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Ping a port with hping3

# cf. http://trac.macports.org/wiki/InstallingMacPorts
/opt/local/bin/port info hping3
/usr/bin/sudo /opt/local/bin/port install hping3

hping3 --help


# Terminal window 1
alias sudo=/usr/bin/sudo
alias tcpdump=/usr/sbin/tcpdump
#sudo tcpdump -s0 -xX -i lo0 port 4678 and host localhost
sudo tcpdump -s0 -vvv -i lo0 port 4678 and host localhost


# Terminal window 2
alias sudo=/usr/bin/sudo
alias hping3=/opt/local/sbin/hping3
sudo hping3 -I lo0 -s 4678 -c 1 localhost -p 4678
sudo hping3 -S -I lo0 -d 995 -s 4678 -c 1 localhost -p 4678
sudo hping3 -SA -I lo0 -d 995 -w 200 -s 4678 -c 1 localhost -p 4678
sudo hping3 -SA -M 3000 -I lo0 -d 995 -w 65 -s 4678 -c 1 localhost -p 4678
sudo hping3 -DV -SA -I lo0 -s 4678 -a 192.168.1.100 -c 1 localhost -p 4678


#----------------------------------------


# some corresponding ipfw rules for testing purposes 
# (just place them at the beginning of your ipfw rule set)

# not me to me & me to not me
/sbin/ipfw -q add count log all from not me to me 4678 in
/sbin/ipfw -q add count log all from me to not me 4678 out

# any to me & me to any
/sbin/ipfw -q add count log all from any to me 4678 in
/sbin/ipfw -q add count log all from me to any 4678 out
    
# any to any
/sbin/ipfw -q add count log all from any to any 4678

Analyze internet traffic volume with dynamic ipfw rules

# cf. Example ipfw ruleset, http://codesnippets.joyent.com/posts/show/1267
# cf. also http://codesnippets.joyent.com/posts/show/1729

man ipfw 2>/dev/null | less -p "If the ruleset"
man ipfw 2>/dev/null | less -p "These dynamic rules"
man ipfw 2>/dev/null | less -p "All rules"

man ipfw 2>/dev/null | less -p "STATEFUL FIREWALL"     # press [n]
man ipfw 2>/dev/null | less -p "SYSCTL VARIABLES"
man ipfw 2>/dev/null | less -p "EXAMPLES"
man ipfw 2>/dev/null | less -p "DYNAMIC RULES"

/usr/bin/sudo /sbin/ipfw -d -e -t list
/usr/bin/sudo /sbin/ipfw -d -e -t list | /usr/bin/sed -E -n -e '1,/^## Dynamic rules/p'
/usr/bin/sudo /sbin/ipfw -d -e -t list | /usr/bin/sed -E -n -e '/^## Dynamic rules/,$p'
/usr/bin/sudo /sbin/ipfw -d -e -t list | /usr/bin/awk '/^## Dynamic rules/,/^$/ {print $0}'
/usr/bin/sudo /sbin/ipfw -d -e -t list | /usr/bin/awk '/<->/ {print $0}'
/usr/bin/sudo /sbin/ipfw -d -e -t list | /usr/bin/awk '{ if ( $0 ~ /<->/ ) {print $0}}'

/usr/bin/sudo /sbin/ipfw -d -e -t list | grep RULENUM
/usr/bin/sudo /sbin/ipfw -d -e -t list | grep IPADDR

/usr/sbin/sysctl -a | egrep 'tcp'
/usr/sbin/sysctl -a | egrep 'net.inet'
/usr/sbin/sysctl -a | egrep '\.fw'
/usr/sbin/sysctl -a | egrep 'ip.fw'
/usr/sbin/sysctl -a | egrep 'li[fv]e'
/usr/sbin/sysctl -a | egrep 'ip.fw.+life'

/usr/sbin/sysctl -n net.inet.tcp.always_keepalive
/usr/sbin/sysctl -n net.inet.ip.fw.dyn_keepalive
/usr/sbin/sysctl -n net.inet.ip.fw.dyn_buckets
/usr/sbin/sysctl -n net.inet.ip.fw.dyn_count
/usr/sbin/sysctl -n net.inet.ip.fw.dyn_max


