/******************************************************************************
  *******************************************************************************
  **
  **  Copyright (C) Sistina Software, Inc.  1997-2003  All rights reserved.

  **  Copyright (C) 2004-2007 Red Hat, Inc.  All rights reserved.

  **
  **  This copyrighted material is made available to anyone wishing to use,
  **  modify, copy, or redistribute it subject to the terms and conditions
  **  of the GNU General Public License v.2.
  **
  *******************************************************************************
  ******************************************************************************/
  
  /*
   * lowcomms.c
   *
   * This is the "low-level" comms layer.
   *
   * It is responsible for sending/receiving messages
   * from other nodes in the cluster.
   *
   * Cluster nodes are referred to by their nodeids. nodeids are
   * simply 32 bit numbers to the locking module - if they need to
   * be expanded for the cluster infrastructure then that is it's
   * responsibility. It is this layer's
   * responsibility to resolve these into IP address or
   * whatever it needs for inter-node communication.
   *
   * The comms level is two kernel threads that deal mainly with
   * the receiving of messages from other nodes and passing them
   * up to the mid-level comms layer (which understands the
   * message format) for execution by the locking core, and
   * a send thread which does all the setting up of connections
   * to remote nodes and the sending of data. Threads are not allowed
   * to send their own data because it may cause them to wait in times
   * of high load. Also, this way, the sending thread can collect together
   * messages bound for one node and send them in one block.
   *

   * lowcomms will choose to use wither TCP or SCTP as its transport layer
   * depending on the configuration variable 'protocol'. This should be set
   * to 0 (default) for TCP or 1 for SCTP. It shouldbe configured using a
   * cluster-wide mechanism as it must be the same on all nodes of the cluster
   * for the DLM to function.

   *
   */

  #include <asm/ioctls.h>
  #include <net/sock.h>
  #include <net/tcp.h>
  #include <linux/pagemap.h>

  #include <linux/idr.h>
  #include <linux/file.h>

  #include <linux/mutex.h>

  #include <linux/sctp.h>
  #include <net/sctp/user.h>

  
  #include "dlm_internal.h"
  #include "lowcomms.h"
  #include "midcomms.h"
  #include "config.h"

  #define NEEDED_RMEM (4*1024*1024)

  struct cbuf {

  	unsigned int base;
  	unsigned int len;
  	unsigned int mask;

  };

  static void cbuf_add(struct cbuf *cb, int n)
  {
  	cb->len += n;
  }

  static int cbuf_data(struct cbuf *cb)
  {
  	return ((cb->base + cb->len) & cb->mask);
  }
  
  static void cbuf_init(struct cbuf *cb, int size)
  {
  	cb->base = cb->len = 0;
  	cb->mask = size-1;
  }
  
  static void cbuf_eat(struct cbuf *cb, int n)
  {
  	cb->len  -= n;
  	cb->base += n;
  	cb->base &= cb->mask;
  }
  
  static bool cbuf_empty(struct cbuf *cb)
  {
  	return cb->len == 0;
  }

  struct connection {
  	struct socket *sock;	/* NULL if not connected */
  	uint32_t nodeid;	/* So we know who we are in the list */

  	struct mutex sock_mutex;

  	unsigned long flags;

  #define CF_READ_PENDING 1
  #define CF_WRITE_PENDING 2
  #define CF_CONNECT_PENDING 3

  #define CF_INIT_PENDING 4
  #define CF_IS_OTHERCON 5

  	struct list_head writequeue;  /* List of outgoing writequeue_entries */

  	spinlock_t writequeue_lock;
  	int (*rx_action) (struct connection *);	/* What to do when active */

  	void (*connect_action) (struct connection *);	/* What to do to connect */

  	struct page *rx_page;
  	struct cbuf cb;
  	int retries;

  #define MAX_CONNECT_RETRIES 3

  	int sctp_assoc;

  	struct connection *othercon;

  	struct work_struct rwork; /* Receive workqueue */
  	struct work_struct swork; /* Send workqueue */

  };
  #define sock2con(x) ((struct connection *)(x)->sk_user_data)
  
  /* An entry waiting to be sent */
  struct writequeue_entry {
  	struct list_head list;
  	struct page *page;
  	int offset;
  	int len;
  	int end;
  	int users;
  	struct connection *con;
  };

  static struct sockaddr_storage *dlm_local_addr[DLM_MAX_ADDR_COUNT];
  static int dlm_local_count;

  /* Work queues */
  static struct workqueue_struct *recv_workqueue;
  static struct workqueue_struct *send_workqueue;

  static DEFINE_IDR(connections_idr);

  static DEFINE_MUTEX(connections_lock);

  static int max_nodeid;

  static struct kmem_cache *con_cache;

  static void process_recv_sockets(struct work_struct *work);
  static void process_send_sockets(struct work_struct *work);

  /*
   * If 'allocation' is zero then we don't attempt to create a new
   * connection structure for this node.
   */
  static struct connection *__nodeid2con(int nodeid, gfp_t alloc)

  {
  	struct connection *con = NULL;

  	int r;
  	int n;

  	con = idr_find(&connections_idr, nodeid);
  	if (con || !alloc)
  		return con;

  	r = idr_pre_get(&connections_idr, alloc);
  	if (!r)
  		return NULL;
  
  	con = kmem_cache_zalloc(con_cache, alloc);
  	if (!con)
  		return NULL;

  	r = idr_get_new_above(&connections_idr, con, nodeid, &n);
  	if (r) {
  		kmem_cache_free(con_cache, con);
  		return NULL;
  	}

  	if (n != nodeid) {
  		idr_remove(&connections_idr, n);
  		kmem_cache_free(con_cache, con);
  		return NULL;

  	}

  	con->nodeid = nodeid;
  	mutex_init(&con->sock_mutex);
  	INIT_LIST_HEAD(&con->writequeue);
  	spin_lock_init(&con->writequeue_lock);
  	INIT_WORK(&con->swork, process_send_sockets);
  	INIT_WORK(&con->rwork, process_recv_sockets);

  	/* Setup action pointers for child sockets */
  	if (con->nodeid) {
  		struct connection *zerocon = idr_find(&connections_idr, 0);

  		con->connect_action = zerocon->connect_action;
  		if (!con->rx_action)
  			con->rx_action = zerocon->rx_action;

