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We assume accept handlers may choose to reject a connection and close it, but connAccept() callers can't distinguish between this state and other error states requiring connClose(). This makes it safe (and mandatory!) to always call connClose() if connAccept() fails, and safe for accept handlers to close connections (which will defer).
89 lines
3.2 KiB
C
89 lines
3.2 KiB
C
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/*
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* Copyright (c) 2019, Redis Labs
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* * Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* * Neither the name of Redis nor the names of its contributors may be used
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* to endorse or promote products derived from this software without
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* specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef __REDIS_CONNHELPERS_H
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#define __REDIS_CONNHELPERS_H
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#include "connection.h"
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/* These are helper functions that are common to different connection
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* implementations (currently sockets in connection.c and TLS in tls.c).
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*
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* Currently helpers implement the mechanisms for invoking connection
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* handlers and tracking connection references, to allow safe destruction
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* of connections from within a handler.
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*/
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/* Incremenet connection references.
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*
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* Inside a connection handler, we guarantee refs >= 1 so it is always
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* safe to connClose().
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*
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* In other cases where we don't want to prematurely lose the connection,
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* it can go beyond 1 as well; currently it is only done by connAccept().
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*/
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static inline void connIncrRefs(connection *conn) {
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conn->refs++;
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}
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/* Decrement connection references.
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*
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* Note that this is not intended to provide any automatic free logic!
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* callHandler() takes care of that for the common flows, and anywhere an
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* explicit connIncrRefs() is used, the caller is expected to take care of
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* that.
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*/
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static inline void connDecrRefs(connection *conn) {
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conn->refs--;
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}
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static inline int connHasRefs(connection *conn) {
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return conn->refs;
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}
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/* Helper for connection implementations to call handlers:
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* 1. Increment refs to protect the connection.
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* 2. Execute the handler (if set).
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* 3. Decrement refs and perform deferred close, if refs==0.
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*/
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static inline int callHandler(connection *conn, ConnectionCallbackFunc handler) {
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connIncrRefs(conn);
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if (handler) handler(conn);
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connDecrRefs(conn);
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if (conn->flags & CONN_FLAG_CLOSE_SCHEDULED) {
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if (!connHasRefs(conn)) connClose(conn);
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return 0;
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}
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return 1;
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}
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#endif /* __REDIS_CONNHELPERS_H */
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