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;
  33         int hdrlen, optlen;
  34
  35         iph = ip_hdr(skb);
  36         skb->transport_header = skb->network_header;
  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_push(skb, x->props.header_len - IPV4_BEET_PHMAXLEN + hdrlen);
  44         skb_reset_network_header(skb);
  45         top_iph = ip_hdr(skb);
  46         skb->transport_header += sizeof(*iph) - hdrlen;
  47
  48         memmove(top_iph, iph, sizeof(*iph));
  49         if (unlikely(optlen)) {
  50                 struct ip_beet_phdr *ph;
  51
  52                 BUG_ON(optlen < 0);
  53
  54                 ph = (struct ip_beet_phdr *)skb_transport_header(skb);
  55                 ph->padlen = 4 - (optlen & 4);
  56                 ph->hdrlen = optlen / 8;
  57                 ph->nexthdr = top_iph->protocol;
  58                 if (ph->padlen)
  59                         memset(ph + 1, IPOPT_NOP, ph->padlen);
  60
  61                 top_iph->protocol = IPPROTO_BEETPH;
  62                 top_iph->ihl = sizeof(struct iphdr) / 4;
  63         }
  64
  65         top_iph->saddr = x->props.saddr.a4;
  66         top_iph->daddr = x->id.daddr.a4;
  67
  68         return 0;
  69 }
  70
  71 static int xfrm4_beet_input(struct xfrm_state *x, struct sk_buff *skb)
  72 {
  73         struct iphdr *iph = ip_hdr(skb);
  74         int phlen = 0;
  75         int optlen = 0;
  76         u8 ph_nexthdr = 0;
  77         int err = -EINVAL;
  78
  79         if (unlikely(iph->protocol == IPPROTO_BEETPH)) {
  80                 struct ip_beet_phdr *ph;
  81
  82                 if (!pskb_may_pull(skb, sizeof(*ph)))
  83                         goto out;
  84                 ph = (struct ip_beet_phdr *)(ipip_hdr(skb) + 1);
  85
  86                 phlen = sizeof(*ph) + ph->padlen;
  87                 optlen = ph->hdrlen * 8 + (IPV4_BEET_PHMAXLEN - phlen);
  88                 if (optlen < 0 || optlen & 3 || optlen > 250)
  89                         goto out;
  90
  91                 if (!pskb_may_pull(skb, phlen + optlen))
  92                         goto out;
  93                 skb->len -= phlen + optlen;
  94
  95                 ph_nexthdr = ph->nexthdr;
  96         }
  97
  98         skb_set_network_header(skb, phlen - sizeof(*iph));
  99         memmove(skb_network_header(skb), iph, sizeof(*iph));
 100         skb_set_transport_header(skb, phlen + optlen);
 101         skb->data = skb_transport_header(skb);
 102
 103         iph = ip_hdr(skb);
 104         iph->ihl = (sizeof(*iph) + optlen) / 4;
 105         iph->tot_len = htons(skb->len + iph->ihl * 4);
 106         iph->daddr = x->sel.daddr.a4;
 107         iph->saddr = x->sel.saddr.a4;
 108         if (ph_nexthdr)
 109                 iph->protocol = ph_nexthdr;
 110         iph->check = 0;
 111         iph->check = ip_fast_csum(skb_network_header(skb), iph->ihl);
 112         err = 0;
 113 out:
 114         return err;
 115 }
 116
 117 static struct xfrm_mode xfrm4_beet_mode = {
 118         .input = xfrm4_beet_input,
 119         .output = xfrm4_beet_output,
 120         .owner = THIS_MODULE,
 121         .encap = XFRM_MODE_BEET,
 122 };
 123
 124 static int __init xfrm4_beet_init(void)
 125 {
 126         return xfrm_register_mode(&xfrm4_beet_mode, AF_INET);
 127 }
 128
 129 static void __exit xfrm4_beet_exit(void)
 130 {
 131         int err;
 132
 133         err = xfrm_unregister_mode(&xfrm4_beet_mode, AF_INET);
 134         BUG_ON(err);
 135 }
 136
 137 module_init(xfrm4_beet_init);
 138 module_exit(xfrm4_beet_exit);
 139 MODULE_LICENSE("GPL");
 140 MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_BEET);