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 (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         /* preserve TX timestamp flags and TS key for first segment */
 228         skb_shinfo(seg)->tskey = skb_shinfo(gso_skb)->tskey;
 229         skb_shinfo(seg)->tx_flags |=
 230                         (skb_shinfo(gso_skb)->tx_flags & SKBTX_ANY_TSTAMP);
 231
 232         /* compute checksum adjustment based on old length versus new */
 233         newlen = htons(sizeof(*uh) + mss);
 234         check = csum16_add(csum16_sub(uh->check, uh->len), newlen);
 235
 236         for (;;) {
 237                 if (copy_dtor) {
 238                         seg->destructor = sock_wfree;
 239                         seg->sk = sk;
 240                         sum_truesize += seg->truesize;
 241                 }
 242
 243                 if (!seg->next)
 244                         break;
 245
 246                 uh->len = newlen;
 247                 uh->check = check;
 248
 249                 if (seg->ip_summed == CHECKSUM_PARTIAL)
 250                         gso_reset_checksum(seg, ~check);
 251                 else
 252                         uh->check = gso_make_checksum(seg, ~check) ? :
 253                                     CSUM_MANGLED_0;
 254
 255                 seg = seg->next;
 256                 uh = udp_hdr(seg);
 257         }
 258
 259         /* last packet can be partial gso_size, account for that in checksum */
 260         newlen = htons(skb_tail_pointer(seg) - skb_transport_header(seg) +
 261                        seg->data_len);
 262         check = csum16_add(csum16_sub(uh->check, uh->len), newlen);
 263
 264         uh->len = newlen;
 265         uh->check = check;
 266
 267         if (seg->ip_summed == CHECKSUM_PARTIAL)
 268                 gso_reset_checksum(seg, ~check);
 269         else
 270                 uh->check = gso_make_checksum(seg, ~check) ? : CSUM_MANGLED_0;
 271
 272         /* update refcount for the packet */
 273         if (copy_dtor) {
 274                 int delta = sum_truesize - gso_skb->truesize;
 275
 276                 /* In some pathological cases, delta can be negative.
 277                  * We need to either use refcount_add() or refcount_sub_and_test()
 278                  */
 279                 if (likely(delta >= 0))
 280                         refcount_add(delta, &sk->sk_wmem_alloc);
 281                 else
 282                         WARN_ON_ONCE(refcount_sub_and_test(-delta, &sk->sk_wmem_alloc));
 283         }
 284         return segs;
 285 }
 286 EXPORT_SYMBOL_GPL(__udp_gso_segment);
 287
 288 static struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb,
 289                                          netdev_features_t features)
 290 {
 291         struct sk_buff *segs = ERR_PTR(-EINVAL);
 292         unsigned int mss;
 293         __wsum csum;
 294         struct udphdr *uh;
 295         struct iphdr *iph;
 296
 297         if (skb->encapsulation &&
 298             (skb_shinfo(skb)->gso_type &
 299              (SKB_GSO_UDP_TUNNEL|SKB_GSO_UDP_TUNNEL_CSUM))) {
 300                 segs = skb_udp_tunnel_segment(skb, features, false);
 301                 goto out;
 302         }
 303
 304         if (!(skb_shinfo(skb)->gso_type & (SKB_GSO_UDP | SKB_GSO_UDP_L4)))
 305                 goto out;
 306
 307         if (!pskb_may_pull(skb, sizeof(struct udphdr)))
 308                 goto out;
 309
 310         if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4)
 311                 return __udp_gso_segment(skb, features);
 312
 313         mss = skb_shinfo(skb)->gso_size;
 314         if (unlikely(skb->len <= mss))
 315                 goto out;
 316
 317         /* Do software UFO. Complete and fill in the UDP checksum as
 318          * HW cannot do checksum of UDP packets sent as multiple
 319          * IP fragments.
 320          */
 321
 322         uh = udp_hdr(skb);
 323         iph = ip_hdr(skb);
 324
 325         uh->check = 0;
 326         csum = skb_checksum(skb, 0, skb->len, 0);
 327         uh->check = udp_v4_check(skb->len, iph->saddr, iph->daddr, csum);
 328         if (uh->check == 0)
 329                 uh->check = CSUM_MANGLED_0;
 330
 331         skb->ip_summed = CHECKSUM_UNNECESSARY;
 332
 333         /* If there is no outer header we can fake a checksum offload
 334          * due to the fact that we have already done the checksum in
 335          * software prior to segmenting the frame.
