/*
* close_all_beyond()
*
* Close all file descriptors after the given keep_fd, which is the
* highest fd to keep open. See
*
* http://stackoverflow.com/questions/899038/getting-the-highest-allocated-file-descriptor
*/
void
close_all_beyond(
int keep_fd
)
{
# ifdef HAVE_CLOSEFROM
closefrom(keep_fd + 1);
# elif defined(F_CLOSEM)
/*
* From 'Writing Reliable AIX Daemons,' SG24-4946-00,
* by Eric Agar (saves us from doing 32767 system
* calls)
*/
if (fcntl(keep_fd + 1, F_CLOSEM, 0) == -1)
msyslog(LOG_ERR, "F_CLOSEM(%d): %m", keep_fd + 1);
# else /* !HAVE_CLOSEFROM && !F_CLOSEM follows */
int fd;
int max_fd;
/* includes POSIX case */
max_fd = GETDTABLESIZE();
for (fd = keep_fd + 1; fd < max_fd; fd++)
close(fd);
# endif /* !HAVE_CLOSEFROM && !F_CLOSEM */
}
/*
* on Unix systems the stdio library typically
* makes use of file descriptors in the lower
* integer range. stdio usually will make use
* of the file descriptors in the range of
* [0..FOPEN_MAX)
* in order to keep this range clean, for socket
* file descriptors we attempt to move them above
* FOPEN_MAX. This is not as easy as it sounds as
* FOPEN_MAX changes from implementation to implementation
* and may exceed to current file decriptor limits.
* We are using following strategy:
* - keep a current socket fd boundary initialized with
* max(0, min(GETDTABLESIZE() - FD_CHUNK, FOPEN_MAX))
* - attempt to move the descriptor to the boundary or
* above.
* - if that fails and boundary > 0 set boundary
* to min(0, socket_fd_boundary - FD_CHUNK)
* -> retry
* if failure and boundary == 0 return old fd
* - on success close old fd return new fd
*
* effects:
* - fds will be moved above the socket fd boundary
* if at all possible.
* - the socket boundary will be reduced until
* allocation is possible or 0 is reached - at this
* point the algrithm will be disabled
*/
SOCKET
move_fd(
SOCKET fd
)
{
#if !defined(SYS_WINNT) && defined(F_DUPFD)
#ifndef FD_CHUNK
#define FD_CHUNK 10
#endif
#ifndef FOPEN_MAX
#define FOPEN_MAX 20
#endif
/*
* number of fds we would like to have for
* stdio FILE* available.
* we can pick a "low" number as our use of
* FILE* is limited to log files and temporarily
* to data and config files. Except for log files
* we don't keep the other FILE* open beyond the
* scope of the function that opened it.
*/
#ifndef FD_PREFERRED_SOCKBOUNDARY
#define FD_PREFERRED_SOCKBOUNDARY 48
#endif
static SOCKET socket_boundary = -1;
SOCKET newfd;
NTP_REQUIRE((int)fd >= 0);
/*
* check whether boundary has be set up
* already
*/
if (socket_boundary == -1) {
socket_boundary = max(0, min(GETDTABLESIZE() - FD_CHUNK,
min(FOPEN_MAX, FD_PREFERRED_SOCKBOUNDARY)));
TRACE(1, ("move_fd: estimated max descriptors: %d, "
"initial socket boundary: %d\n",
GETDTABLESIZE(), socket_boundary));
}
/*
* Leave a space for stdio to work in. potentially moving the
* socket_boundary lower until allocation succeeds.
*/
do {
if (fd >= 0 && fd < socket_boundary) {
/* inside reserved range: attempt to move fd */
newfd = fcntl(fd, F_DUPFD, socket_boundary);
if (newfd != -1) {
/* success: drop the old one - return the new one */
close(fd);
return newfd;
}
} else {
/* outside reserved range: no work - return the original one */
return fd;
}
socket_boundary = max(0, socket_boundary - FD_CHUNK);
TRACE(1, ("move_fd: selecting new socket boundary: %d\n",
socket_boundary));
} while (socket_boundary > 0);
#else
NTP_REQUIRE((int)fd >= 0);
#endif /* !defined(SYS_WINNT) && defined(F_DUPFD) */
return fd;
}