[tipc-discussion] [PATCH net-next v2 1/6] tipc: introduce new TIPC server infrastructure

[Ying X. <yin...@wi...>]

TIPC have two internal servers, one that provides a subscription
service for topology events and another that provides the
configuration interface. These servers have previously been running
in BH context, accessing the TIPC-port API directly. This required
complex lock policies to be implemented and it also caused
scalability problems when the topology server port got congested
and events got dropped silently.

Therefor, we are introducing a TIPC server module that uses kernel
sockets for message passing(instead of TIPC port directly).

Signed-off-by: Ying Xue <yin...@wi...>
---
 net/tipc/Makefile |    2 +-
 net/tipc/server.c |  686 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 net/tipc/server.h |  103 ++++++++
 3 files changed, 790 insertions(+), 1 deletions(-)
 create mode 100644 net/tipc/server.c
 create mode 100644 net/tipc/server.h

diff --git a/net/tipc/Makefile b/net/tipc/Makefile
index 6cd55d6..af7206b 100644
--- a/net/tipc/Makefile
+++ b/net/tipc/Makefile
@@ -8,4 +8,4 @@ tipc-y	+= addr.o bcast.o bearer.o config.o \
 	   core.o handler.o link.o discover.o msg.o  \
 	   name_distr.o  subscr.o name_table.o net.o  \
 	   netlink.o node.o node_subscr.o port.o ref.o  \
-	   socket.o log.o eth_media.o
+	   socket.o log.o eth_media.o server.o
diff --git a/net/tipc/server.c b/net/tipc/server.c
new file mode 100644
index 0000000..0c369ae
--- /dev/null
+++ b/net/tipc/server.c
@@ -0,0 +1,686 @@
+/*
+ * net/tipc/server.c: TIPC server infrastructure
+ *
+ * Copyright (c) 2012 Wind River Systems
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the names of the copyright holders nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * Alternatively, this software may be distributed under the terms of the
+ * GNU General Public License ("GPL") version 2 as published by the Free
+ * Software Foundation.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "server.h"
+#include <net/sock.h>
+#include <linux/module.h>
+
+/* Number of messages to send before rescheduling */
+#define MAX_SEND_MSG_COUNT 25
+#define	CF_CONNECTED 1
+
+#define sock2con(x) ((struct tipc_conn *)(x)->sk_user_data)
+
+/**
+ * struct tipc_conn - TIPC connection structure
+ * @kref: reference counter to connection object
+ * @conid: connection identifier
+ * @sock: socket handler associated with connection
+ * @flags: indicates connection state
+ * @server: pointer to connected server
+ * @outqueue: pointer to first outbound message in queue
+ * @outqueue_lock: controll access to the outqueue
+ * @rx_action: what to do when connection socket is active
+ * @list: list of connection objects for its server
+ * @rwork: receive work item
+ * @swork: send work item
+ * @usr_data: user-specified field
+ */
+struct tipc_conn {
+	struct kref kref;
+	unsigned int conid;
+	struct socket *sock;
+	unsigned long flags;
+	struct tipc_server *server;
+	struct list_head outqueue;
+	spinlock_t outqueue_lock;
+	int (*rx_action) (struct tipc_conn *con);
+	struct hlist_node list;
+	struct work_struct rwork;
+	struct work_struct swork;
+	void *usr_data;
+};
+
+/* An entry waiting to be sent */
+struct outqueue_entry {
+	struct list_head list;
+	struct kvec iov;
+	struct sockaddr_tipc dest;
+};
+
