/*
 * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
 */

/*
 * This file contains code imported from the OFED rds source file threads.c
 * Oracle elects to have and use the contents of threads.c under and governed
 * by the OpenIB.org BSD license (see below for full license text). However,
 * the following notice accompanied the original version of this file:
 */

/*
 * Copyright (c) 2006 Oracle.  All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * OpenIB.org BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - 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.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 */
#include <sys/rds.h>
#include <sys/sunddi.h>
#include <sys/containerof.h>

#include <sys/ib/clients/rdsv3/rdsv3.h>
#include <sys/ib/clients/rdsv3/rdsv3_debug.h>

/*
 * All of connection management is simplified by serializing it through
 * work queues that execute in a connection managing thread.
 *
 * TCP wants to send acks through sendpage() in response to data_ready(),
 * but it needs a process context to do so.
 *
 * The receive paths need to allocate but can't drop packets (!) so we have
 * a thread around to block allocating if the receive fast path sees an
 * allocation failure.
 */

/*
 * Grand Unified Theory of connection life cycle:
 * At any point in time, the connection can be in one of these states:
 * DOWN, CONNECTING, UP, DISCONNECTING, ERROR
 *
 * The following transitions are possible:
 *  ANY           -> ERROR
 *  UP            -> DISCONNECTING
 *  ERROR         -> DISCONNECTING
 *  DISCONNECTING -> DOWN
 *  DOWN          -> CONNECTING
 *  CONNECTING    -> UP
 *
 * Transition to state DISCONNECTING/DOWN:
 *  -   Inside the shutdown worker; synchronizes with xmit path
 *      through c_send_lock, and with connection management callbacks
 *      via c_cm_lock.
 *
 *      For receive callbacks, we rely on the underlying transport
 *      (TCP, IB/RDMA) to provide the necessary synchronisation.
 */
struct rdsv3_workqueue_struct_s *rdsv3_wq;

void
rdsv3_connect_complete(struct rdsv3_connection *conn)
{
        RDSV3_DPRINTF4("rdsv3_connect_complete", "Enter(conn: %p)", conn);

        if (!rdsv3_conn_transition(conn, RDSV3_CONN_CONNECTING,
            RDSV3_CONN_UP)) {
#ifndef __lock_lint
                RDSV3_DPRINTF2("rdsv3_connect_complete",
                    "%s: Cannot transition to state UP, "
                    "current state is %d",
                    __func__,
                    atomic_get(&conn->c_state));
#endif
                conn->c_state = RDSV3_CONN_ERROR;
                rdsv3_queue_work(rdsv3_wq, &conn->c_down_w);
                return;
        }

        RDSV3_DPRINTF2("rdsv3_connect_complete",
            "conn %p for %u.%u.%u.%u to %u.%u.%u.%u complete",
            conn, NIPQUAD(conn->c_laddr), NIPQUAD(conn->c_faddr));

        conn->c_reconnect_jiffies = 0;
        conn->c_last_connect_jiffies = ddi_get_lbolt();

        set_bit(0, &conn->c_map_queued);
        rdsv3_queue_delayed_work(rdsv3_wq, &conn->c_send_w, 0);
        rdsv3_queue_delayed_work(rdsv3_wq, &conn->c_recv_w, 0);

        RDSV3_DPRINTF4("rdsv3_connect_complete", "Return(conn: %p)", conn);
}

/*
 * This random exponential backoff is relied on to eventually resolve racing
 * connects.
 *
 * If connect attempts race then both parties drop both connections and come
 * here to wait for a random amount of time before trying again.  Eventually
 * the backoff range will be so much greater than the time it takes to
 * establish a connection that one of the pair will establish the connection
 * before the other's random delay fires.
 *
 * Connection attempts that arrive while a connection is already established
 * are also considered to be racing connects.  This lets a connection from
 * a rebooted machine replace an existing stale connection before the transport
 * notices that the connection has failed.
 *
 * We should *always* start with a random backoff; otherwise a broken connection
 * will always take several iterations to be re-established.
 */
void
rdsv3_queue_reconnect(struct rdsv3_connection *conn)
{
        unsigned long rand;

        RDSV3_DPRINTF2("rdsv3_queue_reconnect",
            "conn %p for %u.%u.%u.%u to %u.%u.%u.%u reconnect jiffies %lu",
            conn, NIPQUAD(conn->c_laddr), NIPQUAD(conn->c_faddr),
            conn->c_reconnect_jiffies);

        set_bit(RDSV3_RECONNECT_PENDING, &conn->c_flags);
        if (conn->c_reconnect_jiffies == 0) {
                conn->c_reconnect_jiffies = rdsv3_sysctl_reconnect_min_jiffies;
                rdsv3_queue_delayed_work(rdsv3_wq, &conn->c_conn_w, 0);
                return;
        }

        (void) random_get_pseudo_bytes((uint8_t *)&rand, sizeof (rand));

        RDSV3_DPRINTF5("rdsv3",
            "%lu delay %lu ceil conn %p for %u.%u.%u.%u -> %u.%u.%u.%u",
            rand % conn->c_reconnect_jiffies, conn->c_reconnect_jiffies,
            conn, NIPQUAD(conn->c_laddr), NIPQUAD(conn->c_faddr));

        rdsv3_queue_delayed_work(rdsv3_wq, &conn->c_conn_w,
            rand % conn->c_reconnect_jiffies);

        conn->c_reconnect_jiffies = min(conn->c_reconnect_jiffies * 2,
            rdsv3_sysctl_reconnect_max_jiffies);
}

void
rdsv3_connect_worker(struct rdsv3_work_s *work)
{
        struct rdsv3_connection *conn = __containerof(work,
            struct rdsv3_connection, c_conn_w.work);
        int ret;

