net/netfilter/ipvs/ip_vs_conn.c

/*
 * IPVS         An implementation of the IP virtual server support for the
 *              LINUX operating system.  IPVS is now implemented as a module
 *              over the Netfilter framework. IPVS can be used to build a
 *              high-performance and highly available server based on a
 *              cluster of servers.
 *
 * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
 *              Peter Kese <peter.kese@ijs.si>
 *              Julian Anastasov <ja@ssi.bg>
 *
 *              This program is free software; you can redistribute it and/or
 *              modify it under the terms of the GNU General Public License
 *              as published by the Free Software Foundation; either version
 *              2 of the License, or (at your option) any later version.
 *
 * The IPVS code for kernel 2.2 was done by Wensong Zhang and Peter Kese,
 * with changes/fixes from Julian Anastasov, Lars Marowsky-Bree, Horms
 * and others. Many code here is taken from IP MASQ code of kernel 2.2.
 *
 * Changes:
 *
 */

#define KMSG_COMPONENT "IPVS"
#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt

#include <linux/interrupt.h>
#include <linux/in.h>
#include <linux/net.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/vmalloc.h>
#include <linux/proc_fs.h>		/* for proc_net_* */
#include <linux/slab.h>
#include <linux/seq_file.h>
#include <linux/jhash.h>
#include <linux/random.h>

#include <net/net_namespace.h>
#include <net/ip_vs.h>


#ifndef CONFIG_IP_VS_TAB_BITS
#define CONFIG_IP_VS_TAB_BITS	12
#endif

/*
 * Connection hash size. Default is what was selected at compile time.
*/
int ip_vs_conn_tab_bits = CONFIG_IP_VS_TAB_BITS;
module_param_named(conn_tab_bits, ip_vs_conn_tab_bits, int, 0444);
MODULE_PARM_DESC(conn_tab_bits, "Set connections' hash size");

/* size and mask values */
int ip_vs_conn_tab_size;
int ip_vs_conn_tab_mask;

/*
 *  Connection hash table: for input and output packets lookups of IPVS
 */
static struct list_head *ip_vs_conn_tab;

/*  SLAB cache for IPVS connections */
static struct kmem_cache *ip_vs_conn_cachep __read_mostly;

/*  counter for current IPVS connections */
static atomic_t ip_vs_conn_count = ATOMIC_INIT(0);

/*  counter for no client port connections */
static atomic_t ip_vs_conn_no_cport_cnt = ATOMIC_INIT(0);

/* random value for IPVS connection hash */
static unsigned int ip_vs_conn_rnd;

/*
 *  Fine locking granularity for big connection hash table
 */
#define CT_LOCKARRAY_BITS  4
#define CT_LOCKARRAY_SIZE  (1<<CT_LOCKARRAY_BITS)
#define CT_LOCKARRAY_MASK  (CT_LOCKARRAY_SIZE-1)

struct ip_vs_aligned_lock
{
	rwlock_t	l;
} __attribute__((__aligned__(SMP_CACHE_BYTES)));

/* lock array for conn table */
static struct ip_vs_aligned_lock
__ip_vs_conntbl_lock_array[CT_LOCKARRAY_SIZE] __cacheline_aligned;

static inline void ct_read_lock(unsigned key)
{
	read_lock(&__ip_vs_conntbl_lock_array[key&CT_LOCKARRAY_MASK].l);
}

static inline void ct_read_unlock(unsigned key)
{
	read_unlock(&__ip_vs_conntbl_lock_array[key&CT_LOCKARRAY_MASK].l);
}

static inline void ct_write_lock(unsigned key)
{
	write_lock(&__ip_vs_conntbl_lock_array[key&CT_LOCKARRAY_MASK].l);
}

static inline void ct_write_unlock(unsigned key)
{
	write_unlock(&__ip_vs_conntbl_lock_array[key&CT_LOCKARRAY_MASK].l);
}

static inline void ct_read_lock_bh(unsigned key)
{
	read_lock_bh(&__ip_vs_conntbl_lock_array[key&CT_LOCKARRAY_MASK].l);
}

static inline void ct_read_unlock_bh(unsigned key)
{
	read_unlock_bh(&__ip_vs_conntbl_lock_array[key&CT_LOCKARRAY_MASK].l);
}

static inline void ct_write_lock_bh(unsigned key)
{
	write_lock_bh(&__ip_vs_conntbl_lock_array[key&CT_LOCKARRAY_MASK].l);
}

static inline void ct_write_unlock_bh(unsigned key)
{
	write_unlock_bh(&__ip_vs_conntbl_lock_array[key&CT_LOCKARRAY_MASK].l);
}


/*
 *	Returns hash value for IPVS connection entry
 */
static unsigned int ip_vs_conn_hashkey(int af, unsigned proto,
				       const union nf_inet_addr *addr,
				       __be16 port)
{
#ifdef CONFIG_IP_VS_IPV6
	if (af == AF_INET6)
		return jhash_3words(jhash(addr, 16, ip_vs_conn_rnd),
				    (__force u32)port, proto, ip_vs_conn_rnd)
			& ip_vs_conn_tab_mask;
#endif
	return jhash_3words((__force u32)addr->ip, (__force u32)port, proto,
			    ip_vs_conn_rnd)
		& ip_vs_conn_tab_mask;
}


