/* SPDX-License-Identifier: GPL-2.0 */
/*
 * net/dst.h    Protocol independent destination cache definitions.
 *
 * Authors:     Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
 *
 */

#ifndef _NET_DST_H
#define _NET_DST_H

#include <net/dst_ops.h>
#include <linux/netdevice.h>
#include <linux/rtnetlink.h>
#include <linux/rcupdate.h>
#include <linux/bug.h>
#include <linux/jiffies.h>
#include <linux/refcount.h>
#include <net/neighbour.h>
#include <asm/processor.h>

#define DST_GC_MIN      (HZ/10)
#define DST_GC_INC      (HZ/2)
#define DST_GC_MAX      (120*HZ)

/* Each dst_entry has reference count and sits in some parent list(s).
 * When it is removed from parent list, it is "freed" (dst_free).
 * After this it enters dead state (dst->obsolete > 0) and if its refcnt
 * is zero, it can be destroyed immediately, otherwise it is added
 * to gc list and garbage collector periodically checks the refcnt.
 */

struct sk_buff;

struct dst_entry {
        struct net_device       *dev;
        struct  dst_ops         *ops;
        unsigned long           _metrics;
        unsigned long           expires;
#ifdef CONFIG_XFRM
        struct xfrm_state       *xfrm;
#else
        void                    *__pad1;
#endif
        int                     (*input)(struct sk_buff *);
        int                     (*output)(struct net *net, struct sock *sk, struct sk_buff *skb);

        unsigned short          flags;
#define DST_HOST                0x0001
#define DST_NOXFRM              0x0002
#define DST_NOPOLICY            0x0004
#define DST_NOCOUNT             0x0008
#define DST_FAKE_RTABLE         0x0010
#define DST_XFRM_TUNNEL         0x0020
#define DST_XFRM_QUEUE          0x0040
#define DST_METADATA            0x0080

        /* A non-zero value of dst->obsolete forces by-hand validation
         * of the route entry.  Positive values are set by the generic
         * dst layer to indicate that the entry has been forcefully
         * destroyed.
         *
         * Negative values are used by the implementation layer code to
         * force invocation of the dst_ops->check() method.
         */
        short                   obsolete;
#define DST_OBSOLETE_NONE       0
#define DST_OBSOLETE_DEAD       2
#define DST_OBSOLETE_FORCE_CHK  -1
#define DST_OBSOLETE_KILL       -2
        unsigned short          header_len;     /* more space at head required */
        unsigned short          trailer_len;    /* space to reserve at tail */

        /*
         * __refcnt wants to be on a different cache line from
         * input/output/ops or performance tanks badly
         */
#ifdef CONFIG_64BIT
        atomic_t                __refcnt;       /* 64-bit offset 64 */
#endif
        int                     __use;
        unsigned long           lastuse;
        struct lwtunnel_state   *lwtstate;
        struct rcu_head         rcu_head;
        short                   error;
        short                   __pad;
        __u32                   tclassid;
#ifndef CONFIG_64BIT
        atomic_t                __refcnt;       /* 32-bit offset 64 */
#endif
};

struct dst_metrics {
        u32             metrics[RTAX_MAX];
        refcount_t      refcnt;
};
extern const struct dst_metrics dst_default_metrics;

u32 *dst_cow_metrics_generic(struct dst_entry *dst, unsigned long old);

#define DST_METRICS_READ_ONLY           0x1UL
#define DST_METRICS_REFCOUNTED          0x2UL
#define DST_METRICS_FLAGS               0x3UL
#define __DST_METRICS_PTR(Y)    \
        ((u32 *)((Y) & ~DST_METRICS_FLAGS))
#define DST_METRICS_PTR(X)      __DST_METRICS_PTR((X)->_metrics)

static inline bool dst_metrics_read_only(const struct dst_entry *dst)
{
        return dst->_metrics & DST_METRICS_READ_ONLY;
}

void __dst_destroy_metrics_generic(struct dst_entry *dst, unsigned long old);

static inline void dst_destroy_metrics_generic(struct dst_entry *dst)
{
        unsigned long val = dst->_metrics;
        if (!(val & DST_METRICS_READ_ONLY))
                __dst_destroy_metrics_generic(dst, val);
}

static inline u32 *dst_metrics_write_ptr(struct dst_entry *dst)
{
        unsigned long p = dst->_metrics;

