Refactor sys condition plugin into a standalone keventd

This patch is a refactor of the prototype sys condition plugin.  It
moves most of the logic to monitor kernel events into a keventd that,
currently only, sets and clears the sys/pwr/ac condition.  The sys
plugin itself is now only a monitor of conditions and ensures Finit
follows them.  This is a lot more secure and moves (at least one piece
of) netlink processing out from PID 1.

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

plugins/sys.c

@@ -33,40 +33,71 @@
 #include "plugin.h"
 #include "iwatch.h"
 
-#define _PATH_SYSFS_PWR  "/sys/class/power_supply"
-
 static struct iwatch iw_sys;
-static int num_ac_online;
-static int num_ac;
 
-static void sys_cond(int set)
+
+static int sys_add_path(struct iwatch *iw, char *path)
 {
-	char cond[MAX_COND_LEN] = COND_SYS;
-
-	strlcat(cond, "pwr/ac", sizeof(cond));
-	if (set)
-		cond_set_oneshot(cond);
-	else
-		cond_clear(cond);
+	return iwatch_add(iw, path, IN_ONLYDIR | IN_CLOSE_WRITE);
 }
 
-static int check_online(char *ac)
+static void sys_update_conds(char *dir, char *name, uint32_t mask)
 {
-	char path[strlen(ac) + 1];
-	char *ptr;
-	int val;
+	char fn[PATH_MAX];
+	char *cond;
 
-	strlcpy(path, ac, sizeof(path));
-	ptr = strrchr(path, '/');
-	if (!ptr)
-		return 0;
-	ptr[1] = 0;
-	strlcat(path, "online", sizeof(path));
+	paste(fn, sizeof(fn), dir, name);
+	cond = strstr(fn, COND_BASE);
+	if (!cond)
+		return;
 
-	if (fngetint(path, &val))
-		return 0;
+	cond += strlen(COND_BASE) + 1;
+	_d("cond: %s set: %d", cond, mask & IN_CREATE ? 1 : 0);
+	cond_update(cond);
+}
 
-	return val;
+/* synthesize events in case of new run dirs */
+static void sys_scandir(struct iwatch *iw, char *dir, int len)
+{
+	glob_t gl;
+	size_t i;
+	char path[len + 6];
+	int rc;
+
+	snprintf(path, sizeof(path), "%s/*", dir);
+	rc = glob(path, GLOB_NOSORT, NULL, &gl);
+	if (rc && rc != GLOB_NOMATCH)
+		return;
+
+	for (i = 0; i < gl.gl_pathc; i++) {
+		_d("scan found %s", gl.gl_pathv[i]);
+		sys_update_conds(dir, gl.gl_pathv[i], IN_CREATE);
+	}
+	globfree(&gl);
+}
+
+/*
+ * create/remove sub-directory in monitored directory
+ */
+static void sys_handle_dir(struct iwatch *iw, char *dir, char *name, int mask)
+{
+	char path[strlen(dir) + strlen(name) + 2];
+	struct iwatch_path *iwp;
+
+	paste(path, sizeof(path), dir, name);
+	_d("path: %s", path);
+
+	iwp = iwatch_find_by_path(iw, path);
+
+	if (mask & IN_CREATE) {
+		if (!iwp) {
+			if (!sys_add_path(iw, path))
+				sys_scandir(iw, path, sizeof(path));
+		}
+	} else if (mask & IN_DELETE) {
+		if (iwp)
+			iwatch_del(&iw_sys, iwp);
+	}
 }
 
 static void sys_callback(void *arg, int fd, int events)
@@ -102,99 +133,34 @@ static void sys_callback(void *arg, int fd, int events)
 		if (!iwp)
 			continue;
 
-		if (check_online(iwp->path)) {
-			if (!num_ac_online)
-				sys_cond(1);
-
-			if (num_ac_online < num_ac)
-				num_ac_online++;
-		} else {
-			if (num_ac_online > 0)
-				num_ac_online--;
-
-			if (!num_ac_online)
-				sys_cond(0);
+		if (ev->mask & IN_ISDIR) {
+			sys_handle_dir(&iw_sys, iwp->path, ev->name, ev->mask);
+			continue;
 		}
+
+		if (ev->mask & (IN_CREATE | IN_DELETE))
+			sys_update_conds(iwp->path, ev->name, ev->mask);
 	}
 }
 