/*
 *	Hashes ip_vs_conn in ip_vs_conn_tab by proto,addr,port.
 *	returns bool success.
 */
static inline int ip_vs_conn_hash(struct ip_vs_conn *cp)
{
	unsigned hash;
	int ret;

	if (cp->flags & IP_VS_CONN_F_ONE_PACKET)
		return 0;

	/* Hash by protocol, client address and port */
	hash = ip_vs_conn_hashkey(cp->af, cp->protocol, &cp->caddr, cp->cport);

	ct_write_lock(hash);
	spin_lock(&cp->lock);

	if (!(cp->flags & IP_VS_CONN_F_HASHED)) {
		list_add(&cp->c_list, &ip_vs_conn_tab[hash]);
		cp->flags |= IP_VS_CONN_F_HASHED;
		atomic_inc(&cp->refcnt);
		ret = 1;
	} else {
		pr_err("%s(): request for already hashed, called from %pF\n",
		       __func__, __builtin_return_address(0));
		ret = 0;
	}

	spin_unlock(&cp->lock);
	ct_write_unlock(hash);

	return ret;
}


/*
 *	UNhashes ip_vs_conn from ip_vs_conn_tab.
 *	returns bool success.
 */
static inline int ip_vs_conn_unhash(struct ip_vs_conn *cp)
{
	unsigned hash;
	int ret;

	/* unhash it and decrease its reference counter */
	hash = ip_vs_conn_hashkey(cp->af, cp->protocol, &cp->caddr, cp->cport);

	ct_write_lock(hash);
	spin_lock(&cp->lock);

	if (cp->flags & IP_VS_CONN_F_HASHED) {
		list_del(&cp->c_list);
		cp->flags &= ~IP_VS_CONN_F_HASHED;
		atomic_dec(&cp->refcnt);
		ret = 1;
	} else
		ret = 0;

	spin_unlock(&cp->lock);
	ct_write_unlock(hash);

	return ret;
}


/*
 *  Gets ip_vs_conn associated with supplied parameters in the ip_vs_conn_tab.
 *  Called for pkts coming from OUTside-to-INside.
 *	p->caddr, p->cport: pkt source address (foreign host)
 *	p->vaddr, p->vport: pkt dest address (load balancer)
 */
static inline struct ip_vs_conn *
__ip_vs_conn_in_get(const struct ip_vs_conn_param *p)
{
	unsigned hash;
	struct ip_vs_conn *cp;

	hash = ip_vs_conn_hashkey(p->af, p->protocol, p->caddr, p->cport);

	ct_read_lock(hash);

	list_for_each_entry(cp, &ip_vs_conn_tab[hash], c_list) {
		if (cp->af == p->af &&
		    ip_vs_addr_equal(p->af, p->caddr, &cp->caddr) &&
		    ip_vs_addr_equal(p->af, p->vaddr, &cp->vaddr) &&
		    p->cport == cp->cport && p->vport == cp->vport &&
		    ((!p->cport) ^ (!(cp->flags & IP_VS_CONN_F_NO_CPORT))) &&
		    p->protocol == cp->protocol) {
			/* HIT */
			atomic_inc(&cp->refcnt);
			ct_read_unlock(hash);
			return cp;
		}
	}

	ct_read_unlock(hash);

	return NULL;
}

struct ip_vs_conn *ip_vs_conn_in_get(const struct ip_vs_conn_param *p)
{
	struct ip_vs_conn *cp;

	cp = __ip_vs_conn_in_get(p);
	if (!cp && atomic_read(&ip_vs_conn_no_cport_cnt)) {
		struct ip_vs_conn_param cport_zero_p = *p;
		cport_zero_p.cport = 0;
		cp = __ip_vs_conn_in_get(&cport_zero_p);
	}

	IP_VS_DBG_BUF(9, "lookup/in %s %s:%d->%s:%d %s\n",
		      ip_vs_proto_name(p->protocol),
		      IP_VS_DBG_ADDR(p->af, p->caddr), ntohs(p->cport),
		      IP_VS_DBG_ADDR(p->af, p->vaddr), ntohs(p->vport),
		      cp ? "hit" : "not hit");

	return cp;
}

static int
ip_vs_conn_fill_param_proto(int af, const struct sk_buff *skb,
			    const struct ip_vs_iphdr *iph,
			    unsigned int proto_off, int inverse,
			    struct ip_vs_conn_param *p)
{
	__be16 _ports[2], *pptr;

	pptr = skb_header_pointer(skb, proto_off, sizeof(_ports), _ports);
	if (pptr == NULL)
		return 1;

	if (likely(!inverse))
		ip_vs_conn_fill_param(af, iph->protocol, &iph->saddr, pptr[0],
				      &iph->daddr, pptr[1], p);
	else
		ip_vs_conn_fill_param(af, iph->protocol, &iph->daddr, pptr[1],
				      &iph->saddr, pptr[0], p);
	return 0;
}

struct ip_vs_conn *
ip_vs_conn_in_get_proto(int af, const struct sk_buff *skb,
			struct ip_vs_protocol *pp,
			const struct ip_vs_iphdr *iph,
			unsigned int proto_off, int inverse)
{
	struct ip_vs_conn_param p;

	if (ip_vs_conn_fill_param_proto(af, skb, iph, proto_off, inverse, &p))
		return NULL;

	return ip_vs_conn_in_get(&p);
}
EXPORT_SYMBOL_GPL(ip_vs_conn_in_get_proto);