        BUG_ON(!p);

        if (p & DST_METRICS_READ_ONLY)
                return dst->ops->cow_metrics(dst, p);
        return __DST_METRICS_PTR(p);
}

/* This may only be invoked before the entry has reached global
 * visibility.
 */
static inline void dst_init_metrics(struct dst_entry *dst,
                                    const u32 *src_metrics,
                                    bool read_only)
{
        dst->_metrics = ((unsigned long) src_metrics) |
                (read_only ? DST_METRICS_READ_ONLY : 0);
}

static inline void dst_copy_metrics(struct dst_entry *dest, const struct dst_entry *src)
{
        u32 *dst_metrics = dst_metrics_write_ptr(dest);

        if (dst_metrics) {
                u32 *src_metrics = DST_METRICS_PTR(src);

                memcpy(dst_metrics, src_metrics, RTAX_MAX * sizeof(u32));
        }
}

static inline u32 *dst_metrics_ptr(struct dst_entry *dst)
{
        return DST_METRICS_PTR(dst);
}

static inline u32
dst_metric_raw(const struct dst_entry *dst, const int metric)
{
        u32 *p = DST_METRICS_PTR(dst);

        return p[metric-1];
}

static inline u32
dst_metric(const struct dst_entry *dst, const int metric)
{
        WARN_ON_ONCE(metric == RTAX_HOPLIMIT ||
                     metric == RTAX_ADVMSS ||
                     metric == RTAX_MTU);
        return dst_metric_raw(dst, metric);
}

static inline u32
dst_metric_advmss(const struct dst_entry *dst)
{
        u32 advmss = dst_metric_raw(dst, RTAX_ADVMSS);

        if (!advmss)
                advmss = dst->ops->default_advmss(dst);

        return advmss;
}

static inline void dst_metric_set(struct dst_entry *dst, int metric, u32 val)
{
        u32 *p = dst_metrics_write_ptr(dst);

        if (p)
                p[metric-1] = val;
}

/* Kernel-internal feature bits that are unallocated in user space. */
#define DST_FEATURE_ECN_CA      (1 << 31)

#define DST_FEATURE_MASK        (DST_FEATURE_ECN_CA)
#define DST_FEATURE_ECN_MASK    (DST_FEATURE_ECN_CA | RTAX_FEATURE_ECN)

static inline u32
dst_feature(const struct dst_entry *dst, u32 feature)
{
        return dst_metric(dst, RTAX_FEATURES) & feature;
}

static inline u32 dst_mtu(const struct dst_entry *dst)
{
        return dst->ops->mtu(dst);
}

/* RTT metrics are stored in milliseconds for user ABI, but used as jiffies */
static inline unsigned long dst_metric_rtt(const struct dst_entry *dst, int metric)
{
        return msecs_to_jiffies(dst_metric(dst, metric));
}

static inline u32
dst_allfrag(const struct dst_entry *dst)
{
        int ret = dst_feature(dst,  RTAX_FEATURE_ALLFRAG);
        return ret;
}

static inline int
dst_metric_locked(const struct dst_entry *dst, int metric)
{
        return dst_metric(dst, RTAX_LOCK) & (1<<metric);
}

static inline void dst_hold(struct dst_entry *dst)
{
        /*
         * If your kernel compilation stops here, please check
         * the placement of __refcnt in struct dst_entry
         */
        BUILD_BUG_ON(offsetof(struct dst_entry, __refcnt) & 63);
        WARN_ON(atomic_inc_not_zero(&dst->__refcnt) == 0);
}

static inline void dst_use_noref(struct dst_entry *dst, unsigned long time)
{
        if (unlikely(time != dst->lastuse)) {
                dst->__use++;
                dst->lastuse = time;
        }
}

static inline void dst_hold_and_use(struct dst_entry *dst, unsigned long time)
{
        dst_hold(dst);
        dst_use_noref(dst, time);
}

static inline struct dst_entry *dst_clone(struct dst_entry *dst)
{
        if (dst)
                dst_hold(dst);
        return dst;
}

void dst_release(struct dst_entry *dst);

void dst_release_immediate(struct dst_entry *dst);

static inline void refdst_drop(unsigned long refdst)
{
        if (!(refdst & SKB_DST_NOREF))
                dst_release((struct dst_entry *)(refdst & SKB_DST_PTRMASK));
}