        RDSV3_DPRINTF2("rdsv3_connect_worker", "Enter(work: %p)", work);

        clear_bit(RDSV3_RECONNECT_PENDING, &conn->c_flags);
        if (rdsv3_conn_transition(conn, RDSV3_CONN_DOWN,
            RDSV3_CONN_CONNECTING)) {
                ret = conn->c_trans->conn_connect(conn);

                RDSV3_DPRINTF5("rdsv3",
                    "connect conn %p for %u.%u.%u.%u -> %u.%u.%u.%u "
                    "ret %d", conn, NIPQUAD(conn->c_laddr),
                    NIPQUAD(conn->c_faddr), ret);

                RDSV3_DPRINTF2("rdsv3_connect_worker",
                    "conn %p for %u.%u.%u.%u to %u.%u.%u.%u dispatched, ret %d",
                    conn, NIPQUAD(conn->c_laddr), NIPQUAD(conn->c_faddr), ret);

                if (ret) {
                        if (rdsv3_conn_transition(conn, RDSV3_CONN_CONNECTING,
                            RDSV3_CONN_DOWN))
                                rdsv3_queue_reconnect(conn);
                        else {
                                RDSV3_DPRINTF2("rdsv3_connect_worker",
                                    "RDS: connect failed: %p", conn);
                                rdsv3_conn_drop(conn);
                        }
                }
        }

        RDSV3_DPRINTF2("rdsv3_connect_worker", "Return(work: %p)", work);
}

void
rdsv3_send_worker(struct rdsv3_work_s *work)
{
        struct rdsv3_connection *conn = __containerof(work,
            struct rdsv3_connection, c_send_w.work);
        int ret;

        RDSV3_DPRINTF4("rdsv3_send_worker", "Enter(work: %p)", work);

        if (rdsv3_conn_state(conn) == RDSV3_CONN_UP) {
                ret = rdsv3_send_xmit(conn);
                RDSV3_DPRINTF5("rdsv3", "conn %p ret %d", conn, ret);
                switch (ret) {
                case -EAGAIN:
                        rdsv3_stats_inc(s_send_immediate_retry);
                        rdsv3_queue_delayed_work(rdsv3_wq, &conn->c_send_w, 0);
                        break;
                case -ENOMEM:
                        rdsv3_stats_inc(s_send_delayed_retry);
                        rdsv3_queue_delayed_work(rdsv3_wq, &conn->c_send_w, 2);
                default:
                        break;
                }
        }

        RDSV3_DPRINTF4("rdsv3_send_worker", "Return(work: %p)", work);
}

void
rdsv3_recv_worker(struct rdsv3_work_s *work)
{
        struct rdsv3_connection *conn = __containerof(work,
            struct rdsv3_connection, c_recv_w.work);
        int ret;

        RDSV3_DPRINTF4("rdsv3_recv_worker", "Enter(work: %p)", work);

        if (rdsv3_conn_state(conn) == RDSV3_CONN_UP) {
                ret = conn->c_trans->recv(conn);
                RDSV3_DPRINTF5("rdsv3", "conn %p ret %d", conn, ret);
                switch (ret) {
                case -EAGAIN:
                        rdsv3_stats_inc(s_recv_immediate_retry);
                        rdsv3_queue_delayed_work(rdsv3_wq, &conn->c_recv_w, 0);
                        break;
                case -ENOMEM:
                        rdsv3_stats_inc(s_recv_delayed_retry);
                        rdsv3_queue_delayed_work(rdsv3_wq, &conn->c_recv_w, 2);
                default:
                        break;
                }
        }

        RDSV3_DPRINTF4("rdsv3_recv_worker", "Return(work: %p)", work);
}

void
rdsv3_shutdown_worker(struct rdsv3_work_s *work)
{
        struct rdsv3_connection *conn = __containerof(work,
            struct rdsv3_connection, c_down_w);
        rdsv3_conn_shutdown(conn);
}

#define time_after(a, b)        ((long)(b) - (long)(a) < 0)

void
rdsv3_reaper_worker(struct rdsv3_work_s *work)
{
        struct rdsv3_connection *conn = __containerof(work,
            struct rdsv3_connection, c_reap_w.work);

        if (rdsv3_conn_state(conn) != RDSV3_CONN_UP &&
            !time_after(conn->c_last_connect_jiffies,
            ddi_get_lbolt() - RDSV3_REAPER_WAIT_JIFFIES)) {
                rdsv3_conn_destroy(conn);
        } else {
                rdsv3_queue_delayed_work(rdsv3_wq, &conn->c_reap_w,
                    RDSV3_REAPER_WAIT_JIFFIES);
        }
}

void
rdsv3_threads_exit(void)
{
        rdsv3_destroy_task_workqueue(rdsv3_wq);
}

int
rdsv3_threads_init(void)
{
        rdsv3_wq = rdsv3_create_task_workqueue("krdsd");
        if (!rdsv3_wq)
                return (-ENOMEM);

        return (0);
}