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BUG/MINOR: systemd: always restore signals before execve()

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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.
This commit is contained in:
Willy Tarreau 2016-10-25 16:49:31 +02:00
parent 7643d09dca
commit 4351ea61fb
1 changed files with 41 additions and 8 deletions
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49
src/haproxy-systemd-wrapper.c
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@ -28,6 +28,11 @@ static char *pid_file = "/run/haproxy.pid";
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 @@ static void spawn_haproxy(char **pid_strv, int nb_pid)
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 @@ static void signal_handler(int signum)
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 @@ static void do_restart(int sig)
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 @@ static void init(int argc, char **argv)
int main(int argc, char **argv)
{
int status;
struct sigaction sa;
setup_signal_handler();
wrapper_argc = argc;
wrapper_argv = argv;
@ -176,13 +216,6 @@ int main(int argc, char **argv)
--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;