Create a script that connects to network and if it fails fallbacks to ad-hoc network

Question

I'd like to create a script that tries to connect me to the WiFi specified by my wpa_supplicant conf, and if it fails, create an ad-hoc network. But I'm struggling with it.

Here is what I have done so far:

#!/bin/bash

# create adhoc network function
createAdHocNetwork(){
    echo "Creating ad-hoc network"
    ifconfig wlan0 down
    iwconfig wlan0 mode ad-hoc
    iwconfig wlan0 essid AccessPoint
    ifconfig wlan0 11.0.0.1 netmask 255.255.255.0 up
    echo "Ad-hoc network created"
}

# connect to wifi function
connect(){
    echo "Trying to connect to configured wifi"
    ifdown wlan0
    wpa_supplicant -B -i wlan0 -c /home/pi/pics/wpa_supplicant.conf
    ifup wlan0
    echo "Wifi configured"
}

echo "================================="
echo "Wifi setup"
echo "================================="
connect
echo "Checking connectivity..."
sleep 5s
ping -c 5 -I wlan0 google.com > /dev/null 2>&1
PINGSTATUS=$?
echo "Status"
echo $PINGSTATUS
if [ $PINGSTATUS -eq 0 ];
    then
        echo "Connected to WiFi"
    else
        echo "Wifi not connected, fallback to ad-hoc"
        createAdHocNetwork
fi

exit 0

It seems it connects to the configured Wi=Fi, but not for the ad-hoc.

Here is my /etc/network/interfaces :

# start interfaces upon start of the system
auto lo wlan0

# register loopback interface
iface lo inet loopback

# use dhcp and allow interface to be started when kernel detects a hotplug event
allow-hotplug eth0
iface eth0 inet dhcp

# use manual ip configuration for wlan0 interface and allow hotplug as well
allow-hotplug wlan0
iface wlan0 inet dhcp

And my /etc/dhcp/dhcpd.conf:

ddns-update-style interim;
default-lease-time 600;
max-lease-time 7200;
authoritative;
log-facility local7;
subnet 11.0.0.0 netmask 255.255.255.0 {
  range 11.0.0.2 11.0.0.150;
}

I can see the ad-hoc network from another computer, but I cannot connect to it, any ideas?

Answer 1

It is an issue of your WiFi Dongle. If you are using Edimax 7811UN it will not work with Linux Kernels past 3.8+ versions for ad-hoc mode functions. This has been examined by me and this query will assure you of it.

I suggest to use Ralink Based RT5370 Chipset dongles. They work well with ad-hoc mode as I use Ad-hoc mode everyday with almost 10 RPis.