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 struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
  18                                 netdev_features_t features)
  19 {
  20         struct sk_buff *segs = ERR_PTR(-EINVAL);
  21         struct tcphdr *th;
  22         unsigned int thlen;
  23         unsigned int seq;
  24         __be32 delta;
  25         unsigned int oldlen;
  26         unsigned int mss;
  27         struct sk_buff *gso_skb = skb;
  28         __sum16 newcheck;
  29         bool ooo_okay, copy_destructor;
  30
  31         if (!pskb_may_pull(skb, sizeof(*th)))
  32                 goto out;
  33
  34         th = tcp_hdr(skb);
  35         thlen = th->doff * 4;
  36         if (thlen < sizeof(*th))
  37                 goto out;
  38
  39         if (!pskb_may_pull(skb, thlen))
  40                 goto out;
  41
  42         oldlen = (u16)~skb->len;
  43         __skb_pull(skb, thlen);
  44
  45         mss = tcp_skb_mss(skb);
  46         if (unlikely(skb->len <= mss))
  47                 goto out;
  48
  49         if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
  50                 /* Packet is from an untrusted source, reset gso_segs. */
  51                 int type = skb_shinfo(skb)->gso_type;
  52
  53                 if (unlikely(type &
  54                              ~(SKB_GSO_TCPV4 |
  55                                SKB_GSO_DODGY |
  56                                SKB_GSO_TCP_ECN |
  57                                SKB_GSO_TCPV6 |
  58                                SKB_GSO_GRE |
  59                                SKB_GSO_IPIP |
  60                                SKB_GSO_MPLS |
  61                                SKB_GSO_UDP_TUNNEL |
  62                                0) ||
  63                              !(type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6))))
  64                         goto out;
  65
  66                 skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
  67
  68                 segs = NULL;
  69                 goto out;
  70         }
  71
  72         copy_destructor = gso_skb->destructor == tcp_wfree;
  73         ooo_okay = gso_skb->ooo_okay;
  74         /* All segments but the first should have ooo_okay cleared */
  75         skb->ooo_okay = 0;
  76
  77         segs = skb_segment(skb, features);
  78         if (IS_ERR(segs))
  79                 goto out;
  80
  81         /* Only first segment might have ooo_okay set */
  82         segs->ooo_okay = ooo_okay;
  83
  84         delta = htonl(oldlen + (thlen + mss));
  85
  86         skb = segs;
  87         th = tcp_hdr(skb);
  88         seq = ntohl(th->seq);
  89
  90         newcheck = ~csum_fold((__force __wsum)((__force u32)th->check +
  91                                                (__force u32)delta));
  92
  93         do {
  94                 th->fin = th->psh = 0;
  95                 th->check = newcheck;
  96
  97                 if (skb->ip_summed != CHECKSUM_PARTIAL)
  98                         th->check =
  99                              csum_fold(csum_partial(skb_transport_header(skb),
 100                                                     thlen, skb->csum));
 101
 102                 seq += mss;
 103                 if (copy_destructor) {
 104                         skb->destructor = gso_skb->destructor;
 105                         skb->sk = gso_skb->sk;
 106                         /* {tcp|sock}_wfree() use exact truesize accounting :
 107                          * sum(skb->truesize) MUST be exactly be gso_skb->truesize
 108                          * So we account mss bytes of 'true size' for each segment.
 109                          * The last segment will contain the remaining.
