Add support for if:[!]ident and ifdef:[!]ident for run/task/services

Conditional loading of stanza depending on ident is already loaded.  The
if: checks as in-band while ifdef: checks out-of-band, i.e., post eval.

The optional leading '!' negates the comparison, if NOT foo then ...

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/conf.c

@@ -1011,6 +1011,9 @@ int conf_reload(void)
 	/* Mark any reverse deps as chenaged. */
 	service_update_rdeps();
 
+	/* Prune according to ifdef:[!]ident */
+	service_mark_unavail();
+
 	/* Set up top-level cgroups */
 	cgroup_config();
 done:

src/service.c

@@ -1395,6 +1395,7 @@ int service_register(int type, char *cfg, struct rlimit rlimit[], char *file)
 	char *id = NULL, *env = NULL, *cgroup = NULL;
 	char *pre_script = NULL, *post_script = NULL;
 	char *ready_script = NULL, *conflict = NULL;
+	char *ifdef = NULL, *ifident = NULL;
 	char *notify = NULL;
 	struct tty tty = { 0 };
 	char *dev = NULL;
@@ -1507,6 +1508,10 @@ int service_register(int type, char *cfg, struct rlimit rlimit[], char *file)
 			cgroup = arg; /* with group */
 		else if (MATCH_CMD(cmd, "conflict:", arg))
 			conflict = arg;
+		else if (MATCH_CMD(cmd, "if:", arg))
+			ifident = arg;
+		else if (MATCH_CMD(cmd, "ifdef:", arg))
+			ifdef = arg;
 		else
 			break;
 
@@ -1520,6 +1525,18 @@ int service_register(int type, char *cfg, struct rlimit rlimit[], char *file)
 	if (!id)
 		id = "";
 
+	if (ifident) {
+		char ident[MAX_IDENT_LEN];
+
+		if (id[0]) {
+			snprintf(ident, sizeof(ident), "%s:%s", name, id);
+		} else
+			strlcpy(ident, name, sizeof(ident));
+
+		if (!svc_ifthen(ident, ifident))
+			return 0;
+	}
+
 	levels = conf_parse_runlevels(runlevels);
 	if (runlevel > 0 && !ISOTHER(levels, 0)) {
 		dbg("Skipping %s%s%s, bootstrap is completed.",
@@ -1710,6 +1727,10 @@ int service_register(int type, char *cfg, struct rlimit rlimit[], char *file)
 		strlcpy(svc->conflict, conflict, sizeof(svc->conflict));
 	else
 		memset(svc->conflict, 0, sizeof(svc->conflict));
+	if (ifdef)
+		strlcpy(svc->ifdef, ifdef, sizeof(svc->ifdef));
+	else
+		memset(svc->ifdef, 0, sizeof(svc->ifdef));
 	svc->manual  = manual;
 	svc->respawn = respawn;
 	svc->forking = forking;
@@ -1897,6 +1918,25 @@ void service_update_rdeps(void)
 	}
 }
 
+/*
+ * Drop services with 'if:otherserv' if otherserv does not exist.
+ * Drop services with 'if:!otherserv' if otherserv does exist.
+ */
+void service_mark_unavail(void)
+{
+	svc_t *svc, *iter = NULL;
+
+	for (svc = svc_iterator(&iter, 1); svc; svc = svc_iterator(&iter, 0)) {
+		char buf[MAX_IDENT_LEN];
+
+		if (!svc->ifdef[0])
+			continue;
+
+		if (!svc_ifthen(svc_ident(svc, buf, sizeof(buf)), svc->ifdef))
+			svc_mark(svc);
+	}
+}
+
 static void service_kill_script(svc_t *svc)
 {
 	if (svc->pid <= 1)

src/service.h

@@ -34,6 +34,7 @@ void      service_unregister     (svc_t *svc);
 void      service_runtask_clean  (void);
 void      service_reload_dynamic (void);
 void      service_update_rdeps   (void);
+void      service_mark_unavail   (void);
 
 void      service_ready_script   (svc_t *svc); /* XXX: only for pidfile plugin before notify framework */
 

src/svc.c

@@ -686,6 +686,32 @@ int svc_conflicts(svc_t *svc)
 	return rc;
 }
 
+int svc_ifthen(const char *ident, const char *stmt)
+{
+	int not = 0;
+	svc_t *svc;
+
+	if (!stmt || !stmt[0])
+		return 1;
+
+	if (stmt[0] == '!') {
+		stmt++;
+		not++;
+	}
+
+	svc = svc_find_by_str(stmt);
+	if (not && svc) {
+		dbg("skipping %s, %s already loaded.", ident, svc_ident(svc, NULL, 0));
+		return 0;
+	}
+	if (!not && !svc) {
+		dbg("skipping %s, %s not available.", ident, stmt);
+		return 0;
+	}
+
+	return 1;
+}
+
 /* break up "job:id job:id job:id ..." into several "job:id" tokens */
 static char *tokstr(char *str, size_t len)
 {

src/svc.h

@@ -138,6 +138,7 @@ typedef struct svc {
 	int            job;	       /* For intenal use only, canonical ref is NAME:ID */
 	char           name[MAX_ARG_LEN];
 	char           id[MAX_ID_LEN]; /* :ID */
+	char           ifdef[MAX_IDENT_LEN];
 
 	/* Counters */
 	char           once;	       /* run/task, (at least) once per runlevel */
@@ -237,6 +238,7 @@ void	    svc_prune_bootstrap	   (void);
 void        svc_enable             (svc_t *svc);
 int         svc_enabled            (svc_t *svc);
 int         svc_conflicts          (svc_t *svc);
+int         svc_ifthen             (const char *ident, const char *ifstm);
 
 int         svc_parse_jobstr       (char *str, size_t len, void *user_data, int (*found)(svc_t *, void *), int (not_found)(char *, char *, void *));