path: root/net/rxrpc/conn_client.c

// SPDX-License-Identifier: GPL-2.0-or-later
/* Client connection-specific management code.
 *
 * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * Client connections need to be cached for a little while after they've made a
 * call so as to handle retransmitted DATA packets in case the server didn't
 * receive the final ACK or terminating ABORT we sent it.
 *
 * Client connections can be in one of a number of cache states:
 *
 *  (1) INACTIVE - The connection is not held in any list and may not have been
 *      exposed to the world.  If it has been previously exposed, it was
 *      discarded from the idle list after expiring.
 *
 *  (2) WAITING - The connection is waiting for the number of client conns to
 *      drop below the maximum capacity.  Calls may be in progress upon it from
 *      when it was active and got culled.
 *
 *	The connection is on the rxrpc_waiting_client_conns list which is kept
 *	in to-be-granted order.  Culled conns with waiters go to the back of
 *	the queue just like new conns.
 *
 *  (3) ACTIVE - The connection has at least one call in progress upon it, it
 *      may freely grant available channels to new calls and calls may be
 *      waiting on it for channels to become available.
 *
 *	The connection is on the rxnet->active_client_conns list which is kept
 *	in activation order for culling purposes.
 *
 *	rxrpc_nr_active_client_conns is held incremented also.
 *
 *  (4) UPGRADE - As for ACTIVE, but only one call may be in progress and is
 *      being used to probe for service upgrade.
 *
 *  (5) CULLED - The connection got summarily culled to try and free up
 *      capacity.  Calls currently in progress on the connection are allowed to
 *      continue, but new calls will have to wait.  There can be no waiters in
 *      this state - the conn would have to go to the WAITING state instead.
 *
 *  (6) IDLE - The connection has no calls in progress upon it and must have
 *      been exposed to the world (ie. the EXPOSED flag must be set).  When it
 *      expires, the EXPOSED flag is cleared and the connection transitions to
 *      the INACTIVE state.
 *
 *	The connection is on the rxnet->idle_client_conns list which is kept in
 *	order of how soon they'll expire.
 *
 * There are flags of relevance to the cache:
 *
 *  (1) EXPOSED - The connection ID got exposed to the world.  If this flag is
 *      set, an extra ref is added to the connection preventing it from being
 *      reaped when it has no calls outstanding.  This flag is cleared and the
 *      ref dropped when a conn is discarded from the idle list.
 *
 *      This allows us to move terminal call state retransmission to the
 *      connection and to discard the call immediately we think it is done
 *      with.  It also give us a chance to reuse the connection.
 *
 *  (2) DONT_REUSE - The connection should be discarded as soon as possible and
 *      should not be reused.  This is set when an exclusive connection is used
 *      or a call ID counter overflows.
 *
 * The caching state may only be changed if the cache lock is held.
 *
 * There are two idle client connection expiry durations.  If the total number
 * of connections is below the reap threshold, we use the normal duration; if
 * it's above, we use the fast duration.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/slab.h>
#include <linux/idr.h>
#include <linux/timer.h>
#include <linux/sched/signal.h>

#include "ar-internal.h"

__read_mostly unsigned int rxrpc_max_client_connections = 1000;
__read_mostly unsigned int rxrpc_reap_client_connections = 900;
__read_mostly unsigned long rxrpc_conn_idle_client_expiry = 2 * 60 * HZ;
__read_mostly unsigned long rxrpc_conn_idle_client_fast_expiry = 2 * HZ;

/*
 * We use machine-unique IDs for our client connections.
 */
DEFINE_IDR(rxrpc_client_conn_ids);
static DEFINE_SPINLOCK(rxrpc_conn_id_lock);

static void rxrpc_cull_active_client_conns(struct rxrpc_net *);

/*
 * Get a connection ID and epoch for a client connection from the global pool.
 * The connection struct pointer is then recorded in the idr radix tree.  The
 * epoch doesn't change until the client is rebooted (or, at least, unless the
 * module is unloaded).
 */
static int rxrpc_get_client_connection_id(struct rxrpc_connection *conn,
					  gfp_t gfp)
{
	struct rxrpc_net *rxnet = conn->params.local->rxnet;
	int id;

	_enter("");

	idr_preload(gfp);
	spin_lock(&rxrpc_conn_id_lock);

	id = idr_alloc_cyclic(&rxrpc_client_conn_ids, conn,
			      1, 0x40000000, GFP_NOWAIT);
	if (id < 0)
		goto error;

	spin_unlock(&rxrpc_conn_id_lock);
	idr_preload_end();

	conn->proto.epoch = rxnet->epoch;
	conn->proto.cid = id << RXRPC_CIDSHIFT;
	set_bit(RXRPC_CONN_HAS_IDR, &conn->flags);
	_leave(" [CID %x]", conn->proto.cid);
	return 0;

error:
	spin_unlock(&rxrpc_conn_id_lock);
	idr_preload_end();
	_leave(" = %d", id);
	return id;
}

/*
 * Release a connection ID for a client connection from the global pool.
 */
static void rxrpc_put_client_connection_id(struct rxrpc_connection *conn)
{
	if (test_bit(RXRPC_CONN_HAS_IDR, &conn->flags)) {
		spin_lock(&rxrpc_conn_id_lock);
		idr_remove(&rxrpc_client_conn_ids,
			   conn->proto.cid >> RXRPC_CIDSHIFT);
		spin_unlock(&rxrpc_conn_id_lock);
	}
}

/*
 * Destroy the client connection ID tree.
 */
void rxrpc_destroy_client_conn_ids(void)
{
	struct rxrpc_connection *conn;
	int id;

	if (!idr_is_empty(&rxrpc_client_conn_ids)) {
		idr_for_each_entry(&rxrpc_client_conn_ids, conn, id) {
			pr_err("AF_RXRPC: Leaked client conn %p {%d}\n",
			       conn, atomic_read(&conn->usage));
		}
		BUG();
	}

	idr_destroy(&rxrpc_client_conn_ids);
}

/*
 * Allocate a client connection.
 */
static