/* RxRPC virtual connection handler
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * 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.
 */

#include <linux/module.h>
#include <linux/net.h>
#include <linux/skbuff.h>
#include <linux/crypto.h>
#include <net/sock.h>
#include <net/af_rxrpc.h>
#include "ar-internal.h"

static void rxrpc_connection_reaper(struct work_struct *work);

LIST_HEAD(rxrpc_connections);
DEFINE_RWLOCK(rxrpc_connection_lock);
static unsigned long rxrpc_connection_timeout = 10 * 60;
static DECLARE_DELAYED_WORK(rxrpc_connection_reap, rxrpc_connection_reaper);

/*
 * allocate a new client connection bundle
 */
static struct rxrpc_conn_bundle *rxrpc_alloc_bundle(gfp_t gfp)
{
        struct rxrpc_conn_bundle *bundle;

        _enter("");

        bundle = kzalloc(sizeof(struct rxrpc_conn_bundle), gfp);
        if (bundle) {
                INIT_LIST_HEAD(&bundle->unused_conns);
                INIT_LIST_HEAD(&bundle->avail_conns);
                INIT_LIST_HEAD(&bundle->busy_conns);
                init_waitqueue_head(&bundle->chanwait);
                atomic_set(&bundle->usage, 1);
        }

        _leave(" = %p", bundle);
        return bundle;
}

/*
 * compare bundle parameters with what we're looking for
 * - return -ve, 0 or +ve
 */
static inline
int rxrpc_cmp_bundle(const struct rxrpc_conn_bundle *bundle,
                     struct key *key, __be16 service_id)
{
        return (bundle->service_id - service_id) ?:
                ((unsigned long) bundle->key - (unsigned long) key);
}

/*
 * get bundle of client connections that a client socket can make use of
 */
struct rxrpc_conn_bundle *rxrpc_get_bundle(struct rxrpc_sock *rx,
                                           struct rxrpc_transport *trans,
                                           struct key *key,
                                           __be16 service_id,
                                           gfp_t gfp)
{
        struct rxrpc_conn_bundle *bundle, *candidate;
        struct rb_node *p, *parent, **pp;

        _enter("%p{%x},%x,%hx,",
               rx, key_serial(key), trans->debug_id, ntohs(service_id));

        if (rx->trans == trans && rx->bundle) {
                atomic_inc(&rx->bundle->usage);
                return rx->bundle;
        }

        /* search the extant bundles first for one that matches the specified
         * user ID */
        spin_lock(&trans->client_lock);

        p = trans->bundles.rb_node;
        while (p) {
                bundle = rb_entry(p, struct rxrpc_conn_bundle, node);

                if (rxrpc_cmp_bundle(bundle, key, service_id) < 0)
                        p = p->rb_left;
                else if (rxrpc_cmp_bundle(bundle, key, service_id) > 0)
                        p = p->rb_right;
                else
                        goto found_extant_bundle;
        }

        spin_unlock(&trans->client_lock);

        /* not yet present - create a candidate for a new record and then
         * redo the search */
        candidate = rxrpc_alloc_bundle(gfp);
        if (!candidate) {
                _leave(" = -ENOMEM");
                return ERR_PTR(-ENOMEM);
        }

        candidate->key = key_get(key);
        candidate->service_id = service_id;

        spin_lock(&trans->client_lock);

        pp = &trans->bundles.rb_node;
        parent = NULL;
        while (*pp) {
                parent = *pp;
                bundle = rb_entry(parent, struct rxrpc_conn_bundle, node);

                if (rxrpc_cmp_bundle(bundle, key, service_id) < 0)
                        pp = &(*pp)->rb_left;
                else if (rxrpc_cmp_bundle(bundle, key, service_id) > 0)
                        pp = &(*pp)->rb_right;
                else
                        goto found_extant_second;
        }

        /* second search also failed; add the new bundle */
        bundle = candidate;
        candidate = NULL;

        rb_link_node(&bundle->node, parent, pp);
        rb_insert_color(&bundle->node, &trans->bundles);
        spin_unlock(&trans->client_lock);
        _net("BUNDLE new on trans %d", trans->debug_id);
        if (!rx->bundle && rx->sk.sk_state == RXRPC_CLIENT_CONNECTED) {
                atomic_inc(&bundle->usage);
                rx->bundle = bundle;
        }
        _leave(" = %p [new]", bundle);
        return bundle;

