1
2/*
3 * Copyright (c) 2019, Redis Labs
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions are met:
8 *
9 * * Redistributions of source code must retain the above copyright notice,
10 * this list of conditions and the following disclaimer.
11 * * Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 * * Neither the name of Redis nor the names of its contributors may be used
15 * to endorse or promote products derived from this software without
16 * specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
19 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
22 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
23 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
24 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
25 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
26 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
27 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
28 * POSSIBILITY OF SUCH DAMAGE.
29 */
30
31#ifndef __REDIS_CONNHELPERS_H
32#define __REDIS_CONNHELPERS_H
33
34#include "connection.h"
35
36/* These are helper functions that are common to different connection
37 * implementations (currently sockets in connection.c and TLS in tls.c).
38 *
39 * Currently helpers implement the mechanisms for invoking connection
40 * handlers and tracking connection references, to allow safe destruction
41 * of connections from within a handler.
42 */
43
44/* Increment connection references.
45 *
46 * Inside a connection handler, we guarantee refs >= 1 so it is always
47 * safe to connClose().
48 *
49 * In other cases where we don't want to prematurely lose the connection,
50 * it can go beyond 1 as well; currently it is only done by connAccept().
51 */
52static inline void connIncrRefs(connection *conn) {
53 conn->refs++;
54}
55
56/* Decrement connection references.
57 *
58 * Note that this is not intended to provide any automatic free logic!
59 * callHandler() takes care of that for the common flows, and anywhere an
60 * explicit connIncrRefs() is used, the caller is expected to take care of
61 * that.
62 */
63
64static inline void connDecrRefs(connection *conn) {
65 conn->refs--;
66}
67
68static inline int connHasRefs(connection *conn) {
69 return conn->refs;
70}
71
72/* Helper for connection implementations to call handlers:
73 * 1. Increment refs to protect the connection.
74 * 2. Execute the handler (if set).
75 * 3. Decrement refs and perform deferred close, if refs==0.
76 */
77static inline int callHandler(connection *conn, ConnectionCallbackFunc handler) {
78 connIncrRefs(conn);
79 if (handler) handler(conn);
80 connDecrRefs(conn);
81 if (conn->flags & CONN_FLAG_CLOSE_SCHEDULED) {
82 if (!connHasRefs(conn)) connClose(conn);
83 return 0;
84 }
85 return 1;
86}
87
88#endif /* __REDIS_CONNHELPERS_H */
89