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 (!pskb_may_pull(skb, sizeof(struct tcphdr)))
  36                 return ERR_PTR(-EINVAL);
  37
  38         if (unlikely(skb->ip_summed != CHECKSUM_PARTIAL)) {
  39                 const struct iphdr *iph = ip_hdr(skb);
  40                 struct tcphdr *th = tcp_hdr(skb);
  41
  42                 /* Set up checksum pseudo header, usually expect stack to
  43                  * have done this already.
  44                  */
  45
  46                 th->check = 0;
  47                 skb->ip_summed = CHECKSUM_PARTIAL;
  48                 __tcp_v4_send_check(skb, iph->saddr, iph->daddr);
  49         }
  50
  51         return tcp_gso_segment(skb, features);
  52 }
  53
  54 struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
  55                                 netdev_features_t features)
  56 {
  57         struct sk_buff *segs = ERR_PTR(-EINVAL);
  58         unsigned int sum_truesize = 0;
  59         struct tcphdr *th;
  60         unsigned int thlen;
  61         unsigned int seq;
  62         __be32 delta;
  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
  69         th = tcp_hdr(skb);
  70         thlen = th->doff * 4;
  71         if (thlen < sizeof(*th))
  72                 goto out;
  73
  74         if (!pskb_may_pull(skb, thlen))
  75                 goto out;
  76
  77         oldlen = (u16)~skb->len;
  78         __skb_pull(skb, thlen);
  79
  80         mss = skb_shinfo(skb)->gso_size;
  81         if (unlikely(skb->len <= mss))
  82                 goto out;
  83
  84         if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
  85                 /* Packet is from an untrusted source, reset gso_segs. */
  86                 int type = skb_shinfo(skb)->gso_type;
  87
  88                 if (unlikely(type &
  89                              ~(SKB_GSO_TCPV4 |
  90                                SKB_GSO_DODGY |
  91                                SKB_GSO_TCP_ECN |
  92                                SKB_GSO_TCP_FIXEDID |
  93                                SKB_GSO_TCPV6 |
  94                                SKB_GSO_GRE |
  95                                SKB_GSO_GRE_CSUM |
  96                                SKB_GSO_IPIP |
  97                                SKB_GSO_SIT |
  98                                SKB_GSO_UDP_TUNNEL |
  99                                SKB_GSO_UDP_TUNNEL_CSUM |
 100                                SKB_GSO_TUNNEL_REMCSUM |
 101                                0) ||
 102                              !(type & (SKB_GSO_TCPV4 |
 103                                        SKB_GSO_TCPV6))))
 104                         goto out;
 105
 106                 skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
 107
 108                 segs = NULL;
 109                 goto out;
 110         }
 111
 112         /* GSO partial only requires splitting the frame into an MSS
 113          * multiple and possibly a remainder.  So update the mss now.
 114          */
 115         if (features & NETIF_F_GSO_PARTIAL)
 116                 mss = skb->len - (skb->len % mss);
 117
 118         copy_destructor = gso_skb->destructor == tcp_wfree;
 119         ooo_okay = gso_skb->ooo_okay;
 120         /* All segments but the first should have ooo_okay cleared */
 121         skb->ooo_okay = 0;
 122
 123         segs = skb_segment(skb, features);
 124         if (IS_ERR(segs))
 125                 goto out;
 126
 127         /* Only first segment might have ooo_okay set */
 128         segs->ooo_okay = ooo_okay;
 129
 130         delta = htonl(oldlen + (thlen + mss));
 131
 132         skb = segs;
 133         th = tcp_hdr(skb);
 134         seq = ntohl(th->seq);
 135
 136         if (unlikely(skb_shinfo(gso_skb)->tx_flags & SKBTX_SW_TSTAMP))
 137                 tcp_gso_tstamp(segs, skb_shinfo(gso_skb)->tskey, seq, mss);
 138
 139         newcheck = ~csum_fold((__force __wsum)((__force u32)th->check +
 140                                                (__force u32)delta));
 141
 142         while (skb->next) {
 143                 th->fin = th->psh = 0;
 144                 th->check = newcheck;
 145
 146                 if (skb->ip_summed == CHECKSUM_PARTIAL)
 147                         gso_reset_checksum(skb, ~th->check);
