[WATCHDOG] Merge code clean-up's from Alan Cox.

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / net / ipv4 / 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:
 *
 */

#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/seq_file.h>
#include <linux/jhash.h>
#include <linux/random.h>

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


/*
 *  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(unsigned proto, __be32 addr, __be16 port)
{
        return jhash_3words((__force u32)addr, (__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;

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

        ct_write_lock(hash);

        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 {
                IP_VS_ERR("ip_vs_conn_hash(): request for already hashed, "
                          "called from %p\n", __builtin_return_address(0));
                ret = 0;
        }

        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->protocol, cp->caddr, cp->cport);

        ct_write_lock(hash);

        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;

        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.
 *      s_addr, s_port: pkt source address (foreign host)
 *      d_addr, d_port: pkt dest address (load balancer)
 */
static inline struct ip_vs_conn *__ip_vs_conn_in_get
(int protocol, __be32 s_addr, __be16 s_port, __be32 d_addr, __be16 d_port)
{
        unsigned hash;
        struct ip_vs_conn *cp;

        hash = ip_vs_conn_hashkey(protocol, s_addr, s_port);

        ct_read_lock(hash);

        list_for_each_entry(cp, &ip_vs_conn_tab[hash], c_list) {
                if (s_addr==cp->caddr && s_port==cp->cport &&
                    d_port==cp->vport && d_addr==cp->vaddr &&
                    ((!s_port) ^ (!(cp->flags & IP_VS_CONN_F_NO_CPORT))) &&
                    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
(int protocol, __be32 s_addr, __be16 s_port, __be32 d_addr, __be16 d_port)
{
        struct ip_vs_conn *cp;

        cp = __ip_vs_conn_in_get(protocol, s_addr, s_port, d_addr, d_port);
        if (!cp && atomic_read(&ip_vs_conn_no_cport_cnt))
                cp = __ip_vs_conn_in_get(protocol, s_addr, 0, d_addr, d_port);

        IP_VS_DBG(9, "lookup/in %s %u.%u.%u.%u:%d->%u.%u.%u.%u:%d %s\n",
                  ip_vs_proto_name(protocol),
                  NIPQUAD(s_addr), ntohs(s_port),
                  NIPQUAD(d_addr), ntohs(d_port),
                  cp?"hit":"not hit");

        return cp;
}

/* Get reference to connection template */
struct ip_vs_conn *ip_vs_ct_in_get
(int protocol, __be32 s_addr, __be16 s_port, __be32 d_addr, __be16 d_port)
{
        unsigned hash;
        struct ip_vs_conn *cp;

        hash = ip_vs_conn_hashkey(protocol, s_addr, s_port);

        ct_read_lock(hash);

        list_for_each_entry(cp, &ip_vs_conn_tab[hash], c_list) {
                if (s_addr==cp->caddr && s_port==cp->cport &&
                    d_port==cp->vport && d_addr==cp->vaddr &&
                    cp->flags & IP_VS_CONN_F_TEMPLATE &&
                    protocol==cp->protocol) {
                        /* HIT */
                        atomic_inc(&cp->refcnt);
                        goto out;
                }
        }
        cp = NULL;

  out:
        ct_read_unlock(hash);

        IP_VS_DBG(9, "template lookup/in %s %u.%u.%u.%u:%d->%u.%u.%u.%u:%d %s\n",
                  ip_vs_proto_name(protocol),
                  NIPQUAD(s_addr), ntohs(s_port),
                  NIPQUAD(d_addr), ntohs(d_port),
                  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.
 *      s_addr, s_port: pkt source address (inside host)
 *      d_addr, d_port: pkt dest address (foreign host)
 */
struct ip_vs_conn *ip_vs_conn_out_get
(int protocol, __be32 s_addr, __be16 s_port, __be32 d_addr, __be16 d_port)
{
        unsigned hash;
        struct ip_vs_conn *cp, *ret=NULL;

        /*
         *      Check for "full" addressed entries
         */
        hash = ip_vs_conn_hashkey(protocol, d_addr, d_port);

        ct_read_lock(hash);

        list_for_each_entry(cp, &ip_vs_conn_tab[hash], c_list) {
                if (d_addr == cp->caddr && d_port == cp->cport &&
                    s_port == cp->dport && s_addr == cp->daddr &&
                    protocol == cp->protocol) {
                        /* HIT */
                        atomic_inc(&cp->refcnt);
                        ret = cp;
                        break;
                }
        }

        ct_read_unlock(hash);

