net/ipv4/udp_offload.c

   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_set_transport_header(skb, skb_inner_transport_offset(skb));
  53         skb->mac_len = skb_inner_network_offset(skb);
  54         skb->protocol = new_protocol;
  55
  56         need_csum = !!(skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL_CSUM);
  57         skb->encap_hdr_csum = need_csum;
  58
  59         remcsum = !!(skb_shinfo(skb)->gso_type & SKB_GSO_TUNNEL_REMCSUM);
  60         skb->remcsum_offload = remcsum;
  61
  62         need_ipsec = skb_dst(skb) && dst_xfrm(skb_dst(skb));
  63         /* Try to offload checksum if possible */
  64         offload_csum = !!(need_csum &&
  65                           !need_ipsec &&
  66                           (skb->dev->features &
  67                            (is_ipv6 ? (NETIF_F_HW_CSUM | NETIF_F_IPV6_CSUM) :
  68                                       (NETIF_F_HW_CSUM | NETIF_F_IP_CSUM))));
  69
  70         features &= skb->dev->hw_enc_features;
  71         /* CRC checksum can't be handled by HW when it's a UDP tunneling packet. */
  72         features &= ~NETIF_F_SCTP_CRC;
  73
  74         /* The only checksum offload we care about from here on out is the
  75          * outer one so strip the existing checksum feature flags and
  76          * instead set the flag based on our outer checksum offload value.
  77          */
  78         if (remcsum) {
  79                 features &= ~NETIF_F_CSUM_MASK;
  80                 if (!need_csum || offload_csum)
  81                         features |= NETIF_F_HW_CSUM;
  82         }
  83
  84         /* segment inner packet. */
  85         segs = gso_inner_segment(skb, features);
  86         if (IS_ERR_OR_NULL(segs)) {
  87                 skb_gso_error_unwind(skb, protocol, tnl_hlen, mac_offset,
  88                                      mac_len);
  89                 goto out;
  90         }
  91
  92         gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL);
  93
  94         outer_hlen = skb_tnl_header_len(skb);
  95         udp_offset = outer_hlen - tnl_hlen;
  96         skb = segs;
  97         do {
  98                 unsigned int len;
  99
 100                 if (remcsum)
 101                         skb->ip_summed = CHECKSUM_NONE;
 102
 103                 /* Set up inner headers if we are offloading inner checksum */
 104                 if (skb->ip_summed == CHECKSUM_PARTIAL) {
 105                         skb_reset_inner_headers(skb);
 106                         skb->encapsulation = 1;
 107                 }
 108
 109                 skb->mac_len = mac_len;
 110                 skb->protocol = protocol;
 111
 112                 __skb_push(skb, outer_hlen);
 113                 skb_reset_mac_header(skb);
 114                 skb_set_network_header(skb, mac_len);
 115                 skb_set_transport_header(skb, udp_offset);
 116                 len = skb->len - udp_offset;
 117                 uh = udp_hdr(skb);
 118
 119                 /* If we are only performing partial GSO the inner header
 120                  * will be using a length value equal to only one MSS sized
 121                  * segment instead of the entire frame.
