text: /*
   * 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:     $Id: ip_vs_sync.c,v 1.13 2003/06/08 09:31:19 wensong Exp $
   *
   * 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.
   */
  
  #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 <net/ip.h>
  #include <net/sock.h>
  #include <asm/uaccess.h>                /* for get_fs and set_fs */
  
  #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 */
  
  
  /*
   *	IPVS sync connection entry
   */
  struct ip_vs_sync_conn {
  	__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 */
  };
  
  struct ip_vs_sync_thread_data {
  	struct completion *startup;
  	int state;
  };
  
  #define IP_VS_SYNC_CONN_TIMEOUT (3*60*HZ)
  #define SIMPLE_CONN_SIZE  (sizeof(struct ip_vs_sync_conn))
  #define FULL_CONN_SIZE  \
  (sizeof(struct ip_vs_sync_conn) + sizeof(struct ip_vs_sync_conn_options))
  
  
  /*
    The master mulitcasts messages to the backup load balancers in the
    following format.
  
         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)                   |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                            .                                  |
        |                            .                                  |
        |                            .                                  |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        |                    IPVS Sync Connection (n)                   |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  */
  
  #define SYNC_MESG_HEADER_LEN	4
  
  struct ip_vs_sync_mesg {
  	__u8                    nr_conns;
  	__u8                    syncid;
  	__u16                   size;
  
  	/* ip_vs_sync_conn entries start here */
  };
  
  /* the maximum length of sync (sending/receiving) message */
  static int sync_send_mesg_maxlen;
  static int sync_recv_mesg_maxlen;
  
  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;
  };
  
  
  /* the sync_buff list head and the lock */
  static LIST_HEAD(ip_vs_sync_queue);
  static DEFINE_SPINLOCK(ip_vs_sync_lock);
  
  /* current sync_buff for accepting new conn entries */
  static struct ip_vs_sync_buff   *curr_sb = NULL;
  static DEFINE_SPINLOCK(curr_sb_lock);
  
  /* ipvs sync daemon state */
  volatile int ip_vs_sync_state = IP_VS_STATE_NONE;
  volatile int ip_vs_master_syncid = 0;
  volatile int ip_vs_backup_syncid = 0;
  
  /* multicast interface name */
  char ip_vs_master_mcast_ifn[IP_VS_IFNAME_MAXLEN];
  char ip_vs_backup_mcast_ifn[IP_VS_IFNAME_MAXLEN];
  
  /* multicast addr */
  static struct sockaddr_in mcast_addr;
  
  
  static inline void sb_queue_tail(struct ip_vs_sync_buff *sb)
  {
  	spin_lock(&ip_vs_sync_lock);
  	list_add_tail(&sb->list, &ip_vs_sync_queue);
  	spin_unlock(&ip_vs_sync_lock);
  }
  
  static inline struct ip_vs_sync_buff * sb_dequeue(void)
  {
  	struct ip_vs_sync_buff *sb;
  
  	spin_lock_bh(&ip_vs_sync_lock);
  	if (list_empty(&ip_vs_sync_queue)) {
  		sb = NULL;
  	} else {
  		sb = list_entry(ip_vs_sync_queue.next,
  				struct ip_vs_sync_buff,
  				list);
  		list_del(&sb->list);
  	}
  	spin_unlock_bh(&ip_vs_sync_lock);
  
  	return sb;
  }
  
  static inline struct ip_vs_sync_buff * ip_vs_sync_buff_create(void)
  {
  	struct ip_vs_sync_buff *sb;
  
  	if (!(sb=kmalloc(sizeof(struct ip_vs_sync_buff), GFP_ATOMIC)))
  		return NULL;
  
  	if (!(sb->mesg=kmalloc(sync_send_mesg_maxlen, GFP_ATOMIC))) {
  		kfree(sb);
  		return NULL;
  	}
  	sb->mesg->nr_conns = 0;
  	sb->mesg->syncid = ip_vs_master_syncid;
  	sb->mesg->size = 4;
  	sb->head = (unsigned char *)sb->mesg + 4;
  	sb->end = (unsigned char *)sb->mesg + sync_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);
  }
  
