xfrm6_mode_transport.c

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/*
 * xfrm6_mode_transport.c - Transport mode encapsulation for IPv6.
 *
 * Copyright (C) 2002 USAGI/WIDE Project
 * Copyright (c) 2004-2006 Herbert Xu <[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/ipv6.h>
#include <net/xfrm.h>

/* Add encapsulation header.
 *
 * The IP header and mutable extension headers will be moved forward to make
 * space for the encapsulation header.
 */
static int xfrm6_transport_output(struct xfrm_state *x, struct sk_buff *skb)
{
    struct ipv6hdr *iph;
    u8 *prevhdr;
    int hdr_len;

    iph = ipv6_hdr(skb);

    hdr_len = x->type->hdr_offset(x, skb, &prevhdr);
    skb_set_mac_header(skb, (prevhdr - x->props.header_len) - skb->data);
    skb_set_network_header(skb, -x->props.header_len);
    skb->transport_header = skb->network_header + hdr_len;
    __skb_pull(skb, hdr_len);
    memmove(ipv6_hdr(skb), iph, hdr_len);
    return 0;
}

/* Remove encapsulation header.
 *
 * The IP header will be moved over the top of the encapsulation header.
 *
 * On entry, skb->h shall point to where the IP header should be and skb->nh
 * shall be set to where the IP header currently is.  skb->data shall point
 * to the start of the payload.
 */
static int xfrm6_transport_input(struct xfrm_state *x, struct sk_buff *skb)
{
    int ihl = skb->data - skb_transport_header(skb);

    if (skb->transport_header != skb->network_header) {
        memmove(skb_transport_header(skb),
            skb_network_header(skb), ihl);
        skb->network_header = skb->transport_header;
    }
    ipv6_hdr(skb)->payload_len = htons(skb->len + ihl -
                       sizeof(struct ipv6hdr));
    skb_reset_transport_header(skb);
    return 0;
}

static struct xfrm_mode xfrm6_transport_mode = {
    .input = xfrm6_transport_input,
    .output = xfrm6_transport_output,
    .owner = THIS_MODULE,
    .encap = XFRM_MODE_TRANSPORT,
};

static int __init xfrm6_transport_init(void)
{
    return xfrm_register_mode(&xfrm6_transport_mode, AF_INET6);
}

static void __exit xfrm6_transport_exit(void)
{
    int err;

    err = xfrm_unregister_mode(&xfrm6_transport_mode, AF_INET6);
    BUG_ON(err);
}

module_init(xfrm6_transport_init);
module_exit(xfrm6_transport_exit);
MODULE_LICENSE("GPL");
MODULE_ALIAS_XFRM_MODE(AF_INET6, XFRM_MODE_TRANSPORT);