net/ipv4/tcp_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  *      TCPv4 GSO/GRO support
  11  */
  12
  13 #include <linux/skbuff.h>
  14 #include <net/tcp.h>
  15 #include <net/protocol.h>
  16
  17 static void tcp_gso_tstamp(struct sk_buff *skb, unsigned int ts_seq,
  18                            unsigned int seq, unsigned int mss)
  19 {
  20         while (skb) {
  21                 if (before(ts_seq, seq + mss)) {
  22                         skb_shinfo(skb)->tx_flags |= SKBTX_SW_TSTAMP;
  23                         skb_shinfo(skb)->tskey = ts_seq;
  24                         return;
  25                 }
  26
  27                 skb = skb->next;
  28                 seq += mss;
  29         }
  30 }
  31
  32 static struct sk_buff *tcp4_gso_segment(struct sk_buff *skb,
  33                                         netdev_features_t features)
  34 {
  35         if (!(skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4))
  36                 return ERR_PTR(-EINVAL);
  37
  38         if (!pskb_may_pull(skb, sizeof(struct tcphdr)))
  39                 return ERR_PTR(-EINVAL);
  40
  41         if (unlikely(skb->ip_summed != CHECKSUM_PARTIAL)) {
  42                 const struct iphdr *iph = ip_hdr(skb);
  43                 struct tcphdr *th = tcp_hdr(skb);
  44
  45                 /* Set up checksum pseudo header, usually expect stack to
  46                  * have done this already.
  47                  */
  48
  49                 th->check = 0;
  50                 skb->ip_summed = CHECKSUM_PARTIAL;
  51                 __tcp_v4_send_check(skb, iph->saddr, iph->daddr);
  52         }
  53
  54         return tcp_gso_segment(skb, features);
  55 }
  56
  57 struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
  58                                 netdev_features_t features)
  59 {
  60         struct sk_buff *segs = ERR_PTR(-EINVAL);
  61         unsigned int sum_truesize = 0;
  62         struct tcphdr *th;
  63         unsigned int thlen;
  64         unsigned int seq;
  65         __be32 delta;
  66         unsigned int oldlen;
  67         unsigned int mss;
  68         struct sk_buff *gso_skb = skb;
  69         __sum16 newcheck;
  70         bool ooo_okay, copy_destructor;
  71
  72         th = tcp_hdr(skb);
  73         thlen = th->doff * 4;
  74         if (thlen < sizeof(*th))
  75                 goto out;
  76
  77         if (!pskb_may_pull(skb, thlen))
  78                 goto out;
  79
  80         oldlen = (u16)~skb->len;
  81         __skb_pull(skb, thlen);
  82
  83         mss = skb_shinfo(skb)->gso_size;
  84         if (unlikely(skb->len <= mss))
  85                 goto out;
  86
  87         if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
  88                 /* Packet is from an untrusted source, reset gso_segs. */
  89
  90                 skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
  91
  92                 segs = NULL;
  93                 goto out;
  94         }
  95
  96         copy_destructor = gso_skb->destructor == tcp_wfree;
  97         ooo_okay = gso_skb->ooo_okay;
  98         /* All segments but the first should have ooo_okay cleared */
  99         skb->ooo_okay = 0;
 100
 101         segs = skb_segment(skb, features);
 102         if (IS_ERR(segs))
 103                 goto out;
 104
 105         /* Only first segment might have ooo_okay set */
 106         segs->ooo_okay = ooo_okay;
 107
 108         /* GSO partial and frag_list segmentation only requires splitting
 109          * the frame into an MSS multiple and possibly a remainder, both
 110          * cases return a GSO skb. So update the mss now.
