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, gso_partial;
  28
  29         if (!skb->encapsulation)
  30                 goto out;
  31
  32         if (unlikely(tnl_hlen < sizeof(struct gre_base_hdr)))
  33                 goto out;
  34
  35         if (unlikely(!pskb_may_pull(skb, tnl_hlen)))
  36                 goto out;
  37
  38         /* setup inner skb. */
  39         skb->encapsulation = 0;
  40         SKB_GSO_CB(skb)->encap_level = 0;
  41         __skb_pull(skb, tnl_hlen);
  42         skb_reset_mac_header(skb);
  43         skb_set_network_header(skb, skb_inner_network_offset(skb));
  44         skb->mac_len = skb_inner_network_offset(skb);
  45         skb->protocol = skb->inner_protocol;
  46
  47         need_csum = !!(skb_shinfo(skb)->gso_type & SKB_GSO_GRE_CSUM);
  48         skb->encap_hdr_csum = need_csum;
  49
  50         features &= skb->dev->hw_enc_features;
  51
  52         /* segment inner packet. */
  53         segs = skb_mac_gso_segment(skb, features);
  54         if (IS_ERR_OR_NULL(segs)) {
  55                 skb_gso_error_unwind(skb, protocol, tnl_hlen, mac_offset,
  56                                      mac_len);
  57                 goto out;
  58         }
  59
  60         gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL);
  61
  62         outer_hlen = skb_tnl_header_len(skb);
  63         gre_offset = outer_hlen - tnl_hlen;
  64         skb = segs;
  65         do {
  66                 struct gre_base_hdr *greh;
  67                 __sum16 *pcsum;
  68
  69                 /* Set up inner headers if we are offloading inner checksum */
  70                 if (skb->ip_summed == CHECKSUM_PARTIAL) {
  71                         skb_reset_inner_headers(skb);
  72                         skb->encapsulation = 1;
  73                 }
  74
  75                 skb->mac_len = mac_len;
  76                 skb->protocol = protocol;
  77
  78                 __skb_push(skb, outer_hlen);
  79                 skb_reset_mac_header(skb);
  80                 skb_set_network_header(skb, mac_len);
  81                 skb_set_transport_header(skb, gre_offset);
  82
  83                 if (!need_csum)
  84                         continue;
  85
  86                 greh = (struct gre_base_hdr *)skb_transport_header(skb);
  87                 pcsum = (__sum16 *)(greh + 1);
  88
  89                 if (gso_partial && skb_is_gso(skb)) {
  90                         unsigned int partial_adj;
  91
  92                         /* Adjust checksum to account for the fact that
  93                          * the partial checksum is based on actual size
  94                          * whereas headers should be based on MSS size.
  95                          */
  96                         partial_adj = skb->len + skb_headroom(skb) -
  97                                       SKB_GSO_CB(skb)->data_offset -
  98                                       skb_shinfo(skb)->gso_size;
  99                         *pcsum = ~csum_fold((__force __wsum)htonl(partial_adj));
 100                 } else {
 101                         *pcsum = 0;
 102                 }
 103
 104                 *(pcsum + 1) = 0;
 105                 *pcsum = gso_make_checksum(skb, 0);
 106         } while ((skb = skb->next));
 107 out:
 108         return segs;
 109 }
 110
 111 static struct sk_buff **gre_gro_receive(struct sk_buff **head,
 112                                         struct sk_buff *skb)
 113 {
 114         struct sk_buff **pp = NULL;
 115         struct sk_buff *p;
 116         const struct gre_base_hdr *greh;
 117         unsigned int hlen, grehlen;
 118         unsigned int off;
 119         int flush = 1;
 120         struct packet_offload *ptype;
 121         __be16 type;
 122
 123         if (NAPI_GRO_CB(skb)->encap_mark)
 124                 goto out;
 125
 126         NAPI_GRO_CB(skb)->encap_mark = 1;
 127
 128         off = skb_gro_offset(skb);
 129         hlen = off + sizeof(*greh);
 130         greh = skb_gro_header_fast(skb, off);
 131         if (skb_gro_header_hard(skb, hlen)) {
 132                 greh = skb_gro_header_slow(skb, hlen, off);
 133                 if (unlikely(!greh))
 134                         goto out;
 135         }
 136
 137         /* Only support version 0 and K (key), C (csum) flags. Note that
 138          * although the support for the S (seq#) flag can be added easily
 139          * for GRO, this is problematic for GSO hence can not be enabled
 140          * here because a GRO pkt may end up in the forwarding path, thus
 141          * requiring GSO support to break it up correctly.
 142          */
 143         if ((greh->flags & ~(GRE_KEY|GRE_CSUM)) != 0)
 144                 goto out;
 145
 146         /* We can only support GRE_CSUM if we can track the location of
 147          * the GRE header.  In the case of FOU/GUE we cannot because the
 148          * outer UDP header displaces the GRE header leaving us in a state
 149          * of limbo.
