I use a laptop with Atheros wifi card with ath9k driver. I use hostapd to convert my laptop wifi into AP (Access point) so I can share network with my Nexus 7 and Kindle. This has been working fine for quite some time till my recent update.
After recent system update (I use Debian Sid), I couldn't for some reason convert my wifi into AP so my device can connect. I can't find anything in log nor in hostapd debug messages which is useful to trouble shoot the issue. Every time I start the laptop my wifi card will be blocked by RF-KILL and I have manually unblock (both hard and soft). The script which I use to convert my Wifi into AP is below
#Initial wifi interface configuration
ifconfig "$1" up 192.168.2.1 netmask 255.255.255.0
sleep 2
# start dhcp
sudo systemctl restart dnsmasq.service
iptables --flush
iptables --table nat --flush
iptables --delete-chain
iptables -t nat -A POSTROUTING -o "$2" -j MASQUERADE
iptables -A FORWARD -i "$1" -j ACCEPT
sysctl -w net.ipv4.ip_forward=1
#start hostapd
hostapd /etc/hostapd/hostapd.conf &> /dev/null &
I tried rebooting the laptop and for some time I managed to convert my wifi into AP, I noticed at same time that Network Manager is not started once laptop is booted, yeah this also started happening after recent upgrade which I guess is the black magic of systemd. After some time I noticed wifi has went down and now I can't bring it up because its blocked by RF-KILL. After checking the syslog I noticed following lines.
Jul 18 23:09:30 rudra kernel: [ 1754.891060] IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready Jul 18 23:09:30 rudra NetworkManager[5485]: <info> (mon.wlan0): using nl80211 for WiFi device control Jul 18 23:09:30 rudra NetworkManager[5485]: <info> (mon.wlan0): driver supports Access Point (AP) mode Jul 18 23:09:30 rudra NetworkManager[5485]: <info> (mon.wlan0): new 802.11 WiFi device (driver: 'ath9k' ifindex: 10) Jul 18 23:09:30 rudra NetworkManager[5485]: <info> (mon.wlan0): exported as /org/freedesktop/NetworkManager/Devices/8 Jul 18 23:09:30 rudra NetworkManager[5485]: <info> (mon.wlan0): device state change: unmanaged -> unavailable (reason 'managed') [10 20 2] Jul 18 23:09:30 rudra NetworkManager[5485]: <info> (mon.wlan0): preparing device Jul 18 23:09:30 rudra NetworkManager[5485]: <info> devices added (path: /sys/devices/pci0000:00/0000:00:1c.1/0000:04:00.0/net/mon.wlan0, iface: mon.wlan0) Jul 18 23:09:30 rudra NetworkManager[5485]: <info> device added (path: /sys/devices/pci0000:00/0000:00:1c.1/0000:04:00.0/net/mon.wlan0, iface: mon.wlan0): no ifupdown configuration found. Jul 18 23:09:33 rudra ModemManager[891]: <warn> Couldn't find support for device at '/sys/devices/pci0000:00/0000:00:1c.1/0000:04:00.0': not supported by any plugin
Well I couldn't figure out much but it looks like NetworkManager has come up and after seeing interface mon.wlan0, a monitoring interface created by hostapd to monitor the AP goes mad and tries to do something with it. I've no clue what it is doing and don't have enough patience to debug that. Probably some expert can give me hints on this.
So as a last resort I purged the NetworkManager completely from the system and settled back to good old wicd and rebooted the system. After reboot wifi card is happy and is not blocked by RF-KILL and now I can convert it AP and use it as long as I wish without any problems. Wicd is not a great tool but its good enough to get the job done and does only what is asked to it unlike the NetworkManager.
So in short
NetworkManager please stop f***ing with my settings and stop acting oversmart.