net/ipv4/gre_offload.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *      IPV4 GSO/GRO offload support
   4  *      Linux INET implementation
   5  *
   6  *      GRE GSO support
   7  */
   8
   9 #include <linux/skbuff.h>
  10 #include <linux/init.h>
  11 #include <net/protocol.h>
  12 #include <net/gre.h>
  13
  14 static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
  15                                        netdev_features_t features)
  16 {
  17         int tnl_hlen = skb_inner_mac_header(skb) - skb_transport_header(skb);
  18         bool need_csum, offload_csum, gso_partial, need_ipsec;
  19         struct sk_buff *segs = ERR_PTR(-EINVAL);
  20         u16 mac_offset = skb->mac_header;
  21         __be16 protocol = skb->protocol;
  22         u16 mac_len = skb->mac_len;
  23         int gre_offset, outer_hlen;
  24
  25         if (!skb->encapsulation)
  26                 goto out;
  27
  28         if (unlikely(tnl_hlen < sizeof(struct gre_base_hdr)))
  29                 goto out;
  30
  31         if (unlikely(!pskb_may_pull(skb, tnl_hlen)))
  32                 goto out;
  33
  34         /* setup inner skb. */
  35         skb->encapsulation = 0;
  36         SKB_GSO_CB(skb)->encap_level = 0;
  37         __skb_pull(skb, tnl_hlen);
  38         skb_reset_mac_header(skb);
  39         skb_set_network_header(skb, skb_inner_network_offset(skb));
  40         skb->mac_len = skb_inner_network_offset(skb);
  41         skb->protocol = skb->inner_protocol;
  42
  43         need_csum = !!(skb_shinfo(skb)->gso_type & SKB_GSO_GRE_CSUM);
  44         skb->encap_hdr_csum = need_csum;
  45
  46         features &= skb->dev->hw_enc_features;
  47         if (need_csum)
  48                 features &= ~NETIF_F_SCTP_CRC;
  49
  50         need_ipsec = skb_dst(skb) && dst_xfrm(skb_dst(skb));
  51         /* Try to offload checksum if possible */
  52         offload_csum = !!(need_csum && !need_ipsec &&
  53                           (skb->dev->features & NETIF_F_HW_CSUM));
  54
  55         /* segment inner packet. */
  56         segs = skb_mac_gso_segment(skb, features);
  57         if (IS_ERR_OR_NULL(segs)) {
  58                 skb_gso_error_unwind(skb, protocol, tnl_hlen, mac_offset,
  59                                      mac_len);
  60                 goto out;
  61         }
  62
  63         gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL);
  64
  65         outer_hlen = skb_tnl_header_len(skb);
  66         gre_offset = outer_hlen - tnl_hlen;
  67         skb = segs;
  68         do {
  69                 struct gre_base_hdr *greh;
  70                 __sum16 *pcsum;
  71
  72                 /* Set up inner headers if we are offloading inner checksum */
  73                 if (skb->ip_summed == CHECKSUM_PARTIAL) {
  74                         skb_reset_inner_headers(skb);
  75                         skb->encapsulation = 1;
  76                 }
  77
  78                 skb->mac_len = mac_len;
  79                 skb->protocol = protocol;
  80
  81                 __skb_push(skb, outer_hlen);
  82                 skb_reset_mac_header(skb);
  83                 skb_set_network_header(skb, mac_len);
  84                 skb_set_transport_header(skb, gre_offset);
  85
  86                 if (!need_csum)
  87                         continue;
  88
  89                 greh = (struct gre_base_hdr *)skb_transport_header(skb);
  90                 pcsum = (__sum16 *)(greh + 1);
  91
  92                 if (gso_partial && skb_is_gso(skb)) {
  93                         unsigned int partial_adj;
  94
  95                         /* Adjust checksum to account for the fact that
  96                          * the partial checksum is based on actual size
  97                          * whereas headers should be based on MSS size.
  98                          */
  99                         partial_adj = skb->len + skb_headroom(skb) -
 100                                       SKB_GSO_CB(skb)->data_offset -
 101                                       skb_shinfo(skb)->gso_size;
 102                         *pcsum = ~csum_fold((__force __wsum)htonl(partial_adj));
 103                 } else {
 104                         *pcsum = 0;
 105                 }
 106
 107                 *(pcsum + 1) = 0;
 108                 if (skb->encapsulation || !offload_csum) {
 109                         *pcsum = gso_make_checksum(skb, 0);
 110                 } else {
 111                         skb->ip_summed = CHECKSUM_PARTIAL;
 112                         skb->csum_start = skb_transport_header(skb) - skb->head;
 113                         skb->csum_offset = sizeof(*greh);
 114                 }
 115         } while ((skb = skb->next));
 116 out:
 117         return segs;
 118 }
 119
 120 static struct sk_buff *gre_gro_receive(struct list_head *head,
 121                                        struct sk_buff *skb)
 122 {
 123         struct sk_buff *pp = NULL;
 124         struct sk_buff *p;
 125         const struct gre_base_hdr *greh;
 126         unsigned int hlen, grehlen;
 127         unsigned int off;
 128         int flush = 1;
 129         struct packet_offload *ptype;
 130         __be16 type;
 131
 132         if (NAPI_GRO_CB(skb)->encap_mark)
 133                 goto out;
 134
 135         NAPI_GRO_CB(skb)->encap_mark = 1;
 136
 137         off = skb_gro_offset(skb);
 138         hlen = off + sizeof(*greh);
 139         greh = skb_gro_header_fast(skb, off);
 140         if (skb_gro_header_hard(skb, hlen)) {
 141                 greh = skb_gro_header_slow(skb, hlen, off);
 142                 if (unlikely(!greh))
 143                         goto out;
 144         }
 145
 146         /* Only support version 0 and K (key), C (csum) flags. Note that
 147          * although the support for the S (seq#) flag can be added easily
 148          * for GRO, this is problematic for GSO hence can not be enabled
 149          * here because a GRO pkt may end up in the forwarding path, thus
 150          * requiring GSO support to break it up correctly.
