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 int gre_gso_send_check(struct sk_buff *skb)
  19 {
  20         if (!skb->encapsulation)
  21                 return -EINVAL;
  22         return 0;
  23 }
  24
  25 static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
  26                                        netdev_features_t features)
  27 {
  28         struct sk_buff *segs = ERR_PTR(-EINVAL);
  29         netdev_features_t enc_features;
  30         int ghl;
  31         struct gre_base_hdr *greh;
  32         u16 mac_offset = skb->mac_header;
  33         int mac_len = skb->mac_len;
  34         __be16 protocol = skb->protocol;
  35         int tnl_hlen;
  36         bool csum;
  37
  38         if (unlikely(skb_shinfo(skb)->gso_type &
  39                                 ~(SKB_GSO_TCPV4 |
  40                                   SKB_GSO_TCPV6 |
  41                                   SKB_GSO_UDP |
  42                                   SKB_GSO_DODGY |
  43                                   SKB_GSO_TCP_ECN |
  44                                   SKB_GSO_GRE |
  45                                   SKB_GSO_GRE_CSUM |
  46                                   SKB_GSO_IPIP)))
  47                 goto out;
  48
  49         if (unlikely(!pskb_may_pull(skb, sizeof(*greh))))
  50                 goto out;
  51
  52         greh = (struct gre_base_hdr *)skb_transport_header(skb);
  53
  54         ghl = skb_inner_network_header(skb) - skb_transport_header(skb);
  55         if (unlikely(ghl < sizeof(*greh)))
  56                 goto out;
  57
  58         csum = !!(greh->flags & GRE_CSUM);
  59         if (csum)
  60                 skb->encap_hdr_csum = 1;
  61
  62         if (unlikely(!pskb_may_pull(skb, ghl)))
  63                 goto out;
  64
  65         /* setup inner skb. */
  66         skb->protocol = greh->protocol;
  67         skb->encapsulation = 0;
  68
  69         __skb_pull(skb, ghl);
  70         skb_reset_mac_header(skb);
  71         skb_set_network_header(skb, skb_inner_network_offset(skb));
  72         skb->mac_len = skb_inner_network_offset(skb);
  73
  74         /* segment inner packet. */
  75         enc_features = skb->dev->hw_enc_features & netif_skb_features(skb);
  76         segs = skb_mac_gso_segment(skb, enc_features);
  77         if (!segs || IS_ERR(segs)) {
  78                 skb_gso_error_unwind(skb, protocol, ghl, mac_offset, mac_len);
  79                 goto out;
  80         }
  81
  82         skb = segs;
  83         tnl_hlen = skb_tnl_header_len(skb);
  84         do {
  85                 __skb_push(skb, ghl);
  86                 if (csum) {
  87                         __be32 *pcsum;
  88
  89                         if (skb_has_shared_frag(skb)) {
  90                                 int err;
  91
  92                                 err = __skb_linearize(skb);
  93                                 if (err) {
  94                                         kfree_skb_list(segs);
  95                                         segs = ERR_PTR(err);
  96                                         goto out;
  97                                 }
  98                         }
  99
 100                         skb_reset_transport_header(skb);
 101
 102                         greh = (struct gre_base_hdr *)
 103                             skb_transport_header(skb);
 104                         pcsum = (__be32 *)(greh + 1);
 105                         *pcsum = 0;
 106                         *(__sum16 *)pcsum = gso_make_checksum(skb, 0);
 107                 }
 108                 __skb_push(skb, tnl_hlen - ghl);
 109
 110                 skb_reset_inner_headers(skb);
 111                 skb->encapsulation = 1;
 112
 113                 skb_reset_mac_header(skb);
 114                 skb_set_network_header(skb, mac_len);
 115                 skb->mac_len = mac_len;
 116                 skb->protocol = protocol;
 117         } while ((skb = skb->next));
 118 out:
 119         return segs;
 120 }
 121
 122 /* Compute the whole skb csum in s/w and store it, then verify GRO csum
 123  * starting from gro_offset.
 124  */
 125 static __sum16 gro_skb_checksum(struct sk_buff *skb)
 126 {
 127         __sum16 sum;
 128
 129         skb->csum = skb_checksum(skb, 0, skb->len, 0);
 130         NAPI_GRO_CB(skb)->csum = csum_sub(skb->csum,
 131                 csum_partial(skb->data, skb_gro_offset(skb), 0));
 132         sum = csum_fold(NAPI_GRO_CB(skb)->csum);
 133         if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE)) {
 134                 if (unlikely(!sum) && !skb->csum_complete_sw)
 135                         netdev_rx_csum_fault(skb->dev);
 136         } else {
 137                 skb->ip_summed = CHECKSUM_COMPLETE;
 138                 skb->csum_complete_sw = 1;
 139         }
 140
 141         return sum;
 142 }
 143
 144 static struct sk_buff **gre_gro_receive(struct sk_buff **head,
 145                                         struct sk_buff *skb)
 146 {
 147         struct sk_buff **pp = NULL;
 148         struct sk_buff *p;
 149         const struct gre_base_hdr *greh;
 150         unsigned int hlen, grehlen;
 151         unsigned int off;
 152         int flush = 1;
 153         struct packet_offload *ptype;
 154         __be16 type;
 155
 156         off = skb_gro_offset(skb);
 157         hlen = off + sizeof(*greh);
 158         greh = skb_gro_header_fast(skb, off);
 159         if (skb_gro_header_hard(skb, hlen)) {
 160                 greh = skb_gro_header_slow(skb, hlen, off);
 161                 if (unlikely(!greh))
 162                         goto out;
 163         }
 164
 165         /* Only support version 0 and K (key), C (csum) flags. Note that
 166          * although the support for the S (seq#) flag can be added easily
 167          * for GRO, this is problematic for GSO hence can not be enabled
 168          * here because a GRO pkt may end up in the forwarding path, thus
 169          * requiring GSO support to break it up correctly.
