net/ipv4/tcp_offload.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *      IPV4 GSO/GRO offload support
   4  *      Linux INET implementation
   5  *
   6  *      TCPv4 GSO/GRO support
   7  */
   8
   9 #include <linux/indirect_call_wrapper.h>
  10 #include <linux/skbuff.h>
  11 #include <net/gro.h>
  12 #include <net/gso.h>
  13 #include <net/tcp.h>
  14 #include <net/protocol.h>
  15
  16 static void tcp_gso_tstamp(struct sk_buff *skb, unsigned int ts_seq,
  17                            unsigned int seq, unsigned int mss)
  18 {
  19         while (skb) {
  20                 if (before(ts_seq, seq + mss)) {
  21                         skb_shinfo(skb)->tx_flags |= SKBTX_SW_TSTAMP;
  22                         skb_shinfo(skb)->tskey = ts_seq;
  23                         return;
  24                 }
  25
  26                 skb = skb->next;
  27                 seq += mss;
  28         }
  29 }
  30
  31 static void __tcpv4_gso_segment_csum(struct sk_buff *seg,
  32                                      __be32 *oldip, __be32 newip,
  33                                      __be16 *oldport, __be16 newport)
  34 {
  35         struct tcphdr *th;
  36         struct iphdr *iph;
  37
  38         if (*oldip == newip && *oldport == newport)
  39                 return;
  40
  41         th = tcp_hdr(seg);
  42         iph = ip_hdr(seg);
  43
  44         inet_proto_csum_replace4(&th->check, seg, *oldip, newip, true);
  45         inet_proto_csum_replace2(&th->check, seg, *oldport, newport, false);
  46         *oldport = newport;
  47
  48         csum_replace4(&iph->check, *oldip, newip);
  49         *oldip = newip;
  50 }
  51
  52 static struct sk_buff *__tcpv4_gso_segment_list_csum(struct sk_buff *segs)
  53 {
  54         const struct tcphdr *th;
  55         const struct iphdr *iph;
  56         struct sk_buff *seg;
  57         struct tcphdr *th2;
  58         struct iphdr *iph2;
  59
  60         seg = segs;
  61         th = tcp_hdr(seg);
  62         iph = ip_hdr(seg);
  63         th2 = tcp_hdr(seg->next);
  64         iph2 = ip_hdr(seg->next);
  65
  66         if (!(*(const u32 *)&th->source ^ *(const u32 *)&th2->source) &&
  67             iph->daddr == iph2->daddr && iph->saddr == iph2->saddr)
  68                 return segs;
  69
  70         while ((seg = seg->next)) {
  71                 th2 = tcp_hdr(seg);
  72                 iph2 = ip_hdr(seg);
  73
  74                 __tcpv4_gso_segment_csum(seg,
  75                                          &iph2->saddr, iph->saddr,
  76                                          &th2->source, th->source);
  77                 __tcpv4_gso_segment_csum(seg,
  78                                          &iph2->daddr, iph->daddr,
  79                                          &th2->dest, th->dest);
  80         }
  81
  82         return segs;
  83 }
  84
  85 static struct sk_buff *__tcp4_gso_segment_list(struct sk_buff *skb,
  86                                               netdev_features_t features)
  87 {
  88         skb = skb_segment_list(skb, features, skb_mac_header_len(skb));
  89         if (IS_ERR(skb))
  90                 return skb;
  91
  92         return __tcpv4_gso_segment_list_csum(skb);
  93 }
  94
  95 static struct sk_buff *tcp4_gso_segment(struct sk_buff *skb,
  96                                         netdev_features_t features)
  97 {
  98         if (!(skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4))
  99                 return ERR_PTR(-EINVAL);
 100
 101         if (!pskb_may_pull(skb, sizeof(struct tcphdr)))
 102                 return ERR_PTR(-EINVAL);
 103
 104         if (skb_shinfo(skb)->gso_type & SKB_GSO_FRAGLIST) {
 105                 struct tcphdr *th = tcp_hdr(skb);
 106
 107                 if (skb_pagelen(skb) - th->doff * 4 == skb_shinfo(skb)->gso_size)
 108                         return __tcp4_gso_segment_list(skb, features);
 109
 110                 skb->ip_summed = CHECKSUM_NONE;
 111         }
 112
 113         if (unlikely(skb->ip_summed != CHECKSUM_PARTIAL)) {
 114                 const struct iphdr *iph = ip_hdr(skb);
 115                 struct tcphdr *th = tcp_hdr(skb);
 116
 117                 /* Set up checksum pseudo header, usually expect stack to
 118                  * have done this already.
