xfrm6_mode_tunnel.c

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/*
 * xfrm6_mode_tunnel.c - Tunnel mode encapsulation for IPv6.
 *
 * Copyright (C) 2002 USAGI/WIDE Project
 * Copyright (c) 2004-2006 Herbert Xu <[email protected]>
 */

#include <linux/gfp.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/stringify.h>
#include <net/dsfield.h>
#include <net/dst.h>
#include <net/inet_ecn.h>
#include <net/ip6_route.h>
#include <net/ipv6.h>
#include <net/xfrm.h>

static inline void ipip6_ecn_decapsulate(struct sk_buff *skb)
{
    const struct ipv6hdr *outer_iph = ipv6_hdr(skb);
    struct ipv6hdr *inner_iph = ipipv6_hdr(skb);

    if (INET_ECN_is_ce(ipv6_get_dsfield(outer_iph)))
        IP6_ECN_set_ce(inner_iph);
}

/* Add encapsulation header.
 *
 * The top IP header will be constructed per RFC 2401.
 */
static int xfrm6_mode_tunnel_output(struct xfrm_state *x, struct sk_buff *skb)
{
    struct dst_entry *dst = skb_dst(skb);
    struct ipv6hdr *top_iph;
    int dsfield;

    skb_set_network_header(skb, -x->props.header_len);
    skb->mac_header = skb->network_header +
              offsetof(struct ipv6hdr, nexthdr);
    skb->transport_header = skb->network_header + sizeof(*top_iph);
    top_iph = ipv6_hdr(skb);

    top_iph->version = 6;

    memcpy(top_iph->flow_lbl, XFRM_MODE_SKB_CB(skb)->flow_lbl,
           sizeof(top_iph->flow_lbl));
    top_iph->nexthdr = xfrm_af2proto(skb_dst(skb)->ops->family);

    dsfield = XFRM_MODE_SKB_CB(skb)->tos;
    dsfield = INET_ECN_encapsulate(dsfield, dsfield);
    if (x->props.flags & XFRM_STATE_NOECN)
        dsfield &= ~INET_ECN_MASK;
    ipv6_change_dsfield(top_iph, 0, dsfield);
    top_iph->hop_limit = ip6_dst_hoplimit(dst->child);
    top_iph->saddr = *(struct in6_addr *)&x->props.saddr;
    top_iph->daddr = *(struct in6_addr *)&x->id.daddr;
    return 0;
}

static int xfrm6_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
{
    int err = -EINVAL;

    if (XFRM_MODE_SKB_CB(skb)->protocol != IPPROTO_IPV6)
        goto out;
    if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
        goto out;

    if (skb_cloned(skb) &&
        (err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
        goto out;

    if (x->props.flags & XFRM_STATE_DECAP_DSCP)
        ipv6_copy_dscp(ipv6_get_dsfield(ipv6_hdr(skb)),
                   ipipv6_hdr(skb));
    if (!(x->props.flags & XFRM_STATE_NOECN))
        ipip6_ecn_decapsulate(skb);

    skb_reset_network_header(skb);
    skb_mac_header_rebuild(skb);

    err = 0;

out:
    return err;
}

static struct xfrm_mode xfrm6_tunnel_mode = {
    .input2 = xfrm6_mode_tunnel_input,
    .input = xfrm_prepare_input,
    .output2 = xfrm6_mode_tunnel_output,
    .output = xfrm6_prepare_output,
    .owner = THIS_MODULE,
    .encap = XFRM_MODE_TUNNEL,
    .flags = XFRM_MODE_FLAG_TUNNEL,
};

static int __init xfrm6_mode_tunnel_init(void)
{
    return xfrm_register_mode(&xfrm6_tunnel_mode, AF_INET6);
}

static void __exit xfrm6_mode_tunnel_exit(void)
{
    int err;

    err = xfrm_unregister_mode(&xfrm6_tunnel_mode, AF_INET6);
    BUG_ON(err);
}

module_init(xfrm6_mode_tunnel_init);
module_exit(xfrm6_mode_tunnel_exit);
MODULE_LICENSE("GPL");
MODULE_ALIAS_XFRM_MODE(AF_INET6, XFRM_MODE_TUNNEL);