/*
 * 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/ip6_checksum.h>
#include <net/netfilter/nf_queue.h>

int ip6_route_me_harder(struct net *net, struct sk_buff *skb)
{
        const struct ipv6hdr *iph = ipv6_hdr(skb);
        unsigned int hh_len;
        struct dst_entry *dst;
        struct flowi6 fl6 = {
                .flowi6_oif = skb->sk ? skb->sk->sk_bound_dev_if : 0,
                .flowi6_mark = skb->mark,
                .daddr = iph->daddr,
                .saddr = iph->saddr,
        };
        int err;

        dst = ip6_route_output(net, skb->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), skb->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);

/*
 * Extra routing may needed on local out, as the QUEUE target never
 * returns control to the table.
 */

struct ip6_rt_info {
        struct in6_addr daddr;
        struct in6_addr saddr;
        u_int32_t mark;
};

static void nf_ip6_saveroute(const struct sk_buff *skb,
                             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);

                rt_info->daddr = iph->daddr;
                rt_info->saddr = iph->saddr;
                rt_info->mark = skb->mark;
        }
}

static int nf_ip6_reroute(struct net *net, 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(net, skb);
        }
        return 0;
}

static 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;
}

__sum16 nf_ip6_checksum(struct sk_buff *skb, unsigned int hook,
                             unsigned int dataoff, u_int8_t protocol)
{
        const struct ipv6hdr *ip6h = ipv6_hdr(skb);
        __sum16 csum = 0;

        switch (skb->ip_summed) {
        case CHECKSUM_COMPLETE:
                if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN)
                        break;
                if (!csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
                                     skb->len - dataoff, protocol,
                                     csum_sub(skb->csum,
                                              skb_checksum(skb, 0,
                                                           dataoff, 0)))) {
                        skb->ip_summed = CHECKSUM_UNNECESSARY;
                        break;
                }
                /* fall through */
        case CHECKSUM_NONE:
                skb->csum = ~csum_unfold(
                                csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
                                             skb->len - dataoff,
                                             protocol,
                                             csum_sub(0,
                                                      skb_checksum(skb, 0,
                                                                   dataoff, 0))));
                csum = __skb_checksum_complete(skb);
        }
        return csum;
}
EXPORT_SYMBOL(nf_ip6_checksum);

static __sum16 nf_ip6_checksum_partial(struct sk_buff *skb, unsigned int hook,
                                       unsigned int dataoff, unsigned int len,
                                       u_int8_t protocol)
{
        const struct ipv6hdr *ip6h = ipv6_hdr(skb);
        __wsum hsum;
        __sum16 csum = 0;

        switch (skb->ip_summed) {
        case CHECKSUM_COMPLETE:
                if (len == skb->len - dataoff)
                        return nf_ip6_checksum(skb, hook, dataoff, protocol);
                /* fall through */
        case CHECKSUM_NONE:
                hsum = skb_checksum(skb, 0, dataoff, 0);
                skb->csum = ~csum_unfold(csum_ipv6_magic(&ip6h->saddr,
                                                         &ip6h->daddr,
                                                         skb->len - dataoff,
                                                         protocol,
                                                         csum_sub(0, hsum)));
                skb->ip_summed = CHECKSUM_NONE;
                return __skb_checksum_complete_head(skb, dataoff + len);
        }
        return csum;
};

static const struct nf_ipv6_ops ipv6ops = {
        .chk_addr       = ipv6_chk_addr,
        .route_input    = ip6_route_input,
        .fragment       = ip6_fragment
};

static const struct nf_afinfo nf_ip6_afinfo = {
        .family                 = AF_INET6,
        .checksum               = nf_ip6_checksum,
        .checksum_partial       = nf_ip6_checksum_partial,
        .route                  = nf_ip6_route,
        .saveroute              = nf_ip6_saveroute,
        .reroute                = nf_ip6_reroute,
        .route_key_size         = sizeof(struct ip6_rt_info),
};

int __init ipv6_netfilter_init(void)
{
        RCU_INIT_POINTER(nf_ipv6_ops, &ipv6ops);
        return nf_register_afinfo(&nf_ip6_afinfo);
}

/* 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);
        nf_unregister_afinfo(&nf_ip6_afinfo);
}