fix: ignore SIGTERM in gravity child to survive systemd cgroup-level kill

setsid() was already added to detach the child from the parent's
process group, but systemd's default KillMode=control-group sends
SIGTERM to ALL processes in the cgroup, not just the process group.
After execv(), custom signal handlers are reset to SIG_DFL, so the
gravity child was still killed immediately.

Set SIG_IGN for SIGTERM before execv() since SIG_IGN (unlike custom
handlers) is preserved across exec. This lets gravity run to
completion even when FTL receives SIGTERM from systemd.

Signed-off-by: Dominik <[email protected]>

Author: DL6ER

src/api/action.c

@@ -64,6 +64,13 @@ static int run_and_stream_command(struct ftl_conn *api, const char *path, const
 		// propagate to this child.
 		(void)setsid();
 
+		// Ignore SIGTERM so systemd's cgroup-level kill (the
+		// default KillMode=control-group sends SIGTERM to ALL
+		// processes in the cgroup) doesn't terminate gravity
+		// mid-run. SIG_IGN is preserved across execv(), unlike
+		// custom handlers which are reset to SIG_DFL.
+		signal(SIGTERM, SIG_IGN);
+
 		// Run pihole -g
 		execv(path, (char *const *)args);