  /*
   *	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(unsigned long time)
  {
  	struct ip_vs_sync_buff *sb;
  
  	spin_lock_bh(&curr_sb_lock);
  	if (curr_sb && (time == 0 ||
  			time_before(jiffies - curr_sb->firstuse, time))) {
  		sb = curr_sb;
  		curr_sb = NULL;
  	} else
  		sb = NULL;
  	spin_unlock_bh(&curr_sb_lock);
  	return sb;
  }
  
  
  /*
   *      Add an ip_vs_conn information into the current sync_buff.
   *      Called by ip_vs_in.
   */
  void ip_vs_sync_conn(struct ip_vs_conn *cp)
  {
  	struct ip_vs_sync_mesg *m;
  	struct ip_vs_sync_conn *s;
  	int len;
  
  	spin_lock(&curr_sb_lock);
  	if (!curr_sb) {
  		if (!(curr_sb=ip_vs_sync_buff_create())) {
  			spin_unlock(&curr_sb_lock);
  			IP_VS_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 = curr_sb->mesg;
  	s = (struct ip_vs_sync_conn *)curr_sb->head;
  
  	/* copy members */
  	s->protocol = cp->protocol;
  	s->cport = cp->cport;
  	s->vport = cp->vport;
  	s->dport = cp->dport;
  	s->caddr = cp->caddr;
  	s->vaddr = cp->vaddr;
  	s->daddr = cp->daddr;
  	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;
  	curr_sb->head += len;
  
  	/* check if there is a space for next one */
  	if (curr_sb->head+FULL_CONN_SIZE > curr_sb->end) {
  		sb_queue_tail(curr_sb);
  		curr_sb = NULL;
  	}
  	spin_unlock(&curr_sb_lock);
  
  	/* synchronize its controller if it has */
  	if (cp->control)
  		ip_vs_sync_conn(cp->control);
  }
  
  
  /*
   *      Process received multicast message and create the corresponding
   *      ip_vs_conn entries.
   */
  static void ip_vs_process_message(const char *buffer, const size_t buflen)
  {
  	struct ip_vs_sync_mesg *m = (struct ip_vs_sync_mesg *)buffer;
  	struct ip_vs_sync_conn *s;
  	struct ip_vs_sync_conn_options *opt;
  	struct ip_vs_conn *cp;
  	char *p;
  	int i;
  
  	/* Convert size back to host byte order */
  	m->size = ntohs(m->size);
  
  	if (buflen != m->size) {
  		IP_VS_ERR("bogus message\n");
  		return;
  	}
  
  	/* SyncID sanity check */
  	if (ip_vs_backup_syncid != 0 && m->syncid != ip_vs_backup_syncid) {
  		IP_VS_DBG(7, "Ignoring incoming msg with syncid = %d\n",
  			  m->syncid);
  		return;
  	}
  
  	p = (char *)buffer + sizeof(struct ip_vs_sync_mesg);
  	for (i=0; i<m->nr_conns; i++) {
  		unsigned flags;
  
  		s = (struct ip_vs_sync_conn *)p;
  		flags = ntohs(s->flags);
  		if (!(flags & IP_VS_CONN_F_TEMPLATE))
  			cp = ip_vs_conn_in_get(s->protocol,
  					       s->caddr, s->cport,
  					       s->vaddr, s->vport);
  		else
  			cp = ip_vs_ct_in_get(s->protocol,
  					       s->caddr, s->cport,
  					       s->vaddr, s->vport);
  		if (!cp) {
  			cp = ip_vs_conn_new(s->protocol,
  					    s->caddr, s->cport,
  					    s->vaddr, s->vport,
  					    s->daddr, s->dport,
  					    flags, NULL);
  			if (!cp) {
  				IP_VS_ERR("ip_vs_conn_new failed\n");
  				return;
  			}
  			cp->state = ntohs(s->state);
  		} else if (!cp->dest) {
  			/* it is an entry created by the synchronization */
  			cp->state = ntohs(s->state);
  			cp->flags = flags | IP_VS_CONN_F_HASHED;
  		}	/* Note that we don't touch its state and flags
  			   if it is a normal entry. */
  
