/*
 * 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 "socket.h"
#include <net/sock.h>
#include <linux/module.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 CF_SERVER               2

#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: control 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;
        struct sockaddr_tipc *saddr = s->saddr;
        struct socket *sock = con->sock;
        struct sock *sk;

        if (sock) {
                sk = sock->sk;
                if (test_bit(CF_SERVER, &con->flags)) {
                        __module_get(sock->ops->owner);
                        __module_get(sk->sk_prot_creator->owner);
                }
                saddr->scope = -TIPC_NODE_SCOPE;
                kernel_bind(sock, (struct sockaddr *)saddr, sizeof(*saddr));
                sock_release(sock);
                con->sock = NULL;

                spin_lock_bh(&s->idr_lock);
                idr_remove(&s->conn_idr, con->conid);
                s->idr_in_use--;
                spin_unlock_bh(&s->idr_lock);
        }

        tipc_clean_outqueues(con);
        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 && test_bit(CF_CONNECTED, &con->flags))
                conn_get(con);
        else
                con = NULL;
        spin_unlock_bh(&s->idr_lock);
        return con;
}

static void sock_data_ready(struct sock *sk)
{
        struct tipc_conn *con;

        read_lock_bh(&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_bh(&sk->sk_callback_lock);
}

static void sock_write_space(struct sock *sk)
{
        struct tipc_conn *con;

        read_lock_bh(&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_bh(&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)) {
                tipc_unregister_callbacks(con);

                if (con->conid)
                        s->tipc_conn_release(con->conid, con->usr_data);

                /* 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.
                 */
                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(sock_net(con->sock->sk), 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 = kernel_accept(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);
        if (!newcon->usr_data) {
                sock_release(newsock);
                return -ENOMEM;
        }

        /* Wake up receive process in case of 'SYN+' message */
        newsock->sk->sk_data_ready(newsock->sk);
        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 = sock_create_kern(s->net, AF_TIPC, SOCK_SEQPACKET, 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;
        }

        /* As server's listening socket owner and creator is the same module,
         * we have to decrease TIPC module reference count to guarantee that
         * it remains zero after the server socket is created, otherwise,
         * executing "rmmod" command is unable to make TIPC module deleted
         * after TIPC module is inserted successfully.
         *
         * However, the reference count is ever increased twice in
         * sock_create_kern(): one is to increase the reference count of owner
         * of TIPC socket's proto_ops struct; another is to increment the
         * reference count of owner of TIPC proto struct. Therefore, we must
         * decrement the module reference count twice to ensure that it keeps
         * zero after server's listening socket is created. Of course, we
         * must bump the module reference count twice as well before the socket
         * is closed.
         */
        module_put(sock->ops->owner);
        module_put(sock->sk->sk_prot_creator->owner);
        set_bit(CF_SERVER, &con->flags);

        return sock;

create_err:
        kernel_sock_shutdown(sock, SHUT_RDWR);
        sock_release(sock);
        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) {
                idr_remove(&s->conn_idr, con->conid);
                s->idr_in_use--;
                kfree(con);
                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 = kmemdup(data, len, GFP_ATOMIC);
        if (!buf) {
                kfree(entry);
                return NULL;
        }

        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;

        if (!test_bit(CF_CONNECTED, &con->flags)) {
                conn_put(con);
                return 0;
        }

        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 (!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 (test_bit(CF_CONNECTED, &con->flags)) {
                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_ordered_workqueue("tipc_rcv", 0);
        if (!s->rcv_wq) {
                pr_err("can't start tipc receive workqueue\n");
                return -ENOMEM;
        }

        s->send_wq = alloc_ordered_workqueue("tipc_send", 0);
        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;
        }
        ret = tipc_open_listening_sock(s);
        if (ret < 0) {
                tipc_work_stop(s);
                kmem_cache_destroy(s->rcvbuf_cache);
                return ret;
        }
        return ret;
}

void tipc_server_stop(struct tipc_server *s)
{
        struct tipc_conn *con;
        int id;

        spin_lock_bh(&s->idr_lock);
        for (id = 0; s->idr_in_use; id++) {
                con = idr_find(&s->conn_idr, id);
                if (con) {
                        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);
}