 110                          */
 111                         skb->truesize = mss;
 112                         gso_skb->truesize -= mss;
 113                 }
 114                 skb = skb->next;
 115                 th = tcp_hdr(skb);
 116
 117                 th->seq = htonl(seq);
 118                 th->cwr = 0;
 119         } while (skb->next);
 120
 121         /* Following permits TCP Small Queues to work well with GSO :
 122          * The callback to TCP stack will be called at the time last frag
 123          * is freed at TX completion, and not right now when gso_skb
 124          * is freed by GSO engine
 125          */
 126         if (copy_destructor) {
 127                 swap(gso_skb->sk, skb->sk);
 128                 swap(gso_skb->destructor, skb->destructor);
 129                 swap(gso_skb->truesize, skb->truesize);
 130         }
 131
 132         delta = htonl(oldlen + (skb_tail_pointer(skb) -
 133                                 skb_transport_header(skb)) +
 134                       skb->data_len);
 135         th->check = ~csum_fold((__force __wsum)((__force u32)th->check +
 136                                 (__force u32)delta));
 137         if (skb->ip_summed != CHECKSUM_PARTIAL)
 138                 th->check = csum_fold(csum_partial(skb_transport_header(skb),
 139                                                    thlen, skb->csum));
 140 out:
 141         return segs;
 142 }
 143 EXPORT_SYMBOL(tcp_gso_segment);
 144
 145 struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb)
 146 {
 147         struct sk_buff **pp = NULL;
 148         struct sk_buff *p;
 149         struct tcphdr *th;
 150         struct tcphdr *th2;
 151         unsigned int len;
 152         unsigned int thlen;
 153         __be32 flags;
 154         unsigned int mss = 1;
 155         unsigned int hlen;
 156         unsigned int off;
 157         int flush = 1;
 158         int i;
 159
 160         off = skb_gro_offset(skb);
 161         hlen = off + sizeof(*th);
 162         th = skb_gro_header_fast(skb, off);
 163         if (skb_gro_header_hard(skb, hlen)) {
 164                 th = skb_gro_header_slow(skb, hlen, off);
 165                 if (unlikely(!th))
 166                         goto out;
 167         }
 168
 169         thlen = th->doff * 4;
 170         if (thlen < sizeof(*th))
 171                 goto out;
 172
 173         hlen = off + thlen;
 174         if (skb_gro_header_hard(skb, hlen)) {
 175                 th = skb_gro_header_slow(skb, hlen, off);
 176                 if (unlikely(!th))
 177                         goto out;
 178         }
 179
 180         skb_gro_pull(skb, thlen);
 181
 182         len = skb_gro_len(skb);
 183         flags = tcp_flag_word(th);
 184
 185         for (; (p = *head); head = &p->next) {
 186                 if (!NAPI_GRO_CB(p)->same_flow)
 187                         continue;
 188
 189                 th2 = tcp_hdr(p);
 190
 191                 if (*(u32 *)&th->source ^ *(u32 *)&th2->source) {
 192                         NAPI_GRO_CB(p)->same_flow = 0;
 193                         continue;
 194                 }
 195
 196                 goto found;
 197         }
 198
 199         goto out_check_final;
 200
 201 found:
 202         flush = NAPI_GRO_CB(p)->flush;
 203         flush |= (__force int)(flags & TCP_FLAG_CWR);
 204         flush |= (__force int)((flags ^ tcp_flag_word(th2)) &
 205                   ~(TCP_FLAG_CWR | TCP_FLAG_FIN | TCP_FLAG_PSH));
 206         flush |= (__force int)(th->ack_seq ^ th2->ack_seq);
 207         for (i = sizeof(*th); i < thlen; i += 4)
 208                 flush |= *(u32 *)((u8 *)th + i) ^
 209                          *(u32 *)((u8 *)th2 + i);
 210
 211         mss = tcp_skb_mss(p);
 212
 213         flush |= (len - 1) >= mss;
 214         flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);
 215
 216         if (flush || skb_gro_receive(head, skb)) {
 217                 mss = 1;