 336          */
 337         if (!skb->encap_hdr_csum)
 338                 features |= NETIF_F_HW_CSUM;
 339
 340         /* Fragment the skb. IP headers of the fragments are updated in
 341          * inet_gso_segment()
 342          */
 343         segs = skb_segment(skb, features);
 344 out:
 345         return segs;
 346 }
 347
 348 #define UDP_GRO_CNT_MAX 64
 349 static struct sk_buff *udp_gro_receive_segment(struct list_head *head,
 350                                                struct sk_buff *skb)
 351 {
 352         struct udphdr *uh = udp_hdr(skb);
 353         struct sk_buff *pp = NULL;
 354         struct udphdr *uh2;
 355         struct sk_buff *p;
 356         unsigned int ulen;
 357
 358         /* requires non zero csum, for symmetry with GSO */
 359         if (!uh->check) {
 360                 NAPI_GRO_CB(skb)->flush = 1;
 361                 return NULL;
 362         }
 363
 364         /* Do not deal with padded or malicious packets, sorry ! */
 365         ulen = ntohs(uh->len);
 366         if (ulen <= sizeof(*uh) || ulen != skb_gro_len(skb)) {
 367                 NAPI_GRO_CB(skb)->flush = 1;
 368                 return NULL;
 369         }
 370         /* pull encapsulating udp header */
 371         skb_gro_pull(skb, sizeof(struct udphdr));
 372         skb_gro_postpull_rcsum(skb, uh, sizeof(struct udphdr));
 373
 374         list_for_each_entry(p, head, list) {
 375                 if (!NAPI_GRO_CB(p)->same_flow)
 376                         continue;
 377
 378                 uh2 = udp_hdr(p);
 379
 380                 /* Match ports only, as csum is always non zero */
 381                 if ((*(u32 *)&uh->source != *(u32 *)&uh2->source)) {
 382                         NAPI_GRO_CB(p)->same_flow = 0;
 383                         continue;
 384                 }
 385
 386                 /* Terminate the flow on len mismatch or if it grow "too much".
 387                  * Under small packet flood GRO count could elsewhere grow a lot
 388                  * leading to excessive truesize values.
 389                  * On len mismatch merge the first packet shorter than gso_size,
 390                  * otherwise complete the GRO packet.
 391                  */
 392                 if (ulen > ntohs(uh2->len) || skb_gro_receive(p, skb) ||
 393                     ulen != ntohs(uh2->len) ||
 394                     NAPI_GRO_CB(p)->count >= UDP_GRO_CNT_MAX)
 395                         pp = p;
 396
 397                 return pp;
 398         }
 399
 400         /* mismatch, but we never need to flush */
 401         return NULL;
 402 }
 403
 404 INDIRECT_CALLABLE_DECLARE(struct sock *udp6_lib_lookup_skb(struct sk_buff *skb,
 405                                                    __be16 sport, __be16 dport));
 406 struct sk_buff *udp_gro_receive(struct list_head *head, struct sk_buff *skb,
 407                                 struct udphdr *uh, udp_lookup_t lookup)
 408 {
 409         struct sk_buff *pp = NULL;
 410         struct sk_buff *p;
 411         struct udphdr *uh2;
 412         unsigned int off = skb_gro_offset(skb);
 413         int flush = 1;
 414         struct sock *sk;
 415
 416         rcu_read_lock();
 417         sk = INDIRECT_CALL_INET(lookup, udp6_lib_lookup_skb,
 418                                 udp4_lib_lookup_skb, skb, uh->source, uh->dest);
 419         if (!sk)
 420                 goto out_unlock;
 421
 422         if (udp_sk(sk)->gro_enabled) {
 423                 pp = call_gro_receive(udp_gro_receive_segment, head, skb);
 424                 rcu_read_unlock();
 425                 return pp;
 426         }
 427
 428         if (NAPI_GRO_CB(skb)->encap_mark ||
 429             (skb->ip_summed != CHECKSUM_PARTIAL &&
 430              NAPI_GRO_CB(skb)->csum_cnt == 0 &&
 431              !NAPI_GRO_CB(skb)->csum_valid) ||
 432             !udp_sk(sk)->gro_receive)
 433                 goto out_unlock;
 434
 435         /* mark that this skb passed once through the tunnel gro layer */
 436         NAPI_GRO_CB(skb)->encap_mark = 1;
 437
 438         flush = 0;
 439
 440         list_for_each_entry(p, head, list) {
 441                 if (!NAPI_GRO_CB(p)->same_flow)
 442                         continue;
 443
 444                 uh2 = (struct udphdr   *)(p->data + off);
 445
 446                 /* Match ports and either checksums are either both zero
 447                  * or nonzero.
