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