#!/bin/sh
# Filename: set-permanent-dns-resolvers.sh
# Location: /etc/ansible/files
# Author: bgstack15@gmail.com
# Startdate: 2018-07-27 08:28:24
# Title: Set permanent Dns Resolvers
# Purpose: To provide a single command that inserts dns resolver information into the permanent network config
# Package: former-gists
# History: 
#    2018-08-03 improve -d1 info about resolv.conf 
# Usage: 
#    ./set-permanent-dns-resolvers.sh 1.2.3.4 5.6.7.8 -r --iface
# Reference: ftemplate.sh 2018-06-21m; framework.sh 2017-11-11m
# Improve:
fiversion="2018-06-21m"
SPDR_version="2018-08-03a"

usage() {
   ${PAGER:-/usr/bin/less -F} >&2 <<ENDUSAGE
usage: set-permanent-dns-resolvers.sh [-duV] [--ifile <ifile>] [-i eth0] [-c conffile] [<1.2.3.4> [<1.2.3.5> ...]]
Set the dns resolvers in both the interface file and resolv.conf.
version ${SPDR_version}
 -d debug   Show debugging info, including parsed variables.
 -u usage   Show this usage block.
 -V version Show script version number.
 -c conf    Read in this config file.
 -i interface  Use this interface.
 --iface    sets SPDR_DO_I
 --noiface  unsets SPDR_DO_I
 -s silent  sets SPDR_SILENT=1
 --nosilent sets SPDR_SILENT=0
 --ifile <file>   sets SPDR_IFILE
 --rfile <file>   sets SPDR_RFILE
 -r resolv  sets SPDR_DO_R
 --nor      unsets SPDR_DO_R
Return values:
 0 Normal
 1 Help or version info displayed
 2 Count or type of flaglessvals is incorrect
 3 Incorrect OS type
 4 Unable to find dependency
 5 Not run as root or sudo
 6 Invalid interface definition
 7 Invalid resolv.conf file
Environment variables:
SPDR_DNS1   What resolvers to use.
SPDR_DNS2   If one of these is set to "gone" the script will remove that value from the file.
SPDR_DNS3
SPDR_DO_I    If truthy, update SPDR_IFILE. Default is 1.
SPDR_DO_R    If truthy, update SPDR_RFILE. Default is 1.
SPDR_INTERFACE    The ethernet card to configure. If undefined, it will find the first ethernet card with a "DNS1" definition. If that fails, it will select the first ethernet card.
SPDR_IFILE   Exact interface file to manipulate. Default is blank, and it will be derived by the SPDR_INTERFACE value.
SPDR_RFILE   resolv.conf file. Default is /etc/resolv.conf
SPDR_SILENT  If truthy, suppress "changed" notification
Debug levels:
 1 changes being made
 2 checks being performed
 3 finding the interface to use
ENDUSAGE
}

# DEFINE FUNCTIONS
find_valid_interface() {
   # call: find_valid_interface
   # output: interface name on stdout.
   debuglev 9 && ferror "find_valid_interface $@"

   local output=""

   # Find first ethernet card with a DNS1 definition.
   output="$( grep -lE '^\s*DNS1\s*=' /etc/sysconfig/network-scripts/ifcfg* 2>/dev/null | sort | grep -vE '^(lo|loopback)$' | head -n1 )"
   if test -n "${output}" ;
   then
      echo "${output}"
   else
       # If that fails, select the first ethernet card found.
       output="$( find /etc/sysconfig/network-scripts/ifcfg* 2>/dev/null | sort | grep -vE -e '-(lo|loopback)$' )"
       if test -n "${output}" ;
       then
          echo "${output}" ;
       else
          # no DNS1 definitions and no ethernet card found. Fail out.
          ferror "${scriptfile}: 6. No valid interface definition found! Please check /etc/sysconfig/network-scripts. Aborted."
          exit 6
       fi
   fi
   debuglev 1 && ferror "Using interface $( basename "${output}" | sed -r -e 's/ifcfg-//;' )"
}

apply_interface() {
   # call: apply_interface "DNS1" "${SPDR_DNS1}" "${SPDR_IFILE}"
   # performs action and does not directly care about output
   debuglev 9 && ferror "apply_interface $@"

   local dnsnum="${1}"
   local dnsr="${2}"
   local ifile="${3}"
   local dnscurrent=""