 122                  */
 123                 if (gso_partial && skb_is_gso(skb)) {
 124                         uh->len = htons(skb_shinfo(skb)->gso_size +
 125                                         SKB_GSO_CB(skb)->data_offset +
 126                                         skb->head - (unsigned char *)uh);
 127                 } else {
 128                         uh->len = htons(len);
 129                 }
 130
 131                 if (!need_csum)
 132                         continue;
 133
 134                 uh->check = ~csum_fold(csum_add(partial,
 135                                        (__force __wsum)htonl(len)));
 136
 137                 if (skb->encapsulation || !offload_csum) {
 138                         uh->check = gso_make_checksum(skb, ~uh->check);
 139                         if (uh->check == 0)
 140                                 uh->check = CSUM_MANGLED_0;
 141                 } else {
 142                         skb->ip_summed = CHECKSUM_PARTIAL;
 143                         skb->csum_start = skb_transport_header(skb) - skb->head;
 144                         skb->csum_offset = offsetof(struct udphdr, check);
 145                 }
 146         } while ((skb = skb->next));
 147 out:
 148         return segs;
 149 }
 150
 151 struct sk_buff *skb_udp_tunnel_segment(struct sk_buff *skb,
 152                                        netdev_features_t features,
 153                                        bool is_ipv6)
 154 {
 155         __be16 protocol = skb->protocol;
 156         const struct net_offload **offloads;
 157         const struct net_offload *ops;
 158         struct sk_buff *segs = ERR_PTR(-EINVAL);
 159         struct sk_buff *(*gso_inner_segment)(struct sk_buff *skb,
 160                                              netdev_features_t features);
 161
 162         rcu_read_lock();
 163
 164         switch (skb->inner_protocol_type) {
 165         case ENCAP_TYPE_ETHER:
 166                 protocol = skb->inner_protocol;
 167                 gso_inner_segment = skb_mac_gso_segment;
 168                 break;
 169         case ENCAP_TYPE_IPPROTO:
 170                 offloads = is_ipv6 ? inet6_offloads : inet_offloads;
 171                 ops = rcu_dereference(offloads[skb->inner_ipproto]);
 172                 if (!ops || !ops->callbacks.gso_segment)
 173                         goto out_unlock;
 174                 gso_inner_segment = ops->callbacks.gso_segment;
 175                 break;
 176         default:
 177                 goto out_unlock;
 178         }
 179
 180         segs = __skb_udp_tunnel_segment(skb, features, gso_inner_segment,
 181                                         protocol, is_ipv6);
 182
 183 out_unlock:
 184         rcu_read_unlock();
 185
 186         return segs;
 187 }
 188 EXPORT_SYMBOL(skb_udp_tunnel_segment);
 189
 190 static struct sk_buff *__udp_gso_segment_list(struct sk_buff *skb,
 191                                               netdev_features_t features)
 192 {
 193         unsigned int mss = skb_shinfo(skb)->gso_size;
 194
 195         skb = skb_segment_list(skb, features, skb_mac_header_len(skb));
 196         if (IS_ERR(skb))
 197                 return skb;
 198
 199         udp_hdr(skb)->len = htons(sizeof(struct udphdr) + mss);
 200
 201         return skb;
 202 }
 203
 204 struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
 205                                   netdev_features_t features)
 206 {
 207         struct sock *sk = gso_skb->sk;
 208         unsigned int sum_truesize = 0;
 209         struct sk_buff *segs, *seg;
 210         struct udphdr *uh;
 211         unsigned int mss;
 212         bool copy_dtor;
 213         __sum16 check;
 214         __be16 newlen;
 215
 216         if (skb_shinfo(gso_skb)->gso_type & SKB_GSO_FRAGLIST)
 217                 return __udp_gso_segment_list(gso_skb, features);
 218
 219         mss = skb_shinfo(gso_skb)->gso_size;
 220         if (gso_skb->len <= sizeof(*uh) + mss)
 221                 return ERR_PTR(-EINVAL);
 222
 223         skb_pull(gso_skb, sizeof(*uh));
 224
 225         /* clear destructor to avoid skb_segment assigning it to tail */
 226         copy_dtor = gso_skb->destructor == sock_wfree;
 227         if (copy_dtor)
 228                 gso_skb->destructor = NULL;
 229
 230         segs = skb_segment(gso_skb, features);
 231         if (IS_ERR_OR_NULL(segs)) {
 232                 if (copy_dtor)
 233                         gso_skb->destructor = sock_wfree;
 234                 return segs;
 235         }
 236
 237         /* GSO partial and frag_list segmentation only requires splitting
 238          * the frame into an MSS multiple and possibly a remainder, both
 239          * cases return a GSO skb. So update the mss now.
