stamina

#!/bin/sh
#
# A script which provides a point to point connection to
# a USB modem(ex: /dev/ttyUSB*, ...). its dependencies are:
#   usb_modeswitch, ModemManager, NetworkManager, systemd
#
#          From: https://codeberg.org@tcheukueppo/ktoolbox.git
#          Author: Kueppo Tcheukam

if test "$(uname)" != Linux ; then
  printf '%s: ERROR: this is a linux script\n' "$0" >&2
  exit 1
fi

if test "$(id -u)" -ne 0 ; then
  printf '%s: ERROR: root permission needed\n' "$0" >&2
  exit 1
fi

usage() {
cat<<EOF >&2
Usage: stamina [OPTIONS]... APN
establishes a connection to a usb modem, modems
of the type /dev/ttyUSB*, /dev/ttyS*, etc. stamina
takes as mandatory argument which is the APN.
APN depends on your service provider.
  -k, --kill  delete the network manager connection
              called "stamina" which was created
              when the usb modem was first plug-in.
EOF
}

check() {
   local cmd=''

   # to switch to from a storage device to a modem
   # send bulk message to the device with usb_modeswitch
   printf 'warn: mode switch the usb device(usb_modeswitch)\n'
   printf 'checking dependencies ...'
   for cmd in systemd usb_modeswitch ModemManger NetworkManager ; do
      command -v "$cmd" >/dev/null || {
         printf "\n%s: ERROR: \`%s' not found\n" "$0" "$cmd"
         exit 1
      }
   done
   printf 'ok'
}

servck() {
   local service=

   for service in ModemManger NetworkManager ; do
      printf 'starting "%s" service ...' $service
      systemctl start ModemManager >/dev/null 2>&1 && printf 'ok\n' || { printf 'failed\n'; exit 1; }
   done
}

pppcon() {
   local pport='' timeout=0

   printf 'listening to usb modems ...\n'
   while test "$(mmcli -L)" = "No modems were found"; do
      test $timeout = 8 && break
      sleep 4
      timeout=$(($timeout + 1))
   done
   test $timeout -lt 8 && printf ok || { printf failed; return 1; }
   # get modem index
   index="$(mmcli -L | cut -d/ -f6 | cut -d ' ' -f1)"
   if ! printf '%d\n' "$index" | grep -q '[0-9]\{1,\}' ; then
      printf '%s: ERROR: could not get modem index\n' "$0" >&2
      exit 1
   fi
   # create a persistent connection with networkmanager
   if nmcli connection show 2>/dev/null | grep -q '^Stamina ' ; then
      wmsg() {
         printf 'warning: this script should be run once, it creates\n'
         printf 'a persistent connection to a usb modem by creating\n'
         printf 'an active connection with NetworkManager so run\n'
         printf '`stamina -k` do delete the NetworkManager active\n'
         printf 'connection.\n'
      }
      wmsg >&2
      nmcli radio wwan on
      exit 1
   fi

   pport="$(mmcli -m $index | fgrep 'primary port' | cut -d: -f2)"
   pport=${pport## }
   if test -c "/dev/$pport" ; then
      nmcli radio wwan on
      nmcli connection add type gsm ifname "$pport" con-name "Stamina" apn "$1"
      test $? -eq 0 && printf 'usb modem connection succeeded\n'
   fi
}

kilcon() {
   local gguid
   if ! nmcli connection show | grep -q '^Stamina ' ; then
      printf '%s: ERROR: no connection found\n' "$0" >&2
      return 1
   fi
   printf 'attempting to delete the connection ...'
   gguid=$(nmcli connection show | grep '^Stamina ' | sed -n 's/^[^ ]\+ \+\([^ ]\+\).\+/\1/p')
   nmcli connection delete "$gguid"  && printf ok || printf failed
   return 0
}

stamina() {
   case $# in
      0) usage >&2 ;;
      1)
       case $1 in
          -k|--kill) kilcon ;;
          -h|--help) usage ;;
          *) check >&2 || exit 1
             printf 'connecting to a usb modem with apn "%s"\n' "$1"
             servck || return 1
             pppcon "$1" || return 1 ;;
       esac ;;
      *) printf 'invalid number of arguments\n' >&2 ;;
   esac
   return 0
}

stamina "$@"