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         type = greh->protocol;
 154
 155         rcu_read_lock();
 156         ptype = gro_find_receive_by_type(type);
 157         if (!ptype)
 158                 goto out_unlock;
 159
 160         grehlen = GRE_HEADER_SECTION;
 161
 162         if (greh->flags & GRE_KEY)
 163                 grehlen += GRE_HEADER_SECTION;
 164
 165         if (greh->flags & GRE_CSUM)
 166                 grehlen += GRE_HEADER_SECTION;
 167
 168         hlen = off + grehlen;
 169         if (skb_gro_header_hard(skb, hlen)) {
 170                 greh = skb_gro_header_slow(skb, hlen, off);
 171                 if (unlikely(!greh))
 172                         goto out_unlock;
 173         }
 174
 175         /* Don't bother verifying checksum if we're going to flush anyway. */
 176         if ((greh->flags & GRE_CSUM) && !NAPI_GRO_CB(skb)->flush) {
 177                 if (skb_gro_checksum_simple_validate(skb))
 178                         goto out_unlock;
 179
 180                 skb_gro_checksum_try_convert(skb, IPPROTO_GRE, 0,
 181                                              null_compute_pseudo);
 182         }
 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         flush = 0;
 221
 222 out_unlock:
 223         rcu_read_unlock();
 224 out:
 225         NAPI_GRO_CB(skb)->flush |= flush;
 226
 227         return pp;
 228 }
 229
 230 static int gre_gro_complete(struct sk_buff *skb, int nhoff)
 231 {
 232         struct gre_base_hdr *greh = (struct gre_base_hdr *)(skb->data + nhoff);
 233         struct packet_offload *ptype;
 234         unsigned int grehlen = sizeof(*greh);
 235         int err = -ENOENT;
 236         __be16 type;
 237
 238         skb->encapsulation = 1;
 239         skb_shinfo(skb)->gso_type = SKB_GSO_GRE;
 240
 241         type = greh->protocol;
 242         if (greh->flags & GRE_KEY)
 243                 grehlen += GRE_HEADER_SECTION;
 244
 245         if (greh->flags & GRE_CSUM)
 246                 grehlen += GRE_HEADER_SECTION;
 247
 248         rcu_read_lock();
 249         ptype = gro_find_complete_by_type(type);
 250         if (ptype)
 251                 err = ptype->callbacks.gro_complete(skb, nhoff + grehlen);
 252
 253         rcu_read_unlock();
 254
 255         skb_set_inner_mac_header(skb, nhoff + grehlen);
 256
 257         return err;
 258 }
 259
 260 static const struct net_offload gre_offload = {
 261         .callbacks = {
 262                 .gso_segment = gre_gso_segment,
 263                 .gro_receive = gre_gro_receive,
 264                 .gro_complete = gre_gro_complete,
 265         },
 266 };
 267
 268 static int __init gre_offload_init(void)
 269 {
 270         return inet_add_offload(&gre_offload, IPPROTO_GRE);
 271 }
 272 device_initcall(gre_offload_init);