/*
 * IPv6 specific functions of netfilter core
 *
 * Rusty Russell (C) 2000 -- This code is GPL.
 * Patrick McHardy (C) 2006-2012
 */
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/ipv6.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv6.h>
#include <linux/export.h>
#include <net/addrconf.h>
#include <net/dst.h>
#include <net/ipv6.h>
#include <net/ip6_route.h>
#include <net/xfrm.h>
#include <net/netfilter/nf_queue.h>
#include <net/netfilter/nf_conntrack_bridge.h>
#include <net/netfilter/ipv6/nf_defrag_ipv6.h>
#include "../bridge/br_private.h"

int ip6_route_me_harder(struct net *net, struct sock *sk_partial, struct sk_buff *skb)
{
        const struct ipv6hdr *iph = ipv6_hdr(skb);
        struct sock *sk = sk_to_full_sk(sk_partial);
        struct flow_keys flkeys;
        unsigned int hh_len;
        struct dst_entry *dst;
        int strict = (ipv6_addr_type(&iph->daddr) &
                      (IPV6_ADDR_MULTICAST | IPV6_ADDR_LINKLOCAL));
        struct flowi6 fl6 = {
                .flowi6_oif = sk && sk->sk_bound_dev_if ? sk->sk_bound_dev_if :
                        strict ? skb_dst(skb)->dev->ifindex : 0,
                .flowi6_mark = skb->mark,
                .flowi6_uid = sock_net_uid(net, sk),
                .daddr = iph->daddr,
                .saddr = iph->saddr,
        };
        int err;

        fib6_rules_early_flow_dissect(net, skb, &fl6, &flkeys);
        dst = ip6_route_output(net, sk, &fl6);
        err = dst->error;
        if (err) {
                IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTNOROUTES);
                net_dbg_ratelimited("ip6_route_me_harder: No more route\n");
                dst_release(dst);
                return err;
        }

        /* Drop old route. */
        skb_dst_drop(skb);

        skb_dst_set(skb, dst);

#ifdef CONFIG_XFRM
        if (!(IP6CB(skb)->flags & IP6SKB_XFRM_TRANSFORMED) &&
            xfrm_decode_session(skb, flowi6_to_flowi(&fl6), AF_INET6) == 0) {
                skb_dst_set(skb, NULL);
                dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), sk, 0);
                if (IS_ERR(dst))
                        return PTR_ERR(dst);
                skb_dst_set(skb, dst);
        }
#endif

        /* Change in oif may mean change in hh_len. */
        hh_len = skb_dst(skb)->dev->hard_header_len;
        if (skb_headroom(skb) < hh_len &&
            pskb_expand_head(skb, HH_DATA_ALIGN(hh_len - skb_headroom(skb)),
                             0, GFP_ATOMIC))
                return -ENOMEM;

        return 0;
}
EXPORT_SYMBOL(ip6_route_me_harder);

static int nf_ip6_reroute(struct sk_buff *skb,
                          const struct nf_queue_entry *entry)
{
        struct ip6_rt_info *rt_info = nf_queue_entry_reroute(entry);

        if (entry->state.hook == NF_INET_LOCAL_OUT) {
                const struct ipv6hdr *iph = ipv6_hdr(skb);
                if (!ipv6_addr_equal(&iph->daddr, &rt_info->daddr) ||
                    !ipv6_addr_equal(&iph->saddr, &rt_info->saddr) ||
                    skb->mark != rt_info->mark)
                        return ip6_route_me_harder(entry->state.net, entry->state.sk, skb);
        }
        return 0;
}

int __nf_ip6_route(struct net *net, struct dst_entry **dst,
                   struct flowi *fl, bool strict)
{
        static const struct ipv6_pinfo fake_pinfo;
        static const struct inet_sock fake_sk = {
                /* makes ip6_route_output set RT6_LOOKUP_F_IFACE: */
                .sk.sk_bound_dev_if = 1,
                .pinet6 = (struct ipv6_pinfo *) &fake_pinfo,
        };
        const void *sk = strict ? &fake_sk : NULL;
        struct dst_entry *result;
        int err;

        result = ip6_route_output(net, sk, &fl->u.ip6);
        err = result->error;
        if (err)
                dst_release(result);
        else
                *dst = result;
        return err;
}
EXPORT_SYMBOL_GPL(__nf_ip6_route);

int br_ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
                    struct nf_bridge_frag_data *data,
                    int (*output)(struct net *, struct sock *sk,
                                  const struct nf_bridge_frag_data *data,
                                  struct sk_buff *))
{
        int frag_max_size = BR_INPUT_SKB_CB(skb)->frag_max_size;
        ktime_t tstamp = skb->tstamp;
        struct ip6_frag_state state;
        u8 *prevhdr, nexthdr = 0;
        unsigned int mtu, hlen;
        int hroom, err = 0;
        __be32 frag_id;