   # if defined
   if test -n "${dnsr}" ;
   then
      if echo "${dnsr}" | grep -qE -e "gone|absent|empty" ;
      then
         # remove line if it exists
         if grep -qE -e "^\s*${dnsnum}\s*=" "${ifile}" ;
         then
            # remove line
            debuglev 1 && ferror "remove ${ifile} ${dnsnum}"
            sed -i -r -n -e "/^\s*${dnsnum}\s*=/! p" "${ifile}"
            mark_changed
         else
            # no change needed
            debuglev 2 && ferror "unchanged ${ifile} ${dnsnum} undefined"
         fi
      else
         # set value because it is defined
         if grep -qE -e "^\s*${dnsnum}\s*=" "${ifile}" ;
         then
            # see if the dnscurrent
            dnscurrent="$( grep -E "${dnsnum}=" "${ifile}" | awk -F'=' '{print $2}' )"
            if ! test "${dnscurrent}" = "${dnsr}" ;
            then
               # replace it
               debuglev 1 && ferror "change ${ifile} ${dnsnum} from ${dnscurrent} to ${dnsr}"
               sed -i -r -e "s/(^\s*${dnsnum}\s*=).*/\1${dnsr}/;" "${ifile}"
               mark_changed
            else
               debuglev 2 && ferror "unchanged ${ifile} ${dnsnum}=${dnsr}"
            fi
         else
            # add it
            debuglev 1 && ferror "add ${ifile} ${dnsnum}=${dnsr}"
            echo "${dnsnum}=${dnsr}" >> "${ifile}"
            mark_changed
            
         fi
      fi
   fi
}

mark_changed() {
   echo "1" > "${tmpfile1}"
}

apply_resolv_conf() {
   # call: apply_resolv_conf "1.2.3.4" "${DNS2}" "${DNS3}" "${SPDR_RFILE}"
   # performs action and does not really care about output
   debuglev 9 && ferror "apply_resolv_conf $@"

   local dns1="${1}"
   local dns2="${2}"
   local dns3="${3}"
   local rfile="${4}"

   # populate dns variables from file for comparison
   local rfile_contents="$( cat "${rfile}" 2>/dev/null )"
   local rfile_dns1="$( echo "${rfile_contents}" | sed -n '/nameserver/p' | awk -v "num=1" 'NR==num{print $2;}' )"
   local rfile_dns2="$( echo "${rfile_contents}" | sed -n '/nameserver/p' | awk -v "num=2" 'NR==num{print $2;}' )"
   local rfile_dns3="$( echo "${rfile_contents}" | sed -n '/nameserver/p' | awk -v "num=3" 'NR==num{print $2;}' )"

   # compare and update each one if needed
   x=0
   SPDR_rfile_done=0
   while test "${SPDR_rfile_done}" = 0 ;
   do
      x=$(( x + 1 ))
      eval this_dns_goal="\${SPDR_DNS${x}}"
      eval this_dns_already="\${rfile_dns${x}}"

      # if defined
      if test -n "${this_dns_goal}" ;
      then
         # if requested to be absent, then please remove it
         if echo "${this_dns_goal}" | grep -qE -e "gone|absent|empty" ;
         then
            # remove line if it exists
            awk -v "dnsgone=${x}" 'BEGIN{a=0} /nameserver/{a=a+1; if(a==dnsgone)next;} {print;}' "${rfile}" > "${tmpfile2}"
            replace_file_if_modified "${rfile}" "${tmpfile2}" && { debuglev 1 && ferror "remove nameserver ${x} of ${this_dns_already}" ; } || { debuglev 2 && ferror "unchanged nameserver ${x} empty" ; }
         elif test "${this_dns_goal}" != "${this_dns_already}" ;
         then

