/*
 * 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.
 *
 * Version 1,   is capable of handling both version 0 and 1 messages.
 *              Version 0 is the plain old format.
 *              Note Version 0 receivers will just drop Ver 1 messages.
 *              Version 1 is capable of handle IPv6, Persistence data,
 *              time-outs, and firewall marks.
 *              In ver.1 "ip_vs_sync_conn_options" will be sent in netw. order.
 *              Ver. 0 can be turned on by sysctl -w net.ipv4.vs.sync_version=0
 *
 * Definitions  Message: is a complete datagram
 *              Sync_conn: is a part of a Message
 *              Param Data is an option to a Sync_conn.
 *
 * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
 *
 * ip_vs_sync:  sync connection info from master load balancer to backups
 *              through multicast
 *
 * Changes:
 *      Alexandre Cassen        :       Added master & backup support at a time.
 *      Alexandre Cassen        :       Added SyncID support for incoming sync
 *                                      messages filtering.
 *      Justin Ossevoort        :       Fix endian problem on sync message size.
 *      Hans Schillstrom        :       Added Version 1: i.e. IPv6,
 *                                      Persistence support, fwmark and time-out.
 */

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

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/inetdevice.h>
#include <linux/net.h>
#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/skbuff.h>
#include <linux/in.h>
#include <linux/igmp.h>                 /* for ip_mc_join_group */
#include <linux/udp.h>
#include <linux/err.h>
#include <linux/kthread.h>
#include <linux/wait.h>
#include <linux/kernel.h>

#include <asm/unaligned.h>              /* Used for ntoh_seq and hton_seq */

#include <net/ip.h>
#include <net/sock.h>

#include <net/ip_vs.h>

#define IP_VS_SYNC_GROUP 0xe0000051    /* multicast addr - 224.0.0.81 */
#define IP_VS_SYNC_PORT  8848          /* multicast port */

#define SYNC_PROTO_VER  1               /* Protocol version in header */

/*
 *      IPVS sync connection entry
 *      Version 0, i.e. original version.
 */
struct ip_vs_sync_conn_v0 {
        __u8                    reserved;

        /* Protocol, addresses and port numbers */
        __u8                    protocol;       /* Which protocol (TCP/UDP) */
        __be16                  cport;
        __be16                  vport;
        __be16                  dport;
        __be32                  caddr;          /* client address */
        __be32                  vaddr;          /* virtual address */
        __be32                  daddr;          /* destination address */

        /* Flags and state transition */
        __be16                  flags;          /* status flags */
        __be16                  state;          /* state info */

        /* The sequence options start here */
};

struct ip_vs_sync_conn_options {
        struct ip_vs_seq        in_seq;         /* incoming seq. struct */
        struct ip_vs_seq        out_seq;        /* outgoing seq. struct */
};

/*
     Sync Connection format (sync_conn)

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    Type       |    Protocol   | Ver.  |        Size           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             Flags                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            State              |         cport                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            vport              |         dport                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             fwmark                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             timeout  (in sec.)                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      |                        IP-Addresses  (v4 or v6)               |
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  Optional Parameters.
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Param. Type    | Param. Length |   Param. data                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
      |                              ...                              |
      |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                               | Param Type    | Param. Length |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Param  data                         |
      |         Last Param data should be padded for 32 bit alignment |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/

/*
 *  Type 0, IPv4 sync connection format
 */
struct ip_vs_sync_v4 {
        __u8                    type;
        __u8                    protocol;       /* Which protocol (TCP/UDP) */
        __be16                  ver_size;       /* Version msb 4 bits */
        /* Flags and state transition */
        __be32                  flags;          /* status flags */
        __be16                  state;          /* state info   */
        /* Protocol, addresses and port numbers */
        __be16                  cport;
        __be16                  vport;
        __be16                  dport;
        __be32                  fwmark;         /* Firewall mark from skb */
        __be32                  timeout;        /* cp timeout */
        __be32                  caddr;          /* client address */
        __be32                  vaddr;          /* virtual address */
        __be32                  daddr;          /* destination address */
        /* The sequence options start here */
        /* PE data padded to 32bit alignment after seq. options */
};
/*
 * Type 2 messages IPv6
 */
struct ip_vs_sync_v6 {
        __u8                    type;
        __u8                    protocol;       /* Which protocol (TCP/UDP) */
        __be16                  ver_size;       /* Version msb 4 bits */
        /* Flags and state transition */
        __be32                  flags;          /* status flags */
        __be16                  state;          /* state info   */
        /* Protocol, addresses and port numbers */
        __be16                  cport;
        __be16                  vport;
        __be16                  dport;
        __be32                  fwmark;         /* Firewall mark from skb */
        __be32                  timeout;        /* cp timeout */
        struct in6_addr         caddr;          /* client address */
        struct in6_addr         vaddr;          /* virtual address */
        struct in6_addr         daddr;          /* destination address */
        /* The sequence options start here */
        /* PE data padded to 32bit alignment after seq. options */
};

union ip_vs_sync_conn {
        struct ip_vs_sync_v4    v4;
        struct ip_vs_sync_v6    v6;
};

/* Bits in Type field in above */
#define STYPE_INET6             0
#define STYPE_F_INET6           (1 << STYPE_INET6)

#define SVER_SHIFT              12              /* Shift to get version */
#define SVER_MASK               0x0fff          /* Mask to strip version */

#define IPVS_OPT_SEQ_DATA       1
#define IPVS_OPT_PE_DATA        2
#define IPVS_OPT_PE_NAME        3
#define IPVS_OPT_PARAM          7

#define IPVS_OPT_F_SEQ_DATA     (1 << (IPVS_OPT_SEQ_DATA-1))
#define IPVS_OPT_F_PE_DATA      (1 << (IPVS_OPT_PE_DATA-1))
#define IPVS_OPT_F_PE_NAME      (1 << (IPVS_OPT_PE_NAME-1))
#define IPVS_OPT_F_PARAM        (1 << (IPVS_OPT_PARAM-1))

struct ip_vs_sync_thread_data {
        struct net *net;
        struct socket *sock;
        char *buf;
};

/* Version 0 definition of packet sizes */
#define SIMPLE_CONN_SIZE  (sizeof(struct ip_vs_sync_conn_v0))
#define FULL_CONN_SIZE  \
(sizeof(struct ip_vs_sync_conn_v0) + sizeof(struct ip_vs_sync_conn_options))


/*
  The master mulitcasts messages (Datagrams) to the backup load balancers
  in the following format.

 Version 1:
  Note, first byte should be Zero, so ver 0 receivers will drop the packet.

