net/ipv4/gre_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  *      GRE GSO support
  11  */
  12
  13 #include <linux/skbuff.h>
  14 #include <linux/init.h>
  15 #include <net/protocol.h>
  16 #include <net/gre.h>
  17
  18 static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
  19                                        netdev_features_t features)
  20 {
  21         int tnl_hlen = skb_inner_mac_header(skb) - skb_transport_header(skb);
  22         struct sk_buff *segs = ERR_PTR(-EINVAL);
  23         u16 mac_offset = skb->mac_header;
  24         __be16 protocol = skb->protocol;
  25         u16 mac_len = skb->mac_len;
  26         int gre_offset, outer_hlen;
  27         bool need_csum, ufo;
  28
  29         if (unlikely(skb_shinfo(skb)->gso_type &
  30                                 ~(SKB_GSO_TCPV4 |
  31                                   SKB_GSO_TCPV6 |
  32                                   SKB_GSO_UDP |
  33                                   SKB_GSO_DODGY |
  34                                   SKB_GSO_TCP_ECN |
  35                                   SKB_GSO_TCP_FIXEDID |
  36                                   SKB_GSO_GRE |
  37                                   SKB_GSO_GRE_CSUM |
  38                                   SKB_GSO_IPIP |
  39                                   SKB_GSO_SIT |
  40                                   SKB_GSO_PARTIAL)))
  41                 goto out;
  42
  43         if (!skb->encapsulation)
  44                 goto out;
  45
  46         if (unlikely(tnl_hlen < sizeof(struct gre_base_hdr)))
  47                 goto out;
  48
  49         if (unlikely(!pskb_may_pull(skb, tnl_hlen)))
  50                 goto out;
  51
  52         /* setup inner skb. */
  53         skb->encapsulation = 0;
  54         SKB_GSO_CB(skb)->encap_level = 0;
  55         __skb_pull(skb, tnl_hlen);
  56         skb_reset_mac_header(skb);
  57         skb_set_network_header(skb, skb_inner_network_offset(skb));
  58         skb->mac_len = skb_inner_network_offset(skb);
  59         skb->protocol = skb->inner_protocol;
  60
  61         need_csum = !!(skb_shinfo(skb)->gso_type & SKB_GSO_GRE_CSUM);
  62         skb->encap_hdr_csum = need_csum;
  63
  64         ufo = !!(skb_shinfo(skb)->gso_type & SKB_GSO_UDP);
  65
  66         features &= skb->dev->hw_enc_features;
  67
  68         /* The only checksum offload we care about from here on out is the
  69          * outer one so strip the existing checksum feature flags based
  70          * on the fact that we will be computing our checksum in software.
  71          */
  72         if (ufo) {
  73                 features &= ~NETIF_F_CSUM_MASK;
  74                 if (!need_csum)
  75                         features |= NETIF_F_HW_CSUM;
  76         }
  77
  78         /* segment inner packet. */
  79         segs = skb_mac_gso_segment(skb, features);
  80         if (IS_ERR_OR_NULL(segs)) {
  81                 skb_gso_error_unwind(skb, protocol, tnl_hlen, mac_offset,
  82                                      mac_len);
  83                 goto out;
  84         }
  85
  86         outer_hlen = skb_tnl_header_len(skb);
  87         gre_offset = outer_hlen - tnl_hlen;
  88         skb = segs;
  89         do {
  90                 struct gre_base_hdr *greh;
  91                 __sum16 *pcsum;
  92
  93                 /* Set up inner headers if we are offloading inner checksum */
  94                 if (skb->ip_summed == CHECKSUM_PARTIAL) {
  95                         skb_reset_inner_headers(skb);
  96                         skb->encapsulation = 1;
  97                 }
  98
  99                 skb->mac_len = mac_len;
 100                 skb->protocol = protocol;
 101
 102                 __skb_push(skb, outer_hlen);
 103                 skb_reset_mac_header(skb);
 104                 skb_set_network_header(skb, mac_len);
 105                 skb_set_transport_header(skb, gre_offset);
 106
 107                 if (!need_csum)
 108                         continue;
 109
 110                 greh = (struct gre_base_hdr *)skb_transport_header(skb);
 111                 pcsum = (__sum16 *)(greh + 1);
 112
 113                 if (skb_is_gso(skb)) {
 114                         unsigned int partial_adj;
 115
 116                         /* Adjust checksum to account for the fact that
 117                          * the partial checksum is based on actual size
 118                          * whereas headers should be based on MSS size.