 111          */
 112         if (skb_is_gso(segs))
 113                 mss *= skb_shinfo(segs)->gso_segs;
 114
 115         delta = htonl(oldlen + (thlen + mss));
 116
 117         skb = segs;
 118         th = tcp_hdr(skb);
 119         seq = ntohl(th->seq);
 120
 121         if (unlikely(skb_shinfo(gso_skb)->tx_flags & SKBTX_SW_TSTAMP))
 122                 tcp_gso_tstamp(segs, skb_shinfo(gso_skb)->tskey, seq, mss);
 123
 124         newcheck = ~csum_fold((__force __wsum)((__force u32)th->check +
 125                                                (__force u32)delta));
 126
 127         while (skb->next) {
 128                 th->fin = th->psh = 0;
 129                 th->check = newcheck;
 130
 131                 if (skb->ip_summed == CHECKSUM_PARTIAL)
 132                         gso_reset_checksum(skb, ~th->check);
 133                 else
 134                         th->check = gso_make_checksum(skb, ~th->check);
 135
 136                 seq += mss;
 137                 if (copy_destructor) {
 138                         skb->destructor = gso_skb->destructor;
 139                         skb->sk = gso_skb->sk;
 140                         sum_truesize += skb->truesize;
 141                 }
 142                 skb = skb->next;
 143                 th = tcp_hdr(skb);
 144
 145                 th->seq = htonl(seq);
 146                 th->cwr = 0;
 147         }
 148
 149         /* Following permits TCP Small Queues to work well with GSO :
 150          * The callback to TCP stack will be called at the time last frag
 151          * is freed at TX completion, and not right now when gso_skb
 152          * is freed by GSO engine
 153          */
 154         if (copy_destructor) {
 155                 int delta;
 156
 157                 swap(gso_skb->sk, skb->sk);
 158                 swap(gso_skb->destructor, skb->destructor);
 159                 sum_truesize += skb->truesize;
 160                 delta = sum_truesize - gso_skb->truesize;
 161                 /* In some pathological cases, delta can be negative.
 162                  * We need to either use refcount_add() or refcount_sub_and_test()
 163                  */
 164                 if (likely(delta >= 0))
 165                         refcount_add(delta, &skb->sk->sk_wmem_alloc);
 166                 else
 167                         WARN_ON_ONCE(refcount_sub_and_test(-delta, &skb->sk->sk_wmem_alloc));
 168         }
 169
 170         delta = htonl(oldlen + (skb_tail_pointer(skb) -
 171                                 skb_transport_header(skb)) +
 172                       skb->data_len);
 173         th->check = ~csum_fold((__force __wsum)((__force u32)th->check +
 174                                 (__force u32)delta));
 175         if (skb->ip_summed == CHECKSUM_PARTIAL)
 176                 gso_reset_checksum(skb, ~th->check);
 177         else
 178                 th->check = gso_make_checksum(skb, ~th->check);
 179 out:
 180         return segs;
 181 }
 182
 183 struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb)
 184 {
 185         struct sk_buff **pp = NULL;
 186         struct sk_buff *p;
 187         struct tcphdr *th;
 188         struct tcphdr *th2;
 189         unsigned int len;
 190         unsigned int thlen;
 191         __be32 flags;
 192         unsigned int mss = 1;
 193         unsigned int hlen;
 194         unsigned int off;
 195         int flush = 1;
 196         int i;
 197
 198         off = skb_gro_offset(skb);
 199         hlen = off + sizeof(*th);
 200         th = skb_gro_header_fast(skb, off);
 201         if (skb_gro_header_hard(skb, hlen)) {
 202                 th = skb_gro_header_slow(skb, hlen, off);
 203                 if (unlikely(!th))
 204                         goto out;
 205         }
 206
 207         thlen = th->doff * 4;
 208         if (thlen < sizeof(*th))
 209                 goto out;
 210
 211         hlen = off + thlen;
 212         if (skb_gro_header_hard(skb, hlen)) {
 213                 th = skb_gro_header_slow(skb, hlen, off);
 214                 if (unlikely(!th))
 215                         goto out;
 216         }
 217
 218         skb_gro_pull(skb, thlen);
 219
 220         len = skb_gro_len(skb);
 221         flags = tcp_flag_word(th);
 222
 223         for (; (p = *head); head = &p->next) {
 224                 if (!NAPI_GRO_CB(p)->same_flow)
 225                         continue;
 226
 227                 th2 = tcp_hdr(p);
 228
 229                 if (*(u32 *)&th->source ^ *(u32 *)&th2->source) {
 230                         NAPI_GRO_CB(p)->same_flow = 0;
 231                         continue;
 232                 }
 233
 234                 goto found;
 235         }
 236
 237         goto out_check_final;
 238
 239 found:
 240         /* Include the IP ID check below from the inner most IP hdr */
 241         flush = NAPI_GRO_CB(p)->flush;
 242         flush |= (__force int)(flags & TCP_FLAG_CWR);
 243         flush |= (__force int)((flags ^ tcp_flag_word(th2)) &
 244                   ~(TCP_FLAG_CWR | TCP_FLAG_FIN | TCP_FLAG_PSH));
 245         flush |= (__force int)(th->ack_seq ^ th2->ack_seq);
 246         for (i = sizeof(*th); i < thlen; i += 4)
 247                 flush |= *(u32 *)((u8 *)th + i) ^
 248                          *(u32 *)((u8 *)th2 + i);
 249
 250         /* When we receive our second frame we can made a decision on if we
 251          * continue this flow as an atomic flow with a fixed ID or if we use
 252          * an incrementing ID.
