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