// SPDX-License-Identifier: GPL-2.0-or-later
/* RxRPC virtual connection handler, common bits.
 *
 * Copyright (C) 2007, 2016 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/net.h>
#include <linux/skbuff.h>
#include "ar-internal.h"

/*
 * Time till a connection expires after last use (in seconds).
 */
unsigned int __read_mostly rxrpc_connection_expiry = 10 * 60;
unsigned int __read_mostly rxrpc_closed_conn_expiry = 10;

static void rxrpc_clean_up_connection(struct work_struct *work);
static void rxrpc_set_service_reap_timer(struct rxrpc_net *rxnet,
                                         unsigned long reap_at);

void rxrpc_poke_conn(struct rxrpc_connection *conn, enum rxrpc_conn_trace why)
{
        struct rxrpc_local *local = conn->local;
        bool busy;

        if (WARN_ON_ONCE(!local))
                return;

        spin_lock_irq(&local->lock);
        busy = !list_empty(&conn->attend_link);
        if (!busy) {
                rxrpc_get_connection(conn, why);
                list_add_tail(&conn->attend_link, &local->conn_attend_q);
        }
        spin_unlock_irq(&local->lock);
        rxrpc_wake_up_io_thread(local);
}

static void rxrpc_connection_timer(struct timer_list *timer)
{
        struct rxrpc_connection *conn =
                container_of(timer, struct rxrpc_connection, timer);

        rxrpc_poke_conn(conn, rxrpc_conn_get_poke_timer);
}

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

        _enter("");

        conn = kzalloc_obj(struct rxrpc_connection, gfp);
        if (conn) {
                INIT_LIST_HEAD(&conn->cache_link);
                timer_setup(&conn->timer, &rxrpc_connection_timer, 0);
                INIT_WORK(&conn->processor, rxrpc_process_connection);
                INIT_WORK(&conn->destructor, rxrpc_clean_up_connection);
                INIT_LIST_HEAD(&conn->proc_link);
                INIT_LIST_HEAD(&conn->link);
                INIT_LIST_HEAD(&conn->attend_link);
                mutex_init(&conn->security_lock);
                mutex_init(&conn->tx_data_alloc_lock);
                skb_queue_head_init(&conn->rx_queue);
                conn->rxnet = rxnet;
                conn->security = &rxrpc_no_security;
                rwlock_init(&conn->security_use_lock);
                spin_lock_init(&conn->state_lock);
                conn->debug_id = atomic_inc_return(&rxrpc_debug_id);
                conn->idle_timestamp = jiffies;
        }

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

/*
 * Look up a connection in the cache by protocol parameters.
 *
 * If successful, a pointer to the connection is returned, but no ref is taken.
 * NULL is returned if there is no match.
 *
 * When searching for a service call, if we find a peer but no connection, we
 * return that through *_peer in case we need to create a new service call.
 *
 * The caller must be holding the RCU read lock.
 */
struct rxrpc_connection *rxrpc_find_client_connection_rcu(struct rxrpc_local *local,
                                                          struct sockaddr_rxrpc *srx,
                                                          struct sk_buff *skb)
{
        struct rxrpc_connection *conn;
        struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
        struct rxrpc_peer *peer;

        _enter(",%x", sp->hdr.cid & RXRPC_CIDMASK);

        /* Look up client connections by connection ID alone as their
         * IDs are unique for this machine.
         */
        conn = idr_find(&local->conn_ids, sp->hdr.cid >> RXRPC_CIDSHIFT);
        if (!conn || refcount_read(&conn->ref) == 0) {
                _debug("no conn");
                goto not_found;
        }

        if (conn->proto.epoch != sp->hdr.epoch ||
            conn->local != local)
                goto not_found;

        peer = conn->peer;
        switch (srx->transport.family) {
        case AF_INET:
                if (peer->srx.transport.sin.sin_port !=
                    srx->transport.sin.sin_port)
                        goto not_found;
                break;
#ifdef CONFIG_AF_RXRPC_IPV6
        case AF_INET6:
                if (peer->srx.transport.sin6.sin6_port !=
                    srx->transport.sin6.sin6_port)
                        goto not_found;
                break;
#endif
        default:
                BUG();
        }

