/*
 * xfrm4_policy.c
 *
 * Changes:
 *      Kazunori MIYAZAWA @USAGI
 *      YOSHIFUJI Hideaki @USAGI
 *              Split up af-specific portion
 *
 */

#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/inetdevice.h>
#include <linux/if_tunnel.h>
#include <net/dst.h>
#include <net/xfrm.h>
#include <net/ip.h>

static struct xfrm_policy_afinfo xfrm4_policy_afinfo;

static struct dst_entry *__xfrm4_dst_lookup(struct net *net, struct flowi4 *fl4,
                                            int tos,
                                            const xfrm_address_t *saddr,
                                            const xfrm_address_t *daddr)
{
        struct rtable *rt;

        memset(fl4, 0, sizeof(*fl4));
        fl4->daddr = daddr->a4;
        fl4->flowi4_tos = tos;
        if (saddr)
                fl4->saddr = saddr->a4;

        rt = __ip_route_output_key(net, fl4);
        if (!IS_ERR(rt))
                return &rt->dst;

        return ERR_CAST(rt);
}

static struct dst_entry *xfrm4_dst_lookup(struct net *net, int tos,
                                          const xfrm_address_t *saddr,
                                          const xfrm_address_t *daddr)
{
        struct flowi4 fl4;

        return __xfrm4_dst_lookup(net, &fl4, tos, saddr, daddr);
}

static int xfrm4_get_saddr(struct net *net,
                           xfrm_address_t *saddr, xfrm_address_t *daddr)
{
        struct dst_entry *dst;
        struct flowi4 fl4;

        dst = __xfrm4_dst_lookup(net, &fl4, 0, NULL, daddr);
        if (IS_ERR(dst))
                return -EHOSTUNREACH;

        saddr->a4 = fl4.saddr;
        dst_release(dst);
        return 0;
}

static int xfrm4_get_tos(const struct flowi *fl)
{
        return IPTOS_RT_MASK & fl->u.ip4.flowi4_tos; /* Strip ECN bits */
}

static int xfrm4_init_path(struct xfrm_dst *path, struct dst_entry *dst,
                           int nfheader_len)
{
        return 0;
}

static int xfrm4_fill_dst(struct xfrm_dst *xdst, struct net_device *dev,
                          const struct flowi *fl)
{
        struct rtable *rt = (struct rtable *)xdst->route;
        const struct flowi4 *fl4 = &fl->u.ip4;

        xdst->u.rt.rt_key_dst = fl4->daddr;
        xdst->u.rt.rt_key_src = fl4->saddr;
        xdst->u.rt.rt_key_tos = fl4->flowi4_tos;
        xdst->u.rt.rt_route_iif = fl4->flowi4_iif;
        xdst->u.rt.rt_iif = fl4->flowi4_iif;
        xdst->u.rt.rt_oif = fl4->flowi4_oif;
        xdst->u.rt.rt_mark = fl4->flowi4_mark;

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

        xdst->u.rt.peer = rt->peer;
        if (rt->peer)
                atomic_inc(&rt->peer->refcnt);

        /* Sheit... I remember I did this right. Apparently,
         * it was magically lost, so this code needs audit */
        xdst->u.rt.rt_flags = rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST |
                                              RTCF_LOCAL);
        xdst->u.rt.rt_type = rt->rt_type;
        xdst->u.rt.rt_src = rt->rt_src;
        xdst->u.rt.rt_dst = rt->rt_dst;
        xdst->u.rt.rt_gateway = rt->rt_gateway;
        xdst->u.rt.rt_spec_dst = rt->rt_spec_dst;

        return 0;
}

static void
_decode_session4(struct sk_buff *skb, struct flowi *fl, int reverse)
{
        const struct iphdr *iph = ip_hdr(skb);
        u8 *xprth = skb_network_header(skb) + iph->ihl * 4;
        struct flowi4 *fl4 = &fl->u.ip4;

        memset(fl4, 0, sizeof(struct flowi4));
        fl4->flowi4_mark = skb->mark;

        if (!ip_is_fragment(iph)) {
                switch (iph->protocol) {
                case IPPROTO_UDP:
                case IPPROTO_UDPLITE:
                case IPPROTO_TCP:
                case IPPROTO_SCTP:
                case IPPROTO_DCCP:
                        if (xprth + 4 < skb->data ||
                            pskb_may_pull(skb, xprth + 4 - skb->data)) {
                                __be16 *ports = (__be16 *)xprth;

                                fl4->fl4_sport = ports[!!reverse];
                                fl4->fl4_dport = ports[!reverse];
                        }
                        break;

                case IPPROTO_ICMP:
                        if (pskb_may_pull(skb, xprth + 2 - skb->data)) {
                                u8 *icmp = xprth;

                                fl4->fl4_icmp_type = icmp[0];
                                fl4->fl4_icmp_code = icmp[1];
                        }
                        break;

                case IPPROTO_ESP:
                        if (pskb_may_pull(skb, xprth + 4 - skb->data)) {
                                __be32 *ehdr = (__be32 *)xprth;

