based on old length versus new */
250 	newlen = htons(sizeof(*uh) + mss);
251 	check = csum16_add(csum16_sub(uh->check, uh->len), newlen);
252 
253 	for (;;) {
254 		if (copy_dtor) {
255 			seg->destructor = sock_wfree;
256 			seg->sk = sk;
257 			sum_truesize += seg->truesize;
258 		}
259 
260 		if (!seg->next)
261 			break;
262 
263 		uh->len = newlen;
264 		uh->check = check;
265 
266 		if (seg->ip_summed == CHECKSUM_PARTIAL)
267 			gso_reset_checksum(seg, ~check);
268 		else
269 			uh->check = gso_make_checksum(seg, ~check) ? :
270 				    CSUM_MANGLED_0;
271 
272 		seg = seg->next;
273 		uh = udp_hdr(seg);
274 	}
275 
276 	/* last packet can be partial gso_size, account for that in checksum */
277 	newlen = htons(skb_tail_pointer(seg) - skb_transport_header(seg) +
278 		       seg->data_len);
279 	check = csum16_add(csum16_sub(uh->check, uh->len), newlen);
280 
281 	uh->len = newlen;
282 	uh->check = check;
283 
284 	if (seg->ip_summed == CHECKSUM_PARTIAL)
285 		gso_reset_checksum(seg, ~check);
286 	else
287 		uh->check = gso_make_checksum(seg, ~check) ? : CSUM_MANGLED_0;
288 
289 	/* update refcount for the packet */
290 	if (copy_dtor) {
291 		int delta = sum_truesize - gso_skb->truesize;
292 
293 		/* In some pathological cases, delta can be negative.
294 		 * We need to either use refcount_add() or refcount_sub_and_test()
295 		 */
296 		if (likely(delta >= 0))
297 			refcount_add(delta, &sk->sk_wmem_alloc);
298 		else
299 			WARN_ON_ONCE(refcount_sub_and_test(-delta, &sk->sk_wmem_alloc));
300 	}
301 	return segs;
302 }
303 EXPORT_SYMBOL_GPL(__udp_gso_segment);
304 
305 static struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb,
306 					 netdev_features_t features)
307 {
308 	struct sk_buff *segs = ERR_PTR(-EINVAL);
309 	unsigned int mss;
310 	__wsum csum;
311 	struct udphdr *uh;
312 	struct iphdr *iph;
313 
314 	if (skb->encapsulation &&
315 	    (skb_shinfo(skb)->gso_type &
316 	     (SKB_GSO_UDP_TUNNEL|SKB_GSO_UDP_TUNNEL_CSUM))) {
317 		segs = skb_udp_tunnel_segment(skb, features, false);
318 		goto out;
319 	}
320 
321 	if (!(skb_shinfo(skb)->gso_type & (SKB_GSO_UDP | SKB_GSO_UDP_L4)))
322 		goto out;
323 
324 	if (!pskb_may_pull(skb, sizeof(struct udphdr)))
325 		goto out;
326 
327 	if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4)
328 		return __udp_gso_segment(skb, features);
329 
330 	mss = skb_shinfo(skb)->gso_size;
331 	if (unlikely(skb->len <= mss))
332 		goto out;
333 
334 	/* Do software UFO. Complete and fill in the UDP checksum as
335 	 * HW cannot do checksum of UDP packets sent as multiple
336 	 * IP fragments.
337 	 */
338 
339 	uh = udp_hdr(skb);
340 	iph = ip_hdr(skb);
341 
342 	uh->check = 0;
343 	csum = skb_checksum(skb, 0, skb->len, 0);
344 	uh->check = udp_v4_check(skb->len, iph->saddr, iph->daddr, csum);
345 	if (uh->check == 0)
346 		uh->check = CSUM_MANGLED_0;
347 
348 	skb->ip_summed = CHECKSUM_UNNECESSARY;
349 
350 	/* If there is no outer header we can fake a checksum offload
351 	 * due to the fact that we have already done the checksum in
352 	 * software prior to segmenting the frame.
