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