  	}

  	if (nodeid > max_nodeid)
  		max_nodeid = nodeid;
  
  	return con;
  }
  
  static struct connection *nodeid2con(int nodeid, gfp_t allocation)
  {
  	struct connection *con;

  	mutex_lock(&connections_lock);

  	con = __nodeid2con(nodeid, allocation);

  	mutex_unlock(&connections_lock);

  	return con;
  }

  /* This is a bit drastic, but only called when things go wrong */
  static struct connection *assoc2con(int assoc_id)
  {
  	int i;
  	struct connection *con;

  	mutex_lock(&connections_lock);

  	for (i=0; i<=max_nodeid; i++) {

  		con = __nodeid2con(i, 0);
  		if (con && con->sctp_assoc == assoc_id) {

  			mutex_unlock(&connections_lock);

  			return con;
  		}
  	}

  	mutex_unlock(&connections_lock);

  	return NULL;
  }
  
  static int nodeid_to_addr(int nodeid, struct sockaddr *retaddr)
  {
  	struct sockaddr_storage addr;
  	int error;
  
  	if (!dlm_local_count)
  		return -1;
  
  	error = dlm_nodeid_to_addr(nodeid, &addr);
  	if (error)
  		return error;
  
  	if (dlm_local_addr[0]->ss_family == AF_INET) {
  		struct sockaddr_in *in4  = (struct sockaddr_in *) &addr;
  		struct sockaddr_in *ret4 = (struct sockaddr_in *) retaddr;
  		ret4->sin_addr.s_addr = in4->sin_addr.s_addr;
  	} else {
  		struct sockaddr_in6 *in6  = (struct sockaddr_in6 *) &addr;
  		struct sockaddr_in6 *ret6 = (struct sockaddr_in6 *) retaddr;
  		memcpy(&ret6->sin6_addr, &in6->sin6_addr,
  		       sizeof(in6->sin6_addr));
  	}
  
  	return 0;
  }

  /* Data available on socket or listen socket received a connect */
  static void lowcomms_data_ready(struct sock *sk, int count_unused)
  {
  	struct connection *con = sock2con(sk);

  	if (con && !test_and_set_bit(CF_READ_PENDING, &con->flags))

  		queue_work(recv_workqueue, &con->rwork);

  }
  
  static void lowcomms_write_space(struct sock *sk)
  {
  	struct connection *con = sock2con(sk);

  	if (con && !test_and_set_bit(CF_WRITE_PENDING, &con->flags))

  		queue_work(send_workqueue, &con->swork);

  }
  
  static inline void lowcomms_connect_sock(struct connection *con)
  {

  	if (!test_and_set_bit(CF_CONNECT_PENDING, &con->flags))
  		queue_work(send_workqueue, &con->swork);

  }
  
  static void lowcomms_state_change(struct sock *sk)
  {

  	if (sk->sk_state == TCP_ESTABLISHED)

  		lowcomms_write_space(sk);

  }
  
  /* Make a socket active */
  static int add_sock(struct socket *sock, struct connection *con)
  {
  	con->sock = sock;
  
  	/* Install a data_ready callback */
  	con->sock->sk->sk_data_ready = lowcomms_data_ready;
  	con->sock->sk->sk_write_space = lowcomms_write_space;
  	con->sock->sk->sk_state_change = lowcomms_state_change;

  	con->sock->sk->sk_user_data = con;

  	return 0;
  }

  /* Add the port number to an IPv6 or 4 sockaddr and return the address

     length */
  static void make_sockaddr(struct sockaddr_storage *saddr, uint16_t port,
  			  int *addr_len)
  {

  	saddr->ss_family =  dlm_local_addr[0]->ss_family;

  	if (saddr->ss_family == AF_INET) {

  		struct sockaddr_in *in4_addr = (struct sockaddr_in *)saddr;
  		in4_addr->sin_port = cpu_to_be16(port);
  		*addr_len = sizeof(struct sockaddr_in);

  		memset(&in4_addr->sin_zero, 0, sizeof(in4_addr->sin_zero));

  	} else {

  		struct sockaddr_in6 *in6_addr = (struct sockaddr_in6 *)saddr;
  		in6_addr->sin6_port = cpu_to_be16(port);
  		*addr_len = sizeof(struct sockaddr_in6);
  	}

  	memset((char *)saddr + *addr_len, 0, sizeof(struct sockaddr_storage) - *addr_len);

  }
  
  /* Close a remote connection and tidy up */

  static void close_connection(struct connection *con, bool and_other)

  {

  	mutex_lock(&con->sock_mutex);

  
  	if (con->sock) {
  		sock_release(con->sock);
  		con->sock = NULL;
  	}
  	if (con->othercon && and_other) {

  		/* Will only re-enter once. */
  		close_connection(con->othercon, false);

  	}
  	if (con->rx_page) {
  		__free_page(con->rx_page);
  		con->rx_page = NULL;
  	}

  	con->retries = 0;
  	mutex_unlock(&con->sock_mutex);

  }

  /* We only send shutdown messages to nodes that are not part of the cluster */
  static void sctp_send_shutdown(sctp_assoc_t associd)
  {
  	static char outcmsg[CMSG_SPACE(sizeof(struct sctp_sndrcvinfo))];
  	struct msghdr outmessage;
  	struct cmsghdr *cmsg;
  	struct sctp_sndrcvinfo *sinfo;
  	int ret;
  	struct connection *con;
  
  	con = nodeid2con(0,0);
  	BUG_ON(con == NULL);
  
  	outmessage.msg_name = NULL;
  	outmessage.msg_namelen = 0;
  	outmessage.msg_control = outcmsg;
  	outmessage.msg_controllen = sizeof(outcmsg);
  	outmessage.msg_flags = MSG_EOR;
  
  	cmsg = CMSG_FIRSTHDR(&outmessage);
  	cmsg->cmsg_level = IPPROTO_SCTP;
  	cmsg->cmsg_type = SCTP_SNDRCV;
  	cmsg->cmsg_len = CMSG_LEN(sizeof(struct sctp_sndrcvinfo));
  	outmessage.msg_controllen = cmsg->cmsg_len;
  	sinfo = CMSG_DATA(cmsg);
  	memset(sinfo, 0x00, sizeof(struct sctp_sndrcvinfo));
  