+static void tipc_recv_work(struct work_struct *work);
+static void tipc_send_work(struct work_struct *work);
+static void clean_outqueues(struct tipc_conn *con);
+
+static void tipc_conn_kref_release(struct kref *kref)
+{
+	struct tipc_conn *con = container_of(kref, struct tipc_conn, kref);
+	struct tipc_server *s = con->server;
+
+	if (con->sock) {
+		__module_get(con->sock->ops->owner);
+		__module_get(con->sock->sk->sk_prot_creator->owner);
+		sock_release(con->sock);
+		con->sock = NULL;
+	}
+
+	clean_outqueues(con);
+
+	if (con->conid)
+		s->tipc_conn_shutdown(con->conid, con->usr_data);
+
+	kfree(con);
+}
+
+static void conn_put(struct tipc_conn *con)
+{
+	kref_put(&con->kref, tipc_conn_kref_release);
+}
+
+static void conn_get(struct tipc_conn *con)
+{
+	kref_get(&con->kref);
+}
+
+static inline unsigned int conid_hash(unsigned int conid)
+{
+	return conid & (CONN_HASH_SIZE - 1);
+}
+
+static struct tipc_conn *tipc_conn_lookup(struct tipc_server *s,
+					  unsigned int conid)
+{
+	struct hlist_node *h;
+	struct tipc_conn *con;
+	unsigned int r;
+
+	r = conid_hash(conid);
+
+	read_lock_bh(&s->conn_hlist_lock);
+	hlist_for_each_entry(con, h, &s->conn_hlist[r], list) {
+		if (con->conid == conid) {
+			conn_get(con);
+			read_unlock_bh(&s->conn_hlist_lock);
+			return con;
+		}
+	}
+	read_unlock_bh(&s->conn_hlist_lock);
+	return NULL;
+}
+
+static void sock_data_ready(struct sock *sk, int unused)
+{
+	struct tipc_conn *con;
+
+	read_lock(&sk->sk_callback_lock);
+	con = sock2con(sk);
+	if (con && test_bit(CF_CONNECTED, &con->flags)) {
+		conn_get(con);
+		if (!queue_work(con->server->rcv_wq, &con->rwork))
+			conn_put(con);
+	}
+	read_unlock(&sk->sk_callback_lock);
+}
+
+static void sock_write_space(struct sock *sk)
+{
+	struct tipc_conn *con;
+
+	read_lock(&sk->sk_callback_lock);
+	con = sock2con(sk);
+	if (con && test_bit(CF_CONNECTED, &con->flags)) {
+		conn_get(con);
+		if (!queue_work(con->server->send_wq, &con->swork))
+			conn_put(con);
+	}
+	read_unlock(&sk->sk_callback_lock);
+}
+
+/**
+ * tipc_register_callbacks - register socket callbacks
+ */
+static void tipc_register_callbacks(struct socket *sock, struct tipc_conn *con)
+{
+	struct sock *sk = sock->sk;
+
+	write_lock_bh(&sk->sk_callback_lock);
+
+	sk->sk_data_ready = sock_data_ready;
+	sk->sk_write_space = sock_write_space;
+	sk->sk_user_data = con;
+
+	con->sock = sock;
+
+	write_unlock_bh(&sk->sk_callback_lock);
+}
+
+/**
+ * tipc_unregister_callbacks - unregister socket callbacks
+ */
+static void tipc_unregister_callbacks(struct tipc_conn *con)
+{
+	struct sock *sk = con->sock->sk;
+
+	write_lock_bh(&sk->sk_callback_lock);
+	sk->sk_user_data = NULL;
+	write_unlock_bh(&sk->sk_callback_lock);
+}
+
+/**
+ * tipc_close_conn - close connection
+ */
+static void tipc_close_conn(struct tipc_conn *con)
+{
+	struct tipc_server *s = con->server;
+
+	if (test_and_clear_bit(CF_CONNECTED, &con->flags)) {
+		write_lock_bh(&s->conn_hlist_lock);
+		hlist_del(&con->list);
+		write_unlock_bh(&s->conn_hlist_lock);
+
+		tipc_unregister_callbacks(con);
+
+		/*
+		 * We shouldn't flush pending works as we may be in the
+		 * thread. In fact the races with pending rx/tx work structs
+		 * are harmless for us here as we have already deleted this
+		 * connection from server connection list and set
+		 * sk->sk_user_data to 0 before release connection object.
