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->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 struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
 188                                   netdev_features_t features)
 189 {
 190         struct sock *sk = gso_skb->sk;
 191         unsigned int sum_truesize = 0;
 192         struct sk_buff *segs, *seg;
 193         struct udphdr *uh;
 194         unsigned int mss;
 195         bool copy_dtor;
 196         __sum16 check;
 197         __be16 newlen;
 198
 199         mss = skb_shinfo(gso_skb)->gso_size;
 200         if (gso_skb->len <= sizeof(*uh) + mss)
 201                 return ERR_PTR(-EINVAL);
 202
 203         skb_pull(gso_skb, sizeof(*uh));
 204
 205         /* clear destructor to avoid skb_segment assigning it to tail */
 206         copy_dtor = gso_skb->destructor == sock_wfree;
 207         if (copy_dtor)
 208                 gso_skb->destructor = NULL;
 209
 210         segs = skb_segment(gso_skb, features);
 211         if (unlikely(IS_ERR_OR_NULL(segs))) {
 212                 if (copy_dtor)
 213                         gso_skb->destructor = sock_wfree;
 214                 return segs;
 215         }
 216
 217         /* GSO partial and frag_list segmentation only requires splitting
 218          * the frame into an MSS multiple and possibly a remainder, both
 219          * cases return a GSO skb. So update the mss now.
 220          */
 221         if (skb_is_gso(segs))
 222                 mss *= skb_shinfo(segs)->gso_segs;
 223
 224         seg = segs;
 225         uh = udp_hdr(seg);
 226
 227         /* compute checksum adjustment based on old length versus new */
 228         newlen = htons(sizeof(*uh) + mss);
 229         check = csum16_add(csum16_sub(uh->check, uh->len), newlen);
 230
 231         for (;;) {
 232                 if (copy_dtor) {
 233                         seg->destructor = sock_wfree;
 234                         seg->sk = sk;
 235                         sum_truesize += seg->truesize;
 236                 }
 237
 238                 if (!seg->next)
 239                         break;
 240
 241                 uh->len = newlen;
 242                 uh->check = check;
 243
 244                 if (seg->ip_summed == CHECKSUM_PARTIAL)
 245                         gso_reset_checksum(seg, ~check);
 246                 else
 247                         uh->check = gso_make_checksum(seg, ~check) ? :
 248                                     CSUM_MANGLED_0;
 249
 250                 seg = seg->next;
 251                 uh = udp_hdr(seg);
 252         }
 253
 254         /* last packet can be partial gso_size, account for that in checksum */
 255         newlen = htons(skb_tail_pointer(seg) - skb_transport_header(seg) +
 256                        seg->data_len);
 257         check = csum16_add(csum16_sub(uh->check, uh->len), newlen);
 258
 259         uh->len = newlen;
 260         uh->check = check;
 261
 262         if (seg->ip_summed == CHECKSUM_PARTIAL)
 263                 gso_reset_checksum(seg, ~check);
 264         else
 265                 uh->check = gso_make_checksum(seg, ~check) ? : CSUM_MANGLED_0;
 266
 267         /* update refcount for the packet */
 268         if (copy_dtor) {
 269                 int delta = sum_truesize - gso_skb->truesize;
 270
 271                 /* In some pathological cases, delta can be negative.
