tipc: introduce new TIPC server infrastructure

TIPC has two internal servers, one providing a subscription
service for topology events, and another providing the
configuration interface. These servers have previously been running
in BH context, accessing the TIPC-port (aka native) API directly.
Apart from these servers, even the TIPC socket implementation is
partially built on this API.

As this API may simultaneously be called via different paths and in
different contexts, a complex and costly lock policiy is required
in order to protect TIPC internal resources.

To eliminate the need for this complex lock policiy, we introduce
a new, generic service API that uses kernel sockets for message
passing instead of the native API. Once the toplogy and configuration
servers are converted to use this new service, all code pertaining
to the native API can be removed. This entails a significant
reduction in code amount and complexity, and opens up for a complete
rework of the locking policy in TIPC.

The new service also solves another problem:

As the current topology server works in BH context, it cannot easily
be blocked when sending of events fails due to congestion. In such
cases events may have to be silently dropped, something that is
unacceptable. Therefore, the new service keeps a dedicated outbound
queue receiving messages from BH context. Once messages are
inserted into this queue, we will immediately schedule a work from a
special workqueue. This way, messages/events from the topology server
are in reality sent in process context, and the server can block
if necessary.

Analogously, there is a new workqueue for receiving messages. Once a
notification about an arriving message is received in BH context, we
schedule a work from the receive workqueue to do the job of
receiving the message in process context.

As both sending and receive messages are now finished in processes,
subscribed events cannot be dropped any more.

As of this commit, this new server infrastructure is built, but
not actually yet called by the existing TIPC code, but since the
conversion changes required in order to use it are significant,
the addition is kept here as a separate commit.

Signed-off-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 596 insertions, 0 deletions

