/*
 * Copyright (C)2004 USAGI/WIDE Project
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Author:
 *      Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
 */

#include <linux/types.h>
#include <linux/ipv6.h>
#include <linux/in6.h>
#include <linux/netfilter.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/icmp.h>
#include <linux/sysctl.h>
#include <net/ipv6.h>
#include <net/inet_frag.h>

#include <linux/netfilter_ipv6.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_l4proto.h>
#include <net/netfilter/nf_conntrack_l3proto.h>
#include <net/netfilter/nf_conntrack_core.h>

static bool ipv6_pkt_to_tuple(const struct sk_buff *skb, unsigned int nhoff,
                              struct nf_conntrack_tuple *tuple)
{
        const u_int32_t *ap;
        u_int32_t _addrs[8];

        ap = skb_header_pointer(skb, nhoff + offsetof(struct ipv6hdr, saddr),
                                sizeof(_addrs), _addrs);
        if (ap == NULL)
                return false;

        memcpy(tuple->src.u3.ip6, ap, sizeof(tuple->src.u3.ip6));
        memcpy(tuple->dst.u3.ip6, ap + 4, sizeof(tuple->dst.u3.ip6));

        return true;
}

static bool ipv6_invert_tuple(struct nf_conntrack_tuple *tuple,
                              const struct nf_conntrack_tuple *orig)
{
        memcpy(tuple->src.u3.ip6, orig->dst.u3.ip6, sizeof(tuple->src.u3.ip6));
        memcpy(tuple->dst.u3.ip6, orig->src.u3.ip6, sizeof(tuple->dst.u3.ip6));

        return true;
}

static int ipv6_print_tuple(struct seq_file *s,
                            const struct nf_conntrack_tuple *tuple)
{
        return seq_printf(s, "src=" NIP6_FMT " dst=" NIP6_FMT " ",
                          NIP6(*((struct in6_addr *)tuple->src.u3.ip6)),
                          NIP6(*((struct in6_addr *)tuple->dst.u3.ip6)));
}

/*
 * Based on ipv6_skip_exthdr() in net/ipv6/exthdr.c
 *
 * This function parses (probably truncated) exthdr set "hdr"
 * of length "len". "nexthdrp" initially points to some place,
 * where type of the first header can be found.
 *
 * It skips all well-known exthdrs, and returns pointer to the start
 * of unparsable area i.e. the first header with unknown type.
 * if success, *nexthdr is updated by type/protocol of this header.
 *
 * NOTES: - it may return pointer pointing beyond end of packet,
 *          if the last recognized header is truncated in the middle.
 *        - if packet is truncated, so that all parsed headers are skipped,
 *          it returns -1.
 *        - if packet is fragmented, return pointer of the fragment header.
 *        - ESP is unparsable for now and considered like
 *          normal payload protocol.
 *        - Note also special handling of AUTH header. Thanks to IPsec wizards.
 */

static int nf_ct_ipv6_skip_exthdr(const struct sk_buff *skb, int start,
                                  u8 *nexthdrp, int len)
{
        u8 nexthdr = *nexthdrp;

        while (ipv6_ext_hdr(nexthdr)) {
                struct ipv6_opt_hdr hdr;
                int hdrlen;

                if (len < (int)sizeof(struct ipv6_opt_hdr))
                        return -1;
                if (nexthdr == NEXTHDR_NONE)
                        break;
                if (nexthdr == NEXTHDR_FRAGMENT)
                        break;
                if (skb_copy_bits(skb, start, &hdr, sizeof(hdr)))
                        BUG();
                if (nexthdr == NEXTHDR_AUTH)
                        hdrlen = (hdr.hdrlen+2)<<2;
                else
                        hdrlen = ipv6_optlen(&hdr);

                nexthdr = hdr.nexthdr;
                len -= hdrlen;
                start += hdrlen;
        }

