lowcomms.c

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/******************************************************************************
*******************************************************************************
**
**  Copyright (C) Sistina Software, Inc.  1997-2003  All rights reserved.
**  Copyright (C) 2004-2009 Red Hat, Inc.  All rights reserved.
**
**  This copyrighted material is made available to anyone wishing to use,
**  modify, copy, or redistribute it subject to the terms and conditions
**  of the GNU General Public License v.2.
**
*******************************************************************************
******************************************************************************/

/*
 * lowcomms.c
 *
 * This is the "low-level" comms layer.
 *
 * It is responsible for sending/receiving messages
 * from other nodes in the cluster.
 *
 * Cluster nodes are referred to by their nodeids. nodeids are
 * simply 32 bit numbers to the locking module - if they need to
 * be expanded for the cluster infrastructure then that is its
 * responsibility. It is this layer's
 * responsibility to resolve these into IP address or
 * whatever it needs for inter-node communication.
 *
 * The comms level is two kernel threads that deal mainly with
 * the receiving of messages from other nodes and passing them
 * up to the mid-level comms layer (which understands the
 * message format) for execution by the locking core, and
 * a send thread which does all the setting up of connections
 * to remote nodes and the sending of data. Threads are not allowed
 * to send their own data because it may cause them to wait in times
 * of high load. Also, this way, the sending thread can collect together
 * messages bound for one node and send them in one block.
 *
 * lowcomms will choose to use either TCP or SCTP as its transport layer
 * depending on the configuration variable 'protocol'. This should be set
 * to 0 (default) for TCP or 1 for SCTP. It should be configured using a
 * cluster-wide mechanism as it must be the same on all nodes of the cluster
 * for the DLM to function.
 *
 */

#include <asm/ioctls.h>
#include <net/sock.h>
#include <net/tcp.h>
#include <linux/pagemap.h>
#include <linux/file.h>
#include <linux/mutex.h>
#include <linux/sctp.h>
#include <linux/slab.h>
#include <net/sctp/sctp.h>
#include <net/sctp/user.h>
#include <net/ipv6.h>

#include "dlm_internal.h"
#include "lowcomms.h"
#include "midcomms.h"
#include "config.h"

#define NEEDED_RMEM (4*1024*1024)
#define CONN_HASH_SIZE 32

/* Number of messages to send before rescheduling */
#define MAX_SEND_MSG_COUNT 25

struct cbuf {
    unsigned int base;
    unsigned int len;
    unsigned int mask;
};

static void cbuf_add(struct cbuf *cb, int n)
{
    cb->len += n;
}

static int cbuf_data(struct cbuf *cb)
{
    return ((cb->base + cb->len) & cb->mask);
}

static void cbuf_init(struct cbuf *cb, int size)
{
    cb->base = cb->len = 0;
    cb->mask = size-1;
}

static void cbuf_eat(struct cbuf *cb, int n)
{
    cb->len  -= n;
    cb->base += n;
    cb->base &= cb->mask;
}

static bool cbuf_empty(struct cbuf *cb)
{
    return cb->len == 0;
}

struct connection {
    struct socket *sock;    /* NULL if not connected */
    uint32_t nodeid;    /* So we know who we are in the list */
    struct mutex sock_mutex;
    unsigned long flags;
#define CF_READ_PENDING 1
#define CF_WRITE_PENDING 2
#define CF_CONNECT_PENDING 3
#define CF_INIT_PENDING 4
#define CF_IS_OTHERCON 5
#define CF_CLOSE 6
#define CF_APP_LIMITED 7
    struct list_head writequeue;  /* List of outgoing writequeue_entries */
    spinlock_t writequeue_lock;
    int (*rx_action) (struct connection *); /* What to do when active */
    void (*connect_action) (struct connection *);   /* What to do to connect */
    struct page *rx_page;
    struct cbuf cb;
    int retries;
#define MAX_CONNECT_RETRIES 3
    int sctp_assoc;
    struct hlist_node list;
    struct connection *othercon;
    struct work_struct rwork; /* Receive workqueue */
    struct work_struct swork; /* Send workqueue */
};
#define sock2con(x) ((struct connection *)(x)->sk_user_data)

/* An entry waiting to be sent */
struct writequeue_entry {
    struct list_head list;
    struct page *page;
    int offset;
    int len;
    int end;
    int users;
    struct connection *con;
};

struct dlm_node_addr {
    struct list_head list;
    int nodeid;
    int addr_count;
    struct sockaddr_storage *addr[DLM_MAX_ADDR_COUNT];
};

static LIST_HEAD(dlm_node_addrs);
static DEFINE_SPINLOCK(dlm_node_addrs_spin);

static struct sockaddr_storage *dlm_local_addr[DLM_MAX_ADDR_COUNT];
static int dlm_local_count;
static int dlm_allow_conn;

/* Work queues */
static struct workqueue_struct *recv_workqueue;
static struct workqueue_struct *send_workqueue;

static struct hlist_head connection_hash[CONN_HASH_SIZE];
static DEFINE_MUTEX(connections_lock);
static struct kmem_cache *con_cache;

static void process_recv_sockets(struct work_struct *work);
static void process_send_sockets(struct work_struct *work);


/* This is deliberately very simple because most clusters have simple
   sequential nodeids, so we should be able to go straight to a connection
   struct in the array */
static inline int nodeid_hash(int nodeid)
{
    return nodeid & (CONN_HASH_SIZE-1);
}

static struct connection *__find_con(int nodeid)
{
    int r;
    struct hlist_node *h;
    struct connection *con;

    r = nodeid_hash(nodeid);

    hlist_for_each_entry(con, h, &connection_hash[r], list) {
        if (con->nodeid == nodeid)
            return con;
    }
    return NULL;
}

/*
 * If 'allocation' is zero then we don't attempt to create a new
 * connection structure for this node.
 */
static struct connection *__nodeid2con(int nodeid, gfp_t alloc)
{
    struct connection *con = NULL;
    int r;

    con = __find_con(nodeid);
    if (con || !alloc)
        return con;

    con = kmem_cache_zalloc(con_cache, alloc);
    if (!con)
        return NULL;

    r = nodeid_hash(nodeid);
    hlist_add_head(&con->list, &connection_hash[r]);

    con->nodeid = nodeid;
    mutex_init(&con->sock_mutex);
    INIT_LIST_HEAD(&con->writequeue);
    spin_lock_init(&con->writequeue_lock);
    INIT_WORK(&con->swork, process_send_sockets);
    INIT_WORK(&con->rwork, process_recv_sockets);