        IP_VS_DBG(9, "lookup/out %s %u.%u.%u.%u:%d->%u.%u.%u.%u:%d %s\n",
                  ip_vs_proto_name(protocol),
                  NIPQUAD(s_addr), ntohs(s_port),
                  NIPQUAD(d_addr), ntohs(d_port),
                  ret?"hit":"not hit");

        return ret;
}


/*
 *      Put back the conn and restart its timer with its timeout
 */
void ip_vs_conn_put(struct ip_vs_conn *cp)
{
        /* reset it expire in its timeout */
        mod_timer(&cp->timer, jiffies+cp->timeout);

        __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;
        }
}


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

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

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

        IP_VS_DBG(7, "Bind-dest %s c:%u.%u.%u.%u:%d v:%u.%u.%u.%u:%d "
                  "d:%u.%u.%u.%u:%d fwd:%c s:%u conn->flags:%X conn->refcnt:%d "
                  "dest->refcnt:%d\n",
                  ip_vs_proto_name(cp->protocol),
                  NIPQUAD(cp->caddr), ntohs(cp->cport),
                  NIPQUAD(cp->vaddr), ntohs(cp->vport),
                  NIPQUAD(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->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(7, "Unbind-dest %s c:%u.%u.%u.%u:%d v:%u.%u.%u.%u:%d "
                  "d:%u.%u.%u.%u:%d fwd:%c s:%u conn->flags:%X conn->refcnt:%d "
                  "dest->refcnt:%d\n",
                  ip_vs_proto_name(cp->protocol),
                  NIPQUAD(cp->caddr), ntohs(cp->cport),
                  NIPQUAD(cp->vaddr), ntohs(cp->vport),
                  NIPQUAD(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(9, "check_template: dest not available for "
                          "protocol %s s:%u.%u.%u.%u:%d v:%u.%u.%u.%u:%d "
                          "-> d:%u.%u.%u.%u:%d\n",
                          ip_vs_proto_name(ct->protocol),
                          NIPQUAD(ct->caddr), ntohs(ct->cport),
                          NIPQUAD(ct->vaddr), ntohs(ct->vport),
                          NIPQUAD(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))
                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 (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(int proto, __be32 caddr, __be16 cport, __be32 vaddr, __be16 vport,
               __be32 daddr, __be16 dport, unsigned flags,
               struct ip_vs_dest *dest)
{
        struct ip_vs_conn *cp;
        struct ip_vs_protocol *pp = ip_vs_proto_get(proto);

        cp = kmem_cache_zalloc(ip_vs_conn_cachep, GFP_ATOMIC);
        if (cp == NULL) {
                IP_VS_ERR_RL("ip_vs_conn_new: no memory available.\n");
                return NULL;
        }

        INIT_LIST_HEAD(&cp->c_list);
        setup_timer(&cp->timer, ip_vs_conn_expire, (unsigned long)cp);
        cp->protocol       = proto;
        cp->caddr          = caddr;
        cp->cport          = cport;
        cp->vaddr          = vaddr;
        cp->vport          = vport;
        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 */
        ip_vs_bind_xmit(cp);

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

        /* 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;

                seq_printf(seq,
                        "%-3s %08X %04X %08X %04X %08X %04X %-11s %7lu\n",
                                ip_vs_proto_name(cp->protocol),
                                ntohl(cp->caddr), ntohs(cp->cport),
                                ntohl(cp->vaddr), ntohs(cp->vport),
                                ntohl(cp->daddr), 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;

                seq_printf(seq,
                        "%-3s %08X %04X %08X %04X %08X %04X %-11s %-6s %7lu\n",
                                ip_vs_proto_name(cp->protocol),
                                ntohl(cp->caddr), ntohs(cp->cport),
                                ntohl(cp->vaddr), ntohs(cp->vport),
                                ntohl(cp->daddr), 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 ip_vs_conn_init(void)
{
        int idx;

        /*
         * 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;
        }

        IP_VS_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);
}