1 files changed, 154 insertions, 0 deletions
diff --git a/src/lighttpd-angel.c b/src/lighttpd-angel.c
new file mode 100644
index 0000000..a6e3741
--- /dev/null
+++ b/src/lighttpd-angel.c
@@ -0,0 +1,154 @@
+/**
+ * angel process for lighttpd 
+ *
+ * the purpose is the run as root all the time and handle:
+ * - restart on crash
+ * - spawn on HUP to allow graceful restart
+ * - ...
+ *
+ * it has to stay safe and small to be trustable
+ */
+
+#include <sys/wait.h>
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <time.h>
+#include <signal.h>
+
+#define BINPATH SBIN_DIR"/lighttpd"
+
+static siginfo_t last_sigterm_info;
+static siginfo_t last_sighup_info;
+
+static volatile sig_atomic_t start_process    = 1;
+static volatile sig_atomic_t graceful_restart = 0;
+static volatile pid_t pid = -1;
+
+static void sigaction_handler(int sig, siginfo_t *si, void *context) {
+	int exitcode;
+
+	switch (sig) {
+	case SIGINT: 
+	case SIGTERM:
+		memcpy(&last_sigterm_info, si, sizeof(*si));
+
+		/** forward the sig to the child */
+		kill(pid, sig);
+		break;
+	case SIGHUP: /** do a graceful restart */
+		memcpy(&last_sighup_info, si, sizeof(*si));
+
+		/** do a graceful shutdown on the main process and start a new child */
+		kill(pid, SIGINT);
+
+		usleep(5 * 1000); /** wait 5 microsec */
+		
+		start_process = 1;
+		break;
+	case SIGCHLD:
+		/** a child died, de-combie it */
+		wait(&exitcode);
+		break;
+	}
+}
+
+int main(int argc, char **argv) {
+	int is_shutdown = 0;
+	struct sigaction act;
+
+	/**
+	 * we are running as root BEWARE
+	 */
+
+	memset(&act, 0, sizeof(act));
+	act.sa_handler = SIG_IGN;
+	sigaction(SIGPIPE, &act, NULL);
+	sigaction(SIGUSR1, &act, NULL);
+
+	act.sa_sigaction = sigaction_handler;
+	sigemptyset(&act.sa_mask);
+	act.sa_flags = SA_SIGINFO;
+
+	sigaction(SIGINT,  &act, NULL);
+	sigaction(SIGTERM, &act, NULL);
+	sigaction(SIGHUP,  &act, NULL);
+	sigaction(SIGALRM, &act, NULL);
+	sigaction(SIGCHLD, &act, NULL);
+
+	/* check that the compiled in path has the right user,
+	 *
+	 * BEWARE: there is a race between the check here and the exec later
+	 */
+
+	while (!is_shutdown) {
+		int exitcode = 0;
+
+		if (start_process) {
+			pid = fork();
+
+			if (0 == pid) {
+				/* i'm the child */
+
+				argv[0] = BINPATH;
+
+				execvp(BINPATH, argv);
+
+				exit(1);
+			} else if (-1 == pid) {
+				/** error */
+
+				return -1;
+			}
+
+			/* I'm the angel */
+			start_process = 0;
+		}
+	       
+		if ((pid_t)-1 == waitpid(pid, &exitcode, 0)) {
+			switch (errno) {
+			case EINTR:
+				/* someone sent a signal ... 
+				 * do we have to shutdown or restart the process */
+				break;
+			case ECHILD:
+				/** 
+				 * make sure we are not in a race between the signal handler
+				 * and the process restart */
+				if (!start_process) is_shutdown = 1;
+				break;
+			default:
+				break;
+			}
+		} else {
+			/** process went away */
+
+			if (WIFEXITED(exitcode)) {
+				/** normal exit */
+
+				is_shutdown = 1;
+
+				fprintf(stderr, "%s.%d: child (pid=%d) exited normally with exitcode: %d\n", 
+						__FILE__, __LINE__,
+						pid,
+						WEXITSTATUS(exitcode));
+
+			} else if (WIFSIGNALED(exitcode)) {
+				/** got a signal */
+
+				fprintf(stderr, "%s.%d: child (pid=%d) exited unexpectedly with signal %d, restarting\n", 
+						__FILE__, __LINE__,
+						pid,
+						WTERMSIG(exitcode));
+
+				start_process = 1;
+			}
+		}
+	}
+
+	return 0;
+}
+