+		 */
+		kernel_sock_shutdown(con->sock, SHUT_RDWR);
+
+		conn_put(con);
+	}
+}
+
+/**
+ * get_conid - get unique connection ID
+ */
+static unsigned int get_conid(struct tipc_server *s)
+{
+	struct hlist_node *h;
+	struct tipc_conn *con;
+	unsigned int r;
+	unsigned int i;
+
+	for (i = 0; i < 0xffffffff; i++) {
+		r = conid_hash(s->conid);
+
+		if (hlist_empty(&s->conn_hlist[r]))
+			return s->conid;
+
+		hlist_for_each_entry(con, h, &s->conn_hlist[r], list) {
+			if (con->conid != s->conid)
+				return s->conid;
+		}
+		s->conid++;
+	}
+	panic("failed to allocate unique connection ID\n");
+	return 0;
+}
+
+/**
+ * alloc_tipc_conn - allocate connection object
+ */
+static struct tipc_conn *alloc_tipc_conn(struct tipc_server *s)
+{
+	struct tipc_conn *con;
+	int r;
+
+	con = kzalloc(sizeof(struct tipc_conn), GFP_ATOMIC);
+	if (!con)
+		return NULL;
+
+	write_lock_bh(&s->conn_hlist_lock);
+	r = conid_hash(get_conid(s));
+	hlist_add_head(&con->list, &s->conn_hlist[r]);
+	con->conid = s->conid++;
+	write_unlock_bh(&s->conn_hlist_lock);
+
+	set_bit(CF_CONNECTED, &con->flags);
+	con->server = s;
+	kref_init(&con->kref);
+	INIT_LIST_HEAD(&con->outqueue);
+	spin_lock_init(&con->outqueue_lock);
+	INIT_WORK(&con->swork, tipc_send_work);
+	INIT_WORK(&con->rwork, tipc_recv_work);
+
+	return con;
+}
+
+/**
+ * tipc_receive_from_sock - receive data from remote end
+ */
+static int tipc_receive_from_sock(struct tipc_conn *con)
+{
+	struct kvec iov;
+	void *buf;
+	int ret;
+	struct sockaddr_tipc addr;
+	struct msghdr msg = {};
+	struct tipc_server *s = con->server;
+
+	buf = kmem_cache_alloc(s->rcvbuf_cache, GFP_ATOMIC);
+	if (!buf) {
+		ret = -ENOMEM;
+		goto out_close;
+	}
+
+	iov.iov_base = buf;
+	iov.iov_len = s->max_rcvbuf_size;
+	msg.msg_name = &addr;
+	ret = kernel_recvmsg(con->sock, &msg, &iov, 1, iov.iov_len,
+			     MSG_DONTWAIT);
+	if (ret <= 0) {
+		kmem_cache_free(s->rcvbuf_cache, buf);
+		goto out_close;
+	}
+
+	s->tipc_conn_recvmsg(con->conid, &addr, con->usr_data, buf, ret);
+
+	kmem_cache_free(s->rcvbuf_cache, buf);
+
+	return 0;
+
+out_close:
+	if (ret != -EWOULDBLOCK)
+		tipc_close_conn(con);
+	else if (ret == 0)
+		/* Don't return success if we really got EOF */
+		ret = -EAGAIN;
+
+	return ret;
+}
+
+/**
+ * tipc_accept_from_sock - listen and accept a new connection
+ */
+static int tipc_accept_from_sock(struct tipc_conn *con)
+{
+	struct socket *newsock;
+	struct tipc_conn *newcon;
+	int ret;
+	struct tipc_server *s = con->server;
+
+	ret = kernel_accept(con->sock, &newsock, O_NONBLOCK);
+	if (ret < 0)
+		goto exit;
+
+	newcon = alloc_tipc_conn(con->server);
+	if (!newcon) {
+		ret = -ENOMEM;
+		sock_release(newsock);
+		goto exit;
+	}
+
+	newcon->rx_action = tipc_receive_from_sock;
+	tipc_register_callbacks(newsock, newcon);
+
+	/* Notify new connection is incoming */
+	newcon->usr_data = s->tipc_conn_new(newcon->conid);
+
+	module_put(newsock->ops->owner);
+	module_put(newsock->sk->sk_prot_creator->owner);
+
+exit:
+	return ret;
+}
+
+/**
+ * tipc_create_listen_sock - create and listen server socket
+ */
+static struct socket *tipc_create_listen_sock(struct tipc_conn *con)
+{
+	int ret;
+	struct socket *sock = NULL;