  	sinfo->sinfo_flags |= MSG_EOF;
  	sinfo->sinfo_assoc_id = associd;
  
  	ret = kernel_sendmsg(con->sock, &outmessage, NULL, 0, 0);
  
  	if (ret != 0)
  		log_print("send EOF to node failed: %d", ret);
  }
  
  /* INIT failed but we don't know which node...
     restart INIT on all pending nodes */
  static void sctp_init_failed(void)
  {
  	int i;
  	struct connection *con;

  	mutex_lock(&connections_lock);

  	for (i=1; i<=max_nodeid; i++) {
  		con = __nodeid2con(i, 0);
  		if (!con)
  			continue;
  		con->sctp_assoc = 0;
  		if (test_and_clear_bit(CF_CONNECT_PENDING, &con->flags)) {
  			if (!test_and_set_bit(CF_WRITE_PENDING, &con->flags)) {
  				queue_work(send_workqueue, &con->swork);
  			}
  		}
  	}

  	mutex_unlock(&connections_lock);

  }
  
  /* Something happened to an association */

  static void process_sctp_notification(struct connection *con,
  				      struct msghdr *msg, char *buf)

  {
  	union sctp_notification *sn = (union sctp_notification *)buf;
  
  	if (sn->sn_header.sn_type == SCTP_ASSOC_CHANGE) {
  		switch (sn->sn_assoc_change.sac_state) {
  
  		case SCTP_COMM_UP:
  		case SCTP_RESTART:
  		{
  			/* Check that the new node is in the lockspace */
  			struct sctp_prim prim;
  			int nodeid;
  			int prim_len, ret;
  			int addr_len;
  			struct connection *new_con;
  			struct file *file;
  			sctp_peeloff_arg_t parg;
  			int parglen = sizeof(parg);
  
  			/*
  			 * We get this before any data for an association.
  			 * We verify that the node is in the cluster and
  			 * then peel off a socket for it.
  			 */
  			if ((int)sn->sn_assoc_change.sac_assoc_id <= 0) {
  				log_print("COMM_UP for invalid assoc ID %d",

  					 (int)sn->sn_assoc_change.sac_assoc_id);

  				sctp_init_failed();
  				return;
  			}
  			memset(&prim, 0, sizeof(struct sctp_prim));
  			prim_len = sizeof(struct sctp_prim);
  			prim.ssp_assoc_id = sn->sn_assoc_change.sac_assoc_id;
  
  			ret = kernel_getsockopt(con->sock,
  						IPPROTO_SCTP,
  						SCTP_PRIMARY_ADDR,
  						(char*)&prim,
  						&prim_len);
  			if (ret < 0) {
  				log_print("getsockopt/sctp_primary_addr on "
  					  "new assoc %d failed : %d",
  					  (int)sn->sn_assoc_change.sac_assoc_id,
  					  ret);
  
  				/* Retry INIT later */
  				new_con = assoc2con(sn->sn_assoc_change.sac_assoc_id);
  				if (new_con)
  					clear_bit(CF_CONNECT_PENDING, &con->flags);
  				return;
  			}
  			make_sockaddr(&prim.ssp_addr, 0, &addr_len);
  			if (dlm_addr_to_nodeid(&prim.ssp_addr, &nodeid)) {
  				int i;
  				unsigned char *b=(unsigned char *)&prim.ssp_addr;
  				log_print("reject connect from unknown addr");
  				for (i=0; i<sizeof(struct sockaddr_storage);i++)
  					printk("%02x ", b[i]);
  				printk("
  ");
  				sctp_send_shutdown(prim.ssp_assoc_id);
  				return;
  			}
  
  			new_con = nodeid2con(nodeid, GFP_KERNEL);
  			if (!new_con)
  				return;
  
  			/* Peel off a new sock */
  			parg.associd = sn->sn_assoc_change.sac_assoc_id;

  			ret = kernel_getsockopt(con->sock, IPPROTO_SCTP,
  						SCTP_SOCKOPT_PEELOFF,

  						(void *)&parg, &parglen);

  			if (ret) {

  				log_print("Can't peel off a socket for "
  					  "connection %d to node %d: err=%d
  ",

  					  parg.associd, nodeid, ret);

  			}

  			file = fget(parg.sd);
  			new_con->sock = SOCKET_I(file->f_dentry->d_inode);
  			add_sock(new_con->sock, new_con);
  			fput(file);
  			put_unused_fd(parg.sd);
  
  			log_print("got new/restarted association %d nodeid %d",

  				 (int)sn->sn_assoc_change.sac_assoc_id, nodeid);

  
  			/* Send any pending writes */
  			clear_bit(CF_CONNECT_PENDING, &new_con->flags);
  			clear_bit(CF_INIT_PENDING, &con->flags);
  			if (!test_and_set_bit(CF_WRITE_PENDING, &new_con->flags)) {
  				queue_work(send_workqueue, &new_con->swork);
  			}
  			if (!test_and_set_bit(CF_READ_PENDING, &new_con->flags))
  				queue_work(recv_workqueue, &new_con->rwork);
  		}
  		break;
  
  		case SCTP_COMM_LOST:
  		case SCTP_SHUTDOWN_COMP:
  		{
  			con = assoc2con(sn->sn_assoc_change.sac_assoc_id);
  			if (con) {
  				con->sctp_assoc = 0;
  			}
  		}
  		break;
  
  		/* We don't know which INIT failed, so clear the PENDING flags
  		 * on them all.  if assoc_id is zero then it will then try
  		 * again */
  
  		case SCTP_CANT_STR_ASSOC:
  		{
  			log_print("Can't start SCTP association - retrying");
  			sctp_init_failed();
  		}
  		break;
  
  		default:
  			log_print("unexpected SCTP assoc change id=%d state=%d",
  				  (int)sn->sn_assoc_change.sac_assoc_id,
  				  sn->sn_assoc_change.sac_state);
  		}
  	}
  }

