mirror of
https://github.com/freebsd/freebsd-src
synced 2024-10-14 12:23:58 +00:00
daemon: use kqueue for all events
Refactor daemon to use kqueue/kevent instead of signals.
This changes allows to simplify the code in several ways:
- the execution flow is now linear, no async events.
- several variables became redundant and got removed.
- all event handling is now concentrated inside of the event loop, which
makes code reading and comprehension easier.
- new kqueuex(2) call is used for CLOEXEC, but maintained closing the
kq fd prior to execve() to ease later MFC
No UX/API changes are intended.
Reviewed by: kevans
Pull Request: https://github.com/freebsd/freebsd-src/pull/701
(cherry picked from commit 8935a39932
)
This commit is contained in:
parent
06c9bece28
commit
b64f569e5c
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@ -32,6 +32,7 @@
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#include <sys/cdefs.h>
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#include <sys/param.h>
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#include <sys/event.h>
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#include <sys/mman.h>
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#include <sys/wait.h>
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@ -57,11 +58,14 @@
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#define LBUF_SIZE 4096
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enum daemon_mode {
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MODE_DAEMON = 0, /* simply daemonize, no supervision */
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MODE_SUPERVISE, /* initial supervision state */
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MODE_TERMINATING, /* user requested termination */
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MODE_NOCHILD, /* child is terminated, final state of the event loop */
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};
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struct daemon_state {
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sigset_t mask_orig;
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sigset_t mask_read;
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sigset_t mask_term;
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sigset_t mask_susp;
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int pipe_fd[2];
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char **argv;
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const char *child_pidfile;
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@ -72,6 +76,8 @@ struct daemon_state {
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const char *user;
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struct pidfh *parent_pidfh;
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struct pidfh *child_pidfh;
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enum daemon_mode mode;
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int pid;
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int keep_cur_workdir;
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int restart_delay;
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int stdmask;
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@ -79,33 +85,25 @@ struct daemon_state {
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int syslog_facility;
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int keep_fds_open;
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int output_fd;
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bool supervision_enabled;
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bool child_eof;
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bool restart_enabled;
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bool syslog_enabled;
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bool log_reopen;
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};
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static void setup_signals(struct daemon_state *);
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static void restrict_process(const char *);
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static void handle_term(int);
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static void handle_chld(int);
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static void handle_hup(int);
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static int open_log(const char *);
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static void reopen_log(struct daemon_state *);
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static bool listen_child(int, struct daemon_state *);
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static int get_log_mapping(const char *, const CODE *);
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static void open_pid_files(struct daemon_state *);
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static void do_output(const unsigned char *, size_t, struct daemon_state *);
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static void daemon_sleep(time_t, long);
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static void daemon_sleep(struct daemon_state *);
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static void daemon_state_init(struct daemon_state *);
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static void daemon_eventloop(struct daemon_state *);
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static void daemon_terminate(struct daemon_state *);
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static volatile sig_atomic_t terminate = 0;
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static volatile sig_atomic_t child_gone = 0;
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static volatile sig_atomic_t pid = 0;
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static volatile sig_atomic_t do_log_reopen = 0;
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static void daemon_exec(struct daemon_state *);
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static bool daemon_is_child_dead(struct daemon_state *);
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static void daemon_set_child_pipe(struct daemon_state *);
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static const char shortopts[] = "+cfHSp:P:ru:o:s:l:t:m:R:T:h";
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@ -170,6 +168,10 @@ main(int argc, char *argv[])
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daemon_state_init(&state);
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/* Signals are processed via kqueue */
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signal(SIGHUP, SIG_IGN);
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signal(SIGTERM, SIG_IGN);
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/*
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* Supervision mode is enabled if one of the following options are used:
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* --child-pidfile -p
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@ -205,7 +207,7 @@ main(int argc, char *argv[])
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errx(5, "unrecognized syslog facility");
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}
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state.syslog_enabled = true;
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state.supervision_enabled = true;
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state.mode = MODE_SUPERVISE;
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break;
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case 'm':
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state.stdmask = strtol(optarg, &p, 10);
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@ -221,19 +223,19 @@ main(int argc, char *argv[])
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* daemon could open the specified file and set it's
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* descriptor as both stderr and stout before execve()
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*/
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state.supervision_enabled = true;
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state.mode = MODE_SUPERVISE;
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break;
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case 'p':
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state.child_pidfile = optarg;
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state.supervision_enabled = true;
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state.mode = MODE_SUPERVISE;
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break;
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case 'P':
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state.parent_pidfile = optarg;
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state.supervision_enabled = true;
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state.mode = MODE_SUPERVISE;
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break;
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case 'r':
