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/*
* xfrm4_output.c - Common IPsec encapsulation code for IPv4.
* Copyright (c) 2004 Herbert Xu <herbert@gondor.apana.org.au>
*
* 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/compiler.h>
#include <linux/skbuff.h>
#include <linux/spinlock.h>
#include <linux/netfilter_ipv4.h>
#include <net/inet_ecn.h>
#include <net/ip.h>
#include <net/xfrm.h>
#include <net/icmp.h>
/* Add encapsulation header.
*
* In transport mode, the IP header will be moved forward to make space
* for the encapsulation header.
*
* In tunnel mode, the top IP header will be constructed per RFC 2401.
* The following fields in it shall be filled in by x->type->output:
* tot_len
* check
*
* On exit, skb->h will be set to the start of the payload to be processed
* by x->type->output and skb->nh will be set to the top IP header.
*/
static void xfrm4_encap(struct sk_buff *skb)
{
struct dst_entry *dst = skb->dst;
struct xfrm_state *x = dst->xfrm;
struct iphdr *iph, *top_iph;
int flags;
iph = skb->nh.iph;
skb->h.ipiph = iph;
skb->nh.raw = skb_push(skb, x->props.header_len);
top_iph = skb->nh.iph;
if (!x->props.mode) {
skb->h.raw += iph->ihl*4;
memmove(top_iph, iph, iph->ihl*4);
return;
}
top_iph->ihl = 5;
top_iph->version = 4;
/* DS disclosed */
top_iph->tos = INET_ECN_encapsulate(iph->tos, iph->tos);
flags = x->props.flags;
if (flags & XFRM_STATE_NOECN)
IP_ECN_clear(top_iph);
top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ?
0 : (iph->frag_off & htons(IP_DF));
if (!top_iph->frag_off)
__ip_select_ident(top_iph, dst, 0);
top_iph->ttl = dst_metric(dst->child, RTAX_HOPLIMIT);
top_iph->saddr = x->props.saddr.a4;
top_iph->daddr = x->id.daddr.a4;
top_iph->protocol = IPPROTO_IPIP;
memset(&(IPCB(skb)->opt), 0, sizeof(struct ip_options));
}
static int xfrm4_tunnel_check_size(struct sk_buff *skb)
{
int mtu, ret = 0;
struct dst_entry *dst;
struct iphdr *iph = skb->nh.iph;
if (IPCB(skb)->flags & IPSKB_XFRM_TUNNEL_SIZE)
goto out;
IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE;
if (!(iph->frag_off & htons(IP_DF)) || skb->local_df)
goto out;
dst = skb->dst;
mtu = dst_mtu(dst);
if (skb->len > mtu) {
icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu));
ret = -EMSGSIZE;
}
out:
return ret;
}
static int xfrm4_output_one(struct sk_buff *skb)
{
struct dst_entry *dst = skb->dst;
struct xfrm_state *x = dst->xfrm;
int err;
if (skb->ip_summed == CHECKSUM_HW) {
err = skb_checksum_help(skb, 0);
if (err)
goto error_nolock;
}
if (x->props.mode) {
err = xfrm4_tunnel_check_size(skb);
if (err)
goto error_nolock;
}
do {
spin_lock_bh(&x->lock);
err = xfrm_state_check(x, skb);
if (err)
goto error;
xfrm4_encap(skb);
err = x->type->output(x, skb);
if (err)
goto error;
x->curlft.bytes += skb->len;
x->curlft.packets++;
spin_unlock_bh(&x->lock);
if (!(skb->dst = dst_pop(dst))) {
err = -EHOSTUNREACH;
goto error_nolock;
}
dst = skb->dst;
x = dst->xfrm;
} while (x && !x->props.mode);
IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED;
err = 0;
out_exit:
return err;
error:
spin_unlock_bh(&x->lock);
error_nolock:
kfree_skb(skb);
goto out_exit;
}
int xfrm4_output_finish(struct sk_buff *skb)
{
int err;
while (likely((err = xfrm4_output_one(skb)) == 0)) {
nf_reset(skb);
err = nf_hook(PF_INET, NF_IP_LOCAL_OUT, &skb, NULL,
skb->dst->dev, dst_output);
if (unlikely(err != 1))
break;
if (!skb->dst->xfrm)
return dst_output(skb);
err = nf_hook(PF_INET, NF_IP_POST_ROUTING, &skb, NULL,
skb->dst->dev, xfrm4_output_finish);
if (unlikely(err != 1))
break;
}
return err;
}
int xfrm4_output(struct sk_buff *skb)
{
return NF_HOOK(PF_INET, NF_IP_POST_ROUTING, skb, NULL, skb->dst->dev,
xfrm4_output_finish);
}
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