353 	 */
354 	if (!skb->encap_hdr_csum)
355 		features |= NETIF_F_HW_CSUM;
356 
357 	/* Fragment the skb. IP headers of the fragments are updated in
358 	 * inet_gso_segment()
359 	 */
360 	segs = skb_segment(skb, features);
361 out:
362 	return segs;
363 }
364 
365 #define UDP_GRO_CNT_MAX 64
366 static struct sk_buff *udp_gro_receive_segment(struct list_head *head,
367 					       struct sk_buff *skb)
368 {
369 	struct udphdr *uh = udp_hdr(skb);
370 	struct sk_buff *pp = NULL;
371 	struct udphdr *uh2;
372 	struct sk_buff *p;
373 	unsigned int ulen;
374 	int ret = 0;
375 
376 	/* requires non zero csum, for symmetry with GSO */
377 	if (!uh->check) {
378 		NAPI_GRO_CB(skb)->flush = 1;
379 		return NULL;
380 	}
381 
382 	/* Do not deal with padded or malicious packets, sorry ! */
383 	ulen = ntohs(uh->len);
384 	if (ulen <= sizeof(*uh) || ulen != skb_gro_len(skb)) {
385 		NAPI_GRO_CB(skb)->flush = 1;
386 		return NULL;
387 	}
388 	/* pull encapsulating udp header */
389 	skb_gro_pull(skb, sizeof(struct udphdr));
390 
391 	list_for_each_entry(p, head, list) {
392 		if (!NAPI_GRO_CB(p)->same_flow)
393 			continue;
394 
395 		uh2 = udp_hdr(p);
396 
397 		/* Match ports only, as csum is always non zero */
398 		if ((*(u32 *)&uh->source != *(u32 *)&uh2->source)) {
399 			NAPI_GRO_CB(p)->same_flow = 0;
400 			continue;
401 		}
402 
403 		if (NAPI_GRO_CB(skb)->is_flist != NAPI_GRO_CB(p)->is_flist) {
404 			NAPI_GRO_CB(skb)->flush = 1;
405 			return p;
406 		}
407 
408 		/* Terminate the flow on len mismatch or if it grow "too much".
409 		 * Under small packet flood GRO count could elsewhere grow a lot
410 		 * leading to excessive truesize values.
411 		 * On len mismatch merge the first packet shorter than gso_size,
412 		 * otherwise complete the GRO packet.
413 		 */
414 		if (ulen > ntohs(uh2->len)) {
415 			pp = p;
416 		} else {
417 			if (NAPI_GRO_CB(skb)->is_flist) {
418 				if (!pskb_may_pull(skb, skb_gro_offset(skb))) {
419 					NAPI_GRO_CB(skb)->flush = 1;
420 					return NULL;
421 				}
422 				if ((skb->ip_summed != p->ip_summed) ||
423 				    (skb->csum_level != p->csum_level)) {
424 					NAPI_GRO_CB(skb)->flush = 1;
425 					return NULL;
426 				}
427 				ret = skb_gro_receive_list(p, skb);
428 			} else {
429 				skb_gro_postpull_rcsum(skb, uh,
430 						       sizeof(struct udphdr));
431 
432 				ret = skb_gro_receive(p, skb);
433 			}
434 		}
435 
436 		if (ret || ulen != ntohs(uh2->len) ||
437 		    NAPI_GRO_CB(p)->count >= UDP_GRO_CNT_MAX)
438 			pp = p;
439 
440 		return pp;
441 	}
442 
443 	/* mismatch, but we never need to flush */
444 	return NULL;
445 }
446 
447 struct sk_buff *udp_gro_receive(struct list_head *head, struct sk_buff *skb,
448 				struct udphdr *uh, struct sock *sk)
449 {
450 	struct sk_buff *pp = NULL;
451 	struct sk_buff *p;
452 	struct udphdr *uh2;
453 	unsigned int off = skb_gro_offset(skb);
454 	int flush = 1;
455 
456 	NAPI_GRO_CB(skb)->is_flist = 0;
457 	if (skb->dev->features & NETIF_F_GRO_FRAGLIST)
458 		NAPI_GRO_CB(skb)->is_flist = sk ? !udp_sk(sk)->gro_enabled: 1;
459 
460 	if ((sk && udp_sk(sk)->gro_enabled) || NAPI_GRO_CB(skb)->is_flist) {
461 		pp = call_gro_receive(udp_gro_receive_segment, head, skb);
462 		return pp;
463 	}
464 
465 	if (!sk || NAPI_GRO_CB(skb)->encap_mark ||
466 	    (skb->ip_summed != CHECKSUM_PARTIAL &&
467 	     NAPI_GRO_CB(skb)->csum_cnt == 0 &&
468 	     !NAPI_GRO_CB(skb)->csum_valid) ||
469 	    !udp_sk(sk)->gro_receive)
470 		goto out;
471 
472 	/* mark that this skb passed once through the tunnel gro layer */
473 	NAPI_GRO_CB(skb)->encap_mark = 1;
474 
475 	flush = 0;
476 
477 	list_for_each_entry(p, head, list) {
478 		if (!NAPI_GRO_CB(p)->same_flow)
479 			continue;
480 
481 		uh2 = (struct udphdr   *)(p->data + off);
482 
483 		/* Match ports and either checksums are either both zero
484 		 * or nonzero.
