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/tcp.h>
  13 #include <net/protocol.h>
  14
  15 static void tcp_gso_tstamp(struct sk_buff *skb, unsigned int ts_seq,
  16                            unsigned int seq, unsigned int mss)
  17 {
  18         while (skb) {
  19                 if (before(ts_seq, seq + mss)) {
  20                         skb_shinfo(skb)->tx_flags |= SKBTX_SW_TSTAMP;
  21                         skb_shinfo(skb)->tskey = ts_seq;
  22                         return;
  23                 }
  24
  25                 skb = skb->next;
  26                 seq += mss;
  27         }
  28 }
  29
  30 static struct sk_buff *tcp4_gso_segment(struct sk_buff *skb,
  31                                         netdev_features_t features)
  32 {
  33         if (!(skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4))
  34                 return ERR_PTR(-EINVAL);
  35
  36         if (!pskb_may_pull(skb, sizeof(struct tcphdr)))
  37                 return ERR_PTR(-EINVAL);
  38
  39         if (unlikely(skb->ip_summed != CHECKSUM_PARTIAL)) {
  40                 const struct iphdr *iph = ip_hdr(skb);
  41                 struct tcphdr *th = tcp_hdr(skb);
  42
  43                 /* Set up checksum pseudo header, usually expect stack to
  44                  * have done this already.
  45                  */
  46
  47                 th->check = 0;
  48                 skb->ip_summed = CHECKSUM_PARTIAL;
  49                 __tcp_v4_send_check(skb, iph->saddr, iph->daddr);
  50         }
  51
  52         return tcp_gso_segment(skb, features);
  53 }
  54
  55 struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
  56                                 netdev_features_t features)
  57 {
  58         struct sk_buff *segs = ERR_PTR(-EINVAL);
  59         unsigned int sum_truesize = 0;
  60         struct tcphdr *th;
  61         unsigned int thlen;
  62         unsigned int seq;
  63         unsigned int oldlen;
  64         unsigned int mss;
  65         struct sk_buff *gso_skb = skb;
  66         __sum16 newcheck;
  67         bool ooo_okay, copy_destructor;
  68         __wsum delta;
  69
  70         th = tcp_hdr(skb);
  71         thlen = th->doff * 4;
  72         if (thlen < sizeof(*th))
  73                 goto out;
  74
  75         if (!pskb_may_pull(skb, thlen))
  76                 goto out;
  77
  78         oldlen = ~skb->len;
  79         __skb_pull(skb, thlen);
  80
  81         mss = skb_shinfo(skb)->gso_size;
  82         if (unlikely(skb->len <= mss))
  83                 goto out;
  84
  85         if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
  86                 /* Packet is from an untrusted source, reset gso_segs. */
  87
  88                 skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
  89
  90                 segs = NULL;
  91                 goto out;
  92         }
  93
  94         copy_destructor = gso_skb->destructor == tcp_wfree;
  95         ooo_okay = gso_skb->ooo_okay;
  96         /* All segments but the first should have ooo_okay cleared */
  97         skb->ooo_okay = 0;
  98
  99         segs = skb_segment(skb, features);
 100         if (IS_ERR(segs))
 101                 goto out;
 102
 103         /* Only first segment might have ooo_okay set */
 104         segs->ooo_okay = ooo_okay;
 105
 106         /* GSO partial and frag_list segmentation only requires splitting
 107          * the frame into an MSS multiple and possibly a remainder, both
 108          * cases return a GSO skb. So update the mss now.
