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->h.raw = skb->nh.raw;
  30         skb->h.raw += ihl;
  31
  32         skb_push(skb, x->props.header_len);
  33         skb_reset_network_header(skb);
  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->h.raw;
  49
  50         if (skb->h.raw != skb->nh.raw) {
  51                 memmove(skb->h.raw, skb_network_header(skb), ihl);
  52                 skb->nh.raw = skb->h.raw;
  53         }
  54         ip_hdr(skb)->tot_len = htons(skb->len + ihl);
  55         skb->h.raw = skb->data;
  56         return 0;
  57 }
  58
  59 static struct xfrm_mode xfrm4_transport_mode = {
  60         .input = xfrm4_transport_input,
  61         .output = xfrm4_transport_output,
  62         .owner = THIS_MODULE,
  63         .encap = XFRM_MODE_TRANSPORT,
  64 };
  65
  66 static int __init xfrm4_transport_init(void)
  67 {
  68         return xfrm_register_mode(&xfrm4_transport_mode, AF_INET);
  69 }
  70
  71 static void __exit xfrm4_transport_exit(void)
  72 {
  73         int err;
  74
  75         err = xfrm_unregister_mode(&xfrm4_transport_mode, AF_INET);
  76         BUG_ON(err);
  77 }
  78
  79 module_init(xfrm4_transport_init);
  80 module_exit(xfrm4_transport_exit);
  81 MODULE_LICENSE("GPL");
  82 MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TRANSPORT);