/*
 * xfrm6_policy.c: based on xfrm4_policy.c
 *
 * Authors:
 *      Mitsuru KANDA @USAGI
 *      Kazunori MIYAZAWA @USAGI
 *      Kunihiro Ishiguro <kunihiro@ipinfusion.com>
 *              IPv6 support
 *      YOSHIFUJI Hideaki
 *              Split up af-specific portion
 *
 */

#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <net/addrconf.h>
#include <net/dst.h>
#include <net/xfrm.h>
#include <net/ip.h>
#include <net/ipv6.h>
#include <net/ip6_route.h>
#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
#include <net/mip6.h>
#endif

static struct dst_ops xfrm6_dst_ops;
static struct xfrm_policy_afinfo xfrm6_policy_afinfo;

static struct dst_entry *xfrm6_dst_lookup(struct net *net, int tos,
                                          xfrm_address_t *saddr,
                                          xfrm_address_t *daddr)
{
        struct flowi fl = {};
        struct dst_entry *dst;
        int err;

        memcpy(&fl.fl6_dst, daddr, sizeof(fl.fl6_dst));
        if (saddr)
                memcpy(&fl.fl6_src, saddr, sizeof(fl.fl6_src));

        dst = ip6_route_output(net, NULL, &fl);

        err = dst->error;
        if (dst->error) {
                dst_release(dst);
                dst = ERR_PTR(err);
        }

        return dst;
}

static int xfrm6_get_saddr(struct net *net,
                           xfrm_address_t *saddr, xfrm_address_t *daddr)
{
        struct dst_entry *dst;
        struct net_device *dev;

        dst = xfrm6_dst_lookup(net, 0, NULL, daddr);
        if (IS_ERR(dst))
                return -EHOSTUNREACH;

        dev = ip6_dst_idev(dst)->dev;
        ipv6_dev_get_saddr(dev_net(dev), dev,
                           (struct in6_addr *)&daddr->a6, 0,
                           (struct in6_addr *)&saddr->a6);
        dst_release(dst);
        return 0;
}

static struct dst_entry *
__xfrm6_find_bundle(struct flowi *fl, struct xfrm_policy *policy)
{
        struct dst_entry *dst;

        /* Still not clear if we should set fl->fl6_{src,dst}... */
        read_lock_bh(&policy->lock);
        for (dst = policy->bundles; dst; dst = dst->next) {
                struct xfrm_dst *xdst = (struct xfrm_dst*)dst;
                struct in6_addr fl_dst_prefix, fl_src_prefix;

                ipv6_addr_prefix(&fl_dst_prefix,
                                 &fl->fl6_dst,
                                 xdst->u.rt6.rt6i_dst.plen);
                ipv6_addr_prefix(&fl_src_prefix,
                                 &fl->fl6_src,
                                 xdst->u.rt6.rt6i_src.plen);
                if (ipv6_addr_equal(&xdst->u.rt6.rt6i_dst.addr, &fl_dst_prefix) &&
                    ipv6_addr_equal(&xdst->u.rt6.rt6i_src.addr, &fl_src_prefix) &&
                    xfrm_bundle_ok(policy, xdst, fl, AF_INET6,
                                   (xdst->u.rt6.rt6i_dst.plen != 128 ||
                                    xdst->u.rt6.rt6i_src.plen != 128))) {
                        dst_clone(dst);
                        break;
                }
        }
        read_unlock_bh(&policy->lock);
        return dst;
}

static int xfrm6_get_tos(struct flowi *fl)
{
        return 0;
}

static int xfrm6_init_path(struct xfrm_dst *path, struct dst_entry *dst,
                           int nfheader_len)
{
        if (dst->ops->family == AF_INET6) {
                struct rt6_info *rt = (struct rt6_info*)dst;
                if (rt->rt6i_node)
                        path->path_cookie = rt->rt6i_node->fn_sernum;
        }

        path->u.rt6.rt6i_nfheader_len = nfheader_len;

        return 0;
}

static int xfrm6_fill_dst(struct xfrm_dst *xdst, struct net_device *dev)
{
        struct rt6_info *rt = (struct rt6_info*)xdst->route;

        xdst->u.dst.dev = dev;
        dev_hold(dev);

        xdst->u.rt6.rt6i_idev = in6_dev_get(rt->u.dst.dev);
        if (!xdst->u.rt6.rt6i_idev)
                return -ENODEV;