        /* we found the bundle in the list immediately */
found_extant_bundle:
        atomic_inc(&bundle->usage);
        spin_unlock(&trans->client_lock);
        _net("BUNDLE old on trans %d", trans->debug_id);
        if (!rx->bundle && rx->sk.sk_state == RXRPC_CLIENT_CONNECTED) {
                atomic_inc(&bundle->usage);
                rx->bundle = bundle;
        }
        _leave(" = %p [extant %d]", bundle, atomic_read(&bundle->usage));
        return bundle;

        /* we found the bundle on the second time through the list */
found_extant_second:
        atomic_inc(&bundle->usage);
        spin_unlock(&trans->client_lock);
        kfree(candidate);
        _net("BUNDLE old2 on trans %d", trans->debug_id);
        if (!rx->bundle && rx->sk.sk_state == RXRPC_CLIENT_CONNECTED) {
                atomic_inc(&bundle->usage);
                rx->bundle = bundle;
        }
        _leave(" = %p [second %d]", bundle, atomic_read(&bundle->usage));
        return bundle;
}

/*
 * release a bundle
 */
void rxrpc_put_bundle(struct rxrpc_transport *trans,
                      struct rxrpc_conn_bundle *bundle)
{
        _enter("%p,%p{%d}",trans, bundle, atomic_read(&bundle->usage));

        if (atomic_dec_and_lock(&bundle->usage, &trans->client_lock)) {
                _debug("Destroy bundle");
                rb_erase(&bundle->node, &trans->bundles);
                spin_unlock(&trans->client_lock);
                ASSERT(list_empty(&bundle->unused_conns));
                ASSERT(list_empty(&bundle->avail_conns));
                ASSERT(list_empty(&bundle->busy_conns));
                ASSERTCMP(bundle->num_conns, ==, 0);
                key_put(bundle->key);
                kfree(bundle);
        }

        _leave("");
}

/*
 * allocate a new connection
 */
static struct rxrpc_connection *rxrpc_alloc_connection(gfp_t gfp)
{
        struct rxrpc_connection *conn;

        _enter("");

        conn = kzalloc(sizeof(struct rxrpc_connection), gfp);
        if (conn) {
                INIT_WORK(&conn->processor, &rxrpc_process_connection);
                INIT_LIST_HEAD(&conn->bundle_link);
                conn->calls = RB_ROOT;
                skb_queue_head_init(&conn->rx_queue);
                rwlock_init(&conn->lock);
                spin_lock_init(&conn->state_lock);
                atomic_set(&conn->usage, 1);
                conn->debug_id = atomic_inc_return(&rxrpc_debug_id);
                conn->avail_calls = RXRPC_MAXCALLS;
                conn->size_align = 4;
                conn->header_size = sizeof(struct rxrpc_header);
        }

        _leave(" = %p{%d}", conn, conn ? conn->debug_id : 0);
        return conn;
}

/*
 * assign a connection ID to a connection and add it to the transport's
 * connection lookup tree
 * - called with transport client lock held
 */
static void rxrpc_assign_connection_id(struct rxrpc_connection *conn)
{
        struct rxrpc_connection *xconn;
        struct rb_node *parent, **p;
        __be32 epoch;
        u32 real_conn_id;

        _enter("");

        epoch = conn->epoch;

        write_lock_bh(&conn->trans->conn_lock);

        conn->trans->conn_idcounter += RXRPC_CID_INC;
        if (conn->trans->conn_idcounter < RXRPC_CID_INC)
                conn->trans->conn_idcounter = RXRPC_CID_INC;
        real_conn_id = conn->trans->conn_idcounter;

attempt_insertion:
        parent = NULL;
        p = &conn->trans->client_conns.rb_node;

        while (*p) {
                parent = *p;
                xconn = rb_entry(parent, struct rxrpc_connection, node);

                if (epoch < xconn->epoch)
                        p = &(*p)->rb_left;
                else if (epoch > xconn->epoch)
                        p = &(*p)->rb_right;
                else if (real_conn_id < xconn->real_conn_id)
                        p = &(*p)->rb_left;
                else if (real_conn_id > xconn->real_conn_id)
                        p = &(*p)->rb_right;
                else
                        goto id_exists;
        }

