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/*
* xfrm4_mode_beet.c - BEET mode encapsulation for IPv4.
*
* Copyright (c) 2006 Diego Beltrami <diego.beltrami@gmail.com>
* Miika Komu <miika@iki.fi>
* Herbert Xu <herbert@gondor.apana.org.au>
* Abhinav Pathak <abhinav.pathak@hiit.fi>
* Jeff Ahrenholz <ahrenholz@gmail.com>
*/

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/stringify.h>
#include <net/dst.h>
#include <net/ip.h>
#include <net/xfrm.h>

static void xfrm4_beet_make_header(struct sk_buff *skb)
{
struct iphdr *iph = ip_hdr(skb);

iph->ihl = 5;
iph->version = 4;

iph->protocol = XFRM_MODE_SKB_CB(skb)->protocol;
iph->tos = XFRM_MODE_SKB_CB(skb)->tos;

iph->id = XFRM_MODE_SKB_CB(skb)->id;
iph->frag_off = XFRM_MODE_SKB_CB(skb)->frag_off;
iph->ttl = XFRM_MODE_SKB_CB(skb)->ttl;
}

/* Add encapsulation header.
*
* The top IP header will be constructed per draft-nikander-esp-beet-mode-06.txt.
*/
static int xfrm4_beet_output(struct xfrm_state *x, struct sk_buff *skb)
{
struct ip_beet_phdr *ph;
struct iphdr *top_iph;
int hdrlen, optlen;

hdrlen = 0;
optlen = XFRM_MODE_SKB_CB(skb)->optlen;
if (unlikely(optlen))
hdrlen += IPV4_BEET_PHMAXLEN - (optlen & 4);

skb_set_network_header(skb, -x->props.header_len -
hdrlen + (XFRM_MODE_SKB_CB(skb)->ihl - sizeof(*top_iph)));
if (x->sel.family != AF_INET6)
skb->network_header += IPV4_BEET_PHMAXLEN;
skb->mac_header = skb->network_header +
offsetof(struct iphdr, protocol);
skb->transport_header = skb->network_header + sizeof(*top_iph);

xfrm4_beet_make_header(skb);

ph = (struct ip_beet_phdr *)
__skb_pull(skb, XFRM_MODE_SKB_CB(skb)->ihl - hdrlen);

top_iph = ip_hdr(skb);

if (unlikely(optlen)) {
BUG_ON(optlen < 0);

ph->padlen = 4 - (optlen & 4);
ph->hdrlen = optlen / 8;
ph->nexthdr = top_iph->protocol;
if (ph->padlen)
memset(ph + 1, IPOPT_NOP, ph->padlen);

top_iph->protocol = IPPROTO_BEETPH;
top_iph->ihl = sizeof(struct iphdr) / 4;
}

top_iph->saddr = x->props.saddr.a4;
top_iph->daddr = x->id.daddr.a4;

return 0;
}

static int xfrm4_beet_input(struct xfrm_state *x, struct sk_buff *skb)
{
struct iphdr *iph;
int optlen = 0;
int err = -EINVAL;

if (unlikely(XFRM_MODE_SKB_CB(skb)->protocol == IPPROTO_BEETPH)) {
struct ip_beet_phdr *ph;
int phlen;

if (!pskb_may_pull(skb, sizeof(*ph)))
goto out;

ph = (struct ip_beet_phdr *)skb->data;

phlen = sizeof(*ph) + ph->padlen;
optlen = ph->hdrlen * 8 + (IPV4_BEET_PHMAXLEN - phlen);
if (optlen < 0 || optlen & 3 || optlen > 250)
goto out;

XFRM_MODE_SKB_CB(skb)->protocol = ph->nexthdr;

if (!pskb_may_pull(skb, phlen))
goto out;
__skb_pull(skb, phlen);
}

skb_push(skb, sizeof(*iph));
skb_reset_network_header(skb);
skb_mac_header_rebuild(skb);

xfrm4_beet_make_header(skb);

iph = ip_hdr(skb);

iph->ihl += optlen / 4;
iph->tot_len = htons(skb->len);
iph->daddr = x->sel.daddr.a4;
iph->saddr = x->sel.saddr.a4;
iph->check = 0;
iph->check = ip_fast_csum(skb_network_header(skb), iph->ihl);
err = 0;
out:
return err;
}

static struct xfrm_mode xfrm4_beet_mode = {
.input2 = xfrm4_beet_input,
.input = xfrm_prepare_input,
.output2 = xfrm4_beet_output,
.output = xfrm4_prepare_output,
.owner = THIS_MODULE,
.encap = XFRM_MODE_BEET,
.flags = XFRM_MODE_FLAG_TUNNEL,
};

static int __init xfrm4_beet_init(void)
{
return xfrm_register_mode(&xfrm4_beet_mode, AF_INET);
}

static void __exit xfrm4_beet_exit(void)
{
int err;

err = xfrm_unregister_mode(&xfrm4_beet_mode, AF_INET);
BUG_ON(err);
}

module_init(xfrm4_beet_init);
module_exit(xfrm4_beet_exit);
MODULE_LICENSE("GPL");
MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_BEET);
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