/* Get reference to connection template */
struct ip_vs_conn *ip_vs_ct_in_get(const struct ip_vs_conn_param *p)
{
	unsigned hash;
	struct ip_vs_conn *cp;

	hash = ip_vs_conn_hashkey(p->af, p->protocol, p->caddr, p->cport);

	ct_read_lock(hash);

	list_for_each_entry(cp, &ip_vs_conn_tab[hash], c_list) {
		if (cp->af == p->af &&
		    ip_vs_addr_equal(p->af, p->caddr, &cp->caddr) &&
		    /* protocol should only be IPPROTO_IP if
		     * p->vaddr is a fwmark */
		    ip_vs_addr_equal(p->protocol == IPPROTO_IP ? AF_UNSPEC :
				     p->af, p->vaddr, &cp->vaddr) &&
		    p->cport == cp->cport && p->vport == cp->vport &&
		    cp->flags & IP_VS_CONN_F_TEMPLATE &&
		    p->protocol == cp->protocol) {
			/* HIT */
			atomic_inc(&cp->refcnt);
			goto out;
		}
	}
	cp = NULL;

  out:
	ct_read_unlock(hash);

	IP_VS_DBG_BUF(9, "template lookup/in %s %s:%d->%s:%d %s\n",
		      ip_vs_proto_name(p->protocol),
		      IP_VS_DBG_ADDR(p->af, p->caddr), ntohs(p->cport),
		      IP_VS_DBG_ADDR(p->af, p->vaddr), ntohs(p->vport),
		      cp ? "hit" : "not hit");

	return cp;
}

/* Gets ip_vs_conn associated with supplied parameters in the ip_vs_conn_tab.
 * Called for pkts coming from inside-to-OUTside.
 *	p->caddr, p->cport: pkt source address (inside host)
 *	p->vaddr, p->vport: pkt dest address (foreign host) */
struct ip_vs_conn *ip_vs_conn_out_get(const struct ip_vs_conn_param *p)
{
	unsigned hash;
	struct ip_vs_conn *cp, *ret=NULL;

	/*
	 *	Check for "full" addressed entries
	 */
	hash = ip_vs_conn_hashkey(p->af, p->protocol, p->vaddr, p->vport);

	ct_read_lock(hash);

	list_for_each_entry(cp, &ip_vs_conn_tab[hash], c_list) {
		if (cp->af == p->af &&
		    ip_vs_addr_equal(p->af, p->vaddr, &cp->caddr) &&
		    ip_vs_addr_equal(p->af, p->caddr, &cp->daddr) &&
		    p->vport == cp->cport && p->cport == cp->dport &&
		    p->protocol == cp->protocol) {
			/* HIT */
			atomic_inc(&cp->refcnt);
			ret = cp;
			break;
		}
	}

	ct_read_unlock(hash);

	IP_VS_DBG_BUF(9, "lookup/out %s %s:%d->%s:%d %s\n",
		      ip_vs_proto_name(p->protocol),
		      IP_VS_DBG_ADDR(p->af, p->caddr), ntohs(p->cport),
		      IP_VS_DBG_ADDR(p->af, p->vaddr), ntohs(p->vport),
		      ret ? "hit" : "not hit");

	return ret;
}

struct ip_vs_conn *
ip_vs_conn_out_get_proto(int af, const struct sk_buff *skb,
			 struct ip_vs_protocol *pp,
			 const struct ip_vs_iphdr *iph,
			 unsigned int proto_off, int inverse)
{
	struct ip_vs_conn_param p;

	if (ip_vs_conn_fill_param_proto(af, skb, iph, proto_off, inverse, &p))
		return NULL;

	return ip_vs_conn_out_get(&p);
}
EXPORT_SYMBOL_GPL(ip_vs_conn_out_get_proto);

/*
 *      Put back the conn and restart its timer with its timeout
 */
void ip_vs_conn_put(struct ip_vs_conn *cp)
{
	unsigned long t = (cp->flags & IP_VS_CONN_F_ONE_PACKET) ?
		0 : cp->timeout;
	mod_timer(&cp->timer, jiffies+t);

	__ip_vs_conn_put(cp);
}


/*
 *	Fill a no_client_port connection with a client port number
 */
void ip_vs_conn_fill_cport(struct ip_vs_conn *cp, __be16 cport)
{
	if (ip_vs_conn_unhash(cp)) {
		spin_lock(&cp->lock);
		if (cp->flags & IP_VS_CONN_F_NO_CPORT) {
			atomic_dec(&ip_vs_conn_no_cport_cnt);
			cp->flags &= ~IP_VS_CONN_F_NO_CPORT;
			cp->cport = cport;
		}
		spin_unlock(&cp->lock);

