connection.c

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/*
 * 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 <linux/kernel.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/export.h>
#include <net/inet_hashtables.h>

#include "rds.h"
#include "loop.h"

#define RDS_CONNECTION_HASH_BITS 12
#define RDS_CONNECTION_HASH_ENTRIES (1 << RDS_CONNECTION_HASH_BITS)
#define RDS_CONNECTION_HASH_MASK (RDS_CONNECTION_HASH_ENTRIES - 1)

/* converting this to RCU is a chore for another day.. */
static DEFINE_SPINLOCK(rds_conn_lock);
static unsigned long rds_conn_count;
static struct hlist_head rds_conn_hash[RDS_CONNECTION_HASH_ENTRIES];
static struct kmem_cache *rds_conn_slab;

static struct hlist_head *rds_conn_bucket(__be32 laddr, __be32 faddr)
{
    /* Pass NULL, don't need struct net for hash */
    unsigned long hash = inet_ehashfn(NULL,
                      be32_to_cpu(laddr), 0,
                      be32_to_cpu(faddr), 0);
    return &rds_conn_hash[hash & RDS_CONNECTION_HASH_MASK];
}

#define rds_conn_info_set(var, test, suffix) do {       \
    if (test)                       \
        var |= RDS_INFO_CONNECTION_FLAG_##suffix;   \
} while (0)

/* rcu read lock must be held or the connection spinlock */
static struct rds_connection *rds_conn_lookup(struct hlist_head *head,
                          __be32 laddr, __be32 faddr,
                          struct rds_transport *trans)
{
    struct rds_connection *conn, *ret = NULL;
    struct hlist_node *pos;

    hlist_for_each_entry_rcu(conn, pos, head, c_hash_node) {
        if (conn->c_faddr == faddr && conn->c_laddr == laddr &&
                conn->c_trans == trans) {
            ret = conn;
            break;
        }
    }
    rdsdebug("returning conn %p for %pI4 -> %pI4\n", ret,
         &laddr, &faddr);
    return ret;
}

/*
 * This is called by transports as they're bringing down a connection.
 * It clears partial message state so that the transport can start sending
 * and receiving over this connection again in the future.  It is up to
 * the transport to have serialized this call with its send and recv.
 */
static void rds_conn_reset(struct rds_connection *conn)
{
    rdsdebug("connection %pI4 to %pI4 reset\n",
      &conn->c_laddr, &conn->c_faddr);

    rds_stats_inc(s_conn_reset);
    rds_send_reset(conn);
    conn->c_flags = 0;

    /* Do not clear next_rx_seq here, else we cannot distinguish
     * retransmitted packets from new packets, and will hand all
     * of them to the application. That is not consistent with the
     * reliability guarantees of RDS. */
}

/*
 * There is only every one 'conn' for a given pair of addresses in the
 * system at a time.  They contain messages to be retransmitted and so
 * span the lifetime of the actual underlying transport connections.
 *
 * For now they are not garbage collected once they're created.  They
 * are torn down as the module is removed, if ever.
 */
static struct rds_connection *__rds_conn_create(__be32 laddr, __be32 faddr,
                       struct rds_transport *trans, gfp_t gfp,
                       int is_outgoing)
{
    struct rds_connection *conn, *parent = NULL;
    struct hlist_head *head = rds_conn_bucket(laddr, faddr);
    struct rds_transport *loop_trans;
    unsigned long flags;
    int ret;

    rcu_read_lock();
    conn = rds_conn_lookup(head, laddr, faddr, trans);
    if (conn && conn->c_loopback && conn->c_trans != &rds_loop_transport &&
        !is_outgoing) {
        /* This is a looped back IB connection, and we're
         * called by the code handling the incoming connect.
         * We need a second connection object into which we
         * can stick the other QP. */
        parent = conn;
        conn = parent->c_passive;
    }
    rcu_read_unlock();
    if (conn)
        goto out;

    conn = kmem_cache_zalloc(rds_conn_slab, gfp);
    if (!conn) {
        conn = ERR_PTR(-ENOMEM);
        goto out;
    }

    INIT_HLIST_NODE(&conn->c_hash_node);
    conn->c_laddr = laddr;
    conn->c_faddr = faddr;
    spin_lock_init(&conn->c_lock);
    conn->c_next_tx_seq = 1;

    init_waitqueue_head(&conn->c_waitq);
    INIT_LIST_HEAD(&conn->c_send_queue);
    INIT_LIST_HEAD(&conn->c_retrans);

    ret = rds_cong_get_maps(conn);
    if (ret) {
        kmem_cache_free(rds_conn_slab, conn);
        conn = ERR_PTR(ret);
        goto out;
    }

