Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

[linux-2.6] / fs / ocfs2 / cluster / tcp.c

/* -*- mode: c; c-basic-offset: 8; -*-
 *
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * Copyright (C) 2004 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 *
 * ----
 *
 * Callers for this were originally written against a very simple synchronus
 * API.  This implementation reflects those simple callers.  Some day I'm sure
 * we'll need to move to a more robust posting/callback mechanism.
 *
 * Transmit calls pass in kernel virtual addresses and block copying this into
 * the socket's tx buffers via a usual blocking sendmsg.  They'll block waiting
 * for a failed socket to timeout.  TX callers can also pass in a poniter to an
 * 'int' which gets filled with an errno off the wire in response to the
 * message they send.
 *
 * Handlers for unsolicited messages are registered.  Each socket has a page
 * that incoming data is copied into.  First the header, then the data.
 * Handlers are called from only one thread with a reference to this per-socket
 * page.  This page is destroyed after the handler call, so it can't be
 * referenced beyond the call.  Handlers may block but are discouraged from
 * doing so.
 *
 * Any framing errors (bad magic, large payload lengths) close a connection.
 *
 * Our sock_container holds the state we associate with a socket.  It's current
 * framing state is held there as well as the refcounting we do around when it
 * is safe to tear down the socket.  The socket is only finally torn down from
 * the container when the container loses all of its references -- so as long
 * as you hold a ref on the container you can trust that the socket is valid
 * for use with kernel socket APIs.
 *
 * Connections are initiated between a pair of nodes when the node with the
 * higher node number gets a heartbeat callback which indicates that the lower
 * numbered node has started heartbeating.  The lower numbered node is passive
 * and only accepts the connection if the higher numbered node is heartbeating.
 */

#include <linux/kernel.h>
#include <linux/jiffies.h>
#include <linux/slab.h>
#include <linux/idr.h>
#include <linux/kref.h>
#include <linux/net.h>
#include <net/tcp.h>

#include <asm/uaccess.h>

#include "heartbeat.h"
#include "tcp.h"
#include "nodemanager.h"
#define MLOG_MASK_PREFIX ML_TCP
#include "masklog.h"
#include "quorum.h"

#include "tcp_internal.h"

#define SC_NODEF_FMT "node %s (num %u) at %u.%u.%u.%u:%u"
#define SC_NODEF_ARGS(sc) sc->sc_node->nd_name, sc->sc_node->nd_num,    \
                          NIPQUAD(sc->sc_node->nd_ipv4_address),        \
                          ntohs(sc->sc_node->nd_ipv4_port)

/*
 * In the following two log macros, the whitespace after the ',' just
 * before ##args is intentional. Otherwise, gcc 2.95 will eat the
 * previous token if args expands to nothing.
 */
#define msglog(hdr, fmt, args...) do {                                  \
        typeof(hdr) __hdr = (hdr);                                      \
        mlog(ML_MSG, "[mag %u len %u typ %u stat %d sys_stat %d "       \
             "key %08x num %u] " fmt,                                   \
             be16_to_cpu(__hdr->magic), be16_to_cpu(__hdr->data_len),   \
             be16_to_cpu(__hdr->msg_type), be32_to_cpu(__hdr->status),  \
             be32_to_cpu(__hdr->sys_status), be32_to_cpu(__hdr->key),   \
             be32_to_cpu(__hdr->msg_num) ,  ##args);                    \
} while (0)

#define sclog(sc, fmt, args...) do {                                    \
        typeof(sc) __sc = (sc);                                         \
        mlog(ML_SOCKET, "[sc %p refs %d sock %p node %u page %p "       \
             "pg_off %zu] " fmt, __sc,                                  \
             atomic_read(&__sc->sc_kref.refcount), __sc->sc_sock,       \
            __sc->sc_node->nd_num, __sc->sc_page, __sc->sc_page_off ,   \
            ##args);                                                    \
} while (0)

static DEFINE_RWLOCK(o2net_handler_lock);
static struct rb_root o2net_handler_tree = RB_ROOT;

static struct o2net_node o2net_nodes[O2NM_MAX_NODES];

/* XXX someday we'll need better accounting */
static struct socket *o2net_listen_sock = NULL;

/*
 * listen work is only queued by the listening socket callbacks on the
 * o2net_wq.  teardown detaches the callbacks before destroying the workqueue.
 * quorum work is queued as sock containers are shutdown.. stop_listening
 * tears down all the node's sock containers, preventing future shutdowns
 * and queued quroum work, before canceling delayed quorum work and
 * destroying the work queue.
 */
static struct workqueue_struct *o2net_wq;
static struct work_struct o2net_listen_work;

static struct o2hb_callback_func o2net_hb_up, o2net_hb_down;
#define O2NET_HB_PRI 0x1

static struct o2net_handshake *o2net_hand;
static struct o2net_msg *o2net_keep_req, *o2net_keep_resp;

static int o2net_sys_err_translations[O2NET_ERR_MAX] =
                {[O2NET_ERR_NONE]       = 0,
                 [O2NET_ERR_NO_HNDLR]   = -ENOPROTOOPT,
                 [O2NET_ERR_OVERFLOW]   = -EOVERFLOW,
                 [O2NET_ERR_DIED]       = -EHOSTDOWN,};

/* can't quite avoid *all* internal declarations :/ */
static void o2net_sc_connect_completed(struct work_struct *work);
static void o2net_rx_until_empty(struct work_struct *work);
static void o2net_shutdown_sc(struct work_struct *work);
static void o2net_listen_data_ready(struct sock *sk, int bytes);
static void o2net_sc_send_keep_req(struct work_struct *work);
static void o2net_idle_timer(unsigned long data);
static void o2net_sc_postpone_idle(struct o2net_sock_container *sc);
static void o2net_sc_reset_idle_timer(struct o2net_sock_container *sc);

#ifdef CONFIG_DEBUG_FS
static void o2net_init_nst(struct o2net_send_tracking *nst, u32 msgtype,
                           u32 msgkey, struct task_struct *task, u8 node)
{
        INIT_LIST_HEAD(&nst->st_net_debug_item);
        nst->st_task = task;
        nst->st_msg_type = msgtype;
        nst->st_msg_key = msgkey;
        nst->st_node = node;
}

static void o2net_set_nst_sock_time(struct o2net_send_tracking *nst)
{
        do_gettimeofday(&nst->st_sock_time);
}

static void o2net_set_nst_send_time(struct o2net_send_tracking *nst)
{
        do_gettimeofday(&nst->st_send_time);
}

static void o2net_set_nst_status_time(struct o2net_send_tracking *nst)
{
        do_gettimeofday(&nst->st_status_time);
}

static void o2net_set_nst_sock_container(struct o2net_send_tracking *nst,
                                         struct o2net_sock_container *sc)
{
        nst->st_sc = sc;
}

static void o2net_set_nst_msg_id(struct o2net_send_tracking *nst, u32 msg_id)
{
        nst->st_id = msg_id;
}

#else  /* CONFIG_DEBUG_FS */

static inline void o2net_init_nst(struct o2net_send_tracking *nst, u32 msgtype,
                                  u32 msgkey, struct task_struct *task, u8 node)
{
}

static inline void o2net_set_nst_sock_time(struct o2net_send_tracking *nst)
{
}

static inline void o2net_set_nst_send_time(struct o2net_send_tracking *nst)
{
}

static inline void o2net_set_nst_status_time(struct o2net_send_tracking *nst)
{
}

static inline void o2net_set_nst_sock_container(struct o2net_send_tracking *nst,
                                                struct o2net_sock_container *sc)
{
}

static inline void o2net_set_nst_msg_id(struct o2net_send_tracking *nst,
                                        u32 msg_id)
{
}

#endif /* CONFIG_DEBUG_FS */

static inline int o2net_reconnect_delay(void)
{
        return o2nm_single_cluster->cl_reconnect_delay_ms;
}

static inline int o2net_keepalive_delay(void)
{
        return o2nm_single_cluster->cl_keepalive_delay_ms;
}

static inline int o2net_idle_timeout(void)
{
        return o2nm_single_cluster->cl_idle_timeout_ms;
}

static inline int o2net_sys_err_to_errno(enum o2net_system_error err)
{
        int trans;
        BUG_ON(err >= O2NET_ERR_MAX);
        trans = o2net_sys_err_translations[err];

        /* Just in case we mess up the translation table above */
        BUG_ON(err != O2NET_ERR_NONE && trans == 0);
        return trans;
}

static struct o2net_node * o2net_nn_from_num(u8 node_num)
{
        BUG_ON(node_num >= ARRAY_SIZE(o2net_nodes));
        return &o2net_nodes[node_num];
}

static u8 o2net_num_from_nn(struct o2net_node *nn)
{
        BUG_ON(nn == NULL);
        return nn - o2net_nodes;
}

