net/ipv4/udp_offload.c

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