 253          */
 254         if (NAPI_GRO_CB(p)->flush_id != 1 ||
 255             NAPI_GRO_CB(p)->count != 1 ||
 256             !NAPI_GRO_CB(p)->is_atomic)
 257                 flush |= NAPI_GRO_CB(p)->flush_id;
 258         else
 259                 NAPI_GRO_CB(p)->is_atomic = false;
 260
 261         mss = skb_shinfo(p)->gso_size;
 262
 263         flush |= (len - 1) >= mss;
 264         flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);
 265
 266         if (flush || skb_gro_receive(head, skb)) {
 267                 mss = 1;
 268                 goto out_check_final;
 269         }
 270
 271         p = *head;
 272         th2 = tcp_hdr(p);
 273         tcp_flag_word(th2) |= flags & (TCP_FLAG_FIN | TCP_FLAG_PSH);
 274
 275 out_check_final:
 276         flush = len < mss;
 277         flush |= (__force int)(flags & (TCP_FLAG_URG | TCP_FLAG_PSH |
 278                                         TCP_FLAG_RST | TCP_FLAG_SYN |
 279                                         TCP_FLAG_FIN));
 280
 281         if (p && (!NAPI_GRO_CB(skb)->same_flow || flush))
 282                 pp = head;
 283
 284 out:
 285         NAPI_GRO_CB(skb)->flush |= (flush != 0);
 286
 287         return pp;
 288 }
 289
 290 int tcp_gro_complete(struct sk_buff *skb)
 291 {
 292         struct tcphdr *th = tcp_hdr(skb);
 293
 294         skb->csum_start = (unsigned char *)th - skb->head;
 295         skb->csum_offset = offsetof(struct tcphdr, check);
 296         skb->ip_summed = CHECKSUM_PARTIAL;
 297
 298         skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
 299
 300         if (th->cwr)
 301                 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
 302
 303         return 0;
 304 }
 305 EXPORT_SYMBOL(tcp_gro_complete);
 306
 307 static struct sk_buff **tcp4_gro_receive(struct sk_buff **head, struct sk_buff *skb)
 308 {
 309         /* Don't bother verifying checksum if we're going to flush anyway. */
 310         if (!NAPI_GRO_CB(skb)->flush &&
 311             skb_gro_checksum_validate(skb, IPPROTO_TCP,
 312                                       inet_gro_compute_pseudo)) {
 313                 NAPI_GRO_CB(skb)->flush = 1;
 314                 return NULL;
 315         }
 316
 317         return tcp_gro_receive(head, skb);
 318 }
 319
 320 static int tcp4_gro_complete(struct sk_buff *skb, int thoff)
 321 {
 322         const struct iphdr *iph = ip_hdr(skb);
 323         struct tcphdr *th = tcp_hdr(skb);
 324
 325         th->check = ~tcp_v4_check(skb->len - thoff, iph->saddr,
 326                                   iph->daddr, 0);
 327         skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4;
 328
 329         if (NAPI_GRO_CB(skb)->is_atomic)
 330                 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_FIXEDID;
 331
 332         return tcp_gro_complete(skb);
 333 }
 334
 335 static const struct net_offload tcpv4_offload = {
 336         .callbacks = {
 337                 .gso_segment    =       tcp4_gso_segment,
 338                 .gro_receive    =       tcp4_gro_receive,
 339                 .gro_complete   =       tcp4_gro_complete,
 340         },
 341 };
 342
 343 int __init tcpv4_offload_init(void)
 344 {
 345         return inet_add_offload(&tcpv4_offload, IPPROTO_TCP);
 346 }