    /* Setup action pointers for child sockets */
    if (con->nodeid) {
        struct connection *zerocon = __find_con(0);

        con->connect_action = zerocon->connect_action;
        if (!con->rx_action)
            con->rx_action = zerocon->rx_action;
    }

    return con;
}

/* Loop round all connections */
static void foreach_conn(void (*conn_func)(struct connection *c))
{
    int i;
    struct hlist_node *h, *n;
    struct connection *con;

    for (i = 0; i < CONN_HASH_SIZE; i++) {
        hlist_for_each_entry_safe(con, h, n, &connection_hash[i], list){
            conn_func(con);
        }
    }
}

static struct connection *nodeid2con(int nodeid, gfp_t allocation)
{
    struct connection *con;

    mutex_lock(&connections_lock);
    con = __nodeid2con(nodeid, allocation);
    mutex_unlock(&connections_lock);

    return con;
}

/* This is a bit drastic, but only called when things go wrong */
static struct connection *assoc2con(int assoc_id)
{
    int i;
    struct hlist_node *h;
    struct connection *con;

    mutex_lock(&connections_lock);

    for (i = 0 ; i < CONN_HASH_SIZE; i++) {
        hlist_for_each_entry(con, h, &connection_hash[i], list) {
            if (con->sctp_assoc == assoc_id) {
                mutex_unlock(&connections_lock);
                return con;
            }
        }
    }
    mutex_unlock(&connections_lock);
    return NULL;
}

static struct dlm_node_addr *find_node_addr(int nodeid)
{
    struct dlm_node_addr *na;

    list_for_each_entry(na, &dlm_node_addrs, list) {
        if (na->nodeid == nodeid)
            return na;
    }
    return NULL;
}

static int addr_compare(struct sockaddr_storage *x, struct sockaddr_storage *y)
{
    switch (x->ss_family) {
    case AF_INET: {
        struct sockaddr_in *sinx = (struct sockaddr_in *)x;
        struct sockaddr_in *siny = (struct sockaddr_in *)y;
        if (sinx->sin_addr.s_addr != siny->sin_addr.s_addr)
            return 0;
        if (sinx->sin_port != siny->sin_port)
            return 0;
        break;
    }
    case AF_INET6: {
        struct sockaddr_in6 *sinx = (struct sockaddr_in6 *)x;
        struct sockaddr_in6 *siny = (struct sockaddr_in6 *)y;
        if (!ipv6_addr_equal(&sinx->sin6_addr, &siny->sin6_addr))
            return 0;
        if (sinx->sin6_port != siny->sin6_port)
            return 0;
        break;
    }
    default:
        return 0;
    }
    return 1;
}

static int nodeid_to_addr(int nodeid, struct sockaddr_storage *sas_out,
              struct sockaddr *sa_out)
{
    struct sockaddr_storage sas;
    struct dlm_node_addr *na;

    if (!dlm_local_count)
        return -1;

    spin_lock(&dlm_node_addrs_spin);
    na = find_node_addr(nodeid);
    if (na && na->addr_count)
        memcpy(&sas, na->addr[0], sizeof(struct sockaddr_storage));
    spin_unlock(&dlm_node_addrs_spin);

    if (!na)
        return -EEXIST;

    if (!na->addr_count)
        return -ENOENT;

    if (sas_out)
        memcpy(sas_out, &sas, sizeof(struct sockaddr_storage));

    if (!sa_out)
        return 0;

    if (dlm_local_addr[0]->ss_family == AF_INET) {
        struct sockaddr_in *in4  = (struct sockaddr_in *) &sas;
        struct sockaddr_in *ret4 = (struct sockaddr_in *) sa_out;
        ret4->sin_addr.s_addr = in4->sin_addr.s_addr;
    } else {
        struct sockaddr_in6 *in6  = (struct sockaddr_in6 *) &sas;
        struct sockaddr_in6 *ret6 = (struct sockaddr_in6 *) sa_out;
        ret6->sin6_addr = in6->sin6_addr;
    }

    return 0;
}

static int addr_to_nodeid(struct sockaddr_storage *addr, int *nodeid)
{
    struct dlm_node_addr *na;
    int rv = -EEXIST;

    spin_lock(&dlm_node_addrs_spin);
    list_for_each_entry(na, &dlm_node_addrs, list) {
        if (!na->addr_count)
            continue;

        if (!addr_compare(na->addr[0], addr))
            continue;

        *nodeid = na->nodeid;
        rv = 0;
        break;
    }
    spin_unlock(&dlm_node_addrs_spin);
    return rv;
}

int dlm_lowcomms_addr(int nodeid, struct sockaddr_storage *addr, int len)
{
    struct sockaddr_storage *new_addr;
    struct dlm_node_addr *new_node, *na;

    new_node = kzalloc(sizeof(struct dlm_node_addr), GFP_NOFS);
    if (!new_node)
        return -ENOMEM;

    new_addr = kzalloc(sizeof(struct sockaddr_storage), GFP_NOFS);
    if (!new_addr) {
        kfree(new_node);
        return -ENOMEM;
    }

    memcpy(new_addr, addr, len);

    spin_lock(&dlm_node_addrs_spin);
    na = find_node_addr(nodeid);
    if (!na) {
        new_node->nodeid = nodeid;
        new_node->addr[0] = new_addr;
        new_node->addr_count = 1;
        list_add(&new_node->list, &dlm_node_addrs);
        spin_unlock(&dlm_node_addrs_spin);
        return 0;
    }

    if (na->addr_count >= DLM_MAX_ADDR_COUNT) {
        spin_unlock(&dlm_node_addrs_spin);
        kfree(new_addr);
        kfree(new_node);
        return -ENOSPC;
    }

    na->addr[na->addr_count++] = new_addr;
    spin_unlock(&dlm_node_addrs_spin);
    kfree(new_node);
    return 0;
}

/* Data available on socket or listen socket received a connect */
static void lowcomms_data_ready(struct sock *sk, int count_unused)
{
    struct connection *con = sock2con(sk);
    if (con && !test_and_set_bit(CF_READ_PENDING, &con->flags))
        queue_work(recv_workqueue, &con->rwork);
}

static void lowcomms_write_space(struct sock *sk)
{
    struct connection *con = sock2con(sk);

    if (!con)
        return;

    clear_bit(SOCK_NOSPACE, &con->sock->flags);

    if (test_and_clear_bit(CF_APP_LIMITED, &con->flags)) {
        con->sock->sk->sk_write_pending--;
        clear_bit(SOCK_ASYNC_NOSPACE, &con->sock->flags);
    }

    if (!test_and_set_bit(CF_WRITE_PENDING, &con->flags))
        queue_work(send_workqueue, &con->swork);
}

static inline void lowcomms_connect_sock(struct connection *con)
{
    if (test_bit(CF_CLOSE, &con->flags))
        return;
    if (!test_and_set_bit(CF_CONNECT_PENDING, &con->flags))
        queue_work(send_workqueue, &con->swork);
}

static void lowcomms_state_change(struct sock *sk)
{
    if (sk->sk_state == TCP_ESTABLISHED)
        lowcomms_write_space(sk);
}

int dlm_lowcomms_connect_node(int nodeid)
{
    struct connection *con;