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      0        |    SyncID     |            Size               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Count Conns  |    Version    |    Reserved, set to Zero      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      |                    IPVS Sync Connection (1)                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                            .                                  |
      ~                            .                                  ~
      |                            .                                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      |                    IPVS Sync Connection (n)                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 Version 0 Header
       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Count Conns  |    SyncID     |            Size               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    IPVS Sync Connection (1)                   |
*/

#define SYNC_MESG_HEADER_LEN    4
#define MAX_CONNS_PER_SYNCBUFF  255 /* nr_conns in ip_vs_sync_mesg is 8 bit */

/* Version 0 header */
struct ip_vs_sync_mesg_v0 {
        __u8                    nr_conns;
        __u8                    syncid;
        __u16                   size;

        /* ip_vs_sync_conn entries start here */
};

/* Version 1 header */
struct ip_vs_sync_mesg {
        __u8                    reserved;       /* must be zero */
        __u8                    syncid;
        __u16                   size;
        __u8                    nr_conns;
        __s8                    version;        /* SYNC_PROTO_VER  */
        __u16                   spare;
        /* ip_vs_sync_conn entries start here */
};

struct ip_vs_sync_buff {
        struct list_head        list;
        unsigned long           firstuse;

        /* pointers for the message data */
        struct ip_vs_sync_mesg  *mesg;
        unsigned char           *head;
        unsigned char           *end;
};

/* multicast addr */
static struct sockaddr_in mcast_addr = {
        .sin_family             = AF_INET,
        .sin_port               = cpu_to_be16(IP_VS_SYNC_PORT),
        .sin_addr.s_addr        = cpu_to_be32(IP_VS_SYNC_GROUP),
};

/*
 * Copy of struct ip_vs_seq
 * From unaligned network order to aligned host order
 */
static void ntoh_seq(struct ip_vs_seq *no, struct ip_vs_seq *ho)
{
        ho->init_seq       = get_unaligned_be32(&no->init_seq);
        ho->delta          = get_unaligned_be32(&no->delta);
        ho->previous_delta = get_unaligned_be32(&no->previous_delta);
}

/*
 * Copy of struct ip_vs_seq
 * From Aligned host order to unaligned network order
 */
static void hton_seq(struct ip_vs_seq *ho, struct ip_vs_seq *no)
{
        put_unaligned_be32(ho->init_seq, &no->init_seq);
        put_unaligned_be32(ho->delta, &no->delta);
        put_unaligned_be32(ho->previous_delta, &no->previous_delta);
}

static inline struct ip_vs_sync_buff *sb_dequeue(struct netns_ipvs *ipvs)
{
        struct ip_vs_sync_buff *sb;

        spin_lock_bh(&ipvs->sync_lock);
        if (list_empty(&ipvs->sync_queue)) {
                sb = NULL;
        } else {
                sb = list_entry(ipvs->sync_queue.next,
                                struct ip_vs_sync_buff,
                                list);
                list_del(&sb->list);
        }
        spin_unlock_bh(&ipvs->sync_lock);

        return sb;
}

/*
 * Create a new sync buffer for Version 1 proto.
 */
static inline struct ip_vs_sync_buff *
ip_vs_sync_buff_create(struct netns_ipvs *ipvs)
{
        struct ip_vs_sync_buff *sb;

        if (!(sb=kmalloc(sizeof(struct ip_vs_sync_buff), GFP_ATOMIC)))
                return NULL;

        sb->mesg = kmalloc(ipvs->send_mesg_maxlen, GFP_ATOMIC);
        if (!sb->mesg) {
                kfree(sb);
                return NULL;
        }
        sb->mesg->reserved = 0;  /* old nr_conns i.e. must be zeo now */
        sb->mesg->version = SYNC_PROTO_VER;
        sb->mesg->syncid = ipvs->master_syncid;
        sb->mesg->size = sizeof(struct ip_vs_sync_mesg);
        sb->mesg->nr_conns = 0;
        sb->mesg->spare = 0;
        sb->head = (unsigned char *)sb->mesg + sizeof(struct ip_vs_sync_mesg);
        sb->end = (unsigned char *)sb->mesg + ipvs->send_mesg_maxlen;

        sb->firstuse = jiffies;
        return sb;
}

static inline void ip_vs_sync_buff_release(struct ip_vs_sync_buff *sb)
{
        kfree(sb->mesg);
        kfree(sb);
}

static inline void sb_queue_tail(struct netns_ipvs *ipvs)
{
        struct ip_vs_sync_buff *sb = ipvs->sync_buff;

        spin_lock(&ipvs->sync_lock);
        if (ipvs->sync_state & IP_VS_STATE_MASTER)
                list_add_tail(&sb->list, &ipvs->sync_queue);
        else
                ip_vs_sync_buff_release(sb);
        spin_unlock(&ipvs->sync_lock);
}

/*
 *      Get the current sync buffer if it has been created for more
 *      than the specified time or the specified time is zero.
 */
static inline struct ip_vs_sync_buff *
get_curr_sync_buff(struct netns_ipvs *ipvs, unsigned long time)
{
        struct ip_vs_sync_buff *sb;

        spin_lock_bh(&ipvs->sync_buff_lock);
        if (ipvs->sync_buff &&
            time_after_eq(jiffies - ipvs->sync_buff->firstuse, time)) {
                sb = ipvs->sync_buff;
                ipvs->sync_buff = NULL;
        } else
                sb = NULL;
        spin_unlock_bh(&ipvs->sync_buff_lock);
        return sb;
}

/*
 * Switch mode from sending version 0 or 1
 *  - must handle sync_buf
 */
void ip_vs_sync_switch_mode(struct net *net, int mode)
{
        struct netns_ipvs *ipvs = net_ipvs(net);

        if (!(ipvs->sync_state & IP_VS_STATE_MASTER))
                return;
        if (mode == sysctl_sync_ver(ipvs) || !ipvs->sync_buff)
                return;

        spin_lock_bh(&ipvs->sync_buff_lock);
        /* Buffer empty ? then let buf_create do the job  */
        if (ipvs->sync_buff->mesg->size <=  sizeof(struct ip_vs_sync_mesg)) {
                kfree(ipvs->sync_buff);
                ipvs->sync_buff = NULL;
        } else {
                spin_lock_bh(&ipvs->sync_lock);
                if (ipvs->sync_state & IP_VS_STATE_MASTER)
                        list_add_tail(&ipvs->sync_buff->list,
                                      &ipvs->sync_queue);
                else
                        ip_vs_sync_buff_release(ipvs->sync_buff);
                spin_unlock_bh(&ipvs->sync_lock);
        }
        spin_unlock_bh(&ipvs->sync_buff_lock);
}

/*
 * Create a new sync buffer for Version 0 proto.
 */
static inline struct ip_vs_sync_buff *
ip_vs_sync_buff_create_v0(struct netns_ipvs *ipvs)
{
        struct ip_vs_sync_buff *sb;
        struct ip_vs_sync_mesg_v0 *mesg;

        if (!(sb=kmalloc(sizeof(struct ip_vs_sync_buff), GFP_ATOMIC)))
                return NULL;

        sb->mesg = kmalloc(ipvs->send_mesg_maxlen, GFP_ATOMIC);
        if (!sb->mesg) {
                kfree(sb);
                return NULL;
        }
        mesg = (struct ip_vs_sync_mesg_v0 *)sb->mesg;
        mesg->nr_conns = 0;
        mesg->syncid = ipvs->master_syncid;
        mesg->size = sizeof(struct ip_vs_sync_mesg_v0);
        sb->head = (unsigned char *)mesg + sizeof(struct ip_vs_sync_mesg_v0);
        sb->end = (unsigned char *)mesg + ipvs->send_mesg_maxlen;
        sb->firstuse = jiffies;
        return sb;
}

