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   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 static int xfrm4_beet_output(struct xfrm_state *x, struct sk_buff *skb)
  28 {
  29         struct ip_beet_phdr *ph;
  30         struct iphdr *iph, *top_iph;
  31         int hdrlen, optlen;
  32
  33         iph = ip_hdr(skb);
  34
  35         hdrlen = 0;
  36         optlen = iph->ihl * 4 - sizeof(*iph);
  37         if (unlikely(optlen))
  38                 hdrlen += IPV4_BEET_PHMAXLEN - (optlen & 4);
  39
  40         skb_set_network_header(skb, IPV4_BEET_PHMAXLEN - x->props.header_len -
  41                                     hdrlen);
  42         skb->mac_header = skb->network_header +
  43                           offsetof(struct iphdr, protocol);
  44         skb->transport_header = skb->network_header + sizeof(*iph);
  45
  46         ph = (struct ip_beet_phdr *)__skb_pull(skb, sizeof(*iph) - hdrlen);
  47
  48         top_iph = ip_hdr(skb);
  49         memmove(top_iph, iph, sizeof(*iph));
  50         if (unlikely(optlen)) {
  51                 BUG_ON(optlen < 0);
  52
  53                 ph->padlen = 4 - (optlen & 4);
  54                 ph->hdrlen = optlen / 8;
  55                 ph->nexthdr = top_iph->protocol;
  56                 if (ph->padlen)
  57                         memset(ph + 1, IPOPT_NOP, ph->padlen);
  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 = ip_hdr(skb);
  72         int phlen = 0;
  73         int optlen = 0;
  74         u8 ph_nexthdr = 0;
  75         int err = -EINVAL;
  76
  77         if (unlikely(iph->protocol == IPPROTO_BEETPH)) {
  78                 struct ip_beet_phdr *ph;
  79
  80                 if (!pskb_may_pull(skb, sizeof(*ph)))
  81                         goto out;
  82                 ph = (struct ip_beet_phdr *)(ipip_hdr(skb) + 1);
  83
  84                 phlen = sizeof(*ph) + ph->padlen;
  85                 optlen = ph->hdrlen * 8 + (IPV4_BEET_PHMAXLEN - phlen);
  86                 if (optlen < 0 || optlen & 3 || optlen > 250)
  87                         goto out;
  88
  89                 if (!pskb_may_pull(skb, phlen + optlen))
  90                         goto out;
  91                 skb->len -= phlen + optlen;
  92
  93                 ph_nexthdr = ph->nexthdr;
  94         }
  95
  96         skb_set_network_header(skb, phlen - sizeof(*iph));
  97         memmove(skb_network_header(skb), iph, sizeof(*iph));
  98         skb_set_transport_header(skb, phlen + optlen);
  99         skb->data = skb_transport_header(skb);
 100
 101         iph = ip_hdr(skb);
 102         iph->ihl = (sizeof(*iph) + optlen) / 4;
 103         iph->tot_len = htons(skb->len + iph->ihl * 4);
 104         iph->daddr = x->sel.daddr.a4;
 105         iph->saddr = x->sel.saddr.a4;
 106         if (ph_nexthdr)
 107                 iph->protocol = ph_nexthdr;
 108         iph->check = 0;
 109         iph->check = ip_fast_csum(skb_network_header(skb), iph->ihl);
 110         err = 0;
 111 out:
 112         return err;
 113 }
 114
 115 static struct xfrm_mode xfrm4_beet_mode = {
 116         .input = xfrm4_beet_input,
 117         .output = xfrm4_beet_output,
 118         .owner = THIS_MODULE,
 119         .encap = XFRM_MODE_BEET,
 120 };
 121
 122 static int __init xfrm4_beet_init(void)
 123 {
 124         return xfrm_register_mode(&xfrm4_beet_mode, AF_INET);
 125 }
 126
 127 static void __exit xfrm4_beet_exit(void)
 128 {
 129         int err;
 130
 131         err = xfrm_unregister_mode(&xfrm4_beet_mode, AF_INET);
 132         BUG_ON(err);
 133 }
 134
 135 module_init(xfrm4_beet_init);
 136 module_exit(xfrm4_beet_exit);
 137 MODULE_LICENSE("GPL");
 138 MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_BEET);