                                fl4->fl4_ipsec_spi = ehdr[0];
                        }
                        break;

                case IPPROTO_AH:
                        if (pskb_may_pull(skb, xprth + 8 - skb->data)) {
                                __be32 *ah_hdr = (__be32*)xprth;

                                fl4->fl4_ipsec_spi = ah_hdr[1];
                        }
                        break;

                case IPPROTO_COMP:
                        if (pskb_may_pull(skb, xprth + 4 - skb->data)) {
                                __be16 *ipcomp_hdr = (__be16 *)xprth;

                                fl4->fl4_ipsec_spi = htonl(ntohs(ipcomp_hdr[1]));
                        }
                        break;

                case IPPROTO_GRE:
                        if (pskb_may_pull(skb, xprth + 12 - skb->data)) {
                                __be16 *greflags = (__be16 *)xprth;
                                __be32 *gre_hdr = (__be32 *)xprth;

                                if (greflags[0] & GRE_KEY) {
                                        if (greflags[0] & GRE_CSUM)
                                                gre_hdr++;
                                        fl4->fl4_gre_key = gre_hdr[1];
                                }
                        }
                        break;

                default:
                        fl4->fl4_ipsec_spi = 0;
                        break;
                }
        }
        fl4->flowi4_proto = iph->protocol;
        fl4->daddr = reverse ? iph->saddr : iph->daddr;
        fl4->saddr = reverse ? iph->daddr : iph->saddr;
        fl4->flowi4_tos = iph->tos;
}

static inline int xfrm4_garbage_collect(struct dst_ops *ops)
{
        struct net *net = container_of(ops, struct net, xfrm.xfrm4_dst_ops);

        xfrm4_policy_afinfo.garbage_collect(net);
        return (dst_entries_get_slow(ops) > ops->gc_thresh * 2);
}

static void xfrm4_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 xfrm4_dst_destroy(struct dst_entry *dst)
{
        struct xfrm_dst *xdst = (struct xfrm_dst *)dst;

        dst_destroy_metrics_generic(dst);

        if (likely(xdst->u.rt.peer))
                inet_putpeer(xdst->u.rt.peer);

        xfrm_dst_destroy(xdst);
}

static void xfrm4_dst_ifdown(struct dst_entry *dst, struct net_device *dev,
                             int unregister)
{
        if (!unregister)
                return;

        xfrm_dst_ifdown(dst, dev);
}

static struct dst_ops xfrm4_dst_ops = {
        .family =               AF_INET,
        .protocol =             cpu_to_be16(ETH_P_IP),
        .gc =                   xfrm4_garbage_collect,
        .update_pmtu =          xfrm4_update_pmtu,
        .cow_metrics =          dst_cow_metrics_generic,
        .destroy =              xfrm4_dst_destroy,
        .ifdown =               xfrm4_dst_ifdown,
        .local_out =            __ip_local_out,
        .gc_thresh =            1024,
};

static struct xfrm_policy_afinfo xfrm4_policy_afinfo = {
        .family =               AF_INET,
        .dst_ops =              &xfrm4_dst_ops,
        .dst_lookup =           xfrm4_dst_lookup,
        .get_saddr =            xfrm4_get_saddr,
        .decode_session =       _decode_session4,
        .get_tos =              xfrm4_get_tos,
        .init_path =            xfrm4_init_path,
        .fill_dst =             xfrm4_fill_dst,
        .blackhole_route =      ipv4_blackhole_route,
};

#ifdef CONFIG_SYSCTL
static struct ctl_table xfrm4_policy_table[] = {
        {
                .procname       = "xfrm4_gc_thresh",
                .data           = &init_net.xfrm.xfrm4_dst_ops.gc_thresh,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec,
        },
        { }
};

static struct ctl_table_header *sysctl_hdr;
#endif

static void __init xfrm4_policy_init(void)
{
        xfrm_policy_register_afinfo(&xfrm4_policy_afinfo);
}

static void __exit xfrm4_policy_fini(void)
{
#ifdef CONFIG_SYSCTL
        if (sysctl_hdr)
                unregister_net_sysctl_table(sysctl_hdr);
#endif
        xfrm_policy_unregister_afinfo(&xfrm4_policy_afinfo);
}

void __init xfrm4_init(int rt_max_size)
{
        /*
         * Select a default value for the gc_thresh based on the main route
         * table hash size.  It seems to me the worst case scenario is when
         * we have ipsec operating in transport mode, in which we create a
         * dst_entry per socket.  The xfrm gc algorithm starts trying to remove
         * entries at gc_thresh, and prevents new allocations as 2*gc_thresh
         * so lets set an initial xfrm gc_thresh value at the rt_max_size/2.
         * That will let us store an ipsec connection per route table entry,
         * and start cleaning when were 1/2 full
         */
        xfrm4_dst_ops.gc_thresh = rt_max_size/2;
        dst_entries_init(&xfrm4_dst_ops);

        xfrm4_state_init();
        xfrm4_policy_init();
#ifdef CONFIG_SYSCTL
        sysctl_hdr = register_net_sysctl_table(&init_net, net_ipv4_ctl_path,
                                                xfrm4_policy_table);
#endif
}