    /* with sctp there's no connecting without sending */
    if (dlm_config.ci_protocol != 0)
        return 0;

    if (nodeid == dlm_our_nodeid())
        return 0;

    con = nodeid2con(nodeid, GFP_NOFS);
    if (!con)
        return -ENOMEM;
    lowcomms_connect_sock(con);
    return 0;
}

/* Make a socket active */
static void add_sock(struct socket *sock, struct connection *con)
{
    con->sock = sock;

    /* Install a data_ready callback */
    con->sock->sk->sk_data_ready = lowcomms_data_ready;
    con->sock->sk->sk_write_space = lowcomms_write_space;
    con->sock->sk->sk_state_change = lowcomms_state_change;
    con->sock->sk->sk_user_data = con;
    con->sock->sk->sk_allocation = GFP_NOFS;
}

/* Add the port number to an IPv6 or 4 sockaddr and return the address
   length */
static void make_sockaddr(struct sockaddr_storage *saddr, uint16_t port,
              int *addr_len)
{
    saddr->ss_family =  dlm_local_addr[0]->ss_family;
    if (saddr->ss_family == AF_INET) {
        struct sockaddr_in *in4_addr = (struct sockaddr_in *)saddr;
        in4_addr->sin_port = cpu_to_be16(port);
        *addr_len = sizeof(struct sockaddr_in);
        memset(&in4_addr->sin_zero, 0, sizeof(in4_addr->sin_zero));
    } else {
        struct sockaddr_in6 *in6_addr = (struct sockaddr_in6 *)saddr;
        in6_addr->sin6_port = cpu_to_be16(port);
        *addr_len = sizeof(struct sockaddr_in6);
    }
    memset((char *)saddr + *addr_len, 0, sizeof(struct sockaddr_storage) - *addr_len);
}

/* Close a remote connection and tidy up */
static void close_connection(struct connection *con, bool and_other)
{
    mutex_lock(&con->sock_mutex);

    if (con->sock) {
        sock_release(con->sock);
        con->sock = NULL;
    }
    if (con->othercon && and_other) {
        /* Will only re-enter once. */
        close_connection(con->othercon, false);
    }
    if (con->rx_page) {
        __free_page(con->rx_page);
        con->rx_page = NULL;
    }

    con->retries = 0;
    mutex_unlock(&con->sock_mutex);
}

/* We only send shutdown messages to nodes that are not part of the cluster */
static void sctp_send_shutdown(sctp_assoc_t associd)
{
    static char outcmsg[CMSG_SPACE(sizeof(struct sctp_sndrcvinfo))];
    struct msghdr outmessage;
    struct cmsghdr *cmsg;
    struct sctp_sndrcvinfo *sinfo;
    int ret;
    struct connection *con;

    con = nodeid2con(0,0);
    BUG_ON(con == NULL);

    outmessage.msg_name = NULL;
    outmessage.msg_namelen = 0;
    outmessage.msg_control = outcmsg;
    outmessage.msg_controllen = sizeof(outcmsg);
    outmessage.msg_flags = MSG_EOR;

    cmsg = CMSG_FIRSTHDR(&outmessage);
    cmsg->cmsg_level = IPPROTO_SCTP;
    cmsg->cmsg_type = SCTP_SNDRCV;
    cmsg->cmsg_len = CMSG_LEN(sizeof(struct sctp_sndrcvinfo));
    outmessage.msg_controllen = cmsg->cmsg_len;
    sinfo = CMSG_DATA(cmsg);
    memset(sinfo, 0x00, sizeof(struct sctp_sndrcvinfo));

    sinfo->sinfo_flags |= MSG_EOF;
    sinfo->sinfo_assoc_id = associd;

    ret = kernel_sendmsg(con->sock, &outmessage, NULL, 0, 0);

    if (ret != 0)
        log_print("send EOF to node failed: %d", ret);
}

static void sctp_init_failed_foreach(struct connection *con)
{
    con->sctp_assoc = 0;
    if (test_and_clear_bit(CF_CONNECT_PENDING, &con->flags)) {
        if (!test_and_set_bit(CF_WRITE_PENDING, &con->flags))
            queue_work(send_workqueue, &con->swork);
    }
}

/* INIT failed but we don't know which node...
   restart INIT on all pending nodes */
static void sctp_init_failed(void)
{
    mutex_lock(&connections_lock);

    foreach_conn(sctp_init_failed_foreach);

    mutex_unlock(&connections_lock);
}

/* Something happened to an association */
static void process_sctp_notification(struct connection *con,
                      struct msghdr *msg, char *buf)
{
    union sctp_notification *sn = (union sctp_notification *)buf;

    if (sn->sn_header.sn_type == SCTP_ASSOC_CHANGE) {
        switch (sn->sn_assoc_change.sac_state) {

        case SCTP_COMM_UP:
        case SCTP_RESTART:
        {
            /* Check that the new node is in the lockspace */
            struct sctp_prim prim;
            int nodeid;
            int prim_len, ret;
            int addr_len;
            struct connection *new_con;

            /*
             * We get this before any data for an association.
             * We verify that the node is in the cluster and
             * then peel off a socket for it.
             */
            if ((int)sn->sn_assoc_change.sac_assoc_id <= 0) {
                log_print("COMM_UP for invalid assoc ID %d",
                     (int)sn->sn_assoc_change.sac_assoc_id);
                sctp_init_failed();
                return;
            }
            memset(&prim, 0, sizeof(struct sctp_prim));
            prim_len = sizeof(struct sctp_prim);
            prim.ssp_assoc_id = sn->sn_assoc_change.sac_assoc_id;

            ret = kernel_getsockopt(con->sock,
                        IPPROTO_SCTP,
                        SCTP_PRIMARY_ADDR,
                        (char*)&prim,
                        &prim_len);
            if (ret < 0) {
                log_print("getsockopt/sctp_primary_addr on "
                      "new assoc %d failed : %d",
                      (int)sn->sn_assoc_change.sac_assoc_id,
                      ret);