        /* Sheit... I remember I did this right. Apparently,
         * it was magically lost, so this code needs audit */
        xdst->u.rt6.rt6i_flags = rt->rt6i_flags & (RTF_ANYCAST |
                                                   RTF_LOCAL);
        xdst->u.rt6.rt6i_metric = rt->rt6i_metric;
        xdst->u.rt6.rt6i_node = rt->rt6i_node;
        if (rt->rt6i_node)
                xdst->route_cookie = rt->rt6i_node->fn_sernum;
        xdst->u.rt6.rt6i_gateway = rt->rt6i_gateway;
        xdst->u.rt6.rt6i_dst = rt->rt6i_dst;
        xdst->u.rt6.rt6i_src = rt->rt6i_src;

        return 0;
}

static inline void
_decode_session6(struct sk_buff *skb, struct flowi *fl, int reverse)
{
        int onlyproto = 0;
        u16 offset = skb_network_header_len(skb);
        struct ipv6hdr *hdr = ipv6_hdr(skb);
        struct ipv6_opt_hdr *exthdr;
        const unsigned char *nh = skb_network_header(skb);
        u8 nexthdr = nh[IP6CB(skb)->nhoff];

        memset(fl, 0, sizeof(struct flowi));
        ipv6_addr_copy(&fl->fl6_dst, reverse ? &hdr->saddr : &hdr->daddr);
        ipv6_addr_copy(&fl->fl6_src, reverse ? &hdr->daddr : &hdr->saddr);

        while (nh + offset + 1 < skb->data ||
               pskb_may_pull(skb, nh + offset + 1 - skb->data)) {
                nh = skb_network_header(skb);
                exthdr = (struct ipv6_opt_hdr *)(nh + offset);

                switch (nexthdr) {
                case NEXTHDR_FRAGMENT:
                        onlyproto = 1;
                case NEXTHDR_ROUTING:
                case NEXTHDR_HOP:
                case NEXTHDR_DEST:
                        offset += ipv6_optlen(exthdr);
                        nexthdr = exthdr->nexthdr;
                        exthdr = (struct ipv6_opt_hdr *)(nh + offset);
                        break;

                case IPPROTO_UDP:
                case IPPROTO_UDPLITE:
                case IPPROTO_TCP:
                case IPPROTO_SCTP:
                case IPPROTO_DCCP:
                        if (!onlyproto && (nh + offset + 4 < skb->data ||
                             pskb_may_pull(skb, nh + offset + 4 - skb->data))) {
                                __be16 *ports = (__be16 *)exthdr;

                                fl->fl_ip_sport = ports[!!reverse];
                                fl->fl_ip_dport = ports[!reverse];
                        }
                        fl->proto = nexthdr;
                        return;

                case IPPROTO_ICMPV6:
                        if (!onlyproto && pskb_may_pull(skb, nh + offset + 2 - skb->data)) {
                                u8 *icmp = (u8 *)exthdr;

                                fl->fl_icmp_type = icmp[0];
                                fl->fl_icmp_code = icmp[1];
                        }
                        fl->proto = nexthdr;
                        return;

#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
                case IPPROTO_MH:
                        if (!onlyproto && pskb_may_pull(skb, nh + offset + 3 - skb->data)) {
                                struct ip6_mh *mh;
                                mh = (struct ip6_mh *)exthdr;

                                fl->fl_mh_type = mh->ip6mh_type;
                        }
                        fl->proto = nexthdr;
                        return;
#endif

                /* XXX Why are there these headers? */
                case IPPROTO_AH:
                case IPPROTO_ESP:
                case IPPROTO_COMP:
                default:
                        fl->fl_ipsec_spi = 0;
                        fl->proto = nexthdr;
                        return;
                }
        }
}

static inline int xfrm6_garbage_collect(struct dst_ops *ops)
{
        xfrm6_policy_afinfo.garbage_collect(&init_net);
        return (atomic_read(&xfrm6_dst_ops.entries) > xfrm6_dst_ops.gc_thresh*2);
}

static void xfrm6_update_pmtu(struct dst_entry *dst, u32 mtu)
{
        struct xfrm_dst *xdst = (struct xfrm_dst *)dst;
        struct dst_entry *path = xdst->route;

        path->ops->update_pmtu(path, mtu);
}

static void xfrm6_dst_destroy(struct dst_entry *dst)
{
        struct xfrm_dst *xdst = (struct xfrm_dst *)dst;