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state.restart_enabled = true;
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state.supervision_enabled = true;
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state.mode = MODE_SUPERVISE;
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break;
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case 'R':
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state.restart_enabled = true;
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@ -249,11 +251,11 @@ main(int argc, char *argv[])
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errx(4, "unrecognized syslog priority");
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}
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state.syslog_enabled = true;
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state.supervision_enabled = true;
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state.mode = MODE_SUPERVISE;
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break;
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case 'S':
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state.syslog_enabled = true;
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state.supervision_enabled = true;
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state.mode = MODE_SUPERVISE;
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break;
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case 't':
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state.title = optarg;
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@ -261,7 +263,7 @@ main(int argc, char *argv[])
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case 'T':
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state.syslog_tag = optarg;
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state.syslog_enabled = true;
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state.supervision_enabled = true;
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state.mode = MODE_SUPERVISE;
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break;
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case 'u':
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state.user = optarg;
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@ -302,246 +304,212 @@ main(int argc, char *argv[])
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* to be able to report the error intelligently
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*/
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open_pid_files(&state);
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/*
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* TODO: add feature to avoid backgrounding
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* i.e. --foreground, -f
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*/
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if (daemon(state.keep_cur_workdir, state.keep_fds_open) == -1) {
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warn("daemon");
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daemon_terminate(&state);
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}
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if (state.mode == MODE_DAEMON) {
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daemon_exec(&state);
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}
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/* Write out parent pidfile if needed. */
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pidfile_write(state.parent_pidfh);
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if (state.supervision_enabled) {
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/* Block SIGTERM to avoid racing until the child is spawned. */
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if (sigprocmask(SIG_BLOCK, &state.mask_term, &state.mask_orig)) {
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warn("sigprocmask");
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daemon_terminate(&state);
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}
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setup_signals(&state);
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/*
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* Try to protect against pageout kill. Ignore the
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* error, madvise(2) will fail only if a process does
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* not have superuser privileges.
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*/
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(void)madvise(NULL, 0, MADV_PROTECT);
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}
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do {
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state.mode = MODE_SUPERVISE;
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daemon_eventloop(&state);
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close(state.pipe_fd[0]);
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state.pipe_fd[0] = -1;
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} while (state.restart_enabled && !terminate);
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daemon_sleep(&state);
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} while (state.restart_enabled);
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daemon_terminate(&state);
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}
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static void
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daemon_exec(struct daemon_state *state)
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{
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pidfile_write(state->child_pidfh);
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/*
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* Main event loop: fork the child and watch for events.
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* In legacy mode simply execve into the target process.
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*
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* Signal handling logic:
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*
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* - SIGTERM is masked while there is no child.
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*
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* - SIGCHLD is masked while reading from the pipe. SIGTERM has to be
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* caught, to avoid indefinite blocking on read().
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*
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* - Both SIGCHLD and SIGTERM are masked before calling sigsuspend()
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* to avoid racing.
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*
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* - After SIGTERM is recieved and propagated to the child there are
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* several options on what to do next:
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* - read until EOF
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* - read until EOF but only for a while
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* - bail immediately
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* Currently the third option is used, because otherwise there is no
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* guarantee that read() won't block indefinitely if the child refuses
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* to depart. To handle the second option, a different approach
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* would be needed (procctl()?).
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*
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* - Child's exit might be detected by receiveing EOF from the pipe.
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* But the child might have closed its stdout and stderr, so deamon
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* must wait for the SIGCHLD to ensure that the child is actually gone.
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if (state->user != NULL) {
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restrict_process(state->user);
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}
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/* Ignored signals remain ignored after execve, unignore them */
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signal(SIGHUP, SIG_DFL);
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signal(SIGTERM, SIG_DFL);
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execvp(state->argv[0], state->argv);
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/* execvp() failed - report error and exit this process */
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err(1, "%s", state->argv[0]);
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}
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/* Main event loop: fork the child and watch for events.