                /* Retry INIT later */
                new_con = assoc2con(sn->sn_assoc_change.sac_assoc_id);
                if (new_con)
                    clear_bit(CF_CONNECT_PENDING, &con->flags);
                return;
            }
            make_sockaddr(&prim.ssp_addr, 0, &addr_len);
            if (addr_to_nodeid(&prim.ssp_addr, &nodeid)) {
                unsigned char *b=(unsigned char *)&prim.ssp_addr;
                log_print("reject connect from unknown addr");
                print_hex_dump_bytes("ss: ", DUMP_PREFIX_NONE, 
                             b, sizeof(struct sockaddr_storage));
                sctp_send_shutdown(prim.ssp_assoc_id);
                return;
            }

            new_con = nodeid2con(nodeid, GFP_NOFS);
            if (!new_con)
                return;

            /* Peel off a new sock */
            sctp_lock_sock(con->sock->sk);
            ret = sctp_do_peeloff(con->sock->sk,
                sn->sn_assoc_change.sac_assoc_id,
                &new_con->sock);
            sctp_release_sock(con->sock->sk);
            if (ret < 0) {
                log_print("Can't peel off a socket for "
                      "connection %d to node %d: err=%d",
                      (int)sn->sn_assoc_change.sac_assoc_id,
                      nodeid, ret);
                return;
            }
            add_sock(new_con->sock, new_con);

            log_print("connecting to %d sctp association %d",
                 nodeid, (int)sn->sn_assoc_change.sac_assoc_id);

            /* Send any pending writes */
            clear_bit(CF_CONNECT_PENDING, &new_con->flags);
            clear_bit(CF_INIT_PENDING, &con->flags);
            if (!test_and_set_bit(CF_WRITE_PENDING, &new_con->flags)) {
                queue_work(send_workqueue, &new_con->swork);
            }
            if (!test_and_set_bit(CF_READ_PENDING, &new_con->flags))
                queue_work(recv_workqueue, &new_con->rwork);
        }
        break;

        case SCTP_COMM_LOST:
        case SCTP_SHUTDOWN_COMP:
        {
            con = assoc2con(sn->sn_assoc_change.sac_assoc_id);
            if (con) {
                con->sctp_assoc = 0;
            }
        }
        break;

        /* We don't know which INIT failed, so clear the PENDING flags
         * on them all.  if assoc_id is zero then it will then try
         * again */

        case SCTP_CANT_STR_ASSOC:
        {
            log_print("Can't start SCTP association - retrying");
            sctp_init_failed();
        }
        break;

        default:
            log_print("unexpected SCTP assoc change id=%d state=%d",
                  (int)sn->sn_assoc_change.sac_assoc_id,
                  sn->sn_assoc_change.sac_state);
        }
    }
}

/* Data received from remote end */
static int receive_from_sock(struct connection *con)
{
    int ret = 0;
    struct msghdr msg = {};
    struct kvec iov[2];
    unsigned len;
    int r;
    int call_again_soon = 0;
    int nvec;
    char incmsg[CMSG_SPACE(sizeof(struct sctp_sndrcvinfo))];

    mutex_lock(&con->sock_mutex);

    if (con->sock == NULL) {
        ret = -EAGAIN;
        goto out_close;
    }

    if (con->rx_page == NULL) {
        /*
         * This doesn't need to be atomic, but I think it should
         * improve performance if it is.
         */
        con->rx_page = alloc_page(GFP_ATOMIC);
        if (con->rx_page == NULL)
            goto out_resched;
        cbuf_init(&con->cb, PAGE_CACHE_SIZE);
    }

    /* Only SCTP needs these really */
    memset(&incmsg, 0, sizeof(incmsg));
    msg.msg_control = incmsg;
    msg.msg_controllen = sizeof(incmsg);

    /*
     * iov[0] is the bit of the circular buffer between the current end
     * point (cb.base + cb.len) and the end of the buffer.
     */
    iov[0].iov_len = con->cb.base - cbuf_data(&con->cb);
    iov[0].iov_base = page_address(con->rx_page) + cbuf_data(&con->cb);
    iov[1].iov_len = 0;
    nvec = 1;

    /*
     * iov[1] is the bit of the circular buffer between the start of the
     * buffer and the start of the currently used section (cb.base)
     */
    if (cbuf_data(&con->cb) >= con->cb.base) {
        iov[0].iov_len = PAGE_CACHE_SIZE - cbuf_data(&con->cb);
        iov[1].iov_len = con->cb.base;
        iov[1].iov_base = page_address(con->rx_page);
        nvec = 2;
    }
    len = iov[0].iov_len + iov[1].iov_len;

    r = ret = kernel_recvmsg(con->sock, &msg, iov, nvec, len,
                   MSG_DONTWAIT | MSG_NOSIGNAL);
    if (ret <= 0)
        goto out_close;

    /* Process SCTP notifications */
    if (msg.msg_flags & MSG_NOTIFICATION) {
        msg.msg_control = incmsg;
        msg.msg_controllen = sizeof(incmsg);

        process_sctp_notification(con, &msg,
                page_address(con->rx_page) + con->cb.base);
        mutex_unlock(&con->sock_mutex);
        return 0;
    }
    BUG_ON(con->nodeid == 0);

    if (ret == len)
        call_again_soon = 1;
    cbuf_add(&con->cb, ret);
    ret = dlm_process_incoming_buffer(con->nodeid,
                      page_address(con->rx_page),
                      con->cb.base, con->cb.len,
                      PAGE_CACHE_SIZE);
    if (ret == -EBADMSG) {
        log_print("lowcomms: addr=%p, base=%u, len=%u, "
              "iov_len=%u, iov_base[0]=%p, read=%d",
              page_address(con->rx_page), con->cb.base, con->cb.len,
              len, iov[0].iov_base, r);
    }
    if (ret < 0)
        goto out_close;
    cbuf_eat(&con->cb, ret);

    if (cbuf_empty(&con->cb) && !call_again_soon) {
        __free_page(con->rx_page);
        con->rx_page = NULL;
    }

    if (call_again_soon)
        goto out_resched;
    mutex_unlock(&con->sock_mutex);
    return 0;

out_resched:
    if (!test_and_set_bit(CF_READ_PENDING, &con->flags))
        queue_work(recv_workqueue, &con->rwork);
    mutex_unlock(&con->sock_mutex);
    return -EAGAIN;

out_close:
    mutex_unlock(&con->sock_mutex);
    if (ret != -EAGAIN) {
        close_connection(con, false);
        /* Reconnect when there is something to send */
    }
    /* Don't return success if we really got EOF */
    if (ret == 0)
        ret = -EAGAIN;

    return ret;
}

/* Listening socket is busy, accept a connection */
static int tcp_accept_from_sock(struct connection *con)
{
    int result;
    struct sockaddr_storage peeraddr;
    struct socket *newsock;
    int len;
    int nodeid;
    struct connection *newcon;
    struct connection *addcon;

    mutex_lock(&connections_lock);
    if (!dlm_allow_conn) {
        mutex_unlock(&connections_lock);
        return -1;
    }
    mutex_unlock(&connections_lock);

    memset(&peeraddr, 0, sizeof(peeraddr));
    result = sock_create_kern(dlm_local_addr[0]->ss_family, SOCK_STREAM,
                  IPPROTO_TCP, &newsock);
    if (result < 0)
        return -ENOMEM;

    mutex_lock_nested(&con->sock_mutex, 0);

    result = -ENOTCONN;
    if (con->sock == NULL)
        goto accept_err;

    newsock->type = con->sock->type;
    newsock->ops = con->sock->ops;

    result = con->sock->ops->accept(con->sock, newsock, O_NONBLOCK);
    if (result < 0)
        goto accept_err;

