/*
 * 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/inet.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.
*/
static 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 __read_mostly;
static int ip_vs_conn_tab_mask __read_mostly;

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

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

/*  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 __read_mostly;

/*
 *  Fine locking granularity for big connection hash table
 */
#define CT_LOCKARRAY_BITS  5
#define CT_LOCKARRAY_SIZE  (1<<CT_LOCKARRAY_BITS)
#define CT_LOCKARRAY_MASK  (CT_LOCKARRAY_SIZE-1)

/* We need an addrstrlen that works with or without v6 */
#ifdef CONFIG_IP_VS_IPV6
#define IP_VS_ADDRSTRLEN INET6_ADDRSTRLEN
#else
#define IP_VS_ADDRSTRLEN (8+1)
#endif

struct ip_vs_aligned_lock
{
        spinlock_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_write_lock_bh(unsigned int key)
{
        spin_lock_bh(&__ip_vs_conntbl_lock_array[key&CT_LOCKARRAY_MASK].l);
}

static inline void ct_write_unlock_bh(unsigned int key)
{
        spin_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(struct net *net, int af, unsigned int 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) ^
                        ((size_t)net>>8)) & ip_vs_conn_tab_mask;
#endif
        return (jhash_3words((__force u32)addr->ip, (__force u32)port, proto,
                            ip_vs_conn_rnd) ^
                ((size_t)net>>8)) & ip_vs_conn_tab_mask;
}

static unsigned int ip_vs_conn_hashkey_param(const struct ip_vs_conn_param *p,
                                             bool inverse)
{
        const union nf_inet_addr *addr;
        __be16 port;

        if (p->pe_data && p->pe->hashkey_raw)
                return p->pe->hashkey_raw(p, ip_vs_conn_rnd, inverse) &
                        ip_vs_conn_tab_mask;

        if (likely(!inverse)) {
                addr = p->caddr;
                port = p->cport;
        } else {
                addr = p->vaddr;
                port = p->vport;
        }

        return ip_vs_conn_hashkey(p->net, p->af, p->protocol, addr, port);
}

static unsigned int ip_vs_conn_hashkey_conn(const struct ip_vs_conn *cp)
{
        struct ip_vs_conn_param p;

        ip_vs_conn_fill_param(ip_vs_conn_net(cp), cp->af, cp->protocol,
                              &cp->caddr, cp->cport, NULL, 0, &p);

        if (cp->pe) {
                p.pe = cp->pe;
                p.pe_data = cp->pe_data;
                p.pe_data_len = cp->pe_data_len;
        }

        return ip_vs_conn_hashkey_param(&p, false);
}

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

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

        if (!(cp->flags & IP_VS_CONN_F_HASHED)) {
                cp->flags |= IP_VS_CONN_F_HASHED;
                atomic_inc(&cp->refcnt);
                hlist_add_head_rcu(&cp->c_list, &ip_vs_conn_tab[hash]);
                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_bh(hash);

        return ret;
}


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

        /* unhash it and decrease its reference counter */
        hash = ip_vs_conn_hashkey_conn(cp);

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

        if (cp->flags & IP_VS_CONN_F_HASHED) {
                hlist_del_rcu(&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_bh(hash);

        return ret;
}

/* Try to unlink ip_vs_conn from ip_vs_conn_tab.
 * returns bool success.
 */
static inline bool ip_vs_conn_unlink(struct ip_vs_conn *cp)
{
        unsigned int hash;
        bool ret;

        hash = ip_vs_conn_hashkey_conn(cp);