        /* we've found a suitable hole - arrange for this connection to occupy
         * it */
        rb_link_node(&conn->node, parent, p);
        rb_insert_color(&conn->node, &conn->trans->client_conns);

        conn->real_conn_id = real_conn_id;
        conn->cid = htonl(real_conn_id);
        write_unlock_bh(&conn->trans->conn_lock);
        _leave(" [CONNID %x CID %x]", real_conn_id, ntohl(conn->cid));
        return;

        /* we found a connection with the proposed ID - walk the tree from that
         * point looking for the next unused ID */
id_exists:
        for (;;) {
                real_conn_id += RXRPC_CID_INC;
                if (real_conn_id < RXRPC_CID_INC) {
                        real_conn_id = RXRPC_CID_INC;
                        conn->trans->conn_idcounter = real_conn_id;
                        goto attempt_insertion;
                }

                parent = rb_next(parent);
                if (!parent)
                        goto attempt_insertion;

                xconn = rb_entry(parent, struct rxrpc_connection, node);
                if (epoch < xconn->epoch ||
                    real_conn_id < xconn->real_conn_id)
                        goto attempt_insertion;
        }
}

/*
 * add a call to a connection's call-by-ID tree
 */
static void rxrpc_add_call_ID_to_conn(struct rxrpc_connection *conn,
                                      struct rxrpc_call *call)
{
        struct rxrpc_call *xcall;
        struct rb_node *parent, **p;
        __be32 call_id;

        write_lock_bh(&conn->lock);

        call_id = call->call_id;
        p = &conn->calls.rb_node;
        parent = NULL;
        while (*p) {
                parent = *p;
                xcall = rb_entry(parent, struct rxrpc_call, conn_node);

                if (call_id < xcall->call_id)
                        p = &(*p)->rb_left;
                else if (call_id > xcall->call_id)
                        p = &(*p)->rb_right;
                else
                        BUG();
        }

        rb_link_node(&call->conn_node, parent, p);
        rb_insert_color(&call->conn_node, &conn->calls);

        write_unlock_bh(&conn->lock);
}

/*
 * connect a call on an exclusive connection
 */
static int rxrpc_connect_exclusive(struct rxrpc_sock *rx,
                                   struct rxrpc_transport *trans,
                                   __be16 service_id,
                                   struct rxrpc_call *call,
                                   gfp_t gfp)
{
        struct rxrpc_connection *conn;
        int chan, ret;

        _enter("");

        conn = rx->conn;
        if (!conn) {
                /* not yet present - create a candidate for a new connection
                 * and then redo the check */
                conn = rxrpc_alloc_connection(gfp);
                if (IS_ERR(conn)) {
                        _leave(" = %ld", PTR_ERR(conn));
                        return PTR_ERR(conn);
                }

                conn->trans = trans;
                conn->bundle = NULL;
                conn->service_id = service_id;
                conn->epoch = rxrpc_epoch;
                conn->in_clientflag = 0;
                conn->out_clientflag = RXRPC_CLIENT_INITIATED;
                conn->cid = 0;
                conn->state = RXRPC_CONN_CLIENT;
                conn->avail_calls = RXRPC_MAXCALLS - 1;
                conn->security_level = rx->min_sec_level;
                conn->key = key_get(rx->key);

                ret = rxrpc_init_client_conn_security(conn);
                if (ret < 0) {
                        key_put(conn->key);
                        kfree(conn);
                        _leave(" = %d [key]", ret);
                        return ret;
                }

                write_lock_bh(&rxrpc_connection_lock);
                list_add_tail(&conn->link, &rxrpc_connections);
                write_unlock_bh(&rxrpc_connection_lock);

                spin_lock(&trans->client_lock);
                atomic_inc(&trans->usage);

