/*
   * 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/if_ether.h>
  #include <linux/kernel.h>

  #include <linux/skbuff.h>
  #include <linux/spinlock.h>

  #include <linux/netfilter_ipv4.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;
  
  	IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE;

  	if (!(ip_hdr(skb)->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_PARTIAL) {
  		err = skb_checksum_help(skb);

  		if (err)
  			goto error_nolock;
  	}

  	if (x->props.mode == XFRM_MODE_TUNNEL) {

  		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;

  		err = x->mode->output(x, skb);

  		if (err)
  			goto error;

  		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 != XFRM_MODE_TUNNEL));

  	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;
  }

  static int xfrm4_output_finish2(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_finish2);

  		if (unlikely(err != 1))
  			break;
  	}
  
  	return err;
  }

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

  	if (!skb_is_gso(skb))

  		return xfrm4_output_finish2(skb);
  
  	skb->protocol = htons(ETH_P_IP);
  	segs = skb_gso_segment(skb, 0);
  	kfree_skb(skb);
  	if (unlikely(IS_ERR(segs)))
  		return PTR_ERR(segs);
  
  	do {
  		struct sk_buff *nskb = segs->next;
  		int err;
  
  		segs->next = NULL;
  		err = xfrm4_output_finish2(segs);
  
  		if (unlikely(err)) {
  			while ((segs = nskb)) {
  				nskb = segs->next;
  				segs->next = NULL;
  				kfree_skb(segs);
  			}
  			return err;
  		}
  
  		segs = nskb;
  	} while (segs);
  
  	return 0;
  }

  int xfrm4_output(struct sk_buff *skb)
  {

  	return NF_HOOK_COND(PF_INET, NF_IP_POST_ROUTING, skb, NULL, skb->dst->dev,
  			    xfrm4_output_finish,
  			    !(IPCB(skb)->flags & IPSKB_REROUTED));

  }