diff --git a/lnxrouter b/lnxrouter
index d4772d1..fd6497d 100755
--- a/lnxrouter
+++ b/lnxrouter
@@ -192,6 +192,8 @@ define_global_variables(){
 
     # -- variables for running
     CONFDIR=
+    NM_RUNNING=0
+    NM_UNM_LIST=  # it's called "list" but for now one interface
 }
 
 
@@ -737,8 +739,6 @@ haveged_watchdog() {
 
 # only support NetworkManager >= 0.9.9
 nm_initcheck() {
-    NM_RUNNING=0
-    NM_UNM_LIST=
     if (which nmcli >/dev/null 2>&1 ) && (nmcli -t -f RUNNING g 2>&1 | grep -E '^running$' >/dev/null 2>&1 ) ; then
         NM_RUNNING=1
     fi
@@ -1269,6 +1269,8 @@ send_stop() {
 
 ## ========================================================
 ## ========================================================
+# decide linux-router's global temporary path for all instances
+# this is different and should be before config-saving dir. The latter is for one instance
 init_tmpdir(){
     if [[ -d /dev/shm ]]; then
         TMPD=/dev/shm
@@ -1318,90 +1320,84 @@ daemonizing_check(){
 
 #============================
 prepare_wifi() {
-    if [[ $WIFI_IFACE ]]; then
+    if [[ $FREQ_BAND != 2.4 && $FREQ_BAND != 5 ]]; then
+        echo "ERROR: Invalid frequency band" >&2
+        exit 1
+    fi
 
-        if [[ $FREQ_BAND != 2.4 && $FREQ_BAND != 5 ]]; then
-            echo "ERROR: Invalid frequency band" >&2
+    if [[ $CHANNEL == default ]]; then
+        if [[ $FREQ_BAND == 2.4 ]]; then
+            CHANNEL=1
+        else
+            CHANNEL=36
+        fi
+    fi
+
+    if [[ $FREQ_BAND != 5 && $CHANNEL -gt 14 ]]; then
+        echo "Channel number is greater than 14, assuming 5GHz frequency band"
+        FREQ_BAND=5
+    fi
+
+    if ! can_be_ap ${WIFI_IFACE}; then
+        echo "ERROR: Your adapter does not support AP (master) mode" >&2
+        exit 1
+    fi
+
+    if ! can_be_sta_and_ap ${WIFI_IFACE}; then
+        if is_wifi_connected ${WIFI_IFACE}; then
+            echo "ERROR: Your adapter can not be a station (i.e. be connected) and an AP at the same time" >&2
+            exit 1
+        elif [[ $NO_VIRT -eq 0 ]]; then
+            echo "WARN: Your adapter does not fully support AP virtual interface, enabling --no-virt" >&2
+            NO_VIRT=1
+        fi
+    fi
+
+    HOSTAPD=$(which hostapd)
+
+    if [[ $(get_adapter_kernel_module ${WIFI_IFACE}) =~ ^(8192[cd][ue]|8723a[sue])$ ]]; then
+        if ! strings "$HOSTAPD" | grep -m1 rtl871xdrv > /dev/null 2>&1; then
+            echo "ERROR: You need to patch your hostapd with rtl871xdrv patches." >&2
             exit 1
         fi
 
-        if [[ $CHANNEL == default ]]; then
-            if [[ $FREQ_BAND == 2.4 ]]; then
-                CHANNEL=1
-            else
-                CHANNEL=36
-            fi
+        if [[ $DRIVER != "rtl871xdrv" ]]; then
+            echo "WARN: Your adapter needs rtl871xdrv, enabling --driver=rtl871xdrv" >&2
+            DRIVER=rtl871xdrv
         fi
+    fi
+    
+    if [[ ${#SSID} -lt 1 || ${#SSID} -gt 32 ]]; then
+        echo "ERROR: Invalid SSID length ${#SSID} (expected 1..32)" >&2
+        exit 1
+    fi
 
-        if [[ $FREQ_BAND != 5 && $CHANNEL -gt 14 ]]; then
-            echo "Channel number is greater than 14, assuming 5GHz frequency band"
-            FREQ_BAND=5
-        fi
-
-        if ! can_be_ap ${WIFI_IFACE}; then
-            echo "ERROR: Your adapter does not support AP (master) mode" >&2
+    if [[ $USE_PSK -eq 0 ]]; then
+        if [[ ${#PASSPHRASE} -gt 0 && ${#PASSPHRASE} -lt 8 ]] || [[ ${#PASSPHRASE} -gt 63 ]]; then
+            echo "ERROR: Invalid passphrase length ${#PASSPHRASE} (expected 8..63)" >&2
             exit 1
         fi
+    elif [[ ${#PASSPHRASE} -gt 0 && ${#PASSPHRASE} -ne 64 ]]; then
+        echo "ERROR: Invalid pre-shared-key length ${#PASSPHRASE} (expected 64)" >&2
+        exit 1
+    fi
 