/* ------------------------------------------------------------ */

static int o2net_prep_nsw(struct o2net_node *nn, struct o2net_status_wait *nsw)
{
        int ret = 0;

        do {
                if (!idr_pre_get(&nn->nn_status_idr, GFP_ATOMIC)) {
                        ret = -EAGAIN;
                        break;
                }
                spin_lock(&nn->nn_lock);
                ret = idr_get_new(&nn->nn_status_idr, nsw, &nsw->ns_id);
                if (ret == 0)
                        list_add_tail(&nsw->ns_node_item,
                                      &nn->nn_status_list);
                spin_unlock(&nn->nn_lock);
        } while (ret == -EAGAIN);

        if (ret == 0)  {
                init_waitqueue_head(&nsw->ns_wq);
                nsw->ns_sys_status = O2NET_ERR_NONE;
                nsw->ns_status = 0;
        }

        return ret;
}

static void o2net_complete_nsw_locked(struct o2net_node *nn,
                                      struct o2net_status_wait *nsw,
                                      enum o2net_system_error sys_status,
                                      s32 status)
{
        assert_spin_locked(&nn->nn_lock);

        if (!list_empty(&nsw->ns_node_item)) {
                list_del_init(&nsw->ns_node_item);
                nsw->ns_sys_status = sys_status;
                nsw->ns_status = status;
                idr_remove(&nn->nn_status_idr, nsw->ns_id);
                wake_up(&nsw->ns_wq);
        }
}

static void o2net_complete_nsw(struct o2net_node *nn,
                               struct o2net_status_wait *nsw,
                               u64 id, enum o2net_system_error sys_status,
                               s32 status)
{
        spin_lock(&nn->nn_lock);
        if (nsw == NULL) {
                if (id > INT_MAX)
                        goto out;

                nsw = idr_find(&nn->nn_status_idr, id);
                if (nsw == NULL)
                        goto out;
        }

        o2net_complete_nsw_locked(nn, nsw, sys_status, status);

out:
        spin_unlock(&nn->nn_lock);
        return;
}

static void o2net_complete_nodes_nsw(struct o2net_node *nn)
{
        struct o2net_status_wait *nsw, *tmp;
        unsigned int num_kills = 0;

        assert_spin_locked(&nn->nn_lock);

        list_for_each_entry_safe(nsw, tmp, &nn->nn_status_list, ns_node_item) {
                o2net_complete_nsw_locked(nn, nsw, O2NET_ERR_DIED, 0);
                num_kills++;
        }

        mlog(0, "completed %d messages for node %u\n", num_kills,
             o2net_num_from_nn(nn));
}

static int o2net_nsw_completed(struct o2net_node *nn,
                               struct o2net_status_wait *nsw)
{
        int completed;
        spin_lock(&nn->nn_lock);
        completed = list_empty(&nsw->ns_node_item);
        spin_unlock(&nn->nn_lock);
        return completed;
}

/* ------------------------------------------------------------ */

static void sc_kref_release(struct kref *kref)
{
        struct o2net_sock_container *sc = container_of(kref,
                                        struct o2net_sock_container, sc_kref);
        BUG_ON(timer_pending(&sc->sc_idle_timeout));

        sclog(sc, "releasing\n");

        if (sc->sc_sock) {
                sock_release(sc->sc_sock);
                sc->sc_sock = NULL;
        }

        o2nm_node_put(sc->sc_node);
        sc->sc_node = NULL;

        o2net_debug_del_sc(sc);
        kfree(sc);
}

static void sc_put(struct o2net_sock_container *sc)
{
        sclog(sc, "put\n");
        kref_put(&sc->sc_kref, sc_kref_release);
}
static void sc_get(struct o2net_sock_container *sc)
{
        sclog(sc, "get\n");
        kref_get(&sc->sc_kref);
}
static struct o2net_sock_container *sc_alloc(struct o2nm_node *node)
{
        struct o2net_sock_container *sc, *ret = NULL;
        struct page *page = NULL;

        page = alloc_page(GFP_NOFS);
        sc = kzalloc(sizeof(*sc), GFP_NOFS);
        if (sc == NULL || page == NULL)
                goto out;

        kref_init(&sc->sc_kref);
        o2nm_node_get(node);
        sc->sc_node = node;

        INIT_WORK(&sc->sc_connect_work, o2net_sc_connect_completed);
        INIT_WORK(&sc->sc_rx_work, o2net_rx_until_empty);
        INIT_WORK(&sc->sc_shutdown_work, o2net_shutdown_sc);
        INIT_DELAYED_WORK(&sc->sc_keepalive_work, o2net_sc_send_keep_req);

        init_timer(&sc->sc_idle_timeout);
        sc->sc_idle_timeout.function = o2net_idle_timer;
        sc->sc_idle_timeout.data = (unsigned long)sc;

        sclog(sc, "alloced\n");

        ret = sc;
        sc->sc_page = page;
        o2net_debug_add_sc(sc);
        sc = NULL;
        page = NULL;

out:
        if (page)
                __free_page(page);
        kfree(sc);

        return ret;
}

/* ------------------------------------------------------------ */

static void o2net_sc_queue_work(struct o2net_sock_container *sc,
                                struct work_struct *work)
{
        sc_get(sc);
        if (!queue_work(o2net_wq, work))
                sc_put(sc);
}
static void o2net_sc_queue_delayed_work(struct o2net_sock_container *sc,
                                        struct delayed_work *work,
                                        int delay)
{
        sc_get(sc);
        if (!queue_delayed_work(o2net_wq, work, delay))
                sc_put(sc);
}
static void o2net_sc_cancel_delayed_work(struct o2net_sock_container *sc,
                                         struct delayed_work *work)
{
        if (cancel_delayed_work(work))
                sc_put(sc);
}

static atomic_t o2net_connected_peers = ATOMIC_INIT(0);

int o2net_num_connected_peers(void)
{
        return atomic_read(&o2net_connected_peers);
}

static void o2net_set_nn_state(struct o2net_node *nn,
                               struct o2net_sock_container *sc,
                               unsigned valid, int err)
{
        int was_valid = nn->nn_sc_valid;
        int was_err = nn->nn_persistent_error;
        struct o2net_sock_container *old_sc = nn->nn_sc;

        assert_spin_locked(&nn->nn_lock);

        if (old_sc && !sc)
                atomic_dec(&o2net_connected_peers);
        else if (!old_sc && sc)
                atomic_inc(&o2net_connected_peers);

        /* the node num comparison and single connect/accept path should stop
         * an non-null sc from being overwritten with another */
        BUG_ON(sc && nn->nn_sc && nn->nn_sc != sc);
        mlog_bug_on_msg(err && valid, "err %d valid %u\n", err, valid);
        mlog_bug_on_msg(valid && !sc, "valid %u sc %p\n", valid, sc);

        if (was_valid && !valid && err == 0)
                err = -ENOTCONN;

        mlog(ML_CONN, "node %u sc: %p -> %p, valid %u -> %u, err %d -> %d\n",
             o2net_num_from_nn(nn), nn->nn_sc, sc, nn->nn_sc_valid, valid,
             nn->nn_persistent_error, err);

        nn->nn_sc = sc;
        nn->nn_sc_valid = valid ? 1 : 0;
        nn->nn_persistent_error = err;

        /* mirrors o2net_tx_can_proceed() */
        if (nn->nn_persistent_error || nn->nn_sc_valid)
                wake_up(&nn->nn_sc_wq);

        if (!was_err && nn->nn_persistent_error) {
                o2quo_conn_err(o2net_num_from_nn(nn));
                queue_delayed_work(o2net_wq, &nn->nn_still_up,
                                   msecs_to_jiffies(O2NET_QUORUM_DELAY_MS));
        }

        if (was_valid && !valid) {
                printk(KERN_INFO "o2net: no longer connected to "
                       SC_NODEF_FMT "\n", SC_NODEF_ARGS(old_sc));
                o2net_complete_nodes_nsw(nn);
        }

        if (!was_valid && valid) {
                o2quo_conn_up(o2net_num_from_nn(nn));
                cancel_delayed_work(&nn->nn_connect_expired);
                printk(KERN_INFO "o2net: %s " SC_NODEF_FMT "\n",
                       o2nm_this_node() > sc->sc_node->nd_num ?
                                "connected to" : "accepted connection from",
                       SC_NODEF_ARGS(sc));
        }

        /* trigger the connecting worker func as long as we're not valid,
         * it will back off if it shouldn't connect.  This can be called
         * from node config teardown and so needs to be careful about
         * the work queue actually being up. */
        if (!valid && o2net_wq) {
                unsigned long delay;
                /* delay if we're withing a RECONNECT_DELAY of the
                 * last attempt */
                delay = (nn->nn_last_connect_attempt +
                         msecs_to_jiffies(o2net_reconnect_delay()))
                        - jiffies;
                if (delay > msecs_to_jiffies(o2net_reconnect_delay()))
                        delay = 0;
                mlog(ML_CONN, "queueing conn attempt in %lu jiffies\n", delay);
                queue_delayed_work(o2net_wq, &nn->nn_connect_work, delay);

                /*
                 * Delay the expired work after idle timeout.
                 *
                 * We might have lots of failed connection attempts that run
                 * through here but we only cancel the connect_expired work when
                 * a connection attempt succeeds.  So only the first enqueue of
                 * the connect_expired work will do anything.  The rest will see
                 * that it's already queued and do nothing.
                 */
                delay += msecs_to_jiffies(o2net_idle_timeout());
                queue_delayed_work(o2net_wq, &nn->nn_connect_expired, delay);
        }

