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