  /* Data received from remote end */
  static int receive_from_sock(struct connection *con)
  {
  	int ret = 0;

  	struct msghdr msg = {};
  	struct kvec iov[2];

  	unsigned len;
  	int r;
  	int call_again_soon = 0;

  	int nvec;

  	char incmsg[CMSG_SPACE(sizeof(struct sctp_sndrcvinfo))];

  	mutex_lock(&con->sock_mutex);

  	if (con->sock == NULL) {
  		ret = -EAGAIN;
  		goto out_close;
  	}

  	if (con->rx_page == NULL) {
  		/*
  		 * This doesn't need to be atomic, but I think it should
  		 * improve performance if it is.
  		 */
  		con->rx_page = alloc_page(GFP_ATOMIC);
  		if (con->rx_page == NULL)
  			goto out_resched;

  		cbuf_init(&con->cb, PAGE_CACHE_SIZE);

  	}

  	/* Only SCTP needs these really */
  	memset(&incmsg, 0, sizeof(incmsg));
  	msg.msg_control = incmsg;
  	msg.msg_controllen = sizeof(incmsg);

  	/*
  	 * iov[0] is the bit of the circular buffer between the current end
  	 * point (cb.base + cb.len) and the end of the buffer.
  	 */

  	iov[0].iov_len = con->cb.base - cbuf_data(&con->cb);
  	iov[0].iov_base = page_address(con->rx_page) + cbuf_data(&con->cb);

  	iov[1].iov_len = 0;

  	nvec = 1;

  
  	/*
  	 * iov[1] is the bit of the circular buffer between the start of the
  	 * buffer and the start of the currently used section (cb.base)
  	 */

  	if (cbuf_data(&con->cb) >= con->cb.base) {
  		iov[0].iov_len = PAGE_CACHE_SIZE - cbuf_data(&con->cb);

  		iov[1].iov_len = con->cb.base;
  		iov[1].iov_base = page_address(con->rx_page);

  		nvec = 2;

  	}
  	len = iov[0].iov_len + iov[1].iov_len;

  	r = ret = kernel_recvmsg(con->sock, &msg, iov, nvec, len,

  			       MSG_DONTWAIT | MSG_NOSIGNAL);

  	if (ret <= 0)
  		goto out_close;

  	/* Process SCTP notifications */
  	if (msg.msg_flags & MSG_NOTIFICATION) {

  		msg.msg_control = incmsg;
  		msg.msg_controllen = sizeof(incmsg);
  
  		process_sctp_notification(con, &msg,

  				page_address(con->rx_page) + con->cb.base);

  		mutex_unlock(&con->sock_mutex);
  		return 0;
  	}
  	BUG_ON(con->nodeid == 0);

  	if (ret == len)
  		call_again_soon = 1;

  	cbuf_add(&con->cb, ret);

  	ret = dlm_process_incoming_buffer(con->nodeid,
  					  page_address(con->rx_page),
  					  con->cb.base, con->cb.len,
  					  PAGE_CACHE_SIZE);
  	if (ret == -EBADMSG) {

  		log_print("lowcomms: addr=%p, base=%u, len=%u, "
  			  "iov_len=%u, iov_base[0]=%p, read=%d",
  			  page_address(con->rx_page), con->cb.base, con->cb.len,
  			  len, iov[0].iov_base, r);

  	}
  	if (ret < 0)
  		goto out_close;

  	cbuf_eat(&con->cb, ret);

  	if (cbuf_empty(&con->cb) && !call_again_soon) {

  		__free_page(con->rx_page);
  		con->rx_page = NULL;
  	}

  	if (call_again_soon)
  		goto out_resched;

  	mutex_unlock(&con->sock_mutex);

  	return 0;

  out_resched:

  	if (!test_and_set_bit(CF_READ_PENDING, &con->flags))
  		queue_work(recv_workqueue, &con->rwork);

  	mutex_unlock(&con->sock_mutex);

  	return -EAGAIN;

  out_close:

  	mutex_unlock(&con->sock_mutex);

  	if (ret != -EAGAIN) {

  		close_connection(con, false);

  		/* Reconnect when there is something to send */
  	}

  	/* Don't return success if we really got EOF */
  	if (ret == 0)
  		ret = -EAGAIN;

  	return ret;
  }
  
  /* Listening socket is busy, accept a connection */

  static int tcp_accept_from_sock(struct connection *con)

  {
  	int result;
  	struct sockaddr_storage peeraddr;
  	struct socket *newsock;
  	int len;
  	int nodeid;
  	struct connection *newcon;

  	struct connection *addcon;

  
  	memset(&peeraddr, 0, sizeof(peeraddr));

  	result = sock_create_kern(dlm_local_addr[0]->ss_family, SOCK_STREAM,

  				  IPPROTO_TCP, &newsock);

  	if (result < 0)
  		return -ENOMEM;

  	mutex_lock_nested(&con->sock_mutex, 0);

  
  	result = -ENOTCONN;
  	if (con->sock == NULL)
  		goto accept_err;
  
  	newsock->type = con->sock->type;
  	newsock->ops = con->sock->ops;
  
  	result = con->sock->ops->accept(con->sock, newsock, O_NONBLOCK);
  	if (result < 0)
  		goto accept_err;
  
  	/* Get the connected socket's peer */
  	memset(&peeraddr, 0, sizeof(peeraddr));
  	if (newsock->ops->getname(newsock, (struct sockaddr *)&peeraddr,
  				  &len, 2)) {
  		result = -ECONNABORTED;
  		goto accept_err;
  	}
  
  	/* Get the new node's NODEID */
  	make_sockaddr(&peeraddr, 0, &len);
  	if (dlm_addr_to_nodeid(&peeraddr, &nodeid)) {

  		log_print("connect from non cluster node");

  		sock_release(newsock);

  		mutex_unlock(&con->sock_mutex);

  		return -1;
  	}
  
  	log_print("got connection from %d", nodeid);
  
  	/*  Check to see if we already have a connection to this node. This
  	 *  could happen if the two nodes initiate a connection at roughly
  	 *  the same time and the connections cross on the wire.