-        if ! can_be_sta_and_ap ${WIFI_IFACE}; then
-            if is_wifi_connected ${WIFI_IFACE}; then
-                echo "ERROR: Your adapter can not be a station (i.e. be connected) and an AP at the same time" >&2
-                exit 1
-            elif [[ $NO_VIRT -eq 0 ]]; then
-                echo "WARN: Your adapter does not fully support AP virtual interface, enabling --no-virt" >&2
-                NO_VIRT=1
-            fi
+    if [[ $(get_adapter_kernel_module ${WIFI_IFACE}) =~ ^rtl[0-9].*$ ]]; then
+        if [[ $WPA_VERSION == '1' || $WPA_VERSION == '1+2' ]]; then
+            echo "WARN: Realtek drivers usually have problems with WPA1, WPA2 is recommended" >&2
         fi
-
-        HOSTAPD=$(which hostapd)
-
-        if [[ $(get_adapter_kernel_module ${WIFI_IFACE}) =~ ^(8192[cd][ue]|8723a[sue])$ ]]; then
-            if ! strings "$HOSTAPD" | grep -m1 rtl871xdrv > /dev/null 2>&1; then
-                echo "ERROR: You need to patch your hostapd with rtl871xdrv patches." >&2
-                exit 1
-            fi
-
-            if [[ $DRIVER != "rtl871xdrv" ]]; then
-                echo "WARN: Your adapter needs rtl871xdrv, enabling --driver=rtl871xdrv" >&2
-                DRIVER=rtl871xdrv
-            fi
-        fi
-        
-        if [[ ${#SSID} -lt 1 || ${#SSID} -gt 32 ]]; then
-            echo "ERROR: Invalid SSID length ${#SSID} (expected 1..32)" >&2
-            exit 1
-        fi
-
-        if [[ $USE_PSK -eq 0 ]]; then
-            if [[ ${#PASSPHRASE} -gt 0 && ${#PASSPHRASE} -lt 8 ]] || [[ ${#PASSPHRASE} -gt 63 ]]; then
-                echo "ERROR: Invalid passphrase length ${#PASSPHRASE} (expected 8..63)" >&2
-                exit 1
-            fi
-        elif [[ ${#PASSPHRASE} -gt 0 && ${#PASSPHRASE} -ne 64 ]]; then
-            echo "ERROR: Invalid pre-shared-key length ${#PASSPHRASE} (expected 64)" >&2
-            exit 1
-        fi
-
-        if [[ $(get_adapter_kernel_module ${WIFI_IFACE}) =~ ^rtl[0-9].*$ ]]; then
-            if [[ $WPA_VERSION == '1' || $WPA_VERSION == '1+2' ]]; then
-                echo "WARN: Realtek drivers usually have problems with WPA1, WPA2 is recommended" >&2
-            fi
-            echo "WARN: If AP doesn't work, read https://github.com/oblique/create_ap/blob/master/howto/realtek.md" >&2
-        fi
-
+        echo "WARN: If AP doesn't work, read https://github.com/oblique/create_ap/blob/master/howto/realtek.md" >&2
     fi
 }
 
 check_if_new_mac_valid() {
-    if [[ -n "$NEW_MACADDR" ]]; then
-        if ! is_unicast_macaddr "$NEW_MACADDR"; then
-            echo "ERROR: The first byte of MAC address (${NEW_MACADDR}) must be even" >&2
-            exit 1
-        fi
+    if ! is_unicast_macaddr "$NEW_MACADDR"; then
+        echo "ERROR: The first byte of MAC address (${NEW_MACADDR}) must be even" >&2
+        exit 1
+    fi
 
-        if [[ $(get_all_macaddrs | grep -c ${NEW_MACADDR}) -ne 0 ]]; then
-            echo "WARN: MAC address '${NEW_MACADDR}' already exists" >&2
-        fi
+    if [[ $(get_all_macaddrs | grep -c ${NEW_MACADDR}) -ne 0 ]]; then
+        echo "WARN: MAC address '${NEW_MACADDR}' already exists" >&2
     fi
 }
 
@@ -1434,55 +1430,51 @@ decide_ip_addresses() {
 }
 
 prepare_wifi_interface() {
-    if [[ $WIFI_IFACE ]]; then
+    if [[ $USE_IWCONFIG -eq 0 ]]; then
+        iw dev ${WIFI_IFACE} set power_save off
+    fi
+    
+    if [[ $NO_VIRT -eq 0 ]]; then
+    ## Generate virtual wifi interface
+    
+        VWIFI_IFACE=$(alloc_new_iface)
 