            # not the same so please update
            awk -v "dnsnum=${x}" -v "goal=${this_dns_goal}" 'BEGIN{a=0} /nameserver/{a=a+1;if (a==dnsnum)$2=goal;} {print;}' "${rfile}" > "${tmpfile2}"
            replace_file_if_modified "${rfile}" "${tmpfile2}" && debuglev 1 && ferror "change nameserver ${x} from ${this_dns_already} to ${this_dns_goal}"
            # if it needs to add the above logic did not cover it, so check and add it here
            if ! grep -qE "nameserver\\s+${this_dns_goal}" "${rfile}" ;
            then
               # it is not present so please add it
               debuglev 1 && ferror "add ${rfile} nameserver ${x} ${this_dns_goal}"
               echo "nameserver ${this_dns_goal}" >> "${rfile}"
            fi
            mark_changed
         else
            # no change needed
            debuglev 2 && ferror "unchanged ${rfile} nameserver ${x}: ${this_dns_already}"
         fi
      fi
      test ${x} -ge 3 && SPDR_rfile_done=1
   done

}

replace_file_if_modified() {
   # call: replace_file_if_modified "/etc/resolv.conf" "${tmpfile2}"
   # output: performs action and does not care about output
   # returns: 0 if a change occurred
   # goal is to replace first file if the second file is different than it
   debuglev 9 && ferror "replace_file_if_modified $@"

   local origfile="${1}"
   local tmpfile="${2}"
   if ! diff -q "${origfile}" "${tmpfile}" 1>/dev/null 2>&1 ;
   then
      cat "${tmpfile}" > "${origfile}"
      mark_changed ; # since we are just doing a simple boolean check at the end it is fine to spam this file
      return 0
   fi
   return 1
}

react_changed() {
   # call: react_changed
   # output: "changed" to stdout if there was any changes according to the tmpfile.
   # usage: in the trap before exiting this script

   # react to changed
   test -n "$( cat "${tmpfile1}" 2>/dev/null )" && ! fistruthy "${SPDR_SILENT}" && echo "changed"

}

# DEFINE TRAPS

clean_SPDR() {
   # use at end of entire script if you need to clean up tmpfiles
   # rm -f "${tmpfile1}" "${tmpfile2}" 2>/dev/null

   # Delayed cleanup
   if test -z "${FETCH_NO_CLEAN}" ;
   then
      nohup /bin/bash <<EOF 1>/dev/null 2>&1 &
sleep "${SPDR_CLEANUP_SEC:-300}" ; /bin/rm -r "${SPDR_TMPDIR:-NOTHINGTODELETE}" 1>/dev/null 2>&1 ;
EOF
   fi
}

CTRLC() {
   # use with: trap "CTRLC" 2
   # useful for controlling the ctrl+c keystroke
   :
}

CTRLZ() {
   # use with: trap "CTRLZ" 18
   # useful for controlling the ctrl+z keystroke
   :
}

parseFlag() {
   flag="$1"
   hasval=0
   case ${flag} in
      # INSERT FLAGS HERE
      "d" | "debug" | "DEBUG" | "dd" ) setdebug; ferror "debug level ${debug}" __debug_set_by_param=1;;
      "u" | "usage" | "help" | "h" ) usage; exit 1;;
      "V" | "fcheck" | "version" ) ferror "${scriptfile} version ${SPDR_version}"; exit 1;;
      #"i" | "infile" | "inputfile" ) getval; infile1=${tempval};;
      "c" | "conf" | "conffile" | "config" ) getval; conffile="${tempval}";;
      "i" | "interface" ) getval; SPDR_INTERFACE="${tempval}";;
      "iface" ) SPDR_DO_I=1;;
      "noiface" | "no-iface" | "noi" | "ni" ) SPDR_DO_I=0;;
      "s" | "silent" | "q" | "quiet" ) SPDR_SILENT=1;;
      "nosilent" | "no-silent" | "verbose" | "v" ) SPDR_SILENT=0;;
      "ifile" ) getval; SPDR_IFILE="${tempval}";;
      "rfile" ) getval; SPDR_RFILE="${tempval}";;
      "resolv" | "resolve" ) SPDR_DO_R=1;;
      "noresolv" | "noresolve" | "no-resolv" | "no-resolve" | "nr" | "nor" ) SPDR_DO_R=0;;
   esac
   
   debuglev 10 && { test ${hasval} -eq 1 && ferror "flag: ${flag} = ${tempval}" || ferror "flag: ${flag}"; }
}

