net/ipv6/xfrm6_mode_transport.c

   1 /*
   2  * xfrm6_mode_transport.c - Transport mode encapsulation for IPv6.
   3  *
   4  * Copyright (C) 2002 USAGI/WIDE Project
   5  * Copyright (c) 2004-2006 Herbert Xu <herbert@gondor.apana.org.au>
   6  */
   7
   8 #include <linux/init.h>
   9 #include <linux/kernel.h>
  10 #include <linux/module.h>
  11 #include <linux/skbuff.h>
  12 #include <linux/stringify.h>
  13 #include <net/dst.h>
  14 #include <net/ipv6.h>
  15 #include <net/xfrm.h>
  16
  17 /* Add encapsulation header.
  18  *
  19  * The IP header and mutable extension headers will be moved forward to make
  20  * space for the encapsulation header.
  21  *
  22  * On exit, skb->h will be set to the start of the encapsulation header to be
  23  * filled in by x->type->output and skb->nh will be set to the nextheader field
  24  * of the extension header directly preceding the encapsulation header, or in
  25  * its absence, that of the top IP header.  The value of skb->data will always
  26  * point to the top IP header.
  27  */
  28 static int xfrm6_transport_output(struct sk_buff *skb)
  29 {
  30         struct xfrm_state *x = skb->dst->xfrm;
  31         struct ipv6hdr *iph;
  32         u8 *prevhdr;
  33         int hdr_len;
  34
  35         skb_push(skb, x->props.header_len);
  36         iph = skb->nh.ipv6h;
  37
  38         hdr_len = ip6_find_1stfragopt(skb, &prevhdr);
  39         skb->nh.raw = prevhdr - x->props.header_len;
  40         skb->h.raw = skb->data + hdr_len;
  41         memmove(skb->data, iph, hdr_len);
  42         return 0;
  43 }
  44
  45 /* Remove encapsulation header.
  46  *
  47  * The IP header will be moved over the top of the encapsulation header.
  48  *
  49  * On entry, skb->h shall point to where the IP header should be and skb->nh
  50  * shall be set to where the IP header currently is.  skb->data shall point
  51  * to the start of the payload.
  52  */
  53 static int xfrm6_transport_input(struct xfrm_state *x, struct sk_buff *skb)
  54 {
  55         int ihl = skb->data - skb->h.raw;
  56
  57         if (skb->h.raw != skb->nh.raw)
  58                 skb->nh.raw = memmove(skb->h.raw, skb->nh.raw, ihl);
  59         skb->nh.ipv6h->payload_len = htons(skb->len + ihl -
  60                                            sizeof(struct ipv6hdr));
  61         skb->h.raw = skb->data;
  62         return 0;
  63 }
  64
  65 static struct xfrm_mode xfrm6_transport_mode = {
  66         .input = xfrm6_transport_input,
  67         .output = xfrm6_transport_output,
  68         .owner = THIS_MODULE,
  69         .encap = XFRM_MODE_TRANSPORT,
  70 };
  71
  72 static int __init xfrm6_transport_init(void)
  73 {
  74         return xfrm_register_mode(&xfrm6_transport_mode, AF_INET6);
  75 }
  76
  77 static void __exit xfrm6_transport_exit(void)
  78 {
  79         int err;
  80
  81         err = xfrm_unregister_mode(&xfrm6_transport_mode, AF_INET6);
  82         BUG_ON(err);
  83 }
  84
  85 module_init(xfrm6_transport_init);
  86 module_exit(xfrm6_transport_exit);
  87 MODULE_LICENSE("GPL");
  88 MODULE_ALIAS_XFRM_MODE(AF_INET6, XFRM_MODE_TRANSPORT);