 119                  */
 120
 121                 th->check = 0;
 122                 skb->ip_summed = CHECKSUM_PARTIAL;
 123                 __tcp_v4_send_check(skb, iph->saddr, iph->daddr);
 124         }
 125
 126         return tcp_gso_segment(skb, features);
 127 }
 128
 129 struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
 130                                 netdev_features_t features)
 131 {
 132         struct sk_buff *segs = ERR_PTR(-EINVAL);
 133         unsigned int sum_truesize = 0;
 134         struct tcphdr *th;
 135         unsigned int thlen;
 136         unsigned int seq;
 137         unsigned int oldlen;
 138         unsigned int mss;
 139         struct sk_buff *gso_skb = skb;
 140         __sum16 newcheck;
 141         bool ooo_okay, copy_destructor;
 142         __wsum delta;
 143
 144         th = tcp_hdr(skb);
 145         thlen = th->doff * 4;
 146         if (thlen < sizeof(*th))
 147                 goto out;
 148
 149         if (unlikely(skb_checksum_start(skb) != skb_transport_header(skb)))
 150                 goto out;
 151
 152         if (!pskb_may_pull(skb, thlen))
 153                 goto out;
 154
 155         oldlen = ~skb->len;
 156         __skb_pull(skb, thlen);
 157
 158         mss = skb_shinfo(skb)->gso_size;
 159         if (unlikely(skb->len <= mss))
 160                 goto out;
 161
 162         if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
 163                 /* Packet is from an untrusted source, reset gso_segs. */
 164
 165                 skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
 166
 167                 segs = NULL;
 168                 goto out;
 169         }
 170
 171         copy_destructor = gso_skb->destructor == tcp_wfree;
 172         ooo_okay = gso_skb->ooo_okay;
 173         /* All segments but the first should have ooo_okay cleared */
 174         skb->ooo_okay = 0;
 175
 176         segs = skb_segment(skb, features);
 177         if (IS_ERR(segs))
 178                 goto out;
 179
 180         /* Only first segment might have ooo_okay set */
 181         segs->ooo_okay = ooo_okay;
 182
 183         /* GSO partial and frag_list segmentation only requires splitting
 184          * the frame into an MSS multiple and possibly a remainder, both
 185          * cases return a GSO skb. So update the mss now.