+	struct tipc_server *s = con->server;
+
+	ret = sock_create_kern(AF_TIPC, s->type, 0, &sock);
+	if (ret < 0)
+		return NULL;
+	ret = kernel_setsockopt(sock, SOL_TIPC, TIPC_IMPORTANCE,
+			(char *)&s->imp, sizeof(s->imp));
+	if (ret < 0)
+		goto create_err;
+	ret = kernel_bind(sock, (struct sockaddr *)s->saddr,
+			  sizeof(*s->saddr));
+	if (ret < 0)
+		goto create_err;
+
+	switch (s->type) {
+	case SOCK_STREAM:
+	case SOCK_SEQPACKET:
+		con->rx_action = tipc_accept_from_sock;
+
+		ret = kernel_listen(sock, 0);
+		if (ret < 0)
+			goto create_err;
+		break;
+	case SOCK_DGRAM:
+	case SOCK_RDM:
+		con->rx_action = tipc_receive_from_sock;
+		break;
+	default:
+		pr_err("Unknown socket type %d\n", s->type);
+		goto create_err;
+	}
+
+	/*
+	 * Hack: we put TIPC module twice since its refcount has been
+	 * increased two times when socket is created, otherwise, the
+	 * module cannot be unloaded at all. But it's safe to descrease
+	 * its refcount here because the lifetime of the socket is always
+	 * same as TIPC module. Likely we must inscrease it when the
+	 * socket is closed.
+	 */
+	module_put(sock->ops->owner);
+	module_put(sock->sk->sk_prot_creator->owner);
+
+	return sock;
+
+create_err:
+	sock_release(sock);
+	con->sock = NULL;
+	return NULL;
+}
+
+/**
+ * tipc_open_listening_sock - create server to listen connections on its socket
+ */
+static int tipc_open_listening_sock(struct tipc_server *server)
+{
+	struct socket *sock;
+	struct tipc_conn *con;
+	int ret = -EINVAL;
+
+	con = alloc_tipc_conn(server);
+	if (!con)
+		return -ENOMEM;
+
+	sock = tipc_create_listen_sock(con);
+	if (sock) {
+		tipc_register_callbacks(sock, con);
+		ret = 0;
+	}
+
+	return ret;
+}
+
+static struct outqueue_entry *alloc_entry(void *data, int len)
+{
+	struct outqueue_entry *entry;
+	void *buf;
+
+	entry = kmalloc(sizeof(struct outqueue_entry), GFP_ATOMIC);
+	if (!entry)
+		return NULL;
+
+	buf = kmalloc(len, GFP_ATOMIC);
+	if (!buf) {
+		kfree(entry);
+		return NULL;
+	}
+
+	memcpy(buf, data, len);
+	entry->iov.iov_base = buf;
+	entry->iov.iov_len = len;
+
+	return entry;
+}
+
+static void free_entry(struct outqueue_entry *e)
+{
+	kfree(e->iov.iov_base);
+	kfree(e);
+}
+
+/**
+ * clean_outqueues - discard all entries on the outqueues
+ */
+static void clean_outqueues(struct tipc_conn *con)
+{
+	struct outqueue_entry *e, *safe;
+
+	spin_lock_bh(&con->outqueue_lock);
+	list_for_each_entry_safe(e, safe, &con->outqueue, list) {
+		list_del(&e->list);
+		free_entry(e);
+	}
+	spin_unlock_bh(&con->outqueue_lock);
+}
+
+/**
+ * tipc_conn_sendmsg - send message to server with connection ID
+ */
+int tipc_conn_sendmsg(struct tipc_server *s, unsigned int conid,
+		      struct sockaddr_tipc *addr, void *data, size_t len)
+{
+	struct outqueue_entry *e;
+	struct tipc_conn *con;
+
+	con = tipc_conn_lookup(s, conid);
+	if (!con)
+		return -1;
+
+	e = alloc_entry(data, len);
+	if (!e) {
+		conn_put(con);
+		return -ENOMEM;
+	}
+
+	if (addr)
+		memcpy(&e->dest, addr, sizeof(struct sockaddr_tipc));
+
+	spin_lock_bh(&con->outqueue_lock);
+	list_add_tail(&e->list, &con->outqueue);
+	spin_unlock_bh(&con->outqueue_lock);
+
+	if (test_bit(CF_CONNECTED, &con->flags)) {