-        if [[ $USE_IWCONFIG -eq 0 ]]; then
-            iw dev ${WIFI_IFACE} set power_save off
-        fi
-        
-        if [[ $NO_VIRT -eq 0 ]]; then
-        ## Generate virtual wifi interface
-        
-            VWIFI_IFACE=$(alloc_new_iface)
-
-            if is_wifi_connected ${WIFI_IFACE}; then
-                WIFI_IFACE_FREQ=$(iw dev ${WIFI_IFACE} link | grep -i freq | awk '{print $2}')
-                WIFI_IFACE_CHANNEL=$(ieee80211_frequency_to_channel ${WIFI_IFACE_FREQ})
-                echo "${WIFI_IFACE} already in channel ${WIFI_IFACE_CHANNEL} (${WIFI_IFACE_FREQ} MHz)"
-                if is_5ghz_frequency $WIFI_IFACE_FREQ; then
-                    FREQ_BAND=5
-                else
-                    FREQ_BAND=2.4
-                fi
-                if [[ $WIFI_IFACE_CHANNEL -ne $CHANNEL ]]; then
-                    echo "Channel fallback to ${WIFI_IFACE_CHANNEL}"
-                    CHANNEL=$WIFI_IFACE_CHANNEL
-                else
-                    echo
-                fi
-            fi
-
-            VIRTDIEMSG="Maybe your WiFi adapter does not fully support virtual interfaces.
-            Try again with --no-virt."
-            echo "Creating a virtual WiFi interface... "
-
-            if iw dev ${WIFI_IFACE} interface add ${VWIFI_IFACE} type __ap; then
-                echo "${VWIFI_IFACE} created."
-                sleep 2
+        if is_wifi_connected ${WIFI_IFACE}; then
+            WIFI_IFACE_FREQ=$(iw dev ${WIFI_IFACE} link | grep -i freq | awk '{print $2}')
+            WIFI_IFACE_CHANNEL=$(ieee80211_frequency_to_channel ${WIFI_IFACE_FREQ})
+            echo "${WIFI_IFACE} already in channel ${WIFI_IFACE_CHANNEL} (${WIFI_IFACE_FREQ} MHz)"
+            if is_5ghz_frequency $WIFI_IFACE_FREQ; then
+                FREQ_BAND=5
             else
-                VWIFI_IFACE=
-                die "$VIRTDIEMSG"
+                FREQ_BAND=2.4
             fi
-            OLD_MACADDR=$(get_macaddr ${VWIFI_IFACE})
-            if [[ -z "$NEW_MACADDR" && $(get_all_macaddrs | grep -c ${OLD_MACADDR}) -ne 1 ]]; then
-                NEW_MACADDR=$(get_new_macaddr ${VWIFI_IFACE})
+            if [[ $WIFI_IFACE_CHANNEL -ne $CHANNEL ]]; then
+                echo "Channel fallback to ${WIFI_IFACE_CHANNEL}"
+                CHANNEL=$WIFI_IFACE_CHANNEL
+            else
+                echo
             fi
-            AP_IFACE=${VWIFI_IFACE}
-        else
-            OLD_MACADDR=$(get_macaddr ${WIFI_IFACE})
-            AP_IFACE=${WIFI_IFACE}
         fi
 
+        VIRTDIEMSG="Maybe your WiFi adapter does not fully support virtual interfaces.
+        Try again with --no-virt."
+        echo "Creating a virtual WiFi interface... "
+
+        if iw dev ${WIFI_IFACE} interface add ${VWIFI_IFACE} type __ap; then
+            echo "${VWIFI_IFACE} created."
+            sleep 2
+        else
+            VWIFI_IFACE=
+            die "$VIRTDIEMSG"
+        fi
+        OLD_MACADDR=$(get_macaddr ${VWIFI_IFACE})
+        if [[ -z "$NEW_MACADDR" && $(get_all_macaddrs | grep -c ${OLD_MACADDR}) -ne 1 ]]; then
+            NEW_MACADDR=$(get_new_macaddr ${VWIFI_IFACE})
+        fi
+        AP_IFACE=${VWIFI_IFACE}
+    else
+        OLD_MACADDR=$(get_macaddr ${WIFI_IFACE})
+        AP_IFACE=${WIFI_IFACE}
     fi
 }
 
