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 static void xfrm4_beet_make_header(struct sk_buff *skb)
  21 {
  22         struct iphdr *iph = ip_hdr(skb);
  23
  24         iph->ihl = 5;
  25         iph->version = 4;
  26
  27         iph->protocol = XFRM_MODE_SKB_CB(skb)->protocol;
  28         iph->tos = XFRM_MODE_SKB_CB(skb)->tos;
  29
  30         iph->id = XFRM_MODE_SKB_CB(skb)->id;
  31         iph->frag_off = XFRM_MODE_SKB_CB(skb)->frag_off;
  32         iph->ttl = XFRM_MODE_SKB_CB(skb)->ttl;
  33 }
  34
  35 /* Add encapsulation header.
  36  *
  37  * The top IP header will be constructed per draft-nikander-esp-beet-mode-06.txt.
  38  */
  39 static int xfrm4_beet_output(struct xfrm_state *x, struct sk_buff *skb)
  40 {
  41         struct ip_beet_phdr *ph;
  42         struct iphdr *top_iph;
  43         int hdrlen, optlen;
  44
  45         hdrlen = 0;
  46         optlen = XFRM_MODE_SKB_CB(skb)->optlen;
  47         if (unlikely(optlen))
  48                 hdrlen += IPV4_BEET_PHMAXLEN - (optlen & 4);
  49
  50         skb_set_network_header(skb, -x->props.header_len -
  51                                     hdrlen + (XFRM_MODE_SKB_CB(skb)->ihl - sizeof(*top_iph)));
  52         if (x->sel.family != AF_INET6)
  53                 skb->network_header += IPV4_BEET_PHMAXLEN;
  54         skb->mac_header = skb->network_header +
  55                           offsetof(struct iphdr, protocol);
  56         skb->transport_header = skb->network_header + sizeof(*top_iph);
  57
  58         xfrm4_beet_make_header(skb);
  59
  60         ph = (struct ip_beet_phdr *)
  61                 __skb_pull(skb, XFRM_MODE_SKB_CB(skb)->ihl - hdrlen);
  62
  63         top_iph = ip_hdr(skb);
  64
  65         if (unlikely(optlen)) {
  66                 BUG_ON(optlen < 0);
  67
  68                 ph->padlen = 4 - (optlen & 4);
  69                 ph->hdrlen = optlen / 8;
  70                 ph->nexthdr = top_iph->protocol;
  71                 if (ph->padlen)
  72                         memset(ph + 1, IPOPT_NOP, ph->padlen);
  73
  74                 top_iph->protocol = IPPROTO_BEETPH;
  75                 top_iph->ihl = sizeof(struct iphdr) / 4;
  76         }
  77
  78         top_iph->saddr = x->props.saddr.a4;
  79         top_iph->daddr = x->id.daddr.a4;
  80
  81         return 0;
  82 }
  83
  84 static int xfrm4_beet_input(struct xfrm_state *x, struct sk_buff *skb)
  85 {
  86         struct iphdr *iph;
  87         int optlen = 0;
  88         int err = -EINVAL;
  89
  90         if (unlikely(XFRM_MODE_SKB_CB(skb)->protocol == IPPROTO_BEETPH)) {
  91                 struct ip_beet_phdr *ph;
  92                 int phlen;
  93
  94                 if (!pskb_may_pull(skb, sizeof(*ph)))
  95                         goto out;
  96
  97                 ph = (struct ip_beet_phdr *)skb->data;
  98
  99                 phlen = sizeof(*ph) + ph->padlen;
 100                 optlen = ph->hdrlen * 8 + (IPV4_BEET_PHMAXLEN - phlen);
 101                 if (optlen < 0 || optlen & 3 || optlen > 250)
 102                         goto out;
 103
 104                 XFRM_MODE_SKB_CB(skb)->protocol = ph->nexthdr;
 105
 106                 if (!pskb_may_pull(skb, phlen))
 107                         goto out;
 108                 __skb_pull(skb, phlen);
 109         }
 110
 111         skb_push(skb, sizeof(*iph));
 112         skb_reset_network_header(skb);
 113         skb_mac_header_rebuild(skb);
 114
 115         xfrm4_beet_make_header(skb);
 116
 117         iph = ip_hdr(skb);
 118
 119         iph->ihl += optlen / 4;
 120         iph->tot_len = htons(skb->len);
 121         iph->daddr = x->sel.daddr.a4;
 122         iph->saddr = x->sel.saddr.a4;
 123         iph->check = 0;
 124         iph->check = ip_fast_csum(skb_network_header(skb), iph->ihl);
 125         err = 0;
 126 out:
 127         return err;
 128 }
 129
 130 static struct xfrm_mode xfrm4_beet_mode = {
 131         .input2 = xfrm4_beet_input,
 132         .input = xfrm_prepare_input,
 133         .output2 = xfrm4_beet_output,
 134         .output = xfrm4_prepare_output,
 135         .owner = THIS_MODULE,
 136         .encap = XFRM_MODE_BEET,
 137         .flags = XFRM_MODE_FLAG_TUNNEL,
 138 };
 139
 140 static int __init xfrm4_beet_init(void)
 141 {
 142         return xfrm_register_mode(&xfrm4_beet_mode, AF_INET);
 143 }
 144
 145 static void __exit xfrm4_beet_exit(void)
 146 {
 147         int err;
 148
 149         err = xfrm_unregister_mode(&xfrm4_beet_mode, AF_INET);
 150         BUG_ON(err);
 151 }
 152
 153 module_init(xfrm4_beet_init);
 154 module_exit(xfrm4_beet_exit);
 155 MODULE_LICENSE("GPL");
 156 MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_BEET);