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  */
  24 static int xfrm4_beet_output(struct xfrm_state *x, struct sk_buff *skb)
  25 {
  26         struct ip_beet_phdr *ph;
  27         struct iphdr *iph, *top_iph;
  28         int hdrlen, optlen;
  29
  30         iph = ip_hdr(skb);
  31
  32         hdrlen = 0;
  33         optlen = iph->ihl * 4 - sizeof(*iph);
  34         if (unlikely(optlen))
  35                 hdrlen += IPV4_BEET_PHMAXLEN - (optlen & 4);
  36
  37         skb_set_network_header(skb, IPV4_BEET_PHMAXLEN - x->props.header_len -
  38                                     hdrlen);
  39         skb->mac_header = skb->network_header +
  40                           offsetof(struct iphdr, protocol);
  41         skb->transport_header = skb->network_header + sizeof(*iph);
  42
  43         ph = (struct ip_beet_phdr *)__skb_pull(skb, sizeof(*iph) - hdrlen);
  44
  45         top_iph = ip_hdr(skb);
  46
  47         top_iph->ihl = 5;
  48         top_iph->version = 4;
  49
  50         top_iph->protocol = XFRM_MODE_SKB_CB(skb)->protocol;
  51         top_iph->tos = XFRM_MODE_SKB_CB(skb)->tos;
  52
  53         top_iph->id = XFRM_MODE_SKB_CB(skb)->id;
  54         top_iph->frag_off = XFRM_MODE_SKB_CB(skb)->frag_off;
  55         top_iph->ttl = XFRM_MODE_SKB_CB(skb)->ttl;
  56
  57         if (unlikely(optlen)) {
  58                 BUG_ON(optlen < 0);
  59
  60                 ph->padlen = 4 - (optlen & 4);
  61                 ph->hdrlen = optlen / 8;
  62                 ph->nexthdr = top_iph->protocol;
  63                 if (ph->padlen)
  64                         memset(ph + 1, IPOPT_NOP, ph->padlen);
  65
  66                 top_iph->protocol = IPPROTO_BEETPH;
  67                 top_iph->ihl = sizeof(struct iphdr) / 4;
  68         }
  69
  70         top_iph->saddr = x->props.saddr.a4;
  71         top_iph->daddr = x->id.daddr.a4;
  72
  73         return 0;
  74 }
  75
  76 static int xfrm4_beet_input(struct xfrm_state *x, struct sk_buff *skb)
  77 {
  78         struct iphdr *iph = ip_hdr(skb);
  79         int phlen = 0;
  80         int optlen = 0;
  81         u8 ph_nexthdr = 0;
  82         int err = -EINVAL;
  83
  84         if (unlikely(iph->protocol == IPPROTO_BEETPH)) {
  85                 struct ip_beet_phdr *ph;
  86
  87                 if (!pskb_may_pull(skb, sizeof(*ph)))
  88                         goto out;
  89                 ph = (struct ip_beet_phdr *)(ipip_hdr(skb) + 1);
  90
  91                 phlen = sizeof(*ph) + ph->padlen;
  92                 optlen = ph->hdrlen * 8 + (IPV4_BEET_PHMAXLEN - phlen);
  93                 if (optlen < 0 || optlen & 3 || optlen > 250)
  94                         goto out;
  95
  96                 if (!pskb_may_pull(skb, phlen + optlen))
  97                         goto out;
  98                 skb->len -= phlen + optlen;
  99
 100                 ph_nexthdr = ph->nexthdr;
 101         }
 102
 103         skb_set_network_header(skb, phlen - sizeof(*iph));
 104         memmove(skb_network_header(skb), iph, sizeof(*iph));
 105         skb_set_transport_header(skb, phlen + optlen);
 106         skb->data = skb_transport_header(skb);
 107
 108         iph = ip_hdr(skb);
 109         iph->ihl = (sizeof(*iph) + optlen) / 4;
 110         iph->tot_len = htons(skb->len + iph->ihl * 4);
 111         iph->daddr = x->sel.daddr.a4;
 112         iph->saddr = x->sel.saddr.a4;
 113         if (ph_nexthdr)
 114                 iph->protocol = ph_nexthdr;
 115         iph->check = 0;
 116         iph->check = ip_fast_csum(skb_network_header(skb), iph->ihl);
 117         err = 0;
 118 out:
 119         return err;
 120 }
 121
 122 static struct xfrm_mode xfrm4_beet_mode = {
 123         .input = xfrm4_beet_input,
 124         .output2 = xfrm4_beet_output,
 125         .output = xfrm4_prepare_output,
 126         .owner = THIS_MODULE,
 127         .encap = XFRM_MODE_BEET,
 128         .flags = XFRM_MODE_FLAG_TUNNEL,
 129 };
 130
 131 static int __init xfrm4_beet_init(void)
 132 {
 133         return xfrm_register_mode(&xfrm4_beet_mode, AF_INET);
 134 }
 135
 136 static void __exit xfrm4_beet_exit(void)
 137 {
 138         int err;
 139
 140         err = xfrm_unregister_mode(&xfrm4_beet_mode, AF_INET);
 141         BUG_ON(err);
 142 }
 143
 144 module_init(xfrm4_beet_init);
 145 module_exit(xfrm4_beet_exit);
 146 MODULE_LICENSE("GPL");
 147 MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_BEET);