 240          */
 241         if (skb_is_gso(segs))
 242                 mss *= skb_shinfo(segs)->gso_segs;
 243
 244         seg = segs;
 245         uh = udp_hdr(seg);
 246
 247         /* preserve TX timestamp flags and TS key for first segment */
 248         skb_shinfo(seg)->tskey = skb_shinfo(gso_skb)->tskey;
 249         skb_shinfo(seg)->tx_flags |=
 250                         (skb_shinfo(gso_skb)->tx_flags & SKBTX_ANY_TSTAMP);
 251
 252         /* compute checksum adjustment based on old length versus new */
 253         newlen = htons(sizeof(*uh) + mss);
 254         check = csum16_add(csum16_sub(uh->check, uh->len), newlen);
 255
 256         for (;;) {
 257                 if (copy_dtor) {
 258                         seg->destructor = sock_wfree;
 259                         seg->sk = sk;
 260                         sum_truesize += seg->truesize;
 261                 }
 262
 263                 if (!seg->next)
 264                         break;
 265
 266                 uh->len = newlen;
 267                 uh->check = check;
 268
 269                 if (seg->ip_summed == CHECKSUM_PARTIAL)
 270                         gso_reset_checksum(seg, ~check);
 271                 else
 272                         uh->check = gso_make_checksum(seg, ~check) ? :
 273                                     CSUM_MANGLED_0;
 274
 275                 seg = seg->next;
 276                 uh = udp_hdr(seg);
 277         }
 278
 279         /* last packet can be partial gso_size, account for that in checksum */
 280         newlen = htons(skb_tail_pointer(seg) - skb_transport_header(seg) +
 281                        seg->data_len);
 282         check = csum16_add(csum16_sub(uh->check, uh->len), newlen);
 283
 284         uh->len = newlen;
 285         uh->check = check;
 286
 287         if (seg->ip_summed == CHECKSUM_PARTIAL)
 288                 gso_reset_checksum(seg, ~check);
 289         else
 290                 uh->check = gso_make_checksum(seg, ~check) ? : CSUM_MANGLED_0;
 291
 292         /* update refcount for the packet */
 293         if (copy_dtor) {
 294                 int delta = sum_truesize - gso_skb->truesize;
 295
 296                 /* In some pathological cases, delta can be negative.
 297                  * We need to either use refcount_add() or refcount_sub_and_test()
 298                  */
 299                 if (likely(delta >= 0))
 300                         refcount_add(delta, &sk->sk_wmem_alloc);
 301                 else
 302                         WARN_ON_ONCE(refcount_sub_and_test(-delta, &sk->sk_wmem_alloc));
 303         }
 304         return segs;
 305 }
 306 EXPORT_SYMBOL_GPL(__udp_gso_segment);
 307
 308 static struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb,
 309                                          netdev_features_t features)
 310 {
 311         struct sk_buff *segs = ERR_PTR(-EINVAL);
 312         unsigned int mss;
 313         __wsum csum;
 314         struct udphdr *uh;
 315         struct iphdr *iph;
 316
 317         if (skb->encapsulation &&
 318             (skb_shinfo(skb)->gso_type &
 319              (SKB_GSO_UDP_TUNNEL|SKB_GSO_UDP_TUNNEL_CSUM))) {
 320                 segs = skb_udp_tunnel_segment(skb, features, false);
 321                 goto out;
 322         }
 323
 324         if (!(skb_shinfo(skb)->gso_type & (SKB_GSO_UDP | SKB_GSO_UDP_L4)))
 325                 goto out;
 326
 327         if (!pskb_may_pull(skb, sizeof(struct udphdr)))
 328                 goto out;
 329
 330         if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4)
 331                 return __udp_gso_segment(skb, features);
 332
 333         mss = skb_shinfo(skb)->gso_size;
 334         if (unlikely(skb->len <= mss))
 335                 goto out;
 336
 337         /* Do software UFO. Complete and fill in the UDP checksum as
 338          * HW cannot do checksum of UDP packets sent as multiple
 339          * IP fragments.
 340          */
 341
 342         uh = udp_hdr(skb);
 343         iph = ip_hdr(skb);
 344
 345         uh->check = 0;
 346         csum = skb_checksum(skb, 0, skb->len, 0);
 347         uh->check = udp_v4_check(skb->len, iph->saddr, iph->daddr, csum);
 348         if (uh->check == 0)
 349                 uh->check = CSUM_MANGLED_0;
 350
 351         skb->ip_summed = CHECKSUM_UNNECESSARY;
 352
 353         /* If there is no outer header we can fake a checksum offload
 354          * due to the fact that we have already done the checksum in
 355          * software prior to segmenting the frame.