 272                  * We need to either use refcount_add() or refcount_sub_and_test()
 273                  */
 274                 if (likely(delta >= 0))
 275                         refcount_add(delta, &sk->sk_wmem_alloc);
 276                 else
 277                         WARN_ON_ONCE(refcount_sub_and_test(-delta, &sk->sk_wmem_alloc));
 278         }
 279         return segs;
 280 }
 281 EXPORT_SYMBOL_GPL(__udp_gso_segment);
 282
 283 static struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb,
 284                                          netdev_features_t features)
 285 {
 286         struct sk_buff *segs = ERR_PTR(-EINVAL);
 287         unsigned int mss;
 288         __wsum csum;
 289         struct udphdr *uh;
 290         struct iphdr *iph;
 291
 292         if (skb->encapsulation &&
 293             (skb_shinfo(skb)->gso_type &
 294              (SKB_GSO_UDP_TUNNEL|SKB_GSO_UDP_TUNNEL_CSUM))) {
 295                 segs = skb_udp_tunnel_segment(skb, features, false);
 296                 goto out;
 297         }
 298
 299         if (!(skb_shinfo(skb)->gso_type & (SKB_GSO_UDP | SKB_GSO_UDP_L4)))
 300                 goto out;
 301
 302         if (!pskb_may_pull(skb, sizeof(struct udphdr)))
 303                 goto out;
 304
 305         if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4)
 306                 return __udp_gso_segment(skb, features);
 307
 308         mss = skb_shinfo(skb)->gso_size;
 309         if (unlikely(skb->len <= mss))
 310                 goto out;
 311
 312         /* Do software UFO. Complete and fill in the UDP checksum as
 313          * HW cannot do checksum of UDP packets sent as multiple
 314          * IP fragments.
 315          */
 316
 317         uh = udp_hdr(skb);
 318         iph = ip_hdr(skb);
 319
 320         uh->check = 0;
 321         csum = skb_checksum(skb, 0, skb->len, 0);
 322         uh->check = udp_v4_check(skb->len, iph->saddr, iph->daddr, csum);
 323         if (uh->check == 0)
 324                 uh->check = CSUM_MANGLED_0;
 325
 326         skb->ip_summed = CHECKSUM_UNNECESSARY;
 327
 328         /* If there is no outer header we can fake a checksum offload
 329          * due to the fact that we have already done the checksum in
 330          * software prior to segmenting the frame.
 331          */
 332         if (!skb->encap_hdr_csum)
 333                 features |= NETIF_F_HW_CSUM;
 334
 335         /* Fragment the skb. IP headers of the fragments are updated in
 336          * inet_gso_segment()
 337          */
 338         segs = skb_segment(skb, features);
 339 out:
 340         return segs;
 341 }
 342
 343 #define UDP_GRO_CNT_MAX 64
 344 static struct sk_buff *udp_gro_receive_segment(struct list_head *head,
 345                                                struct sk_buff *skb)
 346 {
 347         struct udphdr *uh = udp_hdr(skb);
 348         struct sk_buff *pp = NULL;
 349         struct udphdr *uh2;
 350         struct sk_buff *p;
 351         unsigned int ulen;
 352
 353         /* requires non zero csum, for symmetry with GSO */
 354         if (!uh->check) {
 355                 NAPI_GRO_CB(skb)->flush = 1;
 356                 return NULL;
 357         }
 358
 359         /* Do not deal with padded or malicious packets, sorry ! */
 360         ulen = ntohs(uh->len);
 361         if (ulen <= sizeof(*uh) || ulen != skb_gro_len(skb)) {
 362                 NAPI_GRO_CB(skb)->flush = 1;
 363                 return NULL;
 364         }
 365         /* pull encapsulating udp header */
 366         skb_gro_pull(skb, sizeof(struct udphdr));
 367         skb_gro_postpull_rcsum(skb, uh, sizeof(struct udphdr));
 368
 369         list_for_each_entry(p, head, list) {
 370                 if (!NAPI_GRO_CB(p)->same_flow)
 371                         continue;
 372
 373                 uh2 = udp_hdr(p);
 374
 375                 /* Match ports only, as csum is always non zero */
 376                 if ((*(u32 *)&uh->source != *(u32 *)&uh2->source)) {
 377                         NAPI_GRO_CB(p)->same_flow = 0;
 378                         continue;
 379                 }
 380
 381                 /* Terminate the flow on len mismatch or if it grow "too much".
 382                  * Under small packet flood GRO count could elsewhere grow a lot
 383                  * leading to excessive truesize values.