# DETERMINE LOCATION OF FRAMEWORK
f_needed=20171111
while read flocation ; do if test -e ${flocation} ; then __thisfver="$( sh ${flocation} --fcheck 2>/dev/null )" ; if test ${__thisfver} -ge ${f_needed} ; then frameworkscript="${flocation}" ; break; else printf "Obsolete: %s %s\n" "${flocation}" "${__this_fver}" 1>&2 ; fi ; fi ; done <<EOFLOCATIONS
./framework.sh
${scriptdir}/framework.sh
$HOME/bin/bgscripts/framework.sh
$HOME/bin/framework.sh
$HOME/bgscripts/framework.sh
$HOME/framework.sh
/usr/local/bin/bgscripts/framework.sh
/usr/local/bin/framework.sh
/usr/bin/bgscripts/framework.sh
/usr/bin/framework.sh
/bin/bgscripts/framework.sh
/usr/local/share/bgscripts/framework.sh
/usr/share/bgscripts/framework.sh
EOFLOCATIONS
test -z "${frameworkscript}" && echo "$0: framework not found. Aborted." 1>&2 && exit 4

# INITIALIZE VARIABLES
# variables set in framework:
# today server thistty scriptdir scriptfile scripttrim
# is_cronjob stdin_piped stdout_piped stderr_piped sendsh sendopts
. ${frameworkscript} || echo "$0: framework did not run properly. Continuing..." 1>&2
infile1=
outfile1=
logfile=${scriptdir}/${scripttrim}.${today}.out
define_if_new interestedparties "bgstack15@gmail.com"
# SIMPLECONF
define_if_new default_conffile "/etc/default/set-permanent-dns-resolvers"
#define_if_new defuser_conffile ~/.spdrrc # no need for a default user conf file
test -z "${SPDR_TMPDIR}" && SPDR_TMPDIR="$( mktemp -d )"
define_if_new SPDR_DO_I 1
define_if_new SPDR_DO_R 1
define_if_new SPDR_RFILE "/etc/resolv.conf"
tmpfile1="$( TMPDIR="${SPDR_TMPDIR}" mktemp )"  # if contents exist, then something changed
tmpfile2="$( TMPDIR="${SPDR_TMPDIR}" mktemp )"  # contents for temporary rfile

# REACT TO OPERATING SYSTEM TYPE
case $( uname -s ) in
   Linux) : ;;
   FreeBSD) : ;;
   *) echo "${scriptfile}: 3. Indeterminate OS: $( uname -s )" 1>&2 && exit 3;;
esac

# SET CUSTOM SCRIPT AND VALUES
#setval 1 sendsh sendopts<<EOFSENDSH     # if $1="1" then setvalout="critical-fail" on failure
#/usr/local/share/bgscripts/send.sh -hs  # setvalout maybe be "fail" otherwise
#/usr/share/bgscripts/send.sh -hs        # on success, setvalout="valid-sendsh"
#/usr/local/bin/send.sh -hs
#/usr/bin/mail -s
#EOFSENDSH
#test "${setvalout}" = "critical-fail" && ferror "${scriptfile}: 4. mailer not found. Aborted." && exit 4

# VALIDATE PARAMETERS
# objects before the dash are options, which get filled with the optvals
# to debug flags, use option DEBUG. Variables set in framework: fallopts
validateparams - "$@"

# LEARN EX_DEBUG
test -z "${__debug_set_by_param}" && fisnum "${SPDR_DEBUG}" && debug="${SPDR_DEBUG}"

# CONFIRM TOTAL NUMBER OF FLAGLESSVALS IS CORRECT
#if test ${thiscount} -lt 2;
#then
#   ferror "${scriptfile}: 2. Fewer than 2 flaglessvals. Aborted."
#   exit 2
#fi

# LOAD CONFIG FROM SIMPLECONF
# This section follows a simple hierarchy of precedence, with first being used:
#    1. parameters and flags
#    2. environment
#    3. config file
#    4. default user config: ~/.config/script/script.conf
#    5. default config: /etc/script/script.conf
if test -f "${conffile}";
then
   get_conf "${conffile}"
else
   if test "${conffile}" = "${default_conffile}" || test "${conffile}" = "${defuser_conffile}"; then :; else test -n "${conffile}" && ferror "${scriptfile}: Ignoring conf file which is not found: ${conffile}."; fi
fi
test -f "${defuser_conffile}" && get_conf "${defuser_conffile}"
test -f "${default_conffile}" && get_conf "${default_conffile}"