    /* Get the connected socket's peer */
    memset(&peeraddr, 0, sizeof(peeraddr));
    if (newsock->ops->getname(newsock, (struct sockaddr *)&peeraddr,
                  &len, 2)) {
        result = -ECONNABORTED;
        goto accept_err;
    }

    /* Get the new node's NODEID */
    make_sockaddr(&peeraddr, 0, &len);
    if (addr_to_nodeid(&peeraddr, &nodeid)) {
        unsigned char *b=(unsigned char *)&peeraddr;
        log_print("connect from non cluster node");
        print_hex_dump_bytes("ss: ", DUMP_PREFIX_NONE, 
                     b, sizeof(struct sockaddr_storage));
        sock_release(newsock);
        mutex_unlock(&con->sock_mutex);
        return -1;
    }

    log_print("got connection from %d", nodeid);

    /*  Check to see if we already have a connection to this node. This
     *  could happen if the two nodes initiate a connection at roughly
     *  the same time and the connections cross on the wire.
     *  In this case we store the incoming one in "othercon"
     */
    newcon = nodeid2con(nodeid, GFP_NOFS);
    if (!newcon) {
        result = -ENOMEM;
        goto accept_err;
    }
    mutex_lock_nested(&newcon->sock_mutex, 1);
    if (newcon->sock) {
        struct connection *othercon = newcon->othercon;

        if (!othercon) {
            othercon = kmem_cache_zalloc(con_cache, GFP_NOFS);
            if (!othercon) {
                log_print("failed to allocate incoming socket");
                mutex_unlock(&newcon->sock_mutex);
                result = -ENOMEM;
                goto accept_err;
            }
            othercon->nodeid = nodeid;
            othercon->rx_action = receive_from_sock;
            mutex_init(&othercon->sock_mutex);
            INIT_WORK(&othercon->swork, process_send_sockets);
            INIT_WORK(&othercon->rwork, process_recv_sockets);
            set_bit(CF_IS_OTHERCON, &othercon->flags);
        }
        if (!othercon->sock) {
            newcon->othercon = othercon;
            othercon->sock = newsock;
            newsock->sk->sk_user_data = othercon;
            add_sock(newsock, othercon);
            addcon = othercon;
        }
        else {
            printk("Extra connection from node %d attempted\n", nodeid);
            result = -EAGAIN;
            mutex_unlock(&newcon->sock_mutex);
            goto accept_err;
        }
    }
    else {
        newsock->sk->sk_user_data = newcon;
        newcon->rx_action = receive_from_sock;
        add_sock(newsock, newcon);
        addcon = newcon;
    }

    mutex_unlock(&newcon->sock_mutex);

    /*
     * Add it to the active queue in case we got data
     * between processing the accept adding the socket
     * to the read_sockets list
     */
    if (!test_and_set_bit(CF_READ_PENDING, &addcon->flags))
        queue_work(recv_workqueue, &addcon->rwork);
    mutex_unlock(&con->sock_mutex);

    return 0;

accept_err:
    mutex_unlock(&con->sock_mutex);
    sock_release(newsock);

    if (result != -EAGAIN)
        log_print("error accepting connection from node: %d", result);
    return result;
}

static void free_entry(struct writequeue_entry *e)
{
    __free_page(e->page);
    kfree(e);
}

/* Initiate an SCTP association.
   This is a special case of send_to_sock() in that we don't yet have a
   peeled-off socket for this association, so we use the listening socket
   and add the primary IP address of the remote node.
 */
static void sctp_init_assoc(struct connection *con)
{
    struct sockaddr_storage rem_addr;
    char outcmsg[CMSG_SPACE(sizeof(struct sctp_sndrcvinfo))];
    struct msghdr outmessage;
    struct cmsghdr *cmsg;
    struct sctp_sndrcvinfo *sinfo;
    struct connection *base_con;
    struct writequeue_entry *e;
    int len, offset;
    int ret;
    int addrlen;
    struct kvec iov[1];

    if (test_and_set_bit(CF_INIT_PENDING, &con->flags))
        return;

    if (con->retries++ > MAX_CONNECT_RETRIES)
        return;

    if (nodeid_to_addr(con->nodeid, NULL, (struct sockaddr *)&rem_addr)) {
        log_print("no address for nodeid %d", con->nodeid);
        return;
    }
    base_con = nodeid2con(0, 0);
    BUG_ON(base_con == NULL);

    make_sockaddr(&rem_addr, dlm_config.ci_tcp_port, &addrlen);

    outmessage.msg_name = &rem_addr;
    outmessage.msg_namelen = addrlen;
    outmessage.msg_control = outcmsg;
    outmessage.msg_controllen = sizeof(outcmsg);
    outmessage.msg_flags = MSG_EOR;

    spin_lock(&con->writequeue_lock);

    if (list_empty(&con->writequeue)) {
        spin_unlock(&con->writequeue_lock);
        log_print("writequeue empty for nodeid %d", con->nodeid);
        return;
    }

    e = list_first_entry(&con->writequeue, struct writequeue_entry, list);
    len = e->len;
    offset = e->offset;
    spin_unlock(&con->writequeue_lock);

    /* Send the first block off the write queue */
    iov[0].iov_base = page_address(e->page)+offset;
    iov[0].iov_len = len;

    cmsg = CMSG_FIRSTHDR(&outmessage);
    cmsg->cmsg_level = IPPROTO_SCTP;
    cmsg->cmsg_type = SCTP_SNDRCV;
    cmsg->cmsg_len = CMSG_LEN(sizeof(struct sctp_sndrcvinfo));
    sinfo = CMSG_DATA(cmsg);
    memset(sinfo, 0x00, sizeof(struct sctp_sndrcvinfo));
    sinfo->sinfo_ppid = cpu_to_le32(dlm_our_nodeid());
    outmessage.msg_controllen = cmsg->cmsg_len;

    ret = kernel_sendmsg(base_con->sock, &outmessage, iov, 1, len);
    if (ret < 0) {
        log_print("Send first packet to node %d failed: %d",
              con->nodeid, ret);

