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 static const struct net_offload gre_offload = {
 120         .callbacks = {
 121                 .gso_send_check = gre_gso_send_check,
 122                 .gso_segment = gre_gso_segment,
 123         },
 124 };
 125
 126 int __init gre_offload_init(void)
 127 {
 128         return inet_add_offload(&gre_offload, IPPROTO_GRE);
 129 }
 130
 131 void __exit gre_offload_exit(void)
 132 {
 133         inet_del_offload(&gre_offload, IPPROTO_GRE);
 134 }