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 <net/protocol.h>
  15 #include <net/gre.h>
  16
  17 static int gre_gso_send_check(struct sk_buff *skb)
  18 {
  19         if (!skb->encapsulation)
  20                 return -EINVAL;
  21         return 0;
  22 }
  23
  24 static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
  25                                        netdev_features_t features)
  26 {
  27         struct sk_buff *segs = ERR_PTR(-EINVAL);
  28         netdev_features_t enc_features;
  29         int ghl = GRE_HEADER_SECTION;
  30         struct gre_base_hdr *greh;
  31         u16 mac_offset = skb->mac_header;
  32         int mac_len = skb->mac_len;
  33         __be16 protocol = skb->protocol;
  34         int tnl_hlen;
  35         bool csum;
  36
  37         if (unlikely(skb_shinfo(skb)->gso_type &
  38                                 ~(SKB_GSO_TCPV4 |
  39                                   SKB_GSO_TCPV6 |
  40                                   SKB_GSO_UDP |
  41                                   SKB_GSO_DODGY |
  42                                   SKB_GSO_TCP_ECN |
  43                                   SKB_GSO_GRE |
  44                                   SKB_GSO_IPIP)))
  45                 goto out;
  46
  47         if (unlikely(!pskb_may_pull(skb, sizeof(*greh))))
  48                 goto out;
  49
  50         greh = (struct gre_base_hdr *)skb_transport_header(skb);
  51
  52         if (greh->flags & GRE_KEY)
  53                 ghl += GRE_HEADER_SECTION;
  54         if (greh->flags & GRE_SEQ)
  55                 ghl += GRE_HEADER_SECTION;
  56         if (greh->flags & GRE_CSUM) {
  57                 ghl += GRE_HEADER_SECTION;
  58                 csum = true;
  59         } else
  60                 csum = false;
  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                         greh = (struct gre_base_hdr *)(skb->data);
 101                         pcsum = (__be32 *)(greh + 1);
 102                         *pcsum = 0;
 103                         *(__sum16 *)pcsum = csum_fold(skb_checksum(skb, 0, skb->len, 0));
 104                 }
 105                 __skb_push(skb, tnl_hlen - ghl);
 106
 107                 skb_reset_inner_headers(skb);
 108                 skb->encapsulation = 1;
 109
 110                 skb_reset_mac_header(skb);
 111                 skb_set_network_header(skb, mac_len);
 112                 skb->mac_len = mac_len;
 113                 skb->protocol = protocol;
 114         } while ((skb = skb->next));
 115 out:
 116         return segs;
 117 }
 118
 119 /* Compute the whole skb csum in s/w and store it, then verify GRO csum
 120  * starting from gro_offset.
 121  */
 122 static __sum16 gro_skb_checksum(struct sk_buff *skb)
 123 {
 124         __sum16 sum;
 125
 126         skb->csum = skb_checksum(skb, 0, skb->len, 0);
 127         NAPI_GRO_CB(skb)->csum = csum_sub(skb->csum,
 128                 csum_partial(skb->data, skb_gro_offset(skb), 0));
 129         sum = csum_fold(NAPI_GRO_CB(skb)->csum);
 130         if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE)) {
 131                 if (unlikely(!sum))
 132                         netdev_rx_csum_fault(skb->dev);
 133         } else
 134                 skb->ip_summed = CHECKSUM_COMPLETE;
 135
 136         return sum;
 137 }
 138
 139 static struct sk_buff **gre_gro_receive(struct sk_buff **head,
 140                                         struct sk_buff *skb)
 141 {
 142         struct sk_buff **pp = NULL;
 143         struct sk_buff *p;
 144         const struct gre_base_hdr *greh;
 145         unsigned int hlen, grehlen;
 146         unsigned int off;
 147         int flush = 1;
 148         struct packet_offload *ptype;
 149         __be16 type;
 150
 151         off = skb_gro_offset(skb);
 152         hlen = off + sizeof(*greh);
 153         greh = skb_gro_header_fast(skb, off);
 154         if (skb_gro_header_hard(skb, hlen)) {
 155                 greh = skb_gro_header_slow(skb, hlen, off);
 156                 if (unlikely(!greh))
 157                         goto out;
 158         }
 159
 160         /* Only support version 0 and K (key), C (csum) flags. Note that
 161          * although the support for the S (seq#) flag can be added easily
 162          * for GRO, this is problematic for GSO hence can not be enabled
 163          * here because a GRO pkt may end up in the forwarding path, thus
 164          * requiring GSO support to break it up correctly.
