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 int gre_gso_send_check(struct sk_buff *skb)
  19 {
  20         if (!skb->encapsulation)
  21                 return -EINVAL;
  22         return 0;
  23 }
  24
  25 static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
  26                                        netdev_features_t features)
  27 {
  28         struct sk_buff *segs = ERR_PTR(-EINVAL);
  29         netdev_features_t enc_features;
  30         int ghl;
  31         struct gre_base_hdr *greh;
  32         u16 mac_offset = skb->mac_header;
  33         int mac_len = skb->mac_len;
  34         __be16 protocol = skb->protocol;
  35         int tnl_hlen;
  36         bool csum;
  37
  38         if (unlikely(skb_shinfo(skb)->gso_type &
  39                                 ~(SKB_GSO_TCPV4 |
  40                                   SKB_GSO_TCPV6 |
  41                                   SKB_GSO_UDP |
  42                                   SKB_GSO_DODGY |
  43                                   SKB_GSO_TCP_ECN |
  44                                   SKB_GSO_GRE |
  45                                   SKB_GSO_GRE_CSUM |
  46                                   SKB_GSO_IPIP)))
  47                 goto out;
  48
  49         if (unlikely(!pskb_may_pull(skb, sizeof(*greh))))
  50                 goto out;
  51
  52         greh = (struct gre_base_hdr *)skb_transport_header(skb);
  53
  54         ghl = skb_inner_network_header(skb) - skb_transport_header(skb);
  55         if (unlikely(ghl < sizeof(*greh)))
  56                 goto out;
  57
  58         csum = !!(greh->flags & GRE_CSUM);
  59         if (csum)
  60                 skb->encap_hdr_csum = 1;
  61
  62         if (unlikely(!pskb_may_pull(skb, ghl)))
  63                 goto out;
  64
  65         /* setup inner skb. */
  66         skb->protocol = greh->protocol;
  67         skb->encapsulation = 0;
  68
  69         __skb_pull(skb, ghl);
  70         skb_reset_mac_header(skb);
  71         skb_set_network_header(skb, skb_inner_network_offset(skb));
  72         skb->mac_len = skb_inner_network_offset(skb);
  73
  74         /* segment inner packet. */
  75         enc_features = skb->dev->hw_enc_features & netif_skb_features(skb);
  76         segs = skb_mac_gso_segment(skb, enc_features);
  77         if (IS_ERR_OR_NULL(segs)) {
  78                 skb_gso_error_unwind(skb, protocol, ghl, mac_offset, mac_len);
  79                 goto out;
  80         }
  81
  82         skb = segs;
  83         tnl_hlen = skb_tnl_header_len(skb);
  84         do {
  85                 __skb_push(skb, ghl);
  86                 if (csum) {
  87                         __be32 *pcsum;
  88
  89                         if (skb_has_shared_frag(skb)) {
  90                                 int err;
  91
  92                                 err = __skb_linearize(skb);
  93                                 if (err) {
  94                                         kfree_skb_list(segs);
  95                                         segs = ERR_PTR(err);
  96                                         goto out;
  97                                 }
  98                         }
  99
 100                         skb_reset_transport_header(skb);
 101
 102                         greh = (struct gre_base_hdr *)
 103                             skb_transport_header(skb);
 104                         pcsum = (__be32 *)(greh + 1);
 105                         *pcsum = 0;
 106                         *(__sum16 *)pcsum = gso_make_checksum(skb, 0);
 107                 }
 108                 __skb_push(skb, tnl_hlen - ghl);
 109
 110                 skb_reset_inner_headers(skb);
 111                 skb->encapsulation = 1;
 112
 113                 skb_reset_mac_header(skb);
 114                 skb_set_network_header(skb, mac_len);
 115                 skb->mac_len = mac_len;
 116                 skb->protocol = protocol;
 117         } while ((skb = skb->next));
 118 out:
 119         return segs;
 120 }
 121
 122 static struct sk_buff **gre_gro_receive(struct sk_buff **head,
 123                                         struct sk_buff *skb)
 124 {
 125         struct sk_buff **pp = NULL;
 126         struct sk_buff *p;
 127         const struct gre_base_hdr *greh;
 128         unsigned int hlen, grehlen;
 129         unsigned int off;
 130         int flush = 1;
 131         struct packet_offload *ptype;
 132         __be16 type;
 133
 134         off = skb_gro_offset(skb);
 135         hlen = off + sizeof(*greh);
 136         greh = skb_gro_header_fast(skb, off);
 137         if (skb_gro_header_hard(skb, hlen)) {
 138                 greh = skb_gro_header_slow(skb, hlen, off);
 139                 if (unlikely(!greh))
 140                         goto out;
 141         }
 142
 143         /* Only support version 0 and K (key), C (csum) flags. Note that
 144          * although the support for the S (seq#) flag can be added easily
 145          * for GRO, this is problematic for GSO hence can not be enabled
 146          * here because a GRO pkt may end up in the forwarding path, thus
 147          * requiring GSO support to break it up correctly.