        /* keep track of the nn's sc ref for the caller */
        if ((old_sc == NULL) && sc)
                sc_get(sc);
        if (old_sc && (old_sc != sc)) {
                o2net_sc_queue_work(old_sc, &old_sc->sc_shutdown_work);
                sc_put(old_sc);
        }
}

/* see o2net_register_callbacks() */
static void o2net_data_ready(struct sock *sk, int bytes)
{
        void (*ready)(struct sock *sk, int bytes);

        read_lock(&sk->sk_callback_lock);
        if (sk->sk_user_data) {
                struct o2net_sock_container *sc = sk->sk_user_data;
                sclog(sc, "data_ready hit\n");
                do_gettimeofday(&sc->sc_tv_data_ready);
                o2net_sc_queue_work(sc, &sc->sc_rx_work);
                ready = sc->sc_data_ready;
        } else {
                ready = sk->sk_data_ready;
        }
        read_unlock(&sk->sk_callback_lock);

        ready(sk, bytes);
}

/* see o2net_register_callbacks() */
static void o2net_state_change(struct sock *sk)
{
        void (*state_change)(struct sock *sk);
        struct o2net_sock_container *sc;

        read_lock(&sk->sk_callback_lock);
        sc = sk->sk_user_data;
        if (sc == NULL) {
                state_change = sk->sk_state_change;
                goto out;
        }

        sclog(sc, "state_change to %d\n", sk->sk_state);

        state_change = sc->sc_state_change;

        switch(sk->sk_state) {
                /* ignore connecting sockets as they make progress */
                case TCP_SYN_SENT:
                case TCP_SYN_RECV:
                        break;
                case TCP_ESTABLISHED:
                        o2net_sc_queue_work(sc, &sc->sc_connect_work);
                        break;
                default:
                        o2net_sc_queue_work(sc, &sc->sc_shutdown_work);
                        break;
        }
out:
        read_unlock(&sk->sk_callback_lock);
        state_change(sk);
}

/*
 * we register callbacks so we can queue work on events before calling
 * the original callbacks.  our callbacks our careful to test user_data
 * to discover when they've reaced with o2net_unregister_callbacks().
 */
static void o2net_register_callbacks(struct sock *sk,
                                     struct o2net_sock_container *sc)
{
        write_lock_bh(&sk->sk_callback_lock);

        /* accepted sockets inherit the old listen socket data ready */
        if (sk->sk_data_ready == o2net_listen_data_ready) {
                sk->sk_data_ready = sk->sk_user_data;
                sk->sk_user_data = NULL;
        }

        BUG_ON(sk->sk_user_data != NULL);
        sk->sk_user_data = sc;
        sc_get(sc);

        sc->sc_data_ready = sk->sk_data_ready;
        sc->sc_state_change = sk->sk_state_change;
        sk->sk_data_ready = o2net_data_ready;
        sk->sk_state_change = o2net_state_change;

        mutex_init(&sc->sc_send_lock);

        write_unlock_bh(&sk->sk_callback_lock);
}

static int o2net_unregister_callbacks(struct sock *sk,
                                   struct o2net_sock_container *sc)
{
        int ret = 0;

        write_lock_bh(&sk->sk_callback_lock);
        if (sk->sk_user_data == sc) {
                ret = 1;
                sk->sk_user_data = NULL;
                sk->sk_data_ready = sc->sc_data_ready;
                sk->sk_state_change = sc->sc_state_change;
        }
        write_unlock_bh(&sk->sk_callback_lock);

        return ret;
}

/*
 * this is a little helper that is called by callers who have seen a problem
 * with an sc and want to detach it from the nn if someone already hasn't beat
 * them to it.  if an error is given then the shutdown will be persistent
 * and pending transmits will be canceled.
 */
static void o2net_ensure_shutdown(struct o2net_node *nn,
                                   struct o2net_sock_container *sc,
                                   int err)
{
        spin_lock(&nn->nn_lock);
        if (nn->nn_sc == sc)
                o2net_set_nn_state(nn, NULL, 0, err);
        spin_unlock(&nn->nn_lock);
}

/*
 * This work queue function performs the blocking parts of socket shutdown.  A
 * few paths lead here.  set_nn_state will trigger this callback if it sees an
 * sc detached from the nn.  state_change will also trigger this callback
 * directly when it sees errors.  In that case we need to call set_nn_state
 * ourselves as state_change couldn't get the nn_lock and call set_nn_state
 * itself.
 */
static void o2net_shutdown_sc(struct work_struct *work)
{
        struct o2net_sock_container *sc =
                container_of(work, struct o2net_sock_container,
                             sc_shutdown_work);
        struct o2net_node *nn = o2net_nn_from_num(sc->sc_node->nd_num);

        sclog(sc, "shutting down\n");

        /* drop the callbacks ref and call shutdown only once */
        if (o2net_unregister_callbacks(sc->sc_sock->sk, sc)) {
                /* we shouldn't flush as we're in the thread, the
                 * races with pending sc work structs are harmless */
                del_timer_sync(&sc->sc_idle_timeout);
                o2net_sc_cancel_delayed_work(sc, &sc->sc_keepalive_work);
                sc_put(sc);
                kernel_sock_shutdown(sc->sc_sock, SHUT_RDWR);
        }

        /* not fatal so failed connects before the other guy has our
         * heartbeat can be retried */
        o2net_ensure_shutdown(nn, sc, 0);
        sc_put(sc);
}

/* ------------------------------------------------------------ */

static int o2net_handler_cmp(struct o2net_msg_handler *nmh, u32 msg_type,
                             u32 key)
{
        int ret = memcmp(&nmh->nh_key, &key, sizeof(key));

        if (ret == 0)
                ret = memcmp(&nmh->nh_msg_type, &msg_type, sizeof(msg_type));

        return ret;
}

static struct o2net_msg_handler *
o2net_handler_tree_lookup(u32 msg_type, u32 key, struct rb_node ***ret_p,
                          struct rb_node **ret_parent)
{
        struct rb_node **p = &o2net_handler_tree.rb_node;
        struct rb_node *parent = NULL;
        struct o2net_msg_handler *nmh, *ret = NULL;
        int cmp;

        while (*p) {
                parent = *p;
                nmh = rb_entry(parent, struct o2net_msg_handler, nh_node);
                cmp = o2net_handler_cmp(nmh, msg_type, key);

                if (cmp < 0)
                        p = &(*p)->rb_left;
                else if (cmp > 0)
                        p = &(*p)->rb_right;
                else {
                        ret = nmh;
                        break;
                }
        }

        if (ret_p != NULL)
                *ret_p = p;
        if (ret_parent != NULL)
                *ret_parent = parent;

        return ret;
}

static void o2net_handler_kref_release(struct kref *kref)
{
        struct o2net_msg_handler *nmh;
        nmh = container_of(kref, struct o2net_msg_handler, nh_kref);

        kfree(nmh);
}

static void o2net_handler_put(struct o2net_msg_handler *nmh)
{
        kref_put(&nmh->nh_kref, o2net_handler_kref_release);
}

/* max_len is protection for the handler func.  incoming messages won't
 * be given to the handler if their payload is longer than the max. */
int o2net_register_handler(u32 msg_type, u32 key, u32 max_len,
                           o2net_msg_handler_func *func, void *data,
                           o2net_post_msg_handler_func *post_func,
                           struct list_head *unreg_list)
{
        struct o2net_msg_handler *nmh = NULL;
        struct rb_node **p, *parent;
        int ret = 0;

        if (max_len > O2NET_MAX_PAYLOAD_BYTES) {
                mlog(0, "max_len for message handler out of range: %u\n",
                        max_len);
                ret = -EINVAL;
                goto out;
        }

        if (!msg_type) {
                mlog(0, "no message type provided: %u, %p\n", msg_type, func);
                ret = -EINVAL;
                goto out;