 119                          */
 120                         partial_adj = skb->len + skb_headroom(skb) -
 121                                       SKB_GSO_CB(skb)->data_offset -
 122                                       skb_shinfo(skb)->gso_size;
 123                         *pcsum = ~csum_fold((__force __wsum)htonl(partial_adj));
 124                 } else {
 125                         *pcsum = 0;
 126                 }
 127
 128                 *(pcsum + 1) = 0;
 129                 *pcsum = gso_make_checksum(skb, 0);
 130         } while ((skb = skb->next));
 131 out:
 132         return segs;
 133 }
 134
 135 static struct sk_buff **gre_gro_receive(struct sk_buff **head,
 136                                         struct sk_buff *skb)
 137 {
 138         struct sk_buff **pp = NULL;
 139         struct sk_buff *p;
 140         const struct gre_base_hdr *greh;
 141         unsigned int hlen, grehlen;
 142         unsigned int off;
 143         int flush = 1;
 144         struct packet_offload *ptype;
 145         __be16 type;
 146
 147         if (NAPI_GRO_CB(skb)->encap_mark)
 148                 goto out;
 149
 150         NAPI_GRO_CB(skb)->encap_mark = 1;
 151
 152         off = skb_gro_offset(skb);
 153         hlen = off + sizeof(*greh);
 154         greh = skb_gro_header_fast(skb, off);
 155         if (skb_gro_header_hard(skb, hlen)) {
 156                 greh = skb_gro_header_slow(skb, hlen, off);
 157                 if (unlikely(!greh))
 158                         goto out;
 159         }
 160
 161         /* Only support version 0 and K (key), C (csum) flags. Note that
 162          * although the support for the S (seq#) flag can be added easily
 163          * for GRO, this is problematic for GSO hence can not be enabled
 164          * here because a GRO pkt may end up in the forwarding path, thus
 165          * requiring GSO support to break it up correctly.
 166          */
 167         if ((greh->flags & ~(GRE_KEY|GRE_CSUM)) != 0)
 168                 goto out;
 169
 170         /* We can only support GRE_CSUM if we can track the location of
 171          * the GRE header.  In the case of FOU/GUE we cannot because the
 172          * outer UDP header displaces the GRE header leaving us in a state
 173          * of limbo.
 174          */
 175         if ((greh->flags & GRE_CSUM) && NAPI_GRO_CB(skb)->is_fou)
 176                 goto out;
 177
 178         type = greh->protocol;
 179
 180         rcu_read_lock();
 181         ptype = gro_find_receive_by_type(type);
 182         if (!ptype)
 183                 goto out_unlock;
 184
 185         grehlen = GRE_HEADER_SECTION;
 186
 187         if (greh->flags & GRE_KEY)
 188                 grehlen += GRE_HEADER_SECTION;
 189
 190         if (greh->flags & GRE_CSUM)
 191                 grehlen += GRE_HEADER_SECTION;
 192
 193         hlen = off + grehlen;
 194         if (skb_gro_header_hard(skb, hlen)) {
 195                 greh = skb_gro_header_slow(skb, hlen, off);
 196                 if (unlikely(!greh))
 197                         goto out_unlock;
 198         }
 199
 200         /* Don't bother verifying checksum if we're going to flush anyway. */
 201         if ((greh->flags & GRE_CSUM) && !NAPI_GRO_CB(skb)->flush) {
 202                 if (skb_gro_checksum_simple_validate(skb))
 203                         goto out_unlock;
 204
 205                 skb_gro_checksum_try_convert(skb, IPPROTO_GRE, 0,
 206                                              null_compute_pseudo);
 207         }
 208
 209         for (p = *head; p; p = p->next) {
 210                 const struct gre_base_hdr *greh2;
 211
 212                 if (!NAPI_GRO_CB(p)->same_flow)
 213                         continue;
 214
 215                 /* The following checks are needed to ensure only pkts
 216                  * from the same tunnel are considered for aggregation.