 109          */
 110         if (skb_is_gso(segs))
 111                 mss *= skb_shinfo(segs)->gso_segs;
 112
 113         delta = (__force __wsum)htonl(oldlen + thlen + mss);
 114
 115         skb = segs;
 116         th = tcp_hdr(skb);
 117         seq = ntohl(th->seq);
 118
 119         if (unlikely(skb_shinfo(gso_skb)->tx_flags & SKBTX_SW_TSTAMP))
 120                 tcp_gso_tstamp(segs, skb_shinfo(gso_skb)->tskey, seq, mss);
 121
 122         newcheck = ~csum_fold(csum_add(csum_unfold(th->check), delta));
 123
 124         while (skb->next) {
 125                 th->fin = th->psh = 0;
 126                 th->check = newcheck;
 127
 128                 if (skb->ip_summed == CHECKSUM_PARTIAL)
 129                         gso_reset_checksum(skb, ~th->check);
 130                 else
 131                         th->check = gso_make_checksum(skb, ~th->check);
 132
 133                 seq += mss;
 134                 if (copy_destructor) {
 135                         skb->destructor = gso_skb->destructor;
 136                         skb->sk = gso_skb->sk;
 137                         sum_truesize += skb->truesize;
 138                 }
 139                 skb = skb->next;
 140                 th = tcp_hdr(skb);
 141
 142                 th->seq = htonl(seq);
 143                 th->cwr = 0;
 144         }
 145
 146         /* Following permits TCP Small Queues to work well with GSO :
 147          * The callback to TCP stack will be called at the time last frag
 148          * is freed at TX completion, and not right now when gso_skb
 149          * is freed by GSO engine
 150          */
 151         if (copy_destructor) {
 152                 int delta;
 153
 154                 swap(gso_skb->sk, skb->sk);
 155                 swap(gso_skb->destructor, skb->destructor);
 156                 sum_truesize += skb->truesize;
 157                 delta = sum_truesize - gso_skb->truesize;
 158                 /* In some pathological cases, delta can be negative.
 159                  * We need to either use refcount_add() or refcount_sub_and_test()
 160                  */
 161                 if (likely(delta >= 0))
 162                         refcount_add(delta, &skb->sk->sk_wmem_alloc);
 163                 else
 164                         WARN_ON_ONCE(refcount_sub_and_test(-delta, &skb->sk->sk_wmem_alloc));
 165         }
 166
 167         delta = (__force __wsum)htonl(oldlen +
 168                                       (skb_tail_pointer(skb) -
 169                                        skb_transport_header(skb)) +
 170                                       skb->data_len);
 171         th->check = ~csum_fold(csum_add(csum_unfold(th->check), delta));
 172         if (skb->ip_summed == CHECKSUM_PARTIAL)
 173                 gso_reset_checksum(skb, ~th->check);
 174         else
 175                 th->check = gso_make_checksum(skb, ~th->check);
 176 out:
 177         return segs;
 178 }
 179
 180 struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb)
 181 {
 182         struct sk_buff *pp = NULL;
 183         struct sk_buff *p;
 184         struct tcphdr *th;
 185         struct tcphdr *th2;
 186         unsigned int len;
 187         unsigned int thlen;
 188         __be32 flags;
 189         unsigned int mss = 1;
 190         unsigned int hlen;
 191         unsigned int off;
 192         int flush = 1;
 193         int i;
 194
 195         off = skb_gro_offset(skb);
 196         hlen = off + sizeof(*th);
 197         th = skb_gro_header(skb, hlen, off);
 198         if (unlikely(!th))
 199                 goto out;
 200
 201         thlen = th->doff * 4;
 202         if (thlen < sizeof(*th))
 203                 goto out;
 204
 205         hlen = off + thlen;
 206         if (skb_gro_header_hard(skb, hlen)) {
 207                 th = skb_gro_header_slow(skb, hlen, off);
 208                 if (unlikely(!th))
 209                         goto out;
 210         }
 211
 212         skb_gro_pull(skb, thlen);
 213
 214         len = skb_gro_len(skb);
 215         flags = tcp_flag_word(th);
 216
 217         list_for_each_entry(p, head, list) {
 218                 if (!NAPI_GRO_CB(p)->same_flow)
 219                         continue;
 220
 221                 th2 = tcp_hdr(p);
 222
 223                 if (*(u32 *)&th->source ^ *(u32 *)&th2->source) {
 224                         NAPI_GRO_CB(p)->same_flow = 0;
 225                         continue;
 226                 }
 227
 228                 goto found;
 229         }
 230         p = NULL;
 231         goto out_check_final;
 232
 233 found:
 234         /* Include the IP ID check below from the inner most IP hdr */
 235         flush = NAPI_GRO_CB(p)->flush;
 236         flush |= (__force int)(flags & TCP_FLAG_CWR);
 237         flush |= (__force int)((flags ^ tcp_flag_word(th2)) &
 238                   ~(TCP_FLAG_CWR | TCP_FLAG_FIN | TCP_FLAG_PSH));
 239         flush |= (__force int)(th->ack_seq ^ th2->ack_seq);
 240         for (i = sizeof(*th); i < thlen; i += 4)
 241                 flush |= *(u32 *)((u8 *)th + i) ^
 242                          *(u32 *)((u8 *)th2 + i);
 243
 244         /* When we receive our second frame we can made a decision on if we
 245          * continue this flow as an atomic flow with a fixed ID or if we use
 246          * an incrementing ID.