        }
        if (!func) {
                mlog(0, "no message handler provided: %u, %p\n",
                       msg_type, func);
                ret = -EINVAL;
                goto out;
        }

        nmh = kzalloc(sizeof(struct o2net_msg_handler), GFP_NOFS);
        if (nmh == NULL) {
                ret = -ENOMEM;
                goto out;
        }

        nmh->nh_func = func;
        nmh->nh_func_data = data;
        nmh->nh_post_func = post_func;
        nmh->nh_msg_type = msg_type;
        nmh->nh_max_len = max_len;
        nmh->nh_key = key;
        /* the tree and list get this ref.. they're both removed in
         * unregister when this ref is dropped */
        kref_init(&nmh->nh_kref);
        INIT_LIST_HEAD(&nmh->nh_unregister_item);

        write_lock(&o2net_handler_lock);
        if (o2net_handler_tree_lookup(msg_type, key, &p, &parent))
                ret = -EEXIST;
        else {
                rb_link_node(&nmh->nh_node, parent, p);
                rb_insert_color(&nmh->nh_node, &o2net_handler_tree);
                list_add_tail(&nmh->nh_unregister_item, unreg_list);

                mlog(ML_TCP, "registered handler func %p type %u key %08x\n",
                     func, msg_type, key);
                /* we've had some trouble with handlers seemingly vanishing. */
                mlog_bug_on_msg(o2net_handler_tree_lookup(msg_type, key, &p,
                                                          &parent) == NULL,
                                "couldn't find handler we *just* registerd "
                                "for type %u key %08x\n", msg_type, key);
        }
        write_unlock(&o2net_handler_lock);
        if (ret)
                goto out;

out:
        if (ret)
                kfree(nmh);

        return ret;
}
EXPORT_SYMBOL_GPL(o2net_register_handler);

void o2net_unregister_handler_list(struct list_head *list)
{
        struct o2net_msg_handler *nmh, *n;

        write_lock(&o2net_handler_lock);
        list_for_each_entry_safe(nmh, n, list, nh_unregister_item) {
                mlog(ML_TCP, "unregistering handler func %p type %u key %08x\n",
                     nmh->nh_func, nmh->nh_msg_type, nmh->nh_key);
                rb_erase(&nmh->nh_node, &o2net_handler_tree);
                list_del_init(&nmh->nh_unregister_item);
                kref_put(&nmh->nh_kref, o2net_handler_kref_release);
        }
        write_unlock(&o2net_handler_lock);
}
EXPORT_SYMBOL_GPL(o2net_unregister_handler_list);

static struct o2net_msg_handler *o2net_handler_get(u32 msg_type, u32 key)
{
        struct o2net_msg_handler *nmh;

        read_lock(&o2net_handler_lock);
        nmh = o2net_handler_tree_lookup(msg_type, key, NULL, NULL);
        if (nmh)
                kref_get(&nmh->nh_kref);
        read_unlock(&o2net_handler_lock);

        return nmh;
}

/* ------------------------------------------------------------ */

static int o2net_recv_tcp_msg(struct socket *sock, void *data, size_t len)
{
        int ret;
        mm_segment_t oldfs;
        struct kvec vec = {
                .iov_len = len,
                .iov_base = data,
        };
        struct msghdr msg = {
                .msg_iovlen = 1,
                .msg_iov = (struct iovec *)&vec,
                .msg_flags = MSG_DONTWAIT,
        };

        oldfs = get_fs();
        set_fs(get_ds());
        ret = sock_recvmsg(sock, &msg, len, msg.msg_flags);
        set_fs(oldfs);

        return ret;
}

static int o2net_send_tcp_msg(struct socket *sock, struct kvec *vec,
                              size_t veclen, size_t total)
{
        int ret;
        mm_segment_t oldfs;
        struct msghdr msg = {
                .msg_iov = (struct iovec *)vec,
                .msg_iovlen = veclen,
        };

        if (sock == NULL) {
                ret = -EINVAL;
                goto out;
        }

        oldfs = get_fs();
        set_fs(get_ds());
        ret = sock_sendmsg(sock, &msg, total);
        set_fs(oldfs);
        if (ret != total) {
                mlog(ML_ERROR, "sendmsg returned %d instead of %zu\n", ret,
                     total);
                if (ret >= 0)
                        ret = -EPIPE; /* should be smarter, I bet */
                goto out;
        }

        ret = 0;
out:
        if (ret < 0)
                mlog(0, "returning error: %d\n", ret);
        return ret;
}

static void o2net_sendpage(struct o2net_sock_container *sc,
                           void *kmalloced_virt,
                           size_t size)
{
        struct o2net_node *nn = o2net_nn_from_num(sc->sc_node->nd_num);
        ssize_t ret;

        while (1) {
                mutex_lock(&sc->sc_send_lock);
                ret = sc->sc_sock->ops->sendpage(sc->sc_sock,
                                                 virt_to_page(kmalloced_virt),
                                                 (long)kmalloced_virt & ~PAGE_MASK,
                                                 size, MSG_DONTWAIT);
                mutex_unlock(&sc->sc_send_lock);
                if (ret == size)
                        break;
                if (ret == (ssize_t)-EAGAIN) {
                        mlog(0, "sendpage of size %zu to " SC_NODEF_FMT
                             " returned EAGAIN\n", size, SC_NODEF_ARGS(sc));
                        cond_resched();
                        continue;
                }
                mlog(ML_ERROR, "sendpage of size %zu to " SC_NODEF_FMT 
                     " failed with %zd\n", size, SC_NODEF_ARGS(sc), ret);
                o2net_ensure_shutdown(nn, sc, 0);
                break;
        }
}

static void o2net_init_msg(struct o2net_msg *msg, u16 data_len, u16 msg_type, u32 key)
{
        memset(msg, 0, sizeof(struct o2net_msg));
        msg->magic = cpu_to_be16(O2NET_MSG_MAGIC);
        msg->data_len = cpu_to_be16(data_len);
        msg->msg_type = cpu_to_be16(msg_type);
        msg->sys_status = cpu_to_be32(O2NET_ERR_NONE);
        msg->status = 0;
        msg->key = cpu_to_be32(key);
}

static int o2net_tx_can_proceed(struct o2net_node *nn,
                                struct o2net_sock_container **sc_ret,
                                int *error)
{
        int ret = 0;

        spin_lock(&nn->nn_lock);
        if (nn->nn_persistent_error) {
                ret = 1;
                *sc_ret = NULL;
                *error = nn->nn_persistent_error;
        } else if (nn->nn_sc_valid) {
                kref_get(&nn->nn_sc->sc_kref);

                ret = 1;
                *sc_ret = nn->nn_sc;
                *error = 0;
        }
        spin_unlock(&nn->nn_lock);

        return ret;
}

int o2net_send_message_vec(u32 msg_type, u32 key, struct kvec *caller_vec,
                           size_t caller_veclen, u8 target_node, int *status)
{
        int ret;
        struct o2net_msg *msg = NULL;
        size_t veclen, caller_bytes = 0;
        struct kvec *vec = NULL;
        struct o2net_sock_container *sc = NULL;
        struct o2net_node *nn = o2net_nn_from_num(target_node);
        struct o2net_status_wait nsw = {
                .ns_node_item = LIST_HEAD_INIT(nsw.ns_node_item),
        };
        struct o2net_send_tracking nst;

        o2net_init_nst(&nst, msg_type, key, current, target_node);

        if (o2net_wq == NULL) {
                mlog(0, "attempt to tx without o2netd running\n");
                ret = -ESRCH;
                goto out;
        }

        if (caller_veclen == 0) {
                mlog(0, "bad kvec array length\n");
                ret = -EINVAL;
                goto out;
        }

        caller_bytes = iov_length((struct iovec *)caller_vec, caller_veclen);
        if (caller_bytes > O2NET_MAX_PAYLOAD_BYTES) {
                mlog(0, "total payload len %zu too large\n", caller_bytes);
                ret = -EINVAL;
                goto out;
        }

        if (target_node == o2nm_this_node()) {
                ret = -ELOOP;
                goto out;
        }

        o2net_debug_add_nst(&nst);

        o2net_set_nst_sock_time(&nst);

        wait_event(nn->nn_sc_wq, o2net_tx_can_proceed(nn, &sc, &ret));
        if (ret)
                goto out;

        o2net_set_nst_sock_container(&nst, sc);

        veclen = caller_veclen + 1;
        vec = kmalloc(sizeof(struct kvec) * veclen, GFP_ATOMIC);
        if (vec == NULL) {
                mlog(0, "failed to %zu element kvec!\n", veclen);
                ret = -ENOMEM;
                goto out;
        }

        msg = kmalloc(sizeof(struct o2net_msg), GFP_ATOMIC);
        if (!msg) {
                mlog(0, "failed to allocate a o2net_msg!\n");
                ret = -ENOMEM;
                goto out;
        }

        o2net_init_msg(msg, caller_bytes, msg_type, key);

        vec[0].iov_len = sizeof(struct o2net_msg);
        vec[0].iov_base = msg;
        memcpy(&vec[1], caller_vec, caller_veclen * sizeof(struct kvec));

        ret = o2net_prep_nsw(nn, &nsw);
        if (ret)
                goto out;

        msg->msg_num = cpu_to_be32(nsw.ns_id);
        o2net_set_nst_msg_id(&nst, nsw.ns_id);

        o2net_set_nst_send_time(&nst);

        /* finally, convert the message header to network byte-order
         * and send */
        mutex_lock(&sc->sc_send_lock);
        ret = o2net_send_tcp_msg(sc->sc_sock, vec, veclen,
                                 sizeof(struct o2net_msg) + caller_bytes);
        mutex_unlock(&sc->sc_send_lock);
        msglog(msg, "sending returned %d\n", ret);
        if (ret < 0) {
                mlog(0, "error returned from o2net_send_tcp_msg=%d\n", ret);
                goto out;
        }

        /* wait on other node's handler */
        o2net_set_nst_status_time(&nst);
        wait_event(nsw.ns_wq, o2net_nsw_completed(nn, &nsw));

