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