 356          */
 357         if (!skb->encap_hdr_csum)
 358                 features |= NETIF_F_HW_CSUM;
 359
 360         /* Fragment the skb. IP headers of the fragments are updated in
 361          * inet_gso_segment()
 362          */
 363         segs = skb_segment(skb, features);
 364 out:
 365         return segs;
 366 }
 367
 368 #define UDP_GRO_CNT_MAX 64
 369 static struct sk_buff *udp_gro_receive_segment(struct list_head *head,
 370                                                struct sk_buff *skb)
 371 {
 372         struct udphdr *uh = udp_gro_udphdr(skb);
 373         struct sk_buff *pp = NULL;
 374         struct udphdr *uh2;
 375         struct sk_buff *p;
 376         unsigned int ulen;
 377         int ret = 0;
 378
 379         /* requires non zero csum, for symmetry with GSO */
 380         if (!uh->check) {
 381                 NAPI_GRO_CB(skb)->flush = 1;
 382                 return NULL;
 383         }
 384
 385         /* Do not deal with padded or malicious packets, sorry ! */
 386         ulen = ntohs(uh->len);
 387         if (ulen <= sizeof(*uh) || ulen != skb_gro_len(skb)) {
 388                 NAPI_GRO_CB(skb)->flush = 1;
 389                 return NULL;
 390         }
 391         /* pull encapsulating udp header */
 392         skb_gro_pull(skb, sizeof(struct udphdr));
 393
 394         list_for_each_entry(p, head, list) {
 395                 if (!NAPI_GRO_CB(p)->same_flow)
 396                         continue;
 397
 398                 uh2 = udp_hdr(p);
 399
 400                 /* Match ports only, as csum is always non zero */
 401                 if ((*(u32 *)&uh->source != *(u32 *)&uh2->source)) {
 402                         NAPI_GRO_CB(p)->same_flow = 0;
 403                         continue;
 404                 }
 405
 406                 if (NAPI_GRO_CB(skb)->is_flist != NAPI_GRO_CB(p)->is_flist) {
 407                         NAPI_GRO_CB(skb)->flush = 1;
 408                         return p;
 409                 }
 410
 411                 /* Terminate the flow on len mismatch or if it grow "too much".
 412                  * Under small packet flood GRO count could elsewhere grow a lot
 413                  * leading to excessive truesize values.
 414                  * On len mismatch merge the first packet shorter than gso_size,
 415                  * otherwise complete the GRO packet.
 416                  */
 417                 if (ulen > ntohs(uh2->len)) {
 418                         pp = p;
 419                 } else {
 420                         if (NAPI_GRO_CB(skb)->is_flist) {
 421                                 if (!pskb_may_pull(skb, skb_gro_offset(skb))) {
 422                                         NAPI_GRO_CB(skb)->flush = 1;
 423                                         return NULL;
 424                                 }
 425                                 if ((skb->ip_summed != p->ip_summed) ||
 426                                     (skb->csum_level != p->csum_level)) {
 427                                         NAPI_GRO_CB(skb)->flush = 1;
 428                                         return NULL;
 429                                 }
 430                                 ret = skb_gro_receive_list(p, skb);
 431                         } else {
 432                                 skb_gro_postpull_rcsum(skb, uh,
 433                                                        sizeof(struct udphdr));
 434
 435                                 ret = skb_gro_receive(p, skb);
 436                         }
 437                 }
 438
 439                 if (ret || ulen != ntohs(uh2->len) ||
 440                     NAPI_GRO_CB(p)->count >= UDP_GRO_CNT_MAX)
 441                         pp = p;
 442
 443                 return pp;