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

        if (cp->flags & IP_VS_CONN_F_HASHED) {
                ret = false;
                /* Decrease refcnt and unlink conn only if we are last user */
                if (atomic_cmpxchg(&cp->refcnt, 1, 0) == 1) {
                        hlist_del_rcu(&cp->c_list);
                        cp->flags &= ~IP_VS_CONN_F_HASHED;
                        ret = true;
                }
        } else
                ret = atomic_read(&cp->refcnt) ? false : true;

        spin_unlock(&cp->lock);
        ct_write_unlock_bh(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 int hash;
        struct ip_vs_conn *cp;

        hash = ip_vs_conn_hashkey_param(p, false);

        rcu_read_lock();

        hlist_for_each_entry_rcu(cp, &ip_vs_conn_tab[hash], c_list) {
                if (p->cport == cp->cport && p->vport == cp->vport &&
                    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->flags & IP_VS_CONN_F_NO_CPORT))) &&
                    p->protocol == cp->protocol &&
                    ip_vs_conn_net_eq(cp, p->net)) {
                        if (!__ip_vs_conn_get(cp))
                                continue;
                        /* HIT */
                        rcu_read_unlock();
                        return cp;
                }
        }

        rcu_read_unlock();

        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,
                            int inverse, struct ip_vs_conn_param *p)
{
        __be16 _ports[2], *pptr;
        struct net *net = skb_net(skb);

        pptr = frag_safe_skb_hp(skb, iph->len, sizeof(_ports), _ports, iph);
        if (pptr == NULL)
                return 1;

        if (likely(!inverse))
                ip_vs_conn_fill_param(net, af, iph->protocol, &iph->saddr,
                                      pptr[0], &iph->daddr, pptr[1], p);
        else
                ip_vs_conn_fill_param(net, 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,
                        const struct ip_vs_iphdr *iph, int inverse)
{
        struct ip_vs_conn_param p;

        if (ip_vs_conn_fill_param_proto(af, skb, iph, 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 int hash;
        struct ip_vs_conn *cp;

        hash = ip_vs_conn_hashkey_param(p, false);

        rcu_read_lock();

        hlist_for_each_entry_rcu(cp, &ip_vs_conn_tab[hash], c_list) {
                if (unlikely(p->pe_data && p->pe->ct_match)) {
                        if (!ip_vs_conn_net_eq(cp, p->net))
                                continue;
                        if (p->pe == cp->pe && p->pe->ct_match(p, cp)) {
                                if (__ip_vs_conn_get(cp))
                                        goto out;
                        }
                        continue;
                }

                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->vport == cp->vport && p->cport == cp->cport &&
                    cp->flags & IP_VS_CONN_F_TEMPLATE &&
                    p->protocol == cp->protocol &&
                    ip_vs_conn_net_eq(cp, p->net)) {
                        if (__ip_vs_conn_get(cp))
                                goto out;
                }
        }
        cp = NULL;

  out:
        rcu_read_unlock();

        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 int hash;
        struct ip_vs_conn *cp, *ret=NULL;

        /*
         *      Check for "full" addressed entries
         */
        hash = ip_vs_conn_hashkey_param(p, true);

        rcu_read_lock();

        hlist_for_each_entry_rcu(cp, &ip_vs_conn_tab[hash], c_list) {
                if (p->vport == cp->cport && p->cport == cp->dport &&
                    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->protocol == cp->protocol &&
                    ip_vs_conn_net_eq(cp, p->net)) {
                        if (!__ip_vs_conn_get(cp))
                                continue;
                        /* HIT */
                        ret = cp;
                        break;
                }
        }

        rcu_read_unlock();

        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,
                         const struct ip_vs_iphdr *iph, int inverse)
{
        struct ip_vs_conn_param p;

        if (ip_vs_conn_fill_param_proto(af, skb, iph, 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_bh(&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_bh(&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:
#ifdef CONFIG_IP_VS_IPV6
                if (cp->daf == AF_INET6)
                        cp->packet_xmit = ip_vs_tunnel_xmit_v6;
                else
#endif
                        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:
                if (cp->daf == AF_INET6)
                        cp->packet_xmit = ip_vs_tunnel_xmit_v6;
                else
                        cp->packet_xmit = ip_vs_tunnel_xmit;
                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;
        __u32 flags;