 217                  * The criteria for "the same tunnel" includes:
 218                  * 1) same version (we only support version 0 here)
 219                  * 2) same protocol (we only support ETH_P_IP for now)
 220                  * 3) same set of flags
 221                  * 4) same key if the key field is present.
 222                  */
 223                 greh2 = (struct gre_base_hdr *)(p->data + off);
 224
 225                 if (greh2->flags != greh->flags ||
 226                     greh2->protocol != greh->protocol) {
 227                         NAPI_GRO_CB(p)->same_flow = 0;
 228                         continue;
 229                 }
 230                 if (greh->flags & GRE_KEY) {
 231                         /* compare keys */
 232                         if (*(__be32 *)(greh2+1) != *(__be32 *)(greh+1)) {
 233                                 NAPI_GRO_CB(p)->same_flow = 0;
 234                                 continue;
 235                         }
 236                 }
 237         }
 238
 239         skb_gro_pull(skb, grehlen);
 240
 241         /* Adjusted NAPI_GRO_CB(skb)->csum after skb_gro_pull()*/
 242         skb_gro_postpull_rcsum(skb, greh, grehlen);
 243
 244         pp = ptype->callbacks.gro_receive(head, skb);
 245         flush = 0;
 246
 247 out_unlock:
 248         rcu_read_unlock();
 249 out:
 250         NAPI_GRO_CB(skb)->flush |= flush;
 251
 252         return pp;
 253 }
 254
 255 static int gre_gro_complete(struct sk_buff *skb, int nhoff)
 256 {
 257         struct gre_base_hdr *greh = (struct gre_base_hdr *)(skb->data + nhoff);
 258         struct packet_offload *ptype;
 259         unsigned int grehlen = sizeof(*greh);
 260         int err = -ENOENT;
 261         __be16 type;
 262
 263         skb->encapsulation = 1;
 264         skb_shinfo(skb)->gso_type = SKB_GSO_GRE;
 265
 266         type = greh->protocol;
 267         if (greh->flags & GRE_KEY)
 268                 grehlen += GRE_HEADER_SECTION;
 269
 270         if (greh->flags & GRE_CSUM)
 271                 grehlen += GRE_HEADER_SECTION;
 272
 273         rcu_read_lock();
 274         ptype = gro_find_complete_by_type(type);
 275         if (ptype)
 276                 err = ptype->callbacks.gro_complete(skb, nhoff + grehlen);
 277
 278         rcu_read_unlock();
 279
 280         skb_set_inner_mac_header(skb, nhoff + grehlen);
 281
 282         return err;
 283 }
 284
 285 static const struct net_offload gre_offload = {
 286         .callbacks = {
 287                 .gso_segment = gre_gso_segment,
 288                 .gro_receive = gre_gro_receive,
 289                 .gro_complete = gre_gro_complete,
 290         },
 291 };
 292
 293 static int __init gre_offload_init(void)
 294 {
 295         int err;
 296
 297         err = inet_add_offload(&gre_offload, IPPROTO_GRE);
 298 #if IS_ENABLED(CONFIG_IPV6)
 299         if (err)
 300                 return err;
 301
 302         err = inet6_add_offload(&gre_offload, IPPROTO_GRE);
 303         if (err)
 304                 inet_del_offload(&gre_offload, IPPROTO_GRE);
 305 #endif
 306
 307         return err;
 308 }
 309 device_initcall(gre_offload_init);