        /* Note that we avoid overwriting the callers status return
         * variable if a system error was reported on the other
         * side. Callers beware. */
        ret = o2net_sys_err_to_errno(nsw.ns_sys_status);
        if (status && !ret)
                *status = nsw.ns_status;

        mlog(0, "woken, returning system status %d, user status %d\n",
             ret, nsw.ns_status);
out:
        o2net_debug_del_nst(&nst); /* must be before dropping sc and node */
        if (sc)
                sc_put(sc);
        if (vec)
                kfree(vec);
        if (msg)
                kfree(msg);
        o2net_complete_nsw(nn, &nsw, 0, 0, 0);
        return ret;
}
EXPORT_SYMBOL_GPL(o2net_send_message_vec);

int o2net_send_message(u32 msg_type, u32 key, void *data, u32 len,
                       u8 target_node, int *status)
{
        struct kvec vec = {
                .iov_base = data,
                .iov_len = len,
        };
        return o2net_send_message_vec(msg_type, key, &vec, 1,
                                      target_node, status);
}
EXPORT_SYMBOL_GPL(o2net_send_message);

static int o2net_send_status_magic(struct socket *sock, struct o2net_msg *hdr,
                                   enum o2net_system_error syserr, int err)
{
        struct kvec vec = {
                .iov_base = hdr,
                .iov_len = sizeof(struct o2net_msg),
        };

        BUG_ON(syserr >= O2NET_ERR_MAX);

        /* leave other fields intact from the incoming message, msg_num
         * in particular */
        hdr->sys_status = cpu_to_be32(syserr);
        hdr->status = cpu_to_be32(err);
        hdr->magic = cpu_to_be16(O2NET_MSG_STATUS_MAGIC);  // twiddle the magic
        hdr->data_len = 0;

        msglog(hdr, "about to send status magic %d\n", err);
        /* hdr has been in host byteorder this whole time */
        return o2net_send_tcp_msg(sock, &vec, 1, sizeof(struct o2net_msg));
}

/* this returns -errno if the header was unknown or too large, etc.
 * after this is called the buffer us reused for the next message */
static int o2net_process_message(struct o2net_sock_container *sc,
                                 struct o2net_msg *hdr)
{
        struct o2net_node *nn = o2net_nn_from_num(sc->sc_node->nd_num);
        int ret = 0, handler_status;
        enum  o2net_system_error syserr;
        struct o2net_msg_handler *nmh = NULL;
        void *ret_data = NULL;

        msglog(hdr, "processing message\n");

        o2net_sc_postpone_idle(sc);

        switch(be16_to_cpu(hdr->magic)) {
                case O2NET_MSG_STATUS_MAGIC:
                        /* special type for returning message status */
                        o2net_complete_nsw(nn, NULL,
                                           be32_to_cpu(hdr->msg_num),
                                           be32_to_cpu(hdr->sys_status),
                                           be32_to_cpu(hdr->status));
                        goto out;
                case O2NET_MSG_KEEP_REQ_MAGIC:
                        o2net_sendpage(sc, o2net_keep_resp,
                                       sizeof(*o2net_keep_resp));
                        goto out;
                case O2NET_MSG_KEEP_RESP_MAGIC:
                        goto out;
                case O2NET_MSG_MAGIC:
                        break;
                default:
                        msglog(hdr, "bad magic\n");
                        ret = -EINVAL;
                        goto out;
                        break;
        }

        /* find a handler for it */
        handler_status = 0;
        nmh = o2net_handler_get(be16_to_cpu(hdr->msg_type),
                                be32_to_cpu(hdr->key));
        if (!nmh) {
                mlog(ML_TCP, "couldn't find handler for type %u key %08x\n",
                     be16_to_cpu(hdr->msg_type), be32_to_cpu(hdr->key));
                syserr = O2NET_ERR_NO_HNDLR;
                goto out_respond;
        }

        syserr = O2NET_ERR_NONE;

        if (be16_to_cpu(hdr->data_len) > nmh->nh_max_len)
                syserr = O2NET_ERR_OVERFLOW;

        if (syserr != O2NET_ERR_NONE)
                goto out_respond;

        do_gettimeofday(&sc->sc_tv_func_start);
        sc->sc_msg_key = be32_to_cpu(hdr->key);
        sc->sc_msg_type = be16_to_cpu(hdr->msg_type);
        handler_status = (nmh->nh_func)(hdr, sizeof(struct o2net_msg) +
                                             be16_to_cpu(hdr->data_len),
                                        nmh->nh_func_data, &ret_data);
        do_gettimeofday(&sc->sc_tv_func_stop);

out_respond:
        /* this destroys the hdr, so don't use it after this */
        mutex_lock(&sc->sc_send_lock);
        ret = o2net_send_status_magic(sc->sc_sock, hdr, syserr,
                                      handler_status);
        mutex_unlock(&sc->sc_send_lock);
        hdr = NULL;
        mlog(0, "sending handler status %d, syserr %d returned %d\n",
             handler_status, syserr, ret);

        if (nmh) {
                BUG_ON(ret_data != NULL && nmh->nh_post_func == NULL);
                if (nmh->nh_post_func)
                        (nmh->nh_post_func)(handler_status, nmh->nh_func_data,
                                            ret_data);
        }

out:
        if (nmh)
                o2net_handler_put(nmh);
        return ret;
}

static int o2net_check_handshake(struct o2net_sock_container *sc)
{
        struct o2net_handshake *hand = page_address(sc->sc_page);
        struct o2net_node *nn = o2net_nn_from_num(sc->sc_node->nd_num);

        if (hand->protocol_version != cpu_to_be64(O2NET_PROTOCOL_VERSION)) {
                mlog(ML_NOTICE, SC_NODEF_FMT " advertised net protocol "
                     "version %llu but %llu is required, disconnecting\n",
                     SC_NODEF_ARGS(sc),
                     (unsigned long long)be64_to_cpu(hand->protocol_version),
                     O2NET_PROTOCOL_VERSION);

                /* don't bother reconnecting if its the wrong version. */
                o2net_ensure_shutdown(nn, sc, -ENOTCONN);
                return -1;
        }

        /*
         * Ensure timeouts are consistent with other nodes, otherwise
         * we can end up with one node thinking that the other must be down,
         * but isn't. This can ultimately cause corruption.
         */
        if (be32_to_cpu(hand->o2net_idle_timeout_ms) !=
                                o2net_idle_timeout()) {
                mlog(ML_NOTICE, SC_NODEF_FMT " uses a network idle timeout of "
                     "%u ms, but we use %u ms locally.  disconnecting\n",
                     SC_NODEF_ARGS(sc),
                     be32_to_cpu(hand->o2net_idle_timeout_ms),
                     o2net_idle_timeout());
                o2net_ensure_shutdown(nn, sc, -ENOTCONN);
                return -1;
        }

        if (be32_to_cpu(hand->o2net_keepalive_delay_ms) !=
                        o2net_keepalive_delay()) {
                mlog(ML_NOTICE, SC_NODEF_FMT " uses a keepalive delay of "
                     "%u ms, but we use %u ms locally.  disconnecting\n",
                     SC_NODEF_ARGS(sc),
                     be32_to_cpu(hand->o2net_keepalive_delay_ms),
                     o2net_keepalive_delay());
                o2net_ensure_shutdown(nn, sc, -ENOTCONN);
                return -1;
        }

        if (be32_to_cpu(hand->o2hb_heartbeat_timeout_ms) !=
                        O2HB_MAX_WRITE_TIMEOUT_MS) {
                mlog(ML_NOTICE, SC_NODEF_FMT " uses a heartbeat timeout of "
                     "%u ms, but we use %u ms locally.  disconnecting\n",
                     SC_NODEF_ARGS(sc),
                     be32_to_cpu(hand->o2hb_heartbeat_timeout_ms),
                     O2HB_MAX_WRITE_TIMEOUT_MS);
                o2net_ensure_shutdown(nn, sc, -ENOTCONN);
                return -1;
        }

        sc->sc_handshake_ok = 1;

        spin_lock(&nn->nn_lock);
        /* set valid and queue the idle timers only if it hasn't been
         * shut down already */
        if (nn->nn_sc == sc) {
                o2net_sc_reset_idle_timer(sc);
                atomic_set(&nn->nn_timeout, 0);
                o2net_set_nn_state(nn, sc, 1, 0);
        }
        spin_unlock(&nn->nn_lock);

        /* shift everything up as though it wasn't there */
        sc->sc_page_off -= sizeof(struct o2net_handshake);
        if (sc->sc_page_off)
                memmove(hand, hand + 1, sc->sc_page_off);

        return 0;
}

/* this demuxes the queued rx bytes into header or payload bits and calls
 * handlers as each full message is read off the socket.  it returns -error,
 * == 0 eof, or > 0 for progress made.*/
static int o2net_advance_rx(struct o2net_sock_container *sc)
{
        struct o2net_msg *hdr;
        int ret = 0;
        void *data;
        size_t datalen;

        sclog(sc, "receiving\n");
        do_gettimeofday(&sc->sc_tv_advance_start);

        if (unlikely(sc->sc_handshake_ok == 0)) {
                if(sc->sc_page_off < sizeof(struct o2net_handshake)) {
                        data = page_address(sc->sc_page) + sc->sc_page_off;
                        datalen = sizeof(struct o2net_handshake) - sc->sc_page_off;
                        ret = o2net_recv_tcp_msg(sc->sc_sock, data, datalen);
                        if (ret > 0)
                                sc->sc_page_off += ret;
                }

                if (sc->sc_page_off == sizeof(struct o2net_handshake)) {
                        o2net_check_handshake(sc);
                        if (unlikely(sc->sc_handshake_ok == 0))
                                ret = -EPROTO;
                }
                goto out;
        }