 150          */
 151         if ((greh->flags & GRE_CSUM) && NAPI_GRO_CB(skb)->is_fou)
 152                 goto out;
 153
 154         type = greh->protocol;
 155
 156         rcu_read_lock();
 157         ptype = gro_find_receive_by_type(type);
 158         if (!ptype)
 159                 goto out_unlock;
 160
 161         grehlen = GRE_HEADER_SECTION;
 162
 163         if (greh->flags & GRE_KEY)
 164                 grehlen += GRE_HEADER_SECTION;
 165
 166         if (greh->flags & GRE_CSUM)
 167                 grehlen += GRE_HEADER_SECTION;
 168
 169         hlen = off + grehlen;
 170         if (skb_gro_header_hard(skb, hlen)) {
 171                 greh = skb_gro_header_slow(skb, hlen, off);
 172                 if (unlikely(!greh))
 173                         goto out_unlock;
 174         }
 175
 176         /* Don't bother verifying checksum if we're going to flush anyway. */
 177         if ((greh->flags & GRE_CSUM) && !NAPI_GRO_CB(skb)->flush) {
 178                 if (skb_gro_checksum_simple_validate(skb))
 179                         goto out_unlock;
 180
 181                 skb_gro_checksum_try_convert(skb, IPPROTO_GRE, 0,
 182                                              null_compute_pseudo);
 183         }
 184
 185         for (p = *head; p; p = p->next) {
 186                 const struct gre_base_hdr *greh2;
 187
 188                 if (!NAPI_GRO_CB(p)->same_flow)
 189                         continue;
 190
 191                 /* The following checks are needed to ensure only pkts
 192                  * from the same tunnel are considered for aggregation.
 193                  * The criteria for "the same tunnel" includes:
 194                  * 1) same version (we only support version 0 here)
 195                  * 2) same protocol (we only support ETH_P_IP for now)
 196                  * 3) same set of flags
 197                  * 4) same key if the key field is present.
 198                  */
 199                 greh2 = (struct gre_base_hdr *)(p->data + off);
 200
 201                 if (greh2->flags != greh->flags ||
 202                     greh2->protocol != greh->protocol) {
 203                         NAPI_GRO_CB(p)->same_flow = 0;
 204                         continue;
 205                 }
 206                 if (greh->flags & GRE_KEY) {
 207                         /* compare keys */
 208                         if (*(__be32 *)(greh2+1) != *(__be32 *)(greh+1)) {
 209                                 NAPI_GRO_CB(p)->same_flow = 0;
 210                                 continue;
 211                         }
 212                 }
 213         }
 214
 215         skb_gro_pull(skb, grehlen);
 216
 217         /* Adjusted NAPI_GRO_CB(skb)->csum after skb_gro_pull()*/
 218         skb_gro_postpull_rcsum(skb, greh, grehlen);
 219
 220         pp = call_gro_receive(ptype->callbacks.gro_receive, head, skb);
 221         flush = 0;
 222
 223 out_unlock:
 224         rcu_read_unlock();
 225 out:
 226         NAPI_GRO_CB(skb)->flush |= flush;
 227
 228         return pp;
 229 }
 230
 231 static int gre_gro_complete(struct sk_buff *skb, int nhoff)
 232 {
 233         struct gre_base_hdr *greh = (struct gre_base_hdr *)(skb->data + nhoff);
 234         struct packet_offload *ptype;
 235         unsigned int grehlen = sizeof(*greh);
 236         int err = -ENOENT;
 237         __be16 type;
 238
 239         skb->encapsulation = 1;
 240         skb_shinfo(skb)->gso_type = SKB_GSO_GRE;
 241
 242         type = greh->protocol;
 243         if (greh->flags & GRE_KEY)
 244                 grehlen += GRE_HEADER_SECTION;
 245
 246         if (greh->flags & GRE_CSUM)
 247                 grehlen += GRE_HEADER_SECTION;
 248
 249         rcu_read_lock();
 250         ptype = gro_find_complete_by_type(type);
 251         if (ptype)
 252                 err = ptype->callbacks.gro_complete(skb, nhoff + grehlen);
 253
 254         rcu_read_unlock();
 255
 256         skb_set_inner_mac_header(skb, nhoff + grehlen);
 257
 258         return err;
 259 }
 260
 261 static const struct net_offload gre_offload = {
 262         .callbacks = {
 263                 .gso_segment = gre_gso_segment,
 264                 .gro_receive = gre_gro_receive,
 265                 .gro_complete = gre_gro_complete,
 266         },
 267 };
 268
 269 static int __init gre_offload_init(void)
 270 {
 271         int err;
 272
 273         err = inet_add_offload(&gre_offload, IPPROTO_GRE);
 274 #if IS_ENABLED(CONFIG_IPV6)
 275         if (err)
 276                 return err;
 277
 278         err = inet6_add_offload(&gre_offload, IPPROTO_GRE);
 279         if (err)
 280                 inet_del_offload(&gre_offload, IPPROTO_GRE);
 281 #endif
 282
 283         return err;
 284 }
 285 device_initcall(gre_offload_init);