/*
 *      Version 0 , could be switched in by sys_ctl.
 *      Add an ip_vs_conn information into the current sync_buff.
 */
void ip_vs_sync_conn_v0(struct net *net, struct ip_vs_conn *cp)
{
        struct netns_ipvs *ipvs = net_ipvs(net);
        struct ip_vs_sync_mesg_v0 *m;
        struct ip_vs_sync_conn_v0 *s;
        int len;

        if (unlikely(cp->af != AF_INET))
                return;
        /* Do not sync ONE PACKET */
        if (cp->flags & IP_VS_CONN_F_ONE_PACKET)
                return;

        spin_lock(&ipvs->sync_buff_lock);
        if (!ipvs->sync_buff) {
                ipvs->sync_buff =
                        ip_vs_sync_buff_create_v0(ipvs);
                if (!ipvs->sync_buff) {
                        spin_unlock(&ipvs->sync_buff_lock);
                        pr_err("ip_vs_sync_buff_create failed.\n");
                        return;
                }
        }

        len = (cp->flags & IP_VS_CONN_F_SEQ_MASK) ? FULL_CONN_SIZE :
                SIMPLE_CONN_SIZE;
        m = (struct ip_vs_sync_mesg_v0 *)ipvs->sync_buff->mesg;
        s = (struct ip_vs_sync_conn_v0 *)ipvs->sync_buff->head;

        /* copy members */
        s->reserved = 0;
        s->protocol = cp->protocol;
        s->cport = cp->cport;
        s->vport = cp->vport;
        s->dport = cp->dport;
        s->caddr = cp->caddr.ip;
        s->vaddr = cp->vaddr.ip;
        s->daddr = cp->daddr.ip;
        s->flags = htons(cp->flags & ~IP_VS_CONN_F_HASHED);
        s->state = htons(cp->state);
        if (cp->flags & IP_VS_CONN_F_SEQ_MASK) {
                struct ip_vs_sync_conn_options *opt =
                        (struct ip_vs_sync_conn_options *)&s[1];
                memcpy(opt, &cp->in_seq, sizeof(*opt));
        }

        m->nr_conns++;
        m->size += len;
        ipvs->sync_buff->head += len;

        /* check if there is a space for next one */
        if (ipvs->sync_buff->head + FULL_CONN_SIZE > ipvs->sync_buff->end) {
                sb_queue_tail(ipvs);
                ipvs->sync_buff = NULL;
        }
        spin_unlock(&ipvs->sync_buff_lock);

        /* synchronize its controller if it has */
        if (cp->control)
                ip_vs_sync_conn(net, cp->control);
}

/*
 *      Add an ip_vs_conn information into the current sync_buff.
 *      Called by ip_vs_in.
 *      Sending Version 1 messages
 */
void ip_vs_sync_conn(struct net *net, struct ip_vs_conn *cp)
{
        struct netns_ipvs *ipvs = net_ipvs(net);
        struct ip_vs_sync_mesg *m;
        union ip_vs_sync_conn *s;
        __u8 *p;
        unsigned int len, pe_name_len, pad;

        /* Handle old version of the protocol */
        if (sysctl_sync_ver(ipvs) == 0) {
                ip_vs_sync_conn_v0(net, cp);
                return;
        }
        /* Do not sync ONE PACKET */
        if (cp->flags & IP_VS_CONN_F_ONE_PACKET)
                goto control;
sloop:
        /* Sanity checks */
        pe_name_len = 0;
        if (cp->pe_data_len) {
                if (!cp->pe_data || !cp->dest) {
                        IP_VS_ERR_RL("SYNC, connection pe_data invalid\n");
                        return;
                }
                pe_name_len = strnlen(cp->pe->name, IP_VS_PENAME_MAXLEN);
        }

        spin_lock(&ipvs->sync_buff_lock);

#ifdef CONFIG_IP_VS_IPV6
        if (cp->af == AF_INET6)
                len = sizeof(struct ip_vs_sync_v6);
        else
#endif
                len = sizeof(struct ip_vs_sync_v4);

        if (cp->flags & IP_VS_CONN_F_SEQ_MASK)
                len += sizeof(struct ip_vs_sync_conn_options) + 2;

        if (cp->pe_data_len)
                len += cp->pe_data_len + 2;     /* + Param hdr field */
        if (pe_name_len)
                len += pe_name_len + 2;

        /* check if there is a space for this one  */
        pad = 0;
        if (ipvs->sync_buff) {
                pad = (4 - (size_t)ipvs->sync_buff->head) & 3;
                if (ipvs->sync_buff->head + len + pad > ipvs->sync_buff->end) {
                        sb_queue_tail(ipvs);
                        ipvs->sync_buff = NULL;
                        pad = 0;
                }
        }

        if (!ipvs->sync_buff) {
                ipvs->sync_buff = ip_vs_sync_buff_create(ipvs);
                if (!ipvs->sync_buff) {
                        spin_unlock(&ipvs->sync_buff_lock);
                        pr_err("ip_vs_sync_buff_create failed.\n");
                        return;
                }
        }

        m = ipvs->sync_buff->mesg;
        p = ipvs->sync_buff->head;
        ipvs->sync_buff->head += pad + len;
        m->size += pad + len;
        /* Add ev. padding from prev. sync_conn */
        while (pad--)
                *(p++) = 0;

        s = (union ip_vs_sync_conn *)p;

        /* Set message type  & copy members */
        s->v4.type = (cp->af == AF_INET6 ? STYPE_F_INET6 : 0);
        s->v4.ver_size = htons(len & SVER_MASK);        /* Version 0 */
        s->v4.flags = htonl(cp->flags & ~IP_VS_CONN_F_HASHED);
        s->v4.state = htons(cp->state);
        s->v4.protocol = cp->protocol;
        s->v4.cport = cp->cport;
        s->v4.vport = cp->vport;
        s->v4.dport = cp->dport;
        s->v4.fwmark = htonl(cp->fwmark);
        s->v4.timeout = htonl(cp->timeout / HZ);
        m->nr_conns++;

#ifdef CONFIG_IP_VS_IPV6
        if (cp->af == AF_INET6) {
                p += sizeof(struct ip_vs_sync_v6);
                ipv6_addr_copy(&s->v6.caddr, &cp->caddr.in6);
                ipv6_addr_copy(&s->v6.vaddr, &cp->vaddr.in6);
                ipv6_addr_copy(&s->v6.daddr, &cp->daddr.in6);
        } else
#endif
        {
                p += sizeof(struct ip_vs_sync_v4);      /* options ptr */
                s->v4.caddr = cp->caddr.ip;
                s->v4.vaddr = cp->vaddr.ip;
                s->v4.daddr = cp->daddr.ip;
        }
        if (cp->flags & IP_VS_CONN_F_SEQ_MASK) {
                *(p++) = IPVS_OPT_SEQ_DATA;
                *(p++) = sizeof(struct ip_vs_sync_conn_options);
                hton_seq((struct ip_vs_seq *)p, &cp->in_seq);
                p += sizeof(struct ip_vs_seq);
                hton_seq((struct ip_vs_seq *)p, &cp->out_seq);
                p += sizeof(struct ip_vs_seq);
        }
        /* Handle pe data */
        if (cp->pe_data_len && cp->pe_data) {
                *(p++) = IPVS_OPT_PE_DATA;
                *(p++) = cp->pe_data_len;
                memcpy(p, cp->pe_data, cp->pe_data_len);
                p += cp->pe_data_len;
                if (pe_name_len) {
                        /* Add PE_NAME */
                        *(p++) = IPVS_OPT_PE_NAME;
                        *(p++) = pe_name_len;
                        memcpy(p, cp->pe->name, pe_name_len);
                        p += pe_name_len;
                }
        }

        spin_unlock(&ipvs->sync_buff_lock);

control:
        /* synchronize its controller if it has */
        cp = cp->control;
        if (!cp)
                return;
        /*
         * Reduce sync rate for templates
         * i.e only increment in_pkts for Templates.
         */
        if (cp->flags & IP_VS_CONN_F_TEMPLATE) {
                int pkts = atomic_add_return(1, &cp->in_pkts);

                if (pkts % sysctl_sync_period(ipvs) != 1)
                        return;
        }
        goto sloop;
}

