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