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