 151          */
 152         if ((greh->flags & ~(GRE_KEY|GRE_CSUM)) != 0)
 153                 goto out;
 154
 155         /* We can only support GRE_CSUM if we can track the location of
 156          * the GRE header.  In the case of FOU/GUE we cannot because the
 157          * outer UDP header displaces the GRE header leaving us in a state
 158          * of limbo.
 159          */
 160         if ((greh->flags & GRE_CSUM) && NAPI_GRO_CB(skb)->is_fou)
 161                 goto out;
 162
 163         type = greh->protocol;
 164
 165         rcu_read_lock();
 166         ptype = gro_find_receive_by_type(type);
 167         if (!ptype)
 168                 goto out_unlock;
 169
 170         grehlen = GRE_HEADER_SECTION;
 171
 172         if (greh->flags & GRE_KEY)
 173                 grehlen += GRE_HEADER_SECTION;
 174
 175         if (greh->flags & GRE_CSUM)
 176                 grehlen += GRE_HEADER_SECTION;
 177
 178         hlen = off + grehlen;
 179         if (skb_gro_header_hard(skb, hlen)) {
 180                 greh = skb_gro_header_slow(skb, hlen, off);
 181                 if (unlikely(!greh))
 182                         goto out_unlock;
 183         }
 184
 185         /* Don't bother verifying checksum if we're going to flush anyway. */
 186         if ((greh->flags & GRE_CSUM) && !NAPI_GRO_CB(skb)->flush) {
 187                 if (skb_gro_checksum_simple_validate(skb))
 188                         goto out_unlock;
 189
 190                 skb_gro_checksum_try_convert(skb, IPPROTO_GRE,
 191                                              null_compute_pseudo);
 192         }
 193
 194         list_for_each_entry(p, head, list) {
 195                 const struct gre_base_hdr *greh2;
 196
 197                 if (!NAPI_GRO_CB(p)->same_flow)
 198                         continue;
 199
 200                 /* The following checks are needed to ensure only pkts
 201                  * from the same tunnel are considered for aggregation.
 202                  * The criteria for "the same tunnel" includes:
 203                  * 1) same version (we only support version 0 here)
 204                  * 2) same protocol (we only support ETH_P_IP for now)
 205                  * 3) same set of flags
 206                  * 4) same key if the key field is present.
 207                  */
 208                 greh2 = (struct gre_base_hdr *)(p->data + off);
 209
 210                 if (greh2->flags != greh->flags ||
 211                     greh2->protocol != greh->protocol) {
 212                         NAPI_GRO_CB(p)->same_flow = 0;
 213                         continue;
 214                 }
 215                 if (greh->flags & GRE_KEY) {
 216                         /* compare keys */
 217                         if (*(__be32 *)(greh2+1) != *(__be32 *)(greh+1)) {
 218                                 NAPI_GRO_CB(p)->same_flow = 0;
 219                                 continue;
 220                         }
 221                 }
 222         }
 223
 224         skb_gro_pull(skb, grehlen);
 225
 226         /* Adjusted NAPI_GRO_CB(skb)->csum after skb_gro_pull()*/
 227         skb_gro_postpull_rcsum(skb, greh, grehlen);
 228
 229         pp = call_gro_receive(ptype->callbacks.gro_receive, head, skb);
 230         flush = 0;
 231
 232 out_unlock:
 233         rcu_read_unlock();
 234 out:
 235         skb_gro_flush_final(skb, pp, flush);
 236
 237         return pp;
 238 }
 239
 240 static int gre_gro_complete(struct sk_buff *skb, int nhoff)
 241 {
 242         struct gre_base_hdr *greh = (struct gre_base_hdr *)(skb->data + nhoff);
 243         struct packet_offload *ptype;
 244         unsigned int grehlen = sizeof(*greh);
 245         int err = -ENOENT;
 246         __be16 type;
 247
 248         skb->encapsulation = 1;
 249         skb_shinfo(skb)->gso_type = SKB_GSO_GRE;
 250
 251         type = greh->protocol;
 252         if (greh->flags & GRE_KEY)
 253                 grehlen += GRE_HEADER_SECTION;
 254
 255         if (greh->flags & GRE_CSUM)
 256                 grehlen += GRE_HEADER_SECTION;
 257
 258         rcu_read_lock();
 259         ptype = gro_find_complete_by_type(type);
 260         if (ptype)
 261                 err = ptype->callbacks.gro_complete(skb, nhoff + grehlen);
 262
 263         rcu_read_unlock();
 264
 265         skb_set_inner_mac_header(skb, nhoff + grehlen);
 266
 267         return err;
 268 }
 269
 270 static const struct net_offload gre_offload = {
 271         .callbacks = {
 272                 .gso_segment = gre_gso_segment,
 273                 .gro_receive = gre_gro_receive,
 274                 .gro_complete = gre_gro_complete,
 275         },
 276 };
 277
 278 static int __init gre_offload_init(void)
 279 {
 280         int err;
 281
 282         err = inet_add_offload(&gre_offload, IPPROTO_GRE);
 283 #if IS_ENABLED(CONFIG_IPV6)
 284         if (err)
 285                 return err;
 286
 287         err = inet6_add_offload(&gre_offload, IPPROTO_GRE);
 288         if (err)
 289                 inet_del_offload(&gre_offload, IPPROTO_GRE);
 290 #endif
 291
 292         return err;
 293 }
 294 device_initcall(gre_offload_init);