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_SIT |
  61                                SKB_GSO_MPLS |
  62                                SKB_GSO_UDP_TUNNEL |
  63                                0) ||
  64                              !(type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6))))
  65                         goto out;
  66
  67                 skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
  68
  69                 segs = NULL;
  70                 goto out;
  71         }
  72
  73         copy_destructor = gso_skb->destructor == tcp_wfree;
  74         ooo_okay = gso_skb->ooo_okay;
  75         /* All segments but the first should have ooo_okay cleared */
  76         skb->ooo_okay = 0;
  77
  78         segs = skb_segment(skb, features);
  79         if (IS_ERR(segs))
  80                 goto out;
  81
  82         /* Only first segment might have ooo_okay set */
  83         segs->ooo_okay = ooo_okay;
  84
  85         delta = htonl(oldlen + (thlen + mss));
  86
  87         skb = segs;
  88         th = tcp_hdr(skb);
  89         seq = ntohl(th->seq);
  90
  91         newcheck = ~csum_fold((__force __wsum)((__force u32)th->check +
  92                                                (__force u32)delta));
  93
  94         do {
  95                 th->fin = th->psh = 0;
  96                 th->check = newcheck;
  97
  98                 if (skb->ip_summed != CHECKSUM_PARTIAL)
  99                         th->check =
 100                              csum_fold(csum_partial(skb_transport_header(skb),
 101                                                     thlen, skb->csum));
 102
 103                 seq += mss;
 104                 if (copy_destructor) {
 105                         skb->destructor = gso_skb->destructor;
 106                         skb->sk = gso_skb->sk;
 107                         /* {tcp|sock}_wfree() use exact truesize accounting :
 108                          * sum(skb->truesize) MUST be exactly be gso_skb->truesize
 109                          * So we account mss bytes of 'true size' for each segment.
 110                          * The last segment will contain the remaining.
 111                          */
 112                         skb->truesize = mss;
 113                         gso_skb->truesize -= mss;
 114                 }
 115                 skb = skb->next;
 116                 th = tcp_hdr(skb);
 117
 118                 th->seq = htonl(seq);
 119                 th->cwr = 0;
 120         } while (skb->next);
 121
 122         /* Following permits TCP Small Queues to work well with GSO :
 123          * The callback to TCP stack will be called at the time last frag
 124          * is freed at TX completion, and not right now when gso_skb
 125          * is freed by GSO engine
 126          */
 127         if (copy_destructor) {
 128                 swap(gso_skb->sk, skb->sk);
 129                 swap(gso_skb->destructor, skb->destructor);
 130                 swap(gso_skb->truesize, skb->truesize);
 131         }
 132
 133         delta = htonl(oldlen + (skb_tail_pointer(skb) -
 134                                 skb_transport_header(skb)) +
 135                       skb->data_len);
 136         th->check = ~csum_fold((__force __wsum)((__force u32)th->check +
 137                                 (__force u32)delta));
 138         if (skb->ip_summed != CHECKSUM_PARTIAL)
 139                 th->check = csum_fold(csum_partial(skb_transport_header(skb),
 140                                                    thlen, skb->csum));
 141 out:
 142         return segs;
 143 }
 144 EXPORT_SYMBOL(tcp_gso_segment);
 145
 146 struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb)
 147 {
 148         struct sk_buff **pp = NULL;
 149         struct sk_buff *p;
 150         struct tcphdr *th;
 151         struct tcphdr *th2;
 152         unsigned int len;
 153         unsigned int thlen;
 154         __be32 flags;
 155         unsigned int mss = 1;
 156         unsigned int hlen;
 157         unsigned int off;
 158         int flush = 1;
 159         int i;
 160
 161         off = skb_gro_offset(skb);
 162         hlen = off + sizeof(*th);
 163         th = skb_gro_header_fast(skb, off);
 164         if (skb_gro_header_hard(skb, hlen)) {
 165                 th = skb_gro_header_slow(skb, hlen, off);
 166                 if (unlikely(!th))
 167                         goto out;
 168         }
 169
 170         thlen = th->doff * 4;
 171         if (thlen < sizeof(*th))
 172                 goto out;
 173
 174         hlen = off + thlen;
 175         if (skb_gro_header_hard(skb, hlen)) {
 176                 th = skb_gro_header_slow(skb, hlen, off);
 177                 if (unlikely(!th))
 178                         goto out;
 179         }
 180
 181         skb_gro_pull(skb, thlen);
 182
 183         len = skb_gro_len(skb);
 184         flags = tcp_flag_word(th);
 185
 186         for (; (p = *head); head = &p->next) {
 187                 if (!NAPI_GRO_CB(p)->same_flow)
 188                         continue;