@@ -1495,210 +1487,202 @@ decide_subnet_interface() {
 }
 
 write_hostapd_conf() {
-    if [[ $WIFI_IFACE ]]; then
-
-        if [[ -n "$COUNTRY" && $USE_IWCONFIG -eq 0 ]]; then
-            iw reg set "$COUNTRY"
-        fi
-
-        can_transmit_to_channel ${AP_IFACE} ${CHANNEL} || die "Your adapter can not transmit to channel ${CHANNEL}, frequency band ${FREQ_BAND}GHz."
-
-
-        [[ $HIDDEN -eq 1 ]] && echo "Access Point's SSID is hidden!"
-
-        [[ $MAC_FILTER -eq 1 ]] && echo "MAC address filtering is enabled!"
-
-        [[ $ISOLATE_CLIENTS -eq 1 ]] && echo "Access Point's clients will be isolated!"
-
-        # hostapd config
-        cat <<- EOF > "$CONFDIR/hostapd.conf"
-			beacon_int=100
-			ssid=${SSID}
-			interface=${AP_IFACE}
-			driver=${DRIVER}
-			channel=${CHANNEL}
-			ctrl_interface=$CONFDIR/hostapd_ctrl
-			ctrl_interface_group=0
-			ignore_broadcast_ssid=$HIDDEN
-			ap_isolate=$ISOLATE_CLIENTS
-		EOF
-
-        if [[ -n "$COUNTRY" ]]; then
-            cat <<- EOF >> "$CONFDIR/hostapd.conf"
-				country_code=${COUNTRY}
-				ieee80211d=1
-			EOF
-        fi
-
-        if [[ $FREQ_BAND == 2.4 ]]; then
-            echo "hw_mode=g" >> "$CONFDIR/hostapd.conf"
-        else
-            echo "hw_mode=a" >> "$CONFDIR/hostapd.conf"
-        fi
-
-        if [[ $MAC_FILTER -eq 1 ]]; then
-            cat <<- EOF >> "$CONFDIR/hostapd.conf"
-				macaddr_acl=${MAC_FILTER}
-				accept_mac_file=${MAC_FILTER_ACCEPT}
-			EOF
-        fi
-
-        if [[ $IEEE80211N -eq 1 ]]; then
-            cat <<- EOF >> "$CONFDIR/hostapd.conf"
-				ieee80211n=1
-				ht_capab=${HT_CAPAB}
-			EOF
-        fi
-
-        if [[ $IEEE80211AC -eq 1 ]]; then
-            echo "ieee80211ac=1" >> "$CONFDIR/hostapd.conf"
-        fi
-
-        if [[ -n "$VHT_CAPAB" ]]; then
-            echo "vht_capab=${VHT_CAPAB}" >> "$CONFDIR/hostapd.conf"
-        fi
-
-        if [[ $IEEE80211N -eq 1 ]] || [[ $IEEE80211AC -eq 1 ]]; then
-            echo "wmm_enabled=1" >> "$CONFDIR/hostapd.conf"
-        fi
-
-        if [[ -n "$PASSPHRASE" ]]; then
-            [[ "$WPA_VERSION" == "1+2" ]] && WPA_VERSION=3
-            if [[ $USE_PSK -eq 0 ]]; then
-                WPA_KEY_TYPE=passphrase
-            else
-                WPA_KEY_TYPE=psk
-            fi
-            cat <<- EOF >> "$CONFDIR/hostapd.conf"
-				wpa=${WPA_VERSION}
-				wpa_${WPA_KEY_TYPE}=${PASSPHRASE}
-				wpa_key_mgmt=WPA-PSK
-				wpa_pairwise=CCMP
-				rsn_pairwise=CCMP
-			EOF
-        else
-            echo "WARN: Wifi is not protected by password" >&2
-        fi
-        chmod 600 "$CONFDIR/hostapd.conf"
+    if [[ -n "$COUNTRY" && $USE_IWCONFIG -eq 0 ]]; then
+        iw reg set "$COUNTRY"
     fi
+
+    can_transmit_to_channel ${AP_IFACE} ${CHANNEL} || die "Your adapter can not transmit to channel ${CHANNEL}, frequency band ${FREQ_BAND}GHz."
+
+    [[ $HIDDEN -eq 1 ]] && echo "Access Point's SSID is hidden!"
+
+    [[ $MAC_FILTER -eq 1 ]] && echo "MAC address filtering is enabled!"
+
+    [[ $ISOLATE_CLIENTS -eq 1 ]] && echo "Access Point's clients will be isolated!"
+    # TODO: move above code
+        
+    # hostapd config
+    cat <<- EOF > "$CONFDIR/hostapd.conf"
+		beacon_int=100
+		ssid=${SSID}
+		interface=${AP_IFACE}
+		driver=${DRIVER}
+		channel=${CHANNEL}
+		ctrl_interface=$CONFDIR/hostapd_ctrl
+		ctrl_interface_group=0
+		ignore_broadcast_ssid=$HIDDEN
+		ap_isolate=$ISOLATE_CLIENTS
+	EOF
+
+    if [[ -n "$COUNTRY" ]]; then
+        cat <<- EOF >> "$CONFDIR/hostapd.conf"
+			country_code=${COUNTRY}
+			ieee80211d=1
+		EOF
+    fi
+
+    if [[ $FREQ_BAND == 2.4 ]]; then
+        echo "hw_mode=g" >> "$CONFDIR/hostapd.conf"
+    else
+        echo "hw_mode=a" >> "$CONFDIR/hostapd.conf"
+    fi
+
+    if [[ $MAC_FILTER -eq 1 ]]; then
+        cat <<- EOF >> "$CONFDIR/hostapd.conf"
+			macaddr_acl=${MAC_FILTER}
+			accept_mac_file=${MAC_FILTER_ACCEPT}
+		EOF
+    fi
+
+    if [[ $IEEE80211N -eq 1 ]]; then
+        cat <<- EOF >> "$CONFDIR/hostapd.conf"
+			ieee80211n=1
+			ht_capab=${HT_CAPAB}
+		EOF
+    fi
+
+    if [[ $IEEE80211AC -eq 1 ]]; then
+        echo "ieee80211ac=1" >> "$CONFDIR/hostapd.conf"
+    fi
+
+    if [[ -n "$VHT_CAPAB" ]]; then
+        echo "vht_capab=${VHT_CAPAB}" >> "$CONFDIR/hostapd.conf"
+    fi
+
+    if [[ $IEEE80211N -eq 1 ]] || [[ $IEEE80211AC -eq 1 ]]; then
+        echo "wmm_enabled=1" >> "$CONFDIR/hostapd.conf"
+    fi
+
+    if [[ -n "$PASSPHRASE" ]]; then
+        [[ "$WPA_VERSION" == "1+2" ]] && WPA_VERSION=3
+        if [[ $USE_PSK -eq 0 ]]; then
+            WPA_KEY_TYPE=passphrase
+        else
+            WPA_KEY_TYPE=psk
+        fi
+        cat <<- EOF >> "$CONFDIR/hostapd.conf"
+			wpa=${WPA_VERSION}
+			wpa_${WPA_KEY_TYPE}=${PASSPHRASE}
+			wpa_key_mgmt=WPA-PSK
+			wpa_pairwise=CCMP
+			rsn_pairwise=CCMP
+		EOF
+    else
+        echo "WARN: Wifi is not protected by password" >&2
+    fi
+    chmod 600 "$CONFDIR/hostapd.conf"
 }
 
