Cannot connect to WPA and Open Network

Asked by Penny Chiu on 2019-12-02

I found some issues, so I am tracing netcfg source code which is downloaded from

I saw netcfg.c has defined the state machine in main loop. Depend on different state, the network interface will be up/down. For example, config a WPA wireless network and with DHCP method, I list the state flow, and the wlan0 status after this state as below:
1. GET_INTERFACE (wlan0 down)
2. WCONFIG (no change)
3. WCONFIG_ESSID (wlan0 is up first. If choose essid from the list, wlan0 will be down; if choose enter essid manually, wlan0 will keep up)
5. WCONFIG_WPA (no change)
6. START_WPA (no change)
7. GET_METHOD (no change)
8. GET_DHCP (wlan0 up)

The issue I encountered is choosing essid from the list, wlan0 will be down, so I could see the below errors in syslog during START_WPA state:

Dec 2 04:37:11 localhost netcfg[8076]: INFO: buf = wpa_state=INTERFACE_DISABLED#012address=00:16:01:80:8a:47#012uuid=c9148e48-dd38-516c-80e
Dec 2 04:37:51 localhost netcfg[8076]: message repeated 8 times: [ INFO: buf = wpa_state=INTERFACE_DISABLED#012address=00:16:01:80:8a:47#0]
Dec 2 04:37:53 localhost wpa_supplicant[4114]: wlan0: CTRL-EVENT-SCAN-FAILED ret=-100

And this causes the configuration is failed. But if I choose enter essid manually, it will be successful because wlan0 keeps up during START_WPA state.

My first question is: Why not keeping the wlan0 is up for both use cases because it needs to send commands to wpa_supplicant daemon during START_WPA state?

Another example is setting Open Network. I choose ‘Open Network’ and left wep key as blank. From syslog, I didn’t see the association with access point during WCONFIG_WEP state. Is this expected?
It will be failed due to wlan is carrier down:

Dec 2 05:22:48 localhost netcfg[6898]: DEBUG: State is now 0
Dec 2 05:22:48 localhost netcfg[6898]: DEBUG: Want link on wlan0
Dec 2 05:22:48 localhost netcfg[6898]: INFO: Waiting time set to 3
Dec 2 05:22:49 localhost netcfg[6898]: INFO: ethtool-lite: wlan0: carrier down
Dec 2 05:22:50 localhost netcfg[6898]: message repeated 5 times: [ INFO: ethtool-lite: wlan0: carrier down]

My second question is: Is this expected without association with access point before doing DHCPDISCOVER?

Thanks a lot.

Question information

English Edit question
Ubuntu netcfg Edit question
No assignee Edit question
Last query:
Last reply:

This question was reopened

What is the output of:

sudo lshw -C network; lsb_release -a; uname -a


Penny Chiu (pchiu) said : #2

       description: Ethernet interface
       product: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
       vendor: Realtek Semiconductor Co., Ltd.
       physical id: 0
       bus info: pci@0000:01:00.0
       logical name: eth0
       version: 15
       serial: 00:04:4b:cc:2e:49
       size: 10Mbit/s
       capacity: 1Gbit/s
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress msix bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation
       configuration: autonegotiation=on broadcast=yes driver=r8168 driverversion=8.045.08-NAPI duplex=half latency=0 link=no multicast=yes port=twisted pair speed=10Mbit/s
       resources: irq:406 ioport:1000(size=256) memory:13004000-13004fff memory:13000000-13003fff
       description: Wireless interface
       product: WLI-U2-KG54
       vendor: Buffalo
       physical id: 3
       bus info: usb@1:2.2.3
       logical name: wlan0
       version: 0.01
       serial: 00:16:01:80:8a:47
       capabilities: usb-2.00 ethernet physical wireless
       configuration: broadcast=yes driver=rt2500usb driverversion=4.9.140-tegra firmware=N/A link=no maxpower=400mA multicast=yes speed=480Mbit/s wireless=IEEE 802.11
       description: Ethernet interface
       physical id: 3
       logical name: rndis0
       serial: fe:99:ee:1d:5f:f1
       capabilities: ethernet physical
       configuration: broadcast=yes driver=g_ether driverversion=29-May-2008 firmware=tegra-xudc link=yes multicast=yes
       description: Ethernet interface
       physical id: 4
       logical name: usb0
       serial: fe:99:ee:1d:5f:f3
       capabilities: ethernet physical
       configuration: broadcast=yes driver=g_ether driverversion=29-May-2008 firmware=tegra-xudc link=yes multicast=yes
       description: Ethernet interface
       physical id: 5
       logical name: l4tbr0
       serial: fe:99:ee:1d:5f:f1
       capabilities: ethernet physical
       configuration: broadcast=yes driver=bridge driverversion=2.3 firmware=N/A ip= link=yes multicast=yes
  *-network:3 DISABLED
       description: Ethernet interface
       physical id: 6
       logical name: dummy0
       serial: 46:1a:14:65:74:19
       capabilities: ethernet physical
       configuration: broadcast=yes driver=dummy driverversion=1.0

Distributor ID: Ubuntu
Description: Ubuntu 18.04.3 LTS
Release: 18.04
Codename: bionic

Linux localhost.localdomain 4.9.140-tegra #7 SMP PREEMPT Thu Nov 28 14:01:51 CST 2019 aarch64 aarch64 aarch64 GNU/Linux

Penny Chiu (pchiu) said : #4

Thanks for reply. But the two links are about how to connect wireless network in desktop environment and using nmcli command tool to config wireless network.

Yes, if we use nmcli to config wireless network, it has no issue to connect WPA and Open network, but we need to use netcfg because it is default wireless configuration tool included in oem-config (ubiquity) package. And the issues are occurred during oem-config debconf_ui process.

I have spent some time to compile and trace netcfg source code to test, can you help to check and answer my original questions?

Thanks a lot.

Launchpad Janitor (janitor) said : #5

This question was expired because it remained in the 'Open' state without activity for the last 15 days.