/* 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.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/net.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <net/af_rxrpc.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_connection_reaper(struct work_struct *work);

LIST_HEAD(rxrpc_connections);
DEFINE_RWLOCK(rxrpc_connection_lock);
static DECLARE_DELAYED_WORK(rxrpc_connection_reap, rxrpc_connection_reaper);

/*
 * 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) {
		spin_lock_init(&conn->channel_lock);
		init_waitqueue_head(&conn->channel_wq);
		INIT_WORK(&conn->processor, &rxrpc_process_connection);
		INIT_LIST_HEAD(&conn->link);
		skb_queue_head_init(&conn->rx_queue);
		conn->security = &rxrpc_no_security;
		spin_lock_init(&conn->state_lock);
		/* We maintain an extra ref on the connection whilst it is
		 * on the rxrpc_connections list.
		 */
		atomic_set(&conn->usage, 2);
		conn->debug_id = atomic_inc_return(&rxrpc_debug_id);
		atomic_set(&conn->avail_chans, RXRPC_MAXCALLS);
		conn->size_align = 4;
		conn->header_size = sizeof(struct rxrpc_wire_header);
	}

	_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;
		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_call *call)
{
	struct rxrpc_connection *conn = call->conn;
	struct rxrpc_channel *chan = &conn->channels[call->channel];

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

	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.
		 */
		chan->last_result = call->local_abort;
		smp_wmb();
		chan->last_call = chan->call_id;
		chan->call_id = chan->call_counter;

		rcu_assign_pointer(chan->call, NULL);
		atomic_inc(&conn->avail_chans);
		wake_up(&conn->channel_wq);
	}

	_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;

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

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

/*
 * release a virtual connection
 */
void rxrpc_put_connection(struct rxrpc_connection *conn)
{
	if (!conn)
		return;

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

	ASSERTCMP(atomic_read(&conn->usage), >, 1);

	conn->put_time = ktime_get_seconds();
	if (atomic_dec_return(&conn->usage) == 1) {
		_debug("zombie");
		rxrpc_queue_delayed_work(&rxrpc_connection_reap, 0);
	}

	_leave("");
}

/*
 * 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 connections
 */
static void rxrpc_connection_reaper(struct work_struct *work)
{
	struct rxrpc_connection *conn, *_p;
	unsigned long reap_older_than, earliest, put_time, now;

	LIST_HEAD(graveyard);

	_enter("");

	now = ktime_get_seconds();
	reap_older_than =  now - rxrpc_connection_expiry;
	earliest = ULONG_MAX;

	write_lock(&rxrpc_connection_lock);
	list_for_each_entry_safe(conn, _p, &rxrpc_connections, link) {
		ASSERTCMP(atomic_read(&conn->usage), >, 0);
		if (likely(atomic_read(&conn->usage) > 1))
			continue;

		put_time = READ_ONCE(conn->put_time);
		if (time_after(put_time, reap_older_than)) {
			if (time_before(put_time, earliest))
				earliest = put_time;
			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))
			rxrpc_unpublish_client_conn(conn);
		else
			rxrpc_unpublish_service_conn(conn);

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

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

		ASSERTCMP(atomic_read(&conn->usage), ==, 0);
		skb_queue_purge(&conn->rx_queue);
		call_rcu(&conn->rcu, rxrpc_destroy_connection);
	}

	_leave("");
}

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

	_enter("");

	rxrpc_connection_expiry = 0;
	cancel_delayed_work(&rxrpc_connection_reap);
	rxrpc_queue_delayed_work(&rxrpc_connection_reap, 0);
	flush_workqueue(rxrpc_workqueue);

	write_lock(&rxrpc_connection_lock);
	list_for_each_entry_safe(conn, _p, &rxrpc_connections, link) {
		pr_err("AF_RXRPC: Leaked conn %p {%d}\n",
		       conn, atomic_read(&conn->usage));
		leak = true;
	}
	write_unlock(&rxrpc_connection_lock);
	BUG_ON(leak);

	/* Make sure the local and peer records pinned by any dying connections
	 * are released.
	 */
	rcu_barrier();
	rxrpc_destroy_client_conn_ids();

	_leave("");
}