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 struct sk_buff *gre_gso_segment(struct sk_buff *skb,
  19                                        netdev_features_t features)
  20 {
  21         int tnl_hlen = skb_inner_mac_header(skb) - skb_transport_header(skb);
  22         struct sk_buff *segs = ERR_PTR(-EINVAL);
  23         u16 mac_offset = skb->mac_header;
  24         __be16 protocol = skb->protocol;
  25         u16 mac_len = skb->mac_len;
  26         int gre_offset, outer_hlen;
  27         bool need_csum, ufo;
  28
  29         if (unlikely(skb_shinfo(skb)->gso_type &
  30                                 ~(SKB_GSO_TCPV4 |
  31                                   SKB_GSO_TCPV6 |
  32                                   SKB_GSO_UDP |
  33                                   SKB_GSO_DODGY |
  34                                   SKB_GSO_TCP_ECN |
  35                                   SKB_GSO_GRE |
  36                                   SKB_GSO_GRE_CSUM |
  37                                   SKB_GSO_IPIP |
  38                                   SKB_GSO_SIT)))
  39                 goto out;
  40
  41         if (!skb->encapsulation)
  42                 goto out;
  43
  44         if (unlikely(tnl_hlen < sizeof(struct gre_base_hdr)))
  45                 goto out;
  46
  47         if (unlikely(!pskb_may_pull(skb, tnl_hlen)))
  48                 goto out;
  49
  50         /* setup inner skb. */
  51         skb->encapsulation = 0;
  52         __skb_pull(skb, tnl_hlen);
  53         skb_reset_mac_header(skb);
  54         skb_set_network_header(skb, skb_inner_network_offset(skb));
  55         skb->mac_len = skb_inner_network_offset(skb);
  56         skb->protocol = skb->inner_protocol;
  57
  58         need_csum = !!(skb_shinfo(skb)->gso_type & SKB_GSO_GRE_CSUM);
  59         skb->encap_hdr_csum = need_csum;
  60
  61         ufo = !!(skb_shinfo(skb)->gso_type & SKB_GSO_UDP);
  62
  63         features &= skb->dev->hw_enc_features;
  64
  65         /* The only checksum offload we care about from here on out is the
  66          * outer one so strip the existing checksum feature flags based
  67          * on the fact that we will be computing our checksum in software.
  68          */
  69         if (ufo) {
  70                 features &= ~NETIF_F_CSUM_MASK;
  71                 if (!need_csum)
  72                         features |= NETIF_F_HW_CSUM;
  73         }
  74
  75         /* segment inner packet. */
  76         segs = skb_mac_gso_segment(skb, features);
  77         if (IS_ERR_OR_NULL(segs)) {
  78                 skb_gso_error_unwind(skb, protocol, tnl_hlen, mac_offset,
  79                                      mac_len);
  80                 goto out;
  81         }
  82
  83         outer_hlen = skb_tnl_header_len(skb);
  84         gre_offset = outer_hlen - tnl_hlen;
  85         skb = segs;
  86         do {
  87                 struct gre_base_hdr *greh;
  88                 __be32 *pcsum;
  89
  90                 /* Set up inner headers if we are offloading inner checksum */
  91                 if (skb->ip_summed == CHECKSUM_PARTIAL) {
  92                         skb_reset_inner_headers(skb);
  93                         skb->encapsulation = 1;
  94                 }
  95
  96                 skb->mac_len = mac_len;
  97                 skb->protocol = protocol;
  98
  99                 __skb_push(skb, outer_hlen);
 100                 skb_reset_mac_header(skb);
 101                 skb_set_network_header(skb, mac_len);
 102                 skb_set_transport_header(skb, gre_offset);
 103
 104                 if (!need_csum)
 105                         continue;
 106
 107                 greh = (struct gre_base_hdr *)skb_transport_header(skb);
 108                 pcsum = (__be32 *)(greh + 1);
 109
 110                 *pcsum = 0;
 111                 *(__sum16 *)pcsum = gso_make_checksum(skb, 0);
 112         } while ((skb = skb->next));
 113 out:
 114         return segs;
 115 }
 116
 117 static struct sk_buff **gre_gro_receive(struct sk_buff **head,
 118                                         struct sk_buff *skb)
 119 {
 120         struct sk_buff **pp = NULL;
 121         struct sk_buff *p;
 122         const struct gre_base_hdr *greh;
 123         unsigned int hlen, grehlen;
 124         unsigned int off;
 125         int flush = 1;
 126         struct packet_offload *ptype;
 127         __be16 type;
 128
 129         off = skb_gro_offset(skb);
 130         hlen = off + sizeof(*greh);
 131         greh = skb_gro_header_fast(skb, off);
 132         if (skb_gro_header_hard(skb, hlen)) {
 133                 greh = skb_gro_header_slow(skb, hlen, off);
 134                 if (unlikely(!greh))
 135                         goto out;
 136         }
 137
 138         /* Only support version 0 and K (key), C (csum) flags. Note that
 139          * although the support for the S (seq#) flag can be added easily
 140          * for GRO, this is problematic for GSO hence can not be enabled
 141          * here because a GRO pkt may end up in the forwarding path, thus
 142          * requiring GSO support to break it up correctly.
