xfrm4_mode_beet.c

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/*
 * xfrm4_mode_beet.c - BEET mode encapsulation for IPv4.
 *
 * Copyright (c) 2006 Diego Beltrami <[email protected]>
 *                    Miika Komu     <[email protected]>
 *                    Herbert Xu     <[email protected]>
 *                    Abhinav Pathak <[email protected]>
 *                    Jeff Ahrenholz <[email protected]>
 */

#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);