        /* do we need more header? */
        if (sc->sc_page_off < sizeof(struct o2net_msg)) {
                data = page_address(sc->sc_page) + sc->sc_page_off;
                datalen = sizeof(struct o2net_msg) - sc->sc_page_off;
                ret = o2net_recv_tcp_msg(sc->sc_sock, data, datalen);
                if (ret > 0) {
                        sc->sc_page_off += ret;
                        /* only swab incoming here.. we can
                         * only get here once as we cross from
                         * being under to over */
                        if (sc->sc_page_off == sizeof(struct o2net_msg)) {
                                hdr = page_address(sc->sc_page);
                                if (be16_to_cpu(hdr->data_len) >
                                    O2NET_MAX_PAYLOAD_BYTES)
                                        ret = -EOVERFLOW;
                        }
                }
                if (ret <= 0)
                        goto out;
        }

        if (sc->sc_page_off < sizeof(struct o2net_msg)) {
                /* oof, still don't have a header */
                goto out;
        }

        /* this was swabbed above when we first read it */
        hdr = page_address(sc->sc_page);

        msglog(hdr, "at page_off %zu\n", sc->sc_page_off);

        /* do we need more payload? */
        if (sc->sc_page_off - sizeof(struct o2net_msg) < be16_to_cpu(hdr->data_len)) {
                /* need more payload */
                data = page_address(sc->sc_page) + sc->sc_page_off;
                datalen = (sizeof(struct o2net_msg) + be16_to_cpu(hdr->data_len)) -
                          sc->sc_page_off;
                ret = o2net_recv_tcp_msg(sc->sc_sock, data, datalen);
                if (ret > 0)
                        sc->sc_page_off += ret;
                if (ret <= 0)
                        goto out;
        }

        if (sc->sc_page_off - sizeof(struct o2net_msg) == be16_to_cpu(hdr->data_len)) {
                /* we can only get here once, the first time we read
                 * the payload.. so set ret to progress if the handler
                 * works out. after calling this the message is toast */
                ret = o2net_process_message(sc, hdr);
                if (ret == 0)
                        ret = 1;
                sc->sc_page_off = 0;
        }

out:
        sclog(sc, "ret = %d\n", ret);
        do_gettimeofday(&sc->sc_tv_advance_stop);
        return ret;
}

/* this work func is triggerd by data ready.  it reads until it can read no
 * more.  it interprets 0, eof, as fatal.  if data_ready hits while we're doing
 * our work the work struct will be marked and we'll be called again. */
static void o2net_rx_until_empty(struct work_struct *work)
{
        struct o2net_sock_container *sc =
                container_of(work, struct o2net_sock_container, sc_rx_work);
        int ret;

        do {
                ret = o2net_advance_rx(sc);
        } while (ret > 0);

        if (ret <= 0 && ret != -EAGAIN) {
                struct o2net_node *nn = o2net_nn_from_num(sc->sc_node->nd_num);
                sclog(sc, "saw error %d, closing\n", ret);
                /* not permanent so read failed handshake can retry */
                o2net_ensure_shutdown(nn, sc, 0);
        }

        sc_put(sc);
}

static int o2net_set_nodelay(struct socket *sock)
{
        int ret, val = 1;
        mm_segment_t oldfs;

        oldfs = get_fs();
        set_fs(KERNEL_DS);

        /*
         * Dear unsuspecting programmer,
         *
         * Don't use sock_setsockopt() for SOL_TCP.  It doesn't check its level
         * argument and assumes SOL_SOCKET so, say, your TCP_NODELAY will
         * silently turn into SO_DEBUG.
         *
         * Yours,
         * Keeper of hilariously fragile interfaces.
         */
        ret = sock->ops->setsockopt(sock, SOL_TCP, TCP_NODELAY,
                                    (char __user *)&val, sizeof(val));

        set_fs(oldfs);
        return ret;
}

static void o2net_initialize_handshake(void)
{
        o2net_hand->o2hb_heartbeat_timeout_ms = cpu_to_be32(
                O2HB_MAX_WRITE_TIMEOUT_MS);
        o2net_hand->o2net_idle_timeout_ms = cpu_to_be32(o2net_idle_timeout());
        o2net_hand->o2net_keepalive_delay_ms = cpu_to_be32(
                o2net_keepalive_delay());
        o2net_hand->o2net_reconnect_delay_ms = cpu_to_be32(
                o2net_reconnect_delay());
}

/* ------------------------------------------------------------ */

/* called when a connect completes and after a sock is accepted.  the
 * rx path will see the response and mark the sc valid */
static void o2net_sc_connect_completed(struct work_struct *work)
{
        struct o2net_sock_container *sc =
                container_of(work, struct o2net_sock_container,
                             sc_connect_work);

        mlog(ML_MSG, "sc sending handshake with ver %llu id %llx\n",
              (unsigned long long)O2NET_PROTOCOL_VERSION,
              (unsigned long long)be64_to_cpu(o2net_hand->connector_id));

        o2net_initialize_handshake();
        o2net_sendpage(sc, o2net_hand, sizeof(*o2net_hand));
        sc_put(sc);
}

/* this is called as a work_struct func. */
static void o2net_sc_send_keep_req(struct work_struct *work)
{
        struct o2net_sock_container *sc =
                container_of(work, struct o2net_sock_container,
                             sc_keepalive_work.work);

        o2net_sendpage(sc, o2net_keep_req, sizeof(*o2net_keep_req));
        sc_put(sc);
}

/* socket shutdown does a del_timer_sync against this as it tears down.
 * we can't start this timer until we've got to the point in sc buildup
 * where shutdown is going to be involved */
static void o2net_idle_timer(unsigned long data)
{
        struct o2net_sock_container *sc = (struct o2net_sock_container *)data;
        struct o2net_node *nn = o2net_nn_from_num(sc->sc_node->nd_num);
        struct timeval now;

        do_gettimeofday(&now);

        printk(KERN_INFO "o2net: connection to " SC_NODEF_FMT " has been idle for %u.%u "
             "seconds, shutting it down.\n", SC_NODEF_ARGS(sc),
                     o2net_idle_timeout() / 1000,
                     o2net_idle_timeout() % 1000);
        mlog(ML_NOTICE, "here are some times that might help debug the "
             "situation: (tmr %ld.%ld now %ld.%ld dr %ld.%ld adv "
             "%ld.%ld:%ld.%ld func (%08x:%u) %ld.%ld:%ld.%ld)\n",
             sc->sc_tv_timer.tv_sec, (long) sc->sc_tv_timer.tv_usec, 
             now.tv_sec, (long) now.tv_usec,
             sc->sc_tv_data_ready.tv_sec, (long) sc->sc_tv_data_ready.tv_usec,
             sc->sc_tv_advance_start.tv_sec,
             (long) sc->sc_tv_advance_start.tv_usec,
             sc->sc_tv_advance_stop.tv_sec,
             (long) sc->sc_tv_advance_stop.tv_usec,
             sc->sc_msg_key, sc->sc_msg_type,
             sc->sc_tv_func_start.tv_sec, (long) sc->sc_tv_func_start.tv_usec,
             sc->sc_tv_func_stop.tv_sec, (long) sc->sc_tv_func_stop.tv_usec);

        /*
         * Initialize the nn_timeout so that the next connection attempt
         * will continue in o2net_start_connect.
         */
        atomic_set(&nn->nn_timeout, 1);

        o2net_sc_queue_work(sc, &sc->sc_shutdown_work);
}

static void o2net_sc_reset_idle_timer(struct o2net_sock_container *sc)
{
        o2net_sc_cancel_delayed_work(sc, &sc->sc_keepalive_work);
        o2net_sc_queue_delayed_work(sc, &sc->sc_keepalive_work,
                      msecs_to_jiffies(o2net_keepalive_delay()));
        do_gettimeofday(&sc->sc_tv_timer);
        mod_timer(&sc->sc_idle_timeout,
               jiffies + msecs_to_jiffies(o2net_idle_timeout()));
}

static void o2net_sc_postpone_idle(struct o2net_sock_container *sc)
{
        /* Only push out an existing timer */
        if (timer_pending(&sc->sc_idle_timeout))
                o2net_sc_reset_idle_timer(sc);
}