 186          */
 187         if (skb_is_gso(segs))
 188                 mss *= skb_shinfo(segs)->gso_segs;
 189
 190         delta = (__force __wsum)htonl(oldlen + thlen + mss);
 191
 192         skb = segs;
 193         th = tcp_hdr(skb);
 194         seq = ntohl(th->seq);
 195
 196         if (unlikely(skb_shinfo(gso_skb)->tx_flags & SKBTX_SW_TSTAMP))
 197                 tcp_gso_tstamp(segs, skb_shinfo(gso_skb)->tskey, seq, mss);
 198
 199         newcheck = ~csum_fold(csum_add(csum_unfold(th->check), delta));
 200
 201         while (skb->next) {
 202                 th->fin = th->psh = 0;
 203                 th->check = newcheck;
 204
 205                 if (skb->ip_summed == CHECKSUM_PARTIAL)
 206                         gso_reset_checksum(skb, ~th->check);
 207                 else
 208                         th->check = gso_make_checksum(skb, ~th->check);
 209
 210                 seq += mss;
 211                 if (copy_destructor) {
 212                         skb->destructor = gso_skb->destructor;
 213                         skb->sk = gso_skb->sk;
 214                         sum_truesize += skb->truesize;
 215                 }
 216                 skb = skb->next;
 217                 th = tcp_hdr(skb);
 218
 219                 th->seq = htonl(seq);
 220                 th->cwr = 0;
 221         }
 222
 223         /* Following permits TCP Small Queues to work well with GSO :
 224          * The callback to TCP stack will be called at the time last frag
 225          * is freed at TX completion, and not right now when gso_skb
 226          * is freed by GSO engine
 227          */
 228         if (copy_destructor) {
 229                 int delta;
 230
 231                 swap(gso_skb->sk, skb->sk);
 232                 swap(gso_skb->destructor, skb->destructor);
 233                 sum_truesize += skb->truesize;
 234                 delta = sum_truesize - gso_skb->truesize;
 235                 /* In some pathological cases, delta can be negative.
 236                  * We need to either use refcount_add() or refcount_sub_and_test()
 237                  */
 238                 if (likely(delta >= 0))
 239                         refcount_add(delta, &skb->sk->sk_wmem_alloc);
 240                 else
 241                         WARN_ON_ONCE(refcount_sub_and_test(-delta, &skb->sk->sk_wmem_alloc));
 242         }
 243
 244         delta = (__force __wsum)htonl(oldlen +
 245                                       (skb_tail_pointer(skb) -
 246                                        skb_transport_header(skb)) +
 247                                       skb->data_len);
 248         th->check = ~csum_fold(csum_add(csum_unfold(th->check), delta));
 249         if (skb->ip_summed == CHECKSUM_PARTIAL)
 250                 gso_reset_checksum(skb, ~th->check);
 251         else
 252                 th->check = gso_make_checksum(skb, ~th->check);
 253 out:
 254         return segs;
 255 }
 256
 257 struct sk_buff *tcp_gro_lookup(struct list_head *head, struct tcphdr *th)
 258 {
 259         struct tcphdr *th2;
 260         struct sk_buff *p;
 261
 262         list_for_each_entry(p, head, list) {
 263                 if (!NAPI_GRO_CB(p)->same_flow)
 264                         continue;
 265
 266                 th2 = tcp_hdr(p);
 267                 if (*(u32 *)&th->source ^ *(u32 *)&th2->source) {
 268                         NAPI_GRO_CB(p)->same_flow = 0;
 269                         continue;
 270                 }
 271
 272                 return p;
 273         }
 274
 275         return NULL;
 276 }
 277
 278 struct tcphdr *tcp_gro_pull_header(struct sk_buff *skb)
 279 {
 280         unsigned int thlen, hlen, off;
 281         struct tcphdr *th;
 282
 283         off = skb_gro_offset(skb);
 284         hlen = off + sizeof(*th);
 285         th = skb_gro_header(skb, hlen, off);