  	 *  In this case we store the incoming one in "othercon"
  	 */
  	newcon = nodeid2con(nodeid, GFP_KERNEL);
  	if (!newcon) {
  		result = -ENOMEM;
  		goto accept_err;
  	}

  	mutex_lock_nested(&newcon->sock_mutex, 1);

  	if (newcon->sock) {

  		struct connection *othercon = newcon->othercon;

  
  		if (!othercon) {

  			othercon = kmem_cache_zalloc(con_cache, GFP_KERNEL);

  			if (!othercon) {

  				log_print("failed to allocate incoming socket");

  				mutex_unlock(&newcon->sock_mutex);

  				result = -ENOMEM;
  				goto accept_err;
  			}

  			othercon->nodeid = nodeid;
  			othercon->rx_action = receive_from_sock;

  			mutex_init(&othercon->sock_mutex);

  			INIT_WORK(&othercon->swork, process_send_sockets);
  			INIT_WORK(&othercon->rwork, process_recv_sockets);

  			set_bit(CF_IS_OTHERCON, &othercon->flags);

  		}
  		if (!othercon->sock) {

  			newcon->othercon = othercon;

  			othercon->sock = newsock;
  			newsock->sk->sk_user_data = othercon;
  			add_sock(newsock, othercon);
  			addcon = othercon;
  		}
  		else {
  			printk("Extra connection from node %d attempted
  ", nodeid);
  			result = -EAGAIN;

  			mutex_unlock(&newcon->sock_mutex);

  			goto accept_err;

  		}

  	}
  	else {
  		newsock->sk->sk_user_data = newcon;
  		newcon->rx_action = receive_from_sock;
  		add_sock(newsock, newcon);

  		addcon = newcon;

  	}

  	mutex_unlock(&newcon->sock_mutex);

  
  	/*
  	 * Add it to the active queue in case we got data
  	 * beween processing the accept adding the socket
  	 * to the read_sockets list
  	 */

  	if (!test_and_set_bit(CF_READ_PENDING, &addcon->flags))
  		queue_work(recv_workqueue, &addcon->rwork);

  	mutex_unlock(&con->sock_mutex);

  
  	return 0;

  accept_err:

  	mutex_unlock(&con->sock_mutex);

  	sock_release(newsock);
  
  	if (result != -EAGAIN)

  		log_print("error accepting connection from node: %d", result);

  	return result;
  }

  static void free_entry(struct writequeue_entry *e)
  {
  	__free_page(e->page);
  	kfree(e);
  }
  
  /* Initiate an SCTP association.
     This is a special case of send_to_sock() in that we don't yet have a
     peeled-off socket for this association, so we use the listening socket
     and add the primary IP address of the remote node.
   */
  static void sctp_init_assoc(struct connection *con)
  {
  	struct sockaddr_storage rem_addr;
  	char outcmsg[CMSG_SPACE(sizeof(struct sctp_sndrcvinfo))];
  	struct msghdr outmessage;
  	struct cmsghdr *cmsg;
  	struct sctp_sndrcvinfo *sinfo;
  	struct connection *base_con;
  	struct writequeue_entry *e;
  	int len, offset;
  	int ret;
  	int addrlen;
  	struct kvec iov[1];
  
  	if (test_and_set_bit(CF_INIT_PENDING, &con->flags))
  		return;
  
  	if (con->retries++ > MAX_CONNECT_RETRIES)
  		return;
  
  	log_print("Initiating association with node %d", con->nodeid);
  
  	if (nodeid_to_addr(con->nodeid, (struct sockaddr *)&rem_addr)) {
  		log_print("no address for nodeid %d", con->nodeid);
  		return;
  	}
  	base_con = nodeid2con(0, 0);
  	BUG_ON(base_con == NULL);
  
  	make_sockaddr(&rem_addr, dlm_config.ci_tcp_port, &addrlen);
  
  	outmessage.msg_name = &rem_addr;
  	outmessage.msg_namelen = addrlen;
  	outmessage.msg_control = outcmsg;
  	outmessage.msg_controllen = sizeof(outcmsg);
  	outmessage.msg_flags = MSG_EOR;
  
  	spin_lock(&con->writequeue_lock);
  	e = list_entry(con->writequeue.next, struct writequeue_entry,
  		       list);
  
  	BUG_ON((struct list_head *) e == &con->writequeue);
  
  	len = e->len;
  	offset = e->offset;
  	spin_unlock(&con->writequeue_lock);
  	kmap(e->page);
  
  	/* Send the first block off the write queue */
  	iov[0].iov_base = page_address(e->page)+offset;
  	iov[0].iov_len = len;
  
  	cmsg = CMSG_FIRSTHDR(&outmessage);
  	cmsg->cmsg_level = IPPROTO_SCTP;
  	cmsg->cmsg_type = SCTP_SNDRCV;
  	cmsg->cmsg_len = CMSG_LEN(sizeof(struct sctp_sndrcvinfo));
  	sinfo = CMSG_DATA(cmsg);
  	memset(sinfo, 0x00, sizeof(struct sctp_sndrcvinfo));
  	sinfo->sinfo_ppid = cpu_to_le32(dlm_our_nodeid());
  	outmessage.msg_controllen = cmsg->cmsg_len;
  
  	ret = kernel_sendmsg(base_con->sock, &outmessage, iov, 1, len);
  	if (ret < 0) {

  		log_print("Send first packet to node %d failed: %d",
  			  con->nodeid, ret);

  
  		/* Try again later */
  		clear_bit(CF_CONNECT_PENDING, &con->flags);
  		clear_bit(CF_INIT_PENDING, &con->flags);
  	}
  	else {
  		spin_lock(&con->writequeue_lock);
  		e->offset += ret;
  		e->len -= ret;
  
  		if (e->len == 0 && e->users == 0) {
  			list_del(&e->list);
  			kunmap(e->page);
  			free_entry(e);
  		}
  		spin_unlock(&con->writequeue_lock);
  	}
  }

  /* Connect a new socket to its peer */

  static void tcp_connect_to_sock(struct connection *con)

  {
  	int result = -EHOSTUNREACH;

  	struct sockaddr_storage saddr, src_addr;

  	int addr_len;
  	struct socket *sock;
  
  	if (con->nodeid == 0) {
  		log_print("attempt to connect sock 0 foiled");

  		return;