    /*
     * This is where a connection becomes loopback.  If *any* RDS sockets
     * can bind to the destination address then we'd rather the messages
     * flow through loopback rather than either transport.
     */
    loop_trans = rds_trans_get_preferred(faddr);
    if (loop_trans) {
        rds_trans_put(loop_trans);
        conn->c_loopback = 1;
        if (is_outgoing && trans->t_prefer_loopback) {
            /* "outgoing" connection - and the transport
             * says it wants the connection handled by the
             * loopback transport. This is what TCP does.
             */
            trans = &rds_loop_transport;
        }
    }

    conn->c_trans = trans;

    ret = trans->conn_alloc(conn, gfp);
    if (ret) {
        kmem_cache_free(rds_conn_slab, conn);
        conn = ERR_PTR(ret);
        goto out;
    }

    atomic_set(&conn->c_state, RDS_CONN_DOWN);
    conn->c_reconnect_jiffies = 0;
    INIT_DELAYED_WORK(&conn->c_send_w, rds_send_worker);
    INIT_DELAYED_WORK(&conn->c_recv_w, rds_recv_worker);
    INIT_DELAYED_WORK(&conn->c_conn_w, rds_connect_worker);
    INIT_WORK(&conn->c_down_w, rds_shutdown_worker);
    mutex_init(&conn->c_cm_lock);
    conn->c_flags = 0;

    rdsdebug("allocated conn %p for %pI4 -> %pI4 over %s %s\n",
      conn, &laddr, &faddr,
      trans->t_name ? trans->t_name : "[unknown]",
      is_outgoing ? "(outgoing)" : "");

    /*
     * Since we ran without holding the conn lock, someone could
     * have created the same conn (either normal or passive) in the
     * interim. We check while holding the lock. If we won, we complete
     * init and return our conn. If we lost, we rollback and return the
     * other one.
     */
    spin_lock_irqsave(&rds_conn_lock, flags);
    if (parent) {
        /* Creating passive conn */
        if (parent->c_passive) {
            trans->conn_free(conn->c_transport_data);
            kmem_cache_free(rds_conn_slab, conn);
            conn = parent->c_passive;
        } else {
            parent->c_passive = conn;
            rds_cong_add_conn(conn);
            rds_conn_count++;
        }
    } else {
        /* Creating normal conn */
        struct rds_connection *found;

        found = rds_conn_lookup(head, laddr, faddr, trans);
        if (found) {
            trans->conn_free(conn->c_transport_data);
            kmem_cache_free(rds_conn_slab, conn);
            conn = found;
        } else {
            hlist_add_head_rcu(&conn->c_hash_node, head);
            rds_cong_add_conn(conn);
            rds_conn_count++;
        }
    }
    spin_unlock_irqrestore(&rds_conn_lock, flags);

out:
    return conn;
}

struct rds_connection *rds_conn_create(__be32 laddr, __be32 faddr,
                       struct rds_transport *trans, gfp_t gfp)
{
    return __rds_conn_create(laddr, faddr, trans, gfp, 0);
}
EXPORT_SYMBOL_GPL(rds_conn_create);

struct rds_connection *rds_conn_create_outgoing(__be32 laddr, __be32 faddr,
                       struct rds_transport *trans, gfp_t gfp)
{
    return __rds_conn_create(laddr, faddr, trans, gfp, 1);
}
EXPORT_SYMBOL_GPL(rds_conn_create_outgoing);

void rds_conn_shutdown(struct rds_connection *conn)
{
    /* shut it down unless it's down already */
    if (!rds_conn_transition(conn, RDS_CONN_DOWN, RDS_CONN_DOWN)) {
        /*
         * Quiesce the connection mgmt handlers before we start tearing
         * things down. We don't hold the mutex for the entire
         * duration of the shutdown operation, else we may be
         * deadlocking with the CM handler. Instead, the CM event
         * handler is supposed to check for state DISCONNECTING
         */
        mutex_lock(&conn->c_cm_lock);
        if (!rds_conn_transition(conn, RDS_CONN_UP, RDS_CONN_DISCONNECTING)
         && !rds_conn_transition(conn, RDS_CONN_ERROR, RDS_CONN_DISCONNECTING)) {
            rds_conn_error(conn, "shutdown called in state %d\n",
                    atomic_read(&conn->c_state));
            mutex_unlock(&conn->c_cm_lock);
            return;
        }
        mutex_unlock(&conn->c_cm_lock);

        wait_event(conn->c_waitq,
               !test_bit(RDS_IN_XMIT, &conn->c_flags));

        conn->c_trans->conn_shutdown(conn);
        rds_conn_reset(conn);

        if (!rds_conn_transition(conn, RDS_CONN_DISCONNECTING, RDS_CONN_DOWN)) {
            /* This can happen - eg when we're in the middle of tearing
             * down the connection, and someone unloads the rds module.
             * Quite reproduceable with loopback connections.
             * Mostly harmless.
             */
            rds_conn_error(conn,
                "%s: failed to transition to state DOWN, "
                "current state is %d\n",
                __func__,
                atomic_read(&conn->c_state));
            return;
        }
    }

