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/*
* Copyright (C) 2017-2018 Canonical Ltd
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 3 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
#ifndef SNAP_CONFINE_LOCKING_H
#define SNAP_CONFINE_LOCKING_H
// Include config.h which pulls in _GNU_SOURCE which in turn allows sys/types.h
// to define O_PATH. Since locking.h is included from locking.c this is
// required to see O_PATH there.
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <stdbool.h>
#include <sys/types.h>
/**
* Obtain a flock-based, exclusive, globally scoped, lock.
*
* The actual lock is placed in "/run/snap/ns/.lock"
*
* If the lock cannot be acquired for three seconds (via
* sc_enable_sanity_timeout) then the function fails and the process dies.
*
* The return value needs to be passed to sc_unlock(), there is no need to
* check for errors as the function will die() on any problem.
**/
int sc_lock_global(void);
/**
* Obtain a flock-based, exclusive, snap-scoped, lock.
*
* The actual lock is placed in "/run/snapd/ns/$SNAP_NAME.lock"
* It should be acquired only when holding the global lock.
*
* If the lock cannot be acquired for three seconds (via
* sc_enable_sanity_timeout) then the function fails and the process dies.
*
* The return value needs to be passed to sc_unlock(), there is no need to
* check for errors as the function will die() on any problem.
**/
int sc_lock_snap(const char *snap_name);
/**
* Verify that a flock-based, exclusive, snap-scoped, lock is held.
*
* If the lock is not held the process dies. The details about the lock
* are exactly the same as for sc_lock_snap().
**/
void sc_verify_snap_lock(const char *snap_name);
/**
* Obtain a flock-based, exclusive, snap-scoped, lock.
*
* The actual lock is placed in "/run/snapd/ns/$SNAP_NAME.$UID.lock"
* It should be acquired only when holding the snap-specific lock.
*
* If the lock cannot be acquired for three seconds (via
* sc_enable_sanity_timeout) then the function fails and the process dies.
* The return value needs to be passed to sc_unlock(), there is no need to
* check for errors as the function will die() on any problem.
**/
int sc_lock_snap_user(const char *snap_name, uid_t uid);
/**
* Release a flock-based lock.
*
* All kinds of locks can be unlocked the same way. This function simply
* unlocks the lock and closes the file descriptor.
**/
void sc_unlock(int lock_fd);
/**
* Enable a sanity-check timeout.
*
* The timeout is based on good-old alarm(2) and is intended to break a
* suspended system call, such as flock, after a few seconds. The built-in
* timeout is primed for three seconds. After that any sleeping system calls
* are interrupted and a flag is set.
*
* The call should be paired with sc_disable_sanity_check_timeout() that
* disables the alarm and acts on the flag, aborting the process if the timeout
* gets exceeded.
**/
void sc_enable_sanity_timeout(void);
/**
* Disable sanity-check timeout and abort the process if it expired.
*
* This call has to be paired with sc_enable_sanity_timeout(), see the function
* description for more details.
**/
void sc_disable_sanity_timeout(void);
typedef enum sc_snap_inhibition_hint {
SC_SNAP_HINT_INHIBITED_FOR_REMOVE = 1 << 0,
} sc_snap_inhibition_hint;
/**
* sc_snap_is_inhibited returns true if a given inhibition hint is set for given snap.
* This is determined by testing the presence of a file in /var/lib/snapd/inhibit/<snap_name>.<hint>.
**/
bool sc_snap_is_inhibited(const char *snap_name, sc_snap_inhibition_hint hint);
#endif // SNAP_CONFINE_LOCKING_H
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