 189
 190                 th2 = tcp_hdr(p);
 191
 192                 if (*(u32 *)&th->source ^ *(u32 *)&th2->source) {
 193                         NAPI_GRO_CB(p)->same_flow = 0;
 194                         continue;
 195                 }
 196
 197                 goto found;
 198         }
 199
 200         goto out_check_final;
 201
 202 found:
 203         flush = NAPI_GRO_CB(p)->flush;
 204         flush |= (__force int)(flags & TCP_FLAG_CWR);
 205         flush |= (__force int)((flags ^ tcp_flag_word(th2)) &
 206                   ~(TCP_FLAG_CWR | TCP_FLAG_FIN | TCP_FLAG_PSH));
 207         flush |= (__force int)(th->ack_seq ^ th2->ack_seq);
 208         for (i = sizeof(*th); i < thlen; i += 4)
 209                 flush |= *(u32 *)((u8 *)th + i) ^
 210                          *(u32 *)((u8 *)th2 + i);
 211
 212         mss = tcp_skb_mss(p);
 213
 214         flush |= (len - 1) >= mss;
 215         flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);
 216
 217         if (flush || skb_gro_receive(head, skb)) {
 218                 mss = 1;
 219                 goto out_check_final;
 220         }
 221
 222         p = *head;
 223         th2 = tcp_hdr(p);
 224         tcp_flag_word(th2) |= flags & (TCP_FLAG_FIN | TCP_FLAG_PSH);
 225
 226 out_check_final:
 227         flush = len < mss;
 228         flush |= (__force int)(flags & (TCP_FLAG_URG | TCP_FLAG_PSH |
 229                                         TCP_FLAG_RST | TCP_FLAG_SYN |
 230                                         TCP_FLAG_FIN));
 231
 232         if (p && (!NAPI_GRO_CB(skb)->same_flow || flush))
 233                 pp = head;
 234
 235 out:
 236         NAPI_GRO_CB(skb)->flush |= flush;
 237
 238         return pp;
 239 }
 240 EXPORT_SYMBOL(tcp_gro_receive);
 241
 242 int tcp_gro_complete(struct sk_buff *skb)
 243 {
 244         struct tcphdr *th = tcp_hdr(skb);
 245
 246         skb->csum_start = skb_transport_header(skb) - skb->head;
 247         skb->csum_offset = offsetof(struct tcphdr, check);
 248         skb->ip_summed = CHECKSUM_PARTIAL;
 249
 250         skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
 251
 252         if (th->cwr)
 253                 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
 254
 255         return 0;
 256 }
 257 EXPORT_SYMBOL(tcp_gro_complete);
 258
 259 static int tcp_v4_gso_send_check(struct sk_buff *skb)
 260 {
 261         const struct iphdr *iph;
 262         struct tcphdr *th;
 263
 264         if (!pskb_may_pull(skb, sizeof(*th)))
 265                 return -EINVAL;
 266
 267         iph = ip_hdr(skb);
 268         th = tcp_hdr(skb);
 269
 270         th->check = 0;
 271         skb->ip_summed = CHECKSUM_PARTIAL;
 272         __tcp_v4_send_check(skb, iph->saddr, iph->daddr);
 273         return 0;
 274 }
 275
 276 static struct sk_buff **tcp4_gro_receive(struct sk_buff **head, struct sk_buff *skb)
 277 {
 278         const struct iphdr *iph = skb_gro_network_header(skb);
 279         __wsum wsum;
 280         __sum16 sum;
 281
 282         switch (skb->ip_summed) {
 283         case CHECKSUM_COMPLETE:
 284                 if (!tcp_v4_check(skb_gro_len(skb), iph->saddr, iph->daddr,
 285                                   skb->csum)) {
 286                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 287                         break;
 288                 }
 289 flush:
 290                 NAPI_GRO_CB(skb)->flush = 1;
 291                 return NULL;
 292
 293         case CHECKSUM_NONE:
 294                 wsum = csum_tcpudp_nofold(iph->saddr, iph->daddr,
 295                                           skb_gro_len(skb), IPPROTO_TCP, 0);
 296                 sum = csum_fold(skb_checksum(skb,
 297                                              skb_gro_offset(skb),
 298                                              skb_gro_len(skb),
 299                                              wsum));
 300                 if (sum)
 301                         goto flush;
 302
 303                 skb->ip_summed = CHECKSUM_UNNECESSARY;
 304                 break;
 305         }
 306
 307         return tcp_gro_receive(head, skb);
 308 }
 309
 310 static int tcp4_gro_complete(struct sk_buff *skb)
 311 {
 312         const struct iphdr *iph = ip_hdr(skb);
 313         struct tcphdr *th = tcp_hdr(skb);
 314
 315         th->check = ~tcp_v4_check(skb->len - skb_transport_offset(skb),
 316                                   iph->saddr, iph->daddr, 0);
 317         skb_shinfo(skb)->gso_type = SKB_GSO_TCPV4;
 318
 319         return tcp_gro_complete(skb);
 320 }
 321
 322 static const struct net_offload tcpv4_offload = {
 323         .callbacks = {
 324                 .gso_send_check =       tcp_v4_gso_send_check,
 325                 .gso_segment    =       tcp_gso_segment,
 326                 .gro_receive    =       tcp4_gro_receive,
 327                 .gro_complete   =       tcp4_gro_complete,
 328         },
 329 };
 330
 331 int __init tcpv4_offload_init(void)
 332 {
 333         return inet_add_offload(&tcpv4_offload, IPPROTO_TCP);
 334 }