		/* hash on new dport */
		ip_vs_conn_hash(cp);
	}
}


/*
 *	Bind a connection entry with the corresponding packet_xmit.
 *	Called by ip_vs_conn_new.
 */
static inline void ip_vs_bind_xmit(struct ip_vs_conn *cp)
{
	switch (IP_VS_FWD_METHOD(cp)) {
	case IP_VS_CONN_F_MASQ:
		cp->packet_xmit = ip_vs_nat_xmit;
		break;

	case IP_VS_CONN_F_TUNNEL:
		cp->packet_xmit = ip_vs_tunnel_xmit;
		break;

	case IP_VS_CONN_F_DROUTE:
		cp->packet_xmit = ip_vs_dr_xmit;
		break;

	case IP_VS_CONN_F_LOCALNODE:
		cp->packet_xmit = ip_vs_null_xmit;
		break;

	case IP_VS_CONN_F_BYPASS:
		cp->packet_xmit = ip_vs_bypass_xmit;
		break;
	}
}

#ifdef CONFIG_IP_VS_IPV6
static inline void ip_vs_bind_xmit_v6(struct ip_vs_conn *cp)
{
	switch (IP_VS_FWD_METHOD(cp)) {
	case IP_VS_CONN_F_MASQ:
		cp->packet_xmit = ip_vs_nat_xmit_v6;
		break;

	case IP_VS_CONN_F_TUNNEL:
		cp->packet_xmit = ip_vs_tunnel_xmit_v6;
		break;

	case IP_VS_CONN_F_DROUTE:
		cp->packet_xmit = ip_vs_dr_xmit_v6;
		break;

	case IP_VS_CONN_F_LOCALNODE:
		cp->packet_xmit = ip_vs_null_xmit;
		break;

	case IP_VS_CONN_F_BYPASS:
		cp->packet_xmit = ip_vs_bypass_xmit_v6;
		break;
	}
}
#endif


static inline int ip_vs_dest_totalconns(struct ip_vs_dest *dest)
{
	return atomic_read(&dest->activeconns)
		+ atomic_read(&dest->inactconns);
}

/*
 *	Bind a connection entry with a virtual service destination
 *	Called just after a new connection entry is created.
 */
static inline void
ip_vs_bind_dest(struct ip_vs_conn *cp, struct ip_vs_dest *dest)
{
	unsigned int conn_flags;

	/* if dest is NULL, then return directly */
	if (!dest)
		return;

	/* Increase the refcnt counter of the dest */
	atomic_inc(&dest->refcnt);

	conn_flags = atomic_read(&dest->conn_flags);
	if (cp->protocol != IPPROTO_UDP)
		conn_flags &= ~IP_VS_CONN_F_ONE_PACKET;
	/* Bind with the destination and its corresponding transmitter */
	if (cp->flags & IP_VS_CONN_F_SYNC) {
		/* if the connection is not template and is created
		 * by sync, preserve the activity flag.
		 */
		if (!(cp->flags & IP_VS_CONN_F_TEMPLATE))
			conn_flags &= ~IP_VS_CONN_F_INACTIVE;
	}
	cp->flags |= conn_flags;
	cp->dest = dest;

	IP_VS_DBG_BUF(7, "Bind-dest %s c:%s:%d v:%s:%d "
		      "d:%s:%d fwd:%c s:%u conn->flags:%X conn->refcnt:%d "
		      "dest->refcnt:%d\n",
		      ip_vs_proto_name(cp->protocol),
		      IP_VS_DBG_ADDR(cp->af, &cp->caddr), ntohs(cp->cport),
		      IP_VS_DBG_ADDR(cp->af, &cp->vaddr), ntohs(cp->vport),
		      IP_VS_DBG_ADDR(cp->af, &cp->daddr), ntohs(cp->dport),
		      ip_vs_fwd_tag(cp), cp->state,
		      cp->flags, atomic_read(&cp->refcnt),
		      atomic_read(&dest->refcnt));

	/* Update the connection counters */
	if (!(cp->flags & IP_VS_CONN_F_TEMPLATE)) {
		/* It is a normal connection, so increase the inactive
		   connection counter because it is in TCP SYNRECV
		   state (inactive) or other protocol inacive state */
		if ((cp->flags & IP_VS_CONN_F_SYNC) &&
		    (!(cp->flags & IP_VS_CONN_F_INACTIVE)))
			atomic_inc(&dest->activeconns);
		else
			atomic_inc(&dest->inactconns);
	} else {
		/* It is a persistent connection/template, so increase
		   the peristent connection counter */
		atomic_inc(&dest->persistconns);
	}

	if (dest->u_threshold != 0 &&
	    ip_vs_dest_totalconns(dest) >= dest->u_threshold)
		dest->flags |= IP_VS_DEST_F_OVERLOAD;
}


/*
 * Check if there is a destination for the connection, if so
 * bind the connection to the destination.
 */
struct ip_vs_dest *ip_vs_try_bind_dest(struct ip_vs_conn *cp)
{
	struct ip_vs_dest *dest;

	if ((cp) && (!cp->dest)) {
		dest = ip_vs_find_dest(cp->af, &cp->daddr, cp->dport,
				       &cp->vaddr, cp->vport,
				       cp->protocol);
		ip_vs_bind_dest(cp, dest);
		return dest;
	} else
		return NULL;
}


/*
 *	Unbind a connection entry with its VS destination
 *	Called by the ip_vs_conn_expire function.
 */
static inline void ip_vs_unbind_dest(struct ip_vs_conn *cp)
{
	struct ip_vs_dest *dest = cp->dest;

	if (!dest)
		return;