 write_dnsmasq_conf() {
-    if [[ $NO_DNSMASQ -eq 0 ]]; then
-        if grep "^nobody:" /etc/group >/dev/null 2>&1 ; then
-            NOBODY_GROUP="nobody"
+    if grep "^nobody:" /etc/group >/dev/null 2>&1 ; then
+        NOBODY_GROUP="nobody"
+    else
+        NOBODY_GROUP="nogroup"
+    fi
+    cat <<- EOF > "$CONFDIR/dnsmasq.conf"
+		user=nobody
+		group=$NOBODY_GROUP
+		bind-dynamic
+		listen-address=${GATEWAY}
+		interface=$SUBNET_IFACE
+		except-interface=lo
+		no-dhcp-interface=lo
+		dhcp-range=${GATEWAY%.*}.10,${GATEWAY%.*}.250,255.255.255.0
+		dhcp-option-force=option:router,${GATEWAY}
+		#log-dhcp
+		log-facility=/dev/stdout
+		bogus-priv
+		domain-needed
+	EOF
+    # 'log-dhcp'(Extra logging for DHCP) shows too much logs.
+    # if use '-d', 'log-facility' should = /dev/null
+    if [[ $SHARE_METHOD == "none" ]]; then    
+        echo "no-resolv"  >> "$CONFDIR/dnsmasq.conf"
+        echo "no-poll" >> "$CONFDIR/dnsmasq.conf"
+    fi
+    if [[ "$DHCP_DNS" != "no" ]]; then
+        if [[ "$DHCP_DNS" == "gateway" ]]; then
+            dns_offer="$GATEWAY"
         else
-            NOBODY_GROUP="nogroup"
-        fi
-        cat <<- EOF > "$CONFDIR/dnsmasq.conf"
-			user=nobody
-			group=$NOBODY_GROUP
-			bind-dynamic
-			listen-address=${GATEWAY}
-			interface=$SUBNET_IFACE
-			except-interface=lo
-			no-dhcp-interface=lo
-			dhcp-range=${GATEWAY%.*}.10,${GATEWAY%.*}.250,255.255.255.0
-			dhcp-option-force=option:router,${GATEWAY}
-			#log-dhcp
-			log-facility=/dev/stdout
-			bogus-priv
-			domain-needed
-		EOF
-        # 'log-dhcp'(Extra logging for DHCP) shows too much logs.
-        # if use '-d', 'log-facility' should = /dev/null
-        if [[ $SHARE_METHOD == "none" ]]; then    
-            echo "no-resolv"  >> "$CONFDIR/dnsmasq.conf"
-            echo "no-poll" >> "$CONFDIR/dnsmasq.conf"
-        fi
-        if [[ "$DHCP_DNS" != "no" ]]; then
-            if [[ "$DHCP_DNS" == "gateway" ]]; then
-                dns_offer="$GATEWAY"
-            else
-                dns_offer="$DHCP_DNS"
-            fi
-            echo "dhcp-option-force=option:dns-server,${dns_offer}" >> "$CONFDIR/dnsmasq.conf"
-        fi
-        
-        if [[ ! "$dnsmasq_NO_DNS" -eq 0 ]]; then
-            echo "port=0"  >> "$CONFDIR/dnsmasq.conf"
+            dns_offer="$DHCP_DNS"
         fi
+        echo "dhcp-option-force=option:dns-server,${dns_offer}" >> "$CONFDIR/dnsmasq.conf"
+    fi
+    
+    if [[ ! "$dnsmasq_NO_DNS" -eq 0 ]]; then
+        echo "port=0"  >> "$CONFDIR/dnsmasq.conf"
+    fi
 
-        [[ -n "$MTU" ]] && echo "dhcp-option-force=option:mtu,${MTU}" >> "$CONFDIR/dnsmasq.conf"
-        [[ $ETC_HOSTS -eq 0 ]] && echo no-hosts >> "$CONFDIR/dnsmasq.conf"
-        [[ -n "$ADDN_HOSTS" ]] && echo "addn-hosts=${ADDN_HOSTS}" >> "$CONFDIR/dnsmasq.conf"
-        if [[ "$THISHOSTNAME" ]]; then
-            [[ "$THISHOSTNAME" == "-" ]] && THISHOSTNAME="$(cat /etc/hostname)"
-            echo "interface-name=$THISHOSTNAME,$SUBNET_IFACE" >> "$CONFDIR/dnsmasq.conf"
-        fi
-        if [[ ! "$SHOW_DNS_QUERY" -eq 0 ]]; then
-            echo log-queries=extra >> "$CONFDIR/dnsmasq.conf"
-        fi
+    [[ -n "$MTU" ]] && echo "dhcp-option-force=option:mtu,${MTU}" >> "$CONFDIR/dnsmasq.conf"
+    [[ $ETC_HOSTS -eq 0 ]] && echo no-hosts >> "$CONFDIR/dnsmasq.conf"
+    [[ -n "$ADDN_HOSTS" ]] && echo "addn-hosts=${ADDN_HOSTS}" >> "$CONFDIR/dnsmasq.conf"
+    if [[ "$THISHOSTNAME" ]]; then
+        [[ "$THISHOSTNAME" == "-" ]] && THISHOSTNAME="$(cat /etc/hostname)"
+        echo "interface-name=$THISHOSTNAME,$SUBNET_IFACE" >> "$CONFDIR/dnsmasq.conf"
+    fi
+    if [[ ! "$SHOW_DNS_QUERY" -eq 0 ]]; then
+        echo log-queries=extra >> "$CONFDIR/dnsmasq.conf"
+    fi
+    
+    if [[ $DNS ]]; then
+        DNS_count=$(echo "$DNS" | awk -F, '{print NF}')
+        for (( i=1;i<=DNS_count;i++ )); do
+            sep_ip_port "$(echo $DNS | cut -d, -f$i)" DNS_IP DNS_PORT
+            [[ "$DNS_PORT" ]] && DNS_PORT_D="#$DNS_PORT"
+            echo "server=${DNS_IP}${DNS_PORT_D}" >> "$CONFDIR/dnsmasq.conf"
+        done
         