 384                  * On len mismatch merge the first packet shorter than gso_size,
 385                  * otherwise complete the GRO packet.
 386                  */
 387                 if (ulen > ntohs(uh2->len) || skb_gro_receive(p, skb) ||
 388                     ulen != ntohs(uh2->len) ||
 389                     NAPI_GRO_CB(p)->count >= UDP_GRO_CNT_MAX)
 390                         pp = p;
 391
 392                 return pp;
 393         }
 394
 395         /* mismatch, but we never need to flush */
 396         return NULL;
 397 }
 398
 399 INDIRECT_CALLABLE_DECLARE(struct sock *udp6_lib_lookup_skb(struct sk_buff *skb,
 400                                                    __be16 sport, __be16 dport));
 401 struct sk_buff *udp_gro_receive(struct list_head *head, struct sk_buff *skb,
 402                                 struct udphdr *uh, udp_lookup_t lookup)
 403 {
 404         struct sk_buff *pp = NULL;
 405         struct sk_buff *p;
 406         struct udphdr *uh2;
 407         unsigned int off = skb_gro_offset(skb);
 408         int flush = 1;
 409         struct sock *sk;
 410
 411         rcu_read_lock();
 412         sk = INDIRECT_CALL_INET(lookup, udp6_lib_lookup_skb,
 413                                 udp4_lib_lookup_skb, skb, uh->source, uh->dest);
 414         if (!sk)
 415                 goto out_unlock;
 416
 417         if (udp_sk(sk)->gro_enabled) {
 418                 pp = call_gro_receive(udp_gro_receive_segment, head, skb);
 419                 rcu_read_unlock();
 420                 return pp;
 421         }
 422
 423         if (NAPI_GRO_CB(skb)->encap_mark ||
 424             (skb->ip_summed != CHECKSUM_PARTIAL &&
 425              NAPI_GRO_CB(skb)->csum_cnt == 0 &&
 426              !NAPI_GRO_CB(skb)->csum_valid) ||
 427             !udp_sk(sk)->gro_receive)
 428                 goto out_unlock;
 429
 430         /* mark that this skb passed once through the tunnel gro layer */
 431         NAPI_GRO_CB(skb)->encap_mark = 1;
 432
 433         flush = 0;
 434
 435         list_for_each_entry(p, head, list) {
 436                 if (!NAPI_GRO_CB(p)->same_flow)
 437                         continue;
 438
 439                 uh2 = (struct udphdr   *)(p->data + off);
 440
 441                 /* Match ports and either checksums are either both zero
 442                  * or nonzero.
 443                  */
 444                 if ((*(u32 *)&uh->source != *(u32 *)&uh2->source) ||
 445                     (!uh->check ^ !uh2->check)) {
 446                         NAPI_GRO_CB(p)->same_flow = 0;
 447                         continue;
 448                 }
 449         }
 450
 451         skb_gro_pull(skb, sizeof(struct udphdr)); /* pull encapsulating udp header */
 452         skb_gro_postpull_rcsum(skb, uh, sizeof(struct udphdr));
 453         pp = call_gro_receive_sk(udp_sk(sk)->gro_receive, sk, head, skb);
 454
 455 out_unlock:
 456         rcu_read_unlock();
 457         skb_gro_flush_final(skb, pp, flush);
 458         return pp;
 459 }
 460 EXPORT_SYMBOL(udp_gro_receive);
 461
 462 INDIRECT_CALLABLE_SCOPE
 463 struct sk_buff *udp4_gro_receive(struct list_head *head, struct sk_buff *skb)
 464 {
 465         struct udphdr *uh = udp_gro_udphdr(skb);
 466
 467         if (unlikely(!uh) || !static_branch_unlikely(&udp_encap_needed_key))
 468                 goto flush;
 469
 470         /* Don't bother verifying checksum if we're going to flush anyway. */