                _net("CONNECT EXCL new %d on TRANS %d",
                     conn->debug_id, conn->trans->debug_id);

                rxrpc_assign_connection_id(conn);
                rx->conn = conn;
        }

        /* we've got a connection with a free channel and we can now attach the
         * call to it
         * - we're holding the transport's client lock
         * - we're holding a reference on the connection
         */
        for (chan = 0; chan < RXRPC_MAXCALLS; chan++)
                if (!conn->channels[chan])
                        goto found_channel;
        goto no_free_channels;

found_channel:
        atomic_inc(&conn->usage);
        conn->channels[chan] = call;
        call->conn = conn;
        call->channel = chan;
        call->cid = conn->cid | htonl(chan);
        call->call_id = htonl(++conn->call_counter);

        _net("CONNECT client on conn %d chan %d as call %x",
             conn->debug_id, chan, ntohl(call->call_id));

        spin_unlock(&trans->client_lock);

        rxrpc_add_call_ID_to_conn(conn, call);
        _leave(" = 0");
        return 0;

no_free_channels:
        spin_unlock(&trans->client_lock);
        _leave(" = -ENOSR");
        return -ENOSR;
}

/*
 * find a connection for a call
 * - called in process context with IRQs enabled
 */
int rxrpc_connect_call(struct rxrpc_sock *rx,
                       struct rxrpc_transport *trans,
                       struct rxrpc_conn_bundle *bundle,
                       struct rxrpc_call *call,
                       gfp_t gfp)
{
        struct rxrpc_connection *conn, *candidate;
        int chan, ret;

        DECLARE_WAITQUEUE(myself, current);

        _enter("%p,%lx,", rx, call->user_call_ID);

        if (test_bit(RXRPC_SOCK_EXCLUSIVE_CONN, &rx->flags))
                return rxrpc_connect_exclusive(rx, trans, bundle->service_id,
                                               call, gfp);

        spin_lock(&trans->client_lock);
        for (;;) {
                /* see if the bundle has a call slot available */
                if (!list_empty(&bundle->avail_conns)) {
                        _debug("avail");
                        conn = list_entry(bundle->avail_conns.next,
                                          struct rxrpc_connection,
                                          bundle_link);
                        if (--conn->avail_calls == 0)
                                list_move(&conn->bundle_link,
                                          &bundle->busy_conns);
                        ASSERTCMP(conn->avail_calls, <, RXRPC_MAXCALLS);
                        ASSERT(conn->channels[0] == NULL ||
                               conn->channels[1] == NULL ||
                               conn->channels[2] == NULL ||
                               conn->channels[3] == NULL);
                        atomic_inc(&conn->usage);
                        break;
                }

                if (!list_empty(&bundle->unused_conns)) {
                        _debug("unused");
                        conn = list_entry(bundle->unused_conns.next,
                                          struct rxrpc_connection,
                                          bundle_link);
                        ASSERTCMP(conn->avail_calls, ==, RXRPC_MAXCALLS);
                        conn->avail_calls = RXRPC_MAXCALLS - 1;
                        ASSERT(conn->channels[0] == NULL &&
                               conn->channels[1] == NULL &&
                               conn->channels[2] == NULL &&
                               conn->channels[3] == NULL);
                        atomic_inc(&conn->usage);
                        list_move(&conn->bundle_link, &bundle->avail_conns);
                        break;
                }

                /* need to allocate a new connection */
                _debug("get new conn [%d]", bundle->num_conns);

                spin_unlock(&trans->client_lock);

                if (signal_pending(current))
                        goto interrupted;

                if (bundle->num_conns >= 20) {
                        _debug("too many conns");

                        if (!(gfp & __GFP_WAIT)) {
                                _leave(" = -EAGAIN");
                                return -EAGAIN;
                        }

                        add_wait_queue(&bundle->chanwait, &myself);
                        for (;;) {
                                set_current_state(TASK_INTERRUPTIBLE);
                                if (bundle->num_conns < 20 ||
                                    !list_empty(&bundle->unused_conns) ||
                                    !list_empty(&bundle->avail_conns))
                                        break;
                                if (signal_pending(current))
                                        goto interrupted_dequeue;
                                schedule();
                        }
                        remove_wait_queue(&bundle->chanwait, &myself);
                        __set_current_state(TASK_RUNNING);
                        spin_lock(&trans->client_lock);
                        continue;
                }