        err = ip6_find_1stfragopt(skb, &prevhdr);
        if (err < 0)
                goto blackhole;
        hlen = err;
        nexthdr = *prevhdr;

        mtu = skb->dev->mtu;
        if (frag_max_size > mtu ||
            frag_max_size < IPV6_MIN_MTU)
                goto blackhole;

        mtu = frag_max_size;
        if (mtu < hlen + sizeof(struct frag_hdr) + 8)
                goto blackhole;
        mtu -= hlen + sizeof(struct frag_hdr);

        frag_id = ipv6_select_ident(net, &ipv6_hdr(skb)->daddr,
                                    &ipv6_hdr(skb)->saddr);

        if (skb->ip_summed == CHECKSUM_PARTIAL &&
            (err = skb_checksum_help(skb)))
                goto blackhole;

        hroom = LL_RESERVED_SPACE(skb->dev);
        if (skb_has_frag_list(skb)) {
                unsigned int first_len = skb_pagelen(skb);
                struct ip6_fraglist_iter iter;
                struct sk_buff *frag2;

                if (first_len - hlen > mtu ||
                    skb_headroom(skb) < (hroom + sizeof(struct frag_hdr)))
                        goto blackhole;

                if (skb_cloned(skb))
                        goto slow_path;

                skb_walk_frags(skb, frag2) {
                        if (frag2->len > mtu ||
                            skb_headroom(frag2) < (hlen + hroom + sizeof(struct frag_hdr)))
                                goto blackhole;

                        /* Partially cloned skb? */
                        if (skb_shared(frag2))
                                goto slow_path;
                }

                err = ip6_fraglist_init(skb, hlen, prevhdr, nexthdr, frag_id,
                                        &iter);
                if (err < 0)
                        goto blackhole;

                for (;;) {
                        /* Prepare header of the next frame,
                         * before previous one went down.
                         */
                        if (iter.frag)
                                ip6_fraglist_prepare(skb, &iter);

                        skb->tstamp = tstamp;
                        err = output(net, sk, data, skb);
                        if (err || !iter.frag)
                                break;

                        skb = ip6_fraglist_next(&iter);
                }

                kfree(iter.tmp_hdr);
                if (!err)
                        return 0;

                kfree_skb_list(iter.frag);
                return err;
        }
slow_path:
        /* This is a linearized skbuff, the original geometry is lost for us.
         * This may also be a clone skbuff, we could preserve the geometry for
         * the copies but probably not worth the effort.
         */
        ip6_frag_init(skb, hlen, mtu, skb->dev->needed_tailroom,
                      LL_RESERVED_SPACE(skb->dev), prevhdr, nexthdr, frag_id,
                      &state);

        while (state.left > 0) {
                struct sk_buff *skb2;

                skb2 = ip6_frag_next(skb, &state);
                if (IS_ERR(skb2)) {
                        err = PTR_ERR(skb2);
                        goto blackhole;
                }

                skb2->tstamp = tstamp;
                err = output(net, sk, data, skb2);
                if (err)
                        goto blackhole;
        }
        consume_skb(skb);
        return err;

blackhole:
        kfree_skb(skb);
        return 0;
}
EXPORT_SYMBOL_GPL(br_ip6_fragment);

static const struct nf_ipv6_ops ipv6ops = {
#if IS_MODULE(CONFIG_IPV6)
        .chk_addr               = ipv6_chk_addr,
        .route_me_harder        = ip6_route_me_harder,
        .dev_get_saddr          = ipv6_dev_get_saddr,
        .route                  = __nf_ip6_route,
#if IS_ENABLED(CONFIG_SYN_COOKIES)
        .cookie_init_sequence   = __cookie_v6_init_sequence,
        .cookie_v6_check        = __cookie_v6_check,
#endif
#endif
        .route_input            = ip6_route_input,
        .fragment               = ip6_fragment,
        .reroute                = nf_ip6_reroute,
#if IS_MODULE(CONFIG_IPV6)
        .br_fragment            = br_ip6_fragment,
#endif
};

int __init ipv6_netfilter_init(void)
{
        RCU_INIT_POINTER(nf_ipv6_ops, &ipv6ops);
        return 0;
}

/* This can be called from inet6_init() on errors, so it cannot
 * be marked __exit. -DaveM
 */
void ipv6_netfilter_fini(void)
{
        RCU_INIT_POINTER(nf_ipv6_ops, NULL);
}