    /* Then reconnect if it's still live.
     * The passive side of an IB loopback connection is never added
     * to the conn hash, so we never trigger a reconnect on this
     * conn - the reconnect is always triggered by the active peer. */
    cancel_delayed_work_sync(&conn->c_conn_w);
    rcu_read_lock();
    if (!hlist_unhashed(&conn->c_hash_node)) {
        rcu_read_unlock();
        rds_queue_reconnect(conn);
    } else {
        rcu_read_unlock();
    }
}

/*
 * Stop and free a connection.
 *
 * This can only be used in very limited circumstances.  It assumes that once
 * the conn has been shutdown that no one else is referencing the connection.
 * We can only ensure this in the rmmod path in the current code.
 */
void rds_conn_destroy(struct rds_connection *conn)
{
    struct rds_message *rm, *rtmp;
    unsigned long flags;

    rdsdebug("freeing conn %p for %pI4 -> "
         "%pI4\n", conn, &conn->c_laddr,
         &conn->c_faddr);

    /* Ensure conn will not be scheduled for reconnect */
    spin_lock_irq(&rds_conn_lock);
    hlist_del_init_rcu(&conn->c_hash_node);
    spin_unlock_irq(&rds_conn_lock);
    synchronize_rcu();

    /* shut the connection down */
    rds_conn_drop(conn);
    flush_work(&conn->c_down_w);

    /* make sure lingering queued work won't try to ref the conn */
    cancel_delayed_work_sync(&conn->c_send_w);
    cancel_delayed_work_sync(&conn->c_recv_w);

    /* tear down queued messages */
    list_for_each_entry_safe(rm, rtmp,
                 &conn->c_send_queue,
                 m_conn_item) {
        list_del_init(&rm->m_conn_item);
        BUG_ON(!list_empty(&rm->m_sock_item));
        rds_message_put(rm);
    }
    if (conn->c_xmit_rm)
        rds_message_put(conn->c_xmit_rm);

    conn->c_trans->conn_free(conn->c_transport_data);

    /*
     * The congestion maps aren't freed up here.  They're
     * freed by rds_cong_exit() after all the connections
     * have been freed.
     */
    rds_cong_remove_conn(conn);

    BUG_ON(!list_empty(&conn->c_retrans));
    kmem_cache_free(rds_conn_slab, conn);

    spin_lock_irqsave(&rds_conn_lock, flags);
    rds_conn_count--;
    spin_unlock_irqrestore(&rds_conn_lock, flags);
}
EXPORT_SYMBOL_GPL(rds_conn_destroy);

static void rds_conn_message_info(struct socket *sock, unsigned int len,
                  struct rds_info_iterator *iter,
                  struct rds_info_lengths *lens,
                  int want_send)
{
    struct hlist_head *head;
    struct hlist_node *pos;
    struct list_head *list;
    struct rds_connection *conn;
    struct rds_message *rm;
    unsigned int total = 0;
    unsigned long flags;
    size_t i;

    len /= sizeof(struct rds_info_message);

    rcu_read_lock();

    for (i = 0, head = rds_conn_hash; i < ARRAY_SIZE(rds_conn_hash);
         i++, head++) {
        hlist_for_each_entry_rcu(conn, pos, head, c_hash_node) {
            if (want_send)
                list = &conn->c_send_queue;
            else
                list = &conn->c_retrans;

            spin_lock_irqsave(&conn->c_lock, flags);

            /* XXX too lazy to maintain counts.. */
            list_for_each_entry(rm, list, m_conn_item) {
                total++;
                if (total <= len)
                    rds_inc_info_copy(&rm->m_inc, iter,
                              conn->c_laddr,
                              conn->c_faddr, 0);
            }

            spin_unlock_irqrestore(&conn->c_lock, flags);
        }
    }
    rcu_read_unlock();

    lens->nr = total;
    lens->each = sizeof(struct rds_info_message);
}

static void rds_conn_message_info_send(struct socket *sock, unsigned int len,
                       struct rds_info_iterator *iter,
                       struct rds_info_lengths *lens)
{
    rds_conn_message_info(sock, len, iter, lens, 1);
}

static void rds_conn_message_info_retrans(struct socket *sock,
                      unsigned int len,
                      struct rds_info_iterator *iter,
                      struct rds_info_lengths *lens)
{
    rds_conn_message_info(sock, len, iter, lens, 0);
}