/*
 *  fill_param used by version 1
 */
static inline int
ip_vs_conn_fill_param_sync(struct net *net, int af, union ip_vs_sync_conn *sc,
                           struct ip_vs_conn_param *p,
                           __u8 *pe_data, unsigned int pe_data_len,
                           __u8 *pe_name, unsigned int pe_name_len)
{
#ifdef CONFIG_IP_VS_IPV6
        if (af == AF_INET6)
                ip_vs_conn_fill_param(net, af, sc->v6.protocol,
                                      (const union nf_inet_addr *)&sc->v6.caddr,
                                      sc->v6.cport,
                                      (const union nf_inet_addr *)&sc->v6.vaddr,
                                      sc->v6.vport, p);
        else
#endif
                ip_vs_conn_fill_param(net, af, sc->v4.protocol,
                                      (const union nf_inet_addr *)&sc->v4.caddr,
                                      sc->v4.cport,
                                      (const union nf_inet_addr *)&sc->v4.vaddr,
                                      sc->v4.vport, p);
        /* Handle pe data */
        if (pe_data_len) {
                if (pe_name_len) {
                        char buff[IP_VS_PENAME_MAXLEN+1];

                        memcpy(buff, pe_name, pe_name_len);
                        buff[pe_name_len]=0;
                        p->pe = __ip_vs_pe_getbyname(buff);
                        if (!p->pe) {
                                IP_VS_DBG(3, "BACKUP, no %s engine found/loaded\n",
                                             buff);
                                return 1;
                        }
                } else {
                        IP_VS_ERR_RL("BACKUP, Invalid PE parameters\n");
                        return 1;
                }

                p->pe_data = kmemdup(pe_data, pe_data_len, GFP_ATOMIC);
                if (!p->pe_data) {
                        if (p->pe->module)
                                module_put(p->pe->module);
                        return -ENOMEM;
                }
                p->pe_data_len = pe_data_len;
        }
        return 0;
}

/*
 *  Connection Add / Update.
 *  Common for version 0 and 1 reception of backup sync_conns.
 *  Param: ...
 *         timeout is in sec.
 */
static void ip_vs_proc_conn(struct net *net, struct ip_vs_conn_param *param,
                            unsigned int flags, unsigned int state,
                            unsigned int protocol, unsigned int type,
                            const union nf_inet_addr *daddr, __be16 dport,
                            unsigned long timeout, __u32 fwmark,
                            struct ip_vs_sync_conn_options *opt)
{
        struct ip_vs_dest *dest;
        struct ip_vs_conn *cp;
        struct netns_ipvs *ipvs = net_ipvs(net);

        if (!(flags & IP_VS_CONN_F_TEMPLATE))
                cp = ip_vs_conn_in_get(param);
        else
                cp = ip_vs_ct_in_get(param);

        if (cp && param->pe_data)       /* Free pe_data */
                kfree(param->pe_data);
        if (!cp) {
                /*
                 * Find the appropriate destination for the connection.
                 * If it is not found the connection will remain unbound
                 * but still handled.
                 */
                dest = ip_vs_find_dest(net, type, daddr, dport, param->vaddr,
                                       param->vport, protocol, fwmark);

                /*  Set the approprite ativity flag */
                if (protocol == IPPROTO_TCP) {
                        if (state != IP_VS_TCP_S_ESTABLISHED)
                                flags |= IP_VS_CONN_F_INACTIVE;
                        else
                                flags &= ~IP_VS_CONN_F_INACTIVE;
                } else if (protocol == IPPROTO_SCTP) {
                        if (state != IP_VS_SCTP_S_ESTABLISHED)
                                flags |= IP_VS_CONN_F_INACTIVE;
                        else
                                flags &= ~IP_VS_CONN_F_INACTIVE;
                }
                cp = ip_vs_conn_new(param, daddr, dport, flags, dest, fwmark);
                if (dest)
                        atomic_dec(&dest->refcnt);
                if (!cp) {
                        if (param->pe_data)
                                kfree(param->pe_data);
                        IP_VS_DBG(2, "BACKUP, add new conn. failed\n");
                        return;
                }
        } else if (!cp->dest) {
                dest = ip_vs_try_bind_dest(cp);
                if (dest)
                        atomic_dec(&dest->refcnt);
        } else if ((cp->dest) && (cp->protocol == IPPROTO_TCP) &&
                (cp->state != state)) {
                /* update active/inactive flag for the connection */
                dest = cp->dest;
                if (!(cp->flags & IP_VS_CONN_F_INACTIVE) &&
                        (state != IP_VS_TCP_S_ESTABLISHED)) {
                        atomic_dec(&dest->activeconns);
                        atomic_inc(&dest->inactconns);
                        cp->flags |= IP_VS_CONN_F_INACTIVE;
                } else if ((cp->flags & IP_VS_CONN_F_INACTIVE) &&
                        (state == IP_VS_TCP_S_ESTABLISHED)) {
                        atomic_inc(&dest->activeconns);
                        atomic_dec(&dest->inactconns);
                        cp->flags &= ~IP_VS_CONN_F_INACTIVE;
                }
        } else if ((cp->dest) && (cp->protocol == IPPROTO_SCTP) &&
                (cp->state != state)) {
                dest = cp->dest;
                if (!(cp->flags & IP_VS_CONN_F_INACTIVE) &&
                (state != IP_VS_SCTP_S_ESTABLISHED)) {
                        atomic_dec(&dest->activeconns);
                        atomic_inc(&dest->inactconns);
                        cp->flags &= ~IP_VS_CONN_F_INACTIVE;
                }
        }

        if (opt)
                memcpy(&cp->in_seq, opt, sizeof(*opt));
        atomic_set(&cp->in_pkts, sysctl_sync_threshold(ipvs));
        cp->state = state;
        cp->old_state = cp->state;
        /*
         * For Ver 0 messages style
         *  - Not possible to recover the right timeout for templates
         *  - can not find the right fwmark
         *    virtual service. If needed, we can do it for
         *    non-fwmark persistent services.
         * Ver 1 messages style.
         *  - No problem.
         */
        if (timeout) {
                if (timeout > MAX_SCHEDULE_TIMEOUT / HZ)
                        timeout = MAX_SCHEDULE_TIMEOUT / HZ;
                cp->timeout = timeout*HZ;
        } else {
                struct ip_vs_proto_data *pd;

                pd = ip_vs_proto_data_get(net, protocol);
                if (!(flags & IP_VS_CONN_F_TEMPLATE) && pd && pd->timeout_table)
                        cp->timeout = pd->timeout_table[state];
                else
                        cp->timeout = (3*60*HZ);
        }
        ip_vs_conn_put(cp);
}