# list all dynamic ipfw rules

function ipfwtraffic() {

   declare args argsregex bytes megabytes

   if [[ $# -eq 0 ]]; then

      /usr/bin/sudo /sbin/ipfw -d -e -t list | \
         /usr/bin/awk '/<->/ {printf "%-10s %-10s %-20s %-10s %-20s %-10s %-10s\n", $3, $6, $7, $8, $10, $11, $1}' | \
         /usr/bin/sort -bu | while IFS=" " read  bytes proto ipnum1 port1 ipnum2 port2 rulenum; do

      # byte
      #bytes=$(printf "%s\n" "${bytes}" | /usr/bin/awk '{ total = total + $1 } END { print total }')
      #printf "\e[1mbytes\e[m: %-17s %-10s %-40s \e[1mrule\e[m: %-15s \e[1mports\e[m: %-15s\n" \
           #"${bytes}" "${proto}" "${ipnum1}  ::  ${ipnum2}" "${rulenum}" "${port1}  ${port2}"

      # mega byte
      megabytes=$(printf "%s\n" "${bytes}" | /usr/bin/awk '{ total = (total + $1) / (1024*1024.0) } END { print total }')
      printf "\e[1mmbytes\e[m: %-20.6f %-10s %-40s \e[1mrule\e[m: %-15s \e[1mports\e[m: %-15s\n" \
           "${megabytes}" "${proto}" "${ipnum1}  ::  ${ipnum2}" "${rulenum}" "${port1}  ${port2}"

      done | /usr/bin/sort -rn -k 2,2

   else

      args="${@}"
      if [[ "${args}" != "${args//[^. [:digit:]]/}" ]]; then 
         printf "%s\n" 'Found at least one invalid rule number or IP address!'
         return 1
      fi

      if [[ "${args//[ [:digit:]]/}" == '' ]]; then 
         argsregex="^0*(${args// /|})"    #  ipfw rule numbers 
      else
         argsregex="(${args// /|})"    #  IP addresses
      fi
    
      #echo $argsregex

      /usr/bin/sudo /sbin/ipfw -d -e -t list | /usr/bin/egrep "${argsregex}" | \
         /usr/bin/awk '/<->/ {printf "%-10s %-10s %-20s %-10s %-20s %-10s %-10s\n", $3, $6, $7, $8, $10, $11, $1}' | \
         /usr/bin/sort -bu | while IFS=" " read  bytes proto ipnum1 port1 ipnum2 port2 rulenum; do

      # byte
      #bytes=$(printf "%s\n" "${bytes}" | /usr/bin/awk '{ total = total + $1 } END { print total }')
      #printf "\e[1mbytes\e[m: %-17s %-10s %-40s \e[1mrule\e[m: %-15s \e[1mports\e[m: %-15s\n" \
           #"${bytes}" "${proto}" "${ipnum1}  ::  ${ipnum2}" "${rulenum}" "${port1}  ${port2}"

      # mega byte
      megabytes=$(printf "%s\n" "${bytes}" | /usr/bin/awk '{ total = (total + $1) / (1024*1024.0) } END { print total }')
      printf "\e[1mmbytes\e[m: %-20.6f %-10s %-40s \e[1mrule\e[m: %-15s \e[1mports\e[m: %-15s\n" \
           "${megabytes}" "${proto}" "${ipnum1}  ::  ${ipnum2}" "${rulenum}" "${port1}  ${port2}"

      done | /usr/bin/sort -rn -k 2,2

   fi

   return 0
}



# usage:
# ipfwtraffic
# ipfwtraffic [rulenum1] [rulenum2] [rulenum3] ...
# ipfwtraffic [ipaddr1] [ipaddr2] [ipaddr3] ...


ipfwtraffic
ipfwtraffic  9600 10600 11000
ipfwtraffic xx.xxx.xx.xxx xx.xxx.xx.xx

ipfwtraffic | grep 'xx.xxx.xx.xx'