        /* Try again later */
        clear_bit(CF_CONNECT_PENDING, &con->flags);
        clear_bit(CF_INIT_PENDING, &con->flags);
    }
    else {
        spin_lock(&con->writequeue_lock);
        e->offset += ret;
        e->len -= ret;

        if (e->len == 0 && e->users == 0) {
            list_del(&e->list);
            free_entry(e);
        }
        spin_unlock(&con->writequeue_lock);
    }
}

/* Connect a new socket to its peer */
static void tcp_connect_to_sock(struct connection *con)
{
    struct sockaddr_storage saddr, src_addr;
    int addr_len;
    struct socket *sock = NULL;
    int one = 1;
    int result;

    if (con->nodeid == 0) {
        log_print("attempt to connect sock 0 foiled");
        return;
    }

    mutex_lock(&con->sock_mutex);
    if (con->retries++ > MAX_CONNECT_RETRIES)
        goto out;

    /* Some odd races can cause double-connects, ignore them */
    if (con->sock)
        goto out;

    /* Create a socket to communicate with */
    result = sock_create_kern(dlm_local_addr[0]->ss_family, SOCK_STREAM,
                  IPPROTO_TCP, &sock);
    if (result < 0)
        goto out_err;

    memset(&saddr, 0, sizeof(saddr));
    result = nodeid_to_addr(con->nodeid, &saddr, NULL);
    if (result < 0) {
        log_print("no address for nodeid %d", con->nodeid);
        goto out_err;
    }

    sock->sk->sk_user_data = con;
    con->rx_action = receive_from_sock;
    con->connect_action = tcp_connect_to_sock;
    add_sock(sock, con);

    /* Bind to our cluster-known address connecting to avoid
       routing problems */
    memcpy(&src_addr, dlm_local_addr[0], sizeof(src_addr));
    make_sockaddr(&src_addr, 0, &addr_len);
    result = sock->ops->bind(sock, (struct sockaddr *) &src_addr,
                 addr_len);
    if (result < 0) {
        log_print("could not bind for connect: %d", result);
        /* This *may* not indicate a critical error */
    }

    make_sockaddr(&saddr, dlm_config.ci_tcp_port, &addr_len);

    log_print("connecting to %d", con->nodeid);

    /* Turn off Nagle's algorithm */
    kernel_setsockopt(sock, SOL_TCP, TCP_NODELAY, (char *)&one,
              sizeof(one));

    result = sock->ops->connect(sock, (struct sockaddr *)&saddr, addr_len,
                   O_NONBLOCK);
    if (result == -EINPROGRESS)
        result = 0;
    if (result == 0)
        goto out;

out_err:
    if (con->sock) {
        sock_release(con->sock);
        con->sock = NULL;
    } else if (sock) {
        sock_release(sock);
    }
    /*
     * Some errors are fatal and this list might need adjusting. For other
     * errors we try again until the max number of retries is reached.
     */
    if (result != -EHOSTUNREACH &&
        result != -ENETUNREACH &&
        result != -ENETDOWN && 
        result != -EINVAL &&
        result != -EPROTONOSUPPORT) {
        log_print("connect %d try %d error %d", con->nodeid,
              con->retries, result);
        mutex_unlock(&con->sock_mutex);
        msleep(1000);
        lowcomms_connect_sock(con);
        return;
    }
out:
    mutex_unlock(&con->sock_mutex);
    return;
}

static struct socket *tcp_create_listen_sock(struct connection *con,
                         struct sockaddr_storage *saddr)
{
    struct socket *sock = NULL;
    int result = 0;
    int one = 1;
    int addr_len;

    if (dlm_local_addr[0]->ss_family == AF_INET)
        addr_len = sizeof(struct sockaddr_in);
    else
        addr_len = sizeof(struct sockaddr_in6);

    /* Create a socket to communicate with */
    result = sock_create_kern(dlm_local_addr[0]->ss_family, SOCK_STREAM,
                  IPPROTO_TCP, &sock);
    if (result < 0) {
        log_print("Can't create listening comms socket");
        goto create_out;
    }

    /* Turn off Nagle's algorithm */
    kernel_setsockopt(sock, SOL_TCP, TCP_NODELAY, (char *)&one,
              sizeof(one));

    result = kernel_setsockopt(sock, SOL_SOCKET, SO_REUSEADDR,
                   (char *)&one, sizeof(one));

    if (result < 0) {
        log_print("Failed to set SO_REUSEADDR on socket: %d", result);
    }
    con->rx_action = tcp_accept_from_sock;
    con->connect_action = tcp_connect_to_sock;

    /* Bind to our port */
    make_sockaddr(saddr, dlm_config.ci_tcp_port, &addr_len);
    result = sock->ops->bind(sock, (struct sockaddr *) saddr, addr_len);
    if (result < 0) {
        log_print("Can't bind to port %d", dlm_config.ci_tcp_port);
        sock_release(sock);
        sock = NULL;
        con->sock = NULL;
        goto create_out;
    }
    result = kernel_setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE,
                 (char *)&one, sizeof(one));
    if (result < 0) {
        log_print("Set keepalive failed: %d", result);
    }

    result = sock->ops->listen(sock, 5);
    if (result < 0) {
        log_print("Can't listen on port %d", dlm_config.ci_tcp_port);
        sock_release(sock);
        sock = NULL;
        goto create_out;
    }

create_out:
    return sock;
}

/* Get local addresses */
static void init_local(void)
{
    struct sockaddr_storage sas, *addr;
    int i;

    dlm_local_count = 0;
    for (i = 0; i < DLM_MAX_ADDR_COUNT; i++) {
        if (dlm_our_addr(&sas, i))
            break;

        addr = kmalloc(sizeof(*addr), GFP_NOFS);
        if (!addr)
            break;
        memcpy(addr, &sas, sizeof(*addr));
        dlm_local_addr[dlm_local_count++] = addr;
    }
}