  		if (flags & IP_VS_CONN_F_SEQ_MASK) {
  			opt = (struct ip_vs_sync_conn_options *)&s[1];
  			memcpy(&cp->in_seq, opt, sizeof(*opt));
  			p += FULL_CONN_SIZE;
  		} else
  			p += SIMPLE_CONN_SIZE;
  
  		atomic_set(&cp->in_pkts, sysctl_ip_vs_sync_threshold[0]);
  		cp->timeout = IP_VS_SYNC_CONN_TIMEOUT;
  		ip_vs_conn_put(cp);
  
  		if (p > buffer+buflen) {
  			IP_VS_ERR("bogus message\n");
  			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);
  
  	if ((dev = __dev_get_by_name(ifname)) == NULL)
  		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(int sync_state)
  {
  	struct net_device *dev;
  	int num;
  
  	if (sync_state == IP_VS_STATE_MASTER) {
  		if ((dev = __dev_get_by_name(ip_vs_master_mcast_ifn)) == NULL)
  			return -ENODEV;
  
  		num = (dev->mtu - sizeof(struct iphdr) -
  		       sizeof(struct udphdr) -
  		       SYNC_MESG_HEADER_LEN - 20) / SIMPLE_CONN_SIZE;
  		sync_send_mesg_maxlen =
  			SYNC_MESG_HEADER_LEN + SIMPLE_CONN_SIZE * num;
  		IP_VS_DBG(7, "setting the maximum length of sync sending "
  			  "message %d.\n", sync_send_mesg_maxlen);
  	} else if (sync_state == IP_VS_STATE_BACKUP) {
  		if ((dev = __dev_get_by_name(ip_vs_backup_mcast_ifn)) == NULL)
  			return -ENODEV;
  
  		sync_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", sync_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 ip_mreqn mreq;
  	struct net_device *dev;
  	int ret;
  
  	memset(&mreq, 0, sizeof(mreq));
  	memcpy(&mreq.imr_multiaddr, addr, sizeof(struct in_addr));
  
  	if ((dev = __dev_get_by_name(ifname)) == NULL)
  		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_device *dev;
  	__be32 addr;
  	struct sockaddr_in sin;
  
  	if ((dev = __dev_get_by_name(ifname)) == NULL)
  		return -ENODEV;
  
  	addr = inet_select_addr(dev, 0, RT_SCOPE_UNIVERSE);
  	if (!addr)
  		IP_VS_ERR("You probably need to specify IP address on "
  			  "multicast interface.\n");
  
  	IP_VS_DBG(7, "binding socket with (%s) %u.%u.%u.%u\n",
  		  ifname, NIPQUAD(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(void)
  {
  	struct socket *sock;
  
  	/* First create a socket */
  	if (sock_create_kern(PF_INET, SOCK_DGRAM, IPPROTO_UDP, &sock) < 0) {
  		IP_VS_ERR("Error during creation of socket; terminating\n");
  		return NULL;
  	}
  
  	if (set_mcast_if(sock->sk, ip_vs_master_mcast_ifn) < 0) {
  		IP_VS_ERR("Error setting outbound mcast interface\n");
  		goto error;
  	}
  
  	set_mcast_loop(sock->sk, 0);
  	set_mcast_ttl(sock->sk, 1);
  
  	if (bind_mcastif_addr(sock, ip_vs_master_mcast_ifn) < 0) {
  		IP_VS_ERR("Error binding address of the mcast interface\n");
  		goto error;
  	}
  
  	if (sock->ops->connect(sock,
  			       (struct sockaddr*)&mcast_addr,
  			       sizeof(struct sockaddr), 0) < 0) {
  		IP_VS_ERR("Error connecting to the multicast addr\n");
  		goto error;
  	}
  
  	return sock;
  
    error:
  	sock_release(sock);
  	return NULL;
  }
  
  
  /*
   *      Set up receiving multicast socket over UDP
   */
  static struct socket * make_receive_sock(void)
  {
  	struct socket *sock;
  
