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