// SPDX-License-Identifier: GPL-2.0
/*
 * 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 <net/dst.h>
#include <net/xfrm.h>
#include <net/ip.h>
#include <net/l3mdev.h>

static struct dst_entry *__xfrm4_dst_lookup(struct net *net, struct flowi4 *fl4,
                                            int tos, int oif,
                                            const xfrm_address_t *saddr,
                                            const xfrm_address_t *daddr,
                                            u32 mark)
{
        struct rtable *rt;

        memset(fl4, 0, sizeof(*fl4));
        fl4->daddr = daddr->a4;
        fl4->flowi4_tos = tos;
        fl4->flowi4_oif = l3mdev_master_ifindex_by_index(net, oif);
        fl4->flowi4_mark = mark;
        if (saddr)
                fl4->saddr = saddr->a4;

        fl4->flowi4_flags = FLOWI_FLAG_SKIP_NH_OIF;

        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, int oif,
                                          const xfrm_address_t *saddr,
                                          const xfrm_address_t *daddr,
                                          u32 mark)
{
        struct flowi4 fl4;

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

static int xfrm4_get_saddr(struct net *net, int oif,
                           xfrm_address_t *saddr, xfrm_address_t *daddr,
                           u32 mark)
{
        struct dst_entry *dst;
        struct flowi4 fl4;

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

        saddr->a4 = fl4.saddr;
        dst_release(dst);
        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_iif = fl4->flowi4_iif;

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

        /* Sheit... I remember I did this right. Apparently,
         * it was magically lost, so this code needs audit */
        xdst->u.rt.rt_is_input = rt->rt_is_input;
        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_gw_family = rt->rt_gw_family;
        if (rt->rt_gw_family == AF_INET)
                xdst->u.rt.rt_gw4 = rt->rt_gw4;
        else if (rt->rt_gw_family == AF_INET6)
                xdst->u.rt.rt_gw6 = rt->rt_gw6;
        xdst->u.rt.rt_pmtu = rt->rt_pmtu;
        xdst->u.rt.rt_mtu_locked = rt->rt_mtu_locked;
        INIT_LIST_HEAD(&xdst->u.rt.rt_uncached);
        rt_add_uncached_list(&xdst->u.rt);

        return 0;
}

static void xfrm4_update_pmtu(struct dst_entry *dst, struct sock *sk,
                              struct sk_buff *skb, u32 mtu)
{
        struct xfrm_dst *xdst = (struct xfrm_dst *)dst;
        struct dst_entry *path = xdst->route;

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

static void xfrm4_redirect(struct dst_entry *dst, struct sock *sk,
                           struct sk_buff *skb)
{
        struct xfrm_dst *xdst = (struct xfrm_dst *)dst;
        struct dst_entry *path = xdst->route;

        path->ops->redirect(path, sk, skb);
}

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

        dst_destroy_metrics_generic(dst);
        if (xdst->u.rt.rt_uncached_list)
                rt_del_uncached_list(&xdst->u.rt);
        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_template = {
        .family =               AF_INET,
        .update_pmtu =          xfrm4_update_pmtu,
        .redirect =             xfrm4_redirect,
        .cow_metrics =          dst_cow_metrics_generic,
        .destroy =              xfrm4_dst_destroy,
        .ifdown =               xfrm4_dst_ifdown,
        .local_out =            __ip_local_out,
        .gc_thresh =            32768,
};

static const struct xfrm_policy_afinfo xfrm4_policy_afinfo = {
        .dst_ops =              &xfrm4_dst_ops_template,
        .dst_lookup =           xfrm4_dst_lookup,
        .get_saddr =            xfrm4_get_saddr,
        .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 __net_init int xfrm4_net_sysctl_init(struct net *net)
{
        struct ctl_table *table;
        struct ctl_table_header *hdr;

        table = xfrm4_policy_table;
        if (!net_eq(net, &init_net)) {
                table = kmemdup(table, sizeof(xfrm4_policy_table), GFP_KERNEL);
                if (!table)
                        goto err_alloc;

                table[0].data = &net->xfrm.xfrm4_dst_ops.gc_thresh;
        }

        hdr = register_net_sysctl(net, "net/ipv4", table);
        if (!hdr)
                goto err_reg;

        net->ipv4.xfrm4_hdr = hdr;
        return 0;

err_reg:
        if (!net_eq(net, &init_net))
                kfree(table);
err_alloc:
        return -ENOMEM;
}

static __net_exit void xfrm4_net_sysctl_exit(struct net *net)
{
        struct ctl_table *table;

        if (!net->ipv4.xfrm4_hdr)
                return;

        table = net->ipv4.xfrm4_hdr->ctl_table_arg;
        unregister_net_sysctl_table(net->ipv4.xfrm4_hdr);
        if (!net_eq(net, &init_net))
                kfree(table);
}
#else /* CONFIG_SYSCTL */
static inline int xfrm4_net_sysctl_init(struct net *net)
{
        return 0;
}

static inline void xfrm4_net_sysctl_exit(struct net *net)
{
}
#endif

static int __net_init xfrm4_net_init(struct net *net)
{
        int ret;

        memcpy(&net->xfrm.xfrm4_dst_ops, &xfrm4_dst_ops_template,
               sizeof(xfrm4_dst_ops_template));
        ret = dst_entries_init(&net->xfrm.xfrm4_dst_ops);
        if (ret)
                return ret;

        ret = xfrm4_net_sysctl_init(net);
        if (ret)
                dst_entries_destroy(&net->xfrm.xfrm4_dst_ops);

        return ret;
}

static void __net_exit xfrm4_net_exit(struct net *net)
{
        xfrm4_net_sysctl_exit(net);
        dst_entries_destroy(&net->xfrm.xfrm4_dst_ops);
}

static struct pernet_operations __net_initdata xfrm4_net_ops = {
        .init   = xfrm4_net_init,
        .exit   = xfrm4_net_exit,
};

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

void __init xfrm4_init(void)
{
        xfrm4_state_init();
        xfrm4_policy_init();
        xfrm4_protocol_init();
        register_pernet_subsys(&xfrm4_net_ops);
}