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* After SIGTERM is recieved and propagated to the child there are
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* several options on what to do next:
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* - read until EOF
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* - read until EOF but only for a while
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* - bail immediately
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* Currently the third option is used, because otherwise there is no
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* guarantee that read() won't block indefinitely if the child refuses
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* to depart. To handle the second option, a different approach
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* would be needed (procctl()?).
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*/
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static void
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daemon_eventloop(struct daemon_state *state)
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{
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if (state->supervision_enabled) {
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if (pipe(state->pipe_fd)) {
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err(1, "pipe");
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}
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/*
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* Spawn a child to exec the command.
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*/
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child_gone = 0;
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pid = fork();
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}
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/* fork failed, this can only happen when supervision is enabled */
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if (pid == -1) {
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warn("fork");
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daemon_terminate(state);
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}
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/* fork succeeded, this is child's branch or supervision is disabled */
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if (pid == 0) {
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pidfile_write(state->child_pidfh);
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if (state->user != NULL) {
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restrict_process(state->user);
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}
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/*
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* In supervision mode, the child gets the original sigmask,
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* and dup'd pipes.
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*/
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if (state->supervision_enabled) {
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close(state->pipe_fd[0]);
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if (sigprocmask(SIG_SETMASK, &state->mask_orig, NULL)) {
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err(1, "sigprogmask");
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}
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if (state->stdmask & STDERR_FILENO) {
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if (dup2(state->pipe_fd[1], STDERR_FILENO) == -1) {
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err(1, "dup2");
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}
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}
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if (state->stdmask & STDOUT_FILENO) {
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if (dup2(state->pipe_fd[1], STDOUT_FILENO) == -1) {
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err(1, "dup2");
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}
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}
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if (state->pipe_fd[1] != STDERR_FILENO &&
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state->pipe_fd[1] != STDOUT_FILENO) {
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close(state->pipe_fd[1]);
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}
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}
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execvp(state->argv[0], state->argv);
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/* execvp() failed - report error and exit this process */
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err(1, "%s", state->argv[0]);
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}
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struct kevent event;
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int kq;
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int ret;
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/*
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* else: pid > 0
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* fork succeeded, this is the parent branch, this can only happen when
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* supervision is enabled.
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*
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* Unblock SIGTERM - now there is a valid child PID to signal to.
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* Try to protect against pageout kill. Ignore the
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* error, madvise(2) will fail only if a process does
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* not have superuser privileges.
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*/
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if (sigprocmask(SIG_UNBLOCK, &state->mask_term, NULL)) {
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warn("sigprocmask");
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daemon_terminate(state);
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(void)madvise(NULL, 0, MADV_PROTECT);
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if (pipe(state->pipe_fd)) {
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err(1, "pipe");
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}
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kq = kqueuex(KQUEUE_CLOEXEC);
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EV_SET(&event, state->pipe_fd[0], EVFILT_READ, EV_ADD|EV_CLEAR, 0, 0,
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NULL);
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if (kevent(kq, &event, 1, NULL, 0, NULL) == -1) {
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err(EXIT_FAILURE, "failed to register kevent");
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}
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EV_SET(&event, SIGHUP, EVFILT_SIGNAL, EV_ADD, 0, 0, NULL);
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if (kevent(kq, &event, 1, NULL, 0, NULL) == -1) {
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err(EXIT_FAILURE, "failed to register kevent");
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}
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EV_SET(&event, SIGTERM, EVFILT_SIGNAL, EV_ADD, 0, 0, NULL);
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if (kevent(kq, &event, 1, NULL, 0, NULL) == -1) {
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err(EXIT_FAILURE, "failed to register kevent");
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}
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EV_SET(&event, SIGCHLD, EVFILT_SIGNAL, EV_ADD, 0, 0, NULL);
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if (kevent(kq, &event, 1, NULL, 0, NULL) == -1) {
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err(EXIT_FAILURE, "failed to register kevent");
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}
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memset(&event, 0, sizeof(struct kevent));
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/* Spawn a child to exec the command. */
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state->pid = fork();
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/* fork failed, this can only happen when supervision is enabled */
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switch (state->pid) {
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case -1:
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warn("fork");
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state->mode = MODE_NOCHILD;
