I have a Samsung laptop, with Ubuntu 15.04 installed, upgraded all the way down from 13.10 but that's not the problem.
I have connected to countless wifi networks over time without trouble... That is, until a few days ago. I am temporarily working at a client's place and wasn't able to connect to any wifi networks at all. All networks were seen, I just couldn't establish a connection...
As no one else but me had trouble, I knew the problem was on my end.
My card is this:
02:00.0 Network controller: Intel Corporation Centrino Advanced-N 6235 (rev 24)
It uses the iwlwifi driver. And here is what
modinfo reports as options:
parm: swcrypto:using crypto in software (default 0 [hardware]) (int) parm: 11n_disable:disable 11n functionality, bitmap: 1: full, 2: disable agg TX, 4: disable agg RX, 8 enable agg TX (uint) parm: amsdu_size_8K:enable 8K amsdu size (default 0) (int) parm: fw_restart:restart firmware in case of error (default true) (bool) parm: antenna_coupling:specify antenna coupling in dB (default: 0 dB) (int) parm: wd_disable:Disable stuck queue watchdog timer 0=system default, 1=disable (default: 1) (int) parm: nvm_file:NVM file name (charp) parm: uapsd_disable:disable U-APSD functionality (default: Y) (bool) parm: bt_coex_active:enable wifi/bt co-exist (default: enable) (bool) parm: led_mode:0=system default, 1=On(RF On)/Off(RF Off), 2=blinking, 3=Off (default: 0) (int) parm: power_save:enable WiFi power management (default: disable) (bool) parm: power_level:default power save level (range from 1 - 5, default: 1) (int) parm: fw_monitor:firmware monitor - to debug FW (default: false - needs lots of memory) (bool)
By a pure hunch, I modified the appropriate modprobe.d file to add:
options iwlwifi bt_coex_active=0
and all of a sudden I had no problems connecting anymore...
Why does this work? What does this option do?