 165          */
 166         if ((greh->flags & ~(GRE_KEY|GRE_CSUM)) != 0)
 167                 goto out;
 168
 169         type = greh->protocol;
 170
 171         rcu_read_lock();
 172         ptype = gro_find_receive_by_type(type);
 173         if (ptype == NULL)
 174                 goto out_unlock;
 175
 176         grehlen = GRE_HEADER_SECTION;
 177
 178         if (greh->flags & GRE_KEY)
 179                 grehlen += GRE_HEADER_SECTION;
 180
 181         if (greh->flags & GRE_CSUM)
 182                 grehlen += GRE_HEADER_SECTION;
 183
 184         hlen = off + grehlen;
 185         if (skb_gro_header_hard(skb, hlen)) {
 186                 greh = skb_gro_header_slow(skb, hlen, off);
 187                 if (unlikely(!greh))
 188                         goto out_unlock;
 189         }
 190         if (greh->flags & GRE_CSUM) { /* Need to verify GRE csum first */
 191                 __sum16 csum = 0;
 192
 193                 if (skb->ip_summed == CHECKSUM_COMPLETE)
 194                         csum = csum_fold(NAPI_GRO_CB(skb)->csum);
 195                 /* Don't trust csum error calculated/reported by h/w */
 196                 if (skb->ip_summed == CHECKSUM_NONE || csum != 0)
 197                         csum = gro_skb_checksum(skb);
 198
 199                 /* GRE CSUM is the 1's complement of the 1's complement sum
 200                  * of the GRE hdr plus payload so it should add up to 0xffff
 201                  * (and 0 after csum_fold()) just like the IPv4 hdr csum.
 202                  */
 203                 if (csum)
 204                         goto out_unlock;
 205         }
 206         flush = 0;
 207
 208         for (p = *head; p; p = p->next) {
 209                 const struct gre_base_hdr *greh2;
 210
 211                 if (!NAPI_GRO_CB(p)->same_flow)
 212                         continue;
 213
 214                 /* The following checks are needed to ensure only pkts
 215                  * from the same tunnel are considered for aggregation.
 216                  * The criteria for "the same tunnel" includes:
 217                  * 1) same version (we only support version 0 here)
 218                  * 2) same protocol (we only support ETH_P_IP for now)
 219                  * 3) same set of flags
 220                  * 4) same key if the key field is present.
 221                  */
 222                 greh2 = (struct gre_base_hdr *)(p->data + off);
 223
 224                 if (greh2->flags != greh->flags ||
 225                     greh2->protocol != greh->protocol) {
 226                         NAPI_GRO_CB(p)->same_flow = 0;
 227                         continue;
 228                 }
 229                 if (greh->flags & GRE_KEY) {
 230                         /* compare keys */
 231                         if (*(__be32 *)(greh2+1) != *(__be32 *)(greh+1)) {
 232                                 NAPI_GRO_CB(p)->same_flow = 0;
 233                                 continue;
 234                         }
 235                 }
 236         }
 237
 238         skb_gro_pull(skb, grehlen);
 239
 240         /* Adjusted NAPI_GRO_CB(skb)->csum after skb_gro_pull()*/
 241         skb_gro_postpull_rcsum(skb, greh, grehlen);
 242
 243         pp = ptype->callbacks.gro_receive(head, skb);
 244
 245 out_unlock:
 246         rcu_read_unlock();
 247 out:
 248         NAPI_GRO_CB(skb)->flush |= flush;
 249
 250         return pp;
 251 }
 252
 253 int gre_gro_complete(struct sk_buff *skb, int nhoff)
 254 {
 255         struct gre_base_hdr *greh = (struct gre_base_hdr *)(skb->data + nhoff);
 256         struct packet_offload *ptype;
 257         unsigned int grehlen = sizeof(*greh);
 258         int err = -ENOENT;
 259         __be16 type;
 260
 261         type = greh->protocol;
 262         if (greh->flags & GRE_KEY)
 263                 grehlen += GRE_HEADER_SECTION;
 264
 265         if (greh->flags & GRE_CSUM)
 266                 grehlen += GRE_HEADER_SECTION;
 267
 268         rcu_read_lock();
 269         ptype = gro_find_complete_by_type(type);
 270         if (ptype != NULL)
 271                 err = ptype->callbacks.gro_complete(skb, nhoff + grehlen);
 272
 273         rcu_read_unlock();
 274         return err;
 275 }
 276
 277 static const struct net_offload gre_offload = {
 278         .callbacks = {
 279                 .gso_send_check = gre_gso_send_check,
 280                 .gso_segment = gre_gso_segment,
 281                 .gro_receive = gre_gro_receive,
 282                 .gro_complete = gre_gro_complete,
 283         },
 284 };
 285
 286 static int __init gre_offload_init(void)
 287 {
 288         return inet_add_offload(&gre_offload, IPPROTO_GRE);
 289 }
 290
 291 static void __exit gre_offload_exit(void)
 292 {
 293         inet_del_offload(&gre_offload, IPPROTO_GRE);
 294 }
 295
 296 module_init(gre_offload_init);
 297 module_exit(gre_offload_exit);