	IP_VS_DBG_BUF(7, "Unbind-dest %s c:%s:%d v:%s:%d "
		      "d:%s:%d fwd:%c s:%u conn->flags:%X conn->refcnt:%d "
		      "dest->refcnt:%d\n",
		      ip_vs_proto_name(cp->protocol),
		      IP_VS_DBG_ADDR(cp->af, &cp->caddr), ntohs(cp->cport),
		      IP_VS_DBG_ADDR(cp->af, &cp->vaddr), ntohs(cp->vport),
		      IP_VS_DBG_ADDR(cp->af, &cp->daddr), ntohs(cp->dport),
		      ip_vs_fwd_tag(cp), cp->state,
		      cp->flags, atomic_read(&cp->refcnt),
		      atomic_read(&dest->refcnt));

	/* Update the connection counters */
	if (!(cp->flags & IP_VS_CONN_F_TEMPLATE)) {
		/* It is a normal connection, so decrease the inactconns
		   or activeconns counter */
		if (cp->flags & IP_VS_CONN_F_INACTIVE) {
			atomic_dec(&dest->inactconns);
		} else {
			atomic_dec(&dest->activeconns);
		}
	} else {
		/* It is a persistent connection/template, so decrease
		   the peristent connection counter */
		atomic_dec(&dest->persistconns);
	}

	if (dest->l_threshold != 0) {
		if (ip_vs_dest_totalconns(dest) < dest->l_threshold)
			dest->flags &= ~IP_VS_DEST_F_OVERLOAD;
	} else if (dest->u_threshold != 0) {
		if (ip_vs_dest_totalconns(dest) * 4 < dest->u_threshold * 3)
			dest->flags &= ~IP_VS_DEST_F_OVERLOAD;
	} else {
		if (dest->flags & IP_VS_DEST_F_OVERLOAD)
			dest->flags &= ~IP_VS_DEST_F_OVERLOAD;
	}

	/*
	 * Simply decrease the refcnt of the dest, because the
	 * dest will be either in service's destination list
	 * or in the trash.
	 */
	atomic_dec(&dest->refcnt);
}


/*
 *	Checking if the destination of a connection template is available.
 *	If available, return 1, otherwise invalidate this connection
 *	template and return 0.
 */
int ip_vs_check_template(struct ip_vs_conn *ct)
{
	struct ip_vs_dest *dest = ct->dest;

	/*
	 * Checking the dest server status.
	 */
	if ((dest == NULL) ||
	    !(dest->flags & IP_VS_DEST_F_AVAILABLE) ||
	    (sysctl_ip_vs_expire_quiescent_template &&
	     (atomic_read(&dest->weight) == 0))) {
		IP_VS_DBG_BUF(9, "check_template: dest not available for "
			      "protocol %s s:%s:%d v:%s:%d "
			      "-> d:%s:%d\n",
			      ip_vs_proto_name(ct->protocol),
			      IP_VS_DBG_ADDR(ct->af, &ct->caddr),
			      ntohs(ct->cport),
			      IP_VS_DBG_ADDR(ct->af, &ct->vaddr),
			      ntohs(ct->vport),
			      IP_VS_DBG_ADDR(ct->af, &ct->daddr),
			      ntohs(ct->dport));

		/*
		 * Invalidate the connection template
		 */
		if (ct->vport != htons(0xffff)) {
			if (ip_vs_conn_unhash(ct)) {
				ct->dport = htons(0xffff);
				ct->vport = htons(0xffff);
				ct->cport = 0;
				ip_vs_conn_hash(ct);
			}
		}

		/*
		 * Simply decrease the refcnt of the template,
		 * don't restart its timer.
		 */
		atomic_dec(&ct->refcnt);
		return 0;
	}
	return 1;
}

static void ip_vs_conn_expire(unsigned long data)
{
	struct ip_vs_conn *cp = (struct ip_vs_conn *)data;

	cp->timeout = 60*HZ;

	/*
	 *	hey, I'm using it
	 */
	atomic_inc(&cp->refcnt);

	/*
	 *	do I control anybody?
	 */
	if (atomic_read(&cp->n_control))
		goto expire_later;

	/*
	 *	unhash it if it is hashed in the conn table
	 */
	if (!ip_vs_conn_unhash(cp) && !(cp->flags & IP_VS_CONN_F_ONE_PACKET))
		goto expire_later;

	/*
	 *	refcnt==1 implies I'm the only one referrer
	 */
	if (likely(atomic_read(&cp->refcnt) == 1)) {
		/* delete the timer if it is activated by other users */
		if (timer_pending(&cp->timer))
			del_timer(&cp->timer);

		/* does anybody control me? */
		if (cp->control)
			ip_vs_control_del(cp);

		if (cp->flags & IP_VS_CONN_F_NFCT)
			ip_vs_conn_drop_conntrack(cp);

		if (unlikely(cp->app != NULL))
			ip_vs_unbind_app(cp);
		ip_vs_unbind_dest(cp);
		if (cp->flags & IP_VS_CONN_F_NO_CPORT)
			atomic_dec(&ip_vs_conn_no_cport_cnt);
		atomic_dec(&ip_vs_conn_count);

		kmem_cache_free(ip_vs_conn_cachep, cp);
		return;
	}

	/* hash it back to the table */
	ip_vs_conn_hash(cp);

  expire_later:
	IP_VS_DBG(7, "delayed: conn->refcnt-1=%d conn->n_control=%d\n",
		  atomic_read(&cp->refcnt)-1,
		  atomic_read(&cp->n_control));

	ip_vs_conn_put(cp);
}


void ip_vs_conn_expire_now(struct ip_vs_conn *cp)
{
	if (del_timer(&cp->timer))
		mod_timer(&cp->timer, jiffies);
}


