/*
 * net/tipc/server.c: TIPC server infrastructure
 *
 * Copyright (c) 2012-2013, Wind River Systems
 * Copyright (c) 2017-2018, Ericsson AB
 * 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 "subscr.h"
#include "topsrv.h"
#include "core.h"
#include "socket.h"
#include "addr.h"
#include "msg.h"
#include "bearer.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 TIPC_SERVER_NAME_LEN    32

/**
 * struct tipc_topsrv - TIPC server structure
 * @conn_idr: identifier set of connection
 * @idr_lock: protect the connection identifier set
 * @idr_in_use: amount of allocated identifier entry
 * @net: network namspace instance
 * @awork: accept work item
 * @rcv_wq: receive workqueue
 * @send_wq: send workqueue
 * @listener: topsrv listener socket
 * @name: server name
 */
struct tipc_topsrv {
        struct idr conn_idr;
        spinlock_t idr_lock; /* for idr list */
        int idr_in_use;
        struct net *net;
        struct work_struct awork;
        struct workqueue_struct *rcv_wq;
        struct workqueue_struct *send_wq;
        struct socket *listener;
        char name[TIPC_SERVER_NAME_LEN];
};

/**
 * 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
 * @sub_list: lsit to all pertaing subscriptions
 * @sub_lock: lock protecting the subscription list
 * @rwork: receive work item
 * @outqueue: pointer to first outbound message in queue
 * @outqueue_lock: control access to the outqueue
 * @swork: send work item
 */
struct tipc_conn {
        struct kref kref;
        int conid;
        struct socket *sock;
        unsigned long flags;
        struct tipc_topsrv *server;
        struct list_head sub_list;
        spinlock_t sub_lock; /* for subscription list */
        struct work_struct rwork;
        struct list_head outqueue;
        spinlock_t outqueue_lock; /* for outqueue */
        struct work_struct swork;
};

/* An entry waiting to be sent */
struct outqueue_entry {
        bool inactive;
        struct tipc_event evt;
        struct list_head list;
};

static void tipc_conn_recv_work(struct work_struct *work);
static void tipc_conn_send_work(struct work_struct *work);
static void tipc_topsrv_kern_evt(struct net *net, struct tipc_event *evt);
static void tipc_conn_delete_sub(struct tipc_conn *con, struct tipc_subscr *s);

static bool connected(struct tipc_conn *con)
{
        return con && test_bit(CF_CONNECTED, &con->flags);
}

static void tipc_conn_kref_release(struct kref *kref)
{
        struct tipc_conn *con = container_of(kref, struct tipc_conn, kref);
        struct tipc_topsrv *s = con->server;
        struct outqueue_entry *e, *safe;

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

        spin_lock_bh(&con->outqueue_lock);
        list_for_each_entry_safe(e, safe, &con->outqueue, list) {
                list_del(&e->list);
                kfree(e);
        }
        spin_unlock_bh(&con->outqueue_lock);
        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 void tipc_conn_close(struct tipc_conn *con)
{
        struct sock *sk = con->sock->sk;
        bool disconnect = false;

        write_lock_bh(&sk->sk_callback_lock);
        disconnect = test_and_clear_bit(CF_CONNECTED, &con->flags);

        if (disconnect) {
                sk->sk_user_data = NULL;
                tipc_conn_delete_sub(con, NULL);
        }
        write_unlock_bh(&sk->sk_callback_lock);

        /* Handle concurrent calls from sending and receiving threads */
        if (!disconnect)
                return;