void rds_for_each_conn_info(struct socket *sock, unsigned int len,
              struct rds_info_iterator *iter,
              struct rds_info_lengths *lens,
              int (*visitor)(struct rds_connection *, void *),
              size_t item_len)
{
    uint64_t buffer[(item_len + 7) / 8];
    struct hlist_head *head;
    struct hlist_node *pos;
    struct rds_connection *conn;
    size_t i;

    rcu_read_lock();

    lens->nr = 0;
    lens->each = item_len;

    for (i = 0, head = rds_conn_hash; i < ARRAY_SIZE(rds_conn_hash);
         i++, head++) {
        hlist_for_each_entry_rcu(conn, pos, head, c_hash_node) {

            /* XXX no c_lock usage.. */
            if (!visitor(conn, buffer))
                continue;

            /* We copy as much as we can fit in the buffer,
             * but we count all items so that the caller
             * can resize the buffer. */
            if (len >= item_len) {
                rds_info_copy(iter, buffer, item_len);
                len -= item_len;
            }
            lens->nr++;
        }
    }
    rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(rds_for_each_conn_info);

static int rds_conn_info_visitor(struct rds_connection *conn,
                  void *buffer)
{
    struct rds_info_connection *cinfo = buffer;

    cinfo->next_tx_seq = conn->c_next_tx_seq;
    cinfo->next_rx_seq = conn->c_next_rx_seq;
    cinfo->laddr = conn->c_laddr;
    cinfo->faddr = conn->c_faddr;
    strncpy(cinfo->transport, conn->c_trans->t_name,
        sizeof(cinfo->transport));
    cinfo->flags = 0;

    rds_conn_info_set(cinfo->flags, test_bit(RDS_IN_XMIT, &conn->c_flags),
              SENDING);
    /* XXX Future: return the state rather than these funky bits */
    rds_conn_info_set(cinfo->flags,
              atomic_read(&conn->c_state) == RDS_CONN_CONNECTING,
              CONNECTING);
    rds_conn_info_set(cinfo->flags,
              atomic_read(&conn->c_state) == RDS_CONN_UP,
              CONNECTED);
    return 1;
}

static void rds_conn_info(struct socket *sock, unsigned int len,
              struct rds_info_iterator *iter,
              struct rds_info_lengths *lens)
{
    rds_for_each_conn_info(sock, len, iter, lens,
                rds_conn_info_visitor,
                sizeof(struct rds_info_connection));
}

int rds_conn_init(void)
{
    rds_conn_slab = kmem_cache_create("rds_connection",
                      sizeof(struct rds_connection),
                      0, 0, NULL);
    if (!rds_conn_slab)
        return -ENOMEM;

    rds_info_register_func(RDS_INFO_CONNECTIONS, rds_conn_info);
    rds_info_register_func(RDS_INFO_SEND_MESSAGES,
                   rds_conn_message_info_send);
    rds_info_register_func(RDS_INFO_RETRANS_MESSAGES,
                   rds_conn_message_info_retrans);

    return 0;
}

void rds_conn_exit(void)
{
    rds_loop_exit();

    WARN_ON(!hlist_empty(rds_conn_hash));

    kmem_cache_destroy(rds_conn_slab);

    rds_info_deregister_func(RDS_INFO_CONNECTIONS, rds_conn_info);
    rds_info_deregister_func(RDS_INFO_SEND_MESSAGES,
                 rds_conn_message_info_send);
    rds_info_deregister_func(RDS_INFO_RETRANS_MESSAGES,
                 rds_conn_message_info_retrans);
}

/*
 * Force a disconnect
 */
void rds_conn_drop(struct rds_connection *conn)
{
    atomic_set(&conn->c_state, RDS_CONN_ERROR);
    queue_work(rds_wq, &conn->c_down_w);
}
EXPORT_SYMBOL_GPL(rds_conn_drop);

/*
 * If the connection is down, trigger a connect. We may have scheduled a
 * delayed reconnect however - in this case we should not interfere.
 */
void rds_conn_connect_if_down(struct rds_connection *conn)
{
    if (rds_conn_state(conn) == RDS_CONN_DOWN &&
        !test_and_set_bit(RDS_RECONNECT_PENDING, &conn->c_flags))
        queue_delayed_work(rds_wq, &conn->c_conn_w, 0);
}
EXPORT_SYMBOL_GPL(rds_conn_connect_if_down);

/*
 * An error occurred on the connection
 */
void
__rds_conn_error(struct rds_connection *conn, const char *fmt, ...)
{
    va_list ap;

    va_start(ap, fmt);
    vprintk(fmt, ap);
    va_end(ap);

    rds_conn_drop(conn);
}