 286         if (unlikely(!th))
 287                 return NULL;
 288
 289         thlen = th->doff * 4;
 290         if (thlen < sizeof(*th))
 291                 return NULL;
 292
 293         hlen = off + thlen;
 294         if (!skb_gro_may_pull(skb, hlen)) {
 295                 th = skb_gro_header_slow(skb, hlen, off);
 296                 if (unlikely(!th))
 297                         return NULL;
 298         }
 299
 300         skb_gro_pull(skb, thlen);
 301
 302         return th;
 303 }
 304
 305 struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb,
 306                                 struct tcphdr *th)
 307 {
 308         unsigned int thlen = th->doff * 4;
 309         struct sk_buff *pp = NULL;
 310         struct sk_buff *p;
 311         struct tcphdr *th2;
 312         unsigned int len;
 313         __be32 flags;
 314         unsigned int mss = 1;
 315         int flush = 1;
 316         int i;
 317
 318         len = skb_gro_len(skb);
 319         flags = tcp_flag_word(th);
 320
 321         p = tcp_gro_lookup(head, th);
 322         if (!p)
 323                 goto out_check_final;
 324
 325         th2 = tcp_hdr(p);
 326         flush = (__force int)(flags & TCP_FLAG_CWR);
 327         flush |= (__force int)((flags ^ tcp_flag_word(th2)) &
 328                   ~(TCP_FLAG_CWR | TCP_FLAG_FIN | TCP_FLAG_PSH));
 329         flush |= (__force int)(th->ack_seq ^ th2->ack_seq);
 330         for (i = sizeof(*th); i < thlen; i += 4)
 331                 flush |= *(u32 *)((u8 *)th + i) ^
 332                          *(u32 *)((u8 *)th2 + i);
 333
 334         flush |= gro_receive_network_flush(th, th2, p);
 335
 336         mss = skb_shinfo(p)->gso_size;
 337
 338         /* If skb is a GRO packet, make sure its gso_size matches prior packet mss.
 339          * If it is a single frame, do not aggregate it if its length
 340          * is bigger than our mss.
 341          */
 342         if (unlikely(skb_is_gso(skb)))
 343                 flush |= (mss != skb_shinfo(skb)->gso_size);
 344         else
 345                 flush |= (len - 1) >= mss;
 346
 347         flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);
 348         flush |= skb_cmp_decrypted(p, skb);
 349
 350         if (unlikely(NAPI_GRO_CB(p)->is_flist)) {
 351                 flush |= (__force int)(flags ^ tcp_flag_word(th2));
 352                 flush |= skb->ip_summed != p->ip_summed;
 353                 flush |= skb->csum_level != p->csum_level;
 354                 flush |= NAPI_GRO_CB(p)->count >= 64;
 355
 356                 if (flush || skb_gro_receive_list(p, skb))
 357                         mss = 1;
 358
 359                 goto out_check_final;
 360         }
 361
 362         if (flush || skb_gro_receive(p, skb)) {
 363                 mss = 1;
 364                 goto out_check_final;
 365         }
 366
 367         tcp_flag_word(th2) |= flags & (TCP_FLAG_FIN | TCP_FLAG_PSH);
 368
 369 out_check_final:
 370         /* Force a flush if last segment is smaller than mss. */
 371         if (unlikely(skb_is_gso(skb)))
 372                 flush = len != NAPI_GRO_CB(skb)->count * skb_shinfo(skb)->gso_size;
 373         else
 374                 flush = len < mss;
 375
 376         flush |= (__force int)(flags & (TCP_FLAG_URG | TCP_FLAG_PSH |
 377                                         TCP_FLAG_RST | TCP_FLAG_SYN |
 378                                         TCP_FLAG_FIN));
 379
 380         if (p && (!NAPI_GRO_CB(skb)->same_flow || flush))
 381                 pp = p;
 382
 383         NAPI_GRO_CB(skb)->flush |= (flush != 0);
 384
 385         return pp;
 386 }
 387
 388 void tcp_gro_complete(struct sk_buff *skb)
 389 {
 390         struct tcphdr *th = tcp_hdr(skb);
 391         struct skb_shared_info *shinfo;
 392
 393         if (skb->encapsulation)