485 		 */
486 		if ((*(u32 *)&uh->source != *(u32 *)&uh2->source) ||
487 		    (!uh->check ^ !uh2->check)) {
488 			NAPI_GRO_CB(p)->same_flow = 0;
489 			continue;
490 		}
491 	}
492 
493 	skb_gro_pull(skb, sizeof(struct udphdr)); /* pull encapsulating udp header */
494 	skb_gro_postpull_rcsum(skb, uh, sizeof(struct udphdr));
495 	pp = call_gro_receive_sk(udp_sk(sk)->gro_receive, sk, head, skb);
496 
497 out:
498 	skb_gro_flush_final(skb, pp, flush);
499 	return pp;
500 }
501 EXPORT_SYMBOL(udp_gro_receive);
502 
503 INDIRECT_CALLABLE_SCOPE
504 struct sk_buff *udp4_gro_receive(struct list_head *head, struct sk_buff *skb)
505 {
506 	struct udphdr *uh = udp_gro_udphdr(skb);
507 	struct sk_buff *pp;
508 	struct sock *sk;
509 
510 	if (unlikely(!uh))
511 		goto flush;
512 
513 	/* Don't bother verifying checksum if we're going to flush anyway. */
514 	if (NAPI_GRO_CB(skb)->flush)
515 		goto skip;
516 
517 	if (skb_gro_checksum_validate_zero_check(skb, IPPROTO_UDP, uh->check,
518 						 inet_gro_compute_pseudo))
519 		goto flush;
520 	else if (uh->check)
521 		skb_gro_checksum_try_convert(skb, IPPROTO_UDP,
522 					     inet_gro_compute_pseudo);
523 skip:
524 	NAPI_GRO_CB(skb)->is_ipv6 = 0;
525 	rcu_read_lock();
526 	sk = static_branch_unlikely(&udp_encap_needed_key) ? udp4_lib_lookup_skb(skb, uh->source, uh->dest) : NULL;
527 	pp = udp_gro_receive(head, skb, uh, sk);
528 	rcu_read_unlock();
529 	return pp;
530 
531 flush:
532 	NAPI_GRO_CB(skb)->flush = 1;
533 	return NULL;
534 }
535 
536 static int udp_gro_complete_segment(struct sk_buff *skb)
537 {
538 	struct udphdr *uh = udp_hdr(skb);
539 
540 	skb->csum_start = (unsigned char *)uh - skb->head;
541 	skb->csum_offset = offsetof(struct udphdr, check);
542 	skb->ip_summed = CHECKSUM_PARTIAL;
543 
544 	skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
545 	skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_L4;
546 	return 0;
547 }
548 
549 int udp_gro_complete(struct sk_buff *skb, int nhoff,
550 		     udp_lookup_t lookup)
551 {
552 	__be16 newlen = htons(skb->len - nhoff);
553 	struct udphdr *uh = (struct udphdr *)(skb->data + nhoff);
554 	int err = -ENOSYS;
555 	struct sock *sk;
556 
557 	uh->len = newlen;
558 
559 	rcu_read_lock();
560 	sk = INDIRECT_CALL_INET(lookup, udp6_lib_lookup_skb,
561 				udp4_lib_lookup_skb, skb, uh->source, uh->dest);
562 	if (sk && udp_sk(sk)->gro_complete) {
563 		skb_shinfo(skb)->gso_type = uh->check ? SKB_GSO_UDP_TUNNEL_CSUM
564 					: SKB_GSO_UDP_TUNNEL;
565 
566 		/* Set encapsulation before calling into inner gro_complete()
567 		 * functions to make them set up the inner offsets.
568 		 */
569 		skb->encapsulation = 1;
570 		err = udp_sk(sk)->gro_complete(sk, skb,
571 				nhoff + sizeof(struct udphdr));
572 	} else {
573 		err = udp_gro_complete_segment(skb);
574 	}
575 	rcu_read_unlock();
576 
577 	if (skb->remcsum_offload)
578 		skb_shinfo(skb)->gso_type |= SKB_GSO_TUNNEL_REMCSUM;
579 
580 	return err;
581 }
582 EXPORT_SYMBOL(udp_gro_complete);
583 
584 INDIRECT_CALLABLE_SCOPE int udp4_gro_complete(struct sk_buff *skb, int nhoff)
585 {
586 	const struct iphdr *iph = ip_hdr(skb);
587 	struct udphdr *uh = (struct udphdr *)(skb->data + nhoff);
588 
589 	if (NAPI_GRO_CB(skb)->is_flist) {
590 		uh->len = htons(skb->len - nhoff);
591 
592 		skb_shinfo(skb)->gso_type |= (SKB_GSO_FRAGLIST|SKB_GSO_UDP_L4);
593 		skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
594 
595 		if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
596 			if (skb->csum_level < SKB_MAX_CSUM_LEVEL)
597 				skb->csum_level++;
598 		} else {
599 			skb->ip_summed = CHECKSUM_UNNECESSARY;
600 			skb->csum_level = 0;
601 		}
602 
603 		return 0;
604 	}
605 
606 	if (uh->check)
607 		uh->check = ~udp_v4_check(skb->len - nhoff, iph->saddr,
608 					  iph->daddr, 0);
609 
610 	return udp_gro_complete(skb, nhoff, udp4_lib_lookup_skb);
611 }
612 
613 static const struct net_offload udpv4_offload = {
614 	.callbacks = {
615 		.gso_segment = udp4_ufo_fragment,
616 		.gro_receive  =	udp4_gro_receive,
617 		.gro_complete =	udp4_gro_complete,
618 	},
619 };
620 
621 int __init udpv4_offload_init(void)
622 {
623 	return inet_add_offload(&udpv4_offload, IPPROTO_UDP);
624 }
625