/**
 * skb_dst_drop - drops skb dst
 * @skb: buffer
 *
 * Drops dst reference count if a reference was taken.
 */
static inline void skb_dst_drop(struct sk_buff *skb)
{
        if (skb->_skb_refdst) {
                refdst_drop(skb->_skb_refdst);
                skb->_skb_refdst = 0UL;
        }
}

static inline void __skb_dst_copy(struct sk_buff *nskb, unsigned long refdst)
{
        nskb->_skb_refdst = refdst;
        if (!(nskb->_skb_refdst & SKB_DST_NOREF))
                dst_clone(skb_dst(nskb));
}

static inline void skb_dst_copy(struct sk_buff *nskb, const struct sk_buff *oskb)
{
        __skb_dst_copy(nskb, oskb->_skb_refdst);
}

/**
 * dst_hold_safe - Take a reference on a dst if possible
 * @dst: pointer to dst entry
 *
 * This helper returns false if it could not safely
 * take a reference on a dst.
 */
static inline bool dst_hold_safe(struct dst_entry *dst)
{
        return atomic_inc_not_zero(&dst->__refcnt);
}

/**
 * skb_dst_force - makes sure skb dst is refcounted
 * @skb: buffer
 *
 * If dst is not yet refcounted and not destroyed, grab a ref on it.
 */
static inline void skb_dst_force(struct sk_buff *skb)
{
        if (skb_dst_is_noref(skb)) {
                struct dst_entry *dst = skb_dst(skb);

                WARN_ON(!rcu_read_lock_held());
                if (!dst_hold_safe(dst))
                        dst = NULL;

                skb->_skb_refdst = (unsigned long)dst;
        }
}


/**
 *      __skb_tunnel_rx - prepare skb for rx reinsert
 *      @skb: buffer
 *      @dev: tunnel device
 *      @net: netns for packet i/o
 *
 *      After decapsulation, packet is going to re-enter (netif_rx()) our stack,
 *      so make some cleanups. (no accounting done)
 */
static inline void __skb_tunnel_rx(struct sk_buff *skb, struct net_device *dev,
                                   struct net *net)
{
        skb->dev = dev;

        /*
         * Clear hash so that we can recalulate the hash for the
         * encapsulated packet, unless we have already determine the hash
         * over the L4 4-tuple.
         */
        skb_clear_hash_if_not_l4(skb);
        skb_set_queue_mapping(skb, 0);
        skb_scrub_packet(skb, !net_eq(net, dev_net(dev)));
}

/**
 *      skb_tunnel_rx - prepare skb for rx reinsert
 *      @skb: buffer
 *      @dev: tunnel device
 *      @net: netns for packet i/o
 *
 *      After decapsulation, packet is going to re-enter (netif_rx()) our stack,
 *      so make some cleanups, and perform accounting.
 *      Note: this accounting is not SMP safe.
 */
static inline void skb_tunnel_rx(struct sk_buff *skb, struct net_device *dev,
                                 struct net *net)
{
        /* TODO : stats should be SMP safe */
        dev->stats.rx_packets++;
        dev->stats.rx_bytes += skb->len;
        __skb_tunnel_rx(skb, dev, net);
}

static inline u32 dst_tclassid(const struct sk_buff *skb)
{
#ifdef CONFIG_IP_ROUTE_CLASSID
        const struct dst_entry *dst;

        dst = skb_dst(skb);
        if (dst)
                return dst->tclassid;
#endif
        return 0;
}

int dst_discard_out(struct net *net, struct sock *sk, struct sk_buff *skb);
static inline int dst_discard(struct sk_buff *skb)
{
        return dst_discard_out(&init_net, skb->sk, skb);
}
void *dst_alloc(struct dst_ops *ops, struct net_device *dev, int initial_ref,
                int initial_obsolete, unsigned short flags);
void dst_init(struct dst_entry *dst, struct dst_ops *ops,
              struct net_device *dev, int initial_ref, int initial_obsolete,
              unsigned short flags);
struct dst_entry *dst_destroy(struct dst_entry *dst);
void dst_dev_put(struct dst_entry *dst);

