1 files changed, 892 insertions, 0 deletions

diff --git a/net/ipv4/ipvs/ip_vs_sync.c b/net/ipv4/ipvs/ip_vs_sync.c
new file mode 100644
index 00000000000..25c479550a3
--- /dev/null
+++ b/net/ipv4/ipvs/ip_vs_sync.c
@@ -0,0 +1,892 @@
+/*
+ * 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/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 <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) */
+	__u16			cport;
+	__u16                   vport;
+	__u16                   dport;
+	__u32                   caddr;          /* client address */
+	__u32                   vaddr;          /* virtual address */
+	__u32                   daddr;          /* destination address */
+
+	/* Flags and state transition */
+	__u16                   flags;          /* status flags */
+	__u16                   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 */
+};
+
+#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++) {
+		s = (struct ip_vs_sync_conn *)p;
+		cp = ip_vs_conn_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,
+					    ntohs(s->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 = ntohs(s->flags) | IP_VS_CONN_F_HASHED;
+		}	/* Note that we don't touch its state and flags
+			   if it is a normal entry. */
+
+		if (ntohs(s->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;
+	u32 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;
+
+		ssleep(1);
+	}
+
+	/* 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;
+
+		ssleep(1);
+	}
+
+	/* 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;
+
+	/* 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((struct completion *)startup);
+
+	/* 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 */
+	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);
+
+	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);
+		ssleep(1);
+		goto repeat;
+	}
+
+	return 0;
+}
+
+
+int start_sync_thread(int state, char *mcast_ifn, __u8 syncid)
+{
+	DECLARE_COMPLETION(startup);
+	pid_t pid;
+
+	if ((state == IP_VS_STATE_MASTER && sync_master_pid) ||
+	    (state == IP_VS_STATE_BACKUP && sync_backup_pid))
+		return -EEXIST;
+
+	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) {
+		strcpy(ip_vs_master_mcast_ifn, mcast_ifn);
+		ip_vs_master_syncid = syncid;
+	} else {
+		strcpy(ip_vs_backup_mcast_ifn, mcast_ifn);
+		ip_vs_backup_syncid = syncid;
+	}
+
+  repeat:
+	if ((pid = kernel_thread(fork_sync_thread, &startup, 0)) < 0) {
+		IP_VS_ERR("could not create fork_sync_thread due to %d... "
+			  "retrying.\n", pid);
+		ssleep(1);
+		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;
+}