#------------------------------------------------------------------------------



# summarize pairs of IP addresses

function ipfwdynstats() {

   declare args argsregex dynrules ipaddr_pairs

   OIFS=${IFS}
   IFS=$'\n'

   if [[ $# -eq 0 ]]; then

      ipaddr_pairs=($(/usr/bin/sudo /sbin/ipfw -d -e -t list | /usr/bin/awk '/<->/ {print $7, $10}' | /usr/bin/sort -bu))

      dynrules=($(/usr/bin/sudo /sbin/ipfw -d -e -t list | /usr/bin/awk '/<->/ {print $7, $8, $10, $11, $6, $2, $3, $1}' | /usr/bin/sort -bu))

   else

      args="${@}"

      if [[ "${args}" != "${args//[^. [:digit:]]/}" ]]; then 
         printf "%s\n" 'Found at least one invalid rule number or IP address!'
         return 1
      fi

      if [[ "${args//[ [:digit:]]/}" == '' ]]; then 
         argsregex="^0*(${args// /|})"    #  ipfw rule numbers 
      else
         argsregex="(${args// /|})"    #  IP addresses
      fi
    

      ipaddr_pairs=($(/usr/bin/sudo /sbin/ipfw -d -e -t list | /usr/bin/egrep "${argsregex}" | \
           /usr/bin/awk '/<->/ {print $7, $10}' | /usr/bin/sort -bu))

      dynrules=($(/usr/bin/sudo /sbin/ipfw -d -e -t list | /usr/bin/egrep "${argsregex}" | \
           /usr/bin/awk '/<->/ {print $7, $8, $10, $11, $6, $2, $3, $1}' | /usr/bin/sort -bu))


   fi


for ((i=0; i < "${#ipaddr_pairs[@]}"; i++)); do 

   # byte
   #bytesum=$(printf "%s\n" "${dynrules[@]}" | \
        #/usr/bin/awk '$1 == "'"${ipaddr_pairs[${i}]% *}"'" && $3 == "'"${ipaddr_pairs[${i}]#* }"'" { print $7 }' | \
        #/usr/bin/awk '{ total = total + $1 } END { print total }')

   # mega byte
   bytesum=$(printf "%s\n" "${dynrules[@]}" | \
        /usr/bin/awk '$1 == "'"${ipaddr_pairs[${i}]% *}"'" && $3 == "'"${ipaddr_pairs[${i}]#* }"'" { print $7 }' | \
        /usr/bin/awk 'BEGIN { total=0 }; { total = (total + $1) / (1024*1024.0) } END { print total }')


   proto=$(printf "%s\n" "${dynrules[@]}" | \
        /usr/bin/awk '$1 == "'"${ipaddr_pairs[${i}]% *}"'" && $3 == "'"${ipaddr_pairs[${i}]#* }"'" { print $5 }' | \
        /usr/bin/sort -bu)


   rule=$(printf "%s\n" "${dynrules[@]}" | \
        /usr/bin/awk '$1 == "'"${ipaddr_pairs[${i}]% *}"'" && $3 == "'"${ipaddr_pairs[${i}]#* }"'" { print $NF }' | \
        /usr/bin/sort -bu)


   ports=$(printf "%s\n" "${dynrules[@]}" | \
        /usr/bin/awk '$1 == "'"${ipaddr_pairs[${i}]% *}"'" && $3 == "'"${ipaddr_pairs[${i}]#* }"'" { print $2,$4 }' | \
        /usr/bin/sort -bu)


   # byte
   #printf "\e[1mbytes\e[m: %-20s %-10s %-40s \e[1mrules\e[m: %-25s \e[1mports\e[m: %-30s\n" \
        #"${bytesum}" "${proto//[[:cntrl:]]/, }" "${ipaddr_pairs[${i}]% *}  ::  ${ipaddr_pairs[${i}]#* }" \
        #"${rule//[[:cntrl:]]/, }" "${ports//[[:cntrl:]]/, }"


