9c30d4c2f8
When sesman used a standard TCP socket, we were guaranteed only one copy of sesman could run on on address, as standard TCP listening rules enforced this. This isn't the case with Unix Domain sockets. This module implements a locking mechanism for a UDS which emulates the standard TCP socket behaviour.
60 lines
1.9 KiB
C
60 lines
1.9 KiB
C
/**
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* xrdp: A Remote Desktop Protocol server.
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*
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* Copyright (C) 2022 Matt Burt, all xrdp contributors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/**
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*
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* @file lock_uds.h
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* @brief Providing a locking facility for Unix Domain Sockets
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* @author Matt Burt
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*
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* It is difficult for a server to determine whether a socket it wishes
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* to listen on is already active or not. The purpose of this module is to
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* provide a locking facility which can be used as a proxy for this.
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*/
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#ifndef LOCK_UDS_H
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#define LOCK_UDS_H
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struct lock_uds;
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/**
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* Take out a lock for the specified Unix Domain socket
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* @param sockname Name of socket. Must start with a '/'
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* @return A struct lock_uds instance if the lock was successfully acquired.
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*
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* A NULL return may indicate a lack of memory, or that another
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* process has the lock.
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*
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* A file is created in the same directory as the socket. The name
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* of the file is ".${basename}.lock", where basename is the base name
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* of the socket. THE file is removed when the lock is relinquished. */
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struct lock_uds *
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lock_uds(const char *sockname);
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/**
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* Relinquish a lock on the specified Unix Domain Socket.
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* @param lock to relinquish
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*
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* If the process which has originally taken out the lock forks, this
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* routine should be called from the child process to prevent the lock
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* inadvertently being passed to the child. */
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void
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unlock_uds(struct lock_uds *lock);
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#endif // LOCK_UDS_H
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