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
  16 /* Add encapsulation header.
  17  *
  18  * The IP header will be moved forward to make space for the encapsulation
  19  * header.
  20  *
  21  * On exit, skb->h will be set to the start of the payload to be processed
  22  * by x->type->output and skb->nh will be set to the top IP header.
  23  */
  24 static int xfrm4_transport_output(struct xfrm_state *x, struct sk_buff *skb)
  25 {
  26         struct iphdr *iph;
  27         int ihl;
  28
  29         iph = skb->nh.iph;
  30         skb->h.ipiph = iph;
  31
  32         ihl = iph->ihl * 4;
  33         skb->h.raw += ihl;
  34
  35         skb->nh.raw = memmove(skb_push(skb, x->props.header_len), iph, ihl);
  36         return 0;
  37 }
  38
  39 /* Remove encapsulation header.
  40  *
  41  * The IP header will be moved over the top of the encapsulation header.
  42  *
  43  * On entry, skb->h shall point to where the IP header should be and skb->nh
  44  * shall be set to where the IP header currently is.  skb->data shall point
  45  * to the start of the payload.
  46  */
  47 static int xfrm4_transport_input(struct xfrm_state *x, struct sk_buff *skb)
  48 {
  49         int ihl = skb->data - skb->h.raw;
  50
  51         if (skb->h.raw != skb->nh.raw)
  52                 skb->nh.raw = memmove(skb->h.raw, skb->nh.raw, ihl);
  53         skb->nh.iph->tot_len = htons(skb->len + ihl);
  54         skb->h.raw = skb->data;
  55         return 0;
  56 }
  57
  58 static struct xfrm_mode xfrm4_transport_mode = {
  59         .input = xfrm4_transport_input,
  60         .output = xfrm4_transport_output,
  61         .owner = THIS_MODULE,
  62         .encap = XFRM_MODE_TRANSPORT,
  63 };
  64
  65 static int __init xfrm4_transport_init(void)
  66 {
  67         return xfrm_register_mode(&xfrm4_transport_mode, AF_INET);
  68 }
  69
  70 static void __exit xfrm4_transport_exit(void)
  71 {
  72         int err;
  73
  74         err = xfrm_unregister_mode(&xfrm4_transport_mode, AF_INET);
  75         BUG_ON(err);
  76 }
  77
  78 module_init(xfrm4_transport_init);
  79 module_exit(xfrm4_transport_exit);
  80 MODULE_LICENSE("GPL");
  81 MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TRANSPORT);