/*
 *  Process received multicast message for Version 0
 */
static void ip_vs_process_message_v0(struct net *net, const char *buffer,
                                     const size_t buflen)
{
        struct ip_vs_sync_mesg_v0 *m = (struct ip_vs_sync_mesg_v0 *)buffer;
        struct ip_vs_sync_conn_v0 *s;
        struct ip_vs_sync_conn_options *opt;
        struct ip_vs_protocol *pp;
        struct ip_vs_conn_param param;
        char *p;
        int i;

        p = (char *)buffer + sizeof(struct ip_vs_sync_mesg_v0);
        for (i=0; i<m->nr_conns; i++) {
                unsigned flags, state;

                if (p + SIMPLE_CONN_SIZE > buffer+buflen) {
                        IP_VS_ERR_RL("BACKUP v0, bogus conn\n");
                        return;
                }
                s = (struct ip_vs_sync_conn_v0 *) p;
                flags = ntohs(s->flags) | IP_VS_CONN_F_SYNC;
                flags &= ~IP_VS_CONN_F_HASHED;
                if (flags & IP_VS_CONN_F_SEQ_MASK) {
                        opt = (struct ip_vs_sync_conn_options *)&s[1];
                        p += FULL_CONN_SIZE;
                        if (p > buffer+buflen) {
                                IP_VS_ERR_RL("BACKUP v0, Dropping buffer bogus conn options\n");
                                return;
                        }
                } else {
                        opt = NULL;
                        p += SIMPLE_CONN_SIZE;
                }

                state = ntohs(s->state);
                if (!(flags & IP_VS_CONN_F_TEMPLATE)) {
                        pp = ip_vs_proto_get(s->protocol);
                        if (!pp) {
                                IP_VS_DBG(2, "BACKUP v0, Unsupported protocol %u\n",
                                        s->protocol);
                                continue;
                        }
                        if (state >= pp->num_states) {
                                IP_VS_DBG(2, "BACKUP v0, Invalid %s state %u\n",
                                        pp->name, state);
                                continue;
                        }
                } else {
                        /* protocol in templates is not used for state/timeout */
                        if (state > 0) {
                                IP_VS_DBG(2, "BACKUP v0, Invalid template state %u\n",
                                        state);
                                state = 0;
                        }
                }

                ip_vs_conn_fill_param(net, AF_INET, s->protocol,
                                      (const union nf_inet_addr *)&s->caddr,
                                      s->cport,
                                      (const union nf_inet_addr *)&s->vaddr,
                                      s->vport, &param);

                /* Send timeout as Zero */
                ip_vs_proc_conn(net, &param, flags, state, s->protocol, AF_INET,
                                (union nf_inet_addr *)&s->daddr, s->dport,
                                0, 0, opt);
        }
}

/*
 * Handle options
 */
static inline int ip_vs_proc_seqopt(__u8 *p, unsigned int plen,
                                    __u32 *opt_flags,
                                    struct ip_vs_sync_conn_options *opt)
{
        struct ip_vs_sync_conn_options *topt;

        topt = (struct ip_vs_sync_conn_options *)p;

        if (plen != sizeof(struct ip_vs_sync_conn_options)) {
                IP_VS_DBG(2, "BACKUP, bogus conn options length\n");
                return -EINVAL;
        }
        if (*opt_flags & IPVS_OPT_F_SEQ_DATA) {
                IP_VS_DBG(2, "BACKUP, conn options found twice\n");
                return -EINVAL;
        }
        ntoh_seq(&topt->in_seq, &opt->in_seq);
        ntoh_seq(&topt->out_seq, &opt->out_seq);
        *opt_flags |= IPVS_OPT_F_SEQ_DATA;
        return 0;
}

static int ip_vs_proc_str(__u8 *p, unsigned int plen, unsigned int *data_len,
                          __u8 **data, unsigned int maxlen,
                          __u32 *opt_flags, __u32 flag)
{
        if (plen > maxlen) {
                IP_VS_DBG(2, "BACKUP, bogus par.data len > %d\n", maxlen);
                return -EINVAL;
        }
        if (*opt_flags & flag) {
                IP_VS_DBG(2, "BACKUP, Par.data found twice 0x%x\n", flag);
                return -EINVAL;
        }
        *data_len = plen;
        *data = p;
        *opt_flags |= flag;
        return 0;
}
/*
 *   Process a Version 1 sync. connection
 */
static inline int ip_vs_proc_sync_conn(struct net *net, __u8 *p, __u8 *msg_end)
{
        struct ip_vs_sync_conn_options opt;
        union  ip_vs_sync_conn *s;
        struct ip_vs_protocol *pp;
        struct ip_vs_conn_param param;
        __u32 flags;
        unsigned int af, state, pe_data_len=0, pe_name_len=0;
        __u8 *pe_data=NULL, *pe_name=NULL;
        __u32 opt_flags=0;
        int retc=0;

        s = (union ip_vs_sync_conn *) p;

        if (s->v6.type & STYPE_F_INET6) {
#ifdef CONFIG_IP_VS_IPV6
                af = AF_INET6;
                p += sizeof(struct ip_vs_sync_v6);
#else
                IP_VS_DBG(3,"BACKUP, IPv6 msg received, and IPVS is not compiled for IPv6\n");
                retc = 10;
                goto out;
#endif
        } else if (!s->v4.type) {
                af = AF_INET;
                p += sizeof(struct ip_vs_sync_v4);
        } else {
                return -10;
        }
        if (p > msg_end)
                return -20;

        /* Process optional params check Type & Len. */
        while (p < msg_end) {
                int ptype;
                int plen;

                if (p+2 > msg_end)
                        return -30;
                ptype = *(p++);
                plen  = *(p++);

                if (!plen || ((p + plen) > msg_end))
                        return -40;
                /* Handle seq option  p = param data */
                switch (ptype & ~IPVS_OPT_F_PARAM) {
                case IPVS_OPT_SEQ_DATA:
                        if (ip_vs_proc_seqopt(p, plen, &opt_flags, &opt))
                                return -50;
                        break;

                case IPVS_OPT_PE_DATA:
                        if (ip_vs_proc_str(p, plen, &pe_data_len, &pe_data,
                                           IP_VS_PEDATA_MAXLEN, &opt_flags,
                                           IPVS_OPT_F_PE_DATA))
                                return -60;
                        break;

                case IPVS_OPT_PE_NAME:

                        if (ip_vs_proc_str(p, plen,&pe_name_len, &pe_name,
                                           IP_VS_PENAME_MAXLEN, &opt_flags,
                                           IPVS_OPT_F_PE_NAME))
                                return -70;
                        break;

                default:
                        /* Param data mandatory ? */
                        if (!(ptype & IPVS_OPT_F_PARAM)) {
                                IP_VS_DBG(3, "BACKUP, Unknown mandatory param %d found\n",
                                          ptype & ~IPVS_OPT_F_PARAM);
                                retc = 20;
                                goto out;
                        }
                }
                p += plen;  /* Next option */
        }