        /* Don't flush pending works, -just let them expire */
        kernel_sock_shutdown(con->sock, SHUT_RDWR);

        conn_put(con);
}

static struct tipc_conn *tipc_conn_alloc(struct tipc_topsrv *s)
{
        struct tipc_conn *con;
        int ret;

        con = kzalloc(sizeof(*con), GFP_ATOMIC);
        if (!con)
                return ERR_PTR(-ENOMEM);

        kref_init(&con->kref);
        INIT_LIST_HEAD(&con->outqueue);
        INIT_LIST_HEAD(&con->sub_list);
        spin_lock_init(&con->outqueue_lock);
        spin_lock_init(&con->sub_lock);
        INIT_WORK(&con->swork, tipc_conn_send_work);
        INIT_WORK(&con->rwork, tipc_conn_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 struct tipc_conn *tipc_conn_lookup(struct tipc_topsrv *s, int conid)
{
        struct tipc_conn *con;

        spin_lock_bh(&s->idr_lock);
        con = idr_find(&s->conn_idr, conid);
        if (!connected(con) || !kref_get_unless_zero(&con->kref))
                con = NULL;
        spin_unlock_bh(&s->idr_lock);
        return con;
}

/* tipc_conn_delete_sub - delete a specific or all subscriptions
 * for a given subscriber
 */
static void tipc_conn_delete_sub(struct tipc_conn *con, struct tipc_subscr *s)
{
        struct tipc_net *tn = tipc_net(con->server->net);
        struct list_head *sub_list = &con->sub_list;
        struct tipc_subscription *sub, *tmp;

        spin_lock_bh(&con->sub_lock);
        list_for_each_entry_safe(sub, tmp, sub_list, sub_list) {
                if (!s || !memcmp(s, &sub->evt.s, sizeof(*s))) {
                        tipc_sub_unsubscribe(sub);
                        atomic_dec(&tn->subscription_count);
                        if (s)
                                break;
                }
        }
        spin_unlock_bh(&con->sub_lock);
}

static void tipc_conn_send_to_sock(struct tipc_conn *con)
{
        struct list_head *queue = &con->outqueue;
        struct tipc_topsrv *srv = con->server;
        struct outqueue_entry *e;
        struct tipc_event *evt;
        struct msghdr msg;
        struct kvec iov;
        int count = 0;
        int ret;

        spin_lock_bh(&con->outqueue_lock);

        while (!list_empty(queue)) {
                e = list_first_entry(queue, struct outqueue_entry, list);
                evt = &e->evt;
                spin_unlock_bh(&con->outqueue_lock);

                if (e->inactive)
                        tipc_conn_delete_sub(con, &evt->s);

                memset(&msg, 0, sizeof(msg));
                msg.msg_flags = MSG_DONTWAIT;
                iov.iov_base = evt;
                iov.iov_len = sizeof(*evt);
                msg.msg_name = NULL;

                if (con->sock) {
                        ret = kernel_sendmsg(con->sock, &msg, &iov,
                                             1, sizeof(*evt));
                        if (ret == -EWOULDBLOCK || ret == 0) {
                                cond_resched();
                                return;
                        } else if (ret < 0) {
                                return tipc_conn_close(con);
                        }
                } else {
                        tipc_topsrv_kern_evt(srv->net, evt);
                }

                /* 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);
                kfree(e);
        }
        spin_unlock_bh(&con->outqueue_lock);
}

static void tipc_conn_send_work(struct work_struct *work)
{
        struct tipc_conn *con = container_of(work, struct tipc_conn, swork);

        if (connected(con))
                tipc_conn_send_to_sock(con);

        conn_put(con);
}

/* tipc_topsrv_queue_evt() - interrupt level call from a subscription instance
 * The queued work is launched into tipc_conn_send_work()->tipc_conn_send_to_sock()
 */
void tipc_topsrv_queue_evt(struct net *net, int conid,
                           u32 event, struct tipc_event *evt)
{
        struct tipc_topsrv *srv = tipc_topsrv(net);
        struct outqueue_entry *e;
        struct tipc_conn *con;

        con = tipc_conn_lookup(srv, conid);
        if (!con)
                return;

        if (!connected(con))
                goto err;

        e = kmalloc(sizeof(*e), GFP_ATOMIC);
        if (!e)
                goto err;
        e->inactive = (event == TIPC_SUBSCR_TIMEOUT);
        memcpy(&e->evt, evt, sizeof(*evt));
        spin_lock_bh(&con->outqueue_lock);
        list_add_tail(&e->list, &con->outqueue);
        spin_unlock_bh(&con->outqueue_lock);

        if (queue_work(srv->send_wq, &con->swork))
                return;
err:
        conn_put(con);
}