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return;
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/* fork succeeded, this is child's branch */
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case 0:
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close(kq);
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daemon_set_child_pipe(state);
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daemon_exec(state);
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break;
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}
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/* case: pid > 0; fork succeeded */
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close(state->pipe_fd[1]);
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state->pipe_fd[1] = -1;
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setproctitle("%s[%d]", state->title, (int)state->pid);
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setproctitle("%s[%d]", state->title, (int)pid);
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for (;;) {
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if (child_gone && state->child_eof) {
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break;
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}
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if (terminate) {
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daemon_terminate(state);
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}
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if (state->child_eof) {
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if (sigprocmask(SIG_BLOCK, &state->mask_susp, NULL)) {
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warn("sigprocmask");
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daemon_terminate(state);
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}
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while (!terminate && !child_gone) {
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sigsuspend(&state->mask_orig);
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}
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if (sigprocmask(SIG_UNBLOCK, &state->mask_susp, NULL)) {
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warn("sigprocmask");
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daemon_terminate(state);
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}
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while (state->mode != MODE_NOCHILD) {
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ret = kevent(kq, NULL, 0, &event, 1, NULL);
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switch (ret) {
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case -1:
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err(EXIT_FAILURE, "kevent wait");
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case 0:
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continue;
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}
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if (sigprocmask(SIG_BLOCK, &state->mask_read, NULL)) {
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warn("sigprocmask");
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daemon_terminate(state);
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if (event.flags & EV_ERROR) {
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errx(EXIT_FAILURE, "Event error: %s",
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strerror(event.data));
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}
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state->child_eof = !listen_child(state->pipe_fd[0], state);
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switch (event.filter) {
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case EVFILT_SIGNAL:
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if (sigprocmask(SIG_UNBLOCK, &state->mask_read, NULL)) {
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warn("sigprocmask");
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daemon_terminate(state);
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switch (event.ident) {
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case SIGCHLD:
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if (daemon_is_child_dead(state)) {
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/* child is dead, read all until EOF */
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state->pid = -1;
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state->mode = MODE_NOCHILD;
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while (listen_child(state->pipe_fd[0],
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state))
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;
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}
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continue;
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case SIGTERM:
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if (state->mode != MODE_SUPERVISE) {
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/* user is impatient */
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/* TODO: warn about repeated SIGTERM? */
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continue;
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}
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state->mode = MODE_TERMINATING;
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state->restart_enabled = false;
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if (state->pid > 0) {
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kill(state->pid, SIGTERM);
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}
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/*
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* TODO set kevent timer to exit
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* unconditionally after some time
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*/
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continue;
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case SIGHUP:
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if (state->log_reopen && state->output_fd >= 0) {
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reopen_log(state);
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}
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continue;
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}
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break;
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case EVFILT_READ:
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/*
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* detecting EOF is no longer necessary
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* if child closes the pipe daemon will stop getting
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* EVFILT_READ events
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*/
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if (event.data > 0) {
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(void)listen_child(state->pipe_fd[0], state);
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}
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continue;
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default:
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continue;
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}
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}
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/*
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* At the end of the loop the the child is already gone.
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* Block SIGTERM to avoid racing until the child is spawned.
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*/
|
||||
if (sigprocmask(SIG_BLOCK, &state->mask_term, NULL)) {
|
||||
warn("sigprocmask");
|
||||
daemon_terminate(state);
|
||||
}
|
||||
|
||||
/* sleep before exiting mainloop if restart is enabled */
|
||||
if (state->restart_enabled && !terminate) {
|
||||
daemon_sleep(state->restart_delay, 0);
|
||||
}
|
||||
close(kq);
|
||||
close(state->pipe_fd[0]);
|
||||
state->pipe_fd[0] = -1;
|
||||
}
|
||||
|
||||
static void
|
||||
daemon_sleep(time_t secs, long nsecs)
|
||||
daemon_sleep(struct daemon_state *state)
|
||||
{
|
||||
struct timespec ts = { secs, nsecs };
|
||||
struct timespec ts = { state->restart_delay, 0 };
|
||||
|
||||
while (!terminate && nanosleep(&ts, &ts) == -1) {
|
||||
if (!state->restart_enabled) {
|
||||
return;
|
||||
}
|
||||
while (nanosleep(&ts, &ts) == -1) {
|
||||
if (errno != EINTR) {
|
||||
err(1, "nanosleep");
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
/*
|
||||
* Setup SIGTERM, SIGCHLD and SIGHUP handlers.