/*
 *	Create a new connection entry and hash it into the ip_vs_conn_tab
 */
struct ip_vs_conn *
ip_vs_conn_new(const struct ip_vs_conn_param *p,
	       const union nf_inet_addr *daddr, __be16 dport, unsigned flags,
	       struct ip_vs_dest *dest)
{
	struct ip_vs_conn *cp;
	struct ip_vs_protocol *pp = ip_vs_proto_get(p->protocol);

	cp = kmem_cache_zalloc(ip_vs_conn_cachep, GFP_ATOMIC);
	if (cp == NULL) {
		IP_VS_ERR_RL("%s(): no memory\n", __func__);
		return NULL;
	}

	INIT_LIST_HEAD(&cp->c_list);
	setup_timer(&cp->timer, ip_vs_conn_expire, (unsigned long)cp);
	cp->af		   = p->af;
	cp->protocol	   = p->protocol;
	ip_vs_addr_copy(p->af, &cp->caddr, p->caddr);
	cp->cport	   = p->cport;
	ip_vs_addr_copy(p->af, &cp->vaddr, p->vaddr);
	cp->vport	   = p->vport;
	/* proto should only be IPPROTO_IP if d_addr is a fwmark */
	ip_vs_addr_copy(p->protocol == IPPROTO_IP ? AF_UNSPEC : p->af,
			&cp->daddr, daddr);
	cp->dport          = dport;
	cp->flags	   = flags;
	spin_lock_init(&cp->lock);

	/*
	 * Set the entry is referenced by the current thread before hashing
	 * it in the table, so that other thread run ip_vs_random_dropentry
	 * but cannot drop this entry.
	 */
	atomic_set(&cp->refcnt, 1);

	atomic_set(&cp->n_control, 0);
	atomic_set(&cp->in_pkts, 0);

	atomic_inc(&ip_vs_conn_count);
	if (flags & IP_VS_CONN_F_NO_CPORT)
		atomic_inc(&ip_vs_conn_no_cport_cnt);

	/* Bind the connection with a destination server */
	ip_vs_bind_dest(cp, dest);

	/* Set its state and timeout */
	cp->state = 0;
	cp->timeout = 3*HZ;

	/* Bind its packet transmitter */
#ifdef CONFIG_IP_VS_IPV6
	if (p->af == AF_INET6)
		ip_vs_bind_xmit_v6(cp);
	else
#endif
		ip_vs_bind_xmit(cp);

	if (unlikely(pp && atomic_read(&pp->appcnt)))
		ip_vs_bind_app(cp, pp);

	/*
	 * Allow conntrack to be preserved. By default, conntrack
	 * is created and destroyed for every packet.
	 * Sometimes keeping conntrack can be useful for
	 * IP_VS_CONN_F_ONE_PACKET too.
	 */

	if (ip_vs_conntrack_enabled())
		cp->flags |= IP_VS_CONN_F_NFCT;

	/* Hash it in the ip_vs_conn_tab finally */
	ip_vs_conn_hash(cp);

	return cp;
}


/*
 *	/proc/net/ip_vs_conn entries
 */
#ifdef CONFIG_PROC_FS

static void *ip_vs_conn_array(struct seq_file *seq, loff_t pos)
{
	int idx;
	struct ip_vs_conn *cp;

	for (idx = 0; idx < ip_vs_conn_tab_size; idx++) {
		ct_read_lock_bh(idx);
		list_for_each_entry(cp, &ip_vs_conn_tab[idx], c_list) {
			if (pos-- == 0) {
				seq->private = &ip_vs_conn_tab[idx];
				return cp;
			}
		}
		ct_read_unlock_bh(idx);
	}

	return NULL;
}

static void *ip_vs_conn_seq_start(struct seq_file *seq, loff_t *pos)
{
	seq->private = NULL;
	return *pos ? ip_vs_conn_array(seq, *pos - 1) :SEQ_START_TOKEN;
}

static void *ip_vs_conn_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
	struct ip_vs_conn *cp = v;
	struct list_head *e, *l = seq->private;
	int idx;

	++*pos;
	if (v == SEQ_START_TOKEN)
		return ip_vs_conn_array(seq, 0);

	/* more on same hash chain? */
	if ((e = cp->c_list.next) != l)
		return list_entry(e, struct ip_vs_conn, c_list);

	idx = l - ip_vs_conn_tab;
	ct_read_unlock_bh(idx);

	while (++idx < ip_vs_conn_tab_size) {
		ct_read_lock_bh(idx);
		list_for_each_entry(cp, &ip_vs_conn_tab[idx], c_list) {
			seq->private = &ip_vs_conn_tab[idx];
			return cp;
		}
		ct_read_unlock_bh(idx);
	}
	seq->private = NULL;
	return NULL;
}

static void ip_vs_conn_seq_stop(struct seq_file *seq, void *v)
{
	struct list_head *l = seq->private;

	if (l)
		ct_read_unlock_bh(l - ip_vs_conn_tab);
}

static int ip_vs_conn_seq_show(struct seq_file *seq, void *v)
{

	if (v == SEQ_START_TOKEN)
		seq_puts(seq,
   "Pro FromIP   FPrt ToIP     TPrt DestIP   DPrt State       Expires\n");
	else {
		const struct ip_vs_conn *cp = v;

