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