|
||||
* To avoid racing SIGCHLD with SIGTERM corresponding
|
||||
* signal handlers mask the other signal.
|
||||
*/
|
||||
static void
|
||||
setup_signals(struct daemon_state *state)
|
||||
{
|
||||
struct sigaction act_term = { 0 };
|
||||
struct sigaction act_chld = { 0 };
|
||||
struct sigaction act_hup = { 0 };
|
||||
|
||||
/* Setup SIGTERM */
|
||||
act_term.sa_handler = handle_term;
|
||||
sigemptyset(&act_term.sa_mask);
|
||||
sigaddset(&act_term.sa_mask, SIGCHLD);
|
||||
if (sigaction(SIGTERM, &act_term, NULL) == -1) {
|
||||
warn("sigaction");
|
||||
daemon_terminate(state);
|
||||
}
|
||||
|
||||
/* Setup SIGCHLD */
|
||||
act_chld.sa_handler = handle_chld;
|
||||
sigemptyset(&act_chld.sa_mask);
|
||||
sigaddset(&act_chld.sa_mask, SIGTERM);
|
||||
if (sigaction(SIGCHLD, &act_chld, NULL) == -1) {
|
||||
warn("sigaction");
|
||||
daemon_terminate(state);
|
||||
}
|
||||
|
||||
/* Setup SIGHUP if configured */
|
||||
if (!state->log_reopen || state->output_fd < 0) {
|
||||
return;
|
||||
}
|
||||
|
||||
act_hup.sa_handler = handle_hup;
|
||||
sigemptyset(&act_hup.sa_mask);
|
||||
if (sigaction(SIGHUP, &act_hup, NULL) == -1) {
|
||||
warn("sigaction");
|
||||
daemon_terminate(state);
|
||||
}
|
||||
}
|
||||
|
||||
static void
|
||||
open_pid_files(struct daemon_state *state)
|
||||
{
|
||||
|
@ -610,6 +578,8 @@ restrict_process(const char *user)
|
|||
*
|
||||
* Return value of false is assumed to mean EOF or error, and true indicates to
|
||||
* continue reading.
|
||||
*
|
||||
* TODO: simplify signature - state contains pipefd
|
||||
*/
|
||||
static bool
|
||||
listen_child(int fd, struct daemon_state *state)
|
||||
|
@ -621,9 +591,6 @@ listen_child(int fd, struct daemon_state *state)
|
|||
assert(state != NULL);
|
||||
assert(bytes_read < LBUF_SIZE - 1);
|
||||
|
||||
if (do_log_reopen) {
|
||||
reopen_log(state);
|
||||
}
|
||||
rv = read(fd, buf + bytes_read, LBUF_SIZE - bytes_read - 1);
|
||||
if (rv > 0) {
|
||||
unsigned char *cp;
|
||||
|
@ -695,42 +662,6 @@ do_output(const unsigned char *buf, size_t len, struct daemon_state *state)
|
|||
}
|
||||
}
|
||||
|
||||
/*
|
||||
* We use the global PID acquired directly from fork. If there is no valid
|
||||
* child pid, the handler should be blocked and/or child_gone == 1.
