/* RxRPC virtual connection handler, common bits.
 *
 * Copyright (C) 2007, 2016 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.
 */

#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 rxrpc_connection_expiry = 10 * 60;

static void rxrpc_destroy_connection(struct rcu_head *);

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

        _enter("");

        conn = kzalloc(sizeof(struct rxrpc_connection), gfp);
        if (conn) {
                INIT_LIST_HEAD(&conn->cache_link);
                spin_lock_init(&conn->channel_lock);
                INIT_LIST_HEAD(&conn->waiting_calls);
                INIT_WORK(&conn->processor, &rxrpc_process_connection);
                INIT_LIST_HEAD(&conn->proc_link);
                INIT_LIST_HEAD(&conn->link);
                skb_queue_head_init(&conn->rx_queue);
                conn->security = &rxrpc_no_security;
                spin_lock_init(&conn->state_lock);
                conn->debug_id = atomic_inc_return(&rxrpc_debug_id);
                conn->size_align = 4;
                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.
 *
 * The caller must be holding the RCU read lock.
 */
struct rxrpc_connection *rxrpc_find_connection_rcu(struct rxrpc_local *local,
                                                   struct sk_buff *skb)
{
        struct rxrpc_connection *conn;
        struct rxrpc_conn_proto k;
        struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
        struct sockaddr_rxrpc srx;
        struct rxrpc_peer *peer;

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

        if (rxrpc_extract_addr_from_skb(&srx, skb) < 0)
                goto not_found;

        k.epoch = sp->hdr.epoch;
        k.cid   = sp->hdr.cid & RXRPC_CIDMASK;

        /* We may have to handle mixing IPv4 and IPv6 */
        if (srx.transport.family != local->srx.transport.family) {
                pr_warn_ratelimited("AF_RXRPC: Protocol mismatch %u not %u\n",
                                    srx.transport.family,
                                    local->srx.transport.family);
                goto not_found;
        }

        k.epoch = sp->hdr.epoch;
        k.cid   = sp->hdr.cid & RXRPC_CIDMASK;

        if (sp->hdr.flags & RXRPC_CLIENT_INITIATED) {
                /* We need to look up service connections by the full protocol
                 * parameter set.  We look up the peer first as an intermediate
                 * step and then the connection from the peer's tree.
                 */
                peer = rxrpc_lookup_peer_rcu(local, &srx);
                if (!peer)
                        goto not_found;
                conn = rxrpc_find_service_conn_rcu(peer, skb);
                if (!conn || atomic_read(&conn->usage) == 0)
                        goto not_found;
                _leave(" = %p", conn);
                return conn;
        } else {
                /* Look up client connections by connection ID alone as their
                 * IDs are unique for this machine.
                 */
                conn = idr_find(&rxrpc_client_conn_ids,
                                sp->hdr.cid >> RXRPC_CIDSHIFT);
                if (!conn || atomic_read(&conn->usage) == 0) {
                        _debug("no conn");
                        goto not_found;
                }

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

                peer = conn->params.peer;
                switch (srx.transport.family) {
                case AF_INET:
                        if (peer->srx.transport.sin.sin_port !=
                            srx.transport.sin.sin_port ||
                            peer->srx.transport.sin.sin_addr.s_addr !=
                            srx.transport.sin.sin_addr.s_addr)
                                goto not_found;
                        break;
#ifdef CONFIG_AF_RXRPC_IPV6
                case AF_INET6:
                        if (peer->srx.transport.sin6.sin6_port !=
                            srx.transport.sin6.sin6_port ||
                            memcmp(&peer->srx.transport.sin6.sin6_addr,
                                   &srx.transport.sin6.sin6_addr,
                                   sizeof(struct in6_addr)) != 0)
                                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 (rcu_access_pointer(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);
                if (call->abort_code) {
                        chan->last_abort = call->abort_code;
                        chan->last_type = RXRPC_PACKET_TYPE_ABORT;
                } else {
                        chan->last_seq = call->rx_hard_ack;
                        chan->last_type = RXRPC_PACKET_TYPE_ACK;
                }
                /* Sync with rxrpc_conn_retransmit(). */
                smp_wmb();
                chan->last_call = chan->call_id;
                chan->call_id = chan->call_counter;

                rcu_assign_pointer(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;

        call->peer->cong_cwnd = call->cong_cwnd;

        spin_lock_bh(&conn->params.peer->lock);
        hlist_del_init(&call->error_link);
        spin_unlock_bh(&conn->params.peer->lock);

        if (rxrpc_is_client_call(call))
                return rxrpc_disconnect_client_call(call);

        spin_lock(&conn->channel_lock);
        __rxrpc_disconnect_call(conn, call);
        spin_unlock(&conn->channel_lock);

        call->conn = NULL;
        conn->idle_timestamp = jiffies;
        rxrpc_put_connection(conn);
}