                /* not yet present - create a candidate for a new connection and then
                 * redo the check */
                candidate = rxrpc_alloc_connection(gfp);
                if (IS_ERR(candidate)) {
                        _leave(" = %ld", PTR_ERR(candidate));
                        return PTR_ERR(candidate);
                }

                candidate->trans = trans;
                candidate->bundle = bundle;
                candidate->service_id = bundle->service_id;
                candidate->epoch = rxrpc_epoch;
                candidate->in_clientflag = 0;
                candidate->out_clientflag = RXRPC_CLIENT_INITIATED;
                candidate->cid = 0;
                candidate->state = RXRPC_CONN_CLIENT;
                candidate->avail_calls = RXRPC_MAXCALLS;
                candidate->security_level = rx->min_sec_level;
                candidate->key = key_get(bundle->key);

                ret = rxrpc_init_client_conn_security(candidate);
                if (ret < 0) {
                        key_put(candidate->key);
                        kfree(candidate);
                        _leave(" = %d [key]", ret);
                        return ret;
                }

                write_lock_bh(&rxrpc_connection_lock);
                list_add_tail(&candidate->link, &rxrpc_connections);
                write_unlock_bh(&rxrpc_connection_lock);

                spin_lock(&trans->client_lock);

                list_add(&candidate->bundle_link, &bundle->unused_conns);
                bundle->num_conns++;
                atomic_inc(&bundle->usage);
                atomic_inc(&trans->usage);

                _net("CONNECT new %d on TRANS %d",
                     candidate->debug_id, candidate->trans->debug_id);

                rxrpc_assign_connection_id(candidate);
                if (candidate->security)
                        candidate->security->prime_packet_security(candidate);

                /* leave the candidate lurking in zombie mode attached to the
                 * bundle until we're ready for it */
                rxrpc_put_connection(candidate);
                candidate = NULL;
        }

        /* we've got a connection with a free channel and we can now attach the
         * call to it
         * - we're holding the transport's client lock
         * - we're holding a reference on the connection
         * - we're holding a reference on the bundle
         */
        for (chan = 0; chan < RXRPC_MAXCALLS; chan++)
                if (!conn->channels[chan])
                        goto found_channel;
        ASSERT(conn->channels[0] == NULL ||
               conn->channels[1] == NULL ||
               conn->channels[2] == NULL ||
               conn->channels[3] == NULL);
        BUG();

found_channel:
        conn->channels[chan] = call;
        call->conn = conn;
        call->channel = chan;
        call->cid = conn->cid | htonl(chan);
        call->call_id = htonl(++conn->call_counter);

        _net("CONNECT client on conn %d chan %d as call %x",
             conn->debug_id, chan, ntohl(call->call_id));

        ASSERTCMP(conn->avail_calls, <, RXRPC_MAXCALLS);
        spin_unlock(&trans->client_lock);

        rxrpc_add_call_ID_to_conn(conn, call);

        _leave(" = 0");
        return 0;

interrupted_dequeue:
        remove_wait_queue(&bundle->chanwait, &myself);
        __set_current_state(TASK_RUNNING);
interrupted:
        _leave(" = -ERESTARTSYS");
        return -ERESTARTSYS;
}

/*
 * get a record of an incoming connection
 */
struct rxrpc_connection *
rxrpc_incoming_connection(struct rxrpc_transport *trans,
                          struct rxrpc_header *hdr,
                          gfp_t gfp)
{
        struct rxrpc_connection *conn, *candidate = NULL;
        struct rb_node *p, **pp;
        const char *new = "old";
        __be32 epoch;
        u32 conn_id;

        _enter("");

        ASSERT(hdr->flags & RXRPC_CLIENT_INITIATED);

        epoch = hdr->epoch;
        conn_id = ntohl(hdr->cid) & RXRPC_CIDMASK;

        /* search the connection list first */
        read_lock_bh(&trans->conn_lock);

        p = trans->server_conns.rb_node;
        while (p) {
                conn = rb_entry(p, struct rxrpc_connection, node);

                _debug("maybe %x", conn->real_conn_id);

                if (epoch < conn->epoch)
                        p = p->rb_left;
                else if (epoch > conn->epoch)
                        p = p->rb_right;
                else if (conn_id < conn->real_conn_id)
                        p = p->rb_left;
                else if (conn_id > conn->real_conn_id)
                        p = p->rb_right;
                else
                        goto found_extant_connection;
        }
        read_unlock_bh(&trans->conn_lock);

