xfrm4_output.c

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/*
 * xfrm4_output.c - Common IPsec encapsulation code for IPv4.
 * Copyright (c) 2004 Herbert Xu <[email protected]>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/if_ether.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/netfilter_ipv4.h>
#include <net/dst.h>
#include <net/ip.h>
#include <net/xfrm.h>
#include <net/icmp.h>

static int xfrm4_tunnel_check_size(struct sk_buff *skb)
{
    int mtu, ret = 0;
    struct dst_entry *dst;

    if (IPCB(skb)->flags & IPSKB_XFRM_TUNNEL_SIZE)
        goto out;

    if (!(ip_hdr(skb)->frag_off & htons(IP_DF)) || skb->local_df)
        goto out;

    dst = skb_dst(skb);
    mtu = dst_mtu(dst);
    if (skb->len > mtu) {
        if (skb->sk)
            ip_local_error(skb->sk, EMSGSIZE, ip_hdr(skb)->daddr,
                       inet_sk(skb->sk)->inet_dport, mtu);
        else
            icmp_send(skb, ICMP_DEST_UNREACH,
                  ICMP_FRAG_NEEDED, htonl(mtu));
        ret = -EMSGSIZE;
    }
out:
    return ret;
}

int xfrm4_extract_output(struct xfrm_state *x, struct sk_buff *skb)
{
    int err;

    err = xfrm4_tunnel_check_size(skb);
    if (err)
        return err;

    XFRM_MODE_SKB_CB(skb)->protocol = ip_hdr(skb)->protocol;

    return xfrm4_extract_header(skb);
}

int xfrm4_prepare_output(struct xfrm_state *x, struct sk_buff *skb)
{
    int err;

    err = xfrm_inner_extract_output(x, skb);
    if (err)
        return err;

    memset(IPCB(skb), 0, sizeof(*IPCB(skb)));
    IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED;

    skb->protocol = htons(ETH_P_IP);

    return x->outer_mode->output2(x, skb);
}
EXPORT_SYMBOL(xfrm4_prepare_output);

int xfrm4_output_finish(struct sk_buff *skb)
{
#ifdef CONFIG_NETFILTER
    if (!skb_dst(skb)->xfrm) {
        IPCB(skb)->flags |= IPSKB_REROUTED;
        return dst_output(skb);
    }

    IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED;
#endif

    skb->protocol = htons(ETH_P_IP);
    return xfrm_output(skb);
}

int xfrm4_output(struct sk_buff *skb)
{
    struct dst_entry *dst = skb_dst(skb);
    struct xfrm_state *x = dst->xfrm;

    return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING, skb,
                NULL, dst->dev,
                x->outer_mode->afinfo->output_finish,
                !(IPCB(skb)->flags & IPSKB_REROUTED));
}