 143          */
 144         if ((greh->flags & ~(GRE_KEY|GRE_CSUM)) != 0)
 145                 goto out;
 146
 147         type = greh->protocol;
 148
 149         rcu_read_lock();
 150         ptype = gro_find_receive_by_type(type);
 151         if (!ptype)
 152                 goto out_unlock;
 153
 154         grehlen = GRE_HEADER_SECTION;
 155
 156         if (greh->flags & GRE_KEY)
 157                 grehlen += GRE_HEADER_SECTION;
 158
 159         if (greh->flags & GRE_CSUM)
 160                 grehlen += GRE_HEADER_SECTION;
 161
 162         hlen = off + grehlen;
 163         if (skb_gro_header_hard(skb, hlen)) {
 164                 greh = skb_gro_header_slow(skb, hlen, off);
 165                 if (unlikely(!greh))
 166                         goto out_unlock;
 167         }
 168
 169         /* Don't bother verifying checksum if we're going to flush anyway. */
 170         if ((greh->flags & GRE_CSUM) && !NAPI_GRO_CB(skb)->flush) {
 171                 if (skb_gro_checksum_simple_validate(skb))
 172                         goto out_unlock;
 173
 174                 skb_gro_checksum_try_convert(skb, IPPROTO_GRE, 0,
 175                                              null_compute_pseudo);
 176         }
 177
 178         for (p = *head; p; p = p->next) {
 179                 const struct gre_base_hdr *greh2;
 180
 181                 if (!NAPI_GRO_CB(p)->same_flow)
 182                         continue;
 183
 184                 /* The following checks are needed to ensure only pkts
 185                  * from the same tunnel are considered for aggregation.
 186                  * The criteria for "the same tunnel" includes:
 187                  * 1) same version (we only support version 0 here)
 188                  * 2) same protocol (we only support ETH_P_IP for now)
 189                  * 3) same set of flags
 190                  * 4) same key if the key field is present.
 191                  */
 192                 greh2 = (struct gre_base_hdr *)(p->data + off);
 193
 194                 if (greh2->flags != greh->flags ||
 195                     greh2->protocol != greh->protocol) {
 196                         NAPI_GRO_CB(p)->same_flow = 0;
 197                         continue;
 198                 }
 199                 if (greh->flags & GRE_KEY) {
 200                         /* compare keys */
 201                         if (*(__be32 *)(greh2+1) != *(__be32 *)(greh+1)) {
 202                                 NAPI_GRO_CB(p)->same_flow = 0;
 203                                 continue;
 204                         }
 205                 }
 206         }
 207
 208         skb_gro_pull(skb, grehlen);
 209
 210         /* Adjusted NAPI_GRO_CB(skb)->csum after skb_gro_pull()*/
 211         skb_gro_postpull_rcsum(skb, greh, grehlen);
 212
 213         pp = ptype->callbacks.gro_receive(head, skb);
 214         flush = 0;
 215
 216 out_unlock:
 217         rcu_read_unlock();
 218 out:
 219         NAPI_GRO_CB(skb)->flush |= flush;
 220
 221         return pp;
 222 }
 223
 224 static int gre_gro_complete(struct sk_buff *skb, int nhoff)
 225 {
 226         struct gre_base_hdr *greh = (struct gre_base_hdr *)(skb->data + nhoff);
 227         struct packet_offload *ptype;
 228         unsigned int grehlen = sizeof(*greh);
 229         int err = -ENOENT;
 230         __be16 type;
 231
 232         skb->encapsulation = 1;
 233         skb_shinfo(skb)->gso_type = SKB_GSO_GRE;
 234
 235         type = greh->protocol;
 236         if (greh->flags & GRE_KEY)
 237                 grehlen += GRE_HEADER_SECTION;
 238
 239         if (greh->flags & GRE_CSUM)
 240                 grehlen += GRE_HEADER_SECTION;
 241
 242         rcu_read_lock();
 243         ptype = gro_find_complete_by_type(type);
 244         if (ptype)
 245                 err = ptype->callbacks.gro_complete(skb, nhoff + grehlen);
 246
 247         rcu_read_unlock();
 248
 249         skb_set_inner_mac_header(skb, nhoff + grehlen);
 250
 251         return err;
 252 }
 253
 254 static const struct net_offload gre_offload = {
 255         .callbacks = {
 256                 .gso_segment = gre_gso_segment,
 257                 .gro_receive = gre_gro_receive,
 258                 .gro_complete = gre_gro_complete,
 259         },
 260 };
 261
 262 static int __init gre_offload_init(void)
 263 {
 264         return inet_add_offload(&gre_offload, IPPROTO_GRE);
 265 }
 266 device_initcall(gre_offload_init);