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