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         skb_set_mac_header(skb, (prevhdr - x->props.header_len) - skb->data);
  32         skb_set_network_header(skb, -x->props.header_len);
  33         skb->transport_header = skb->network_header + hdr_len;
  34         __skb_pull(skb, hdr_len);
  35         memmove(ipv6_hdr(skb), iph, hdr_len);
  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 xfrm6_transport_input(struct xfrm_state *x, struct sk_buff *skb)
  48 {
  49         int ihl = skb->data - skb_transport_header(skb);
  50
  51         if (skb->transport_header != skb->network_header) {
  52                 memmove(skb_transport_header(skb),
  53                         skb_network_header(skb), ihl);
  54                 skb->network_header = skb->transport_header;
  55         }
  56         ipv6_hdr(skb)->payload_len = htons(skb->len + ihl -
  57                                            sizeof(struct ipv6hdr));
  58         skb_reset_transport_header(skb);
  59         return 0;
  60 }
  61
  62 static struct xfrm_mode xfrm6_transport_mode = {
  63         .input = xfrm6_transport_input,
  64         .output = xfrm6_transport_output,
  65         .owner = THIS_MODULE,
  66         .encap = XFRM_MODE_TRANSPORT,
  67 };
  68
  69 static int __init xfrm6_transport_init(void)
  70 {
  71         return xfrm_register_mode(&xfrm6_transport_mode, AF_INET6);
  72 }
  73
  74 static void __exit xfrm6_transport_exit(void)
  75 {
  76         int err;
  77
  78         err = xfrm_unregister_mode(&xfrm6_transport_mode, AF_INET6);
  79         BUG_ON(err);
  80 }
  81
  82 module_init(xfrm6_transport_init);
  83 module_exit(xfrm6_transport_exit);
  84 MODULE_LICENSE("GPL");
  85 MODULE_ALIAS_XFRM_MODE(AF_INET6, XFRM_MODE_TRANSPORT);