/* Bind to an IP address. SCTP allows multiple address so it can do
   multi-homing */
static int add_sctp_bind_addr(struct connection *sctp_con,
                  struct sockaddr_storage *addr,
                  int addr_len, int num)
{
    int result = 0;

    if (num == 1)
        result = kernel_bind(sctp_con->sock,
                     (struct sockaddr *) addr,
                     addr_len);
    else
        result = kernel_setsockopt(sctp_con->sock, SOL_SCTP,
                       SCTP_SOCKOPT_BINDX_ADD,
                       (char *)addr, addr_len);

    if (result < 0)
        log_print("Can't bind to port %d addr number %d",
              dlm_config.ci_tcp_port, num);

    return result;
}

/* Initialise SCTP socket and bind to all interfaces */
static int sctp_listen_for_all(void)
{
    struct socket *sock = NULL;
    struct sockaddr_storage localaddr;
    struct sctp_event_subscribe subscribe;
    int result = -EINVAL, num = 1, i, addr_len;
    struct connection *con = nodeid2con(0, GFP_NOFS);
    int bufsize = NEEDED_RMEM;

    if (!con)
        return -ENOMEM;

    log_print("Using SCTP for communications");

    result = sock_create_kern(dlm_local_addr[0]->ss_family, SOCK_SEQPACKET,
                  IPPROTO_SCTP, &sock);
    if (result < 0) {
        log_print("Can't create comms socket, check SCTP is loaded");
        goto out;
    }

    /* Listen for events */
    memset(&subscribe, 0, sizeof(subscribe));
    subscribe.sctp_data_io_event = 1;
    subscribe.sctp_association_event = 1;
    subscribe.sctp_send_failure_event = 1;
    subscribe.sctp_shutdown_event = 1;
    subscribe.sctp_partial_delivery_event = 1;

    result = kernel_setsockopt(sock, SOL_SOCKET, SO_RCVBUFFORCE,
                 (char *)&bufsize, sizeof(bufsize));
    if (result)
        log_print("Error increasing buffer space on socket %d", result);

    result = kernel_setsockopt(sock, SOL_SCTP, SCTP_EVENTS,
                   (char *)&subscribe, sizeof(subscribe));
    if (result < 0) {
        log_print("Failed to set SCTP_EVENTS on socket: result=%d",
              result);
        goto create_delsock;
    }

    /* Init con struct */
    sock->sk->sk_user_data = con;
    con->sock = sock;
    con->sock->sk->sk_data_ready = lowcomms_data_ready;
    con->rx_action = receive_from_sock;
    con->connect_action = sctp_init_assoc;

    /* Bind to all interfaces. */
    for (i = 0; i < dlm_local_count; i++) {
        memcpy(&localaddr, dlm_local_addr[i], sizeof(localaddr));
        make_sockaddr(&localaddr, dlm_config.ci_tcp_port, &addr_len);

        result = add_sctp_bind_addr(con, &localaddr, addr_len, num);
        if (result)
            goto create_delsock;
        ++num;
    }

    result = sock->ops->listen(sock, 5);
    if (result < 0) {
        log_print("Can't set socket listening");
        goto create_delsock;
    }

    return 0;

create_delsock:
    sock_release(sock);
    con->sock = NULL;
out:
    return result;
}

static int tcp_listen_for_all(void)
{
    struct socket *sock = NULL;
    struct connection *con = nodeid2con(0, GFP_NOFS);
    int result = -EINVAL;

    if (!con)
        return -ENOMEM;

    /* We don't support multi-homed hosts */
    if (dlm_local_addr[1] != NULL) {
        log_print("TCP protocol can't handle multi-homed hosts, "
              "try SCTP");
        return -EINVAL;
    }

    log_print("Using TCP for communications");

    sock = tcp_create_listen_sock(con, dlm_local_addr[0]);
    if (sock) {
        add_sock(sock, con);
        result = 0;
    }
    else {
        result = -EADDRINUSE;
    }

    return result;
}



static struct writequeue_entry *new_writequeue_entry(struct connection *con,
                             gfp_t allocation)
{
    struct writequeue_entry *entry;

    entry = kmalloc(sizeof(struct writequeue_entry), allocation);
    if (!entry)
        return NULL;

    entry->page = alloc_page(allocation);
    if (!entry->page) {
        kfree(entry);
        return NULL;
    }

    entry->offset = 0;
    entry->len = 0;
    entry->end = 0;
    entry->users = 0;
    entry->con = con;

    return entry;
}

void *dlm_lowcomms_get_buffer(int nodeid, int len, gfp_t allocation, char **ppc)
{
    struct connection *con;
    struct writequeue_entry *e;
    int offset = 0;
    int users = 0;

    con = nodeid2con(nodeid, allocation);
    if (!con)
        return NULL;

    spin_lock(&con->writequeue_lock);
    e = list_entry(con->writequeue.prev, struct writequeue_entry, list);
    if ((&e->list == &con->writequeue) ||
        (PAGE_CACHE_SIZE - e->end < len)) {
        e = NULL;
    } else {
        offset = e->end;
        e->end += len;
        users = e->users++;
    }
    spin_unlock(&con->writequeue_lock);

    if (e) {
    got_one:
        *ppc = page_address(e->page) + offset;
        return e;
    }

    e = new_writequeue_entry(con, allocation);
    if (e) {
        spin_lock(&con->writequeue_lock);
        offset = e->end;
        e->end += len;
        users = e->users++;
        list_add_tail(&e->list, &con->writequeue);
        spin_unlock(&con->writequeue_lock);
        goto got_one;
    }
    return NULL;
}

void dlm_lowcomms_commit_buffer(void *mh)
{
    struct writequeue_entry *e = (struct writequeue_entry *)mh;
    struct connection *con = e->con;
    int users;

    spin_lock(&con->writequeue_lock);
    users = --e->users;
    if (users)
        goto out;
    e->len = e->end - e->offset;
    spin_unlock(&con->writequeue_lock);

    if (!test_and_set_bit(CF_WRITE_PENDING, &con->flags)) {
        queue_work(send_workqueue, &con->swork);
    }
    return;

out:
    spin_unlock(&con->writequeue_lock);
    return;
}

/* Send a message */
static void send_to_sock(struct connection *con)
{
    int ret = 0;
    const int msg_flags = MSG_DONTWAIT | MSG_NOSIGNAL;
    struct writequeue_entry *e;
    int len, offset;
    int count = 0;

    mutex_lock(&con->sock_mutex);
    if (con->sock == NULL)
        goto out_connect;

    spin_lock(&con->writequeue_lock);
    for (;;) {
        e = list_entry(con->writequeue.next, struct writequeue_entry,
                   list);
        if ((struct list_head *) e == &con->writequeue)
            break;

        len = e->len;
        offset = e->offset;
        BUG_ON(len == 0 && e->users == 0);
        spin_unlock(&con->writequeue_lock);

        ret = 0;
        if (len) {
            ret = kernel_sendpage(con->sock, e->page, offset, len,
                          msg_flags);
            if (ret == -EAGAIN || ret == 0) {
                if (ret == -EAGAIN &&
                    test_bit(SOCK_ASYNC_NOSPACE, &con->sock->flags) &&
                    !test_and_set_bit(CF_APP_LIMITED, &con->flags)) {
                    /* Notify TCP that we're limited by the
                     * application window size.
                     */
                    set_bit(SOCK_NOSPACE, &con->sock->flags);
                    con->sock->sk->sk_write_pending++;
                }
                cond_resched();
                goto out;
            } else if (ret < 0)
                goto send_error;
        }