/* this work func is kicked whenever a path sets the nn state which doesn't
 * have valid set.  This includes seeing hb come up, losing a connection,
 * having a connect attempt fail, etc. This centralizes the logic which decides
 * if a connect attempt should be made or if we should give up and all future
 * transmit attempts should fail */
static void o2net_start_connect(struct work_struct *work)
{
        struct o2net_node *nn =
                container_of(work, struct o2net_node, nn_connect_work.work);
        struct o2net_sock_container *sc = NULL;
        struct o2nm_node *node = NULL, *mynode = NULL;
        struct socket *sock = NULL;
        struct sockaddr_in myaddr = {0, }, remoteaddr = {0, };
        int ret = 0, stop;
        unsigned int timeout;

        /* if we're greater we initiate tx, otherwise we accept */
        if (o2nm_this_node() <= o2net_num_from_nn(nn))
                goto out;

        /* watch for racing with tearing a node down */
        node = o2nm_get_node_by_num(o2net_num_from_nn(nn));
        if (node == NULL) {
                ret = 0;
                goto out;
        }

        mynode = o2nm_get_node_by_num(o2nm_this_node());
        if (mynode == NULL) {
                ret = 0;
                goto out;
        }

        spin_lock(&nn->nn_lock);
        /*
         * see if we already have one pending or have given up.
         * For nn_timeout, it is set when we close the connection
         * because of the idle time out. So it means that we have
         * at least connected to that node successfully once,
         * now try to connect to it again.
         */
        timeout = atomic_read(&nn->nn_timeout);
        stop = (nn->nn_sc ||
                (nn->nn_persistent_error &&
                (nn->nn_persistent_error != -ENOTCONN || timeout == 0)));
        spin_unlock(&nn->nn_lock);
        if (stop)
                goto out;

        nn->nn_last_connect_attempt = jiffies;

        sc = sc_alloc(node);
        if (sc == NULL) {
                mlog(0, "couldn't allocate sc\n");
                ret = -ENOMEM;
                goto out;
        }

        ret = sock_create(PF_INET, SOCK_STREAM, IPPROTO_TCP, &sock);
        if (ret < 0) {
                mlog(0, "can't create socket: %d\n", ret);
                goto out;
        }
        sc->sc_sock = sock; /* freed by sc_kref_release */

        sock->sk->sk_allocation = GFP_ATOMIC;

        myaddr.sin_family = AF_INET;
        myaddr.sin_addr.s_addr = mynode->nd_ipv4_address;
        myaddr.sin_port = htons(0); /* any port */

        ret = sock->ops->bind(sock, (struct sockaddr *)&myaddr,
                              sizeof(myaddr));
        if (ret) {
                mlog(ML_ERROR, "bind failed with %d at address %pI4\n",
                     ret, &mynode->nd_ipv4_address);
                goto out;
        }

        ret = o2net_set_nodelay(sc->sc_sock);
        if (ret) {
                mlog(ML_ERROR, "setting TCP_NODELAY failed with %d\n", ret);
                goto out;
        }

        o2net_register_callbacks(sc->sc_sock->sk, sc);

        spin_lock(&nn->nn_lock);
        /* handshake completion will set nn->nn_sc_valid */
        o2net_set_nn_state(nn, sc, 0, 0);
        spin_unlock(&nn->nn_lock);

        remoteaddr.sin_family = AF_INET;
        remoteaddr.sin_addr.s_addr = node->nd_ipv4_address;
        remoteaddr.sin_port = node->nd_ipv4_port;

        ret = sc->sc_sock->ops->connect(sc->sc_sock,
                                        (struct sockaddr *)&remoteaddr,
                                        sizeof(remoteaddr),
                                        O_NONBLOCK);
        if (ret == -EINPROGRESS)
                ret = 0;

out:
        if (ret) {
                mlog(ML_NOTICE, "connect attempt to " SC_NODEF_FMT " failed "
                     "with errno %d\n", SC_NODEF_ARGS(sc), ret);
                /* 0 err so that another will be queued and attempted
                 * from set_nn_state */
                if (sc)
                        o2net_ensure_shutdown(nn, sc, 0);
        }
        if (sc)
                sc_put(sc);
        if (node)
                o2nm_node_put(node);
        if (mynode)
                o2nm_node_put(mynode);

        return;
}

static void o2net_connect_expired(struct work_struct *work)
{
        struct o2net_node *nn =
                container_of(work, struct o2net_node, nn_connect_expired.work);

        spin_lock(&nn->nn_lock);
        if (!nn->nn_sc_valid) {
                mlog(ML_ERROR, "no connection established with node %u after "
                     "%u.%u seconds, giving up and returning errors.\n",
                     o2net_num_from_nn(nn),
                     o2net_idle_timeout() / 1000,
                     o2net_idle_timeout() % 1000);

                o2net_set_nn_state(nn, NULL, 0, -ENOTCONN);
        }
        spin_unlock(&nn->nn_lock);
}

static void o2net_still_up(struct work_struct *work)
{
        struct o2net_node *nn =
                container_of(work, struct o2net_node, nn_still_up.work);

        o2quo_hb_still_up(o2net_num_from_nn(nn));
}

/* ------------------------------------------------------------ */

void o2net_disconnect_node(struct o2nm_node *node)
{
        struct o2net_node *nn = o2net_nn_from_num(node->nd_num);

        /* don't reconnect until it's heartbeating again */
        spin_lock(&nn->nn_lock);
        atomic_set(&nn->nn_timeout, 0);
        o2net_set_nn_state(nn, NULL, 0, -ENOTCONN);
        spin_unlock(&nn->nn_lock);

        if (o2net_wq) {
                cancel_delayed_work(&nn->nn_connect_expired);
                cancel_delayed_work(&nn->nn_connect_work);
                cancel_delayed_work(&nn->nn_still_up);
                flush_workqueue(o2net_wq);
        }
}

static void o2net_hb_node_down_cb(struct o2nm_node *node, int node_num,
                                  void *data)
{
        o2quo_hb_down(node_num);

        if (node_num != o2nm_this_node())
                o2net_disconnect_node(node);

        BUG_ON(atomic_read(&o2net_connected_peers) < 0);
}

static void o2net_hb_node_up_cb(struct o2nm_node *node, int node_num,
                                void *data)
{
        struct o2net_node *nn = o2net_nn_from_num(node_num);

        o2quo_hb_up(node_num);

        /* ensure an immediate connect attempt */
        nn->nn_last_connect_attempt = jiffies -
                (msecs_to_jiffies(o2net_reconnect_delay()) + 1);

        if (node_num != o2nm_this_node()) {
                /* believe it or not, accept and node hearbeating testing
                 * can succeed for this node before we got here.. so
                 * only use set_nn_state to clear the persistent error
                 * if that hasn't already happened */
                spin_lock(&nn->nn_lock);
                atomic_set(&nn->nn_timeout, 0);
                if (nn->nn_persistent_error)
                        o2net_set_nn_state(nn, NULL, 0, 0);
                spin_unlock(&nn->nn_lock);
        }
}

void o2net_unregister_hb_callbacks(void)
{
        o2hb_unregister_callback(NULL, &o2net_hb_up);
        o2hb_unregister_callback(NULL, &o2net_hb_down);
}

int o2net_register_hb_callbacks(void)
{
        int ret;

        o2hb_setup_callback(&o2net_hb_down, O2HB_NODE_DOWN_CB,
                            o2net_hb_node_down_cb, NULL, O2NET_HB_PRI);
        o2hb_setup_callback(&o2net_hb_up, O2HB_NODE_UP_CB,
                            o2net_hb_node_up_cb, NULL, O2NET_HB_PRI);

        ret = o2hb_register_callback(NULL, &o2net_hb_up);
        if (ret == 0)
                ret = o2hb_register_callback(NULL, &o2net_hb_down);

        if (ret)
                o2net_unregister_hb_callbacks();

        return ret;
}

/* ------------------------------------------------------------ */

static int o2net_accept_one(struct socket *sock)
{
        int ret, slen;
        struct sockaddr_in sin;
        struct socket *new_sock = NULL;
        struct o2nm_node *node = NULL;
        struct o2net_sock_container *sc = NULL;
        struct o2net_node *nn;

        BUG_ON(sock == NULL);
        ret = sock_create_lite(sock->sk->sk_family, sock->sk->sk_type,
                               sock->sk->sk_protocol, &new_sock);
        if (ret)
                goto out;

        new_sock->type = sock->type;
        new_sock->ops = sock->ops;
        ret = sock->ops->accept(sock, new_sock, O_NONBLOCK);
        if (ret < 0)
                goto out;

        new_sock->sk->sk_allocation = GFP_ATOMIC;

        ret = o2net_set_nodelay(new_sock);
        if (ret) {
                mlog(ML_ERROR, "setting TCP_NODELAY failed with %d\n", ret);
                goto out;
        }

        slen = sizeof(sin);
        ret = new_sock->ops->getname(new_sock, (struct sockaddr *) &sin,
                                       &slen, 1);
        if (ret < 0)
                goto out;

        node = o2nm_get_node_by_ip(sin.sin_addr.s_addr);
        if (node == NULL) {
                mlog(ML_NOTICE, "attempt to connect from unknown node at %pI4:%d\n",
                     &sin.sin_addr.s_addr, ntohs(sin.sin_port));
                ret = -EINVAL;
                goto out;
        }

        if (o2nm_this_node() > node->nd_num) {
                mlog(ML_NOTICE, "unexpected connect attempted from a lower "
                     "numbered node '%s' at " "%pI4:%d with num %u\n",
                     node->nd_name, &sin.sin_addr.s_addr,
                     ntohs(sin.sin_port), node->nd_num);
                ret = -EINVAL;
                goto out;
        }

