vpnc: Control IPv6 data leak prevention with additional option

[vpnc] Control IPv6 data leak prevention with additional option. JB#53542

Add "VPNC.BlockIPv6" option for VPNC to control the IPv6 data leak
prevention feature. If omitted default to false and require the feature
to be explicitly set to true.

VPNC does not have a separate option that is to be used but for
convenience is saved along the VPNC provider configuration.

connman/vpn/plugins/vpnc.c

@@ -91,6 +91,7 @@ struct {
 	{ "VPNC.SingleDES", "Enable Single DES", NULL, OPT_BOOLEAN, true },
 	{ "VPNC.NoEncryption", "Enable no encryption", NULL, OPT_BOOLEAN,
 									true },
+	{ "VPNC.BlockIPv6", "BlockIPv6", NULL, OPT_BOOLEAN, true},
 };
 
 struct vc_private_data {
@@ -314,6 +315,7 @@ static ssize_t write_bool_option(int fd, const char *key, const char *value)
 static int vc_write_config_data(struct vpn_provider *provider, int fd)
 {
 	const char *opt_s;
+	bool block_ipv6 = false;
 	int i;
 
 	for (i = 0; i < (int)ARRAY_SIZE(vpnc_options); i++) {
@@ -325,6 +327,12 @@ static int vc_write_config_data(struct vpn_provider *provider, int fd)
 		if (!opt_s)
 			continue;
 
+		if (g_strcmp0(opt_s, "VPNC.BlockIPv6") && !g_ascii_strcasecmp(
+					vpnc_options[i].vpnc_opt, "true")) {
+			block_ipv6 = true;
+			continue;
+		}
+
 		if (vpnc_options[i].type == OPT_STRING) {
 			if (write_option(fd,
 					vpnc_options[i].vpnc_opt, opt_s) < 0)
@@ -337,6 +345,8 @@ static int vc_write_config_data(struct vpn_provider *provider, int fd)
 
 	}
 
+	vpn_provider_set_supported_ip_networks(provider, true, !block_ipv6);
+
 	return 0;
 }