static inline void dst_confirm(struct dst_entry *dst)
{
}

static inline struct neighbour *dst_neigh_lookup(const struct dst_entry *dst, const void *daddr)
{
        struct neighbour *n = dst->ops->neigh_lookup(dst, NULL, daddr);
        return IS_ERR(n) ? NULL : n;
}

static inline struct neighbour *dst_neigh_lookup_skb(const struct dst_entry *dst,
                                                     struct sk_buff *skb)
{
        struct neighbour *n =  dst->ops->neigh_lookup(dst, skb, NULL);
        return IS_ERR(n) ? NULL : n;
}

static inline void dst_confirm_neigh(const struct dst_entry *dst,
                                     const void *daddr)
{
        if (dst->ops->confirm_neigh)
                dst->ops->confirm_neigh(dst, daddr);
}

static inline void dst_link_failure(struct sk_buff *skb)
{
        struct dst_entry *dst = skb_dst(skb);
        if (dst && dst->ops && dst->ops->link_failure)
                dst->ops->link_failure(skb);
}

static inline void dst_set_expires(struct dst_entry *dst, int timeout)
{
        unsigned long expires = jiffies + timeout;

        if (expires == 0)
                expires = 1;

        if (dst->expires == 0 || time_before(expires, dst->expires))
                dst->expires = expires;
}

/* Output packet to network from transport.  */
static inline int dst_output(struct net *net, struct sock *sk, struct sk_buff *skb)
{
        return skb_dst(skb)->output(net, sk, skb);
}

/* Input packet from network to transport.  */
static inline int dst_input(struct sk_buff *skb)
{
        return skb_dst(skb)->input(skb);
}

static inline struct dst_entry *dst_check(struct dst_entry *dst, u32 cookie)
{
        if (dst->obsolete)
                dst = dst->ops->check(dst, cookie);
        return dst;
}

/* Flags for xfrm_lookup flags argument. */
enum {
        XFRM_LOOKUP_ICMP = 1 << 0,
        XFRM_LOOKUP_QUEUE = 1 << 1,
        XFRM_LOOKUP_KEEP_DST_REF = 1 << 2,
};

struct flowi;
#ifndef CONFIG_XFRM
static inline struct dst_entry *xfrm_lookup(struct net *net,
                                            struct dst_entry *dst_orig,
                                            const struct flowi *fl,
                                            const struct sock *sk,
                                            int flags)
{
        return dst_orig;
}

static inline struct dst_entry *
xfrm_lookup_with_ifid(struct net *net, struct dst_entry *dst_orig,
                      const struct flowi *fl, const struct sock *sk,
                      int flags, u32 if_id)
{
        return dst_orig;
}

static inline struct dst_entry *xfrm_lookup_route(struct net *net,
                                                  struct dst_entry *dst_orig,
                                                  const struct flowi *fl,
                                                  const struct sock *sk,
                                                  int flags)
{
        return dst_orig;
}

static inline struct xfrm_state *dst_xfrm(const struct dst_entry *dst)
{
        return NULL;
}

#else
struct dst_entry *xfrm_lookup(struct net *net, struct dst_entry *dst_orig,
                              const struct flowi *fl, const struct sock *sk,
                              int flags);

struct dst_entry *xfrm_lookup_with_ifid(struct net *net,
                                        struct dst_entry *dst_orig,
                                        const struct flowi *fl,
                                        const struct sock *sk, int flags,
                                        u32 if_id);

struct dst_entry *xfrm_lookup_route(struct net *net, struct dst_entry *dst_orig,
                                    const struct flowi *fl, const struct sock *sk,
                                    int flags);

/* skb attached with this dst needs transformation if dst->xfrm is valid */
static inline struct xfrm_state *dst_xfrm(const struct dst_entry *dst)
{
        return dst->xfrm;
}
#endif

static inline void skb_dst_update_pmtu(struct sk_buff *skb, u32 mtu)
{
        struct dst_entry *dst = skb_dst(skb);

        if (dst && dst->ops->update_pmtu)
                dst->ops->update_pmtu(dst, NULL, skb, mtu);
}

static inline void skb_tunnel_check_pmtu(struct sk_buff *skb,
                                         struct dst_entry *encap_dst,
                                         int headroom)
{
        u32 encap_mtu = dst_mtu(encap_dst);

        if (skb->len > encap_mtu - headroom)
                skb_dst_update_pmtu(skb, encap_mtu - headroom);
}

#endif /* _NET_DST_H */