 444         }
 445
 446         /* mismatch, but we never need to flush */
 447         return NULL;
 448 }
 449
 450 struct sk_buff *udp_gro_receive(struct list_head *head, struct sk_buff *skb,
 451                                 struct udphdr *uh, struct sock *sk)
 452 {
 453         struct sk_buff *pp = NULL;
 454         struct sk_buff *p;
 455         struct udphdr *uh2;
 456         unsigned int off = skb_gro_offset(skb);
 457         int flush = 1;
 458
 459         NAPI_GRO_CB(skb)->is_flist = 0;
 460         if (skb->dev->features & NETIF_F_GRO_FRAGLIST)
 461                 NAPI_GRO_CB(skb)->is_flist = sk ? !udp_sk(sk)->gro_enabled: 1;
 462
 463         if ((sk && udp_sk(sk)->gro_enabled) || NAPI_GRO_CB(skb)->is_flist) {
 464                 pp = call_gro_receive(udp_gro_receive_segment, head, skb);
 465                 return pp;
 466         }
 467
 468         if (!sk || NAPI_GRO_CB(skb)->encap_mark ||
 469             (skb->ip_summed != CHECKSUM_PARTIAL &&
 470              NAPI_GRO_CB(skb)->csum_cnt == 0 &&
 471              !NAPI_GRO_CB(skb)->csum_valid) ||
 472             !udp_sk(sk)->gro_receive)
 473                 goto out;
 474
 475         /* mark that this skb passed once through the tunnel gro layer */
 476         NAPI_GRO_CB(skb)->encap_mark = 1;
 477
 478         flush = 0;
 479
 480         list_for_each_entry(p, head, list) {
 481                 if (!NAPI_GRO_CB(p)->same_flow)
 482                         continue;
 483
 484                 uh2 = (struct udphdr   *)(p->data + off);
 485
 486                 /* Match ports and either checksums are either both zero
 487                  * or nonzero.
 488                  */
 489                 if ((*(u32 *)&uh->source != *(u32 *)&uh2->source) ||
 490                     (!uh->check ^ !uh2->check)) {
 491                         NAPI_GRO_CB(p)->same_flow = 0;
 492                         continue;
 493                 }
 494         }
 495
 496         skb_gro_pull(skb, sizeof(struct udphdr)); /* pull encapsulating udp header */
 497         skb_gro_postpull_rcsum(skb, uh, sizeof(struct udphdr));
 498         pp = call_gro_receive_sk(udp_sk(sk)->gro_receive, sk, head, skb);
 499
 500 out:
 501         skb_gro_flush_final(skb, pp, flush);
 502         return pp;
 503 }
 504 EXPORT_SYMBOL(udp_gro_receive);
 505
 506 static struct sock *udp4_gro_lookup_skb(struct sk_buff *skb, __be16 sport,
 507                                         __be16 dport)
 508 {
 509         const struct iphdr *iph = skb_gro_network_header(skb);
 510
 511         return __udp4_lib_lookup(dev_net(skb->dev), iph->saddr, sport,
 512                                  iph->daddr, dport, inet_iif(skb),
 513                                  inet_sdif(skb), &udp_table, NULL);
 514 }
 515
 516 INDIRECT_CALLABLE_SCOPE
 517 struct sk_buff *udp4_gro_receive(struct list_head *head, struct sk_buff *skb)
 518 {
 519         struct udphdr *uh = udp_gro_udphdr(skb);
 520         struct sock *sk = NULL;
 521         struct sk_buff *pp;
 522
 523         if (unlikely(!uh))
 524                 goto flush;
 525
 526         /* Don't bother verifying checksum if we're going to flush anyway. */
 527         if (NAPI_GRO_CB(skb)->flush)
 528                 goto skip;
 529
 530         if (skb_gro_checksum_validate_zero_check(skb, IPPROTO_UDP, uh->check,
 531                                                  inet_gro_compute_pseudo))
 532                 goto flush;
 533         else if (uh->check)
 534                 skb_gro_checksum_try_convert(skb, IPPROTO_UDP,
 535                                              inet_gro_compute_pseudo);
 536 skip:
 537         NAPI_GRO_CB(skb)->is_ipv6 = 0;
 538         rcu_read_lock();
 539
 540         if (static_branch_unlikely(&udp_encap_needed_key))