#ifdef CONFIG_IP_VS_IPV6
		if (cp->af == AF_INET6)
			seq_printf(seq, "%-3s %pI6 %04X %pI6 %04X %pI6 %04X %-11s %7lu\n",
				ip_vs_proto_name(cp->protocol),
				&cp->caddr.in6, ntohs(cp->cport),
				&cp->vaddr.in6, ntohs(cp->vport),
				&cp->daddr.in6, ntohs(cp->dport),
				ip_vs_state_name(cp->protocol, cp->state),
				(cp->timer.expires-jiffies)/HZ);
		else
#endif
			seq_printf(seq,
				"%-3s %08X %04X %08X %04X"
				" %08X %04X %-11s %7lu\n",
				ip_vs_proto_name(cp->protocol),
				ntohl(cp->caddr.ip), ntohs(cp->cport),
				ntohl(cp->vaddr.ip), ntohs(cp->vport),
				ntohl(cp->daddr.ip), ntohs(cp->dport),
				ip_vs_state_name(cp->protocol, cp->state),
				(cp->timer.expires-jiffies)/HZ);
	}
	return 0;
}

static const struct seq_operations ip_vs_conn_seq_ops = {
	.start = ip_vs_conn_seq_start,
	.next  = ip_vs_conn_seq_next,
	.stop  = ip_vs_conn_seq_stop,
	.show  = ip_vs_conn_seq_show,
};

static int ip_vs_conn_open(struct inode *inode, struct file *file)
{
	return seq_open(file, &ip_vs_conn_seq_ops);
}

static const struct file_operations ip_vs_conn_fops = {
	.owner	 = THIS_MODULE,
	.open    = ip_vs_conn_open,
	.read    = seq_read,
	.llseek  = seq_lseek,
	.release = seq_release,
};

static const char *ip_vs_origin_name(unsigned flags)
{
	if (flags & IP_VS_CONN_F_SYNC)
		return "SYNC";
	else
		return "LOCAL";
}

static int ip_vs_conn_sync_seq_show(struct seq_file *seq, void *v)
{

	if (v == SEQ_START_TOKEN)
		seq_puts(seq,
   "Pro FromIP   FPrt ToIP     TPrt DestIP   DPrt State       Origin Expires\n");
	else {
		const struct ip_vs_conn *cp = v;

#ifdef CONFIG_IP_VS_IPV6
		if (cp->af == AF_INET6)
			seq_printf(seq, "%-3s %pI6 %04X %pI6 %04X %pI6 %04X %-11s %-6s %7lu\n",
				ip_vs_proto_name(cp->protocol),
				&cp->caddr.in6, ntohs(cp->cport),
				&cp->vaddr.in6, ntohs(cp->vport),
				&cp->daddr.in6, ntohs(cp->dport),
				ip_vs_state_name(cp->protocol, cp->state),
				ip_vs_origin_name(cp->flags),
				(cp->timer.expires-jiffies)/HZ);
		else
#endif
			seq_printf(seq,
				"%-3s %08X %04X %08X %04X "
				"%08X %04X %-11s %-6s %7lu\n",
				ip_vs_proto_name(cp->protocol),
				ntohl(cp->caddr.ip), ntohs(cp->cport),
				ntohl(cp->vaddr.ip), ntohs(cp->vport),
				ntohl(cp->daddr.ip), ntohs(cp->dport),
				ip_vs_state_name(cp->protocol, cp->state),
				ip_vs_origin_name(cp->flags),
				(cp->timer.expires-jiffies)/HZ);
	}
	return 0;
}

static const struct seq_operations ip_vs_conn_sync_seq_ops = {
	.start = ip_vs_conn_seq_start,
	.next  = ip_vs_conn_seq_next,
	.stop  = ip_vs_conn_seq_stop,
	.show  = ip_vs_conn_sync_seq_show,
};

static int ip_vs_conn_sync_open(struct inode *inode, struct file *file)
{
	return seq_open(file, &ip_vs_conn_sync_seq_ops);
}

static const struct file_operations ip_vs_conn_sync_fops = {
	.owner	 = THIS_MODULE,
	.open    = ip_vs_conn_sync_open,
	.read    = seq_read,
	.llseek  = seq_lseek,
	.release = seq_release,
};

#endif


/*
 *      Randomly drop connection entries before running out of memory
 */
static inline int todrop_entry(struct ip_vs_conn *cp)
{
	/*
	 * The drop rate array needs tuning for real environments.
	 * Called from timer bh only => no locking
	 */
	static const char todrop_rate[9] = {0, 1, 2, 3, 4, 5, 6, 7, 8};
	static char todrop_counter[9] = {0};
	int i;

	/* if the conn entry hasn't lasted for 60 seconds, don't drop it.
	   This will leave enough time for normal connection to get
	   through. */
	if (time_before(cp->timeout + jiffies, cp->timer.expires + 60*HZ))
		return 0;