        _leave(" = %p", conn);
        return conn;

not_found:
        _leave(" = NULL");
        return NULL;
}

/*
 * Disconnect a call and clear any channel it occupies when that call
 * terminates.  The caller must hold the channel_lock and must release the
 * call's ref on the connection.
 */
void __rxrpc_disconnect_call(struct rxrpc_connection *conn,
                             struct rxrpc_call *call)
{
        struct rxrpc_channel *chan =
                &conn->channels[call->cid & RXRPC_CHANNELMASK];

        _enter("%d,%x", conn->debug_id, call->cid);

        if (chan->call == call) {
                /* Save the result of the call so that we can repeat it if necessary
                 * through the channel, whilst disposing of the actual call record.
                 */
                trace_rxrpc_disconnect_call(call);
                switch (call->completion) {
                case RXRPC_CALL_SUCCEEDED:
                        chan->last_seq = call->rx_highest_seq;
                        chan->last_type = RXRPC_PACKET_TYPE_ACK;
                        break;
                case RXRPC_CALL_LOCALLY_ABORTED:
                        chan->last_abort = call->abort_code;
                        chan->last_type = RXRPC_PACKET_TYPE_ABORT;
                        break;
                default:
                        chan->last_abort = RX_CALL_DEAD;
                        chan->last_type = RXRPC_PACKET_TYPE_ABORT;
                        break;
                }

                chan->last_call = chan->call_id;
                chan->call_id = chan->call_counter;
                chan->call = NULL;
        }

        _leave("");
}

/*
 * Disconnect a call and clear any channel it occupies when that call
 * terminates.
 */
void rxrpc_disconnect_call(struct rxrpc_call *call)
{
        struct rxrpc_connection *conn = call->conn;

        set_bit(RXRPC_CALL_DISCONNECTED, &call->flags);
        rxrpc_see_call(call, rxrpc_call_see_disconnected);

        call->peer->cong_ssthresh = call->cong_ssthresh;

        if (!hlist_unhashed(&call->error_link)) {
                spin_lock_irq(&call->peer->lock);
                hlist_del_init(&call->error_link);
                spin_unlock_irq(&call->peer->lock);
        }

        if (rxrpc_is_client_call(call)) {
                rxrpc_disconnect_client_call(call->bundle, call);
        } else {
                __rxrpc_disconnect_call(conn, call);
                conn->idle_timestamp = jiffies;
                if (atomic_dec_and_test(&conn->active))
                        rxrpc_set_service_reap_timer(conn->rxnet,
                                                     jiffies + rxrpc_connection_expiry * HZ);
        }

        rxrpc_put_call(call, rxrpc_call_put_io_thread);
}

/*
 * Queue a connection's work processor, getting a ref to pass to the work
 * queue.
 */
void rxrpc_queue_conn(struct rxrpc_connection *conn, enum rxrpc_conn_trace why)
{
        if (atomic_read(&conn->active) >= 0 &&
            rxrpc_queue_work(&conn->processor))
                rxrpc_see_connection(conn, why);
}

/*
 * Note the re-emergence of a connection.
 */
void rxrpc_see_connection(struct rxrpc_connection *conn,
                          enum rxrpc_conn_trace why)
{
        if (conn) {
                int r = refcount_read(&conn->ref);

                trace_rxrpc_conn(conn->debug_id, r, why);
        }
}

/*
 * Get a ref on a connection.
 */
struct rxrpc_connection *rxrpc_get_connection(struct rxrpc_connection *conn,
                                              enum rxrpc_conn_trace why)
{
        int r;