   # mega byte
   printf "\e[1mmbytes\e[m: %-20.6f %-10s %-40s \e[1mrules\e[m: %-25s \e[1mports\e[m: %-30s\n" \
        "${bytesum}" "${proto//[[:cntrl:]]/, }" "${ipaddr_pairs[${i}]% *}  ::  ${ipaddr_pairs[${i}]#* }" \
        "${rule//[[:cntrl:]]/, }" "${ports//[[:cntrl:]]/, }"

done | /usr/bin/sort -rn -k 2,2

   export IFS=${OIFS}
   return 0

}


# usage:
# ipfwdynstats
# ipfwdynstats [rulenum1] [rulenum2] [rulenum3] ...
# ipfwdynstats [ipaddr1] [ipaddr2] [ipaddr3] ...


ipfwdynstats
ipfwdynstats  5200 12700
ipfwdynstats xx.xxx.xx.xxx xxx.xxx.xx.xxx



#------------------------------------------------------------------------------



# list port-specific internet traffic

function porttraffic() {

   declare args argsregex dynrules ipaddr_pairs

   OIFS=${IFS}
   IFS=$'\n'

   if [[ $# -eq 0 ]]; then
   
      printf "%s\n" 'No port number given!'
      return 1
   
   elif [[ $# -eq 1 ]]; then

      if [[ "${1//[[:digit:]]/}" != '' ]]; then 
         printf "%s\n" 'Invalid port number!'
         return 1
      fi

      ipaddr_pairs=($(/usr/bin/sudo /sbin/ipfw -d -e -t list | \
         /usr/bin/awk '/<->/ && ( $8 == "'"${1}"'" || $11 == "'"${1}"'" ) {print $7, $10 }' | /usr/bin/sort -bu))

      dynrules=($(/usr/bin/sudo /sbin/ipfw -d -e -t list | \
         /usr/bin/awk '/<->/ && ( $8 == "'"${1}"'" || $11 == "'"${1}"'" ) {print $7, $8, $10, $11, $6, $2, $3, $1 }' | \
         /usr/bin/sort -bu))

   else

      args="${@:2}"   # all arguments starting with the second

      if [[ "${args}" != "${args//[^. [:digit:]]/}" ]]; then 
         printf "%s\n" 'Found at least one invalid rule number or IP address!'
         return 1
      fi

      if [[ "${args//[ [:digit:]]/}" == '' ]]; then 
         argsregex="^0*(${args// /|})"    #  ipfw rule numbers 
      else
         argsregex="(${args// /|})"    #  IP addresses
      fi
    
      #echo $argsregex

      ipaddr_pairs=($(/usr/bin/sudo /sbin/ipfw -d -e -t list | /usr/bin/egrep "${argsregex}" | \
         /usr/bin/awk '/<->/ && ( $8 == "'"${1}"'" || $11 == "'"${1}"'" )  {print $7, $10 }' | /usr/bin/sort -bu))

      dynrules=($(/usr/bin/sudo /sbin/ipfw -d -e -t list | /usr/bin/egrep "${argsregex}" | \
         /usr/bin/awk '/<->/ && ( $8 == "'"${1}"'" || $11 == "'"${1}"'" )  {print $7, $8, $10, $11, $6, $2, $3, $1 }' | \
         /usr/bin/sort -bu))

   fi


for ((i=0; i < "${#ipaddr_pairs[@]}"; i++)); do 

   # byte
   #bytesum=$(printf "%s\n" "${dynrules[@]}" | \
        #/usr/bin/awk '$1 == "'"${ipaddr_pairs[${i}]% *}"'" && $3 == "'"${ipaddr_pairs[${i}]#* }"'" { print $7 }' | \
        #/usr/bin/awk '{ total = total + $1 } END { print total }')