/*
 * Kill off a connection.
 */
void rxrpc_kill_connection(struct rxrpc_connection *conn)
{
        struct rxrpc_net *rxnet = conn->params.local->rxnet;

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

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

        /* 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);

        /* Leave final destruction to RCU.  The connection processor work item
         * must carry a ref on the connection to prevent us getting here whilst
         * it is queued or running.
         */
        call_rcu(&conn->rcu, rxrpc_destroy_connection);
}

/*
 * Queue a connection's work processor, getting a ref to pass to the work
 * queue.
 */
bool rxrpc_queue_conn(struct rxrpc_connection *conn)
{
        const void *here = __builtin_return_address(0);
        int n = __atomic_add_unless(&conn->usage, 1, 0);
        if (n == 0)
                return false;
        if (rxrpc_queue_work(&conn->processor))
                trace_rxrpc_conn(conn, rxrpc_conn_queued, n + 1, here);
        else
                rxrpc_put_connection(conn);
        return true;
}

/*
 * Note the re-emergence of a connection.
 */
void rxrpc_see_connection(struct rxrpc_connection *conn)
{
        const void *here = __builtin_return_address(0);
        if (conn) {
                int n = atomic_read(&conn->usage);

                trace_rxrpc_conn(conn, rxrpc_conn_seen, n, here);
        }
}

/*
 * Get a ref on a connection.
 */
void rxrpc_get_connection(struct rxrpc_connection *conn)
{
        const void *here = __builtin_return_address(0);
        int n = atomic_inc_return(&conn->usage);

        trace_rxrpc_conn(conn, rxrpc_conn_got, n, here);
}

/*
 * Try to get a ref on a connection.
 */
struct rxrpc_connection *
rxrpc_get_connection_maybe(struct rxrpc_connection *conn)
{
        const void *here = __builtin_return_address(0);

        if (conn) {
                int n = __atomic_add_unless(&conn->usage, 1, 0);
                if (n > 0)
                        trace_rxrpc_conn(conn, rxrpc_conn_got, n + 1, here);
                else
                        conn = NULL;
        }
        return conn;
}

/*
 * Release a service connection
 */
void rxrpc_put_service_conn(struct rxrpc_connection *conn)
{
        struct rxrpc_net *rxnet;
        const void *here = __builtin_return_address(0);
        int n;

        n = atomic_dec_return(&conn->usage);
        trace_rxrpc_conn(conn, rxrpc_conn_put_service, n, here);
        ASSERTCMP(n, >=, 0);
        if (n == 0) {
                rxnet = conn->params.local->rxnet;
                rxrpc_queue_delayed_work(&rxnet->service_conn_reaper, 0);
        }
}

/*
 * destroy a virtual connection
 */
static void rxrpc_destroy_connection(struct rcu_head *rcu)
{
        struct rxrpc_connection *conn =
                container_of(rcu, struct rxrpc_connection, rcu);

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

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

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

        rxrpc_purge_queue(&conn->rx_queue);

        conn->security->clear(conn);
        key_put(conn->params.key);
        key_put(conn->server_key);
        rxrpc_put_peer(conn->params.peer);
        rxrpc_put_local(conn->params.local);

        kfree(conn);
        _leave("");
}

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

        LIST_HEAD(graveyard);

        _enter("");

        now = jiffies;
        reap_older_than = now - rxrpc_connection_expiry * HZ;
        earliest = ULONG_MAX;

        write_lock(&rxnet->conn_lock);
        list_for_each_entry_safe(conn, _p, &rxnet->service_conns, link) {
                ASSERTCMP(atomic_read(&conn->usage), >, 0);
                if (likely(atomic_read(&conn->usage) > 1))
                        continue;
                if (conn->state == RXRPC_CONN_SERVICE_PREALLOC)
                        continue;

                idle_timestamp = READ_ONCE(conn->idle_timestamp);
                _debug("reap CONN %d { u=%d,t=%ld }",
                       conn->debug_id, atomic_read(&conn->usage),
                       (long)reap_older_than - (long)idle_timestamp);

                if (time_after(idle_timestamp, reap_older_than)) {
                        if (time_before(idle_timestamp, earliest))
                                earliest = idle_timestamp;
                        continue;
                }

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

                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 != ULONG_MAX) {
                _debug("reschedule reaper %ld", (long) earliest - now);
                ASSERT(time_after(earliest, now));
                rxrpc_queue_delayed_work(&rxnet->client_conn_reaper,
                                         earliest - now);
        }

        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_kill_connection(conn);
        }

        _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("");

        rxrpc_destroy_all_client_connections(rxnet);

        rxrpc_connection_expiry = 0;
        cancel_delayed_work(&rxnet->client_conn_reaper);
        rxrpc_queue_delayed_work(&rxnet->client_conn_reaper, 0);
        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, atomic_read(&conn->usage));
                leak = true;
        }
        write_unlock(&rxnet->conn_lock);
        BUG_ON(leak);

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

        _leave("");
}