-static int is_ac(char *path, size_t len)
-{
-	char type[32] = { 0 };
-	char *types[] = {
-		"Mains",
-		"USB",
-		"BrickID",
-		"Wireless",
-		NULL
-	};
-	FILE *fp;
-	int i;
-
-	strlcat(path, "/type", len);
-	fp = fopen(path, "r");
-	if (!fp)
-		return 0;
-
-	if (!fgets(type, sizeof(type), fp)) {
-		fclose(fp);
-		return 0;
-	}
-	fclose(fp);
-
-	for (i = 0; types[i]; i++) {
-		if (!strncmp(type, types[i], strlen(types[i])))
-			return 1;
-	}
-
-	return 0;
-}
-
-/*
- * Called when base filesystem is up, modules have been probed,
- * or insmodded from /etc/finit.conf, so by now we should have
- * /sys/class/power_supply/ available for probing.  If none is
- * found we assert /sys/pwr/ac condition anyway, this is what
- * systemd does (ConditionACPower) and also makes most sense.
- */
 static void sys_init(void *arg)
 {
-	struct dirent **d = NULL;
-	char path[384];
-	int i, n;
+	char sysdir[MAX_ARG_LEN];
+	char *path;
 
-	if (mkpath(pid_runpath(_PATH_CONDSYS, path, sizeof(path)), 0755) && errno != EEXIST) {
+	if (mkpath(pid_runpath(_PATH_CONDSYS, sysdir, sizeof(sysdir)), 0755) && errno != EEXIST) {
 		_pe("Failed creating %s condition directory, %s", COND_SYS, _PATH_CONDSYS);
 		return;
 	}
 
-	n = scandir(_PATH_SYSFS_PWR, &d, NULL, alphasort);
-	if (n <= 0) {
-		iwatch_exit(&iw_sys);
+	path = realpath(_PATH_CONDSYS, NULL);
+	if (!path) {
+		_pe("Cannot figure out real path to %s, aborting", _PATH_CONDSYS);
 		return;
 	}
-		
-	for (i = 0; i < n; i++) {
-		char *nm = d[i]->d_name;
 
-		snprintf(path, sizeof(path), "%s/%s", _PATH_SYSFS_PWR, nm);
-		if (is_ac(path, sizeof(path))) {
-			num_ac++;
-
-			snprintf(path, sizeof(path), "%s/%s/uevent", _PATH_SYSFS_PWR, nm);
-			if (check_online(path))
-				num_ac_online++;
-
-			if (iwatch_add(&iw_sys, path, IN_CLOSE_NOWRITE))
-				_pe("Failed setting up pwr monitor for %s", path);
-		}
-		free(d[i]);
-	}
-	free(d);
-
-	/* if any power_supply is online, or none can be found */
-	if (num_ac == 0 || num_ac_online > 0)
-		sys_cond(1);
+	if (iwatch_add(&iw_sys, path, IN_ONLYDIR))
+		iwatch_exit(&iw_sys);
 }
 
 static plugin_t plugin = {
@@ -206,11 +172,6 @@ PLUGIN_INIT(plugin_init)
 {
 	int fd;
 
-	if (!fisdir(_PATH_SYSFS_PWR)) {
-		_w("System does not have %s, disabling AC power monitor.", _PATH_SYSFS_PWR);
-		return;
-	}
-
 	fd = iwatch_init(&iw_sys);
 	if (fd < 0)
 		return;

src/.gitignore

@@ -1,6 +1,7 @@
 .deps/*
 finit
 initctl
+keventd
 logit
 reboot
 sulogin

src/Makefile.am

@@ -8,18 +8,22 @@ AM_LDFLAGS         = -export-dynamic
 endif
 
 sbin_PROGRAMS        = finit initctl
-pkglibexec_PROGRAMS  = logit sulogin
+pkglibexec_PROGRAMS  = keventd logit sulogin
+if WATCHDOGD
+pkglibexec_PROGRAMS += watchdogd
+endif
+
 finit_pkglibdir      = $(pkglibdir)
 finit_pkglib_SCRIPTS = rescue.conf sample.conf
 
+keventd_SOURCES      = keventd.c iwatch.c iwatch.h util.c util.h
+keventd_CFLAGS       = -W -Wall -Wextra -std=gnu99
+keventd_LDADD        = $(lite_LIBS)
+
 sulogin_SOURCES      = sulogin.c
 sulogin_CFLAGS       = -W -Wall -Wextra -std=gnu99
 sulogin_LDADD        = -lcrypt
 
