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authorMattias Andrée <maandree@member.fsf.org>2015-12-28 15:07:11 +0100
committerMattias Andrée <maandree@member.fsf.org>2015-12-28 15:07:11 +0100
commitae79d159182044ad450f6c189c231f7ddbbdc918 (patch)
tree0bfe787fdae24a298ca6b8c640074f324d1b2417 /src
parentfix errors (diff)
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daemonise: support keeping arbitrary fd:s open
Signed-off-by: Mattias Andrée <maandree@member.fsf.org>
Diffstat (limited to 'src')
-rw-r--r--src/unistd/daemonise.c103
1 files changed, 96 insertions, 7 deletions
diff --git a/src/unistd/daemonise.c b/src/unistd/daemonise.c
index 7b0bc56..e61b72f 100644
--- a/src/unistd/daemonise.c
+++ b/src/unistd/daemonise.c
@@ -24,6 +24,8 @@
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
+#include <stdarg.h>
+#include <assert.h>
#include <sys/stat.h>
#include <sys/resource.h>
@@ -42,6 +44,41 @@ static char* __pidfile = NULL;
/**
+ * Wrapper for `dup` create a new file descriptor
+ * with a number not less than 3.
+ *
+ * @param old The file descriptor to duplicate.
+ * @return The new file descriptor, -1 on error.
+ *
+ * @throws Any error specified for dup(3).
+ */
+static int dup_at_least_3(int old)
+{
+ int intermediary[] = { -1, -1, -1 };
+ int i, saved_errno;
+
+ while (old < 3)
+ {
+ if (old = dup(old), old == -1)
+ goto fail;
+ assert(i < 3);
+ if (i >= 3)
+ abort();
+ intermediary[i++] = old;
+ }
+
+ fail:
+ saved_errno = errno;
+ if (intermediary[0] >= 0) close(intermediary[0]);
+ if (intermediary[1] >= 0) close(intermediary[1]);
+ if (intermediary[2] >= 0) close(intermediary[2]);
+ errno = saved_errno;
+ return old;
+}
+
+
+
+/**
* Daemonise the process. This means to:
*
* - close all file descritors except for those to
@@ -122,25 +159,40 @@ static char* __pidfile = NULL;
* - `DAEMONISE_CLOSE_STDERR`
* - `DAEMONISE_KEEP_STDIN`
* - `DAEMONISE_KEEP_STDOUT`
+ * - `DAEMONISE_KEEP_FDS`
+ * @parma ... Enabled if `DAEMONISE_KEEP_FDS` is used,
+ * do not add anything if `DAEMONISE_KEEP_FDS`
+ * is unused. This is a `-1`-terminated list
+ * of file descritors to keep open. 0, 1, and 2
+ * are implied by `DAEMONISE_KEEP_STDIN`,
+ * `DAEMONISE_KEEP_STDOUT`, and `DAEMONISE_KEEP_STDERR`,
+ * respectively. All arguments are of type `int`.
* @return Zero on success, -1 on error.
*
* @throws EEXIST The PID file already exists on the system.
* Unless your daemon supervisor removs old
* PID files, this could mean that the daemon
* has exited without removing the PID file.
+ * @throws EINVAL `flags` contains an unsupported bit, both
+ * `DAEMONISE_KEEP_STDERR` and `DAEMONISE_CLOSE_STDERR`
+ * are set, or both `DAEMONISE_CLOSE_STDERR` and
+ * `DAEMONISE_KEEP_FDS` are set whilst `2` is
+ * in the list of file descriptor not to close.
* @throws Any error specified for signal(3).
* @throws Any error specified for sigemptyset(3).
* @throws Any error specified for sigprocmask(3).
* @throws Any error specified for chdir(3).
* @throws Any error specified for pipe(3).
+ * @throws Any error specified for dup(3).
* @throws Any error specified for dup2(3).
* @throws Any error specified for fork(3).
* @throws Any error specified for setsid(3).
* @throws Any error specified for open(3).
+ * @throws Any error specified for malloc(3).
*
* @since Always.
*/
-int daemonise(const char* name, int flags)
+int daemonise(const char* name, int flags, ...)
{
#define t(...) do { if (__VA_ARGS__) goto fail; } while (0)
@@ -151,18 +203,52 @@ int daemonise(const char* name, int flags)
char** w;
char* run;
int i, closeerr, fd = -1;
+ char* keep = NULL;
+ int keepmax = 0;
pid_t pid;
+ va_list args;
int saved_errno;
/* Validate flags. */
- if (flags & ~1023)
+ if (flags & ~2047)
return errno = EINVAL, -1;
if (flags & DAEMONISE_KEEP_STDERR)
if (flags & DAEMONISE_CLOSE_STDERR)
return errno = EINVAL, -1;
+ /* Find out which file descriptors not too close. */
+ if ((flags & DAEMONISE_KEEP_FDS) == 0)
+ {
+ va_start(args, flags);
+ while (va_arg(args, int) >= 0)
+ if ((fd > 2) && (keepmax < fd))
+ keepmax = fd;
+ va_end(args);
+ keep = calloc(keepmax + 1, sizeof(char));
+ t (keep == NULL);
+ va_start(args, flags);
+ while ((fd = va_arg(args, int)) >= 0)
+ switch (fd)
+ {
+ case 0: flags |= DAEMONISE_KEEP_STDIN; break;
+ case 1: flags |= DAEMONISE_KEEP_STDOUT; break;
+ case 2: flags |= DAEMONISE_KEEP_STDERR;
+ if (flags & DAEMONISE_CLOSE_STDERR)
+ return free(keep), errno = EINVAL, -1;
+ break;
+ default:
+ keep[fd] = 1;
+ break;
+ }
+ va_end(args);
+ fd = -1;
+ }
+ /* We assume that the maximum file descriptor is not extremely large.
+ * We also assume the number of file descriptors too keep is very small,
+ * but this does not affect us. */
+
/* Close all files except stdin, stdout, and stderr. */
if ((flags & DAEMONISE_NO_CLOSE) == 0)
{
@@ -171,8 +257,10 @@ int daemonise(const char* name, int flags)
for (i = 3; (rlim_t)i < rlimit.rlim_cur; i++)
/* File descriptors with numbers above and including
* `rlimit.rlim_cur` cannot be created. They cause EBADF. */
- close(i);
+ if ((keep == NULL) || (keep[i] == 0))
+ close(i);
}
+ free(keep), keep = NULL;
/* Reset all signal handlers. */
if ((flags & DAEMONISE_NO_SIG_DFL) == 0)
@@ -205,12 +293,12 @@ int daemonise(const char* name, int flags)
/* Create a channel for letting the original process know when to exit. */
if (pipe(pipe_rw))
t ((pipe_rw[0] = pipe_rw[1] = -1));
- t (dup2(pipe_rw[0], 10) == -1);
+ t (fd = dup_at_least_3(pipe_rw[0]), fd == -1);
close(pipe_rw[0]);
- pipe_rw[0] = 10;
- t (dup2(pipe_rw[1], 11) == -1);
+ pipe_rw[0] = fd;
+ t (fd = dup_at_least_3(pipe_rw[1]), fd == -1);
close(pipe_rw[1]);
- pipe_rw[1] = 11;
+ pipe_rw[1] = fd;
/* Become a background process. */
t (pid = fork(), pid == -1);
@@ -289,6 +377,7 @@ int daemonise(const char* name, int flags)
if (pipe_rw[0] >= 0) close(pipe_rw[0]);
if (pipe_rw[1] >= 0) close(pipe_rw[1]);
if (fd >= 0) close(fd);
+ free(keep);
errno = saved_errno;
return -1;
}