#!/bin/sh

# Script to get and/or check the Ethernet speed. Useful to be run by cron.
# Copyright (C) 2013-2020 Vincent Lefevre <vincent@vinc17.net>
#
# It needs the "ethtool" and "ip" utilities.
#
# Use the -q option to avoid the error message when no UP Ethernet devices
# are found and messages for devices with no Ethernet cable. Useful if the
# machine is not always connected by Ethernet, to avoid spurious messages.
#
# You can provide an optional argument, such as 1000Mb/s (expected speed).
# If the speed has this value, nothing will be output. This is useful to
# check by cron that the Ethernet speed hasn't been reduced (e.g. because
# of dust or a bad cable).
#
# All UP Ethernet devices (whose name matching the regexp in the code below)
# are checked.
#
# Note: Monitoring tools can do a better job, noticing changes immediately.
# But this utility is simpler to use and may still be useful. It should
# also be less sensitive to temporary issues.
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 3
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, see http://www.gnu.org/licenses/
# or write to the Free Software Foundation, Inc., 51 Franklin St,
# Fifth Floor, Boston, MA 02110-1301, USA.

unset quiet
if [ "x$1" = "x-q" ]; then
  quiet=1
  shift
fi

if [ $# -gt 1 ]; then
  echo "Usage: $0 [ -q ] [ <expected_speed> ]" >&2
  exit 1
fi

# Get the Ethernet devices that are up.
# Historical names start with "eth".
# New systemd/udev-based names start with "en":
#   https://www.freedesktop.org/software/systemd/man/systemd.net-naming-scheme.html
devices=$(ip link | \
          sed -n 's/.* \(\(en\|eth\)[-0-9a-z]*\):.*[,<]UP[,>].*/\1/p')

if [ -z "$devices" ]; then
  [ -z "$quiet" ] || exit 0
  echo "$0: can't find an Ethernet device" >&2
  exit 2
fi

et()
{
  # In not run as root, let's hide the ethtool spurious warnings
  # by redirecting stderr to /dev/null; but this will also hide
  # any error message (the user would then run ethtool manually).
  if [ "$(id -u)" -eq 0 ]; then
    ethtool $1
  else
    ethtool $1 2> /dev/null
  fi
}

for dev in $devices
do
  speed=$(et $dev | sed -n 's/^[[:space:]]*Speed:[[:space:]]*//p
                            s/^[[:space:]]*Link detected: no/NOLINK/p')
  case $speed in
    *NOLINK*)
      # This happens when the machine boots without an Ethernet cable and
      # netplug is used, because its probe rule sets all the eth* devices
      # up by default (see netplugd(8) man page). This can also happen on
      # machines with multiple Ethernet interfaces, but where one of them
      # is not used (I'm wondering why such an interface is up, though).
      [ -n "$quiet" ] || echo "$0: no link on $dev" ;;
    *)
      if [ -z "$speed" ]; then
        echo "$0: can't get $dev speed"
      elif [ "x$speed" != "x$1" ]; then
        echo "$0: $dev speed is $speed"
      fi ;;
  esac
done

# Exit with no errors (any output will be shown by cron).
exit 0

# $Id: check-eth-speed 127096 2020-04-29 15:06:28Z vinc17/zira $