BUG/MINOR: systemd: always restore signals before execve()
Since signals are inherited, we must restore them before calling execve()
and intercept them again after a failed execve(). In order to cleanly deal
with the SIGUSR2/SIGHUP loops where we re-exec the wrapper, we ignore these
two signals during a re-exec, and restore them to defaults when spawning
haproxy.
This should be backported to 1.6 and 1.5.
diff --git a/src/haproxy-systemd-wrapper.c b/src/haproxy-systemd-wrapper.c
index a78e75b..84d2e17 100644
--- a/src/haproxy-systemd-wrapper.c
+++ b/src/haproxy-systemd-wrapper.c
@@ -28,6 +28,11 @@
static int wrapper_argc;
static char **wrapper_argv;
+static void setup_signal_handler();
+static void pause_signal_handler();
+static void reset_signal_handler();
+
+
/* returns the path to the haproxy binary into <buffer>, whose size indicated
* in <buffer_size> must be at least 1 byte long.
*/
@@ -76,6 +81,8 @@
char **argv = calloc(4 + main_argc + nb_pid + 1, sizeof(char *));
int i;
int argno = 0;
+
+ reset_signal_handler();
locate_haproxy(haproxy_bin, 512);
argv[argno++] = haproxy_bin;
for (i = 0; i < main_argc; ++i)
@@ -127,6 +134,34 @@
caught_signal = signum;
}
+static void setup_signal_handler()
+{
+ struct sigaction sa;
+
+ memset(&sa, 0, sizeof(struct sigaction));
+ sa.sa_handler = &signal_handler;
+ sigaction(SIGUSR2, &sa, NULL);
+ sigaction(SIGHUP, &sa, NULL);
+ sigaction(SIGINT, &sa, NULL);
+ sigaction(SIGTERM, &sa, NULL);
+}
+
+static void pause_signal_handler()
+{
+ signal(SIGUSR2, SIG_IGN);
+ signal(SIGHUP, SIG_IGN);
+ signal(SIGINT, SIG_DFL);
+ signal(SIGTERM, SIG_DFL);
+}
+
+static void reset_signal_handler()
+{
+ signal(SIGUSR2, SIG_DFL);
+ signal(SIGHUP, SIG_DFL);
+ signal(SIGINT, SIG_DFL);
+ signal(SIGTERM, SIG_DFL);
+}
+
/* handles SIGUSR2 and SIGHUP only */
static void do_restart(int sig)
{
@@ -134,7 +169,11 @@
fprintf(stderr, SD_NOTICE "haproxy-systemd-wrapper: re-executing on %s.\n",
sig == SIGUSR2 ? "SIGUSR2" : "SIGHUP");
+ /* don't let the other process take one of those signals by accident */
+ pause_signal_handler();
execv(wrapper_argv[0], wrapper_argv);
+ /* failed, let's reinstall the signal handler and continue */
+ setup_signal_handler();
}
/* handles SIGTERM and SIGINT only */
@@ -168,7 +207,8 @@
int main(int argc, char **argv)
{
int status;
- struct sigaction sa;
+
+ setup_signal_handler();
wrapper_argc = argc;
wrapper_argv = argv;
@@ -176,13 +216,6 @@
--argc; ++argv;
init(argc, argv);
- memset(&sa, 0, sizeof(struct sigaction));
- sa.sa_handler = &signal_handler;
- sigaction(SIGUSR2, &sa, NULL);
- sigaction(SIGHUP, &sa, NULL);
- sigaction(SIGINT, &sa, NULL);
- sigaction(SIGTERM, &sa, NULL);
-
if (getenv(REEXEC_FLAG) != NULL) {
/* We are being re-executed: restart HAProxy gracefully */
int i;