        /* not yet present - create a candidate for a new record and then
         * redo the search */
        candidate = rxrpc_alloc_connection(gfp);
        if (!candidate) {
                _leave(" = -ENOMEM");
                return ERR_PTR(-ENOMEM);
        }

        candidate->trans = trans;
        candidate->epoch = hdr->epoch;
        candidate->cid = hdr->cid & cpu_to_be32(RXRPC_CIDMASK);
        candidate->service_id = hdr->serviceId;
        candidate->security_ix = hdr->securityIndex;
        candidate->in_clientflag = RXRPC_CLIENT_INITIATED;
        candidate->out_clientflag = 0;
        candidate->real_conn_id = conn_id;
        candidate->state = RXRPC_CONN_SERVER;
        if (candidate->service_id)
                candidate->state = RXRPC_CONN_SERVER_UNSECURED;

        write_lock_bh(&trans->conn_lock);

        pp = &trans->server_conns.rb_node;
        p = NULL;
        while (*pp) {
                p = *pp;
                conn = rb_entry(p, struct rxrpc_connection, node);

                if (epoch < conn->epoch)
                        pp = &(*pp)->rb_left;
                else if (epoch > conn->epoch)
                        pp = &(*pp)->rb_right;
                else if (conn_id < conn->real_conn_id)
                        pp = &(*pp)->rb_left;
                else if (conn_id > conn->real_conn_id)
                        pp = &(*pp)->rb_right;
                else
                        goto found_extant_second;
        }

        /* we can now add the new candidate to the list */
        conn = candidate;
        candidate = NULL;
        rb_link_node(&conn->node, p, pp);
        rb_insert_color(&conn->node, &trans->server_conns);
        atomic_inc(&conn->trans->usage);

        write_unlock_bh(&trans->conn_lock);

        write_lock_bh(&rxrpc_connection_lock);
        list_add_tail(&conn->link, &rxrpc_connections);
        write_unlock_bh(&rxrpc_connection_lock);

        new = "new";

success:
        _net("CONNECTION %s %d {%x}", new, conn->debug_id, conn->real_conn_id);

        _leave(" = %p {u=%d}", conn, atomic_read(&conn->usage));
        return conn;

        /* we found the connection in the list immediately */
found_extant_connection:
        if (hdr->securityIndex != conn->security_ix) {
                read_unlock_bh(&trans->conn_lock);
                goto security_mismatch;
        }
        atomic_inc(&conn->usage);
        read_unlock_bh(&trans->conn_lock);
        goto success;

        /* we found the connection on the second time through the list */
found_extant_second:
        if (hdr->securityIndex != conn->security_ix) {
                write_unlock_bh(&trans->conn_lock);
                goto security_mismatch;
        }
        atomic_inc(&conn->usage);
        write_unlock_bh(&trans->conn_lock);
        kfree(candidate);
        goto success;

security_mismatch:
        kfree(candidate);
        _leave(" = -EKEYREJECTED");
        return ERR_PTR(-EKEYREJECTED);
}

/*
 * find a connection based on transport and RxRPC connection ID for an incoming
 * packet
 */
struct rxrpc_connection *rxrpc_find_connection(struct rxrpc_transport *trans,
                                               struct rxrpc_header *hdr)
{
        struct rxrpc_connection *conn;
        struct rb_node *p;
        __be32 epoch;
        u32 conn_id;

        _enter(",{%x,%x}", ntohl(hdr->cid), hdr->flags);

        read_lock_bh(&trans->conn_lock);

        conn_id = ntohl(hdr->cid) & RXRPC_CIDMASK;
        epoch = hdr->epoch;

        if (hdr->flags & RXRPC_CLIENT_INITIATED)
                p = trans->server_conns.rb_node;
        else
                p = trans->client_conns.rb_node;

        while (p) {
                conn = rb_entry(p, struct rxrpc_connection, node);