  	}

  	mutex_lock(&con->sock_mutex);

  	if (con->retries++ > MAX_CONNECT_RETRIES)
  		goto out;
  
  	/* Some odd races can cause double-connects, ignore them */
  	if (con->sock) {
  		result = 0;
  		goto out;
  	}
  
  	/* Create a socket to communicate with */

  	result = sock_create_kern(dlm_local_addr[0]->ss_family, SOCK_STREAM,

  				  IPPROTO_TCP, &sock);

  	if (result < 0)
  		goto out_err;
  
  	memset(&saddr, 0, sizeof(saddr));
  	if (dlm_nodeid_to_addr(con->nodeid, &saddr))

  		goto out_err;

  
  	sock->sk->sk_user_data = con;
  	con->rx_action = receive_from_sock;

  	con->connect_action = tcp_connect_to_sock;
  	add_sock(sock, con);

  	/* Bind to our cluster-known address connecting to avoid
  	   routing problems */
  	memcpy(&src_addr, dlm_local_addr[0], sizeof(src_addr));
  	make_sockaddr(&src_addr, 0, &addr_len);
  	result = sock->ops->bind(sock, (struct sockaddr *) &src_addr,
  				 addr_len);
  	if (result < 0) {
  		log_print("could not bind for connect: %d", result);
  		/* This *may* not indicate a critical error */
  	}

  	make_sockaddr(&saddr, dlm_config.ci_tcp_port, &addr_len);

  	log_print("connecting to %d", con->nodeid);
  	result =
  		sock->ops->connect(sock, (struct sockaddr *)&saddr, addr_len,

  				   O_NONBLOCK);

  	if (result == -EINPROGRESS)
  		result = 0;

  	if (result == 0)
  		goto out;

  out_err:

  	if (con->sock) {
  		sock_release(con->sock);
  		con->sock = NULL;
  	}
  	/*
  	 * Some errors are fatal and this list might need adjusting. For other
  	 * errors we try again until the max number of retries is reached.
  	 */
  	if (result != -EHOSTUNREACH && result != -ENETUNREACH &&

  	    result != -ENETDOWN && result != -EINVAL

  	    && result != -EPROTONOSUPPORT) {
  		lowcomms_connect_sock(con);
  		result = 0;
  	}

  out:

  	mutex_unlock(&con->sock_mutex);

  	return;

  }

  static struct socket *tcp_create_listen_sock(struct connection *con,
  					     struct sockaddr_storage *saddr)

  {

  	struct socket *sock = NULL;

  	int result = 0;
  	int one = 1;
  	int addr_len;

  	if (dlm_local_addr[0]->ss_family == AF_INET)

  		addr_len = sizeof(struct sockaddr_in);
  	else
  		addr_len = sizeof(struct sockaddr_in6);
  
  	/* Create a socket to communicate with */

  	result = sock_create_kern(dlm_local_addr[0]->ss_family, SOCK_STREAM,
  				  IPPROTO_TCP, &sock);

  	if (result < 0) {

  		log_print("Can't create listening comms socket");

  		goto create_out;
  	}

  	result = kernel_setsockopt(sock, SOL_SOCKET, SO_REUSEADDR,
  				   (char *)&one, sizeof(one));

  	if (result < 0) {

  		log_print("Failed to set SO_REUSEADDR on socket: %d", result);

  	}
  	sock->sk->sk_user_data = con;

  	con->rx_action = tcp_accept_from_sock;
  	con->connect_action = tcp_connect_to_sock;

  	con->sock = sock;
  
  	/* Bind to our port */

  	make_sockaddr(saddr, dlm_config.ci_tcp_port, &addr_len);

  	result = sock->ops->bind(sock, (struct sockaddr *) saddr, addr_len);
  	if (result < 0) {

  		log_print("Can't bind to port %d", dlm_config.ci_tcp_port);

  		sock_release(sock);
  		sock = NULL;
  		con->sock = NULL;
  		goto create_out;
  	}

  	result = kernel_setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE,

  				 (char *)&one, sizeof(one));

  	if (result < 0) {

  		log_print("Set keepalive failed: %d", result);

  	}
  
  	result = sock->ops->listen(sock, 5);
  	if (result < 0) {

  		log_print("Can't listen on port %d", dlm_config.ci_tcp_port);

  		sock_release(sock);
  		sock = NULL;
  		goto create_out;
  	}

  create_out:

  	return sock;
  }

  /* Get local addresses */
  static void init_local(void)
  {
  	struct sockaddr_storage sas, *addr;
  	int i;

  	dlm_local_count = 0;

  	for (i = 0; i < DLM_MAX_ADDR_COUNT - 1; i++) {
  		if (dlm_our_addr(&sas, i))
  			break;
  
  		addr = kmalloc(sizeof(*addr), GFP_KERNEL);
  		if (!addr)
  			break;
  		memcpy(addr, &sas, sizeof(*addr));
  		dlm_local_addr[dlm_local_count++] = addr;
  	}
  }

  /* Bind to an IP address. SCTP allows multiple address so it can do
     multi-homing */
  static int add_sctp_bind_addr(struct connection *sctp_con,
  			      struct sockaddr_storage *addr,
  			      int addr_len, int num)

  {
  	int result = 0;
  
  	if (num == 1)
  		result = kernel_bind(sctp_con->sock,
  				     (struct sockaddr *) addr,
  				     addr_len);
  	else
  		result = kernel_setsockopt(sctp_con->sock, SOL_SCTP,
  					   SCTP_SOCKOPT_BINDX_ADD,
  					   (char *)addr, addr_len);
  
  	if (result < 0)
  		log_print("Can't bind to port %d addr number %d",
  			  dlm_config.ci_tcp_port, num);
  
  	return result;
  }

  /* Initialise SCTP socket and bind to all interfaces */
  static int sctp_listen_for_all(void)
  {
  	struct socket *sock = NULL;
  	struct sockaddr_storage localaddr;
  	struct sctp_event_subscribe subscribe;
  	int result = -EINVAL, num = 1, i, addr_len;
  	struct connection *con = nodeid2con(0, GFP_KERNEL);
  	int bufsize = NEEDED_RMEM;
  
  	if (!con)
  		return -ENOMEM;
  
  	log_print("Using SCTP for communications");
  
  	result = sock_create_kern(dlm_local_addr[0]->ss_family, SOCK_SEQPACKET,
  				  IPPROTO_SCTP, &sock);
  	if (result < 0) {
  		log_print("Can't create comms socket, check SCTP is loaded");
  		goto out;
  	}
  