        *nexthdrp = nexthdr;
        return start;
}

static int ipv6_get_l4proto(const struct sk_buff *skb, unsigned int nhoff,
                            unsigned int *dataoff, u_int8_t *protonum)
{
        unsigned int extoff = nhoff + sizeof(struct ipv6hdr);
        unsigned char pnum;
        int protoff;

        if (skb_copy_bits(skb, nhoff + offsetof(struct ipv6hdr, nexthdr),
                          &pnum, sizeof(pnum)) != 0) {
                pr_debug("ip6_conntrack_core: can't get nexthdr\n");
                return -NF_ACCEPT;
        }
        protoff = nf_ct_ipv6_skip_exthdr(skb, extoff, &pnum, skb->len - extoff);
        /*
         * (protoff == skb->len) mean that the packet doesn't have no data
         * except of IPv6 & ext headers. but it's tracked anyway. - YK
         */
        if ((protoff < 0) || (protoff > skb->len)) {
                pr_debug("ip6_conntrack_core: can't find proto in pkt\n");
                return -NF_ACCEPT;
        }

        *dataoff = protoff;
        *protonum = pnum;
        return NF_ACCEPT;
}

static unsigned int ipv6_confirm(unsigned int hooknum,
                                 struct sk_buff *skb,
                                 const struct net_device *in,
                                 const struct net_device *out,
                                 int (*okfn)(struct sk_buff *))
{
        struct nf_conn *ct;
        const struct nf_conn_help *help;
        const struct nf_conntrack_helper *helper;
        enum ip_conntrack_info ctinfo;
        unsigned int ret, protoff;
        unsigned int extoff = (u8 *)(ipv6_hdr(skb) + 1) - skb->data;
        unsigned char pnum = ipv6_hdr(skb)->nexthdr;


        /* This is where we call the helper: as the packet goes out. */
        ct = nf_ct_get(skb, &ctinfo);
        if (!ct || ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY)
                goto out;

        help = nfct_help(ct);
        if (!help)
                goto out;
        /* rcu_read_lock()ed by nf_hook_slow */
        helper = rcu_dereference(help->helper);
        if (!helper)
                goto out;

        protoff = nf_ct_ipv6_skip_exthdr(skb, extoff, &pnum,
                                         skb->len - extoff);
        if (protoff > skb->len || pnum == NEXTHDR_FRAGMENT) {
                pr_debug("proto header not found\n");
                return NF_ACCEPT;
        }

        ret = helper->help(skb, protoff, ct, ctinfo);
        if (ret != NF_ACCEPT)
                return ret;
out:
        /* We've seen it coming out the other side: confirm it */
        return nf_conntrack_confirm(skb);
}

static enum ip6_defrag_users nf_ct6_defrag_user(unsigned int hooknum,
                                                struct sk_buff *skb)
{
        if (hooknum == NF_INET_PRE_ROUTING)
                return IP6_DEFRAG_CONNTRACK_IN;
        else
                return IP6_DEFRAG_CONNTRACK_OUT;

}

static unsigned int ipv6_defrag(unsigned int hooknum,
                                struct sk_buff *skb,
                                const struct net_device *in,
                                const struct net_device *out,
                                int (*okfn)(struct sk_buff *))
{
        struct sk_buff *reasm;

        /* Previously seen (loopback)?  */
        if (skb->nfct)
                return NF_ACCEPT;

        reasm = nf_ct_frag6_gather(skb, nf_ct6_defrag_user(hooknum, skb));
        /* queued */
        if (reasm == NULL)
                return NF_STOLEN;

        /* error occured or not fragmented */
        if (reasm == skb)
                return NF_ACCEPT;

        nf_ct_frag6_output(hooknum, reasm, (struct net_device *)in,
                           (struct net_device *)out, okfn);

        return NF_STOLEN;
}

static unsigned int ipv6_conntrack_in(unsigned int hooknum,
                                      struct sk_buff *skb,
                                      const struct net_device *in,
                                      const struct net_device *out,
                                      int (*okfn)(struct sk_buff *))
{
        struct sk_buff *reasm = skb->nfct_reasm;