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

        /* Increase the refcnt counter of the dest */
        ip_vs_dest_hold(dest);

        conn_flags = atomic_read(&dest->conn_flags);
        if (cp->protocol != IPPROTO_UDP)
                conn_flags &= ~IP_VS_CONN_F_ONE_PACKET;
        flags = cp->flags;
        /* Bind with the destination and its corresponding transmitter */
        if (flags & IP_VS_CONN_F_SYNC) {
                /* if the connection is not template and is created
                 * by sync, preserve the activity flag.
                 */
                if (!(flags & IP_VS_CONN_F_TEMPLATE))
                        conn_flags &= ~IP_VS_CONN_F_INACTIVE;
                /* connections inherit forwarding method from dest */
                flags &= ~(IP_VS_CONN_F_FWD_MASK | IP_VS_CONN_F_NOOUTPUT);
        }
        flags |= conn_flags;
        cp->flags = 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->daf, &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 (!(flags & IP_VS_CONN_F_TEMPLATE)) {
                /* It is a normal connection, so modify the counters
                 * according to the flags, later the protocol can
                 * update them on state change
                 */
                if (!(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 persistent 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.
 */
void ip_vs_try_bind_dest(struct ip_vs_conn *cp)
{
        struct ip_vs_dest *dest;

        rcu_read_lock();

        /* This function is only invoked by the synchronization code. We do
         * not currently support heterogeneous pools with synchronization,
         * so we can make the assumption that the svc_af is the same as the
         * dest_af
         */
        dest = ip_vs_find_dest(ip_vs_conn_net(cp), cp->af, cp->af, &cp->daddr,
                               cp->dport, &cp->vaddr, cp->vport,
                               cp->protocol, cp->fwmark, cp->flags);
        if (dest) {
                struct ip_vs_proto_data *pd;

                spin_lock_bh(&cp->lock);
                if (cp->dest) {
                        spin_unlock_bh(&cp->lock);
                        rcu_read_unlock();
                        return;
                }

                /* Applications work depending on the forwarding method
                 * but better to reassign them always when binding dest */
                if (cp->app)
                        ip_vs_unbind_app(cp);

                ip_vs_bind_dest(cp, dest);
                spin_unlock_bh(&cp->lock);

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

                pd = ip_vs_proto_data_get(ip_vs_conn_net(cp), cp->protocol);
                if (pd && atomic_read(&pd->appcnt))
                        ip_vs_bind_app(cp, pd->pp);
        }
        rcu_read_unlock();
}


/*
 *      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->daf, &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 persistent 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;
        }

        ip_vs_dest_put(dest);
}

static int expire_quiescent_template(struct netns_ipvs *ipvs,
                                     struct ip_vs_dest *dest)
{
#ifdef CONFIG_SYSCTL
        return ipvs->sysctl_expire_quiescent_template &&
                (atomic_read(&dest->weight) == 0);
#else
        return 0;
#endif
}

/*
 *      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;
        struct netns_ipvs *ipvs = net_ipvs(ip_vs_conn_net(ct));

        /*
         * Checking the dest server status.
         */
        if ((dest == NULL) ||
            !(dest->flags & IP_VS_DEST_F_AVAILABLE) ||
            expire_quiescent_template(ipvs, dest)) {
                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->daf, &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.
                 */
                __ip_vs_conn_put(ct);
                return 0;
        }
        return 1;
}

static void ip_vs_conn_rcu_free(struct rcu_head *head)
{
        struct ip_vs_conn *cp = container_of(head, struct ip_vs_conn,
                                             rcu_head);

        ip_vs_pe_put(cp->pe);
        kfree(cp->pe_data);
        kmem_cache_free(ip_vs_conn_cachep, cp);
}

static void ip_vs_conn_expire(unsigned long data)
{
        struct ip_vs_conn *cp = (struct ip_vs_conn *)data;
        struct net *net = ip_vs_conn_net(cp);
        struct netns_ipvs *ipvs = net_ipvs(net);