 394                 skb->inner_transport_header = skb->transport_header;
 395
 396         skb->csum_start = (unsigned char *)th - skb->head;
 397         skb->csum_offset = offsetof(struct tcphdr, check);
 398         skb->ip_summed = CHECKSUM_PARTIAL;
 399
 400         shinfo = skb_shinfo(skb);
 401         shinfo->gso_segs = NAPI_GRO_CB(skb)->count;
 402
 403         if (th->cwr)
 404                 shinfo->gso_type |= SKB_GSO_TCP_ECN;
 405 }
 406 EXPORT_SYMBOL(tcp_gro_complete);
 407
 408 static void tcp4_check_fraglist_gro(struct list_head *head, struct sk_buff *skb,
 409                                     struct tcphdr *th)
 410 {
 411         const struct iphdr *iph;
 412         struct sk_buff *p;
 413         struct sock *sk;
 414         struct net *net;
 415         int iif, sdif;
 416
 417         if (likely(!(skb->dev->features & NETIF_F_GRO_FRAGLIST)))
 418                 return;
 419
 420         p = tcp_gro_lookup(head, th);
 421         if (p) {
 422                 NAPI_GRO_CB(skb)->is_flist = NAPI_GRO_CB(p)->is_flist;
 423                 return;
 424         }
 425
 426         inet_get_iif_sdif(skb, &iif, &sdif);
 427         iph = skb_gro_network_header(skb);
 428         net = dev_net(skb->dev);
 429         sk = __inet_lookup_established(net, net->ipv4.tcp_death_row.hashinfo,
 430                                        iph->saddr, th->source,
 431                                        iph->daddr, ntohs(th->dest),
 432                                        iif, sdif);
 433         NAPI_GRO_CB(skb)->is_flist = !sk;
 434         if (sk)
 435                 sock_put(sk);
 436 }
 437
 438 INDIRECT_CALLABLE_SCOPE
 439 struct sk_buff *tcp4_gro_receive(struct list_head *head, struct sk_buff *skb)
 440 {
 441         struct tcphdr *th;
 442
 443         /* Don't bother verifying checksum if we're going to flush anyway. */
 444         if (!NAPI_GRO_CB(skb)->flush &&
 445             skb_gro_checksum_validate(skb, IPPROTO_TCP,
 446                                       inet_gro_compute_pseudo))
 447                 goto flush;
 448
 449         th = tcp_gro_pull_header(skb);
 450         if (!th)
 451                 goto flush;
 452
 453         tcp4_check_fraglist_gro(head, skb, th);
 454
 455         return tcp_gro_receive(head, skb, th);
 456
 457 flush:
 458         NAPI_GRO_CB(skb)->flush = 1;
 459         return NULL;
 460 }
 461
 462 INDIRECT_CALLABLE_SCOPE int tcp4_gro_complete(struct sk_buff *skb, int thoff)
 463 {
 464         const u16 offset = NAPI_GRO_CB(skb)->network_offsets[skb->encapsulation];
 465         const struct iphdr *iph = (struct iphdr *)(skb->data + offset);
 466         struct tcphdr *th = tcp_hdr(skb);
 467
 468         if (unlikely(NAPI_GRO_CB(skb)->is_flist)) {
 469                 skb_shinfo(skb)->gso_type |= SKB_GSO_FRAGLIST | SKB_GSO_TCPV4;
 470                 skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
 471
 472                 __skb_incr_checksum_unnecessary(skb);
 473
 474                 return 0;
 475         }
 476
 477         th->check = ~tcp_v4_check(skb->len - thoff, iph->saddr,
 478                                   iph->daddr, 0);
 479
 480         skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4 |
 481                         (NAPI_GRO_CB(skb)->ip_fixedid * SKB_GSO_TCP_FIXEDID);
 482
 483         tcp_gro_complete(skb);
 484         return 0;
 485 }
 486
 487 int __init tcpv4_offload_init(void)
 488 {
 489         net_hotdata.tcpv4_offload = (struct net_offload) {
 490                 .callbacks = {
 491                         .gso_segment    =       tcp4_gso_segment,
 492                         .gro_receive    =       tcp4_gro_receive,
 493                         .gro_complete   =       tcp4_gro_complete,
 494                 },
 495         };
 496         return inet_add_offload(&net_hotdata.tcpv4_offload, IPPROTO_TCP);
 497 }