Add support for configuring cgroups and their settings on services

This patch adds support for modifying settings for the default cgroups;
init, user, and system, as well as adding up to a total of eight groups
for the system.

Services can now be assigned to a cgroup, with optional extra settings
for that particular process group.  The syntax is slightly contrivied
but follows the overall Finit syntax of prop:value,prop':value', e.g.

   cgroup maint cpu.weight:123,mem.max:10000

Starting with the introduction of rlimits, a group of services sharing
the same .conf file can share the same (locally "global") rlimits, and
now also the same cgroup, e.g.

    cgroup.maint
    service foo
    service bar cgroup:mem.max:1000

This puts foo and bar in the same top-level cgroup 'maint', with an
extra memory restriction on bar for max 1000 bytes memory.

NOTE: 'mem.' is a Finit extension, a shorthand for cgroups2 'memory.'

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

src/conf.c

@@ -23,6 +23,7 @@
 
 #include "config.h"		/* Generated by configure script */
 
+#include <ctype.h>
 #include <dirent.h>
 #include <string.h>
 #include <sys/inotify.h>
@@ -50,6 +51,10 @@ int logfile_count_max = 5;
 struct rlimit initial_rlimit[RLIMIT_NLIMITS];
 struct rlimit global_rlimit[RLIMIT_NLIMITS];
 
+struct cgroup cgroups[8];
+size_t cgroups_num;
+char cgroup_current[16]; /* cgroup.NAME sets current cgroup for a set of services */
+
 struct conf_change {
 	TAILQ_ENTRY(conf_change) link;
 	char *name;
@@ -423,6 +428,67 @@ error:
 	logit(LOG_WARNING, "rlimit: parse error");
 }
 
+/* reset defaults */
+static void init_cgroups(void)
+{
+	struct cgroup init[3] = {
+		{ .name = "init",   .cfg = "cpu.weight:100"  },
+		{ .name = "user",   .cfg = "cpu.weight:100"  },
+		{ .name = "system", .cfg = "cpu.weight:9800" },
+	};
+	size_t i;
+
+	for (i = 0; i < NELEMS(init); i++)
+		memcpy(&cgroups[i], &init[i], sizeof(struct cgroup));
+
+	cgroups_num = i;
+}
+
+struct cgroup *conf_cgfind(char *name)
+{
+	size_t i;
+
+	for (i = 0; i < cgroups_num; i++) {
+		if (strcmp(cgroups[i].name, name))
+			continue;
+
+		return &cgroups[i];
+	}
+
+	return NULL;
+}
+
+/* cgroup NAME ctrl.prop:value,ctrl.prop:value ... */
+static void conf_parse_cgroup(char *line)
+{
+	struct cgroup *cg;
+	char *ptr, *name;
+
+	name = strtok(line, " \t");
+	if (!name)
+		return;
+
+	cg = conf_cgfind(name);
+	if (!cg) {
+		if (strstr(name, "..") || strchr(name, '/'))
+			return;		/* illegal */
+		if (cgroups_num + 1 == NELEMS(cgroups))
+			return;		/* exhausted */
+
+		cg = &cgroups[cgroups_num++];
+		strlcpy(cg->name, name, sizeof(cg->name));
+	}
+
+	cg->cfg[0] = 0;
+	while ((ptr = strtok(NULL, " \t"))) {
+		if (cg->cfg[0])
+			strlcat(cg->cfg, ",", sizeof(cg->cfg));
+		strlcat(cg->cfg, ptr, sizeof(cg->cfg));
+	}
+
+	_d("cg->cfg: %s", cg->cfg);
+}
+
 static void parse_static(char *line, int is_rcsd)
 {
 	char cmd[CMD_SIZE];
@@ -552,6 +618,18 @@ static void parse_dynamic(char *line, struct rlimit rlimit[], char *file)
 		return;
 	}
 
+	/* Read contrl group limits */
+	if (MATCH_CMD(line, "cgroup ", x)) {
+		conf_parse_cgroup(x);
+		return;
+	}
+
+	/* Set current cgroup for the following services/run/tasks */
+	if (MATCH_CMD(line, "cgroup.", x)) {
+		strlcpy(cgroup_current, x, sizeof(cgroup_current));
+		return;
+	}
+
 	/* Regular or serial TTYs to run getty */
 	if (MATCH_CMD(line, "tty ", x)) {
 		tty_register(strip_line(x), rlimit, file);
@@ -580,9 +658,11 @@ static int parse_conf(char *file, int is_rcsd)
 	if (!fp)
 		return 1;
 
-	/* Prepare default limits for each service in /etc/finit.d/ */
-	if (is_rcsd)
+	/* Prepare default limits and group for each service in /etc/finit.d/ */
+	if (is_rcsd) {
 		memcpy(rlimit, global_rlimit, sizeof(rlimit));
+		memset(cgroup_current, 0, sizeof(cgroup_current));
+	}
 
 	_d("*** Parsing %s", file);
 	while (!feof(fp)) {
@@ -630,6 +710,9 @@ int conf_reload(void)
 	 */
 	memcpy(global_rlimit, initial_rlimit, sizeof(global_rlimit));
 
+	/* Initialize default cgroups */
+	init_cgroups();
+
 	if (rescue) {
 		int rc;
 		char line[80] = "tty [12345] @console noclear nologin";
@@ -699,6 +782,9 @@ int conf_reload(void)
 
 	/* Mark any reverse deps as chenaged. */
 	service_update_rdeps();
+
+	/* Set up top-level cgroups */
+	cgroup_config(cgroups_num, cgroups);
 done:
 	/* Drop record of all .conf changes */
 	drop_changes();
@@ -888,7 +974,7 @@ int conf_monitor(void)
 }
 
 /*
- * Prepare .conf parser and load all .conf files
+ * Prepare .conf parser and load /etc/finit.conf for global settings
  */
 int conf_init(uev_ctx_t *ctx)
 {
@@ -911,6 +997,12 @@ int conf_init(uev_ctx_t *ctx)
 	/* Initialize global rlimits, e.g. for built-in services */
 	memcpy(global_rlimit, initial_rlimit, sizeof(global_rlimit));
 
+	/* Initialize default cgroups */
+	init_cgroups();
+
+	/* Read global rlimits and global cgroup setup from /etc/finit.conf */
+	parse_conf(FINIT_CONF, 0);
+
 	/* prepare /etc watcher */
 	fd = iwatch_init(&iw_conf);
 	if (fd < 0)