From 56f73937adfbb3dfd7f69a6b08427d59e3be0e19 Mon Sep 17 00:00:00 2001
From: Jakub Jirutka <jakub@jirutka.cz>
Date: Tue, 14 Jun 2022 15:21:47 +0200
Subject: [PATCH] resolver: Add path to resolv.conf to config options

---
 doc/connman.conf.5.in |  8 ++++++++
 src/main.c            | 16 ++++++++++++++++
 src/resolver.c        | 33 ++++++++++++++++++++++++++-------
 3 files changed, 50 insertions(+), 7 deletions(-)

diff --git a/doc/connman.conf.5.in b/doc/connman.conf.5.in
index 82cceb72..16158f94 100644
--- a/doc/connman.conf.5.in
+++ b/doc/connman.conf.5.in
@@ -205,6 +205,14 @@ address will be chosen instead (according to RFC3927). If an address conflict
 occurs for an address offered via DHCP, ConnMan send a DHCP DECLINE once and
 for the second conflict resort to finding an IPv4LL address.
 Default value is false.
+.TP
+.BI ResolvConf= string
+Path to resolv.conf file. If the file does not exist, but intermediate
+directories exist, it will be created.
+If this option is not set, it tries to write into
+@runstatedir@/connman/resolv.conf and fallbacks to @sysconfdir@/resolv.conf if
+it fails (@runstatedir@/connman does not exist or is not writeable).
+If you do not want to update resolv.conf, you can set /dev/null.
 .SH "EXAMPLE"
 The following example configuration disables hostname updates and enables
 ethernet tethering.
diff --git a/src/main.c b/src/main.c
index e209cf26..57d3d0d5 100644
--- a/src/main.c
+++ b/src/main.c
@@ -107,6 +107,7 @@ static struct {
 	bool auto_connect_roaming_services;
 	bool acd;
 	bool use_gateways_as_timeservers;
+	char *resolv_conf;
 } connman_settings  = {
 	.bg_scan = true,
 	.pref_timeservers = NULL,
@@ -134,6 +135,7 @@ static struct {
 	.auto_connect_roaming_services = false,
 	.acd = false,
 	.use_gateways_as_timeservers = false,
+	.resolv_conf = NULL,
 };
 
 #define CONF_BG_SCAN                    "BackgroundScanning"
@@ -162,6 +164,7 @@ static struct {
 #define CONF_AUTO_CONNECT_ROAMING_SERVICES "AutoConnectRoamingServices"
 #define CONF_ACD                        "AddressConflictDetection"
 #define CONF_USE_GATEWAYS_AS_TIMESERVERS "UseGatewaysAsTimeservers"
+#define CONF_RESOLV_CONF                "ResolvConf"
 
 static const char *supported_options[] = {
 	CONF_BG_SCAN,
@@ -190,6 +193,7 @@ static const char *supported_options[] = {
 	CONF_AUTO_CONNECT_ROAMING_SERVICES,
 	CONF_ACD,
 	CONF_USE_GATEWAYS_AS_TIMESERVERS,
+	CONF_RESOLV_CONF,
 	NULL
 };
 
@@ -565,6 +569,15 @@ static void parse_config(GKeyFile *config)
 		connman_settings.use_gateways_as_timeservers = boolean;
 
 	g_clear_error(&error);
+
+	string = __connman_config_get_string(config, "General",
+				CONF_RESOLV_CONF, &error);
+	if (!error)
+		connman_settings.resolv_conf = string;
+	else
+		g_free(string);
+
+	g_clear_error(&error);
 }
 
 static int config_init(const char *file)
@@ -793,6 +806,9 @@ bool connman_setting_get_bool(const char *key)
 	if (g_str_equal(key, CONF_USE_GATEWAYS_AS_TIMESERVERS))
 		return connman_settings.use_gateways_as_timeservers;
 
+	if (g_str_equal(key, CONF_RESOLV_CONF))
+		return connman_settings.resolv_conf;
+
 	return false;
 }
 
diff --git a/src/resolver.c b/src/resolver.c
index 618353fd..4ab51d6b 100644
--- a/src/resolver.c
+++ b/src/resolver.c
@@ -103,6 +103,7 @@ static int resolvfile_export(void)
 	int fd, err;
 	unsigned int count;
 	mode_t old_umask;
+	const char *resolv_conf;
 
 	content = g_string_new("# Generated by Connection Manager\n");
 
@@ -161,15 +162,33 @@ static int resolvfile_export(void)
 
 	old_umask = umask(022);
 
-	fd = open(RESOLV_CONF_STATEDIR, O_RDWR | O_CREAT | O_CLOEXEC,
-					S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
-	if (fd < 0) {
-		connman_warn_once("Cannot create "RESOLV_CONF_STATEDIR" "
-			"falling back to "RESOLV_CONF_ETC);
+	resolv_conf = connman_setting_get_string("ResolvConf");
+	/*
+	 * TODO: This is mainly for backward compatibility. In some future version,
+	 * "ResolvConf" setting should default to RESOLV_CONF_STATEDIR or
+	 * RESOLV_CONF_ETC and this branch can be removed.
+	 */
+	if (resolv_conf == NULL) {
+		fd = open(RESOLV_CONF_STATEDIR, O_RDWR | O_CREAT | O_CLOEXEC,
+						S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
+		if (fd < 0) {
+			connman_warn_once("Cannot create "RESOLV_CONF_STATEDIR" "
+				"falling back to "RESOLV_CONF_ETC);
 
-		fd = open(RESOLV_CONF_ETC, O_RDWR | O_CREAT | O_CLOEXEC,
-					S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
+			fd = open(RESOLV_CONF_ETC, O_RDWR | O_CREAT | O_CLOEXEC,
+						S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
 
+			if (fd < 0) {
+				err = -errno;
+				goto done;
+			}
+		}
+	} else if (resolv_conf[0] == '\0' || strcmp(resolv_conf, "/dev/null") == 0) {
+		err = 0;
+		goto done;
+	} else {
+		fd = open(resolv_conf, O_RDWR | O_CREAT | O_CLOEXEC,
+						S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
 		if (fd < 0) {
 			err = -errno;
 			goto done;
-- 
2.16.4