// SPDX-License-Identifier: GPL-2.0-or-later

  /*
   * xfrm6_output.c - Common IPsec encapsulation code for IPv6.
   * Copyright (C) 2002 USAGI/WIDE Project
   * Copyright (c) 2004 Herbert Xu <herbert@gondor.apana.org.au>

   */

  #include <linux/if_ether.h>

  #include <linux/kernel.h>
  #include <linux/module.h>

  #include <linux/skbuff.h>

  #include <linux/icmpv6.h>

  #include <linux/netfilter_ipv6.h>

  #include <net/dst.h>

  #include <net/ipv6.h>

  #include <net/ip6_route.h>

  #include <net/xfrm.h>

  int xfrm6_find_1stfragopt(struct xfrm_state *x, struct sk_buff *skb,
  			  u8 **prevhdr)
  {
  	return ip6_find_1stfragopt(skb, prevhdr);
  }

  EXPORT_SYMBOL(xfrm6_find_1stfragopt);

  void xfrm6_local_rxpmtu(struct sk_buff *skb, u32 mtu)

  {
  	struct flowi6 fl6;
  	struct sock *sk = skb->sk;
  
  	fl6.flowi6_oif = sk->sk_bound_dev_if;

  	fl6.daddr = ipv6_hdr(skb)->daddr;

  
  	ipv6_local_rxpmtu(sk, &fl6, mtu);
  }

  void xfrm6_local_error(struct sk_buff *skb, u32 mtu)

  {
  	struct flowi6 fl6;

  	const struct ipv6hdr *hdr;

  	struct sock *sk = skb->sk;

  	hdr = skb->encapsulation ? inner_ipv6_hdr(skb) : ipv6_hdr(skb);

  	fl6.fl6_dport = inet_sk(sk)->inet_dport;

  	fl6.daddr = hdr->daddr;

  
  	ipv6_local_error(sk, EMSGSIZE, &fl6, mtu);
  }

  static int __xfrm6_output_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
  {

  	return xfrm_output(sk, skb);

  }

  static int __xfrm6_output(struct net *net, struct sock *sk, struct sk_buff *skb)

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

  	int mtu;

  	bool toobig;

  #ifdef CONFIG_NETFILTER
  	if (!x) {
  		IP6CB(skb)->flags |= IP6SKB_REROUTED;

  		return dst_output(net, sk, skb);

  	}
  #endif

  	if (x->props.mode != XFRM_MODE_TUNNEL)
  		goto skip_frag;

  	if (skb->protocol == htons(ETH_P_IPV6))
  		mtu = ip6_skb_dst_mtu(skb);
  	else
  		mtu = dst_mtu(skb_dst(skb));

  	toobig = skb->len > mtu && !skb_is_gso(skb);

  	if (toobig && xfrm6_local_dontfrag(skb->sk)) {

  		xfrm6_local_rxpmtu(skb, mtu);

  		kfree_skb(skb);

  		return -EMSGSIZE;

  	} else if (!skb->ignore_df && toobig && skb->sk) {

  		xfrm_local_error(skb, mtu);

  		kfree_skb(skb);

  		return -EMSGSIZE;
  	}

  	if (toobig || dst_allfrag(skb_dst(skb)))

  		return ip6_fragment(net, sk, skb,
  				    __xfrm6_output_finish);

  
  skip_frag:

  	return xfrm_output(sk, skb);

  }

  int xfrm6_output(struct net *net, struct sock *sk, struct sk_buff *skb)

  {

  	return NF_HOOK_COND(NFPROTO_IPV6, NF_INET_POST_ROUTING,

  			    net, sk, skb,  skb->dev, skb_dst(skb)->dev,

  			    __xfrm6_output,

  			    !(IP6CB(skb)->flags & IP6SKB_REROUTED));

  }