 170          */
 171         if ((greh->flags & ~(GRE_KEY|GRE_CSUM)) != 0)
 172                 goto out;
 173
 174         type = greh->protocol;
 175
 176         rcu_read_lock();
 177         ptype = gro_find_receive_by_type(type);
 178         if (ptype == NULL)
 179                 goto out_unlock;
 180
 181         grehlen = GRE_HEADER_SECTION;
 182
 183         if (greh->flags & GRE_KEY)
 184                 grehlen += GRE_HEADER_SECTION;
 185
 186         if (greh->flags & GRE_CSUM)
 187                 grehlen += GRE_HEADER_SECTION;
 188
 189         hlen = off + grehlen;
 190         if (skb_gro_header_hard(skb, hlen)) {
 191                 greh = skb_gro_header_slow(skb, hlen, off);
 192                 if (unlikely(!greh))
 193                         goto out_unlock;
 194         }
 195         if (greh->flags & GRE_CSUM) { /* Need to verify GRE csum first */
 196                 __sum16 csum = 0;
 197
 198                 if (skb->ip_summed == CHECKSUM_COMPLETE)
 199                         csum = csum_fold(NAPI_GRO_CB(skb)->csum);
 200                 /* Don't trust csum error calculated/reported by h/w */
 201                 if (skb->ip_summed == CHECKSUM_NONE || csum != 0)
 202                         csum = gro_skb_checksum(skb);
 203
 204                 /* GRE CSUM is the 1's complement of the 1's complement sum
 205                  * of the GRE hdr plus payload so it should add up to 0xffff
 206                  * (and 0 after csum_fold()) just like the IPv4 hdr csum.
 207                  */
 208                 if (csum)
 209                         goto out_unlock;
 210         }
 211         flush = 0;
 212
 213         for (p = *head; p; p = p->next) {
 214                 const struct gre_base_hdr *greh2;
 215
 216                 if (!NAPI_GRO_CB(p)->same_flow)
 217                         continue;
 218
 219                 /* The following checks are needed to ensure only pkts
 220                  * from the same tunnel are considered for aggregation.
 221                  * The criteria for "the same tunnel" includes:
 222                  * 1) same version (we only support version 0 here)
 223                  * 2) same protocol (we only support ETH_P_IP for now)
 224                  * 3) same set of flags
 225                  * 4) same key if the key field is present.
 226                  */
 227                 greh2 = (struct gre_base_hdr *)(p->data + off);
 228
 229                 if (greh2->flags != greh->flags ||
 230                     greh2->protocol != greh->protocol) {
 231                         NAPI_GRO_CB(p)->same_flow = 0;
 232                         continue;
 233                 }
 234                 if (greh->flags & GRE_KEY) {
 235                         /* compare keys */
 236                         if (*(__be32 *)(greh2+1) != *(__be32 *)(greh+1)) {
 237                                 NAPI_GRO_CB(p)->same_flow = 0;
 238                                 continue;
 239                         }
 240                 }
 241         }
 242
 243         skb_gro_pull(skb, grehlen);
 244
 245         /* Adjusted NAPI_GRO_CB(skb)->csum after skb_gro_pull()*/
 246         skb_gro_postpull_rcsum(skb, greh, grehlen);
 247
 248         pp = ptype->callbacks.gro_receive(head, skb);
 249
 250 out_unlock:
 251         rcu_read_unlock();
 252 out:
 253         NAPI_GRO_CB(skb)->flush |= flush;
 254
 255         return pp;
 256 }
 257
 258 static int gre_gro_complete(struct sk_buff *skb, int nhoff)
 259 {
 260         struct gre_base_hdr *greh = (struct gre_base_hdr *)(skb->data + nhoff);
 261         struct packet_offload *ptype;
 262         unsigned int grehlen = sizeof(*greh);
 263         int err = -ENOENT;
 264         __be16 type;
 265
 266         skb->encapsulation = 1;
 267         skb_shinfo(skb)->gso_type = SKB_GSO_GRE;
 268
 269         type = greh->protocol;
 270         if (greh->flags & GRE_KEY)
 271                 grehlen += GRE_HEADER_SECTION;
 272
 273         if (greh->flags & GRE_CSUM)
 274                 grehlen += GRE_HEADER_SECTION;
 275
 276         rcu_read_lock();
 277         ptype = gro_find_complete_by_type(type);
 278         if (ptype != NULL)
 279                 err = ptype->callbacks.gro_complete(skb, nhoff + grehlen);
 280
 281         rcu_read_unlock();
 282         return err;
 283 }
 284
 285 static const struct net_offload gre_offload = {
 286         .callbacks = {
 287                 .gso_send_check = gre_gso_send_check,
 288                 .gso_segment = gre_gso_segment,
 289                 .gro_receive = gre_gro_receive,
 290                 .gro_complete = gre_gro_complete,
 291         },
 292 };
 293
 294 static int __init gre_offload_init(void)
 295 {
 296         return inet_add_offload(&gre_offload, IPPROTO_GRE);
 297 }
 298 device_initcall(gre_offload_init);