 541                 sk = udp4_gro_lookup_skb(skb, uh->source, uh->dest);
 542
 543         pp = udp_gro_receive(head, skb, uh, sk);
 544         rcu_read_unlock();
 545         return pp;
 546
 547 flush:
 548         NAPI_GRO_CB(skb)->flush = 1;
 549         return NULL;
 550 }
 551
 552 static int udp_gro_complete_segment(struct sk_buff *skb)
 553 {
 554         struct udphdr *uh = udp_hdr(skb);
 555
 556         skb->csum_start = (unsigned char *)uh - skb->head;
 557         skb->csum_offset = offsetof(struct udphdr, check);
 558         skb->ip_summed = CHECKSUM_PARTIAL;
 559
 560         skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
 561         skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_L4;
 562         return 0;
 563 }
 564
 565 int udp_gro_complete(struct sk_buff *skb, int nhoff,
 566                      udp_lookup_t lookup)
 567 {
 568         __be16 newlen = htons(skb->len - nhoff);
 569         struct udphdr *uh = (struct udphdr *)(skb->data + nhoff);
 570         struct sock *sk;
 571         int err;
 572
 573         uh->len = newlen;
 574
 575         rcu_read_lock();
 576         sk = INDIRECT_CALL_INET(lookup, udp6_lib_lookup_skb,
 577                                 udp4_lib_lookup_skb, skb, uh->source, uh->dest);
 578         if (sk && udp_sk(sk)->gro_complete) {
 579                 skb_shinfo(skb)->gso_type = uh->check ? SKB_GSO_UDP_TUNNEL_CSUM
 580                                         : SKB_GSO_UDP_TUNNEL;
 581
 582                 /* Set encapsulation before calling into inner gro_complete()
 583                  * functions to make them set up the inner offsets.
 584                  */
 585                 skb->encapsulation = 1;
 586                 err = udp_sk(sk)->gro_complete(sk, skb,
 587                                 nhoff + sizeof(struct udphdr));
 588         } else {
 589                 err = udp_gro_complete_segment(skb);
 590         }
 591         rcu_read_unlock();
 592
 593         if (skb->remcsum_offload)
 594                 skb_shinfo(skb)->gso_type |= SKB_GSO_TUNNEL_REMCSUM;
 595
 596         return err;
 597 }
 598 EXPORT_SYMBOL(udp_gro_complete);
 599
 600 INDIRECT_CALLABLE_SCOPE int udp4_gro_complete(struct sk_buff *skb, int nhoff)
 601 {
 602         const struct iphdr *iph = ip_hdr(skb);
 603         struct udphdr *uh = (struct udphdr *)(skb->data + nhoff);
 604
 605         if (NAPI_GRO_CB(skb)->is_flist) {
 606                 uh->len = htons(skb->len - nhoff);
 607
 608                 skb_shinfo(skb)->gso_type |= (SKB_GSO_FRAGLIST|SKB_GSO_UDP_L4);
 609                 skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
 610
 611                 if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
 612                         if (skb->csum_level < SKB_MAX_CSUM_LEVEL)
 613                                 skb->csum_level++;
 614                 } else {
 615                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 616                         skb->csum_level = 0;
 617                 }
 618
 619                 return 0;
 620         }
 621
 622         if (uh->check)
 623                 uh->check = ~udp_v4_check(skb->len - nhoff, iph->saddr,
 624                                           iph->daddr, 0);
 625
 626         return udp_gro_complete(skb, nhoff, udp4_lib_lookup_skb);
 627 }
 628
 629 static const struct net_offload udpv4_offload = {
 630         .callbacks = {
 631                 .gso_segment = udp4_ufo_fragment,
 632                 .gro_receive  = udp4_gro_receive,
 633                 .gro_complete = udp4_gro_complete,
 634         },
 635 };
 636
 637 int __init udpv4_offload_init(void)
 638 {
 639         return inet_add_offload(&udpv4_offload, IPPROTO_UDP);
 640 }