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         int mac_len = skb->mac_len;
  32         __be16 protocol = skb->protocol;
  33         int tnl_hlen;
  34         bool csum;
  35
  36         if (unlikely(skb_shinfo(skb)->gso_type &
  37                                 ~(SKB_GSO_TCPV4 |
  38                                   SKB_GSO_TCPV6 |
  39                                   SKB_GSO_UDP |
  40                                   SKB_GSO_DODGY |
  41                                   SKB_GSO_TCP_ECN |
  42                                   SKB_GSO_GRE)))
  43                 goto out;
  44
  45         if (unlikely(!pskb_may_pull(skb, sizeof(*greh))))
  46                 goto out;
  47
  48         greh = (struct gre_base_hdr *)skb_transport_header(skb);
  49
  50         if (greh->flags & GRE_KEY)
  51                 ghl += GRE_HEADER_SECTION;
  52         if (greh->flags & GRE_SEQ)
  53                 ghl += GRE_HEADER_SECTION;
  54         if (greh->flags & GRE_CSUM) {
  55                 ghl += GRE_HEADER_SECTION;
  56                 csum = true;
  57         } else
  58                 csum = false;
  59
  60         /* setup inner skb. */
  61         skb->protocol = greh->protocol;
  62         skb->encapsulation = 0;
  63
  64         if (unlikely(!pskb_may_pull(skb, ghl)))
  65                 goto out;
  66
  67         __skb_pull(skb, ghl);
  68         skb_reset_mac_header(skb);
  69         skb_set_network_header(skb, skb_inner_network_offset(skb));
  70         skb->mac_len = skb_inner_network_offset(skb);
  71
  72         /* segment inner packet. */
  73         enc_features = skb->dev->hw_enc_features & netif_skb_features(skb);
  74         segs = skb_mac_gso_segment(skb, enc_features);
  75         if (!segs || IS_ERR(segs))
  76                 goto out;
  77
  78         skb = segs;
  79         tnl_hlen = skb_tnl_header_len(skb);
  80         do {
  81                 __skb_push(skb, ghl);
  82                 if (csum) {
  83                         __be32 *pcsum;
  84
  85                         if (skb_has_shared_frag(skb)) {
  86                                 int err;
  87
  88                                 err = __skb_linearize(skb);
  89                                 if (err) {
  90                                         kfree_skb_list(segs);
  91                                         segs = ERR_PTR(err);
  92                                         goto out;
  93                                 }
  94                         }
  95
  96                         greh = (struct gre_base_hdr *)(skb->data);
  97                         pcsum = (__be32 *)(greh + 1);
  98                         *pcsum = 0;
  99                         *(__sum16 *)pcsum = csum_fold(skb_checksum(skb, 0, skb->len, 0));
 100                 }
 101                 __skb_push(skb, tnl_hlen - ghl);
 102
 103                 skb_reset_inner_headers(skb);
 104                 skb->encapsulation = 1;
 105
 106                 skb_reset_mac_header(skb);
 107                 skb_set_network_header(skb, mac_len);
 108                 skb->mac_len = mac_len;
 109                 skb->protocol = protocol;
 110         } while ((skb = skb->next));
 111 out:
 112         return segs;
 113 }
 114
 115 static const struct net_offload gre_offload = {
 116         .callbacks = {
 117                 .gso_send_check = gre_gso_send_check,
 118                 .gso_segment = gre_gso_segment,
 119         },
 120 };
 121
 122 int __init gre_offload_init(void)
 123 {
 124         return inet_add_offload(&gre_offload, IPPROTO_GRE);
 125 }
 126
 127 void __exit gre_offload_exit(void)
 128 {
 129         inet_del_offload(&gre_offload, IPPROTO_GRE);
 130 }