  	/* First create a socket */
  	if (sock_create_kern(PF_INET, SOCK_DGRAM, IPPROTO_UDP, &sock) < 0) {
  		IP_VS_ERR("Error during creation of socket; terminating\n");
  		return NULL;
  	}
  
  	/* it is equivalent to the REUSEADDR option in user-space */
  	sock->sk->sk_reuse = 1;
  
  	if (sock->ops->bind(sock,
  			    (struct sockaddr*)&mcast_addr,
  			    sizeof(struct sockaddr)) < 0) {
  		IP_VS_ERR("Error binding to the multicast addr\n");
  		goto error;
  	}
  
  	/* join the multicast group */
  	if (join_mcast_group(sock->sk,
  			     (struct in_addr*)&mcast_addr.sin_addr,
  			     ip_vs_backup_mcast_ifn) < 0) {
  		IP_VS_ERR("Error joining to the multicast group\n");
  		goto error;
  	}
  
  	return sock;
  
    error:
  	sock_release(sock);
  	return NULL;
  }
  
  
  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)
  		IP_VS_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 DECLARE_WAIT_QUEUE_HEAD(sync_wait);
  static pid_t sync_master_pid = 0;
  static pid_t sync_backup_pid = 0;
  
  static DECLARE_WAIT_QUEUE_HEAD(stop_sync_wait);
  static int stop_master_sync = 0;
  static int stop_backup_sync = 0;
  
  static void sync_master_loop(void)
  {
  	struct socket *sock;
  	struct ip_vs_sync_buff *sb;
  
  	/* create the sending multicast socket */
  	sock = make_send_sock();
  	if (!sock)
  		return;
  
  	IP_VS_INFO("sync thread started: state = MASTER, mcast_ifn = %s, "
  		   "syncid = %d\n",
  		   ip_vs_master_mcast_ifn, ip_vs_master_syncid);
  
  	for (;;) {
  		while ((sb=sb_dequeue())) {
  			ip_vs_send_sync_msg(sock, sb->mesg);
  			ip_vs_sync_buff_release(sb);
  		}
  
  		/* check if entries stay in curr_sb for 2 seconds */
  		if ((sb = get_curr_sync_buff(2*HZ))) {
  			ip_vs_send_sync_msg(sock, sb->mesg);
  			ip_vs_sync_buff_release(sb);
  		}
  
  		if (stop_master_sync)
  			break;
  
  		msleep_interruptible(1000);
  	}
  
  	/* clean up the sync_buff queue */
  	while ((sb=sb_dequeue())) {
  		ip_vs_sync_buff_release(sb);
  	}
  
  	/* clean up the current sync_buff */
  	if ((sb = get_curr_sync_buff(0))) {
  		ip_vs_sync_buff_release(sb);
  	}
  
  	/* release the sending multicast socket */
  	sock_release(sock);
  }
  
  
  static void sync_backup_loop(void)
  {
  	struct socket *sock;
  	char *buf;
  	int len;
  
  	if (!(buf = kmalloc(sync_recv_mesg_maxlen, GFP_ATOMIC))) {
  		IP_VS_ERR("sync_backup_loop: kmalloc error\n");
  		return;
  	}
  
  	/* create the receiving multicast socket */
  	sock = make_receive_sock();
  	if (!sock)
  		goto out;
  