 148                 else
 149                         th->check = gso_make_checksum(skb, ~th->check);
 150
 151                 seq += mss;
 152                 if (copy_destructor) {
 153                         skb->destructor = gso_skb->destructor;
 154                         skb->sk = gso_skb->sk;
 155                         sum_truesize += skb->truesize;
 156                 }
 157                 skb = skb->next;
 158                 th = tcp_hdr(skb);
 159
 160                 th->seq = htonl(seq);
 161                 th->cwr = 0;
 162         }
 163
 164         /* Following permits TCP Small Queues to work well with GSO :
 165          * The callback to TCP stack will be called at the time last frag
 166          * is freed at TX completion, and not right now when gso_skb
 167          * is freed by GSO engine
 168          */
 169         if (copy_destructor) {
 170                 swap(gso_skb->sk, skb->sk);
 171                 swap(gso_skb->destructor, skb->destructor);
 172                 sum_truesize += skb->truesize;
 173                 atomic_add(sum_truesize - gso_skb->truesize,
 174                            &skb->sk->sk_wmem_alloc);
 175         }
 176
 177         delta = htonl(oldlen + (skb_tail_pointer(skb) -
 178                                 skb_transport_header(skb)) +
 179                       skb->data_len);
 180         th->check = ~csum_fold((__force __wsum)((__force u32)th->check +
 181                                 (__force u32)delta));
 182         if (skb->ip_summed == CHECKSUM_PARTIAL)
 183                 gso_reset_checksum(skb, ~th->check);
 184         else
 185                 th->check = gso_make_checksum(skb, ~th->check);
 186 out:
 187         return segs;
 188 }
 189
 190 struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb)
 191 {
 192         struct sk_buff **pp = NULL;
 193         struct sk_buff *p;
 194         struct tcphdr *th;
 195         struct tcphdr *th2;
 196         unsigned int len;
 197         unsigned int thlen;
 198         __be32 flags;
 199         unsigned int mss = 1;
 200         unsigned int hlen;
 201         unsigned int off;
 202         int flush = 1;
 203         int i;
 204
 205         off = skb_gro_offset(skb);
 206         hlen = off + sizeof(*th);
 207         th = skb_gro_header_fast(skb, off);
 208         if (skb_gro_header_hard(skb, hlen)) {
 209                 th = skb_gro_header_slow(skb, hlen, off);
 210                 if (unlikely(!th))
 211                         goto out;
 212         }
 213
 214         thlen = th->doff * 4;
 215         if (thlen < sizeof(*th))
 216                 goto out;
 217
 218         hlen = off + thlen;
 219         if (skb_gro_header_hard(skb, hlen)) {
 220                 th = skb_gro_header_slow(skb, hlen, off);
 221                 if (unlikely(!th))
 222                         goto out;
 223         }
 224
 225         skb_gro_pull(skb, thlen);
 226
 227         len = skb_gro_len(skb);
 228         flags = tcp_flag_word(th);
 229
 230         for (; (p = *head); head = &p->next) {
 231                 if (!NAPI_GRO_CB(p)->same_flow)
 232                         continue;
 233
 234                 th2 = tcp_hdr(p);
 235
 236                 if (*(u32 *)&th->source ^ *(u32 *)&th2->source) {
 237                         NAPI_GRO_CB(p)->same_flow = 0;
 238                         continue;
 239                 }
 240
 241                 goto found;
 242         }
 243
 244         goto out_check_final;
 245
 246 found:
 247         /* Include the IP ID check below from the inner most IP hdr */
 248         flush = NAPI_GRO_CB(p)->flush;
 249         flush |= (__force int)(flags & TCP_FLAG_CWR);
 250         flush |= (__force int)((flags ^ tcp_flag_word(th2)) &
 251                   ~(TCP_FLAG_CWR | TCP_FLAG_FIN | TCP_FLAG_PSH));
 252         flush |= (__force int)(th->ack_seq ^ th2->ack_seq);
 253         for (i = sizeof(*th); i < thlen; i += 4)
 254                 flush |= *(u32 *)((u8 *)th + i) ^
 255                          *(u32 *)((u8 *)th2 + i);
 256
 257         /* When we receive our second frame we can made a decision on if we
 258          * continue this flow as an atomic flow with a fixed ID or if we use
 259          * an incrementing ID.