                _debug("maybe %x", conn->real_conn_id);

                if (epoch < conn->epoch)
                        p = p->rb_left;
                else if (epoch > conn->epoch)
                        p = p->rb_right;
                else if (conn_id < conn->real_conn_id)
                        p = p->rb_left;
                else if (conn_id > conn->real_conn_id)
                        p = p->rb_right;
                else
                        goto found;
        }

        read_unlock_bh(&trans->conn_lock);
        _leave(" = NULL");
        return NULL;

found:
        atomic_inc(&conn->usage);
        read_unlock_bh(&trans->conn_lock);
        _leave(" = %p", conn);
        return conn;
}

/*
 * release a virtual connection
 */
void rxrpc_put_connection(struct rxrpc_connection *conn)
{
        _enter("%p{u=%d,d=%d}",
               conn, atomic_read(&conn->usage), conn->debug_id);

        ASSERTCMP(atomic_read(&conn->usage), >, 0);

        conn->put_time = get_seconds();
        if (atomic_dec_and_test(&conn->usage)) {
                _debug("zombie");
                rxrpc_queue_delayed_work(&rxrpc_connection_reap, 0);
        }

        _leave("");
}

/*
 * destroy a virtual connection
 */
static void rxrpc_destroy_connection(struct rxrpc_connection *conn)
{
        _enter("%p{%d}", conn, atomic_read(&conn->usage));

        ASSERTCMP(atomic_read(&conn->usage), ==, 0);

        _net("DESTROY CONN %d", conn->debug_id);

        if (conn->bundle)
                rxrpc_put_bundle(conn->trans, conn->bundle);

        ASSERT(RB_EMPTY_ROOT(&conn->calls));
        rxrpc_purge_queue(&conn->rx_queue);

        rxrpc_clear_conn_security(conn);
        rxrpc_put_transport(conn->trans);
        kfree(conn);
        _leave("");
}

/*
 * reap dead connections
 */
void rxrpc_connection_reaper(struct work_struct *work)
{
        struct rxrpc_connection *conn, *_p;
        unsigned long now, earliest, reap_time;

        LIST_HEAD(graveyard);

        _enter("");

        now = get_seconds();
        earliest = ULONG_MAX;

        write_lock_bh(&rxrpc_connection_lock);
        list_for_each_entry_safe(conn, _p, &rxrpc_connections, link) {
                _debug("reap CONN %d { u=%d,t=%ld }",
                       conn->debug_id, atomic_read(&conn->usage),
                       (long) now - (long) conn->put_time);

                if (likely(atomic_read(&conn->usage) > 0))
                        continue;

                spin_lock(&conn->trans->client_lock);
                write_lock(&conn->trans->conn_lock);
                reap_time = conn->put_time + rxrpc_connection_timeout;

                if (atomic_read(&conn->usage) > 0) {
                        ;
                } else if (reap_time <= now) {
                        list_move_tail(&conn->link, &graveyard);
                        if (conn->out_clientflag)
                                rb_erase(&conn->node,
                                         &conn->trans->client_conns);
                        else
                                rb_erase(&conn->node,
                                         &conn->trans->server_conns);
                        if (conn->bundle) {
                                list_del_init(&conn->bundle_link);
                                conn->bundle->num_conns--;
                        }

                } else if (reap_time < earliest) {
                        earliest = reap_time;
                }

                write_unlock(&conn->trans->conn_lock);
                spin_unlock(&conn->trans->client_lock);
        }
        write_unlock_bh(&rxrpc_connection_lock);

        if (earliest != ULONG_MAX) {
                _debug("reschedule reaper %ld", (long) earliest - now);
                ASSERTCMP(earliest, >, now);
                rxrpc_queue_delayed_work(&rxrpc_connection_reap,
                                         (earliest - now) * HZ);
        }

        /* then destroy all those pulled out */
        while (!list_empty(&graveyard)) {
                conn = list_entry(graveyard.next, struct rxrpc_connection,
                                  link);
                list_del_init(&conn->link);

                ASSERTCMP(atomic_read(&conn->usage), ==, 0);
                rxrpc_destroy_connection(conn);
        }

        _leave("");
}

/*
 * preemptively destroy all the connection records rather than waiting for them
 * to time out
 */
void __exit rxrpc_destroy_all_connections(void)
{
        _enter("");

        rxrpc_connection_timeout = 0;
        cancel_delayed_work(&rxrpc_connection_reap);
        rxrpc_queue_delayed_work(&rxrpc_connection_reap, 0);

        _leave("");
}