  	IP_VS_INFO("sync thread started: state = BACKUP, mcast_ifn = %s, "
  		   "syncid = %d\n",
  		   ip_vs_backup_mcast_ifn, ip_vs_backup_syncid);
  
  	for (;;) {
  		/* do you have data now? */
  		while (!skb_queue_empty(&(sock->sk->sk_receive_queue))) {
  			if ((len =
  			     ip_vs_receive(sock, buf,
  					   sync_recv_mesg_maxlen)) <= 0) {
  				IP_VS_ERR("receiving message error\n");
  				break;
  			}
  			/* disable bottom half, because it accessed the data
  			   shared by softirq while getting/creating conns */
  			local_bh_disable();
  			ip_vs_process_message(buf, len);
  			local_bh_enable();
  		}
  
  		if (stop_backup_sync)
  			break;
  
  		msleep_interruptible(1000);
  	}
  
  	/* release the sending multicast socket */
  	sock_release(sock);
  
    out:
  	kfree(buf);
  }
  
  
  static void set_sync_pid(int sync_state, pid_t sync_pid)
  {
  	if (sync_state == IP_VS_STATE_MASTER)
  		sync_master_pid = sync_pid;
  	else if (sync_state == IP_VS_STATE_BACKUP)
  		sync_backup_pid = sync_pid;
  }
  
  static void set_stop_sync(int sync_state, int set)
  {
  	if (sync_state == IP_VS_STATE_MASTER)
  		stop_master_sync = set;
  	else if (sync_state == IP_VS_STATE_BACKUP)
  		stop_backup_sync = set;
  	else {
  		stop_master_sync = set;
  		stop_backup_sync = set;
  	}
  }
  
  static int sync_thread(void *startup)
  {
  	DECLARE_WAITQUEUE(wait, current);
  	mm_segment_t oldmm;
  	int state;
  	const char *name;
  	struct ip_vs_sync_thread_data *tinfo = startup;
  
  	/* increase the module use count */
  	ip_vs_use_count_inc();
  
  	if (ip_vs_sync_state & IP_VS_STATE_MASTER && !sync_master_pid) {
  		state = IP_VS_STATE_MASTER;
  		name = "ipvs_syncmaster";
  	} else if (ip_vs_sync_state & IP_VS_STATE_BACKUP && !sync_backup_pid) {
  		state = IP_VS_STATE_BACKUP;
  		name = "ipvs_syncbackup";
  	} else {
  		IP_VS_BUG();
  		ip_vs_use_count_dec();
  		return -EINVAL;
  	}
  
  	daemonize(name);
  
  	oldmm = get_fs();
  	set_fs(KERNEL_DS);
  
  	/* Block all signals */
  	spin_lock_irq(&current->sighand->siglock);
  	siginitsetinv(&current->blocked, 0);
  	recalc_sigpending();
  	spin_unlock_irq(&current->sighand->siglock);
  
  	/* set the maximum length of sync message */
  	set_sync_mesg_maxlen(state);
  
  	/* set up multicast address */
  	mcast_addr.sin_family = AF_INET;
  	mcast_addr.sin_port = htons(IP_VS_SYNC_PORT);
  	mcast_addr.sin_addr.s_addr = htonl(IP_VS_SYNC_GROUP);
  
  	add_wait_queue(&sync_wait, &wait);
  
  	set_sync_pid(state, current->pid);
  	complete(tinfo->startup);
  
  	/*
  	 * once we call the completion queue above, we should
  	 * null out that reference, since its allocated on the
  	 * stack of the creating kernel thread
  	 */
  	tinfo->startup = NULL;
  
  	/* processing master/backup loop here */
  	if (state == IP_VS_STATE_MASTER)
  		sync_master_loop();
  	else if (state == IP_VS_STATE_BACKUP)
  		sync_backup_loop();
  	else IP_VS_BUG();
  
  	remove_wait_queue(&sync_wait, &wait);
  
  	/* thread exits */
  
  	/*
  	 * If we weren't explicitly stopped, then we
  	 * exited in error, and should undo our state
  	 */
  	if ((!stop_master_sync) && (!stop_backup_sync))
  		ip_vs_sync_state -= tinfo->state;
  
  	set_sync_pid(state, 0);
  	IP_VS_INFO("sync thread stopped!\n");
  
  	set_fs(oldmm);
  
  	/* decrease the module use count */
  	ip_vs_use_count_dec();
  
  	set_stop_sync(state, 0);
  	wake_up(&stop_sync_wait);
  
