Reconnect WLAN

[BjoernS]

Hi,
I have a problem reconnecting the WLAN.

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ifconfig wlan0 down

brings down the interface, but neither

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ifconfig wlan0 up

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ifup wlan0

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wpa_cli -i wlan0 reconfigure

brings it up again.

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ip a

shows:

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2: wlan0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN gr default qlen 1000
    link/ether 74:da:38:65:3d:27 brd ff:ff:ff:ff:ff:ff

lsusb:

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Bus 001 Device 003: ID 7392:7811 Edimax Technology Co., Ltd EW-7811Un 802.11n Wireless Adapter [Realtek RTL8188CUS]

[epoch1970]

The old ifconfig has been obsoleted by “ip” commands.
“ip link set dev <dev> down” is the replacement for “ifconfig <dev> down”
https://baturin.org/docs/iproute2/

ifupdown is even more obsolete, do not use “ifup” or “ifdown” unless you know why.

Try “ip link <dev> up” and then see if the interface reacquires carrier through wpa_supplicant.

[BjoernS]

Thank you, but that also doesn´t work.
But I see some error trace in ther kernel log:
[ 120.103235] ------------[ cut here ]------------
[ 120.104048] WARNING: CPU: 0 PID: 20 at net/wireless/sme.c:981 __cfg80211_disconnected+0x334/0x374 [cfg80211]
[ 120.104059] Modules linked in: 8192cu cfg80211 rfkill snd_bcm2835(C) snd_pcm snd_timer snd uio_pdrv_genirq fixed uio ip_tables x_tables ipv6
[ 120.104115] CPU: 0 PID: 20 Comm: kworker/u2:1 Tainted: G C 4.14.79+ #1159
[ 120.104119] Hardware name: BCM2835
[ 120.104816] Workqueue: cfg80211 cfg80211_event_work [cfg80211]
[ 120.104876] [<c0016420>] (unwind_backtrace) from [<c0013d40>] (show_stack+0x20/0x24)
[ 120.104902] [<c0013d40>] (show_stack) from [<c0634c44>] (dump_stack+0x20/0x28)
[ 120.104925] [<c0634c44>] (dump_stack) from [<c0021ecc>] (__warn+0xe4/0x10c)
[ 120.104940] [<c0021ecc>] (__warn) from [<c0021fc0>] (warn_slowpath_null+0x30/0x38)
[ 120.105634] [<c0021fc0>] (warn_slowpath_null) from [<bf13d458>] (__cfg80211_disconnected+0x334/0x374 [cfg80211])
[ 120.106930] [<bf13d458>] (__cfg80211_disconnected [cfg80211]) from [<bf114b0c>] (cfg80211_process_wdev_events+0x160/0x1b4 [cfg80211])
[ 120.108355] [<bf114b0c>] (cfg80211_process_wdev_events [cfg80211]) from [<bf114b9c>] (cfg80211_process_rdev_events+0x3c/0x74 [cfg80211])
[ 120.109658] [<bf114b9c>] (cfg80211_process_rdev_events [cfg80211]) from [<bf10f218>] (cfg80211_event_work+0x24/0x2c [cfg80211])
[ 120.110298] [<bf10f218>] (cfg80211_event_work [cfg80211]) from [<c0039364>] (process_one_work+0x11c/0x398)
[ 120.110321] [<c0039364>] (process_one_work) from [<c003961c>] (worker_thread+0x3c/0x544)
[ 120.110346] [<c003961c>] (worker_thread) from [<c003f518>] (kthread+0x120/0x15c)
[ 120.110371] [<c003f518>] (kthread) from [<c000fe2c>] (ret_from_fork+0x14/0x28)
[ 120.110379] ---[ end trace e2dd472f47e28fa3 ]---
---
So I tried reloading the kernel module, this is at the moment the only way that works.

[epoch1970]

Ouch, that's a crash, not good at all.
If you suddenly remove the USB adapter you'd get this kind of crash, same if the adapter doesn't get enough power from the PSU.
If this happens during normal operation, perhaps the cause is in the adapter driver?

Reloading the module might be a workaround, but I wouldn't rely too much on that.