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 static int xfrm6_transport_output(struct xfrm_state *x, struct sk_buff *skb)
  23 {
  24         struct ipv6hdr *iph;
  25         u8 *prevhdr;
  26         int hdr_len;
  27
  28         iph = ipv6_hdr(skb);
  29
  30         hdr_len = x->type->hdr_offset(x, skb, &prevhdr);
  31         if (hdr_len < 0)
  32                 return hdr_len;
  33         skb_set_mac_header(skb, (prevhdr - x->props.header_len) - skb->data);
  34         skb_set_network_header(skb, -x->props.header_len);
  35         skb->transport_header = skb->network_header + hdr_len;
  36         __skb_pull(skb, hdr_len);
  37         memmove(ipv6_hdr(skb), iph, hdr_len);
  38         return 0;
  39 }
  40
  41 /* Remove encapsulation header.
  42  *
  43  * The IP header will be moved over the top of the encapsulation header.
  44  *
  45  * On entry, skb->h shall point to where the IP header should be and skb->nh
  46  * shall be set to where the IP header currently is.  skb->data shall point
  47  * to the start of the payload.
  48  */
  49 static int xfrm6_transport_input(struct xfrm_state *x, struct sk_buff *skb)
  50 {
  51         int ihl = skb->data - skb_transport_header(skb);
  52
  53         if (skb->transport_header != skb->network_header) {
  54                 memmove(skb_transport_header(skb),
  55                         skb_network_header(skb), ihl);
  56                 skb->network_header = skb->transport_header;
  57         }
  58         ipv6_hdr(skb)->payload_len = htons(skb->len + ihl -
  59                                            sizeof(struct ipv6hdr));
  60         skb_reset_transport_header(skb);
  61         return 0;
  62 }
  63
  64 static struct xfrm_mode xfrm6_transport_mode = {
  65         .input = xfrm6_transport_input,
  66         .output = xfrm6_transport_output,
  67         .owner = THIS_MODULE,
  68         .encap = XFRM_MODE_TRANSPORT,
  69 };
  70
  71 static int __init xfrm6_transport_init(void)
  72 {
  73         return xfrm_register_mode(&xfrm6_transport_mode, AF_INET6);
  74 }
  75
  76 static void __exit xfrm6_transport_exit(void)
  77 {
  78         int err;
  79
  80         err = xfrm_unregister_mode(&xfrm6_transport_mode, AF_INET6);
  81         BUG_ON(err);
  82 }
  83
  84 module_init(xfrm6_transport_init);
  85 module_exit(xfrm6_transport_exit);
  86 MODULE_LICENSE("GPL");
  87 MODULE_ALIAS_XFRM_MODE(AF_INET6, XFRM_MODE_TRANSPORT);