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

        /* Unlink conn if not referenced anymore */
        if (likely(ip_vs_conn_unlink(cp))) {
                /* delete the timer if it is activated by other users */
                del_timer(&cp->timer);

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

                if (cp->flags & IP_VS_CONN_F_NFCT) {
                        /* Do not access conntracks during subsys cleanup
                         * because nf_conntrack_find_get can not be used after
                         * conntrack cleanup for the net.
                         */
                        smp_rmb();
                        if (ipvs->enable)
                                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);
                call_rcu(&cp->rcu_head, ip_vs_conn_rcu_free);
                atomic_dec(&ipvs->conn_count);
                return;
        }

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

        atomic_inc(&cp->refcnt);
        cp->timeout = 60*HZ;

        if (ipvs->sync_state & IP_VS_STATE_MASTER)
                ip_vs_sync_conn(net, cp, sysctl_sync_threshold(ipvs));

        ip_vs_conn_put(cp);
}

/* Modify timer, so that it expires as soon as possible.
 * Can be called without reference only if under RCU lock.
 */
void ip_vs_conn_expire_now(struct ip_vs_conn *cp)
{
        /* Using mod_timer_pending will ensure the timer is not
         * modified after the final del_timer in ip_vs_conn_expire.
         */
        if (timer_pending(&cp->timer) &&
            time_after(cp->timer.expires, jiffies))
                mod_timer_pending(&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, int dest_af,
               const union nf_inet_addr *daddr, __be16 dport, unsigned int flags,
               struct ip_vs_dest *dest, __u32 fwmark)
{
        struct ip_vs_conn *cp;
        struct netns_ipvs *ipvs = net_ipvs(p->net);
        struct ip_vs_proto_data *pd = ip_vs_proto_data_get(p->net,
                                                           p->protocol);

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

        INIT_HLIST_NODE(&cp->c_list);
        setup_timer(&cp->timer, ip_vs_conn_expire, (unsigned long)cp);
        ip_vs_conn_net_set(cp, p->net);
        cp->af             = p->af;
        cp->daf            = dest_af;
        cp->protocol       = p->protocol;
        ip_vs_addr_set(p->af, &cp->caddr, p->caddr);
        cp->cport          = p->cport;
        /* proto should only be IPPROTO_IP if p->vaddr is a fwmark */
        ip_vs_addr_set(p->protocol == IPPROTO_IP ? AF_UNSPEC : p->af,
                       &cp->vaddr, p->vaddr);
        cp->vport          = p->vport;
        ip_vs_addr_set(cp->daf, &cp->daddr, daddr);
        cp->dport          = dport;
        cp->flags          = flags;
        cp->fwmark         = fwmark;
        if (flags & IP_VS_CONN_F_TEMPLATE && p->pe) {
                ip_vs_pe_get(p->pe);
                cp->pe = p->pe;
                cp->pe_data = p->pe_data;
                cp->pe_data_len = p->pe_data_len;
        } else {
                cp->pe = NULL;
                cp->pe_data = NULL;
                cp->pe_data_len = 0;
        }
        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);

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

        cp->packet_xmit = NULL;
        cp->app = NULL;
        cp->app_data = NULL;
        /* reset struct ip_vs_seq */
        cp->in_seq.delta = 0;
        cp->out_seq.delta = 0;

        atomic_inc(&ipvs->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 */
        cp->dest = NULL;
        ip_vs_bind_dest(cp, dest);

        /* Set its state and timeout */
        cp->state = 0;
        cp->old_state = 0;
        cp->timeout = 3*HZ;
        cp->sync_endtime = jiffies & ~3UL;