 218                 goto out_check_final;
 219         }
 220
 221         p = *head;
 222         th2 = tcp_hdr(p);
 223         tcp_flag_word(th2) |= flags & (TCP_FLAG_FIN | TCP_FLAG_PSH);
 224
 225 out_check_final:
 226         flush = len < mss;
 227         flush |= (__force int)(flags & (TCP_FLAG_URG | TCP_FLAG_PSH |
 228                                         TCP_FLAG_RST | TCP_FLAG_SYN |
 229                                         TCP_FLAG_FIN));
 230
 231         if (p && (!NAPI_GRO_CB(skb)->same_flow || flush))
 232                 pp = head;
 233
 234 out:
 235         NAPI_GRO_CB(skb)->flush |= flush;
 236
 237         return pp;
 238 }
 239 EXPORT_SYMBOL(tcp_gro_receive);
 240
 241 int tcp_gro_complete(struct sk_buff *skb)
 242 {
 243         struct tcphdr *th = tcp_hdr(skb);
 244
 245         skb->csum_start = skb_transport_header(skb) - skb->head;
 246         skb->csum_offset = offsetof(struct tcphdr, check);
 247         skb->ip_summed = CHECKSUM_PARTIAL;
 248
 249         skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
 250
 251         if (th->cwr)
 252                 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
 253
 254         return 0;
 255 }
 256 EXPORT_SYMBOL(tcp_gro_complete);
 257
 258 static int tcp_v4_gso_send_check(struct sk_buff *skb)
 259 {
 260         const struct iphdr *iph;
 261         struct tcphdr *th;
 262
 263         if (!pskb_may_pull(skb, sizeof(*th)))
 264                 return -EINVAL;
 265
 266         iph = ip_hdr(skb);
 267         th = tcp_hdr(skb);
 268
 269         th->check = 0;
 270         skb->ip_summed = CHECKSUM_PARTIAL;
 271         __tcp_v4_send_check(skb, iph->saddr, iph->daddr);
 272         return 0;
 273 }
 274
 275 static struct sk_buff **tcp4_gro_receive(struct sk_buff **head, struct sk_buff *skb)
 276 {
 277         const struct iphdr *iph = skb_gro_network_header(skb);
 278         __wsum wsum;
 279         __sum16 sum;
 280
 281         switch (skb->ip_summed) {
 282         case CHECKSUM_COMPLETE:
 283                 if (!tcp_v4_check(skb_gro_len(skb), iph->saddr, iph->daddr,
 284                                   skb->csum)) {
 285                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 286                         break;
 287                 }
 288 flush:
 289                 NAPI_GRO_CB(skb)->flush = 1;
 290                 return NULL;
 291
 292         case CHECKSUM_NONE:
 293                 wsum = csum_tcpudp_nofold(iph->saddr, iph->daddr,
 294                                           skb_gro_len(skb), IPPROTO_TCP, 0);
 295                 sum = csum_fold(skb_checksum(skb,
 296                                              skb_gro_offset(skb),
 297                                              skb_gro_len(skb),
 298                                              wsum));
 299                 if (sum)
 300                         goto flush;
 301
 302                 skb->ip_summed = CHECKSUM_UNNECESSARY;
 303                 break;
 304         }
 305
 306         return tcp_gro_receive(head, skb);
 307 }
 308
 309 static int tcp4_gro_complete(struct sk_buff *skb)
 310 {
 311         const struct iphdr *iph = ip_hdr(skb);
 312         struct tcphdr *th = tcp_hdr(skb);
 313
 314         th->check = ~tcp_v4_check(skb->len - skb_transport_offset(skb),
 315                                   iph->saddr, iph->daddr, 0);
 316         skb_shinfo(skb)->gso_type = SKB_GSO_TCPV4;
 317
 318         return tcp_gro_complete(skb);
 319 }
 320
 321 static const struct net_offload tcpv4_offload = {
 322         .callbacks = {
 323                 .gso_send_check =       tcp_v4_gso_send_check,
 324                 .gso_segment    =       tcp_gso_segment,
 325                 .gro_receive    =       tcp4_gro_receive,
 326                 .gro_complete   =       tcp4_gro_complete,
 327         },
 328 };
 329
 330 int __init tcpv4_offload_init(void)
 331 {
 332         return inet_add_offload(&tcpv4_offload, IPPROTO_TCP);
 333 }