MEDIUM: Improve signal handling in systemd wrapper.

Move all code out of the signal handlers, since this is potentially
dangerous. To make sure the signal handlers behave as expected, use
sigaction() instead of signal(). That also obsoletes messing with
the signal mask after restart.

Signed-off-by: Conrad Hoffmann <conrad@soundcloud.com>

diff --git a/src/haproxy-systemd-wrapper.c b/src/haproxy-systemd-wrapper.c
index 529b2136df29286d5ce246b3229095b6914217d6..90a94ce47fdb41557bb2a70c7e2287937ed2b1f0 100644 (file)
--- a/src/haproxy-systemd-wrapper.c
+++ b/src/haproxy-systemd-wrapper.c
@@ -22,6 +22,8 @@
 #define SD_DEBUG "<7>"
 #define SD_NOTICE "<5>"
 
+static volatile sig_atomic_t caught_signal;
+
 static char *pid_file = "/run/haproxy.pid";
 static int wrapper_argc;
 static char **wrapper_argv;
@@ -103,7 +105,12 @@ static int read_pids(char ***pid_strv)
        return read;
 }
 
-static void sigusr2_handler(int signum __attribute__((unused)))
+static void signal_handler(int signum)
+{
+       caught_signal = signum;
+}
+
+static void do_restart(void)
 {
        setenv(REEXEC_FLAG, "1", 1);
        fprintf(stderr, SD_NOTICE "haproxy-systemd-wrapper: re-executing\n");
@@ -111,7 +118,7 @@ static void sigusr2_handler(int signum __attribute__((unused)))
        execv(wrapper_argv[0], wrapper_argv);
 }
 
-static void sigint_handler(int signum __attribute__((unused)))
+static void do_shutdown(void)
 {
        int i, pid;
        char **pid_strv = NULL;
@@ -147,25 +154,21 @@ int main(int argc, char **argv)
        --argc; ++argv;
        init(argc, argv);
 
-       signal(SIGINT, &sigint_handler);
-       signal(SIGUSR2, &sigusr2_handler);
+       struct sigaction sa;
+       memset(&sa, 0, sizeof(struct sigaction));
+       sa.sa_handler = &signal_handler;
+       sigaction(SIGUSR2, &sa, NULL);
+       sigaction(SIGINT, &sa, NULL);
 
        if (getenv(REEXEC_FLAG) != NULL) {
                /* We are being re-executed: restart HAProxy gracefully */
                int i;
                char **pid_strv = NULL;
                int nb_pid = read_pids(&pid_strv);
-               sigset_t sigs;
 
                unsetenv(REEXEC_FLAG);
                spawn_haproxy(pid_strv, nb_pid);
 
-               /* Unblock SIGUSR2 which was blocked by the signal handler
-                * before re-exec */
-               sigprocmask(SIG_BLOCK, NULL, &sigs);
-               sigdelset(&sigs, SIGUSR2);
-               sigprocmask(SIG_SETMASK, &sigs, NULL);
-
                for (i = 0; i < nb_pid; ++i)
                        free(pid_strv[i]);
                free(pid_strv);
@@ -176,8 +179,16 @@ int main(int argc, char **argv)
        }
 
        status = -1;
-       while (-1 != wait(&status) || errno == EINTR)
-               ;
+       while (-1 != wait(&status) || errno == EINTR) {
+               if (caught_signal == SIGUSR2) {
+                       caught_signal = 0;
+                       do_restart();
+               }
+               else if (caught_signal == SIGINT) {
+                       caught_signal = 0;
+                       do_shutdown();
+               }
+       }
 
        fprintf(stderr, SD_NOTICE "haproxy-systemd-wrapper: exit, haproxy RC=%d\n",
                        status);