   # mega byte
   bytesum=$(printf "%s\n" "${dynrules[@]}" | \
        /usr/bin/awk '$1 == "'"${ipaddr_pairs[${i}]% *}"'" && $3 == "'"${ipaddr_pairs[${i}]#* }"'" { print $7 }' | \
        /usr/bin/awk 'BEGIN { total=0 }; { total = (total + $1) / (1024*1024.0) } END { print total }')


   proto=$(printf "%s\n" "${dynrules[@]}" | \
        /usr/bin/awk '$1 == "'"${ipaddr_pairs[${i}]% *}"'" && $3 == "'"${ipaddr_pairs[${i}]#* }"'" { print $5 }' | \
        /usr/bin/sort -bu)


   rule=$(printf "%s\n" "${dynrules[@]}" | \
        /usr/bin/awk '$1 == "'"${ipaddr_pairs[${i}]% *}"'" && $3 == "'"${ipaddr_pairs[${i}]#* }"'" { print $NF }' | \
        /usr/bin/sort -bu)


   ports=$(printf "%s\n" "${dynrules[@]}" | \
        /usr/bin/awk '$1 == "'"${ipaddr_pairs[${i}]% *}"'" && $3 == "'"${ipaddr_pairs[${i}]#* }"'" { print $2,$4 }' | \
        /usr/bin/sort -bu)


   # byte
   #printf "\e[1mbytes\e[m: %-20s %-10s %-40s \e[1mrules\e[m: %-25s \e[1mports\e[m: %-30s\n" \
        #"${bytesum}" "${proto//[[:cntrl:]]/, }" "${ipaddr_pairs[${i}]% *}  ::  ${ipaddr_pairs[${i}]#* }" \
        #"${rule//[[:cntrl:]]/, }" "${ports//[[:cntrl:]]/, }"


   # mega byte
   printf "\e[1mmbytes\e[m: %-20.6f %-10s %-40s \e[1mrules\e[m: %-25s \e[1mports\e[m: %-30s\n" \
        "${bytesum}" "${proto//[[:cntrl:]]/, }" "${ipaddr_pairs[${i}]% *}  ::  ${ipaddr_pairs[${i}]#* }" \
        "${rule//[[:cntrl:]]/, }" "${ports//[[:cntrl:]]/, }"

done | /usr/bin/sort -rn -k 2,2

   export IFS=${OIFS}
   return 0

}


# usage:
# porttraffic [portnum]
# porttraffic [portnum] [rulenum1] [rulenum2] [rulenum3] ...
# porttraffic [portnum] [ipaddr1] [ipaddr2] [ipaddr3] ...


porttraffic 80
porttraffic 80 5200 12700 7100
porttraffic 80 xx.xxx.xx.xxx xxx.xxx.xx.xxx



#------------------------------------------------------------------------------



# list rule-specific internet traffic

function ruletraffic() {

   declare args argsregex dynrules ipaddr_pairs

   OIFS=${IFS}
   IFS=$'\n'

   if [[ $# -eq 0 ]]; then
   
      printf "%s\n" 'No rule number given!'
      return 1
   
   elif [[ $# -eq 1 ]]; then

      if [[ "${1//[[:digit:]]/}" != '' ]]; then 
         printf "%s\n" 'Invalid rule number!'
         return 1
      fi

      ipaddr_pairs=($(/usr/bin/sudo /sbin/ipfw -d -e -t list | /usr/bin/egrep "^0*${1}" | \
         /usr/bin/awk '/<->/ {print $7, $10}' | /usr/bin/sort -bu))

      dynrules=($(/usr/bin/sudo /sbin/ipfw -d -e -t list | /usr/bin/egrep "^0*${1}" | \
         /usr/bin/awk '/<->/ {print $7, $8, $10, $11, $6, $2, $3, $1}' | /usr/bin/sort -bu))

      #echo "rulenum: ${1}"
      #echo "ipaddr_pairs: ${ipaddr_pairs[@]/%/$'\n'}"
      #echo "dynrules: ${dynrules[@]/%/$'\n'}"

   else

      args="${@}"

      if [[ "${args//[ [:digit:]]/}" != '' ]]; then 
         printf "%s\n" 'Found at least one invalid rule number!'
         return 1
      fi

      argsregex="^0*(${args// /|})"    #  ipfw rule numbers 

      ipaddr_pairs=($(/usr/bin/sudo /sbin/ipfw -d -e -t list | /usr/bin/egrep "${argsregex}" | \
         /usr/bin/awk '/<->/ {print $7, $10}' | /usr/bin/sort -bu))

      dynrules=($(/usr/bin/sudo /sbin/ipfw -d -e -t list | /usr/bin/egrep "${argsregex}" | \
         /usr/bin/awk '/<->/ {print $7, $8, $10, $11, $6, $2, $3, $1}' | /usr/bin/sort -bu))