  	/* Listen for events */
  	memset(&subscribe, 0, sizeof(subscribe));
  	subscribe.sctp_data_io_event = 1;
  	subscribe.sctp_association_event = 1;
  	subscribe.sctp_send_failure_event = 1;
  	subscribe.sctp_shutdown_event = 1;
  	subscribe.sctp_partial_delivery_event = 1;

  	result = kernel_setsockopt(sock, SOL_SOCKET, SO_RCVBUFFORCE,

  				 (char *)&bufsize, sizeof(bufsize));
  	if (result)

  		log_print("Error increasing buffer space on socket %d", result);

  
  	result = kernel_setsockopt(sock, SOL_SCTP, SCTP_EVENTS,

  				   (char *)&subscribe, sizeof(subscribe));

  	if (result < 0) {
  		log_print("Failed to set SCTP_EVENTS on socket: result=%d",
  			  result);
  		goto create_delsock;
  	}
  
  	/* Init con struct */
  	sock->sk->sk_user_data = con;
  	con->sock = sock;
  	con->sock->sk->sk_data_ready = lowcomms_data_ready;
  	con->rx_action = receive_from_sock;
  	con->connect_action = sctp_init_assoc;
  
  	/* Bind to all interfaces. */
  	for (i = 0; i < dlm_local_count; i++) {
  		memcpy(&localaddr, dlm_local_addr[i], sizeof(localaddr));
  		make_sockaddr(&localaddr, dlm_config.ci_tcp_port, &addr_len);
  
  		result = add_sctp_bind_addr(con, &localaddr, addr_len, num);
  		if (result)
  			goto create_delsock;
  		++num;
  	}
  
  	result = sock->ops->listen(sock, 5);
  	if (result < 0) {
  		log_print("Can't set socket listening");
  		goto create_delsock;
  	}
  
  	return 0;
  
  create_delsock:
  	sock_release(sock);
  	con->sock = NULL;
  out:
  	return result;
  }
  
  static int tcp_listen_for_all(void)

  {
  	struct socket *sock = NULL;
  	struct connection *con = nodeid2con(0, GFP_KERNEL);
  	int result = -EINVAL;

  	if (!con)
  		return -ENOMEM;

  	/* We don't support multi-homed hosts */

  	if (dlm_local_addr[1] != NULL) {

  		log_print("TCP protocol can't handle multi-homed hosts, "
  			  "try SCTP");

  		return -EINVAL;
  	}
  
  	log_print("Using TCP for communications");

  	sock = tcp_create_listen_sock(con, dlm_local_addr[0]);

  	if (sock) {
  		add_sock(sock, con);
  		result = 0;
  	}
  	else {
  		result = -EADDRINUSE;
  	}
  
  	return result;
  }
  
  
  
  static struct writequeue_entry *new_writequeue_entry(struct connection *con,
  						     gfp_t allocation)
  {
  	struct writequeue_entry *entry;
  
  	entry = kmalloc(sizeof(struct writequeue_entry), allocation);
  	if (!entry)
  		return NULL;
  
  	entry->page = alloc_page(allocation);
  	if (!entry->page) {
  		kfree(entry);
  		return NULL;
  	}
  
  	entry->offset = 0;
  	entry->len = 0;
  	entry->end = 0;
  	entry->users = 0;
  	entry->con = con;
  
  	return entry;
  }

  void *dlm_lowcomms_get_buffer(int nodeid, int len, gfp_t allocation, char **ppc)

  {
  	struct connection *con;
  	struct writequeue_entry *e;
  	int offset = 0;
  	int users = 0;

  	con = nodeid2con(nodeid, allocation);
  	if (!con)
  		return NULL;

  	spin_lock(&con->writequeue_lock);

  	e = list_entry(con->writequeue.prev, struct writequeue_entry, list);

  	if ((&e->list == &con->writequeue) ||

  	    (PAGE_CACHE_SIZE - e->end < len)) {
  		e = NULL;
  	} else {
  		offset = e->end;
  		e->end += len;
  		users = e->users++;
  	}
  	spin_unlock(&con->writequeue_lock);
  
  	if (e) {

  	got_one:

  		if (users == 0)
  			kmap(e->page);
  		*ppc = page_address(e->page) + offset;
  		return e;
  	}
  
  	e = new_writequeue_entry(con, allocation);
  	if (e) {
  		spin_lock(&con->writequeue_lock);
  		offset = e->end;
  		e->end += len;
  		users = e->users++;
  		list_add_tail(&e->list, &con->writequeue);
  		spin_unlock(&con->writequeue_lock);
  		goto got_one;
  	}
  	return NULL;
  }
  
  void dlm_lowcomms_commit_buffer(void *mh)
  {
  	struct writequeue_entry *e = (struct writequeue_entry *)mh;
  	struct connection *con = e->con;
  	int users;

  	spin_lock(&con->writequeue_lock);

  	users = --e->users;
  	if (users)
  		goto out;
  	e->len = e->end - e->offset;
  	kunmap(e->page);
  	spin_unlock(&con->writequeue_lock);

  	if (!test_and_set_bit(CF_WRITE_PENDING, &con->flags)) {
  		queue_work(send_workqueue, &con->swork);

  	}
  	return;

  out:

  	spin_unlock(&con->writequeue_lock);
  	return;
  }

  /* Send a message */

  static void send_to_sock(struct connection *con)

