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5a84abb09e
Signed-off-by: ZmnSCPxj jxPCSnmZ <ZmnSCPxj@protonmail.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
82 lines
2.4 KiB
C
82 lines
2.4 KiB
C
/* CC0 license (public domain) - see LICENSE file for details */
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#ifndef CCAN_CLOSEFROM_H
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#define CCAN_CLOSEFROM_H
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#include "config.h"
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#include <stdbool.h>
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#if HAVE_CLOSEFROM
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/* BSD. */
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#include <unistd.h>
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/* Solaris. */
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#include <stdlib.h>
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static inline
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bool closefrom_may_be_slow(void)
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{
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return 0;
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}
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static inline
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void closefrom_limit(unsigned int limit)
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{
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}
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#else /* !HAVE_CLOSEFROM */
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/**
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* closefrom - Close all open file descriptors, starting
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* at fromfd onwards.
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* @fromfd: the first fd to close; it and all higher file descriptors
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* will be closed.
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*
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* This is not multithread-safe: other threads in the same process
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* may or may not open new file descriptors in parallel to this call.
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* However, the expected use-case is that this will be called in a
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* child process just after fork(), meaning the child process is still
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* single-threaded.
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*/
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void closefrom_(int fromfd);
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/* In case the standard library has it, but declared in some
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* *other* header we do not know of yet, we use closefrom_ in
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* the actual name the linker sees.
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*/
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#define closefrom closefrom_
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/**
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* closefrom_may_be_slow - check if the closefrom() function could
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* potentially take a long time.
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*
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* The return value is true if closefrom() is emulated by
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* looping from fromfd to sysconf(_SC_OPEN_MAX), which can be
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* very large (possibly even INT_MAX on some systems).
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* If so, you might want to use setrlimit to limit _SC_OPEN_MAX.
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* If this returns false, then closefrom is efficient and you do not
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* need to limit the number of file descriptors.
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*
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* You can use closefrom_limit to perform the limiting based on
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* closefrom_may_be_slow.
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* This API is exposed in case you want to output to debug logs or
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* something similar.
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*/
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bool closefrom_may_be_slow(void);
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/**
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* closefrom_limit - If closefrom_may_be_slow(), lower the limit on
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* the number of file descriptors we keep open, to prevent closefrom
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* from being *too* slow.
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* @limit: 0 to use a reasonable default of 4096, or non-zero for the
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* limit you prefer.
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*
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* This function does nothing if closefrom_may_be_slow() return false.
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*
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* This function only *lowers* the limit from the hard limit set by
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* root before running this program.
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* If the limit is higher than the hard limit, then the hard limit is
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* respected.
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*/
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void closefrom_limit(unsigned int limit);
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#endif /* !HAVE_CLOSEFROM */
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#endif /* CCAN_CLOSEFROM_H */
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