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