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