-if WATCHDOGD
-pkglibexec_PROGRAMS += watchdogd
-endif
-
 logit_SOURCES        = logit.c logrotate.c
 logit_CFLAGS         = -W -Wall -Wextra -Wno-unused-parameter -std=gnu99
 logit_CFLAGS        += $(lite_CFLAGS)

src/finit.c

@@ -594,6 +594,12 @@ int main(int argc, char *argv[])
 		wdog = svc_find_by_nameid("watchdog", "finit");
 	}
 
+	/*
+	 * Start kernel event daemon as soon as possible, if enabled
+	 */
+	if (whichp(FINIT_LIBPATH_ "/keventd"))
+		service_register(SVC_TYPE_SERVICE, "[123456789] cgroup.init " FINIT_LIBPATH_ "/keventd -- Finit kernel event daemon", global_rlimit, NULL);
+
 	/* Base FS up, enable standard SysV init signals */
 	sig_setup(&loop);
 

src/keventd.c

@@ -0,0 +1,278 @@
+/* Listens to kernel events like AC power status and manages sys/ conditions
+ *
+ * Copyright (c) 2021  Joachim Wiberg <troglobit@gmail.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include <errno.h>
+#include <dirent.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdarg.h>
+#include <string.h>
+#include <syslog.h>
+#include <unistd.h>
+
+#include <sys/poll.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+
+#include <linux/types.h>
+#include <linux/netlink.h>
+
+#include "lite/lite.h"
+
+#include "cond.h"
+#include "pid.h"
+#include "util.h"
+
+#define _PATH_SYSFS_PWR  "/sys/class/power_supply"
+
+static int num_ac_online;
+static int num_ac;
+
+int debug;			/* debug in other modules as well */
+
+void logit(int prio, const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	if (!debug)
+		vsyslog(prio, fmt, ap);
+	else {
+		vfprintf(stderr, fmt, ap);
+		fprintf(stderr, "\n");
+	}
+	va_end(ap);
+}
+#define panic(fmt, args...) { logit(LOG_CRIT, fmt ":%s", ##args, strerror(errno)); exit(1); }
+#define warn(fmt, args...)  { logit(LOG_WARNING, fmt ":%s", ##args, strerror(errno)); }
+
+static void sys_cond(char *cond, int set)
+{
+	char oneshot[256];
+
+	snprintf(oneshot, sizeof(oneshot), "%s/%s", _PATH_CONDSYS, cond);
+	if (set) {
+		if (symlink(_PATH_RECONF, oneshot) && errno != EEXIST)
+			warn("failed asserting sys/%s", cond);
+	} else {
+		if (erase(oneshot) && errno != ENOENT)
+			warn("failed asserting sys/%s", cond);
+	}
+}
+
+static int fgetln(char *path, char *buf, size_t len)
+{
+	FILE *fp;
+
+	fp = fopen(path, "r");
+	if (!fp)
+		return -1;
+
+	if (!fgets(buf, len, fp)) {
+		fclose(fp);
+		return -1;
+	}
+
+	chomp(buf);
+	fclose(fp);
+
+	return 0;
+}
+
+static int check_online(char *online)
+{
+	int val;
+
+	if (!online)
+		return 0;
+
+	val = atoi(online);
+	logit(LOG_INFO, "AC %s", val ? "connected" : "disconnected");
+
+	return val;
+}
+
+static int is_ac(char *type)
+{
+	char *types[] = {
+		"Mains",
+		"USB",
+		"BrickID",
+		"Wireless",
+		NULL
+	};
+	int i;
+
+	for (i = 0; types[i]; i++) {
+		if (!strncmp(type, types[i], strlen(types[i])))
+			return 1;
+	}
+
+	return 0;
+}
+
+static void init(void)
+{
+	struct dirent **d = NULL;
+	char *cond_dirs[] = {
+		_PATH_CONDSYS,
+		_PATH_CONDSYS "/pwr",
+	};
+	char path[384];
+	int i, n;
+
+	for (i = 0; i < (int)NELEMS(cond_dirs); i++) {
+		if (mkpath(cond_dirs[i], 0755) && errno != EEXIST) {