+		if (!queue_work(s->send_wq, &con->swork))
+			conn_put(con);
+	}
+
+	return 0;
+}
+
+/**
+ * tipc_conn_terminate - terminate connection with server
+ */
+void tipc_conn_terminate(struct tipc_server *s, unsigned int conid)
+{
+	struct tipc_conn *con;
+
+	con = tipc_conn_lookup(s, conid);
+	if (con) {
+		tipc_close_conn(con);
+		conn_put(con);
+	}
+}
+
+/**
+ * tipc_send_to_sock - try its best to send out all messages in its outqueue
+ */
+static void tipc_send_to_sock(struct tipc_conn *con)
+{
+	int count = 0;
+	struct tipc_server *s = con->server;
+	struct outqueue_entry *e;
+	struct msghdr msg;
+	int ret;
+
+	spin_lock_bh(&con->outqueue_lock);
+	while (1) {
+		e = list_entry(con->outqueue.next, struct outqueue_entry,
+			       list);
+		if ((struct list_head *) e == &con->outqueue)
+			break;
+		spin_unlock_bh(&con->outqueue_lock);
+
+		memset(&msg, 0, sizeof(msg));
+		msg.msg_flags = MSG_DONTWAIT;
+
+		if (s->type == SOCK_DGRAM || s->type == SOCK_RDM) {
+			msg.msg_name = &e->dest;
+			msg.msg_namelen = sizeof(struct sockaddr_tipc);
+		}
+		ret = kernel_sendmsg(con->sock, &msg, &e->iov, 1,
+				     e->iov.iov_len);
+		if (ret == -EWOULDBLOCK || ret == 0) {
+			cond_resched();
+			goto out;
+		} else if (ret < 0) {
+			goto send_err;
+		}
+
+		/* Don't starve people filling buffers */
+		if (++count >= MAX_SEND_MSG_COUNT) {
+			cond_resched();
+			count = 0;
+		}
+
+		spin_lock_bh(&con->outqueue_lock);
+		list_del(&e->list);
+		free_entry(e);
+	}
+	spin_unlock_bh(&con->outqueue_lock);
+out:
+	return;
+
+send_err:
+	tipc_close_conn(con);
+}
+
+/**
+ * tipc_recv_work - receive workqueue function
+ */
+static void tipc_recv_work(struct work_struct *work)
+{
+	struct tipc_conn *con = container_of(work, struct tipc_conn, rwork);
+	int err;
+
+	do {
+		err = con->rx_action(con);
+	} while (!err);
+
+	conn_put(con);
+}
+
+/**
+ * tipc_send_work - send workqueue function
+ */
+static void tipc_send_work(struct work_struct *work)
+{
+	struct tipc_conn *con = container_of(work, struct tipc_conn, swork);
+
+	tipc_send_to_sock(con);
+	conn_put(con);
+}
+
+/**
+ * tipc_work_stop - destroy allocated workqueues
+ */
+static void tipc_work_stop(struct tipc_server *s)
+{
+	destroy_workqueue(s->rcv_wq);
+	destroy_workqueue(s->send_wq);
+}
+
+/**
+ * tipc_work_start - allocate workqueues
+ */
+static int tipc_work_start(struct tipc_server *s)
+{
+	s->rcv_wq = alloc_workqueue("tipc_rcv", WQ_UNBOUND, 1);
+	if (!s->rcv_wq) {
+		pr_err("can't start tipc receive workqueue\n");
+		return -ENOMEM;
+	}
+
+	s->send_wq = alloc_workqueue("tipc_send", WQ_UNBOUND, 1);
+	if (!s->send_wq) {
+		pr_err("can't start tipc send workqueue\n");
+		destroy_workqueue(s->rcv_wq);
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+/**
+ * tipc_server_start - launch server
+ */
+int tipc_server_start(struct tipc_server *s)
+{
+	int ret;
+	int i;
+
+	s->conid = 0;
+	rwlock_init(&s->conn_hlist_lock);
+
+	for (i = 0; i < CONN_HASH_SIZE; i++)
+		INIT_HLIST_HEAD(&s->conn_hlist[i]);
+
+	s->rcvbuf_cache = kmem_cache_create("tipc_rcvbuf", s->max_rcvbuf_size,
+				0, SLAB_HWCACHE_ALIGN, NULL);
+	if (!s->rcvbuf_cache)
+		return -ENOMEM;
+
+	ret = tipc_work_start(s);
+	if (ret < 0) {
