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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);

/*
 * FIXME: These should use to_o2nm_cluster_from_node(), but we end up
 * losing our parent link to the cluster during shutdown. This can be
 * solved by adding a pre-removal callback to configfs, or passing
 * around the cluster with the node. -jeffm
 */
static inline int o2net_reconnect_delay(struct o2nm_node *node)
{
      return o2nm_single_cluster->cl_reconnect_delay_ms;
}

static inline int o2net_keepalive_delay(struct o2nm_node *node)
{
      return o2nm_single_cluster->cl_keepalive_delay_ms;
}

static inline int o2net_idle_timeout(struct o2nm_node *node)
{
      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;

      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;
      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);

      /* we won't reconnect after our valid conn goes away for
       * this hb iteration.. here so it shows up in the logs */
      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));
            /* this is a bit of a hack.  we only try reconnecting
             * when heartbeating starts until we get a connection.
             * if that connection then dies we don't try reconnecting.
             * the only way to start connecting again is to down
             * heartbeat and bring it back up. */
            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(sc->sc_node)))
                  - jiffies;
            if (delay > msecs_to_jiffies(o2net_reconnect_delay(sc->sc_node)))
                  delay = 0;
            mlog(ML_CONN, "queueing conn attempt in %lu jiffies\n", delay);
            queue_delayed_work(o2net_wq, &nn->nn_connect_work, 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, error = 0;
      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),
      };

      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;
      }

      ret = wait_event_interruptible(nn->nn_sc_wq,
                               o2net_tx_can_proceed(nn, &sc, &error));
      if (!ret && error)
            ret = error;
      if (ret)
            goto out;

      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);

      /* 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 */
      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:
      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(sc->sc_node)) {
            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(sc->sc_node));
            o2net_ensure_shutdown(nn, sc, -ENOTCONN);
            return -1;
      }

      if (be32_to_cpu(hand->o2net_keepalive_delay_ms) !=
                  o2net_keepalive_delay(sc->sc_node)) {
            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(sc->sc_node));
            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);
            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(NULL));
      o2net_hand->o2net_keepalive_delay_ms = cpu_to_be32(
            o2net_keepalive_delay(NULL));
      o2net_hand->o2net_reconnect_delay_ms = cpu_to_be32(
            o2net_reconnect_delay(NULL));
}

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

/* 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 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(sc->sc_node) / 1000,
                 o2net_idle_timeout(sc->sc_node) % 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);

      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(sc->sc_node)));
      do_gettimeofday(&sc->sc_tv_timer);
      mod_timer(&sc->sc_idle_timeout,
             jiffies + msecs_to_jiffies(o2net_idle_timeout(sc->sc_node)));
}

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;

      /* 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 */
      stop = (nn->nn_sc || nn->nn_persistent_error);
      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 %u.%u.%u.%u\n",
                 ret, NIPQUAD(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) {
            struct o2nm_node *node = nn->nn_sc->sc_node;
            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(node) / 1000,
                 o2net_idle_timeout(node) % 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);
      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(node)) + 1);

      if (node_num != o2nm_this_node()) {
            /* heartbeat doesn't work unless a local node number is
             * configured and doing so brings up the o2net_wq, so we can
             * use it.. */
            queue_delayed_work(o2net_wq, &nn->nn_connect_expired,
                               msecs_to_jiffies(o2net_idle_timeout(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);
            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 "
                 "%u.%u.%u.%u:%d\n", NIPQUAD(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 " "%u.%u.%u.%u:%d with num %u\n",
                 node->nd_name, NIPQUAD(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 "
                 "%u.%u.%u.%u:%d but it isn't heartbeating\n",
                 node->nd_name, NIPQUAD(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 "
                 "%u.%u.%u.%u:%d but it already has an open connection\n",
                 node->nd_name, NIPQUAD(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);
      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 %u.%u.%u.%u:%u, "
                 "ret=%d\n", NIPQUAD(addr), ntohs(port), ret);
            goto out;
      }

      ret = sock->ops->listen(sock, 64);
      if (ret < 0) {
            mlog(ML_ERROR, "unable to listen on %u.%u.%u.%u:%u, ret=%d\n",
                 NIPQUAD(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();

      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);

            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);
}

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