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