linux/include/net/inetpeer.h

/*
 *		INETPEER - A storage for permanent information about peers
 *
 *  Authors:	Andrey V. Savochkin <saw@msu.ru>
 */

#ifndef _NET_INETPEER_H
#define _NET_INETPEER_H

#include <linux/types.h>
#include <linux/init.h>
#include <linux/jiffies.h>
#include <linux/spinlock.h>
#include <linux/rtnetlink.h>
#include <net/ipv6.h>
#include <asm/atomic.h>

struct inetpeer_addr_base {
	union {
		__be32			a4;
		__be32			a6[4];
	};
};

struct inetpeer_addr {
	struct inetpeer_addr_base	addr;
	__u16				family;
};

struct inet_peer {
	/* group together avl_left,avl_right,v4daddr to speedup lookups */
	struct inet_peer __rcu	*avl_left, *avl_right;
	struct inetpeer_addr	daddr;
	__u32			avl_height;
	struct list_head	unused;
	__u32			dtime;		/* the time of last use of not
						 * referenced entries */
	atomic_t		refcnt;
	/*
	 * Once inet_peer is queued for deletion (refcnt == -1), following fields
	 * are not available: rid, ip_id_count, tcp_ts, tcp_ts_stamp, metrics
	 * We can share memory with rcu_head to help keep inet_peer small.
	 */
	union {
		struct {
			atomic_t			rid;		/* Frag reception counter */
			atomic_t			ip_id_count;	/* IP ID for the next packet */
			__u32				tcp_ts;
			__u32				tcp_ts_stamp;
			u32				metrics[RTAX_MAX];
			u32				rate_tokens;	/* rate limiting for ICMP */
			unsigned long			rate_last;
			unsigned long			pmtu_expires;
			u32				pmtu_orig;
			u32				pmtu_learned;
			struct inetpeer_addr_base	redirect_learned;
		};
		struct rcu_head         rcu;
	};
};

void			inet_initpeers(void) __init;

#define INETPEER_METRICS_NEW	(~(u32) 0)

static inline bool inet_metrics_new(const struct inet_peer *p)
{
	return p->metrics[RTAX_LOCK-1] == INETPEER_METRICS_NEW;
}

/* can be called with or without local BH being disabled */
struct inet_peer	*inet_getpeer(struct inetpeer_addr *daddr, int create);

static inline struct inet_peer *inet_getpeer_v4(__be32 v4daddr, int create)
{
	struct inetpeer_addr daddr;

	daddr.addr.a4 = v4daddr;
	daddr.family = AF_INET;
	return inet_getpeer(&daddr, create);
}

static inline struct inet_peer *inet_getpeer_v6(const struct in6_addr *v6daddr, int create)
{
	struct inetpeer_addr daddr;

	ipv6_addr_copy((struct in6_addr *)daddr.addr.a6, v6daddr);
	daddr.family = AF_INET6;
	return inet_getpeer(&daddr, create);
}

/* can be called from BH context or outside */
extern void inet_putpeer(struct inet_peer *p);
extern bool inet_peer_xrlim_allow(struct inet_peer *peer, int timeout);

/*
 * temporary check to make sure we dont access rid, ip_id_count, tcp_ts,
 * tcp_ts_stamp if no refcount is taken on inet_peer
 */
static inline void inet_peer_refcheck(const struct inet_peer *p)
{
	WARN_ON_ONCE(atomic_read(&p->refcnt) <= 0);
}


/* can be called with or without local BH being disabled */
static inline __u16	inet_getid(struct inet_peer *p, int more)
{
	more++;
	inet_peer_refcheck(p);
	return atomic_add_return(more, &p->ip_id_count) - more;
}

#endif /* _NET_INETPEER_H */