        __refcount_inc(&conn->ref, &r);
        trace_rxrpc_conn(conn->debug_id, r + 1, why);
        return conn;
}

/*
 * Try to get a ref on a connection.
 */
struct rxrpc_connection *
rxrpc_get_connection_maybe(struct rxrpc_connection *conn,
                           enum rxrpc_conn_trace why)
{
        int r;

        if (conn) {
                if (__refcount_inc_not_zero(&conn->ref, &r))
                        trace_rxrpc_conn(conn->debug_id, r + 1, why);
                else
                        conn = NULL;
        }
        return conn;
}

/*
 * Set the service connection reap timer.
 */
static void rxrpc_set_service_reap_timer(struct rxrpc_net *rxnet,
                                         unsigned long reap_at)
{
        if (rxnet->live)
                timer_reduce(&rxnet->service_conn_reap_timer, reap_at);
}

/*
 * destroy a virtual connection
 */
static void rxrpc_rcu_free_connection(struct rcu_head *rcu)
{
        struct rxrpc_connection *conn =
                container_of(rcu, struct rxrpc_connection, rcu);
        struct rxrpc_net *rxnet = conn->rxnet;

        _enter("{%d,u=%d}", conn->debug_id, refcount_read(&conn->ref));

        trace_rxrpc_conn(conn->debug_id, refcount_read(&conn->ref),
                         rxrpc_conn_free);
        kfree(conn);

        if (atomic_dec_and_test(&rxnet->nr_conns))
                wake_up_var(&rxnet->nr_conns);
}

/*
 * Clean up a dead connection.
 */
static void rxrpc_clean_up_connection(struct work_struct *work)
{
        struct rxrpc_connection *conn =
                container_of(work, struct rxrpc_connection, destructor);
        struct rxrpc_net *rxnet = conn->rxnet;

        ASSERT(!conn->channels[0].call &&
               !conn->channels[1].call &&
               !conn->channels[2].call &&
               !conn->channels[3].call);
        ASSERT(list_empty(&conn->cache_link));

        timer_delete_sync(&conn->timer);
        cancel_work_sync(&conn->processor); /* Processing may restart the timer */
        timer_delete_sync(&conn->timer);

        write_lock(&rxnet->conn_lock);
        list_del_init(&conn->proc_link);
        write_unlock(&rxnet->conn_lock);

        if (conn->pmtud_probe) {
                trace_rxrpc_pmtud_lost(conn, 0);
                conn->peer->pmtud_probing = false;
                conn->peer->pmtud_pending = true;
        }

        rxrpc_purge_queue(&conn->rx_queue);
        rxrpc_free_skb(conn->tx_response, rxrpc_skb_put_response);

        rxrpc_kill_client_conn(conn);

        conn->security->clear(conn);
        key_put(conn->key);
        rxrpc_put_bundle(conn->bundle, rxrpc_bundle_put_conn);
        rxrpc_put_peer(conn->peer, rxrpc_peer_put_conn);
        rxrpc_put_local(conn->local, rxrpc_local_put_kill_conn);

        /* Drain the Rx queue.  Note that even though we've unpublished, an
         * incoming packet could still be being added to our Rx queue, so we
         * will need to drain it again in the RCU cleanup handler.
         */
        rxrpc_purge_queue(&conn->rx_queue);

        page_frag_cache_drain(&conn->tx_data_alloc);
        call_rcu(&conn->rcu, rxrpc_rcu_free_connection);
}

/*
 * Drop a ref on a connection.
 */
void rxrpc_put_connection(struct rxrpc_connection *conn,
                          enum rxrpc_conn_trace why)
{
        unsigned int debug_id;
        bool dead;
        int r;

        if (!conn)
                return;

        debug_id = conn->debug_id;
        dead = __refcount_dec_and_test(&conn->ref, &r);
        trace_rxrpc_conn(debug_id, r - 1, why);
        if (dead) {
                timer_delete(&conn->timer);
                cancel_work(&conn->processor);

                if (in_softirq() || work_busy(&conn->processor) ||
                    timer_pending(&conn->timer))
                        /* Can't use the rxrpc workqueue as we need to cancel/flush
                         * something that may be running/waiting there.
                         */
                        schedule_work(&conn->destructor);
                else
                        rxrpc_clean_up_connection(&conn->destructor);
        }
}