/* tipc_conn_write_space - interrupt callback after a sendmsg EAGAIN
 * Indicates that there now is more space in the send buffer
 * The queued work is launched into tipc_send_work()->tipc_conn_send_to_sock()
 */
static void tipc_conn_write_space(struct sock *sk)
{
        struct tipc_conn *con;

        read_lock_bh(&sk->sk_callback_lock);
        con = sk->sk_user_data;
        if (connected(con)) {
                conn_get(con);
                if (!queue_work(con->server->send_wq, &con->swork))
                        conn_put(con);
        }
        read_unlock_bh(&sk->sk_callback_lock);
}

static int tipc_conn_rcv_sub(struct tipc_topsrv *srv,
                             struct tipc_conn *con,
                             struct tipc_subscr *s)
{
        struct tipc_net *tn = tipc_net(srv->net);
        struct tipc_subscription *sub;
        u32 s_filter = tipc_sub_read(s, filter);

        if (s_filter & TIPC_SUB_CANCEL) {
                tipc_sub_write(s, filter, s_filter & ~TIPC_SUB_CANCEL);
                tipc_conn_delete_sub(con, s);
                return 0;
        }
        if (atomic_read(&tn->subscription_count) >= TIPC_MAX_SUBSCR) {
                pr_warn("Subscription rejected, max (%u)\n", TIPC_MAX_SUBSCR);
                return -1;
        }
        sub = tipc_sub_subscribe(srv->net, s, con->conid);
        if (!sub)
                return -1;
        atomic_inc(&tn->subscription_count);
        spin_lock_bh(&con->sub_lock);
        list_add(&sub->sub_list, &con->sub_list);
        spin_unlock_bh(&con->sub_lock);
        return 0;
}

static int tipc_conn_rcv_from_sock(struct tipc_conn *con)
{
        struct tipc_topsrv *srv = con->server;
        struct sock *sk = con->sock->sk;
        struct msghdr msg = {};
        struct tipc_subscr s;
        struct kvec iov;
        int ret;

        iov.iov_base = &s;
        iov.iov_len = sizeof(s);
        msg.msg_name = NULL;
        iov_iter_kvec(&msg.msg_iter, READ, &iov, 1, iov.iov_len);
        ret = sock_recvmsg(con->sock, &msg, MSG_DONTWAIT);
        if (ret == -EWOULDBLOCK)
                return -EWOULDBLOCK;
        if (ret == sizeof(s)) {
                read_lock_bh(&sk->sk_callback_lock);
                /* RACE: the connection can be closed in the meantime */
                if (likely(connected(con)))
                        ret = tipc_conn_rcv_sub(srv, con, &s);
                read_unlock_bh(&sk->sk_callback_lock);
                if (!ret)
                        return 0;
        }

        tipc_conn_close(con);
        return ret;
}

static void tipc_conn_recv_work(struct work_struct *work)
{
        struct tipc_conn *con = container_of(work, struct tipc_conn, rwork);
        int count = 0;

        while (connected(con)) {
                if (tipc_conn_rcv_from_sock(con))
                        break;

                /* Don't flood Rx machine */
                if (++count >= MAX_RECV_MSG_COUNT) {
                        cond_resched();
                        count = 0;
                }
        }
        conn_put(con);
}