 247          */
 248         if (NAPI_GRO_CB(p)->flush_id != 1 ||
 249             NAPI_GRO_CB(p)->count != 1 ||
 250             !NAPI_GRO_CB(p)->is_atomic)
 251                 flush |= NAPI_GRO_CB(p)->flush_id;
 252         else
 253                 NAPI_GRO_CB(p)->is_atomic = false;
 254
 255         mss = skb_shinfo(p)->gso_size;
 256
 257         /* If skb is a GRO packet, make sure its gso_size matches prior packet mss.
 258          * If it is a single frame, do not aggregate it if its length
 259          * is bigger than our mss.
 260          */
 261         if (unlikely(skb_is_gso(skb)))
 262                 flush |= (mss != skb_shinfo(skb)->gso_size);
 263         else
 264                 flush |= (len - 1) >= mss;
 265
 266         flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);
 267 #ifdef CONFIG_TLS_DEVICE
 268         flush |= p->decrypted ^ skb->decrypted;
 269 #endif
 270
 271         if (flush || skb_gro_receive(p, skb)) {
 272                 mss = 1;
 273                 goto out_check_final;
 274         }
 275
 276         tcp_flag_word(th2) |= flags & (TCP_FLAG_FIN | TCP_FLAG_PSH);
 277
 278 out_check_final:
 279         /* Force a flush if last segment is smaller than mss. */
 280         if (unlikely(skb_is_gso(skb)))
 281                 flush = len != NAPI_GRO_CB(skb)->count * skb_shinfo(skb)->gso_size;
 282         else
 283                 flush = len < mss;
 284
 285         flush |= (__force int)(flags & (TCP_FLAG_URG | TCP_FLAG_PSH |
 286                                         TCP_FLAG_RST | TCP_FLAG_SYN |
 287                                         TCP_FLAG_FIN));
 288
 289         if (p && (!NAPI_GRO_CB(skb)->same_flow || flush))
 290                 pp = p;
 291
 292 out:
 293         NAPI_GRO_CB(skb)->flush |= (flush != 0);
 294
 295         return pp;
 296 }
 297
 298 int tcp_gro_complete(struct sk_buff *skb)
 299 {
 300         struct tcphdr *th = tcp_hdr(skb);
 301
 302         skb->csum_start = (unsigned char *)th - skb->head;
 303         skb->csum_offset = offsetof(struct tcphdr, check);
 304         skb->ip_summed = CHECKSUM_PARTIAL;
 305
 306         skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
 307
 308         if (th->cwr)
 309                 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
 310
 311         if (skb->encapsulation)
 312                 skb->inner_transport_header = skb->transport_header;
 313
 314         return 0;
 315 }
 316 EXPORT_SYMBOL(tcp_gro_complete);
 317
 318 INDIRECT_CALLABLE_SCOPE
 319 struct sk_buff *tcp4_gro_receive(struct list_head *head, struct sk_buff *skb)
 320 {
 321         /* Don't bother verifying checksum if we're going to flush anyway. */
 322         if (!NAPI_GRO_CB(skb)->flush &&
 323             skb_gro_checksum_validate(skb, IPPROTO_TCP,
 324                                       inet_gro_compute_pseudo)) {
 325                 NAPI_GRO_CB(skb)->flush = 1;
 326                 return NULL;
 327         }
 328
 329         return tcp_gro_receive(head, skb);
 330 }
 331
 332 INDIRECT_CALLABLE_SCOPE int tcp4_gro_complete(struct sk_buff *skb, int thoff)
 333 {
 334         const struct iphdr *iph = ip_hdr(skb);
 335         struct tcphdr *th = tcp_hdr(skb);
 336
 337         th->check = ~tcp_v4_check(skb->len - thoff, iph->saddr,
 338                                   iph->daddr, 0);
 339         skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4;
 340
 341         if (NAPI_GRO_CB(skb)->is_atomic)
 342                 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_FIXEDID;
 343
 344         return tcp_gro_complete(skb);
 345 }
 346
 347 static const struct net_offload tcpv4_offload = {
 348         .callbacks = {
 349                 .gso_segment    =       tcp4_gso_segment,
 350                 .gro_receive    =       tcp4_gro_receive,
 351                 .gro_complete   =       tcp4_gro_complete,
 352         },
 353 };
 354
 355 int __init tcpv4_offload_init(void)
 356 {
 357         return inet_add_offload(&tcpv4_offload, IPPROTO_TCP);
 358 }