        /* this happens all the time when the other node sees our heartbeat
         * and tries to connect before we see their heartbeat */
        if (!o2hb_check_node_heartbeating_from_callback(node->nd_num)) {
                mlog(ML_CONN, "attempt to connect from node '%s' at "
                     "%pI4:%d but it isn't heartbeating\n",
                     node->nd_name, &sin.sin_addr.s_addr,
                     ntohs(sin.sin_port));
                ret = -EINVAL;
                goto out;
        }

        nn = o2net_nn_from_num(node->nd_num);

        spin_lock(&nn->nn_lock);
        if (nn->nn_sc)
                ret = -EBUSY;
        else
                ret = 0;
        spin_unlock(&nn->nn_lock);
        if (ret) {
                mlog(ML_NOTICE, "attempt to connect from node '%s' at "
                     "%pI4:%d but it already has an open connection\n",
                     node->nd_name, &sin.sin_addr.s_addr,
                     ntohs(sin.sin_port));
                goto out;
        }

        sc = sc_alloc(node);
        if (sc == NULL) {
                ret = -ENOMEM;
                goto out;
        }

        sc->sc_sock = new_sock;
        new_sock = NULL;

        spin_lock(&nn->nn_lock);
        atomic_set(&nn->nn_timeout, 0);
        o2net_set_nn_state(nn, sc, 0, 0);
        spin_unlock(&nn->nn_lock);

        o2net_register_callbacks(sc->sc_sock->sk, sc);
        o2net_sc_queue_work(sc, &sc->sc_rx_work);

        o2net_initialize_handshake();
        o2net_sendpage(sc, o2net_hand, sizeof(*o2net_hand));

out:
        if (new_sock)
                sock_release(new_sock);
        if (node)
                o2nm_node_put(node);
        if (sc)
                sc_put(sc);
        return ret;
}

static void o2net_accept_many(struct work_struct *work)
{
        struct socket *sock = o2net_listen_sock;
        while (o2net_accept_one(sock) == 0)
                cond_resched();
}

static void o2net_listen_data_ready(struct sock *sk, int bytes)
{
        void (*ready)(struct sock *sk, int bytes);

        read_lock(&sk->sk_callback_lock);
        ready = sk->sk_user_data;
        if (ready == NULL) { /* check for teardown race */
                ready = sk->sk_data_ready;
                goto out;
        }

        /* ->sk_data_ready is also called for a newly established child socket
         * before it has been accepted and the acceptor has set up their
         * data_ready.. we only want to queue listen work for our listening
         * socket */
        if (sk->sk_state == TCP_LISTEN) {
                mlog(ML_TCP, "bytes: %d\n", bytes);
                queue_work(o2net_wq, &o2net_listen_work);
        }

out:
        read_unlock(&sk->sk_callback_lock);
        ready(sk, bytes);
}

static int o2net_open_listening_sock(__be32 addr, __be16 port)
{
        struct socket *sock = NULL;
        int ret;
        struct sockaddr_in sin = {
                .sin_family = PF_INET,
                .sin_addr = { .s_addr = addr },
                .sin_port = port,
        };

        ret = sock_create(PF_INET, SOCK_STREAM, IPPROTO_TCP, &sock);
        if (ret < 0) {
                mlog(ML_ERROR, "unable to create socket, ret=%d\n", ret);
                goto out;
        }

        sock->sk->sk_allocation = GFP_ATOMIC;

        write_lock_bh(&sock->sk->sk_callback_lock);
        sock->sk->sk_user_data = sock->sk->sk_data_ready;
        sock->sk->sk_data_ready = o2net_listen_data_ready;
        write_unlock_bh(&sock->sk->sk_callback_lock);

        o2net_listen_sock = sock;
        INIT_WORK(&o2net_listen_work, o2net_accept_many);

        sock->sk->sk_reuse = 1;
        ret = sock->ops->bind(sock, (struct sockaddr *)&sin, sizeof(sin));
        if (ret < 0) {
                mlog(ML_ERROR, "unable to bind socket at %pI4:%u, "
                     "ret=%d\n", &addr, ntohs(port), ret);
                goto out;
        }

        ret = sock->ops->listen(sock, 64);
        if (ret < 0) {
                mlog(ML_ERROR, "unable to listen on %pI4:%u, ret=%d\n",
                     &addr, ntohs(port), ret);
        }

out:
        if (ret) {
                o2net_listen_sock = NULL;
                if (sock)
                        sock_release(sock);
        }
        return ret;
}

/*
 * called from node manager when we should bring up our network listening
 * socket.  node manager handles all the serialization to only call this
 * once and to match it with o2net_stop_listening().  note,
 * o2nm_this_node() doesn't work yet as we're being called while it
 * is being set up.
 */
int o2net_start_listening(struct o2nm_node *node)
{
        int ret = 0;

        BUG_ON(o2net_wq != NULL);
        BUG_ON(o2net_listen_sock != NULL);

        mlog(ML_KTHREAD, "starting o2net thread...\n");
        o2net_wq = create_singlethread_workqueue("o2net");
        if (o2net_wq == NULL) {
                mlog(ML_ERROR, "unable to launch o2net thread\n");
                return -ENOMEM; /* ? */
        }

        ret = o2net_open_listening_sock(node->nd_ipv4_address,
                                        node->nd_ipv4_port);
        if (ret) {
                destroy_workqueue(o2net_wq);
                o2net_wq = NULL;
        } else
                o2quo_conn_up(node->nd_num);

        return ret;
}

/* again, o2nm_this_node() doesn't work here as we're involved in
 * tearing it down */
void o2net_stop_listening(struct o2nm_node *node)
{
        struct socket *sock = o2net_listen_sock;
        size_t i;

        BUG_ON(o2net_wq == NULL);
        BUG_ON(o2net_listen_sock == NULL);

        /* stop the listening socket from generating work */
        write_lock_bh(&sock->sk->sk_callback_lock);
        sock->sk->sk_data_ready = sock->sk->sk_user_data;
        sock->sk->sk_user_data = NULL;
        write_unlock_bh(&sock->sk->sk_callback_lock);

        for (i = 0; i < ARRAY_SIZE(o2net_nodes); i++) {
                struct o2nm_node *node = o2nm_get_node_by_num(i);
                if (node) {
                        o2net_disconnect_node(node);
                        o2nm_node_put(node);
                }
        }

        /* finish all work and tear down the work queue */
        mlog(ML_KTHREAD, "waiting for o2net thread to exit....\n");
        destroy_workqueue(o2net_wq);
        o2net_wq = NULL;

        sock_release(o2net_listen_sock);
        o2net_listen_sock = NULL;

        o2quo_conn_err(node->nd_num);
}

/* ------------------------------------------------------------ */

int o2net_init(void)
{
        unsigned long i;

        o2quo_init();

        if (o2net_debugfs_init())
                return -ENOMEM;

        o2net_hand = kzalloc(sizeof(struct o2net_handshake), GFP_KERNEL);
        o2net_keep_req = kzalloc(sizeof(struct o2net_msg), GFP_KERNEL);
        o2net_keep_resp = kzalloc(sizeof(struct o2net_msg), GFP_KERNEL);
        if (!o2net_hand || !o2net_keep_req || !o2net_keep_resp) {
                kfree(o2net_hand);
                kfree(o2net_keep_req);
                kfree(o2net_keep_resp);
                return -ENOMEM;
        }

        o2net_hand->protocol_version = cpu_to_be64(O2NET_PROTOCOL_VERSION);
        o2net_hand->connector_id = cpu_to_be64(1);

        o2net_keep_req->magic = cpu_to_be16(O2NET_MSG_KEEP_REQ_MAGIC);
        o2net_keep_resp->magic = cpu_to_be16(O2NET_MSG_KEEP_RESP_MAGIC);

        for (i = 0; i < ARRAY_SIZE(o2net_nodes); i++) {
                struct o2net_node *nn = o2net_nn_from_num(i);

                atomic_set(&nn->nn_timeout, 0);
                spin_lock_init(&nn->nn_lock);
                INIT_DELAYED_WORK(&nn->nn_connect_work, o2net_start_connect);
                INIT_DELAYED_WORK(&nn->nn_connect_expired,
                                  o2net_connect_expired);
                INIT_DELAYED_WORK(&nn->nn_still_up, o2net_still_up);
                /* until we see hb from a node we'll return einval */
                nn->nn_persistent_error = -ENOTCONN;
                init_waitqueue_head(&nn->nn_sc_wq);
                idr_init(&nn->nn_status_idr);
                INIT_LIST_HEAD(&nn->nn_status_list);
        }

        return 0;
}

void o2net_exit(void)
{
        o2quo_exit();
        kfree(o2net_hand);
        kfree(o2net_keep_req);
        kfree(o2net_keep_resp);
        o2net_debugfs_exit();
}