-        if [[ $DNS ]]; then
-            DNS_count=$(echo "$DNS" | awk -F, '{print NF}')
-            for (( i=1;i<=DNS_count;i++ )); do
-                sep_ip_port "$(echo $DNS | cut -d, -f$i)" DNS_IP DNS_PORT
-                [[ "$DNS_PORT" ]] && DNS_PORT_D="#$DNS_PORT"
-                echo "server=${DNS_IP}${DNS_PORT_D}" >> "$CONFDIR/dnsmasq.conf"
-            done
-            
-            cat <<- EOF >> "$CONFDIR/dnsmasq.conf"
-				no-resolv
-				no-poll
-			EOF
-        fi
-        if [[ $IPV6 -eq 1 ]];then
-            cat <<- EOF  >> "$CONFDIR/dnsmasq.conf"
-				listen-address=${GATEWAY6}
-				enable-ra
-				#quiet-ra
-				dhcp-range=interface:${SUBNET_IFACE},::,::ffff:ffff:ffff:ffff,constructor:${SUBNET_IFACE},ra-stateless,64
-			EOF
-            if [[ "$DHCP_DNS6" != "no" ]]; then
-                if [[ "$DHCP_DNS6" == "gateway" ]]; then
-                    dns_offer6="[$GATEWAY6]"
-                else
-                    dns_offer6="$DHCP_DNS6"
-                fi
-                echo "dhcp-option=option6:dns-server,${dns_offer6}" >> "$CONFDIR/dnsmasq.conf"
+        cat <<- EOF >> "$CONFDIR/dnsmasq.conf"
+			no-resolv
+			no-poll
+		EOF
+    fi
+    if [[ $IPV6 -eq 1 ]];then
+        cat <<- EOF  >> "$CONFDIR/dnsmasq.conf"
+			listen-address=${GATEWAY6}
+			enable-ra
+			#quiet-ra
+			dhcp-range=interface:${SUBNET_IFACE},::,::ffff:ffff:ffff:ffff,constructor:${SUBNET_IFACE},ra-stateless,64
+		EOF
+        if [[ "$DHCP_DNS6" != "no" ]]; then
+            if [[ "$DHCP_DNS6" == "gateway" ]]; then
+                dns_offer6="[$GATEWAY6]"
+            else
+                dns_offer6="$DHCP_DNS6"
             fi
+            echo "dhcp-option=option6:dns-server,${dns_offer6}" >> "$CONFDIR/dnsmasq.conf"
         fi
     fi
 }
 
 run_wifi_ap_processes() {
-    if [[ $WIFI_IFACE ]]; then
-
-        if [[ $NO_HAVEGED -eq 0 ]]; then
-            haveged_watchdog &
-            HAVEGED_WATCHDOG_PID=$!
-            echo "$HAVEGED_WATCHDOG_PID" > "$CONFDIR/haveged_watchdog.pid"
-            echo "haveged_watchdog PID: $HAVEGED_WATCHDOG_PID" 
-        fi
-
-        # start access point
-        #echo "hostapd command-line interface: hostapd_cli -p $CONFDIR/hostapd_ctrl"
-        # start hostapd (use stdbuf when available for no delayed output in programs that redirect stdout)
-        STDBUF_PATH=`which stdbuf`
-        if [ $? -eq 0 ]; then
-            STDBUF_PATH=$STDBUF_PATH" -oL"
-        fi
-        echo 
-        echo "Starting hostapd"
-        # hostapd '-P' works only when use '-B' (run in background)
-        $STDBUF_PATH hostapd $HOSTAPD_DEBUG_ARGS -P "$CONFDIR/hostapd.pid" "$CONFDIR/hostapd.conf"  &
-        HOSTAPD_PID=$!
-        echo "$HOSTAPD_PID" > "$CONFDIR/hostapd.pid"
-        echo "hostapd PID: $HOSTAPD_PID"
-        #while [[ ! -f $CONFDIR/hostapd.pid ]]; do
-        #    sleep 1
-        #done
-        #echo -n "hostapd PID: " ; cat $CONFDIR/hostapd.pid
-        ( while [ -e /proc/$HOSTAPD_PID ]; do sleep 10; done ; die "hostapd exited" ) &
-
-        sleep 3
+    if [[ $NO_HAVEGED -eq 0 ]]; then
+        haveged_watchdog &
+        HAVEGED_WATCHDOG_PID=$!
+        echo "$HAVEGED_WATCHDOG_PID" > "$CONFDIR/haveged_watchdog.pid"
+        echo "haveged_watchdog PID: $HAVEGED_WATCHDOG_PID" 
     fi
+
+    # start access point
+    #echo "hostapd command-line interface: hostapd_cli -p $CONFDIR/hostapd_ctrl"
+    # start hostapd (use stdbuf when available for no delayed output in programs that redirect stdout)
+    STDBUF_PATH=`which stdbuf`
+    if [ $? -eq 0 ]; then
+        STDBUF_PATH=$STDBUF_PATH" -oL"
+    fi
+    echo 
+    echo "Starting hostapd"
+    # hostapd '-P' works only when use '-B' (run in background)
+    $STDBUF_PATH hostapd $HOSTAPD_DEBUG_ARGS -P "$CONFDIR/hostapd.pid" "$CONFDIR/hostapd.conf"  &
+    HOSTAPD_PID=$!
+    echo "$HOSTAPD_PID" > "$CONFDIR/hostapd.pid"
+    echo "hostapd PID: $HOSTAPD_PID"
+    #while [[ ! -f $CONFDIR/hostapd.pid ]]; do
+    #    sleep 1
+    #done
+    #echo -n "hostapd PID: " ; cat $CONFDIR/hostapd.pid
+    ( while [ -e /proc/$HOSTAPD_PID ]; do sleep 10; done ; die "hostapd exited" ) &
+
+    sleep 3
 }
 