        /* 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(pd && atomic_read(&pd->appcnt)))
                ip_vs_bind_app(cp, pd->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(ipvs))
                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
struct ip_vs_iter_state {
        struct seq_net_private  p;
        struct hlist_head       *l;
};

static void *ip_vs_conn_array(struct seq_file *seq, loff_t pos)
{
        int idx;
        struct ip_vs_conn *cp;
        struct ip_vs_iter_state *iter = seq->private;

        for (idx = 0; idx < ip_vs_conn_tab_size; idx++) {
                hlist_for_each_entry_rcu(cp, &ip_vs_conn_tab[idx], c_list) {
                        /* __ip_vs_conn_get() is not needed by
                         * ip_vs_conn_seq_show and ip_vs_conn_sync_seq_show
                         */
                        if (pos-- == 0) {
                                iter->l = &ip_vs_conn_tab[idx];
                                return cp;
                        }
                }
                cond_resched_rcu();

        }

        return NULL;
}

static void *ip_vs_conn_seq_start(struct seq_file *seq, loff_t *pos)
        __acquires(RCU)
{
        struct ip_vs_iter_state *iter = seq->private;

        iter->l = NULL;
        rcu_read_lock();
        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 ip_vs_iter_state *iter = seq->private;
        struct hlist_node *e;
        struct hlist_head *l = iter->l;
        int idx;

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

        /* more on same hash chain? */
        e = rcu_dereference(hlist_next_rcu(&cp->c_list));
        if (e)
                return hlist_entry(e, struct ip_vs_conn, c_list);

        idx = l - ip_vs_conn_tab;
        while (++idx < ip_vs_conn_tab_size) {
                hlist_for_each_entry_rcu(cp, &ip_vs_conn_tab[idx], c_list) {
                        iter->l = &ip_vs_conn_tab[idx];
                        return cp;
                }
                cond_resched_rcu();
        }
        iter->l = NULL;
        return NULL;
}

static void ip_vs_conn_seq_stop(struct seq_file *seq, void *v)
        __releases(RCU)
{
        rcu_read_unlock();
}

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 PEName PEData\n");
        else {
                const struct ip_vs_conn *cp = v;
                struct net *net = seq_file_net(seq);
                char pe_data[IP_VS_PENAME_MAXLEN + IP_VS_PEDATA_MAXLEN + 3];
                size_t len = 0;
                char dbuf[IP_VS_ADDRSTRLEN];

                if (!ip_vs_conn_net_eq(cp, net))
                        return 0;
                if (cp->pe_data) {
                        pe_data[0] = ' ';
                        len = strlen(cp->pe->name);
                        memcpy(pe_data + 1, cp->pe->name, len);
                        pe_data[len + 1] = ' ';
                        len += 2;
                        len += cp->pe->show_pe_data(cp, pe_data + len);
                }
                pe_data[len] = '\0';

#ifdef CONFIG_IP_VS_IPV6
                if (cp->daf == AF_INET6)
                        snprintf(dbuf, sizeof(dbuf), "%pI6", &cp->daddr.in6);
                else
#endif
                        snprintf(dbuf, sizeof(dbuf), "%08X",
                                 ntohl(cp->daddr.ip));

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

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_net,
};

static const char *ip_vs_origin_name(unsigned int 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)
{
        char dbuf[IP_VS_ADDRSTRLEN];

        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;
                struct net *net = seq_file_net(seq);

                if (!ip_vs_conn_net_eq(cp, net))
                        return 0;

#ifdef CONFIG_IP_VS_IPV6
                if (cp->daf == AF_INET6)
                        snprintf(dbuf, sizeof(dbuf), "%pI6", &cp->daddr.in6);
                else
#endif
                        snprintf(dbuf, sizeof(dbuf), "%08X",
                                 ntohl(cp->daddr.ip));

#ifdef CONFIG_IP_VS_IPV6
                if (cp->af == AF_INET6)
                        seq_printf(seq, "%-3s %pI6 %04X %pI6 %04X "
                                "%s %04X %-11s %-6s %7lu\n",
                                ip_vs_proto_name(cp->protocol),
                                &cp->caddr.in6, ntohs(cp->cport),
                                &cp->vaddr.in6, ntohs(cp->vport),
                                dbuf, 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 "
                                "%s %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),
                                dbuf, 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_net(inode, file, &ip_vs_conn_sync_seq_ops,
                            sizeof(struct ip_vs_iter_state));
}