        /* Don't starve people filling buffers */
        if (++count >= MAX_SEND_MSG_COUNT) {
            cond_resched();
            count = 0;
        }

        spin_lock(&con->writequeue_lock);
        e->offset += ret;
        e->len -= ret;

        if (e->len == 0 && e->users == 0) {
            list_del(&e->list);
            free_entry(e);
        }
    }
    spin_unlock(&con->writequeue_lock);
out:
    mutex_unlock(&con->sock_mutex);
    return;

send_error:
    mutex_unlock(&con->sock_mutex);
    close_connection(con, false);
    lowcomms_connect_sock(con);
    return;

out_connect:
    mutex_unlock(&con->sock_mutex);
    if (!test_bit(CF_INIT_PENDING, &con->flags))
        lowcomms_connect_sock(con);
}

static void clean_one_writequeue(struct connection *con)
{
    struct writequeue_entry *e, *safe;

    spin_lock(&con->writequeue_lock);
    list_for_each_entry_safe(e, safe, &con->writequeue, list) {
        list_del(&e->list);
        free_entry(e);
    }
    spin_unlock(&con->writequeue_lock);
}

/* Called from recovery when it knows that a node has
   left the cluster */
int dlm_lowcomms_close(int nodeid)
{
    struct connection *con;
    struct dlm_node_addr *na;

    log_print("closing connection to node %d", nodeid);
    con = nodeid2con(nodeid, 0);
    if (con) {
        clear_bit(CF_CONNECT_PENDING, &con->flags);
        clear_bit(CF_WRITE_PENDING, &con->flags);
        set_bit(CF_CLOSE, &con->flags);
        if (cancel_work_sync(&con->swork))
            log_print("canceled swork for node %d", nodeid);
        if (cancel_work_sync(&con->rwork))
            log_print("canceled rwork for node %d", nodeid);
        clean_one_writequeue(con);
        close_connection(con, true);
    }

    spin_lock(&dlm_node_addrs_spin);
    na = find_node_addr(nodeid);
    if (na) {
        list_del(&na->list);
        while (na->addr_count--)
            kfree(na->addr[na->addr_count]);
        kfree(na);
    }
    spin_unlock(&dlm_node_addrs_spin);

    return 0;
}

/* Receive workqueue function */
static void process_recv_sockets(struct work_struct *work)
{
    struct connection *con = container_of(work, struct connection, rwork);
    int err;

    clear_bit(CF_READ_PENDING, &con->flags);
    do {
        err = con->rx_action(con);
    } while (!err);
}

/* Send workqueue function */
static void process_send_sockets(struct work_struct *work)
{
    struct connection *con = container_of(work, struct connection, swork);

    if (test_and_clear_bit(CF_CONNECT_PENDING, &con->flags)) {
        con->connect_action(con);
        set_bit(CF_WRITE_PENDING, &con->flags);
    }
    if (test_and_clear_bit(CF_WRITE_PENDING, &con->flags))
        send_to_sock(con);
}


/* Discard all entries on the write queues */
static void clean_writequeues(void)
{
    foreach_conn(clean_one_writequeue);
}

static void work_stop(void)
{
    destroy_workqueue(recv_workqueue);
    destroy_workqueue(send_workqueue);
}

static int work_start(void)
{
    recv_workqueue = alloc_workqueue("dlm_recv",
                     WQ_UNBOUND | WQ_MEM_RECLAIM, 1);
    if (!recv_workqueue) {
        log_print("can't start dlm_recv");
        return -ENOMEM;
    }

    send_workqueue = alloc_workqueue("dlm_send",
                     WQ_UNBOUND | WQ_MEM_RECLAIM, 1);
    if (!send_workqueue) {
        log_print("can't start dlm_send");
        destroy_workqueue(recv_workqueue);
        return -ENOMEM;
    }

    return 0;
}

static void stop_conn(struct connection *con)
{
    con->flags |= 0x0F;
    if (con->sock && con->sock->sk)
        con->sock->sk->sk_user_data = NULL;
}

static void free_conn(struct connection *con)
{
    close_connection(con, true);
    if (con->othercon)
        kmem_cache_free(con_cache, con->othercon);
    hlist_del(&con->list);
    kmem_cache_free(con_cache, con);
}

void dlm_lowcomms_stop(void)
{
    /* Set all the flags to prevent any
       socket activity.
    */
    mutex_lock(&connections_lock);
    dlm_allow_conn = 0;
    foreach_conn(stop_conn);
    mutex_unlock(&connections_lock);

    work_stop();

    mutex_lock(&connections_lock);
    clean_writequeues();

    foreach_conn(free_conn);

    mutex_unlock(&connections_lock);
    kmem_cache_destroy(con_cache);
}

int dlm_lowcomms_start(void)
{
    int error = -EINVAL;
    struct connection *con;
    int i;

    for (i = 0; i < CONN_HASH_SIZE; i++)
        INIT_HLIST_HEAD(&connection_hash[i]);

    init_local();
    if (!dlm_local_count) {
        error = -ENOTCONN;
        log_print("no local IP address has been set");
        goto fail;
    }

    error = -ENOMEM;
    con_cache = kmem_cache_create("dlm_conn", sizeof(struct connection),
                      __alignof__(struct connection), 0,
                      NULL);
    if (!con_cache)
        goto fail;

    error = work_start();
    if (error)
        goto fail_destroy;

    dlm_allow_conn = 1;

    /* Start listening */
    if (dlm_config.ci_protocol == 0)
        error = tcp_listen_for_all();
    else
        error = sctp_listen_for_all();
    if (error)
        goto fail_unlisten;

    return 0;

fail_unlisten:
    dlm_allow_conn = 0;
    con = nodeid2con(0,0);
    if (con) {
        close_connection(con, false);
        kmem_cache_free(con_cache, con);
    }
fail_destroy:
    kmem_cache_destroy(con_cache);
fail:
    return error;
}

void dlm_lowcomms_exit(void)
{
    struct dlm_node_addr *na, *safe;

    spin_lock(&dlm_node_addrs_spin);
    list_for_each_entry_safe(na, safe, &dlm_node_addrs, list) {
        list_del(&na->list);
        while (na->addr_count--)
            kfree(na->addr[na->addr_count]);
        kfree(na);
    }
    spin_unlock(&dlm_node_addrs_spin);
}