sd-daemon: introduce sd_watchdog_enabled() for parsing $WATCHDOG_USEC

Also, introduce a new environment variable named $WATCHDOG_PID which
cotnains the PID of the process that is supposed to send the keep-alive
events. This is similar how $LISTEN_FDS and $LISTEN_PID work together,
and protects against confusing processes further down the process tree
due to inherited environment.

6 files changed, 21 insertions, 10 deletions

diff --git a/src/core/execute.c b/src/core/execute.c
index 4265717895..9b33ec0ec5 100644
--- a/src/core/execute.c
+++ b/src/core/execute.c
@@ -1020,6 +1020,7 @@ static void do_idle_pipe_dance(int idle_pipe[4]) {
 static int build_environment(
                 ExecContext *c,
                 unsigned n_fds,
+                usec_t watchdog_usec,
                 const char *home,
                 const char *username,
                 const char *shell,
@@ -1032,7 +1033,7 @@ static int build_environment(
         assert(c);
         assert(ret);
 
-        our_env = new(char*, 8);
+        our_env = new0(char*, 10);
         if (!our_env)
                 return -ENOMEM;
 
@@ -1046,6 +1047,16 @@ static int build_environment(
                 our_env[n_env++] = x;
         }
 
+        if (watchdog_usec > 0) {
+                if (asprintf(&x, "WATCHDOG_PID=%lu", (unsigned long) getpid()) < 0)
+                        return -ENOMEM;
+                our_env[n_env++] = x;
+
+                if (asprintf(&x, "WATCHDOG_USEC=%llu", (unsigned long long) watchdog_usec) < 0)
+                        return -ENOMEM;
+                our_env[n_env++] = x;
+        }
+
         if (home) {
                 x = strappend("HOME=", home);
                 if (!x)
@@ -1084,7 +1095,7 @@ static int build_environment(
         }
 
         our_env[n_env++] = NULL;
-        assert(n_env <= 8);
+        assert(n_env <= 10);
 
         *ret = our_env;
         our_env = NULL;
@@ -1104,6 +1115,7 @@ int exec_spawn(ExecCommand *command,
                CGroupControllerMask cgroup_supported,
                const char *cgroup_path,
                const char *unit_id,
+               usec_t watchdog_usec,
                int idle_pipe[4],
                ExecRuntime *runtime,
                pid_t *ret) {
@@ -1560,7 +1572,7 @@ int exec_spawn(ExecCommand *command,
                         }
                 }
 
-                err = build_environment(context, n_fds, home, username, shell, &our_env);
+                err = build_environment(context, n_fds, watchdog_usec, home, username, shell, &our_env);
                 if (r < 0) {
                         r = EXIT_MEMORY;
                         goto fail_child;
diff --git a/src/core/execute.h b/src/core/execute.h
index bd3db0b633..989373f481 100644
--- a/src/core/execute.h
+++ b/src/core/execute.h
@@ -181,6 +181,7 @@ int exec_spawn(ExecCommand *command,
                CGroupControllerMask cgroup_mask,
                const char *cgroup_path,
                const char *unit_id,
+               usec_t watchdog_usec,
                int pipe_fd[2],
                ExecRuntime *runtime,
                pid_t *ret);
diff --git a/src/core/mount.c b/src/core/mount.c
index 2b7934e404..09efa1b6e0 100644
--- a/src/core/mount.c
+++ b/src/core/mount.c
@@ -787,6 +787,7 @@ static int mount_spawn(Mount *m, ExecCommand *c, pid_t *_pid) {
                        UNIT(m)->manager->cgroup_supported,
                        UNIT(m)->cgroup_path,
                        UNIT(m)->id,
+                       0,
                        NULL,
                        m->exec_runtime,
                        &pid);
diff --git a/src/core/service.c b/src/core/service.c
index 87eaa29378..4eb3d9e668 100644
--- a/src/core/service.c
+++ b/src/core/service.c
@@ -1750,7 +1750,7 @@ static int service_spawn(
         if (r < 0)
                 goto fail;
 
-        our_env = new0(char*, 5);
+        our_env = new0(char*, 4);
         if (!our_env) {
                 r = -ENOMEM;
                 goto fail;
@@ -1768,12 +1768,6 @@ static int service_spawn(
                         goto fail;
                 }
 
-        if (s->watchdog_usec > 0)
-                if (asprintf(our_env + n_env++, "WATCHDOG_USEC=%llu", (unsigned long long) s->watchdog_usec) < 0) {
-                        r = -ENOMEM;
-                        goto fail;
-                }
-
         if (UNIT(s)->manager->running_as != SYSTEMD_SYSTEM)
                 if (asprintf(our_env + n_env++, "MANAGERPID=%lu", (unsigned long) getpid()) < 0) {
                         r = -ENOMEM;
@@ -1804,6 +1798,7 @@ static int service_spawn(
                        UNIT(s)->manager->cgroup_supported,
                        path,
                        UNIT(s)->id,
+                       s->watchdog_usec,
                        s->type == SERVICE_IDLE ? UNIT(s)->manager->idle_pipe : NULL,
                        s->exec_runtime,
                        &pid);
diff --git a/src/core/socket.c b/src/core/socket.c
index 2442221355..31fc2a2526 100644
--- a/src/core/socket.c
+++ b/src/core/socket.c
@@ -1254,6 +1254,7 @@ static int socket_spawn(Socket *s, ExecCommand *c, pid_t *_pid) {
                        UNIT(s)->manager->cgroup_supported,
                        UNIT(s)->cgroup_path,
                        UNIT(s)->id,
+                       0,
                        NULL,
                        s->exec_runtime,
                        &pid);
diff --git a/src/core/swap.c b/src/core/swap.c
index 79862e5b87..e0627db965 100644
--- a/src/core/swap.c
+++ b/src/core/swap.c
@@ -645,6 +645,7 @@ static int swap_spawn(Swap *s, ExecCommand *c, pid_t *_pid) {
                        UNIT(s)->manager->cgroup_supported,
                        UNIT(s)->cgroup_path,
                        UNIT(s)->id,
+                       0,
                        NULL,
                        s->exec_runtime,
                        &pid);