        /* This packet is fragmented and has reassembled packet. */
        if (reasm) {
                /* Reassembled packet isn't parsed yet ? */
                if (!reasm->nfct) {
                        unsigned int ret;

                        ret = nf_conntrack_in(PF_INET6, hooknum, reasm);
                        if (ret != NF_ACCEPT)
                                return ret;
                }
                nf_conntrack_get(reasm->nfct);
                skb->nfct = reasm->nfct;
                skb->nfctinfo = reasm->nfctinfo;
                return NF_ACCEPT;
        }

        return nf_conntrack_in(PF_INET6, hooknum, skb);
}

static unsigned int ipv6_conntrack_local(unsigned int hooknum,
                                         struct sk_buff *skb,
                                         const struct net_device *in,
                                         const struct net_device *out,
                                         int (*okfn)(struct sk_buff *))
{
        /* root is playing with raw sockets. */
        if (skb->len < sizeof(struct ipv6hdr)) {
                if (net_ratelimit())
                        printk("ipv6_conntrack_local: packet too short\n");
                return NF_ACCEPT;
        }
        return ipv6_conntrack_in(hooknum, skb, in, out, okfn);
}

static struct nf_hook_ops ipv6_conntrack_ops[] __read_mostly = {
        {
                .hook           = ipv6_defrag,
                .owner          = THIS_MODULE,
                .pf             = PF_INET6,
                .hooknum        = NF_INET_PRE_ROUTING,
                .priority       = NF_IP6_PRI_CONNTRACK_DEFRAG,
        },
        {
                .hook           = ipv6_conntrack_in,
                .owner          = THIS_MODULE,
                .pf             = PF_INET6,
                .hooknum        = NF_INET_PRE_ROUTING,
                .priority       = NF_IP6_PRI_CONNTRACK,
        },
        {
                .hook           = ipv6_conntrack_local,
                .owner          = THIS_MODULE,
                .pf             = PF_INET6,
                .hooknum        = NF_INET_LOCAL_OUT,
                .priority       = NF_IP6_PRI_CONNTRACK,
        },
        {
                .hook           = ipv6_defrag,
                .owner          = THIS_MODULE,
                .pf             = PF_INET6,
                .hooknum        = NF_INET_LOCAL_OUT,
                .priority       = NF_IP6_PRI_CONNTRACK_DEFRAG,
        },
        {
                .hook           = ipv6_confirm,
                .owner          = THIS_MODULE,
                .pf             = PF_INET6,
                .hooknum        = NF_INET_POST_ROUTING,
                .priority       = NF_IP6_PRI_LAST,
        },
        {
                .hook           = ipv6_confirm,
                .owner          = THIS_MODULE,
                .pf             = PF_INET6,
                .hooknum        = NF_INET_LOCAL_IN,
                .priority       = NF_IP6_PRI_LAST-1,
        },
};

#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)

#include <linux/netfilter/nfnetlink.h>
#include <linux/netfilter/nfnetlink_conntrack.h>

static int ipv6_tuple_to_nlattr(struct sk_buff *skb,
                                const struct nf_conntrack_tuple *tuple)
{
        NLA_PUT(skb, CTA_IP_V6_SRC, sizeof(u_int32_t) * 4,
                &tuple->src.u3.ip6);
        NLA_PUT(skb, CTA_IP_V6_DST, sizeof(u_int32_t) * 4,
                &tuple->dst.u3.ip6);
        return 0;

nla_put_failure:
        return -1;
}

static const struct nla_policy ipv6_nla_policy[CTA_IP_MAX+1] = {
        [CTA_IP_V6_SRC] = { .len = sizeof(u_int32_t)*4 },
        [CTA_IP_V6_DST] = { .len = sizeof(u_int32_t)*4 },
};

static int ipv6_nlattr_to_tuple(struct nlattr *tb[],
                                struct nf_conntrack_tuple *t)
{
        if (!tb[CTA_IP_V6_SRC] || !tb[CTA_IP_V6_DST])
                return -EINVAL;