/*
 * reap dead service connections
 */
void rxrpc_service_connection_reaper(struct work_struct *work)
{
        struct rxrpc_connection *conn, *_p;
        struct rxrpc_net *rxnet =
                container_of(work, struct rxrpc_net, service_conn_reaper);
        unsigned long expire_at, earliest, idle_timestamp, now;
        int active;

        LIST_HEAD(graveyard);

        _enter("");

        now = jiffies;
        earliest = now + MAX_JIFFY_OFFSET;

        write_lock(&rxnet->conn_lock);
        list_for_each_entry_safe(conn, _p, &rxnet->service_conns, link) {
                ASSERTCMP(atomic_read(&conn->active), >=, 0);
                if (likely(atomic_read(&conn->active) > 0))
                        continue;
                if (conn->state == RXRPC_CONN_SERVICE_PREALLOC)
                        continue;

                if (rxnet->live && !conn->local->dead) {
                        idle_timestamp = READ_ONCE(conn->idle_timestamp);
                        expire_at = idle_timestamp + rxrpc_connection_expiry * HZ;
                        if (conn->local->service_closed)
                                expire_at = idle_timestamp + rxrpc_closed_conn_expiry * HZ;

                        _debug("reap CONN %d { a=%d,t=%ld }",
                               conn->debug_id, atomic_read(&conn->active),
                               (long)expire_at - (long)now);

                        if (time_before(now, expire_at)) {
                                if (time_before(expire_at, earliest))
                                        earliest = expire_at;
                                continue;
                        }
                }

                /* The activity count sits at 0 whilst the conn is unused on
                 * the list; we reduce that to -1 to make the conn unavailable.
                 */
                active = 0;
                if (!atomic_try_cmpxchg(&conn->active, &active, -1))
                        continue;
                rxrpc_see_connection(conn, rxrpc_conn_see_reap_service);

                if (rxrpc_conn_is_client(conn))
                        BUG();
                else
                        rxrpc_unpublish_service_conn(conn);

                list_move_tail(&conn->link, &graveyard);
        }
        write_unlock(&rxnet->conn_lock);

        if (earliest != now + MAX_JIFFY_OFFSET) {
                _debug("reschedule reaper %ld", (long)earliest - (long)now);
                ASSERT(time_after(earliest, now));
                rxrpc_set_service_reap_timer(rxnet, earliest);
        }

        while (!list_empty(&graveyard)) {
                conn = list_entry(graveyard.next, struct rxrpc_connection,
                                  link);
                list_del_init(&conn->link);

                ASSERTCMP(atomic_read(&conn->active), ==, -1);
                rxrpc_put_connection(conn, rxrpc_conn_put_service_reaped);
        }

        _leave("");
}

/*
 * preemptively destroy all the service connection records rather than
 * waiting for them to time out
 */
void rxrpc_destroy_all_connections(struct rxrpc_net *rxnet)
{
        struct rxrpc_connection *conn, *_p;
        bool leak = false;

        _enter("");

        atomic_dec(&rxnet->nr_conns);

        timer_delete_sync(&rxnet->service_conn_reap_timer);
        rxrpc_queue_work(&rxnet->service_conn_reaper);
        flush_workqueue(rxrpc_workqueue);

        write_lock(&rxnet->conn_lock);
        list_for_each_entry_safe(conn, _p, &rxnet->service_conns, link) {
                pr_err("AF_RXRPC: Leaked conn %p {%d}\n",
                       conn, refcount_read(&conn->ref));
                leak = true;
        }
        write_unlock(&rxnet->conn_lock);
        BUG_ON(leak);

        ASSERT(list_empty(&rxnet->conn_proc_list));

        /* We need to wait for the connections to be destroyed by RCU as they
         * pin things that we still need to get rid of.
         */
        wait_var_event(&rxnet->nr_conns, !atomic_read(&rxnet->nr_conns));
        _leave("");
}