  {
  	int ret = 0;
  	ssize_t(*sendpage) (struct socket *, struct page *, int, size_t, int);
  	const int msg_flags = MSG_DONTWAIT | MSG_NOSIGNAL;
  	struct writequeue_entry *e;
  	int len, offset;

  	mutex_lock(&con->sock_mutex);

  	if (con->sock == NULL)
  		goto out_connect;
  
  	sendpage = con->sock->ops->sendpage;
  
  	spin_lock(&con->writequeue_lock);
  	for (;;) {
  		e = list_entry(con->writequeue.next, struct writequeue_entry,
  			       list);
  		if ((struct list_head *) e == &con->writequeue)
  			break;
  
  		len = e->len;
  		offset = e->offset;
  		BUG_ON(len == 0 && e->users == 0);
  		spin_unlock(&con->writequeue_lock);

  		kmap(e->page);

  
  		ret = 0;
  		if (len) {
  			ret = sendpage(con->sock, e->page, offset, len,
  				       msg_flags);

  			if (ret == -EAGAIN || ret == 0) {
  				cond_resched();

  				goto out;

  			}

  			if (ret <= 0)
  				goto send_error;

  		}

  			/* Don't starve people filling buffers */

  			cond_resched();

  
  		spin_lock(&con->writequeue_lock);
  		e->offset += ret;
  		e->len -= ret;
  
  		if (e->len == 0 && e->users == 0) {
  			list_del(&e->list);

  			kunmap(e->page);

  			free_entry(e);
  			continue;
  		}
  	}
  	spin_unlock(&con->writequeue_lock);

  out:

  	mutex_unlock(&con->sock_mutex);

  	return;

  send_error:

  	mutex_unlock(&con->sock_mutex);

  	close_connection(con, false);

  	lowcomms_connect_sock(con);

  	return;

  out_connect:

  	mutex_unlock(&con->sock_mutex);

  	if (!test_bit(CF_INIT_PENDING, &con->flags))
  		lowcomms_connect_sock(con);

  	return;

  }
  
  static void clean_one_writequeue(struct connection *con)
  {
  	struct list_head *list;
  	struct list_head *temp;
  
  	spin_lock(&con->writequeue_lock);
  	list_for_each_safe(list, temp, &con->writequeue) {
  		struct writequeue_entry *e =
  			list_entry(list, struct writequeue_entry, list);
  		list_del(&e->list);
  		free_entry(e);
  	}
  	spin_unlock(&con->writequeue_lock);
  }
  
  /* Called from recovery when it knows that a node has
     left the cluster */
  int dlm_lowcomms_close(int nodeid)
  {
  	struct connection *con;

  	log_print("closing connection to node %d", nodeid);
  	con = nodeid2con(nodeid, 0);
  	if (con) {
  		clean_one_writequeue(con);

  		close_connection(con, true);

  	}
  	return 0;

  }

  /* Receive workqueue function */

  static void process_recv_sockets(struct work_struct *work)

  {

  	struct connection *con = container_of(work, struct connection, rwork);
  	int err;

  	clear_bit(CF_READ_PENDING, &con->flags);
  	do {
  		err = con->rx_action(con);
  	} while (!err);

  }

  /* Send workqueue function */

  static void process_send_sockets(struct work_struct *work)

  {

  	struct connection *con = container_of(work, struct connection, swork);

  	if (test_and_clear_bit(CF_CONNECT_PENDING, &con->flags)) {

  		con->connect_action(con);

  	}

  	clear_bit(CF_WRITE_PENDING, &con->flags);
  	send_to_sock(con);

  }
  
  
  /* Discard all entries on the write queues */
  static void clean_writequeues(void)
  {
  	int nodeid;

  	for (nodeid = 1; nodeid <= max_nodeid; nodeid++) {
  		struct connection *con = __nodeid2con(nodeid, 0);

  
  		if (con)
  			clean_one_writequeue(con);
  	}
  }

  static void work_stop(void)

  {

  	destroy_workqueue(recv_workqueue);
  	destroy_workqueue(send_workqueue);

  }

  static int work_start(void)

  {

  	int error;

  	recv_workqueue = create_workqueue("dlm_recv");
  	error = IS_ERR(recv_workqueue);

  	if (error) {

  		log_print("can't start dlm_recv %d", error);

  		return error;
  	}

  	send_workqueue = create_singlethread_workqueue("dlm_send");
  	error = IS_ERR(send_workqueue);

  	if (error) {

  		log_print("can't start dlm_send %d", error);
  		destroy_workqueue(recv_workqueue);

  		return error;
  	}

  
  	return 0;
  }

  void dlm_lowcomms_stop(void)
  {
  	int i;

  	struct connection *con;

  	/* Set all the flags to prevent any

  	   socket activity.
  	*/

  	mutex_lock(&connections_lock);

  	for (i = 0; i <= max_nodeid; i++) {

  		con = __nodeid2con(i, 0);

  		if (con) {

  			con->flags |= 0x0F;

  			if (con->sock)
  				con->sock->sk->sk_user_data = NULL;
  		}

  	}

  	mutex_unlock(&connections_lock);

  	work_stop();

  	mutex_lock(&connections_lock);

  	clean_writequeues();

  	for (i = 0; i <= max_nodeid; i++) {

  		con = __nodeid2con(i, 0);

  		if (con) {
  			close_connection(con, true);

  			if (con->othercon)
  				kmem_cache_free(con_cache, con->othercon);

  			kmem_cache_free(con_cache, con);

  		}
  	}

  	max_nodeid = 0;

  	mutex_unlock(&connections_lock);

  	kmem_cache_destroy(con_cache);

  	idr_init(&connections_idr);

  }

  int dlm_lowcomms_start(void)
  {

  	int error = -EINVAL;
  	struct connection *con;

  	init_local();
  	if (!dlm_local_count) {

  		error = -ENOTCONN;

  		log_print("no local IP address has been set");

  		goto out;

  	}

  	error = -ENOMEM;

  	con_cache = kmem_cache_create("dlm_conn", sizeof(struct connection),

  				      __alignof__(struct connection), 0,

  				      NULL);

  	if (!con_cache)

  		goto out;

  	/* Start listening */

  	if (dlm_config.ci_protocol == 0)
  		error = tcp_listen_for_all();
  	else
  		error = sctp_listen_for_all();

  	if (error)
  		goto fail_unlisten;

  	error = work_start();

  	if (error)
  		goto fail_unlisten;

  	return 0;

  fail_unlisten:

  	con = nodeid2con(0,0);
  	if (con) {
  		close_connection(con, false);
  		kmem_cache_free(con_cache, con);
  	}

  	kmem_cache_destroy(con_cache);

  out:

  	return error;
  }