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 = ip_hdr(skb);
  27         int ihl = iph->ihl * 4;
  28
  29         skb->transport_header = skb->network_header + ihl;
  30         skb_push(skb, x->props.header_len);
  31         skb_reset_network_header(skb);
  32         memmove(skb_network_header(skb), iph, ihl);
  33         return 0;
  34 }
  35
  36 /* Remove encapsulation header.
  37  *
  38  * The IP header will be moved over the top of the encapsulation header.
  39  *
  40  * On entry, skb->h shall point to where the IP header should be and skb->nh
  41  * shall be set to where the IP header currently is.  skb->data shall point
  42  * to the start of the payload.
  43  */
  44 static int xfrm4_transport_input(struct xfrm_state *x, struct sk_buff *skb)
  45 {
  46         int ihl = skb->data - skb_transport_header(skb);
  47
  48         if (skb->transport_header != skb->network_header) {
  49                 memmove(skb_transport_header(skb),
  50                         skb_network_header(skb), ihl);
  51                 skb->network_header = skb->transport_header;
  52         }
  53         ip_hdr(skb)->tot_len = htons(skb->len + ihl);
  54         skb_reset_transport_header(skb);
  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);