        /* Get flags and Mask off unsupported */
        flags  = ntohl(s->v4.flags) & IP_VS_CONN_F_BACKUP_MASK;
        flags |= IP_VS_CONN_F_SYNC;
        state = ntohs(s->v4.state);

        if (!(flags & IP_VS_CONN_F_TEMPLATE)) {
                pp = ip_vs_proto_get(s->v4.protocol);
                if (!pp) {
                        IP_VS_DBG(3,"BACKUP, Unsupported protocol %u\n",
                                s->v4.protocol);
                        retc = 30;
                        goto out;
                }
                if (state >= pp->num_states) {
                        IP_VS_DBG(3, "BACKUP, Invalid %s state %u\n",
                                pp->name, state);
                        retc = 40;
                        goto out;
                }
        } else {
                /* protocol in templates is not used for state/timeout */
                if (state > 0) {
                        IP_VS_DBG(3, "BACKUP, Invalid template state %u\n",
                                state);
                        state = 0;
                }
        }
        if (ip_vs_conn_fill_param_sync(net, af, s, &param, pe_data,
                                       pe_data_len, pe_name, pe_name_len)) {
                retc = 50;
                goto out;
        }
        /* If only IPv4, just silent skip IPv6 */
        if (af == AF_INET)
                ip_vs_proc_conn(net, &param, flags, state, s->v4.protocol, af,
                                (union nf_inet_addr *)&s->v4.daddr, s->v4.dport,
                                ntohl(s->v4.timeout), ntohl(s->v4.fwmark),
                                (opt_flags & IPVS_OPT_F_SEQ_DATA ? &opt : NULL)
                                );
#ifdef CONFIG_IP_VS_IPV6
        else
                ip_vs_proc_conn(net, &param, flags, state, s->v6.protocol, af,
                                (union nf_inet_addr *)&s->v6.daddr, s->v6.dport,
                                ntohl(s->v6.timeout), ntohl(s->v6.fwmark),
                                (opt_flags & IPVS_OPT_F_SEQ_DATA ? &opt : NULL)
                                );
#endif
        return 0;
        /* Error exit */
out:
        IP_VS_DBG(2, "BACKUP, Single msg dropped err:%d\n", retc);
        return retc;

}
/*
 *      Process received multicast message and create the corresponding
 *      ip_vs_conn entries.
 *      Handles Version 0 & 1
 */
static void ip_vs_process_message(struct net *net, __u8 *buffer,
                                  const size_t buflen)
{
        struct netns_ipvs *ipvs = net_ipvs(net);
        struct ip_vs_sync_mesg *m2 = (struct ip_vs_sync_mesg *)buffer;
        __u8 *p, *msg_end;
        int i, nr_conns;

        if (buflen < sizeof(struct ip_vs_sync_mesg_v0)) {
                IP_VS_DBG(2, "BACKUP, message header too short\n");
                return;
        }
        /* Convert size back to host byte order */
        m2->size = ntohs(m2->size);

        if (buflen != m2->size) {
                IP_VS_DBG(2, "BACKUP, bogus message size\n");
                return;
        }
        /* SyncID sanity check */
        if (ipvs->backup_syncid != 0 && m2->syncid != ipvs->backup_syncid) {
                IP_VS_DBG(7, "BACKUP, Ignoring syncid = %d\n", m2->syncid);
                return;
        }
        /* Handle version 1  message */
        if ((m2->version == SYNC_PROTO_VER) && (m2->reserved == 0)
            && (m2->spare == 0)) {

                msg_end = buffer + sizeof(struct ip_vs_sync_mesg);
                nr_conns = m2->nr_conns;

                for (i=0; i<nr_conns; i++) {
                        union ip_vs_sync_conn *s;
                        unsigned size;
                        int retc;

                        p = msg_end;
                        if (p + sizeof(s->v4) > buffer+buflen) {
                                IP_VS_ERR_RL("BACKUP, Dropping buffer, to small\n");
                                return;
                        }
                        s = (union ip_vs_sync_conn *)p;
                        size = ntohs(s->v4.ver_size) & SVER_MASK;
                        msg_end = p + size;
                        /* Basic sanity checks */
                        if (msg_end  > buffer+buflen) {
                                IP_VS_ERR_RL("BACKUP, Dropping buffer, msg > buffer\n");
                                return;
                        }
                        if (ntohs(s->v4.ver_size) >> SVER_SHIFT) {
                                IP_VS_ERR_RL("BACKUP, Dropping buffer, Unknown version %d\n",
                                              ntohs(s->v4.ver_size) >> SVER_SHIFT);
                                return;
                        }
                        /* Process a single sync_conn */
                        retc = ip_vs_proc_sync_conn(net, p, msg_end);
                        if (retc < 0) {
                                IP_VS_ERR_RL("BACKUP, Dropping buffer, Err: %d in decoding\n",
                                             retc);
                                return;
                        }
                        /* Make sure we have 32 bit alignment */
                        msg_end = p + ((size + 3) & ~3);
                }
        } else {
                /* Old type of message */
                ip_vs_process_message_v0(net, buffer, buflen);
                return;
        }
}


/*
 *      Setup loopback of outgoing multicasts on a sending socket
 */
static void set_mcast_loop(struct sock *sk, u_char loop)
{
        struct inet_sock *inet = inet_sk(sk);

        /* setsockopt(sock, SOL_IP, IP_MULTICAST_LOOP, &loop, sizeof(loop)); */
        lock_sock(sk);
        inet->mc_loop = loop ? 1 : 0;
        release_sock(sk);
}

/*
 *      Specify TTL for outgoing multicasts on a sending socket
 */
static void set_mcast_ttl(struct sock *sk, u_char ttl)
{
        struct inet_sock *inet = inet_sk(sk);

        /* setsockopt(sock, SOL_IP, IP_MULTICAST_TTL, &ttl, sizeof(ttl)); */
        lock_sock(sk);
        inet->mc_ttl = ttl;
        release_sock(sk);
}

/*
 *      Specifiy default interface for outgoing multicasts
 */
static int set_mcast_if(struct sock *sk, char *ifname)
{
        struct net_device *dev;
        struct inet_sock *inet = inet_sk(sk);
        struct net *net = sock_net(sk);

        dev = __dev_get_by_name(net, ifname);
        if (!dev)
                return -ENODEV;

        if (sk->sk_bound_dev_if && dev->ifindex != sk->sk_bound_dev_if)
                return -EINVAL;

        lock_sock(sk);
        inet->mc_index = dev->ifindex;
        /*  inet->mc_addr  = 0; */
        release_sock(sk);

        return 0;
}


/*
 *      Set the maximum length of sync message according to the
 *      specified interface's MTU.
 */
static int set_sync_mesg_maxlen(struct net *net, int sync_state)
{
        struct netns_ipvs *ipvs = net_ipvs(net);
        struct net_device *dev;
        int num;

        if (sync_state == IP_VS_STATE_MASTER) {
                dev = __dev_get_by_name(net, ipvs->master_mcast_ifn);
                if (!dev)
                        return -ENODEV;

                num = (dev->mtu - sizeof(struct iphdr) -
                       sizeof(struct udphdr) -
                       SYNC_MESG_HEADER_LEN - 20) / SIMPLE_CONN_SIZE;
                ipvs->send_mesg_maxlen = SYNC_MESG_HEADER_LEN +
                        SIMPLE_CONN_SIZE * min(num, MAX_CONNS_PER_SYNCBUFF);
                IP_VS_DBG(7, "setting the maximum length of sync sending "
                          "message %d.\n", ipvs->send_mesg_maxlen);
        } else if (sync_state == IP_VS_STATE_BACKUP) {
                dev = __dev_get_by_name(net, ipvs->backup_mcast_ifn);
                if (!dev)
                        return -ENODEV;

