net/ipv4/xfrm4_mode_transport.c

   1 /*
   2  * xfrm4_mode_transport.c - Transport mode encapsulation for IPv4.
   3  *
   4  * Copyright (c) 2004-2006 Herbert Xu <herbert@gondor.apana.org.au>
   5  */
   6
   7 #include <linux/init.h>
   8 #include <linux/kernel.h>
   9 #include <linux/module.h>
  10 #include <linux/skbuff.h>
  11 #include <linux/stringify.h>
  12 #include <net/dst.h>
  13 #include <net/ip.h>
  14 #include <net/xfrm.h>
  15 #include <net/protocol.h>
  16
  17 /* Add encapsulation header.
  18  *
  19  * The IP header will be moved forward to make space for the encapsulation
  20  * header.
  21  */
  22 static int xfrm4_transport_output(struct xfrm_state *x, struct sk_buff *skb)
  23 {
  24         struct iphdr *iph = ip_hdr(skb);
  25         int ihl = iph->ihl * 4;
  26
  27         skb_set_inner_transport_header(skb, skb_transport_offset(skb));
  28
  29         skb_set_network_header(skb, -x->props.header_len);
  30         skb->mac_header = skb->network_header +
  31                           offsetof(struct iphdr, protocol);
  32         skb->transport_header = skb->network_header + ihl;
  33         __skb_pull(skb, ihl);
  34         memmove(skb_network_header(skb), iph, ihl);
  35         return 0;
  36 }
  37
  38 /* Remove encapsulation header.
  39  *
  40  * The IP header will be moved over the top of the encapsulation header.
  41  *
  42  * On entry, skb->h shall point to where the IP header should be and skb->nh
  43  * shall be set to where the IP header currently is.  skb->data shall point
  44  * to the start of the payload.
  45  */
  46 static int xfrm4_transport_input(struct xfrm_state *x, struct sk_buff *skb)
  47 {
  48         int ihl = skb->data - skb_transport_header(skb);
  49
  50         if (skb->transport_header != skb->network_header) {
  51                 memmove(skb_transport_header(skb),
  52                         skb_network_header(skb), ihl);
  53                 skb->network_header = skb->transport_header;
  54         }
  55         ip_hdr(skb)->tot_len = htons(skb->len + ihl);
  56         skb_reset_transport_header(skb);
  57         return 0;
  58 }
  59
  60 static struct sk_buff *xfrm4_transport_gso_segment(struct xfrm_state *x,
  61                                                    struct sk_buff *skb,
  62                                                    netdev_features_t features)
  63 {
  64         const struct net_offload *ops;
  65         struct sk_buff *segs = ERR_PTR(-EINVAL);
  66         struct xfrm_offload *xo = xfrm_offload(skb);
  67
  68         skb->transport_header += x->props.header_len;
  69         ops = rcu_dereference(inet_offloads[xo->proto]);
  70         if (likely(ops && ops->callbacks.gso_segment))
  71                 segs = ops->callbacks.gso_segment(skb, features);
  72
  73         return segs;
  74 }
  75
  76 static void xfrm4_transport_xmit(struct xfrm_state *x, struct sk_buff *skb)
  77 {
  78         struct xfrm_offload *xo = xfrm_offload(skb);
  79
  80         skb_reset_mac_len(skb);
  81         pskb_pull(skb, skb->mac_len + sizeof(struct iphdr) + x->props.header_len);
  82
  83         if (xo->flags & XFRM_GSO_SEGMENT) {
  84                  skb_reset_transport_header(skb);
  85                  skb->transport_header -= x->props.header_len;
  86         }
  87 }
  88
  89 static struct xfrm_mode xfrm4_transport_mode = {
  90         .input = xfrm4_transport_input,
  91         .output = xfrm4_transport_output,
  92         .gso_segment = xfrm4_transport_gso_segment,
  93         .xmit = xfrm4_transport_xmit,
  94         .owner = THIS_MODULE,
  95         .encap = XFRM_MODE_TRANSPORT,
  96 };
  97
  98 static int __init xfrm4_transport_init(void)
  99 {
 100         return xfrm_register_mode(&xfrm4_transport_mode, AF_INET);
 101 }
 102
 103 static void __exit xfrm4_transport_exit(void)
 104 {
 105         int err;
 106
 107         err = xfrm_unregister_mode(&xfrm4_transport_mode, AF_INET);
 108         BUG_ON(err);
 109 }
 110
 111 module_init(xfrm4_transport_init);
 112 module_exit(xfrm4_transport_exit);
 113 MODULE_LICENSE("GPL");
 114 MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TRANSPORT);