+		kmem_cache_destroy(s->rcvbuf_cache);
+		return ret;
+	}
+
+	ret = tipc_open_listening_sock(s);
+	return ret;
+}
+
+/**
+ * tipc_server_stop - stop server and destroy all allocated resources
+ */
+void tipc_server_stop(struct tipc_server *s)
+{
+	struct hlist_node *h, *h1;
+	struct tipc_conn *con;
+	int i;
+
+	for (i = 0; i < CONN_HASH_SIZE; i++) {
+		hlist_for_each_entry_safe(con, h, h1, &s->conn_hlist[i], list)
+			tipc_close_conn(con);
+	}
+
+	tipc_work_stop(s);
+	kmem_cache_destroy(s->rcvbuf_cache);
+}
diff --git a/net/tipc/server.h b/net/tipc/server.h
new file mode 100644
index 0000000..4b2c4cf
--- /dev/null
+++ b/net/tipc/server.h
@@ -0,0 +1,103 @@
+/*
+ * net/tipc/server.h: Include file for TIPC server code
+ *
+ * Copyright (c) 2012, Wind River Systems
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the names of the copyright holders nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * Alternatively, this software may be distributed under the terms of the
+ * GNU General Public License ("GPL") version 2 as published by the Free
+ * Software Foundation.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _TIPC_SERVER_H
+#define _TIPC_SERVER_H
+
+#include "core.h"
+
+#define TIPC_SERVER_NAME_LEN 32
+#define CONN_HASH_SIZE 32
+
+/**
+ * struct tipc_server - TIPC server structure
+ * @conid: connection identifier associated with server
+ * @conn_hlist: links to all client connections connecting to server
+ * @conn_hlist_lock: conn_hlist list lock
+ * @rcvbuf_cache: memory cache of server receive buffer
+ * @rcv_wq: receive workqueue
+ * @send_wq: send workqueue
+ * @saddr: TIPC server address
+ * @imp: message importance
+ * @type: socket type
+ * @max_rcvbuf_size: maximum permitted receive message length
+ * @name: server name
+ * @tipc_conn_new: callback will be called when new connection is incoming
+ * @tipc_conn_shutdown: callback will be called when connection is shut down
+ * @tipc_conn_recvmsg: callback will be called when message arrives
+ */
+struct tipc_server {
+	unsigned int conid;
+	struct hlist_head conn_hlist[CONN_HASH_SIZE];
+	rwlock_t conn_hlist_lock;
+	struct kmem_cache *rcvbuf_cache;
+	struct workqueue_struct *rcv_wq;
+	struct workqueue_struct *send_wq;
+	struct sockaddr_tipc *saddr;
+	int imp;
+	int type;
+	int max_rcvbuf_size;
+	const char name[TIPC_SERVER_NAME_LEN];
+	void *(*tipc_conn_new) (unsigned int conid);
+	void (*tipc_conn_shutdown) (unsigned int conid, void *usr_data);
+	void (*tipc_conn_recvmsg) (unsigned int conid,
+				   struct sockaddr_tipc *addr,
+				   void *usr_data, void *buf, size_t len);
+};
+
+/**
+ * tipc_conn_sendmsg - send message to connection
+ */
+int tipc_conn_sendmsg(struct tipc_server *s, unsigned int conid,
+		      struct sockaddr_tipc *addr, void *data, size_t len);
+
+/**
+ * tipc_conn_terminate - terminate connection with server
+ *
+ * Note: Must call it in process context since it might sleep
+ */
+void tipc_conn_terminate(struct tipc_server *s, unsigned int conid);
+
+/**
+ * tipc_server_start - start server
+ */
+int tipc_server_start(struct tipc_server *s);
+
+/**
+ * tipc_server_stop - stop server
+ */
+void tipc_server_stop(struct tipc_server *s);
+
+#endif
-- 
1.7.1