        if (likely(xdst->u.rt6.rt6i_idev))
                in6_dev_put(xdst->u.rt6.rt6i_idev);
        xfrm_dst_destroy(xdst);
}

static void xfrm6_dst_ifdown(struct dst_entry *dst, struct net_device *dev,
                             int unregister)
{
        struct xfrm_dst *xdst;

        if (!unregister)
                return;

        xdst = (struct xfrm_dst *)dst;
        if (xdst->u.rt6.rt6i_idev->dev == dev) {
                struct inet6_dev *loopback_idev =
                        in6_dev_get(dev_net(dev)->loopback_dev);
                BUG_ON(!loopback_idev);

                do {
                        in6_dev_put(xdst->u.rt6.rt6i_idev);
                        xdst->u.rt6.rt6i_idev = loopback_idev;
                        in6_dev_hold(loopback_idev);
                        xdst = (struct xfrm_dst *)xdst->u.dst.child;
                } while (xdst->u.dst.xfrm);

                __in6_dev_put(loopback_idev);
        }

        xfrm_dst_ifdown(dst, dev);
}

static struct dst_ops xfrm6_dst_ops = {
        .family =               AF_INET6,
        .protocol =             cpu_to_be16(ETH_P_IPV6),
        .gc =                   xfrm6_garbage_collect,
        .update_pmtu =          xfrm6_update_pmtu,
        .destroy =              xfrm6_dst_destroy,
        .ifdown =               xfrm6_dst_ifdown,
        .local_out =            __ip6_local_out,
        .gc_thresh =            1024,
        .entries =              ATOMIC_INIT(0),
};

static struct xfrm_policy_afinfo xfrm6_policy_afinfo = {
        .family =               AF_INET6,
        .dst_ops =              &xfrm6_dst_ops,
        .dst_lookup =           xfrm6_dst_lookup,
        .get_saddr =            xfrm6_get_saddr,
        .find_bundle =          __xfrm6_find_bundle,
        .decode_session =       _decode_session6,
        .get_tos =              xfrm6_get_tos,
        .init_path =            xfrm6_init_path,
        .fill_dst =             xfrm6_fill_dst,
};

static int __init xfrm6_policy_init(void)
{
        return xfrm_policy_register_afinfo(&xfrm6_policy_afinfo);
}

static void xfrm6_policy_fini(void)
{
        xfrm_policy_unregister_afinfo(&xfrm6_policy_afinfo);
}

#ifdef CONFIG_SYSCTL
static struct ctl_table xfrm6_policy_table[] = {
        {
                .ctl_name       = CTL_UNNUMBERED,
                .procname       = "xfrm6_gc_thresh",
                .data           = &xfrm6_dst_ops.gc_thresh,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec,
        },
        { }
};

static struct ctl_table_header *sysctl_hdr;
#endif

int __init xfrm6_init(void)
{
        int ret;
        unsigned int gc_thresh;

        ret = xfrm6_policy_init();
        if (ret)
                goto out;

        ret = xfrm6_state_init();
        if (ret)
                goto out_policy;
        /*
         * We need a good default value for the xfrm6 gc threshold.
         * In ipv4 we set it to the route hash table size * 8, which
         * is half the size of the maximaum route cache for ipv4.  It
         * would be good to do the same thing for v6, except the table is
         * constructed differently here.  Here each table for a net namespace
         * can have FIB_TABLE_HASHSZ entries, so lets go with the same
         * computation that we used for ipv4 here.  Also, lets keep the initial
         * gc_thresh to a minimum of 1024, since, the ipv6 route cache defaults
         * to that as a minimum as well
         */
        gc_thresh = FIB6_TABLE_HASHSZ * 8;
        xfrm6_dst_ops.gc_thresh = (gc_thresh < 1024) ? 1024 : gc_thresh;
#ifdef CONFIG_SYSCTL
        sysctl_hdr = register_net_sysctl_table(&init_net, net_ipv6_ctl_path,
                                                xfrm6_policy_table);
#endif
out:
        return ret;
out_policy:
        xfrm6_policy_fini();
        goto out;
}

void xfrm6_fini(void)
{
#ifdef CONFIG_SYSCTL
        if (sysctl_hdr)
                unregister_net_sysctl_table(sysctl_hdr);
#endif
        //xfrm6_input_fini();
        xfrm6_policy_fini();
        xfrm6_state_fini();
}