        memcpy(&t->src.u3.ip6, nla_data(tb[CTA_IP_V6_SRC]),
               sizeof(u_int32_t) * 4);
        memcpy(&t->dst.u3.ip6, nla_data(tb[CTA_IP_V6_DST]),
               sizeof(u_int32_t) * 4);

        return 0;
}
#endif

struct nf_conntrack_l3proto nf_conntrack_l3proto_ipv6 __read_mostly = {
        .l3proto                = PF_INET6,
        .name                   = "ipv6",
        .pkt_to_tuple           = ipv6_pkt_to_tuple,
        .invert_tuple           = ipv6_invert_tuple,
        .print_tuple            = ipv6_print_tuple,
        .get_l4proto            = ipv6_get_l4proto,
#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
        .tuple_to_nlattr        = ipv6_tuple_to_nlattr,
        .nlattr_to_tuple        = ipv6_nlattr_to_tuple,
        .nla_policy             = ipv6_nla_policy,
#endif
#ifdef CONFIG_SYSCTL
        .ctl_table_path         = nf_net_netfilter_sysctl_path,
        .ctl_table              = nf_ct_ipv6_sysctl_table,
#endif
        .me                     = THIS_MODULE,
};

MODULE_ALIAS("nf_conntrack-" __stringify(AF_INET6));
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Yasuyuki KOZAKAI @USAGI <yasuyuki.kozakai@toshiba.co.jp>");

static int __init nf_conntrack_l3proto_ipv6_init(void)
{
        int ret = 0;

        need_conntrack();

        ret = nf_ct_frag6_init();
        if (ret < 0) {
                printk("nf_conntrack_ipv6: can't initialize frag6.\n");
                return ret;
        }
        ret = nf_conntrack_l4proto_register(&nf_conntrack_l4proto_tcp6);
        if (ret < 0) {
                printk("nf_conntrack_ipv6: can't register tcp.\n");
                goto cleanup_frag6;
        }

        ret = nf_conntrack_l4proto_register(&nf_conntrack_l4proto_udp6);
        if (ret < 0) {
                printk("nf_conntrack_ipv6: can't register udp.\n");
                goto cleanup_tcp;
        }

        ret = nf_conntrack_l4proto_register(&nf_conntrack_l4proto_icmpv6);
        if (ret < 0) {
                printk("nf_conntrack_ipv6: can't register icmpv6.\n");
                goto cleanup_udp;
        }

        ret = nf_conntrack_l3proto_register(&nf_conntrack_l3proto_ipv6);
        if (ret < 0) {
                printk("nf_conntrack_ipv6: can't register ipv6\n");
                goto cleanup_icmpv6;
        }

        ret = nf_register_hooks(ipv6_conntrack_ops,
                                ARRAY_SIZE(ipv6_conntrack_ops));
        if (ret < 0) {
                printk("nf_conntrack_ipv6: can't register pre-routing defrag "
                       "hook.\n");
                goto cleanup_ipv6;
        }
        return ret;

 cleanup_ipv6:
        nf_conntrack_l3proto_unregister(&nf_conntrack_l3proto_ipv6);
 cleanup_icmpv6:
        nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_icmpv6);
 cleanup_udp:
        nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_udp6);
 cleanup_tcp:
        nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_tcp6);
 cleanup_frag6:
        nf_ct_frag6_cleanup();
        return ret;
}

static void __exit nf_conntrack_l3proto_ipv6_fini(void)
{
        synchronize_net();
        nf_unregister_hooks(ipv6_conntrack_ops, ARRAY_SIZE(ipv6_conntrack_ops));
        nf_conntrack_l3proto_unregister(&nf_conntrack_l3proto_ipv6);
        nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_icmpv6);
        nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_udp6);
        nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_tcp6);
        nf_ct_frag6_cleanup();
}

module_init(nf_conntrack_l3proto_ipv6_init);
module_exit(nf_conntrack_l3proto_ipv6_fini);