                ipvs->recv_mesg_maxlen = dev->mtu -
                        sizeof(struct iphdr) - sizeof(struct udphdr);
                IP_VS_DBG(7, "setting the maximum length of sync receiving "
                          "message %d.\n", ipvs->recv_mesg_maxlen);
        }

        return 0;
}


/*
 *      Join a multicast group.
 *      the group is specified by a class D multicast address 224.0.0.0/8
 *      in the in_addr structure passed in as a parameter.
 */
static int
join_mcast_group(struct sock *sk, struct in_addr *addr, char *ifname)
{
        struct net *net = sock_net(sk);
        struct ip_mreqn mreq;
        struct net_device *dev;
        int ret;

        memset(&mreq, 0, sizeof(mreq));
        memcpy(&mreq.imr_multiaddr, addr, sizeof(struct in_addr));

        dev = __dev_get_by_name(net, ifname);
        if (!dev)
                return -ENODEV;
        if (sk->sk_bound_dev_if && dev->ifindex != sk->sk_bound_dev_if)
                return -EINVAL;

        mreq.imr_ifindex = dev->ifindex;

        lock_sock(sk);
        ret = ip_mc_join_group(sk, &mreq);
        release_sock(sk);

        return ret;
}


static int bind_mcastif_addr(struct socket *sock, char *ifname)
{
        struct net *net = sock_net(sock->sk);
        struct net_device *dev;
        __be32 addr;
        struct sockaddr_in sin;

        dev = __dev_get_by_name(net, ifname);
        if (!dev)
                return -ENODEV;

        addr = inet_select_addr(dev, 0, RT_SCOPE_UNIVERSE);
        if (!addr)
                pr_err("You probably need to specify IP address on "
                       "multicast interface.\n");

        IP_VS_DBG(7, "binding socket with (%s) %pI4\n",
                  ifname, &addr);

        /* Now bind the socket with the address of multicast interface */
        sin.sin_family       = AF_INET;
        sin.sin_addr.s_addr  = addr;
        sin.sin_port         = 0;

        return sock->ops->bind(sock, (struct sockaddr*)&sin, sizeof(sin));
}

/*
 *      Set up sending multicast socket over UDP
 */
static struct socket *make_send_sock(struct net *net)
{
        struct netns_ipvs *ipvs = net_ipvs(net);
        struct socket *sock;
        int result;

        /* First create a socket move it to right name space later */
        result = sock_create_kern(PF_INET, SOCK_DGRAM, IPPROTO_UDP, &sock);
        if (result < 0) {
                pr_err("Error during creation of socket; terminating\n");
                return ERR_PTR(result);
        }
        /*
         * Kernel sockets that are a part of a namespace, should not
         * hold a reference to a namespace in order to allow to stop it.
         * After sk_change_net should be released using sk_release_kernel.
         */
        sk_change_net(sock->sk, net);
        result = set_mcast_if(sock->sk, ipvs->master_mcast_ifn);
        if (result < 0) {
                pr_err("Error setting outbound mcast interface\n");
                goto error;
        }

        set_mcast_loop(sock->sk, 0);
        set_mcast_ttl(sock->sk, 1);

        result = bind_mcastif_addr(sock, ipvs->master_mcast_ifn);
        if (result < 0) {
                pr_err("Error binding address of the mcast interface\n");
                goto error;
        }

        result = sock->ops->connect(sock, (struct sockaddr *) &mcast_addr,
                        sizeof(struct sockaddr), 0);
        if (result < 0) {
                pr_err("Error connecting to the multicast addr\n");
                goto error;
        }

        return sock;

error:
        sk_release_kernel(sock->sk);
        return ERR_PTR(result);
}


/*
 *      Set up receiving multicast socket over UDP
 */
static struct socket *make_receive_sock(struct net *net)
{
        struct netns_ipvs *ipvs = net_ipvs(net);
        struct socket *sock;
        int result;

        /* First create a socket */
        result = sock_create_kern(PF_INET, SOCK_DGRAM, IPPROTO_UDP, &sock);
        if (result < 0) {
                pr_err("Error during creation of socket; terminating\n");
                return ERR_PTR(result);
        }
        /*
         * Kernel sockets that are a part of a namespace, should not
         * hold a reference to a namespace in order to allow to stop it.
         * After sk_change_net should be released using sk_release_kernel.
         */
        sk_change_net(sock->sk, net);
        /* it is equivalent to the REUSEADDR option in user-space */
        sock->sk->sk_reuse = 1;

        result = sock->ops->bind(sock, (struct sockaddr *) &mcast_addr,
                        sizeof(struct sockaddr));
        if (result < 0) {
                pr_err("Error binding to the multicast addr\n");
                goto error;
        }

        /* join the multicast group */
        result = join_mcast_group(sock->sk,
                        (struct in_addr *) &mcast_addr.sin_addr,
                        ipvs->backup_mcast_ifn);
        if (result < 0) {
                pr_err("Error joining to the multicast group\n");
                goto error;
        }

        return sock;

error:
        sk_release_kernel(sock->sk);
        return ERR_PTR(result);
}


static int
ip_vs_send_async(struct socket *sock, const char *buffer, const size_t length)
{
        struct msghdr   msg = {.msg_flags = MSG_DONTWAIT|MSG_NOSIGNAL};
        struct kvec     iov;
        int             len;

        EnterFunction(7);
        iov.iov_base     = (void *)buffer;
        iov.iov_len      = length;

        len = kernel_sendmsg(sock, &msg, &iov, 1, (size_t)(length));

        LeaveFunction(7);
        return len;
}

static void
ip_vs_send_sync_msg(struct socket *sock, struct ip_vs_sync_mesg *msg)
{
        int msize;

        msize = msg->size;

        /* Put size in network byte order */
        msg->size = htons(msg->size);

        if (ip_vs_send_async(sock, (char *)msg, msize) != msize)
                pr_err("ip_vs_send_async error\n");
}

static int
ip_vs_receive(struct socket *sock, char *buffer, const size_t buflen)
{
        struct msghdr           msg = {NULL,};
        struct kvec             iov;
        int                     len;

        EnterFunction(7);

        /* Receive a packet */
        iov.iov_base     = buffer;
        iov.iov_len      = (size_t)buflen;

        len = kernel_recvmsg(sock, &msg, &iov, 1, buflen, 0);

        if (len < 0)
                return -1;

        LeaveFunction(7);
        return len;
}


static int sync_thread_master(void *data)
{
        struct ip_vs_sync_thread_data *tinfo = data;
        struct netns_ipvs *ipvs = net_ipvs(tinfo->net);
        struct ip_vs_sync_buff *sb;

        pr_info("sync thread started: state = MASTER, mcast_ifn = %s, "
                "syncid = %d\n",
                ipvs->master_mcast_ifn, ipvs->master_syncid);

        while (!kthread_should_stop()) {
                while ((sb = sb_dequeue(ipvs))) {
                        ip_vs_send_sync_msg(tinfo->sock, sb->mesg);
                        ip_vs_sync_buff_release(sb);
                }

