// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * net/core/dst_cache.c - dst entry cache
 *
 * Copyright (c) 2016 Paolo Abeni <pabeni@redhat.com>
 */

#include <linux/kernel.h>
#include <linux/percpu.h>
#include <net/dst_cache.h>
#include <net/route.h>
#if IS_ENABLED(CONFIG_IPV6)
#include <net/ip6_fib.h>
#endif
#include <uapi/linux/in.h>

struct dst_cache_pcpu {
        unsigned long refresh_ts;
        struct dst_entry *dst;
        local_lock_t bh_lock;
        u32 cookie;
        union {
                struct in_addr in_saddr;
                struct in6_addr in6_saddr;
        };
};

static void dst_cache_per_cpu_dst_set(struct dst_cache_pcpu *dst_cache,
                                      struct dst_entry *dst, u32 cookie)
{
        DEBUG_NET_WARN_ON_ONCE(!in_softirq());
        dst_release(dst_cache->dst);
        if (dst)
                dst_hold(dst);

        dst_cache->cookie = cookie;
        dst_cache->dst = dst;
}

static struct dst_entry *dst_cache_per_cpu_get(struct dst_cache *dst_cache,
                                               struct dst_cache_pcpu *idst)
{
        struct dst_entry *dst;

        DEBUG_NET_WARN_ON_ONCE(!in_softirq());
        dst = idst->dst;
        if (!dst)
                goto fail;

        /* the cache already hold a dst reference; it can't go away */
        dst_hold(dst);

        if (unlikely(!time_after(idst->refresh_ts,
                                 READ_ONCE(dst_cache->reset_ts)) ||
                     (READ_ONCE(dst->obsolete) && !dst->ops->check(dst, idst->cookie)))) {
                dst_cache_per_cpu_dst_set(idst, NULL, 0);
                dst_release(dst);
                goto fail;
        }
        return dst;

fail:
        idst->refresh_ts = jiffies;
        return NULL;
}

struct dst_entry *dst_cache_get(struct dst_cache *dst_cache)
{
        struct dst_entry *dst;

        if (!dst_cache->cache)
                return NULL;

        local_lock_nested_bh(&dst_cache->cache->bh_lock);
        dst = dst_cache_per_cpu_get(dst_cache, this_cpu_ptr(dst_cache->cache));
        local_unlock_nested_bh(&dst_cache->cache->bh_lock);
        return dst;
}
EXPORT_SYMBOL_GPL(dst_cache_get);

struct rtable *dst_cache_get_ip4(struct dst_cache *dst_cache, __be32 *saddr)
{
        struct dst_cache_pcpu *idst;
        struct dst_entry *dst;

        if (!dst_cache->cache)
                return NULL;

        local_lock_nested_bh(&dst_cache->cache->bh_lock);
        idst = this_cpu_ptr(dst_cache->cache);
        dst = dst_cache_per_cpu_get(dst_cache, idst);
        if (!dst) {
                local_unlock_nested_bh(&dst_cache->cache->bh_lock);
                return NULL;
        }

        *saddr = idst->in_saddr.s_addr;
        local_unlock_nested_bh(&dst_cache->cache->bh_lock);
        return dst_rtable(dst);
}
EXPORT_SYMBOL_GPL(dst_cache_get_ip4);

void dst_cache_set_ip4(struct dst_cache *dst_cache, struct dst_entry *dst,
                       __be32 saddr)
{
        struct dst_cache_pcpu *idst;

        if (!dst_cache->cache)
                return;

        local_lock_nested_bh(&dst_cache->cache->bh_lock);
        idst = this_cpu_ptr(dst_cache->cache);
        dst_cache_per_cpu_dst_set(idst, dst, 0);
        idst->in_saddr.s_addr = saddr;
        local_unlock_nested_bh(&dst_cache->cache->bh_lock);
}
EXPORT_SYMBOL_GPL(dst_cache_set_ip4);

#if IS_ENABLED(CONFIG_IPV6)
void dst_cache_set_ip6(struct dst_cache *dst_cache, struct dst_entry *dst,
                       const struct in6_addr *saddr)
{
        struct dst_cache_pcpu *idst;

        if (!dst_cache->cache)
                return;

        local_lock_nested_bh(&dst_cache->cache->bh_lock);

        idst = this_cpu_ptr(dst_cache->cache);
        dst_cache_per_cpu_dst_set(idst, dst,
                                  rt6_get_cookie(dst_rt6_info(dst)));
        idst->in6_saddr = *saddr;
        local_unlock_nested_bh(&dst_cache->cache->bh_lock);
}
EXPORT_SYMBOL_GPL(dst_cache_set_ip6);

struct dst_entry *dst_cache_get_ip6(struct dst_cache *dst_cache,
                                    struct in6_addr *saddr)
{
        struct dst_cache_pcpu *idst;
        struct dst_entry *dst;

        if (!dst_cache->cache)
                return NULL;

        local_lock_nested_bh(&dst_cache->cache->bh_lock);

        idst = this_cpu_ptr(dst_cache->cache);
        dst = dst_cache_per_cpu_get(dst_cache, idst);
        if (!dst) {
                local_unlock_nested_bh(&dst_cache->cache->bh_lock);
                return NULL;
        }

        *saddr = idst->in6_saddr;
        local_unlock_nested_bh(&dst_cache->cache->bh_lock);
        return dst;
}
EXPORT_SYMBOL_GPL(dst_cache_get_ip6);
#endif

int dst_cache_init(struct dst_cache *dst_cache, gfp_t gfp)
{
        unsigned int i;

        dst_cache->cache = alloc_percpu_gfp(struct dst_cache_pcpu,
                                            gfp | __GFP_ZERO);
        if (!dst_cache->cache)
                return -ENOMEM;
        for_each_possible_cpu(i)
                local_lock_init(&per_cpu_ptr(dst_cache->cache, i)->bh_lock);

        dst_cache_reset(dst_cache);
        return 0;
}
EXPORT_SYMBOL_GPL(dst_cache_init);

void dst_cache_destroy(struct dst_cache *dst_cache)
{
        int i;

        if (!dst_cache->cache)
                return;

        for_each_possible_cpu(i)
                dst_release(per_cpu_ptr(dst_cache->cache, i)->dst);

        free_percpu(dst_cache->cache);
}
EXPORT_SYMBOL_GPL(dst_cache_destroy);

void dst_cache_reset_now(struct dst_cache *dst_cache)
{
        int i;

        if (!dst_cache->cache)
                return;

        dst_cache_reset(dst_cache);
        for_each_possible_cpu(i) {
                struct dst_cache_pcpu *idst = per_cpu_ptr(dst_cache->cache, i);
                struct dst_entry *dst = idst->dst;

                idst->cookie = 0;
                idst->dst = NULL;
                dst_release(dst);
        }
}
EXPORT_SYMBOL_GPL(dst_cache_reset_now);