+			_pe("Failed creating %s condition directory, %s", COND_SYS,
+			    cond_dirs[i]);
+			return;
+		}
+	}
+
+	n = scandir(_PATH_SYSFS_PWR, &d, NULL, alphasort);
+	for (i = 0; i < n; i++) {
+		char *nm = d[i]->d_name;
+ 		char buf[10];
+
+		snprintf(path, sizeof(path), "%s/%s/type", _PATH_SYSFS_PWR, nm);
+		if (!fgetln(path, buf, sizeof(buf)) && is_ac(buf)) {
+			num_ac++;
+
+			snprintf(path, sizeof(path), "%s/%s/online", _PATH_SYSFS_PWR, nm);
+			if (!fgetln(path, buf, sizeof(buf))) {
+				if (check_online(buf))
+					num_ac_online++;
+			}
+		}
+		free(d[i]);
+	}
+
+	if (n > 0)
+		free(d);
+
+	/* if any power_supply is online, or none can be found */
+	if (num_ac == 0 || num_ac_online > 0)
+		sys_cond("pwr/ac", 1);
+}
+
+/*
+ * Started by Finit as soon as possible when base filesystem is up,
+ * modules have been probed, or insmodded from /etc/finit.conf, so by
+ * now we should have /sys/class/power_supply/ available for probing.
+ * If none is found we assert /sys/pwr/ac condition anyway, this is what
+ * systemd does (ConditionACPower) and also makes most sense.
+ */
+int main(int argc, char *argv[])
+{
+	struct sockaddr_nl nls = { 0 };
+	struct pollfd pfd;
+	char buf[1024];
+
+	if (argc > 1) {
+		if (!strcmp(argv[1], "-d"))
+			debug = 1;
+	}
+
+	if (!debug) {
+		openlog("keventd", LOG_CONS | LOG_PID, LOG_DAEMON);
+		setlogmask(LOG_UPTO(LOG_NOTICE));
+	}
+
+	init();
+
+	pfd.events = POLLIN;
+	pfd.fd = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_KOBJECT_UEVENT);
+	if (pfd.fd == -1)
+		panic("failed creating netlink socket");
+
+	nls.nl_family = AF_NETLINK;
+	nls.nl_pid    = 0;
+	nls.nl_groups = -1;
+	if (bind(pfd.fd, (void *)&nls, sizeof(struct sockaddr_nl)))
+		panic("bind failed");
+
+	logit(LOG_DEBUG, "Waiting for events ...");
+	while (-1 != poll(&pfd, 1, -1)) {
+		char *path = NULL;
+		int ac = 0;
+		int i, len;
+
+		len = recv(pfd.fd, buf, sizeof(buf), MSG_DONTWAIT);
+		if (len == -1) {
+			switch (errno) {
+			case EINTR:
+				continue;
+			case ENOBUFS:
+				warn("lost events");
+				continue;
+			default:
+				panic("unhandled");
+				break;
+			}
+		}
+
+		/* skip libusb events, focus on kernel events/changes */
+		if (strncmp(buf, "change@", 7))
+			continue;
+
+		/* XXX: currently limited to monitoring this subsystem */
+		if (!strstr(buf, "power_supply"))
+			continue;
+
+		i = 0;
+		while (i < len) {
+			char *line = buf + i;
+
+			logit(LOG_DEBUG, "%s", line);
+			if (!strncmp(line, "DEVPATH=", 8)) {
+				path = &line[8];
+				logit(LOG_DEBUG, "Got path %s", path);
+			} else if (!strncmp(line, "POWER_SUPPLY_TYPE=", 18)) {
+				ac = is_ac(&line[18]);
+			} else if (!strncmp(line, "POWER_SUPPLY_ONLINE=", 20) && ac) {
+				if (check_online(&line[20])) {
+					if (!num_ac_online)
+						sys_cond("pwr/ac", 1);
+					num_ac_online++;
+				} else {
+					if (num_ac_online > 0)
+						num_ac_online--;
+					if (!num_ac_online)
+						sys_cond("pwr/ac", 0);
+				}
+			}
+
+			i += strlen(line) + 1;
+		}
+	}
+	close(pfd.fd);
+
+	return 0;
+}
+
+/**
+ * Local Variables:
+ *  indent-tabs-mode: t
+ *  c-file-style: "linux"
+ * End:
+ */