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I've got a clean installation of CentOS 7 on a desktop PC and a USB WiFI Adapter (RTL8191SU 802.11n). Connecting through USB leads shows "USB Ethernet: connecting" in Gnome3's network status bar.

lsusb says:

Bus 003 Device 004: ID 0bda:8172 Realtek Semiconductor Corp. RTL8191SU 802.11n WLAN Adapter

grep -e "usb" /var/log/messages:

...
Jun 15 08:01:01 localhost kernel: usb 3-12: new high-speed USB device number 4 using xhci_hcd
Jun 15 08:01:01 localhost kernel: usb 3-12: New USB device found, idVendor=0bda, idProduct=8172
Jun 15 08:01:01 localhost kernel: usb 3-12: New USB device strings: Mfr=1, Product=2, SerialNumber=3
Jun 15 08:01:01 localhost kernel: usb 3-12: Product: RTL8191S WLAN Adapter
Jun 15 08:01:01 localhost kernel: usb 3-12: Manufacturer: Manufacturer Realtek
Jun 15 08:01:01 localhost kernel: usb 3-12: SerialNumber: 00e04c000001
Jun 15 08:01:01 localhost mtp-probe: checking bus 3, device 4: "/sys/devices/pci0000:00/0000:00:14.0/usb3/3-12"
Jun 15 08:01:01 localhost kernel: usb 3-12: r8712u: USB_SPEED_HIGH with 4 endpoints
Jun 15 08:01:01 localhost kernel: usb 3-12: r8712u: Boot from EFUSE: Autoload OK
Jun 15 08:01:02 localhost kernel: usb 3-12: r8712u: CustomerID = 0x000a
Jun 15 08:01:02 localhost kernel: usb 3-12: r8712u: MAC Address from efuse = 24:05:0f:36:27:cd
Jun 15 08:01:02 localhost kernel: usb 3-12: r8712u: Loading firmware from "rtlwifi/rtl8712u.bin"
Jun 15 08:01:02 localhost kernel: usbcore: registered new interface driver r8712u

grep -e "r8712u" /var/log/messages:

Jun 15 08:01:01 localhost kernel: r8712u: module is from the staging directory, the quality is unknown, you have been warned.
Jun 15 08:01:01 localhost kernel: r8712u: Staging version
Jun 15 08:01:01 localhost kernel: r8712u: register rtl8712_netdev_ops to netdev_ops
Jun 15 08:01:01 localhost kernel: usb 3-12: r8712u: USB_SPEED_HIGH with 4 endpoints
Jun 15 08:01:01 localhost kernel: usb 3-12: r8712u: Boot from EFUSE: Autoload OK
Jun 15 08:01:02 localhost kernel: usb 3-12: r8712u: CustomerID = 0x000a
Jun 15 08:01:02 localhost kernel: usb 3-12: r8712u: MAC Address from efuse = 24:05:0f:36:27:cd
Jun 15 08:01:02 localhost kernel: usb 3-12: r8712u: Loading firmware from "rtlwifi/rtl8712u.bin"
Jun 15 08:01:02 localhost kernel: usbcore: registered new interface driver r8712u
Jun 15 08:01:02 localhost NetworkManager[895]: (enp0s20u12): driver 'r8712u' does not support carrier detection.
Jun 15 08:01:02 localhost NetworkManager[895]: (enp0s20u12): new Ethernet device (driver: 'r8712u' ifindex: 3)
Jun 15 08:01:02 localhost kernel: r8712u 3-12:1.0 enp0s20u12: 1 RCR=0x153f00e
Jun 15 08:01:02 localhost kernel: r8712u 3-12:1.0 enp0s20u12: 2 RCR=0x553f00e

Obviously it loads the r8712u driver, but how do I know if it's the right one and if it is - how can I view it's logs or debug it?

Edit: Ubuntu 14.04 LiveUSB loads the same driver and WiFi works out of the box. dmesg in CentOS shows:

IPv6: ADDRCONF(NETDEV_UP): enp0s20u12: link is not ready
IPv6: ADDRCONF(NETDEV_UP): enp0s20u12: link is not ready
IPv6: ADDRCONF(NETDEV_UP): enp0s20u12: link is not ready

while in Ubuntu the link becomes ready eventually:

IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
..
IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready

What gives?

nmcli c sh on CentOS prints:

Wired connection 1 e6c22a72-98c3-4e6e-ad31-5a6ace6db913 802-3-ethernet --
Wired connection 2 950c52f5-fb7a-4349-900e-14a28fa9e688 802-3-ethernet --

While in Ubuntu, after connecting to WiFi nmcli c shows:

mywifi 8d0af4ff-370d-42bd-b824-425571128df1 802-11-wireless Mon 15 Jun 2015 01:08:42 PM UTC
Wired connection 1 e466d3b5-dc88-4438-909f-7e7f56588897 802-3-ethernet Mon 15 Jun 2015 01:06:23 PM UTC

Which obviously means that CentOS recognizes the dongle as wired connection. I've installed the latest kernel (4.0.5-1) from elrepo and now the connection shows up as "USB unknown, unmanaged" in Network Manager. The same firmware is still being loaded, but nothing else happens. Where can I go from here ? PS: There is a official driver on Realtek's website, but I cannot compile it (seems like it's too old)

  • Have you solved the problem? – yO_ Apr 26 '17 at 15:02
  • Nope, decided to go with ubuntu because of several such issues – tesseract Apr 26 '17 at 17:26
  • Okay, thanks. A little amazing because of CentOS's reputation of stability! – yO_ Apr 26 '17 at 17:35
1

I think you should use wpa_supplicant instead of NetworkManager.

There are some posts describe this bug, like here. Some post concluded it as solved and some one as unsolved. I just failed to figure it out how to setup NetworkManager to work with my usb wifi stick.

I use CentOS7 3.10.0-514.10.2.el7.x86_64, and a TP-link TL-WDN5200 usb wifi stick with a mt7610u inside.

  1. After I installed the driver, I connnected it to my wifi by: sudo wpa_passphrase xdhtc >> /etc/wpa_supplicant.conf # type in the passphrase and hit enter sudo wpa_supplicant -B -Dwext -ira0 -c/etc/wpa_supplicant.conf # -B background sudo dhclient ra0

You may also try iw instead of wpa_supplicant if your wifi chip support nl80211.

  1. You may also want to make sure NetworkManager does not manage this wireless network. I tried to let NetworkManager and wpa_supplicant work in parallel. They will work without big problems, but the interface status is obviously not sync. So I add these lines in /etc/NetworkManager/NetworkManager.conf to configure NM ignore my wifi connection:

    [main]
    plugins=keyfile
    [keyfile]
    unmanaged-devices=interface-name:ra0

  2. I put this script under ~/.config/autostart/ to make the wifi starts with the OS, and configured only one ip through this wireless connection.

    sudo wpa_supplicant -B -Dwext -ira0 -c/etc/wpa_supplicant.conf
    sudo dhclient ra0
    sudo ip r add xx.xx.xx.xx via 192.168.2.1 dev ra0
    sudo ip r del default via 192.168.2.1 dev ra0

Please tell me if there is any elegant way to solve this problem.

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