	/* Don't drop the entry if its number of incoming packets is not
	   located in [0, 8] */
	i = atomic_read(&cp->in_pkts);
	if (i > 8 || i < 0) return 0;

	if (!todrop_rate[i]) return 0;
	if (--todrop_counter[i] > 0) return 0;

	todrop_counter[i] = todrop_rate[i];
	return 1;
}

/* Called from keventd and must protect itself from softirqs */
void ip_vs_random_dropentry(void)
{
	int idx;
	struct ip_vs_conn *cp;

	/*
	 * Randomly scan 1/32 of the whole table every second
	 */
	for (idx = 0; idx < (ip_vs_conn_tab_size>>5); idx++) {
		unsigned hash = net_random() & ip_vs_conn_tab_mask;

		/*
		 *  Lock is actually needed in this loop.
		 */
		ct_write_lock_bh(hash);

		list_for_each_entry(cp, &ip_vs_conn_tab[hash], c_list) {
			if (cp->flags & IP_VS_CONN_F_TEMPLATE)
				/* connection template */
				continue;

			if (cp->protocol == IPPROTO_TCP) {
				switch(cp->state) {
				case IP_VS_TCP_S_SYN_RECV:
				case IP_VS_TCP_S_SYNACK:
					break;

				case IP_VS_TCP_S_ESTABLISHED:
					if (todrop_entry(cp))
						break;
					continue;

				default:
					continue;
				}
			} else {
				if (!todrop_entry(cp))
					continue;
			}

			IP_VS_DBG(4, "del connection\n");
			ip_vs_conn_expire_now(cp);
			if (cp->control) {
				IP_VS_DBG(4, "del conn template\n");
				ip_vs_conn_expire_now(cp->control);
			}
		}
		ct_write_unlock_bh(hash);
	}
}


/*
 *      Flush all the connection entries in the ip_vs_conn_tab
 */
static void ip_vs_conn_flush(void)
{
	int idx;
	struct ip_vs_conn *cp;

  flush_again:
	for (idx = 0; idx < ip_vs_conn_tab_size; idx++) {
		/*
		 *  Lock is actually needed in this loop.
		 */
		ct_write_lock_bh(idx);

		list_for_each_entry(cp, &ip_vs_conn_tab[idx], c_list) {

			IP_VS_DBG(4, "del connection\n");
			ip_vs_conn_expire_now(cp);
			if (cp->control) {
				IP_VS_DBG(4, "del conn template\n");
				ip_vs_conn_expire_now(cp->control);
			}
		}
		ct_write_unlock_bh(idx);
	}

	/* the counter may be not NULL, because maybe some conn entries
	   are run by slow timer handler or unhashed but still referred */
	if (atomic_read(&ip_vs_conn_count) != 0) {
		schedule();
		goto flush_again;
	}
}


int __init ip_vs_conn_init(void)
{
	int idx;

	/* Compute size and mask */
	ip_vs_conn_tab_size = 1 << ip_vs_conn_tab_bits;
	ip_vs_conn_tab_mask = ip_vs_conn_tab_size - 1;

	/*
	 * Allocate the connection hash table and initialize its list heads
	 */
	ip_vs_conn_tab = vmalloc(ip_vs_conn_tab_size *
				 sizeof(struct list_head));
	if (!ip_vs_conn_tab)
		return -ENOMEM;

	/* Allocate ip_vs_conn slab cache */
	ip_vs_conn_cachep = kmem_cache_create("ip_vs_conn",
					      sizeof(struct ip_vs_conn), 0,
					      SLAB_HWCACHE_ALIGN, NULL);
	if (!ip_vs_conn_cachep) {
		vfree(ip_vs_conn_tab);
		return -ENOMEM;
	}

	pr_info("Connection hash table configured "
		"(size=%d, memory=%ldKbytes)\n",
		ip_vs_conn_tab_size,
		(long)(ip_vs_conn_tab_size*sizeof(struct list_head))/1024);
	IP_VS_DBG(0, "Each connection entry needs %Zd bytes at least\n",
		  sizeof(struct ip_vs_conn));

	for (idx = 0; idx < ip_vs_conn_tab_size; idx++) {
		INIT_LIST_HEAD(&ip_vs_conn_tab[idx]);
	}

	for (idx = 0; idx < CT_LOCKARRAY_SIZE; idx++)  {
		rwlock_init(&__ip_vs_conntbl_lock_array[idx].l);
	}

	proc_net_fops_create(&init_net, "ip_vs_conn", 0, &ip_vs_conn_fops);
	proc_net_fops_create(&init_net, "ip_vs_conn_sync", 0, &ip_vs_conn_sync_fops);

	/* calculate the random value for connection hash */
	get_random_bytes(&ip_vs_conn_rnd, sizeof(ip_vs_conn_rnd));

	return 0;
}


void ip_vs_conn_cleanup(void)
{
	/* flush all the connection entries first */
	ip_vs_conn_flush();

	/* Release the empty cache */
	kmem_cache_destroy(ip_vs_conn_cachep);
	proc_net_remove(&init_net, "ip_vs_conn");
	proc_net_remove(&init_net, "ip_vs_conn_sync");
	vfree(ip_vs_conn_tab);
}