# CONFIGURE VARIABLES AFTER PARAMETERS
# yes, command line parameters should clobber environment variables
test -n "${opt1}" && SPDR_DNS1="${opt1}"
test -n "${opt2}" && SPDR_DNS2="${opt2}"
test -n "${opt3}" && SPDR_DNS3="${opt3}"

## REACT TO BEING A CRONJOB
#if test ${is_cronjob} -eq 1;
#then
#   :
#else
#   :
#fi

# SET TRAPS
#trap "CTRLC" 2
#trap "CTRLZ" 18
trap "__ec=$? ; react_changed ; clean_SPDR ; trap '' 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 ; exit ${__ec} ;" 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

# DEBUG SIMPLECONF
debuglev 5 && {
   ferror "Using values"
   # used values: EX_(OPT1|OPT2|VERBOSE)
   set | grep -iE "^SPDR_" 1>&2
}

# REACT TO ROOT STATUS
case ${is_root} in
   1) # proper root
      : ;;
   sudo) # sudo to root
      : ;;
   "") # not root at all
      ferror "${scriptfile}: 5. Please run as root or sudo. Aborted."
      exit 5
      ;;
esac

# MAIN LOOP
#{

   # Should we do the interface configuration?
   if fistruthy "${SPDR_DO_I}" ;
   then

      # skip the check if SPDR_IFILE is defined already.
      if test -z "${SPDR_IFILE}" ;
      then

         # Get a valid interface
         if test -z "${SPDR_INTERFACE}" ;
         then
            debuglev 3 && ferror "Will scan for valid interface."
            SPDR_INTERFACE="$( find_valid_interface )"
         elif test ! -e "/etc/sysconfig/network-scripts/ifcfg-${SPDR_INTERFACE}" ;
         then
            # no requested interface, or the requested one is not valid
            debuglev 3 && ferror "${scriptfile}: invalid interface \"${SPDR_INTERFACE}\", so will scan for valid one."
            SPDR_INTERFACE="$( find_valid_interface )"
         fi

         # Trim interface name down to just "eth0"
         echo "${SPDR_INTERFACE}" | grep -qE -e 'ifcfg' && SPDR_INTERFACE="$( basename "${SPDR_INTERFACE}" 2>/dev/null | sed -r -e 's/ifcfg-//;' )"
         # Confirm interface is valid
         if test ! -e "/etc/sysconfig/network-scripts/ifcfg-${SPDR_INTERFACE}" ;
         then
            ferror "${scriptfile}: 6. Cannot find interface ${SPDR_INTERFACE}. Aborted."
            exit 6
         fi
         SPDR_IFILE="/etc/sysconfig/network-scripts/ifcfg-${SPDR_INTERFACE}"

      fi

      # Now with the valid interface file at SPDR_IFILE, please update the DNS1 and DNS2 and DNS3 settings.
      x=0
      SPDR_done=0
      cat /dev/null > "${tmpfile1}" # set changed value to 0
      while test "${SPDR_done}" = 0 ;
      do
         x=$(( x + 1 ))
         eval this_dnsr="\${SPDR_DNS${x}}"
         apply_interface "DNS${x}" "${this_dnsr}" "${SPDR_IFILE}"
         test $x -ge 3 && SPDR_done=1
      done

   fi

   # Should we do the resolv.conf configuration?
   if fistruthy "${SPDR_DO_R}" ;
   then

      # confirm file exists
      # create it if it does not.
      if test ! -e "${SPDR_RFILE}" ;
      then
         touch "${SPDR_RFILE}"
         mark_changed
      fi

      # confirm file is writable
      if test ! -w "${SPDR_RFILE}" ;
      then
         ferror "${scriptfile}: 7. Cannot modify resolv \"${SPDR_RFILE}\". Aborted."
         exit 7
      fi

      # peform changes
      apply_resolv_conf "${SPDR_DNS1}" "${SPDR_DNS2}" "${SPDR_DNS3}" "${SPDR_RFILE}"

   fi

#} | tee -a ${logfile}

# EMAIL LOGFILE
#${sendsh} ${sendopts} "${server} ${scriptfile} out" ${logfile} ${interestedparties}

# exit safely
exit 0