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_net,
};

#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(struct net *net)
{
        int idx;
        struct ip_vs_conn *cp, *cp_c;

        rcu_read_lock();
        /*
         * Randomly scan 1/32 of the whole table every second
         */
        for (idx = 0; idx < (ip_vs_conn_tab_size>>5); idx++) {
                unsigned int hash = prandom_u32() & ip_vs_conn_tab_mask;

                hlist_for_each_entry_rcu(cp, &ip_vs_conn_tab[hash], c_list) {
                        if (cp->flags & IP_VS_CONN_F_TEMPLATE)
                                /* connection template */
                                continue;
                        if (!ip_vs_conn_net_eq(cp, net))
                                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 (cp->protocol == IPPROTO_SCTP) {
                                switch (cp->state) {
                                case IP_VS_SCTP_S_INIT1:
                                case IP_VS_SCTP_S_INIT:
                                        break;
                                case IP_VS_SCTP_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);
                        cp_c = cp->control;
                        /* cp->control is valid only with reference to cp */
                        if (cp_c && __ip_vs_conn_get(cp)) {
                                IP_VS_DBG(4, "del conn template\n");
                                ip_vs_conn_expire_now(cp_c);
                                __ip_vs_conn_put(cp);
                        }
                }
                cond_resched_rcu();
        }
        rcu_read_unlock();
}


/*
 *      Flush all the connection entries in the ip_vs_conn_tab
 */
static void ip_vs_conn_flush(struct net *net)
{
        int idx;
        struct ip_vs_conn *cp, *cp_c;
        struct netns_ipvs *ipvs = net_ipvs(net);

flush_again:
        rcu_read_lock();
        for (idx = 0; idx < ip_vs_conn_tab_size; idx++) {

                hlist_for_each_entry_rcu(cp, &ip_vs_conn_tab[idx], c_list) {
                        if (!ip_vs_conn_net_eq(cp, net))
                                continue;
                        IP_VS_DBG(4, "del connection\n");
                        ip_vs_conn_expire_now(cp);
                        cp_c = cp->control;
                        /* cp->control is valid only with reference to cp */
                        if (cp_c && __ip_vs_conn_get(cp)) {
                                IP_VS_DBG(4, "del conn template\n");
                                ip_vs_conn_expire_now(cp_c);
                                __ip_vs_conn_put(cp);
                        }
                }
                cond_resched_rcu();
        }
        rcu_read_unlock();

        /* 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(&ipvs->conn_count) != 0) {
                schedule();
                goto flush_again;
        }
}
/*
 * per netns init and exit
 */
int __net_init ip_vs_conn_net_init(struct net *net)
{
        struct netns_ipvs *ipvs = net_ipvs(net);

        atomic_set(&ipvs->conn_count, 0);

        proc_create("ip_vs_conn", 0, net->proc_net, &ip_vs_conn_fops);
        proc_create("ip_vs_conn_sync", 0, net->proc_net, &ip_vs_conn_sync_fops);
        return 0;
}

void __net_exit ip_vs_conn_net_cleanup(struct net *net)
{
        /* flush all the connection entries first */
        ip_vs_conn_flush(net);
        remove_proc_entry("ip_vs_conn", net->proc_net);
        remove_proc_entry("ip_vs_conn_sync", net->proc_net);
}

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(*ip_vs_conn_tab));
        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_HLIST_HEAD(&ip_vs_conn_tab[idx]);

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

        /* 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)
{
        /* Wait all ip_vs_conn_rcu_free() callbacks to complete */
        rcu_barrier();
        /* Release the empty cache */
        kmem_cache_destroy(ip_vs_conn_cachep);
        vfree(ip_vs_conn_tab);
}