autohotspot

#!/bin/bash
# Based on autohotspot script version 0.95-41-N/HS-I from RaspberryConnect.com
# See full details at https://www.raspberryconnect.com/projects/65-raspberrypi-hotspot-accesspoints/157-raspberry-pi-auto-wifi-hotspot-switch-internet

wifidev="wlan0" # Wifi device name
ethdev="eth0" # Ethernet device to use with IP tables (IP forwarding for bridged-wifi-to-ethernet setup)

IFSdef=$IFS
cnt=0
# The next four lines capture the wifi networks the RPi is setup to use
wpassid=$(awk '/ssid="/{ print $0 }' /etc/wpa_supplicant/wpa_supplicant.conf | awk -F'ssid=' '{ print $2 }' ORS=',' | sed 's/\"/''/g' | sed 's/,$//')
wpassid=$(echo "${wpassid//[$'\r\n']}")
IFS=","
ssids=($wpassid)
IFS=$IFSdef # Reset back to defaults

mac=()

ssidsmac=("${ssids[@]}" "${mac[@]}") # Combines SSID and MAC for checking

createAdHocNetwork()
{
  echo "Creating local hotspot"
  ip link set dev "$wifidev" down
  ip a add 192.168.50.5/24 brd + dev "$wifidev"
  ip link set dev "$wifidev" up
  dhcpcd -k "$wifidev" >/dev/null 2>&1
  iptables -t nat -A POSTROUTING -o "$ethdev" -j MASQUERADE
  iptables -A FORWARD -i "$ethdev" -o "$wifidev" -m state --state RELATED,ESTABLISHED -j ACCEPT
  iptables -A FORWARD -i "$wifidev" -o "$ethdev" -j ACCEPT
  systemctl start dnsmasq
  systemctl start hostapd
  echo 1 > /proc/sys/net/ipv4/ip_forward
}

KillHotspot()
{
  echo "Shutting down local hotspot"
  ip link set dev "$wifidev" down
  systemctl stop hostapd
  systemctl stop dnsmasq
  iptables -D FORWARD -i "$ethdev" -o "$wifidev" -m state --state RELATED,ESTABLISHED -j ACCEPT
  iptables -D FORWARD -i "$wifidev" -o "$ethdev" -j ACCEPT
  echo 0 > /proc/sys/net/ipv4/ip_forward
  ip addr flush dev "$wifidev"
  ip link set dev "$wifidev" up
  dhcpcd -n "$wifidev" >/dev/null 2>&1
}

ChkWifiUp()
{
  echo "Checking wifi connection"
  sleep 20 # Give enough time for connection to be completed to router
  if ! wpa_cli -i "$wifidev" status | grep 'ip_address' >/dev/null 2>&1
    then # Failed to connect to a known wifi network (known wifi network not in range)
    echo 'Wifi failed to connect, falling back to local hotspot'
    wpa_cli terminate "$wifidev" >/dev/null 2>&1
    createAdHocNetwork
  fi
}

FindSSID()
{
  # Check to see what SSID's and MAC addresses are in range
  ssidChk=('NoSSid')
  i=0; j=0
  until [ $i -eq 1 ] # Wait for wifi if busy
  do
    ssidreply=$((iw dev "$wifidev" scan ap-force | egrep "^BSS|SSID:") 2>&1) >/dev/null 2>&1
    echo "SSid's in range: " $ssidreply
    echo "Device Available Check try " $j
    if (($j >= 10)); then #if busy 10 times goto hotspot
      echo "Device busy or unavailable 10 times, going to Hotspot"
      ssidreply=""
      i=1
    elif echo "$ssidreply" | grep "No such device (-19)" >/dev/null 2>&1; then
      echo "No Device Reported, try " $j
      NoDevice
    elif echo "$ssidreply" | grep "Network is down (-100)" >/dev/null 2>&1 ; then
      echo "Network Not available, trying again" $j
      j=$((j + 1))
      sleep 2
    elif echo "$ssidreply" | grep "Read-only file system (-30)" >/dev/null 2>&1 ; then
      echo "Temporary Read only file system, trying again"
      j=$((j + 1))
      sleep 2
    elif echo "$ssidreply" | grep "Invalid exchange (-52)" >/dev/null 2>&1 ; then
      echo "Temporary unavailable, trying again"
      j=$((j + 1))
      sleep 2
    elif ! echo "$ssidreply" | grep "resource busy (-16)"  >/dev/null 2>&1 ; then
      echo "Device Available, checking SSid Results"
      i=1
    else #see if device not busy in 2 seconds
      echo "Device unavailable checking again, try " $j
      j=$((j + 1))
      sleep 2
    fi
done

for ssid in "${ssidsmac[@]}"
do
  if (echo "$ssidreply" | grep "$ssid") >/dev/null 2>&1
  then
    # Valid SSID found, passing to script
    echo "Valid SSID detected, assesing wifi status"
    ssidChk=$ssid
    return 0
  else
    # No valid SSID found
    echo "No SSID found, assessing wifi status"
    ssidChk='NoSSid'
  fi
done
}

NoDevice()
{
  # If no wifi device, activate wifi so it will be available when it is reconnected
  echo "No wifi device connected"
  wpa_supplicant -B -i "$wifidev" -c /etc/wpa_supplicant/wpa_supplicant.conf >/dev/null 2>&1
  exit 1
}

FindSSID

# Create local hotspot or connect to valid wifi network
if [ "$ssidChk" != "NoSSid" ]
then
  echo 0 > /proc/sys/net/ipv4/ip_forward # Deactivate IP forwarding
  if systemctl status hostapd | grep "(running)" >/dev/null 2>&1
  then # Hotspot running and SSID in range
    KillHotspot
    echo "Hotspot deactivated, bringing wifi up"
    wpa_supplicant -B -i "$wifidev" -c /etc/wpa_supplicant/wpa_supplicant.conf >/dev/null 2>&1
    ChkWifiUp
  elif { wpa_cli -i "$wifidev" status | grep 'ip_address'; } >/dev/null 2>&1
    then # Already connected
    echo "Already connected to an existing network"
  else # SSID exists and no hotspot running --> connect to wifi network
    echo "Connecting to the wifi network"
    wpa_supplicant -B -i "$wifidev" -c /etc/wpa_supplicant/wpa_supplicant.conf >/dev/null 2>&1
    ChkWifiUp
  fi
else # SSID or MAC address not in range
  if systemctl status hostapd | grep "(running)" >/dev/null 2>&1
  then
    echo "Hostspot already active"
  elif { wpa_cli status | grep "$wifidev"; } >/dev/null 2>&1
  then
    echo "Cleaning wifi files and activating local hotspot"
    wpa_cli terminate >/dev/null 2>&1
    ip addr flush "$wifidev"
    ip link set dev "$wifidev" down
    rm -r /var/run/wpa_supplicant >/dev/null 2>&1
    createAdHocNetwork
  else
    echo "No valid SSID found, activating local hotspot"
    createAdHocNetwork
  fi
fi