/*
 * 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>
 *
 * 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/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);

static int xfrm6_local_dontfrag(struct sk_buff *skb)
{
        int proto;
        struct sock *sk = skb->sk;

        if (sk) {
                if (sk->sk_family != AF_INET6)
                        return 0;

                proto = sk->sk_protocol;
                if (proto == IPPROTO_UDP || proto == IPPROTO_RAW)
                        return inet6_sk(sk)->dontfrag;
        }

        return 0;
}

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

        if (skb->ignore_df)
                goto out;

        mtu = dst_mtu(dst);
        if (mtu < IPV6_MIN_MTU)
                mtu = IPV6_MIN_MTU;

        if ((!skb_is_gso(skb) && skb->len > mtu) ||
            (skb_is_gso(skb) &&
             !skb_gso_validate_network_len(skb, ip6_skb_dst_mtu(skb)))) {
                skb->dev = dst->dev;
                skb->protocol = htons(ETH_P_IPV6);

                if (xfrm6_local_dontfrag(skb))
                        xfrm6_local_rxpmtu(skb, mtu);
                else if (skb->sk)
                        xfrm_local_error(skb, mtu);
                else
                        icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
                ret = -EMSGSIZE;
        }
out:
        return ret;
}

int xfrm6_extract_output(struct xfrm_state *x, struct sk_buff *skb)
{
        int err;

        err = xfrm6_tunnel_check_size(skb);
        if (err)
                return err;

        XFRM_MODE_SKB_CB(skb)->protocol = ipv6_hdr(skb)->nexthdr;

        return xfrm6_extract_header(skb);
}

int xfrm6_prepare_output(struct xfrm_state *x, struct sk_buff *skb)
{
        int err;

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

        skb->ignore_df = 1;
        skb->protocol = htons(ETH_P_IPV6);

        return x->outer_mode->output2(x, skb);
}
EXPORT_SYMBOL(xfrm6_prepare_output);

int xfrm6_output_finish(struct sock *sk, struct sk_buff *skb)
{
        memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));

#ifdef CONFIG_NETFILTER
        IP6CB(skb)->flags |= IP6SKB_XFRM_TRANSFORMED;
#endif

        return xfrm_output(sk, skb);
}

static int __xfrm6_output_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
{
        struct xfrm_state *x = skb_dst(skb)->xfrm;

        return x->outer_mode->afinfo->output_finish(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)) {
                xfrm6_local_rxpmtu(skb, mtu);
                return -EMSGSIZE;
        } else if (!skb->ignore_df && toobig && skb->sk) {
                xfrm_local_error(skb, mtu);
                return -EMSGSIZE;
        }

        if (toobig || dst_allfrag(skb_dst(skb)))
                return ip6_fragment(net, sk, skb,
                                    __xfrm6_output_finish);

skip_frag:
        return x->outer_mode->afinfo->output_finish(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,  NULL, skb_dst(skb)->dev,
                            __xfrm6_output,
                            !(IP6CB(skb)->flags & IP6SKB_REROUTED));
}