|
||||
*/
|
||||
static void
|
||||
handle_term(int signo)
|
||||
{
|
||||
if (pid > 0 && !child_gone) {
|
||||
kill(pid, signo);
|
||||
}
|
||||
terminate = 1;
|
||||
}
|
||||
|
||||
static void
|
||||
handle_chld(int signo __unused)
|
||||
{
|
||||
|
||||
for (;;) {
|
||||
int rv = waitpid(-1, NULL, WNOHANG);
|
||||
if (pid == rv) {
|
||||
child_gone = 1;
|
||||
break;
|
||||
} else if (rv == -1 && errno != EINTR) {
|
||||
warn("waitpid");
|
||||
return;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
static void
|
||||
handle_hup(int signo __unused)
|
||||
{
|
||||
|
||||
do_log_reopen = 1;
|
||||
}
|
||||
|
||||
static int
|
||||
open_log(const char *outfn)
|
||||
{
|
||||
|
@ -743,7 +674,6 @@ reopen_log(struct daemon_state *state)
|
|||
{
|
||||
int outfd;
|
||||
|
||||
do_log_reopen = 0;
|
||||
outfd = open_log(state->output_filename);
|
||||
if (state->output_fd >= 0) {
|
||||
close(state->output_fd);
|
||||
|
@ -763,9 +693,9 @@ daemon_state_init(struct daemon_state *state)
|
|||
.parent_pidfile = NULL,
|
||||
.title = NULL,
|
||||
.user = NULL,
|
||||
.supervision_enabled = false,
|
||||
.child_eof = false,
|
||||
.mode = MODE_DAEMON,
|
||||
.restart_enabled = false,
|
||||
.pid = 0,
|
||||
.keep_cur_workdir = 1,
|
||||
.restart_delay = 1,
|
||||
.stdmask = STDOUT_FILENO | STDERR_FILENO,
|
||||
|
@ -778,25 +708,23 @@ daemon_state_init(struct daemon_state *state)
|
|||
.output_fd = -1,
|
||||
.output_filename = NULL,
|
||||
};
|
||||
|
||||
sigemptyset(&state->mask_susp);
|
||||
sigemptyset(&state->mask_read);
|
||||
sigemptyset(&state->mask_term);
|
||||
sigemptyset(&state->mask_orig);
|
||||
sigaddset(&state->mask_susp, SIGTERM);
|
||||
sigaddset(&state->mask_susp, SIGCHLD);
|
||||
sigaddset(&state->mask_term, SIGTERM);
|
||||
sigaddset(&state->mask_read, SIGCHLD);
|
||||
|
||||
}
|
||||
|
||||
static _Noreturn void
|
||||
daemon_terminate(struct daemon_state *state)
|
||||
{
|
||||
assert(state != NULL);
|
||||
close(state->output_fd);
|
||||
close(state->pipe_fd[0]);
|
||||
close(state->pipe_fd[1]);
|
||||
|
||||
if (state->output_fd >= 0) {
|
||||
close(state->output_fd);
|
||||
}
|
||||
if (state->pipe_fd[0] >= 0) {
|
||||
close(state->pipe_fd[0]);
|
||||
}
|
||||
|
||||
if (state->pipe_fd[1] >= 0) {
|
||||
close(state->pipe_fd[1]);
|
||||
}
|
||||
if (state->syslog_enabled) {
|
||||
closelog();
|
||||
}
|
||||
|
@ -810,3 +738,45 @@ daemon_terminate(struct daemon_state *state)
|
|||
*/
|
||||
exit(1);
|
||||
}
|
||||
|
||||
/*
|
||||
* Returns true if SIGCHILD came from state->pid
|
||||
* This function could hang if SIGCHILD was emittied for a reason other than
|
||||
* child dying (e.g., ptrace attach).
|
||||
*/
|
||||
static bool
|
||||
daemon_is_child_dead(struct daemon_state *state)
|
||||
{
|
||||
for (;;) {
|
||||
int who = waitpid(-1, NULL, WNOHANG);
|
||||
if (state->pid == who) {
|
||||
return true;
|
||||
}
|
||||
if (who == -1 && errno != EINTR) {
|
||||
warn("waitpid");
|
||||
return false;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
static void
|
||||
daemon_set_child_pipe(struct daemon_state *state)
|
||||
{
|
||||
if (state->stdmask & STDERR_FILENO) {
|
||||
if (dup2(state->pipe_fd[1], STDERR_FILENO) == -1) {
|
||||
err(1, "dup2");
|
||||
}
|
||||
}
|
||||
if (state->stdmask & STDOUT_FILENO) {
|
||||
if (dup2(state->pipe_fd[1], STDOUT_FILENO) == -1) {
|
||||
err(1, "dup2");
|
||||
}
|
||||
}
|
||||
if (state->pipe_fd[1] != STDERR_FILENO &&
|
||||
state->pipe_fd[1] != STDOUT_FILENO) {
|
||||
close(state->pipe_fd[1]);
|
||||
}
|
||||
|
||||
/* The child gets dup'd pipes. */
|
||||
close(state->pipe_fd[0]);
|
||||
}
|
||||
|
|
Loading…
Reference in a new issue