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From 7a7eada6f4ecfc54325a18cf20c3035994a901c4 Mon Sep 17 00:00:00 2001
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From: Willy Tarreau <w@1wt.eu>
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Date: Tue, 25 Oct 2016 16:49:31 +0200
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Subject: [PATCH 13/26] BUG/MINOR: systemd: always restore signals before
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execve()
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Since signals are inherited, we must restore them before calling execve()
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and intercept them again after a failed execve(). In order to cleanly deal
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with the SIGUSR2/SIGHUP loops where we re-exec the wrapper, we ignore these
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two signals during a re-exec, and restore them to defaults when spawning
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haproxy.
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This should be backported to 1.6 and 1.5.
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(cherry picked from commit 4351ea61fbddf88c960179d60b0e0f1b090f0b70)
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---
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src/haproxy-systemd-wrapper.c | 49 ++++++++++++++++++++++++++++++++++++-------
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1 file changed, 41 insertions(+), 8 deletions(-)
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diff --git a/src/haproxy-systemd-wrapper.c b/src/haproxy-systemd-wrapper.c
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index a78e75b..84d2e17 100644
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--- a/src/haproxy-systemd-wrapper.c
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+++ b/src/haproxy-systemd-wrapper.c
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@@ -28,6 +28,11 @@ static char *pid_file = "/run/haproxy.pid";
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static int wrapper_argc;
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static char **wrapper_argv;
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+static void setup_signal_handler();
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+static void pause_signal_handler();
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+static void reset_signal_handler();
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+
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+
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/* returns the path to the haproxy binary into <buffer>, whose size indicated
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* in <buffer_size> must be at least 1 byte long.
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*/
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@@ -76,6 +81,8 @@ static void spawn_haproxy(char **pid_strv, int nb_pid)
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char **argv = calloc(4 + main_argc + nb_pid + 1, sizeof(char *));
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int i;
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int argno = 0;
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+
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+ reset_signal_handler();
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locate_haproxy(haproxy_bin, 512);
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argv[argno++] = haproxy_bin;
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for (i = 0; i < main_argc; ++i)
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@@ -127,6 +134,34 @@ static void signal_handler(int signum)
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caught_signal = signum;
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}
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+static void setup_signal_handler()
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+{
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+ struct sigaction sa;
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+
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+ memset(&sa, 0, sizeof(struct sigaction));
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+ sa.sa_handler = &signal_handler;
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+ sigaction(SIGUSR2, &sa, NULL);
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+ sigaction(SIGHUP, &sa, NULL);
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+ sigaction(SIGINT, &sa, NULL);
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+ sigaction(SIGTERM, &sa, NULL);
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+}
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+
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+static void pause_signal_handler()
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+{
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+ signal(SIGUSR2, SIG_IGN);
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+ signal(SIGHUP, SIG_IGN);
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+ signal(SIGINT, SIG_DFL);
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+ signal(SIGTERM, SIG_DFL);
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+}
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+
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+static void reset_signal_handler()
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+{
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+ signal(SIGUSR2, SIG_DFL);
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+ signal(SIGHUP, SIG_DFL);
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+ signal(SIGINT, SIG_DFL);
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+ signal(SIGTERM, SIG_DFL);
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+}
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+
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/* handles SIGUSR2 and SIGHUP only */
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static void do_restart(int sig)
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{
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@@ -134,7 +169,11 @@ static void do_restart(int sig)
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fprintf(stderr, SD_NOTICE "haproxy-systemd-wrapper: re-executing on %s.\n",
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sig == SIGUSR2 ? "SIGUSR2" : "SIGHUP");
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+ /* don't let the other process take one of those signals by accident */
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+ pause_signal_handler();
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execv(wrapper_argv[0], wrapper_argv);
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+ /* failed, let's reinstall the signal handler and continue */
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+ setup_signal_handler();
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}
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/* handles SIGTERM and SIGINT only */
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@@ -168,7 +207,8 @@ static void init(int argc, char **argv)
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int main(int argc, char **argv)
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{
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int status;
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- struct sigaction sa;
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+
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+ setup_signal_handler();
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wrapper_argc = argc;
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wrapper_argv = argv;
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@@ -176,13 +216,6 @@ int main(int argc, char **argv)
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--argc; ++argv;
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init(argc, argv);
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- memset(&sa, 0, sizeof(struct sigaction));
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- sa.sa_handler = &signal_handler;
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- sigaction(SIGUSR2, &sa, NULL);
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- sigaction(SIGHUP, &sa, NULL);
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- sigaction(SIGINT, &sa, NULL);
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- sigaction(SIGTERM, &sa, NULL);
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-
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if (getenv(REEXEC_FLAG) != NULL) {
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/* We are being re-executed: restart HAProxy gracefully */
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int i;
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--
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2.7.3
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