/* tipc_conn_data_ready - interrupt callback indicating the socket has data
 * The queued work is launched into tipc_recv_work()->tipc_conn_rcv_from_sock()
 */
static void tipc_conn_data_ready(struct sock *sk)
{
        struct tipc_conn *con;

        read_lock_bh(&sk->sk_callback_lock);
        con = sk->sk_user_data;
        if (connected(con)) {
                conn_get(con);
                if (!queue_work(con->server->rcv_wq, &con->rwork))
                        conn_put(con);
        }
        read_unlock_bh(&sk->sk_callback_lock);
}

static void tipc_topsrv_accept(struct work_struct *work)
{
        struct tipc_topsrv *srv = container_of(work, struct tipc_topsrv, awork);
        struct socket *lsock = srv->listener;
        struct socket *newsock;
        struct tipc_conn *con;
        struct sock *newsk;
        int ret;

        while (1) {
                ret = kernel_accept(lsock, &newsock, O_NONBLOCK);
                if (ret < 0)
                        return;
                con = tipc_conn_alloc(srv);
                if (IS_ERR(con)) {
                        ret = PTR_ERR(con);
                        sock_release(newsock);
                        return;
                }
                /* Register callbacks */
                newsk = newsock->sk;
                write_lock_bh(&newsk->sk_callback_lock);
                newsk->sk_data_ready = tipc_conn_data_ready;
                newsk->sk_write_space = tipc_conn_write_space;
                newsk->sk_user_data = con;
                con->sock = newsock;
                write_unlock_bh(&newsk->sk_callback_lock);

                /* Wake up receive process in case of 'SYN+' message */
                newsk->sk_data_ready(newsk);
        }
}

/* tipc_topsrv_listener_data_ready - interrupt callback with connection request
 * The queued job is launched into tipc_topsrv_accept()
 */
static void tipc_topsrv_listener_data_ready(struct sock *sk)
{
        struct tipc_topsrv *srv;

        read_lock_bh(&sk->sk_callback_lock);
        srv = sk->sk_user_data;
        if (srv->listener)
                queue_work(srv->rcv_wq, &srv->awork);
        read_unlock_bh(&sk->sk_callback_lock);
}

static int tipc_topsrv_create_listener(struct tipc_topsrv *srv)
{
        struct socket *lsock = NULL;
        struct sockaddr_tipc saddr;
        struct sock *sk;
        int rc;

        rc = sock_create_kern(srv->net, AF_TIPC, SOCK_SEQPACKET, 0, &lsock);
        if (rc < 0)
                return rc;

        srv->listener = lsock;
        sk = lsock->sk;
        write_lock_bh(&sk->sk_callback_lock);
        sk->sk_data_ready = tipc_topsrv_listener_data_ready;
        sk->sk_user_data = srv;
        write_unlock_bh(&sk->sk_callback_lock);

        lock_sock(sk);
        rc = tsk_set_importance(sk, TIPC_CRITICAL_IMPORTANCE);
        release_sock(sk);
        if (rc < 0)
                goto err;

        saddr.family                    = AF_TIPC;
        saddr.addrtype                  = TIPC_ADDR_NAMESEQ;
        saddr.addr.nameseq.type         = TIPC_TOP_SRV;
        saddr.addr.nameseq.lower        = TIPC_TOP_SRV;
        saddr.addr.nameseq.upper        = TIPC_TOP_SRV;
        saddr.scope                     = TIPC_NODE_SCOPE;

        rc = kernel_bind(lsock, (struct sockaddr *)&saddr, sizeof(saddr));
        if (rc < 0)
                goto err;
        rc = kernel_listen(lsock, 0);
        if (rc < 0)
                goto 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(lsock->ops->owner);
        module_put(sk->sk_prot_creator->owner);

        return 0;
err:
        sock_release(lsock);
        return -EINVAL;
}

bool tipc_topsrv_kern_subscr(struct net *net, u32 port, u32 type, u32 lower,
                             u32 upper, u32 filter, int *conid)
{
        struct tipc_subscr sub;
        struct tipc_conn *con;
        int rc;

        sub.seq.type = type;
        sub.seq.lower = lower;
        sub.seq.upper = upper;
        sub.timeout = TIPC_WAIT_FOREVER;
        sub.filter = filter;
        *(u32 *)&sub.usr_handle = port;

        con = tipc_conn_alloc(tipc_topsrv(net));
        if (IS_ERR(con))
                return false;

