/*
   * xfrm_output.c - Common IPsec encapsulation code.
   *
   * Copyright (c) 2007 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/errno.h>
  #include <linux/module.h>
  #include <linux/netdevice.h>
  #include <linux/netfilter.h>
  #include <linux/skbuff.h>
  #include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <net/dst.h>
  #include <net/xfrm.h>
  
  static int xfrm_output2(struct sk_buff *skb);
  
  static int xfrm_skb_check_space(struct sk_buff *skb)
  {
  	struct dst_entry *dst = skb_dst(skb);
  	int nhead = dst->header_len + LL_RESERVED_SPACE(dst->dev)
  		- skb_headroom(skb);
  	int ntail = dst->dev->needed_tailroom - skb_tailroom(skb);
  
  	if (nhead <= 0) {
  		if (ntail <= 0)
  			return 0;
  		nhead = 0;
  	} else if (ntail < 0)
  		ntail = 0;
  
  	return pskb_expand_head(skb, nhead, ntail, GFP_ATOMIC);
  }
  
  static int xfrm_output_one(struct sk_buff *skb, int err)
  {
  	struct dst_entry *dst = skb_dst(skb);
  	struct xfrm_state *x = dst->xfrm;
  	struct net *net = xs_net(x);
  
  	if (err <= 0)
  		goto resume;
  
  	do {
  		err = xfrm_skb_check_space(skb);
  		if (err) {
  			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR);
  			goto error_nolock;
  		}
  
  		err = x->outer_mode->output(x, skb);
  		if (err) {
  			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATEMODEERROR);
  			goto error_nolock;
  		}
  
  		spin_lock_bh(&x->lock);
  
  		if (unlikely(x->km.state != XFRM_STATE_VALID)) {
  			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATEINVALID);
  			err = -EINVAL;
  			goto error;
  		}
  
  		err = xfrm_state_check_expire(x);
  		if (err) {
  			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATEEXPIRED);
  			goto error;
  		}
  
  		err = x->repl->overflow(x, skb);
  		if (err) {
  			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATESEQERROR);
  			goto error;
  		}
  
  		x->curlft.bytes += skb->len;
  		x->curlft.packets++;
  
  		spin_unlock_bh(&x->lock);
  
  		skb_dst_force(skb);
  
  		err = x->type->output(x, skb);
  		if (err == -EINPROGRESS)
  			goto out;
  
  resume:
  		if (err) {
  			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATEPROTOERROR);
  			goto error_nolock;
  		}
  
  		dst = skb_dst_pop(skb);
  		if (!dst) {
  			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR);
  			err = -EHOSTUNREACH;
  			goto error_nolock;
  		}
  		skb_dst_set(skb, dst);
  		x = dst->xfrm;
  	} while (x && !(x->outer_mode->flags & XFRM_MODE_FLAG_TUNNEL));
  
  	return 0;
  
  error:
  	spin_unlock_bh(&x->lock);
  error_nolock:
  	kfree_skb(skb);
  out:
  	return err;
  }
  
  int xfrm_output_resume(struct sk_buff *skb, int err)
  {
  	while (likely((err = xfrm_output_one(skb, err)) == 0)) {
  		nf_reset(skb);
  
  		err = skb_dst(skb)->ops->local_out(skb);
  		if (unlikely(err != 1))
  			goto out;
  
  		if (!skb_dst(skb)->xfrm)
  			return dst_output(skb);
  
  		err = nf_hook(skb_dst(skb)->ops->family,
  			      NF_INET_POST_ROUTING, skb,
  			      NULL, skb_dst(skb)->dev, xfrm_output2);
  		if (unlikely(err != 1))
  			goto out;
  	}
  
  	if (err == -EINPROGRESS)
  		err = 0;
  
  out:
  	return err;
  }
  EXPORT_SYMBOL_GPL(xfrm_output_resume);
  
  static int xfrm_output2(struct sk_buff *skb)
  {
  	return xfrm_output_resume(skb, 1);
  }
  
  static int xfrm_output_gso(struct sk_buff *skb)
  {
  	struct sk_buff *segs;
  
  	segs = skb_gso_segment(skb, 0);
  	kfree_skb(skb);
  	if (IS_ERR(segs))
  		return PTR_ERR(segs);
  
  	do {
  		struct sk_buff *nskb = segs->next;
  		int err;
  
  		segs->next = NULL;
  		err = xfrm_output2(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 xfrm_output(struct sk_buff *skb)
  {
  	struct net *net = dev_net(skb_dst(skb)->dev);
  	int err;
  
  	if (skb_is_gso(skb))
  		return xfrm_output_gso(skb);
  
  	if (skb->ip_summed == CHECKSUM_PARTIAL) {
  		err = skb_checksum_help(skb);
  		if (err) {
  			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR);
  			kfree_skb(skb);
  			return err;
  		}
  	}
  
  	return xfrm_output2(skb);
  }
  
  int xfrm_inner_extract_output(struct xfrm_state *x, struct sk_buff *skb)
  {
  	struct xfrm_mode *inner_mode;
  	if (x->sel.family == AF_UNSPEC)
  		inner_mode = xfrm_ip2inner_mode(x,
  				xfrm_af2proto(skb_dst(skb)->ops->family));
  	else
  		inner_mode = x->inner_mode;
  
  	if (inner_mode == NULL)
  		return -EAFNOSUPPORT;
  	return inner_mode->afinfo->extract_output(x, skb);
  }
  
  void xfrm_local_error(struct sk_buff *skb, int mtu)
  {
  	unsigned int proto;
  	struct xfrm_state_afinfo *afinfo;
  
  	if (skb->protocol == htons(ETH_P_IP))
  		proto = AF_INET;
  	else if (skb->protocol == htons(ETH_P_IPV6))
  		proto = AF_INET6;
  	else
  		return;
  
  	afinfo = xfrm_state_get_afinfo(proto);
  	if (!afinfo)
  		return;
  
  	afinfo->local_error(skb, mtu);
  	xfrm_state_put_afinfo(afinfo);
  }
  
  EXPORT_SYMBOL_GPL(xfrm_output);
  EXPORT_SYMBOL_GPL(xfrm_inner_extract_output);
  EXPORT_SYMBOL_GPL(xfrm_local_error);