net/ipv4/xfrm4_mode_beet.c

   1 /*
   2  * xfrm4_mode_beet.c - BEET mode encapsulation for IPv4.
   3  *
   4  * Copyright (c) 2006 Diego Beltrami <diego.beltrami@gmail.com>
   5  *                    Miika Komu     <miika@iki.fi>
   6  *                    Herbert Xu     <herbert@gondor.apana.org.au>
   7  *                    Abhinav Pathak <abhinav.pathak@hiit.fi>
   8  *                    Jeff Ahrenholz <ahrenholz@gmail.com>
   9  */
  10
  11 #include <linux/init.h>
  12 #include <linux/kernel.h>
  13 #include <linux/module.h>
  14 #include <linux/skbuff.h>
  15 #include <linux/stringify.h>
  16 #include <net/dst.h>
  17 #include <net/ip.h>
  18 #include <net/xfrm.h>
  19
  20 /* Add encapsulation header.
  21  *
  22  * The top IP header will be constructed per draft-nikander-esp-beet-mode-06.txt.
  23  * The following fields in it shall be filled in by x->type->output:
  24  *      tot_len
  25  *      check
  26  *
  27  * On exit, skb->h will be set to the start of the payload to be processed
  28  * by x->type->output and skb->nh will be set to the top IP header.
  29  */
  30 static int xfrm4_beet_output(struct xfrm_state *x, struct sk_buff *skb)
  31 {
  32         struct iphdr *iph, *top_iph = NULL;
  33         int hdrlen, optlen;
  34
  35         iph = skb->nh.iph;
  36         skb->h.ipiph = iph;
  37
  38         hdrlen = 0;
  39         optlen = iph->ihl * 4 - sizeof(*iph);
  40         if (unlikely(optlen))
  41                 hdrlen += IPV4_BEET_PHMAXLEN - (optlen & 4);
  42
  43         skb->nh.raw = skb_push(skb, x->props.header_len + hdrlen);
  44         top_iph = skb->nh.iph;
  45         hdrlen = iph->ihl * 4 - optlen;
  46         skb->h.raw += hdrlen;
  47
  48         memmove(top_iph, iph, hdrlen);
  49         if (unlikely(optlen)) {
  50                 struct ip_beet_phdr *ph;
  51
  52                 BUG_ON(optlen < 0);
  53
  54                 ph = (struct ip_beet_phdr *)skb->h.raw;
  55                 ph->padlen = 4 - (optlen & 4);
  56                 ph->hdrlen = (optlen + ph->padlen + sizeof(*ph)) / 8;
  57                 ph->nexthdr = top_iph->protocol;
  58
  59                 top_iph->protocol = IPPROTO_BEETPH;
  60                 top_iph->ihl = sizeof(struct iphdr) / 4;
  61         }
  62
  63         top_iph->saddr = x->props.saddr.a4;
  64         top_iph->daddr = x->id.daddr.a4;
  65
  66         return 0;
  67 }
  68
  69 static int xfrm4_beet_input(struct xfrm_state *x, struct sk_buff *skb)
  70 {
  71         struct iphdr *iph = skb->nh.iph;
  72         int phlen = 0;
  73         int optlen = 0;
  74         __u8 ph_nexthdr = 0, protocol = 0;
  75         int err = -EINVAL;
  76
  77         protocol = iph->protocol;
  78
  79         if (unlikely(iph->protocol == IPPROTO_BEETPH)) {
  80                 struct ip_beet_phdr *ph = (struct ip_beet_phdr*)(iph + 1);
  81
  82                 if (!pskb_may_pull(skb, sizeof(*ph)))
  83                         goto out;
  84
  85                 phlen = ph->hdrlen * 8;
  86                 optlen = phlen - ph->padlen - sizeof(*ph);
  87                 if (optlen < 0 || optlen & 3 || optlen > 250)
  88                         goto out;
  89
  90                 if (!pskb_may_pull(skb, phlen))
  91                         goto out;
  92
  93                 ph_nexthdr = ph->nexthdr;
  94         }
  95
  96         skb_push(skb, sizeof(*iph) - phlen + optlen);
  97         memmove(skb->data, skb->nh.raw, sizeof(*iph));
  98         skb->nh.raw = skb->data;
  99
 100         iph = skb->nh.iph;
 101         iph->ihl = (sizeof(*iph) + optlen) / 4;
 102         iph->tot_len = htons(skb->len);
 103         iph->daddr = x->sel.daddr.a4;
 104         iph->saddr = x->sel.saddr.a4;
 105         if (ph_nexthdr)
 106                 iph->protocol = ph_nexthdr;
 107         else
 108                 iph->protocol = protocol;
 109         iph->check = 0;
 110         iph->check = ip_fast_csum(skb->nh.raw, iph->ihl);
 111         err = 0;
 112 out:
 113         return err;
 114 }
 115
 116 static struct xfrm_mode xfrm4_beet_mode = {
 117         .input = xfrm4_beet_input,
 118         .output = xfrm4_beet_output,
 119         .owner = THIS_MODULE,
 120         .encap = XFRM_MODE_BEET,
 121 };
 122
 123 static int __init xfrm4_beet_init(void)
 124 {
 125         return xfrm_register_mode(&xfrm4_beet_mode, AF_INET);
 126 }
 127
 128 static void __exit xfrm4_beet_exit(void)
 129 {
 130         int err;
 131
 132         err = xfrm_unregister_mode(&xfrm4_beet_mode, AF_INET);
 133         BUG_ON(err);
 134 }
 135
 136 module_init(xfrm4_beet_init);
 137 module_exit(xfrm4_beet_exit);
 138 MODULE_LICENSE("GPL");
 139 MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_BEET);