                /* check if entries stay in ipvs->sync_buff for 2 seconds */
                sb = get_curr_sync_buff(ipvs, 2 * HZ);
                if (sb) {
                        ip_vs_send_sync_msg(tinfo->sock, sb->mesg);
                        ip_vs_sync_buff_release(sb);
                }

                schedule_timeout_interruptible(HZ);
        }

        /* clean up the sync_buff queue */
        while ((sb = sb_dequeue(ipvs)))
                ip_vs_sync_buff_release(sb);

        /* clean up the current sync_buff */
        sb = get_curr_sync_buff(ipvs, 0);
        if (sb)
                ip_vs_sync_buff_release(sb);

        /* release the sending multicast socket */
        sk_release_kernel(tinfo->sock->sk);
        kfree(tinfo);

        return 0;
}


static int sync_thread_backup(void *data)
{
        struct ip_vs_sync_thread_data *tinfo = data;
        struct netns_ipvs *ipvs = net_ipvs(tinfo->net);
        int len;

        pr_info("sync thread started: state = BACKUP, mcast_ifn = %s, "
                "syncid = %d\n",
                ipvs->backup_mcast_ifn, ipvs->backup_syncid);

        while (!kthread_should_stop()) {
                wait_event_interruptible(*sk_sleep(tinfo->sock->sk),
                         !skb_queue_empty(&tinfo->sock->sk->sk_receive_queue)
                         || kthread_should_stop());

                /* do we have data now? */
                while (!skb_queue_empty(&(tinfo->sock->sk->sk_receive_queue))) {
                        len = ip_vs_receive(tinfo->sock, tinfo->buf,
                                        ipvs->recv_mesg_maxlen);
                        if (len <= 0) {
                                pr_err("receiving message error\n");
                                break;
                        }

                        /* disable bottom half, because it accesses the data
                           shared by softirq while getting/creating conns */
                        local_bh_disable();
                        ip_vs_process_message(tinfo->net, tinfo->buf, len);
                        local_bh_enable();
                }
        }

        /* release the sending multicast socket */
        sk_release_kernel(tinfo->sock->sk);
        kfree(tinfo->buf);
        kfree(tinfo);

        return 0;
}


int start_sync_thread(struct net *net, int state, char *mcast_ifn, __u8 syncid)
{
        struct ip_vs_sync_thread_data *tinfo;
        struct task_struct **realtask, *task;
        struct socket *sock;
        struct netns_ipvs *ipvs = net_ipvs(net);
        char *name, *buf = NULL;
        int (*threadfn)(void *data);
        int result = -ENOMEM;

        IP_VS_DBG(7, "%s(): pid %d\n", __func__, task_pid_nr(current));
        IP_VS_DBG(7, "Each ip_vs_sync_conn entry needs %Zd bytes\n",
                  sizeof(struct ip_vs_sync_conn_v0));

        if (state == IP_VS_STATE_MASTER) {
                if (ipvs->master_thread)
                        return -EEXIST;

                strlcpy(ipvs->master_mcast_ifn, mcast_ifn,
                        sizeof(ipvs->master_mcast_ifn));
                ipvs->master_syncid = syncid;
                realtask = &ipvs->master_thread;
                name = "ipvs_master:%d";
                threadfn = sync_thread_master;
                sock = make_send_sock(net);
        } else if (state == IP_VS_STATE_BACKUP) {
                if (ipvs->backup_thread)
                        return -EEXIST;

                strlcpy(ipvs->backup_mcast_ifn, mcast_ifn,
                        sizeof(ipvs->backup_mcast_ifn));
                ipvs->backup_syncid = syncid;
                realtask = &ipvs->backup_thread;
                name = "ipvs_backup:%d";
                threadfn = sync_thread_backup;
                sock = make_receive_sock(net);
        } else {
                return -EINVAL;
        }

        if (IS_ERR(sock)) {
                result = PTR_ERR(sock);
                goto out;
        }

        set_sync_mesg_maxlen(net, state);
        if (state == IP_VS_STATE_BACKUP) {
                buf = kmalloc(ipvs->recv_mesg_maxlen, GFP_KERNEL);
                if (!buf)
                        goto outsocket;
        }

        tinfo = kmalloc(sizeof(*tinfo), GFP_KERNEL);
        if (!tinfo)
                goto outbuf;

        tinfo->net = net;
        tinfo->sock = sock;
        tinfo->buf = buf;

        task = kthread_run(threadfn, tinfo, name, ipvs->gen);
        if (IS_ERR(task)) {
                result = PTR_ERR(task);
                goto outtinfo;
        }

        /* mark as active */
        *realtask = task;
        ipvs->sync_state |= state;

        /* increase the module use count */
        ip_vs_use_count_inc();

        return 0;

outtinfo:
        kfree(tinfo);
outbuf:
        kfree(buf);
outsocket:
        sk_release_kernel(sock->sk);
out:
        return result;
}


int stop_sync_thread(struct net *net, int state)
{
        struct netns_ipvs *ipvs = net_ipvs(net);
        int retc = -EINVAL;

        IP_VS_DBG(7, "%s(): pid %d\n", __func__, task_pid_nr(current));

        if (state == IP_VS_STATE_MASTER) {
                if (!ipvs->master_thread)
                        return -ESRCH;

                pr_info("stopping master sync thread %d ...\n",
                        task_pid_nr(ipvs->master_thread));

                /*
                 * The lock synchronizes with sb_queue_tail(), so that we don't
                 * add sync buffers to the queue, when we are already in
                 * progress of stopping the master sync daemon.
                 */

                spin_lock_bh(&ipvs->sync_lock);
                ipvs->sync_state &= ~IP_VS_STATE_MASTER;
                spin_unlock_bh(&ipvs->sync_lock);
                retc = kthread_stop(ipvs->master_thread);
                ipvs->master_thread = NULL;
        } else if (state == IP_VS_STATE_BACKUP) {
                if (!ipvs->backup_thread)
                        return -ESRCH;

                pr_info("stopping backup sync thread %d ...\n",
                        task_pid_nr(ipvs->backup_thread));

                ipvs->sync_state &= ~IP_VS_STATE_BACKUP;
                retc = kthread_stop(ipvs->backup_thread);
                ipvs->backup_thread = NULL;
        }

        /* decrease the module use count */
        ip_vs_use_count_dec();

        return retc;
}

/*
 * Initialize data struct for each netns
 */
int __net_init __ip_vs_sync_init(struct net *net)
{
        struct netns_ipvs *ipvs = net_ipvs(net);

        INIT_LIST_HEAD(&ipvs->sync_queue);
        spin_lock_init(&ipvs->sync_lock);
        spin_lock_init(&ipvs->sync_buff_lock);

        ipvs->sync_mcast_addr.sin_family = AF_INET;
        ipvs->sync_mcast_addr.sin_port = cpu_to_be16(IP_VS_SYNC_PORT);
        ipvs->sync_mcast_addr.sin_addr.s_addr = cpu_to_be32(IP_VS_SYNC_GROUP);
        return 0;
}

void __ip_vs_sync_cleanup(struct net *net)
{
        int retc;

        retc = stop_sync_thread(net, IP_VS_STATE_MASTER);
        if (retc && retc != -ESRCH)
                pr_err("Failed to stop Master Daemon\n");

        retc = stop_sync_thread(net, IP_VS_STATE_BACKUP);
        if (retc && retc != -ESRCH)
                pr_err("Failed to stop Backup Daemon\n");
}

int __init ip_vs_sync_init(void)
{
        return 0;
}

void ip_vs_sync_cleanup(void)
{
}