 260          */
 261         if (NAPI_GRO_CB(p)->flush_id != 1 ||
 262             NAPI_GRO_CB(p)->count != 1 ||
 263             !NAPI_GRO_CB(p)->is_atomic)
 264                 flush |= NAPI_GRO_CB(p)->flush_id;
 265         else
 266                 NAPI_GRO_CB(p)->is_atomic = false;
 267
 268         mss = skb_shinfo(p)->gso_size;
 269
 270         flush |= (len - 1) >= mss;
 271         flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);
 272
 273         if (flush || skb_gro_receive(head, skb)) {
 274                 mss = 1;
 275                 goto out_check_final;
 276         }
 277
 278         p = *head;
 279         th2 = tcp_hdr(p);
 280         tcp_flag_word(th2) |= flags & (TCP_FLAG_FIN | TCP_FLAG_PSH);
 281
 282 out_check_final:
 283         flush = len < mss;
 284         flush |= (__force int)(flags & (TCP_FLAG_URG | TCP_FLAG_PSH |
 285                                         TCP_FLAG_RST | TCP_FLAG_SYN |
 286                                         TCP_FLAG_FIN));
 287
 288         if (p && (!NAPI_GRO_CB(skb)->same_flow || flush))
 289                 pp = head;
 290
 291 out:
 292         NAPI_GRO_CB(skb)->flush |= (flush != 0);
 293
 294         return pp;
 295 }
 296
 297 int tcp_gro_complete(struct sk_buff *skb)
 298 {
 299         struct tcphdr *th = tcp_hdr(skb);
 300
 301         skb->csum_start = (unsigned char *)th - skb->head;
 302         skb->csum_offset = offsetof(struct tcphdr, check);
 303         skb->ip_summed = CHECKSUM_PARTIAL;
 304
 305         skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
 306
 307         if (th->cwr)
 308                 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
 309
 310         return 0;
 311 }
 312 EXPORT_SYMBOL(tcp_gro_complete);
 313
 314 static struct sk_buff **tcp4_gro_receive(struct sk_buff **head, struct sk_buff *skb)
 315 {
 316         /* Don't bother verifying checksum if we're going to flush anyway. */
 317         if (!NAPI_GRO_CB(skb)->flush &&
 318             skb_gro_checksum_validate(skb, IPPROTO_TCP,
 319                                       inet_gro_compute_pseudo)) {
 320                 NAPI_GRO_CB(skb)->flush = 1;
 321                 return NULL;
 322         }
 323
 324         return tcp_gro_receive(head, skb);
 325 }
 326
 327 static int tcp4_gro_complete(struct sk_buff *skb, int thoff)
 328 {
 329         const struct iphdr *iph = ip_hdr(skb);
 330         struct tcphdr *th = tcp_hdr(skb);
 331
 332         th->check = ~tcp_v4_check(skb->len - thoff, iph->saddr,
 333                                   iph->daddr, 0);
 334         skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4;
 335
 336         if (NAPI_GRO_CB(skb)->is_atomic)
 337                 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_FIXEDID;
 338
 339         return tcp_gro_complete(skb);
 340 }
 341
 342 static const struct net_offload tcpv4_offload = {
 343         .callbacks = {
 344                 .gso_segment    =       tcp4_gso_segment,
 345                 .gro_receive    =       tcp4_gro_receive,
 346                 .gro_complete   =       tcp4_gro_complete,
 347         },
 348 };
 349
 350 int __init tcpv4_offload_init(void)
 351 {
 352         return inet_add_offload(&tcpv4_offload, IPPROTO_TCP);
 353 }