 148          */
 149         if ((greh->flags & ~(GRE_KEY|GRE_CSUM)) != 0)
 150                 goto out;
 151
 152         type = greh->protocol;
 153
 154         rcu_read_lock();
 155         ptype = gro_find_receive_by_type(type);
 156         if (ptype == NULL)
 157                 goto out_unlock;
 158
 159         grehlen = GRE_HEADER_SECTION;
 160
 161         if (greh->flags & GRE_KEY)
 162                 grehlen += GRE_HEADER_SECTION;
 163
 164         if (greh->flags & GRE_CSUM)
 165                 grehlen += GRE_HEADER_SECTION;
 166
 167         hlen = off + grehlen;
 168         if (skb_gro_header_hard(skb, hlen)) {
 169                 greh = skb_gro_header_slow(skb, hlen, off);
 170                 if (unlikely(!greh))
 171                         goto out_unlock;
 172         }
 173
 174         /* Don't bother verifying checksum if we're going to flush anyway. */
 175         if (greh->flags & GRE_CSUM) {
 176                 if (!NAPI_GRO_CB(skb)->flush &&
 177                     skb_gro_checksum_simple_validate(skb))
 178                         goto out_unlock;
 179                 NAPI_GRO_CB(skb)->encapsulation++;
 180         }
 181
 182         flush = 0;
 183
 184         for (p = *head; p; p = p->next) {
 185                 const struct gre_base_hdr *greh2;
 186
 187                 if (!NAPI_GRO_CB(p)->same_flow)
 188                         continue;
 189
 190                 /* The following checks are needed to ensure only pkts
 191                  * from the same tunnel are considered for aggregation.
 192                  * The criteria for "the same tunnel" includes:
 193                  * 1) same version (we only support version 0 here)
 194                  * 2) same protocol (we only support ETH_P_IP for now)
 195                  * 3) same set of flags
 196                  * 4) same key if the key field is present.
 197                  */
 198                 greh2 = (struct gre_base_hdr *)(p->data + off);
 199
 200                 if (greh2->flags != greh->flags ||
 201                     greh2->protocol != greh->protocol) {
 202                         NAPI_GRO_CB(p)->same_flow = 0;
 203                         continue;
 204                 }
 205                 if (greh->flags & GRE_KEY) {
 206                         /* compare keys */
 207                         if (*(__be32 *)(greh2+1) != *(__be32 *)(greh+1)) {
 208                                 NAPI_GRO_CB(p)->same_flow = 0;
 209                                 continue;
 210                         }
 211                 }
 212         }
 213
 214         skb_gro_pull(skb, grehlen);
 215
 216         /* Adjusted NAPI_GRO_CB(skb)->csum after skb_gro_pull()*/
 217         skb_gro_postpull_rcsum(skb, greh, grehlen);
 218
 219         pp = ptype->callbacks.gro_receive(head, skb);
 220
 221 out_unlock:
 222         rcu_read_unlock();
 223 out:
 224         NAPI_GRO_CB(skb)->flush |= flush;
 225
 226         return pp;
 227 }
 228
 229 static int gre_gro_complete(struct sk_buff *skb, int nhoff)
 230 {
 231         struct gre_base_hdr *greh = (struct gre_base_hdr *)(skb->data + nhoff);
 232         struct packet_offload *ptype;
 233         unsigned int grehlen = sizeof(*greh);
 234         int err = -ENOENT;
 235         __be16 type;
 236
 237         skb->encapsulation = 1;
 238         skb_shinfo(skb)->gso_type = SKB_GSO_GRE;
 239
 240         type = greh->protocol;
 241         if (greh->flags & GRE_KEY)
 242                 grehlen += GRE_HEADER_SECTION;
 243
 244         if (greh->flags & GRE_CSUM)
 245                 grehlen += GRE_HEADER_SECTION;
 246
 247         rcu_read_lock();
 248         ptype = gro_find_complete_by_type(type);
 249         if (ptype != NULL)
 250                 err = ptype->callbacks.gro_complete(skb, nhoff + grehlen);
 251
 252         rcu_read_unlock();
 253         return err;
 254 }
 255
 256 static const struct net_offload gre_offload = {
 257         .callbacks = {
 258                 .gso_send_check = gre_gso_send_check,
 259                 .gso_segment = gre_gso_segment,
 260                 .gro_receive = gre_gro_receive,
 261                 .gro_complete = gre_gro_complete,
 262         },
 263 };
 264
 265 static int __init gre_offload_init(void)
 266 {
 267         return inet_add_offload(&gre_offload, IPPROTO_GRE);
 268 }
 269 device_initcall(gre_offload_init);