 471         if (NAPI_GRO_CB(skb)->flush)
 472                 goto skip;
 473
 474         if (skb_gro_checksum_validate_zero_check(skb, IPPROTO_UDP, uh->check,
 475                                                  inet_gro_compute_pseudo))
 476                 goto flush;
 477         else if (uh->check)
 478                 skb_gro_checksum_try_convert(skb, IPPROTO_UDP, uh->check,
 479                                              inet_gro_compute_pseudo);
 480 skip:
 481         NAPI_GRO_CB(skb)->is_ipv6 = 0;
 482         return udp_gro_receive(head, skb, uh, udp4_lib_lookup_skb);
 483
 484 flush:
 485         NAPI_GRO_CB(skb)->flush = 1;
 486         return NULL;
 487 }
 488
 489 static int udp_gro_complete_segment(struct sk_buff *skb)
 490 {
 491         struct udphdr *uh = udp_hdr(skb);
 492
 493         skb->csum_start = (unsigned char *)uh - skb->head;
 494         skb->csum_offset = offsetof(struct udphdr, check);
 495         skb->ip_summed = CHECKSUM_PARTIAL;
 496
 497         skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
 498         skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_L4;
 499         return 0;
 500 }
 501
 502 int udp_gro_complete(struct sk_buff *skb, int nhoff,
 503                      udp_lookup_t lookup)
 504 {
 505         __be16 newlen = htons(skb->len - nhoff);
 506         struct udphdr *uh = (struct udphdr *)(skb->data + nhoff);
 507         int err = -ENOSYS;
 508         struct sock *sk;
 509
 510         uh->len = newlen;
 511
 512         rcu_read_lock();
 513         sk = INDIRECT_CALL_INET(lookup, udp6_lib_lookup_skb,
 514                                 udp4_lib_lookup_skb, skb, uh->source, uh->dest);
 515         if (sk && udp_sk(sk)->gro_enabled) {
 516                 err = udp_gro_complete_segment(skb);
 517         } else if (sk && udp_sk(sk)->gro_complete) {
 518                 skb_shinfo(skb)->gso_type = uh->check ? SKB_GSO_UDP_TUNNEL_CSUM
 519                                         : SKB_GSO_UDP_TUNNEL;
 520
 521                 /* Set encapsulation before calling into inner gro_complete()
 522                  * functions to make them set up the inner offsets.
 523                  */
 524                 skb->encapsulation = 1;
 525                 err = udp_sk(sk)->gro_complete(sk, skb,
 526                                 nhoff + sizeof(struct udphdr));
 527         }
 528         rcu_read_unlock();
 529
 530         if (skb->remcsum_offload)
 531                 skb_shinfo(skb)->gso_type |= SKB_GSO_TUNNEL_REMCSUM;
 532
 533         return err;
 534 }
 535 EXPORT_SYMBOL(udp_gro_complete);
 536
 537 INDIRECT_CALLABLE_SCOPE int udp4_gro_complete(struct sk_buff *skb, int nhoff)
 538 {
 539         const struct iphdr *iph = ip_hdr(skb);
 540         struct udphdr *uh = (struct udphdr *)(skb->data + nhoff);
 541
 542         if (uh->check)
 543                 uh->check = ~udp_v4_check(skb->len - nhoff, iph->saddr,
 544                                           iph->daddr, 0);
 545
 546         return udp_gro_complete(skb, nhoff, udp4_lib_lookup_skb);
 547 }
 548
 549 static const struct net_offload udpv4_offload = {
 550         .callbacks = {
 551                 .gso_segment = udp4_ufo_fragment,
 552                 .gro_receive  = udp4_gro_receive,
 553                 .gro_complete = udp4_gro_complete,
 554         },
 555 };
 556
 557 int __init udpv4_offload_init(void)
 558 {
 559         return inet_add_offload(&udpv4_offload, IPPROTO_UDP);
 560 }