        *conid = con->conid;
        con->sock = NULL;
        rc = tipc_conn_rcv_sub(tipc_topsrv(net), con, &sub);
        if (rc >= 0)
                return true;
        conn_put(con);
        return false;
}

void tipc_topsrv_kern_unsubscr(struct net *net, int conid)
{
        struct tipc_conn *con;

        con = tipc_conn_lookup(tipc_topsrv(net), conid);
        if (!con)
                return;

        test_and_clear_bit(CF_CONNECTED, &con->flags);
        tipc_conn_delete_sub(con, NULL);
        conn_put(con);
        conn_put(con);
}

static void tipc_topsrv_kern_evt(struct net *net, struct tipc_event *evt)
{
        u32 port = *(u32 *)&evt->s.usr_handle;
        u32 self = tipc_own_addr(net);
        struct sk_buff_head evtq;
        struct sk_buff *skb;

        skb = tipc_msg_create(TOP_SRV, 0, INT_H_SIZE, sizeof(*evt),
                              self, self, port, port, 0);
        if (!skb)
                return;
        msg_set_dest_droppable(buf_msg(skb), true);
        memcpy(msg_data(buf_msg(skb)), evt, sizeof(*evt));
        skb_queue_head_init(&evtq);
        __skb_queue_tail(&evtq, skb);
        tipc_loopback_trace(net, &evtq);
        tipc_sk_rcv(net, &evtq);
}

static int tipc_topsrv_work_start(struct tipc_topsrv *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;
}

static void tipc_topsrv_work_stop(struct tipc_topsrv *s)
{
        destroy_workqueue(s->rcv_wq);
        destroy_workqueue(s->send_wq);
}

static int tipc_topsrv_start(struct net *net)
{
        struct tipc_net *tn = tipc_net(net);
        const char name[] = "topology_server";
        struct tipc_topsrv *srv;
        int ret;

        srv = kzalloc(sizeof(*srv), GFP_ATOMIC);
        if (!srv)
                return -ENOMEM;

        srv->net = net;
        INIT_WORK(&srv->awork, tipc_topsrv_accept);

        strscpy(srv->name, name, sizeof(srv->name));
        tn->topsrv = srv;
        atomic_set(&tn->subscription_count, 0);

        spin_lock_init(&srv->idr_lock);
        idr_init(&srv->conn_idr);
        srv->idr_in_use = 0;

        ret = tipc_topsrv_work_start(srv);
        if (ret < 0)
                return ret;

        ret = tipc_topsrv_create_listener(srv);
        if (ret < 0)
                tipc_topsrv_work_stop(srv);

        return ret;
}

static void tipc_topsrv_stop(struct net *net)
{
        struct tipc_topsrv *srv = tipc_topsrv(net);
        struct socket *lsock = srv->listener;
        struct tipc_conn *con;
        int id;

        spin_lock_bh(&srv->idr_lock);
        for (id = 0; srv->idr_in_use; id++) {
                con = idr_find(&srv->conn_idr, id);
                if (con) {
                        spin_unlock_bh(&srv->idr_lock);
                        tipc_conn_close(con);
                        spin_lock_bh(&srv->idr_lock);
                }
        }
        __module_get(lsock->ops->owner);
        __module_get(lsock->sk->sk_prot_creator->owner);
        srv->listener = NULL;
        spin_unlock_bh(&srv->idr_lock);
        sock_release(lsock);
        tipc_topsrv_work_stop(srv);
        idr_destroy(&srv->conn_idr);
        kfree(srv);
}

int __net_init tipc_topsrv_init_net(struct net *net)
{
        return tipc_topsrv_start(net);
}

void __net_exit tipc_topsrv_exit_net(struct net *net)
{
        tipc_topsrv_stop(net);
}