 backup_interface_ipv6_status() {
@@ -1713,8 +1697,10 @@ backup_interface_ipv6_status() {
         echo 0 > "/proc/sys/net/ipv6/conf/$SUBNET_IFACE/use_tempaddr"
         echo 0 > "/proc/sys/net/ipv6/conf/$SUBNET_IFACE/addr_gen_mode"
         
-        ip -6 addr add ${GATEWAY6}/64  dev ${SUBNET_IFACE} || die "Failed setting ${SUBNET_IFACE} IPv6"
+        # TODO: move this code
+        ip -6 addr add ${GATEWAY6}/64  dev ${SUBNET_IFACE} || die "Failed setting ${SUBNET_IFACE} IPv6 address"
     else
+        # TODO: also need to deal with "disable_ipv6" if ipv6 is enabled using this script
         cp "/proc/sys/net/ipv6/conf/$SUBNET_IFACE/disable_ipv6"  "$CONFDIR/sys_6_conf_iface/"
         echo 1 > "/proc/sys/net/ipv6/conf/$SUBNET_IFACE/disable_ipv6"
     fi
@@ -1722,72 +1708,69 @@ backup_interface_ipv6_status() {
 
 
 start_dnsmasq() {
-    if [[ $NO_DNSMASQ -eq 0 ]]; then
-        start_dhcp
-
-        if which complain > /dev/null 2>&1; then
-            # openSUSE's apparmor does not allow dnsmasq to read files.
-            # remove restriction.
-            complain dnsmasq
-        fi
-
-        echo 
-        echo "Starting dnsmasq"
-        # Using '-d'(no daemon) dnsmasq will not turn into 'nobody'
-        # '-x' works only when no '-d'
-        dnsmasq  -k -C "$CONFDIR/dnsmasq.conf" -x "$CONFDIR/dnsmasq.pid" -l "$CONFDIR/dnsmasq.leases" & 
-        #####DNSMASQ_PID=$!         # only when with '-d'
-        ######echo "dnsmasq PID: $DNSMASQ_PID"      # only when with '-d'
-        i=0; while [[ ! -f "$CONFDIR/dnsmasq.pid" ]]; do
-            sleep 1
-            i=$((i + 1))
-            if [[ $i -gt 10 ]]; then die "Couldn't get dnsmasq PID" ; fi
-        done
-        echo -n "dnsmasq PID: " ; cat "$CONFDIR/dnsmasq.pid"
-        ######(wait $DNSMASQ_PID ; die "dnsmasq failed") &  # wait can't deal with non-child
-        ( while [ -e "/proc/$DNSMASQ_PID" ]; do sleep 10; done ; die "dnsmasq exited" ) &
-        sleep 2
+    start_dhcp
 
+    if which complain > /dev/null 2>&1; then
+        # openSUSE's apparmor does not allow dnsmasq to read files.
+        # remove restriction.
+        complain dnsmasq
     fi
+
+    echo 
+    echo "Starting dnsmasq"
+    # Using '-d'(no daemon) dnsmasq will not turn into 'nobody'
+    # '-x' works only when no '-d'
+    dnsmasq  -k -C "$CONFDIR/dnsmasq.conf" -x "$CONFDIR/dnsmasq.pid" -l "$CONFDIR/dnsmasq.leases" & 
+    #####DNSMASQ_PID=$!         # only when with '-d'
+    ######echo "dnsmasq PID: $DNSMASQ_PID"      # only when with '-d'
+    i=0; while [[ ! -f "$CONFDIR/dnsmasq.pid" ]]; do
+        sleep 1
+        i=$((i + 1))
+        if [[ $i -gt 10 ]]; then die "Couldn't get dnsmasq PID" ; fi
+    done
+    echo -n "dnsmasq PID: " ; cat "$CONFDIR/dnsmasq.pid"
+    ######(wait $DNSMASQ_PID ; die "dnsmasq failed") &  # wait can't deal with non-child
+    ( while [ -e "/proc/$DNSMASQ_PID" ]; do sleep 10; done ; die "dnsmasq exited" ) &
+    sleep 2
 }
 
 check_if_need_rfkill_unblock_wifi() {
-    if [[ $WIFI_IFACE ]]; then
-        if which rfkill > /dev/null 2>&1 ; then
-            PHY=$(get_phy_device ${SUBNET_IFACE})
-            [[ -n $PHY ]] && rfkill unblock $(rfkill | grep $PHY | awk '{print $1}') >/dev/null 2>&1
-        fi
+    if which rfkill > /dev/null 2>&1 ; then
+        PHY=$(get_phy_device ${SUBNET_IFACE})
+        [[ -n $PHY ]] && rfkill unblock $(rfkill | grep $PHY | awk '{print $1}') >/dev/null 2>&1
     fi
 }
 