 448                  */
 449                 if ((*(u32 *)&uh->source != *(u32 *)&uh2->source) ||
 450                     (!uh->check ^ !uh2->check)) {
 451                         NAPI_GRO_CB(p)->same_flow = 0;
 452                         continue;
 453                 }
 454         }
 455
 456         skb_gro_pull(skb, sizeof(struct udphdr)); /* pull encapsulating udp header */
 457         skb_gro_postpull_rcsum(skb, uh, sizeof(struct udphdr));
 458         pp = call_gro_receive_sk(udp_sk(sk)->gro_receive, sk, head, skb);
 459
 460 out_unlock:
 461         rcu_read_unlock();
 462         skb_gro_flush_final(skb, pp, flush);
 463         return pp;
 464 }
 465 EXPORT_SYMBOL(udp_gro_receive);
 466
 467 INDIRECT_CALLABLE_SCOPE
 468 struct sk_buff *udp4_gro_receive(struct list_head *head, struct sk_buff *skb)
 469 {
 470         struct udphdr *uh = udp_gro_udphdr(skb);
 471
 472         if (unlikely(!uh) || !static_branch_unlikely(&udp_encap_needed_key))
 473                 goto flush;
 474
 475         /* Don't bother verifying checksum if we're going to flush anyway. */
 476         if (NAPI_GRO_CB(skb)->flush)
 477                 goto skip;
 478
 479         if (skb_gro_checksum_validate_zero_check(skb, IPPROTO_UDP, uh->check,
 480                                                  inet_gro_compute_pseudo))
 481                 goto flush;
 482         else if (uh->check)
 483                 skb_gro_checksum_try_convert(skb, IPPROTO_UDP, uh->check,
 484                                              inet_gro_compute_pseudo);
 485 skip:
 486         NAPI_GRO_CB(skb)->is_ipv6 = 0;
 487         return udp_gro_receive(head, skb, uh, udp4_lib_lookup_skb);
 488
 489 flush:
 490         NAPI_GRO_CB(skb)->flush = 1;
 491         return NULL;
 492 }
 493
 494 static int udp_gro_complete_segment(struct sk_buff *skb)
 495 {
 496         struct udphdr *uh = udp_hdr(skb);
 497
 498         skb->csum_start = (unsigned char *)uh - skb->head;
 499         skb->csum_offset = offsetof(struct udphdr, check);
 500         skb->ip_summed = CHECKSUM_PARTIAL;
 501
 502         skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
 503         skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_L4;
 504         return 0;
 505 }
 506
 507 int udp_gro_complete(struct sk_buff *skb, int nhoff,
 508                      udp_lookup_t lookup)
 509 {
 510         __be16 newlen = htons(skb->len - nhoff);
 511         struct udphdr *uh = (struct udphdr *)(skb->data + nhoff);
 512         int err = -ENOSYS;
 513         struct sock *sk;
 514
 515         uh->len = newlen;
 516
 517         rcu_read_lock();
 518         sk = INDIRECT_CALL_INET(lookup, udp6_lib_lookup_skb,
 519                                 udp4_lib_lookup_skb, skb, uh->source, uh->dest);
 520         if (sk && udp_sk(sk)->gro_enabled) {
 521                 err = udp_gro_complete_segment(skb);
 522         } else if (sk && udp_sk(sk)->gro_complete) {
 523                 skb_shinfo(skb)->gso_type = uh->check ? SKB_GSO_UDP_TUNNEL_CSUM
 524                                         : SKB_GSO_UDP_TUNNEL;
 525
 526                 /* Set encapsulation before calling into inner gro_complete()
 527                  * functions to make them set up the inner offsets.
 528                  */
 529                 skb->encapsulation = 1;
 530                 err = udp_sk(sk)->gro_complete(sk, skb,
 531                                 nhoff + sizeof(struct udphdr));
 532         }
 533         rcu_read_unlock();
 534
 535         if (skb->remcsum_offload)
 536                 skb_shinfo(skb)->gso_type |= SKB_GSO_TUNNEL_REMCSUM;
 537
 538         return err;
 539 }
 540 EXPORT_SYMBOL(udp_gro_complete);
 541
 542 INDIRECT_CALLABLE_SCOPE int udp4_gro_complete(struct sk_buff *skb, int nhoff)
 543 {
 544         const struct iphdr *iph = ip_hdr(skb);
 545         struct udphdr *uh = (struct udphdr *)(skb->data + nhoff);
 546
 547         if (uh->check)
 548                 uh->check = ~udp_v4_check(skb->len - nhoff, iph->saddr,
 549                                           iph->daddr, 0);
 550
 551         return udp_gro_complete(skb, nhoff, udp4_lib_lookup_skb);
 552 }
 553
 554 static const struct net_offload udpv4_offload = {
 555         .callbacks = {
 556                 .gso_segment = udp4_ufo_fragment,
 557                 .gro_receive  = udp4_gro_receive,
 558                 .gro_complete = udp4_gro_complete,
 559         },
 560 };
 561
 562 int __init udpv4_offload_init(void)
 563 {
 564         return inet_add_offload(&udpv4_offload, IPPROTO_UDP);
 565 }