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