dst.h

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/*
 * net/dst.h    Protocol independent destination cache definitions.
 *
 * Authors: Alexey Kuznetsov, <[email protected]>
 *
 */

#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 <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 rcu_head     rcu_head;
    struct dst_entry    *child;
    struct net_device       *dev;
    struct  dst_ops         *ops;
    unsigned long       _metrics;
    union {
        unsigned long           expires;
        /* point to where the dst_entry copied from */
        struct dst_entry        *from;
    };
    struct dst_entry    *path;
    void            *__pad0;
#ifdef CONFIG_XFRM
    struct xfrm_state   *xfrm;
#else
    void            *__pad1;
#endif
    int         (*input)(struct sk_buff *);
    int         (*output)(struct sk_buff *);

    unsigned short      flags;
#define DST_HOST        0x0001
#define DST_NOXFRM      0x0002
#define DST_NOPOLICY        0x0004
#define DST_NOHASH      0x0008
#define DST_NOCACHE     0x0010
#define DST_NOCOUNT     0x0020
#define DST_NOPEER      0x0040
#define DST_FAKE_RTABLE     0x0080
#define DST_XFRM_TUNNEL     0x0100

    unsigned short      pending_confirm;

    short           error;

    /* 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 */
#ifdef CONFIG_IP_ROUTE_CLASSID
    __u32           tclassid;
#else
    __u32           __pad2;
#endif

    /*
     * Align __refcnt to a 64 bytes alignment
     * (L1_CACHE_SIZE would be too much)
     */
#ifdef CONFIG_64BIT
    long            __pad_to_align_refcnt[2];
#endif
    /*
     * __refcnt wants to be on a different cache line from
     * input/output/ops or performance tanks badly
     */
    atomic_t        __refcnt;   /* client references    */
    int         __use;
    unsigned long       lastuse;
    union {
        struct dst_entry    *next;
        struct rtable __rcu *rt_next;
        struct rt6_info     *rt6_next;
        struct dn_route __rcu   *dn_next;
    };
};

extern u32 *dst_cow_metrics_generic(struct dst_entry *dst, unsigned long old);
extern const u32 dst_default_metrics[];

#define DST_METRICS_READ_ONLY   0x1UL
#define __DST_METRICS_PTR(Y)    \
    ((u32 *)((Y) & ~DST_METRICS_READ_ONLY))
#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;
}

extern 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;
}

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
     * __pad_to_align_refcnt declaration in struct dst_entry
     */
    BUILD_BUG_ON(offsetof(struct dst_entry, __refcnt) & 63);
    atomic_inc(&dst->__refcnt);
}

static inline void dst_use(struct dst_entry *dst, unsigned long time)
{
    dst_hold(dst);
    dst->__use++;
    dst->lastuse = time;
}

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

static inline struct dst_entry *dst_clone(struct dst_entry *dst)
{
    if (dst)
        atomic_inc(&dst->__refcnt);
    return dst;
}

extern void dst_release(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));
}

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, const struct sk_buff *oskb)
{
    nskb->_skb_refdst = oskb->_skb_refdst;
    if (!(nskb->_skb_refdst & SKB_DST_NOREF))
        dst_clone(skb_dst(nskb));
}

static inline void skb_dst_force(struct sk_buff *skb)
{
    if (skb_dst_is_noref(skb)) {
        WARN_ON(!rcu_read_lock_held());
        skb->_skb_refdst &= ~SKB_DST_NOREF;
        dst_clone(skb_dst(skb));
    }
}


static inline void __skb_tunnel_rx(struct sk_buff *skb, struct net_device *dev)
{
    skb->dev = dev;

    /*
     * Clear rxhash so that we can recalulate the hash for the
     * encapsulated packet, unless we have already determine the hash
     * over the L4 4-tuple.
     */
    if (!skb->l4_rxhash)
        skb->rxhash = 0;
    skb_set_queue_mapping(skb, 0);
    skb_dst_drop(skb);
    nf_reset(skb);
}

static inline void skb_tunnel_rx(struct sk_buff *skb, struct net_device *dev)
{
    /* TODO : stats should be SMP safe */
    dev->stats.rx_packets++;
    dev->stats.rx_bytes += skb->len;
    __skb_tunnel_rx(skb, dev);
}

/* Children define the path of the packet through the
 * Linux networking.  Thus, destinations are stackable.
 */

static inline struct dst_entry *skb_dst_pop(struct sk_buff *skb)
{
    struct dst_entry *child = dst_clone(skb_dst(skb)->child);

    skb_dst_drop(skb);
    return child;
}

extern int dst_discard(struct sk_buff *skb);
extern void *dst_alloc(struct dst_ops *ops, struct net_device *dev,
               int initial_ref, int initial_obsolete,
               unsigned short flags);
extern void __dst_free(struct dst_entry *dst);
extern struct dst_entry *dst_destroy(struct dst_entry *dst);

static inline void dst_free(struct dst_entry *dst)
{
    if (dst->obsolete > 0)
        return;
    if (!atomic_read(&dst->__refcnt)) {
        dst = dst_destroy(dst);
        if (!dst)
            return;
    }
    __dst_free(dst);
}

static inline void dst_rcu_free(struct rcu_head *head)
{
    struct dst_entry *dst = container_of(head, struct dst_entry, rcu_head);
    dst_free(dst);
}

static inline void dst_confirm(struct dst_entry *dst)
{
    dst->pending_confirm = 1;
}

static inline int dst_neigh_output(struct dst_entry *dst, struct neighbour *n,
                   struct sk_buff *skb)
{
    const struct hh_cache *hh;

    if (dst->pending_confirm) {
        unsigned long now = jiffies;

        dst->pending_confirm = 0;
        /* avoid dirtying neighbour */
        if (n->confirmed != now)
            n->confirmed = now;
    }

    hh = &n->hh;
    if ((n->nud_state & NUD_CONNECTED) && hh->hh_len)
        return neigh_hh_output(hh, skb);
    else
        return n->output(n, skb);
}

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

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

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 sk_buff *skb)
{
    return skb_dst(skb)->output(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;
}

extern void     dst_init(void);

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

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

#endif /* _NET_DST_H */