  	/*
  	 * we need to free the structure that was allocated
  	 * for us in start_sync_thread
  	 */
  	kfree(tinfo);
  	return 0;
  }
  
  
  static int fork_sync_thread(void *startup)
  {
  	pid_t pid;
  
  	/* fork the sync thread here, then the parent process of the
  	   sync thread is the init process after this thread exits. */
    repeat:
  	if ((pid = kernel_thread(sync_thread, startup, 0)) < 0) {
  		IP_VS_ERR("could not create sync_thread due to %d... "
  			  "retrying.\n", pid);
  		msleep_interruptible(1000);
  		goto repeat;
  	}
  
  	return 0;
  }
  
  
  int start_sync_thread(int state, char *mcast_ifn, __u8 syncid)
  {
  	DECLARE_COMPLETION_ONSTACK(startup);
  	pid_t pid;
  	struct ip_vs_sync_thread_data *tinfo;
  
  	if ((state == IP_VS_STATE_MASTER && sync_master_pid) ||
  	    (state == IP_VS_STATE_BACKUP && sync_backup_pid))
  		return -EEXIST;
  
  	/*
  	 * Note that tinfo will be freed in sync_thread on exit
  	 */
  	tinfo = kmalloc(sizeof(struct ip_vs_sync_thread_data), GFP_KERNEL);
  	if (!tinfo)
  		return -ENOMEM;
  
  	IP_VS_DBG(7, "%s: pid %d\n", __FUNCTION__, current->pid);
  	IP_VS_DBG(7, "Each ip_vs_sync_conn entry need %Zd bytes\n",
  		  sizeof(struct ip_vs_sync_conn));
  
  	ip_vs_sync_state |= state;
  	if (state == IP_VS_STATE_MASTER) {
  		strlcpy(ip_vs_master_mcast_ifn, mcast_ifn,
  			sizeof(ip_vs_master_mcast_ifn));
  		ip_vs_master_syncid = syncid;
  	} else {
  		strlcpy(ip_vs_backup_mcast_ifn, mcast_ifn,
  			sizeof(ip_vs_backup_mcast_ifn));
  		ip_vs_backup_syncid = syncid;
  	}
  
  	tinfo->state = state;
  	tinfo->startup = &startup;
  
    repeat:
  	if ((pid = kernel_thread(fork_sync_thread, tinfo, 0)) < 0) {
  		IP_VS_ERR("could not create fork_sync_thread due to %d... "
  			  "retrying.\n", pid);
  		msleep_interruptible(1000);
  		goto repeat;
  	}
  
  	wait_for_completion(&startup);
  
  	return 0;
  }
  
  
  int stop_sync_thread(int state)
  {
  	DECLARE_WAITQUEUE(wait, current);
  
  	if ((state == IP_VS_STATE_MASTER && !sync_master_pid) ||
  	    (state == IP_VS_STATE_BACKUP && !sync_backup_pid))
  		return -ESRCH;
  
  	IP_VS_DBG(7, "%s: pid %d\n", __FUNCTION__, current->pid);
  	IP_VS_INFO("stopping sync thread %d ...\n",
  		   (state == IP_VS_STATE_MASTER) ?
  		   sync_master_pid : sync_backup_pid);
  
  	__set_current_state(TASK_UNINTERRUPTIBLE);
  	add_wait_queue(&stop_sync_wait, &wait);
  	set_stop_sync(state, 1);
  	ip_vs_sync_state -= state;
  	wake_up(&sync_wait);
  	schedule();
  	__set_current_state(TASK_RUNNING);
  	remove_wait_queue(&stop_sync_wait, &wait);
  
  	/* Note: no need to reap the sync thread, because its parent
  	   process is the init process */
  
  	if ((state == IP_VS_STATE_MASTER && stop_master_sync) ||
  	    (state == IP_VS_STATE_BACKUP && stop_backup_sync))
  		IP_VS_BUG();
  
  	return 0;
  }
  