diff --git a/net/tipc/server.c b/net/tipc/server.c
new file mode 100644
index 000000000000..19da5abe0fa6
--- /dev/null
+++ b/net/tipc/server.c
@@ -0,0 +1,596 @@
+/*
+ * net/tipc/server.c: TIPC server infrastructure
+ *
+ * Copyright (c) 2012-2013, 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 "core.h"
+#include <net/sock.h>
+
+/* Number of messages to send before rescheduling */
+#define MAX_SEND_MSG_COUNT	25
+#define MAX_RECV_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
+ * @rwork: receive work item
+ * @usr_data: user-specified field
+ * @rx_action: what to do when connection socket is active
+ * @outqueue: pointer to first outbound message in queue
+ * @outqueue_lock: controll access to the outqueue
+ * @outqueue: list of connection objects for its server
+ * @swork: send work item
+ */
+struct tipc_conn {
+	struct kref kref;
+	int conid;
+	struct socket *sock;
+	unsigned long flags;
+	struct tipc_server *server;
+	struct work_struct rwork;
+	int (*rx_action) (struct tipc_conn *con);
+	void *usr_data;
+	struct list_head outqueue;
+	spinlock_t outqueue_lock;
+	struct work_struct swork;
+};
+
+/* 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 tipc_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) {
+		tipc_sock_release_local(con->sock);
+		con->sock = NULL;
+	}
+
+	tipc_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 struct tipc_conn *tipc_conn_lookup(struct tipc_server *s, int conid)
+{
+	struct tipc_conn *con;
+
+	spin_lock_bh(&s->idr_lock);
+	con = idr_find(&s->conn_idr, conid);
+	if (con)
+		conn_get(con);
+	spin_unlock_bh(&s->idr_lock);
+	return con;
+}
+
+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);
+}
+
+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);
+}
+
+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);
+}
+
+static void tipc_close_conn(struct tipc_conn *con)
+{
+	struct tipc_server *s = con->server;
+
+	if (test_and_clear_bit(CF_CONNECTED, &con->flags)) {
+		spin_lock_bh(&s->idr_lock);
+		idr_remove(&s->conn_idr, con->conid);
+		s->idr_in_use--;
+		spin_unlock_bh(&s->idr_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 releasing connection object.
+		 */
+		kernel_sock_shutdown(con->sock, SHUT_RDWR);
+
+		conn_put(con);
+	}
+}
+
+static struct tipc_conn *tipc_alloc_conn(struct tipc_server *s)
+{
+	struct tipc_conn *con;
+	int ret;
+
+	con = kzalloc(sizeof(struct tipc_conn), GFP_ATOMIC);
+	if (!con)
+		return ERR_PTR(-ENOMEM);
+
+	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);
+
+	spin_lock_bh(&s->idr_lock);
+	ret = idr_alloc(&s->conn_idr, con, 0, 0, GFP_ATOMIC);
+	if (ret < 0) {
+		kfree(con);
+		spin_unlock_bh(&s->idr_lock);
+		return ERR_PTR(-ENOMEM);
+	}
+	con->conid = ret;
+	s->idr_in_use++;
+	spin_unlock_bh(&s->idr_lock);
+
+	set_bit(CF_CONNECTED, &con->flags);
+	con->server = s;
+
+	return con;
+}
+
+static int tipc_receive_from_sock(struct tipc_conn *con)
+{
+	struct msghdr msg = {};
+	struct tipc_server *s = con->server;
+	struct sockaddr_tipc addr;
+	struct kvec iov;
+	void *buf;
+	int ret;
+
+	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;
+}
+
+static int tipc_accept_from_sock(struct tipc_conn *con)
+{
+	struct tipc_server *s = con->server;
+	struct socket *sock = con->sock;
+	struct socket *newsock;
+	struct tipc_conn *newcon;
+	int ret;
+
+	ret = tipc_sock_accept_local(sock, &newsock, O_NONBLOCK);
+	if (ret < 0)
+		return ret;
+
+	newcon = tipc_alloc_conn(con->server);
+	if (IS_ERR(newcon)) {
+		ret = PTR_ERR(newcon);
+		sock_release(newsock);
+		return ret;
+	}
+
+	newcon->rx_action = tipc_receive_from_sock;
+	tipc_register_callbacks(newsock, newcon);
+
+	/* Notify that new connection is incoming */
+	newcon->usr_data = s->tipc_conn_new(newcon->conid);
+
+	/* Wake up receive process in case of 'SYN+' message */
+	newsock->sk->sk_data_ready(newsock->sk, 0);
+	return ret;
+}
+
+static struct socket *tipc_create_listen_sock(struct tipc_conn *con)
+{
+	struct tipc_server *s = con->server;
+	struct socket *sock = NULL;
+	int ret;
+
+	ret = tipc_sock_create_local(s->type, &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;
+	}
+	return sock;
+
+create_err:
+	sock_release(sock);
+	con->sock = NULL;
+	return NULL;
+}
+
+static int tipc_open_listening_sock(struct tipc_server *s)
+{
+	struct socket *sock;
+	struct tipc_conn *con;
+
+	con = tipc_alloc_conn(s);
+	if (IS_ERR(con))
+		return PTR_ERR(con);
+
+	sock = tipc_create_listen_sock(con);
+	if (!sock)
+		return -EINVAL;
+
+	tipc_register_callbacks(sock, con);
+	return 0;
+}
+
+static struct outqueue_entry *tipc_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 tipc_free_entry(struct outqueue_entry *e)
+{
+	kfree(e->iov.iov_base);
+	kfree(e);
+}
+
+static void tipc_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);
+		tipc_free_entry(e);
+	}
+	spin_unlock_bh(&con->outqueue_lock);
+}
+
+int tipc_conn_sendmsg(struct tipc_server *s, 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 -EINVAL;
+
+	e = tipc_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;
+}
+
+void tipc_conn_terminate(struct tipc_server *s, int conid)
+{
+	struct tipc_conn *con;
+
+	con = tipc_conn_lookup(s, conid);
+	if (con) {
+		tipc_close_conn(con);
+		conn_put(con);
+	}
+}
+
+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 users filling buffers */
+		if (++count >= MAX_SEND_MSG_COUNT) {
+			cond_resched();
+			count = 0;
+		}
+
+		spin_lock_bh(&con->outqueue_lock);
+		list_del(&e->list);
+		tipc_free_entry(e);
+	}
+	spin_unlock_bh(&con->outqueue_lock);
+out:
+	return;
+
+send_err:
+	tipc_close_conn(con);
+}
+
+static void tipc_recv_work(struct work_struct *work)
+{
+	struct tipc_conn *con = container_of(work, struct tipc_conn, rwork);
+	int count = 0;
+
+	while (test_bit(CF_CONNECTED, &con->flags)) {
+		if (con->rx_action(con))
+			break;
+
+		/* Don't flood Rx machine */
+		if (++count >= MAX_RECV_MSG_COUNT) {
+			cond_resched();
+			count = 0;
+		}
+	}
+	conn_put(con);
+}
+
+static void tipc_send_work(struct work_struct *work)
+{
+	struct tipc_conn *con = container_of(work, struct tipc_conn, swork);
+
+	if (test_bit(CF_CONNECTED, &con->flags))
+		tipc_send_to_sock(con);
+
+	conn_put(con);
+}
+
+static void tipc_work_stop(struct tipc_server *s)
+{
+	destroy_workqueue(s->rcv_wq);
+	destroy_workqueue(s->send_wq);
+}
+
+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;
+}
+
+int tipc_server_start(struct tipc_server *s)
+{
+	int ret;
+
+	spin_lock_init(&s->idr_lock);
+	idr_init(&s->conn_idr);
+	s->idr_in_use = 0;
+
+	s->rcvbuf_cache = kmem_cache_create(s->name, 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;
+	}
+	s->enabled = 1;
+
+	return tipc_open_listening_sock(s);
+}
+
+void tipc_server_stop(struct tipc_server *s)
+{
+	struct tipc_conn *con;
+	int total = 0;
+	int id;
+
+	if (!s->enabled)
+		return;
+
+	s->enabled = 0;
+	spin_lock_bh(&s->idr_lock);
+	for (id = 0; total < s->idr_in_use; id++) {
+		con = idr_find(&s->conn_idr, id);
+		if (con) {
+			total++;
+			spin_unlock_bh(&s->idr_lock);
+			tipc_close_conn(con);
+			spin_lock_bh(&s->idr_lock);
+		}
+	}
+	spin_unlock_bh(&s->idr_lock);
+
+	tipc_work_stop(s);
+	kmem_cache_destroy(s->rcvbuf_cache);
+	idr_destroy(&s->conn_idr);
+}