 #=========== Above are functions ======================
 #=========== Executing begin ==============================
 
-# show usage and exit if empty option
+# if empty option, show usage and exit 
 check_empty_option "$@"
 
-# TODO: some global variables are still defined in those following code
+# TODO: are some global variables are still defined in those following code?
 define_global_variables
 
 ARGS=( "$@" )
 
 parse_user_options "$@"
 
+# check if networkManager running
 nm_initcheck
 
 init_tmpdir
 
-# will exit after this if user choose to deal with running instances
+# if user choose to deal with running instances, will exit after this 
 check_other_functions 
 
-# will start new background process and exit this if user choose to daemonize
+# if user choose to daemonize, will start new background process and exit this 
 daemonizing_check
 
-prepare_wifi
+# check if wifi will work on this system and user settings
+[[ $WIFI_IFACE ]] && prepare_wifi
 
 [[ "$USE_RANDOM_MAC" -eq 1 ]] && generate_random_mac 
 
-check_if_new_mac_valid
+[[ -n "$NEW_MACADDR" ]] && check_if_new_mac_valid
 
 # checks finished
 
@@ -1801,16 +1784,14 @@ decide_target_interface
 
 decide_ip_addresses
 
-if [[ $TP_PORT ]]; then
-    SHARE_METHOD=redsocks
-fi
+# TODO: should this be some other place?
+[[ $TP_PORT ]] && SHARE_METHOD=redsocks
 
-if [[ $DHCP_DNS != 'gateway' && $DHCP_DNS6 != 'gateway' ]]; then
-    dnsmasq_NO_DNS=1
-fi
+# if user choose to make DHCP to tell clients to use other DNS, we don't have to serve DNS
+[[ $DHCP_DNS != 'gateway' && $DHCP_DNS6 != 'gateway' ]] && dnsmasq_NO_DNS=1
 
-#=================
-# begin to do some change on config files and system
+#===========================================================
+#==== begin to do some change on config files and system===
 
 trap "cleanup" EXIT
 trap "clean_exit" SIGINT SIGUSR1 SIGTERM
@@ -1829,38 +1810,46 @@ echo $$ > "$CONFDIR/pid"
 COMMON_CONFDIR="$TMPDIR/lnxrouter_common.conf"
 mkdir -p "$COMMON_CONFDIR"
 
-prepare_wifi_interface
+[[ $WIFI_IFACE ]] && prepare_wifi_interface
 
 decide_subnet_interface
 
 echo "$SUBNET_IFACE" > "$CONFDIR/subn_iface"
 
-write_hostapd_conf
+[[ $WIFI_IFACE ]] && write_hostapd_conf
 #===================================================
 #===================================================
 
+# set interface unmanaged by networkManager
 if [[ $NM_RUNNING -eq 1 ]] && nm_knows $TARGET_IFACE ; then
     nm_set_unmanaged ${SUBNET_IFACE}
 fi
 
-write_dnsmasq_conf
+[[ $NO_DNSMASQ -eq 0 ]] && write_dnsmasq_conf
 #===========================
 
 # initialize subnet interface
+# put subnet interface down first
 ip link set down dev ${SUBNET_IFACE} || die "Failed setting ${SUBNET_IFACE} down"
+# flush IPs of subnet interface
 ip addr flush ${SUBNET_IFACE} || die "Failed flush ${SUBNET_IFACE} IP"
 
-if [[  -n "$NEW_MACADDR" ]]; then
+# set subnet mac if needed
+if [[ -n "$NEW_MACADDR" ]] ; then
     ip link set dev ${SUBNET_IFACE} address ${NEW_MACADDR} || die "Failed setting new MAC address"
 fi
 
-check_if_need_rfkill_unblock_wifi
+[[ $WIFI_IFACE ]] && check_if_need_rfkill_unblock_wifi
 
+# bring subnet interface up
 ip link set up dev ${SUBNET_IFACE} || die "Failed bringing ${SUBNET_IFACE} up"
 
-run_wifi_ap_processes
+# hostapd , haveged
+[[ $WIFI_IFACE ]] && run_wifi_ap_processes
 
-ip addr add ${GATEWAY}/24 broadcast ${GATEWAY%.*}.255 dev ${SUBNET_IFACE} || die "Failed setting ${SUBNET_IFACE} IP"
+# add ipv4 address to subnet interface
+# TODO: move ipv6 code here
+ip addr add ${GATEWAY}/24 broadcast ${GATEWAY%.*}.255 dev ${SUBNET_IFACE} || die "Failed setting ${SUBNET_IFACE} IPv4 address"
 
 backup_interface_ipv6_status
 
@@ -1891,13 +1880,13 @@ fi
 
 # start dhcp + dns (optional)
 
-if [[ "$DHCP_DNS" == "gateway" || "$DHCP_DNS6" == "gateway" ]]; then
-    allow_dns_port
-fi
+# allow dns port input even if we don't run dnsmasq
+# user can serve their own dns server
+[[ "$DHCP_DNS" == "gateway" || "$DHCP_DNS6" == "gateway" ]] && allow_dns_port
 
 [[ "$CATCH_DNS" -eq 1 ]] && start_catch_dns
 
-start_dnsmasq
+[[ $NO_DNSMASQ -eq 0 ]] && start_dnsmasq
 
 echo 
 echo "== Setting up completed, now linux-router is working =="