      #echo "rulenums: ${@/%/$'\n'}"
      #echo "argsregex: ${argsregex}"
      #echo "ipaddr_pairs: ${ipaddr_pairs[@]/%/$'\n'}"
      #echo "dynrules: ${dynrules[@]/%/$'\n'}"

   fi


for ((i=0; i < "${#ipaddr_pairs[@]}"; i++)); do 

   # byte
   #bytesum=$(printf "%s\n" "${dynrules[@]}" | \
        #/usr/bin/awk '$1 == "'"${ipaddr_pairs[${i}]% *}"'" && $3 == "'"${ipaddr_pairs[${i}]#* }"'" { print $7 }' | \
        #/usr/bin/awk '{ total = total + $1 } END { print total }')

   # mega byte
   bytesum=$(printf "%s\n" "${dynrules[@]}" | \
        /usr/bin/awk '$1 == "'"${ipaddr_pairs[${i}]% *}"'" && $3 == "'"${ipaddr_pairs[${i}]#* }"'" { print $7 }' | \
        /usr/bin/awk 'BEGIN { total=0 }; { total = (total + $1) / (1024*1024.0) } END { print total }')


   proto=$(printf "%s\n" "${dynrules[@]}" | \
        /usr/bin/awk '$1 == "'"${ipaddr_pairs[${i}]% *}"'" && $3 == "'"${ipaddr_pairs[${i}]#* }"'" { print $5 }' | \
        /usr/bin/sort -bu)


   rule=$(printf "%s\n" "${dynrules[@]}" | \
        /usr/bin/awk '$1 == "'"${ipaddr_pairs[${i}]% *}"'" && $3 == "'"${ipaddr_pairs[${i}]#* }"'" { print $NF }' | \
        /usr/bin/sort -bu)


   ports=$(printf "%s\n" "${dynrules[@]}" | \
        /usr/bin/awk '$1 == "'"${ipaddr_pairs[${i}]% *}"'" && $3 == "'"${ipaddr_pairs[${i}]#* }"'" { print $2,$4 }' | \
        /usr/bin/sort -bu)


   #echo "field 1: ${ipaddr_pairs[${i}]% *}"
   #echo "field 2: ${ipaddr_pairs[${i}]#* }"
   #echo "bytesum: ${bytesum}"
   #echo "proto: ${proto//[[:cntrl:]]/, }"
   #echo "rule: ${rule//[[:cntrl:]]/, }"
   #echo "ports: ${ports//[[:cntrl:]]/, }"


   # byte
   #printf "\e[1mbytes\e[m: %-20s %-10s %-40s \e[1mrules\e[m: %-25s \e[1mports\e[m: %-30s\n" \
        #"${bytesum}" "${proto//[[:cntrl:]]/, }" "${ipaddr_pairs[${i}]% *}  ::  ${ipaddr_pairs[${i}]#* }" \
        #"${rule//[[:cntrl:]]/, }" "${ports//[[:cntrl:]]/, }"


   # mega byte
   printf "\e[1mmbytes\e[m: %-20.6f %-10s %-40s \e[1mrules\e[m: %-25s \e[1mports\e[m: %-30s\n" \
        "${bytesum}" "${proto//[[:cntrl:]]/, }" "${ipaddr_pairs[${i}]% *}  ::  ${ipaddr_pairs[${i}]#* }" \
        "${rule//[[:cntrl:]]/, }" "${ports//[[:cntrl:]]/, }"

done | /usr/bin/sort -rn -k 2,2

   export IFS=${OIFS}
   return 0
}


# usage:
# ruletraffic [rulenum]
# ruletraffic [rulenum1] [rulenum2] [rulenum3] ...

ruletraffic 5200
ruletraffic 5200 12700 7100

deny_rules="$(/usr/bin/sudo /sbin/ipfw show | /usr/bin/awk '/deny/ {printf $1" "}')"
echo $deny_rules

ruletraffic $deny_rules


#-------------------------------


/usr/sbin/netstat -n -ibd
/usr/bin/sudo /usr/sbin/tcpdump -vvv -ni en0 not ip


Further information:

- IPFWstats
- ipfwsnmp
- ipfwsnmp (patched)
- ipfw counters (field 3)
- Multi Router Traffic Grapher
- cricket

Enable internet traffic via specified ports through ipfw

# cf. Example ipfw ruleset, http://codesnippets.joyent.com/posts/show/1267

# choose appropriate numbers for num1 & num2 according to your ipfw ruleset

/usr/bin/sudo /sbin/ipfw list
/usr/sbin/sysctl -n net.inet.ip.fw.autoinc_step

function free_ipfw_rule_num() {
   declare -i num1=6701 num2=6799 lastipfwnum
   if [[ $(/usr/sbin/sysctl -n net.inet.ip.fw.autoinc_step) -ne 100 ]]; then 
      printf "%s\x21\n" "sysctl -n net.inet.ip.fw.autoinc_step is not set to 100"
      return 1
   fi
   lastipfwnum=$(/usr/bin/sudo /sbin/ipfw list | /usr/bin/tail -n 2 | /usr/bin/head -n 1 | /usr/bin/awk '{print $1}')
   if [[ $num2 -ge $lastipfwnum ]]; then 
      printf "%s\x21\n" "${num2} is greater than or equal to ${lastipfwnum}"
      return 1
   fi
   while $(/usr/bin/sudo /sbin/ipfw show ${num1} &>/dev/null) ; do
      let "num1 += 1"
      if [[ $num1 -gt $num2 ]]; then num1=; break; return 1; fi
   done
   printf "%s\n" "${num1}"
   return 0
}


function openport() {
   declare portnum rulenum
   if [[ $# -ne 1 ]]; then printf "%s\n" "Wrong number of arguments: $#"; return 1; fi
   portnum="${1//[^[:digit:]]/}"
   if [[ -z $portnum ]]; then printf "%s\n" "No valid port number given: ${1}"; return 1; fi
   if [[ $portnum -gt 65535 ]]; then printf "%s\n" "Given port number is greater than 65535: ${portnum}"; return 1; fi
   rulenum=$(free_ipfw_rule_num)
   /usr/bin/sudo /sbin/ipfw -q add ${rulenum} allow all from any to any dst-port ${portnum} keep-state
   printf "%s\n" "... opening ipfw rule no. ${rulenum} for internet access via port ${portnum}"
   return 0
}


function closeport() {
   declare portnum rulenum
   if [[ $# -ne 1 ]]; then printf "%s\n" "Wrong number of arguments: $#"; return 1; fi
   portnum="${1//[^[:digit:]]/}"
   if [[ -z $portnum ]]; then printf "%s\n" "No valid port number given: ${1}"; return 1; fi
   if [[ $portnum -gt 65535 ]]; then printf "%s\n" "Given port number is greater than 65535: ${portnum}"; return 1; fi
   rulenum=$(/usr/bin/sudo /sbin/ipfw list | /usr/bin/awk "/from +any +to +any +dst-port +${portnum} +keep-state[[:space:]]*$/ {print \$1}")
   if [[ -z "${rulenum}" ]]; then printf "%s\n" "No ipfw rule for port number: ${portnum}"; return 1; fi
   /usr/bin/sudo /sbin/ipfw -q delete ${rulenum}
   printf "%s\n%s\n" "... deleting ipfw rule no. ${rulenum//[[:cntrl:]]/ }" "... closing internet access via port: ${portnum}"
   return 0
}


openport 43
openport 43
openport 43

/usr/bin/sudo /sbin/ipfw show [rulenum]     # ... allow ip from any to any dst-port 43 keep-state

closeport 43

Enable access to specified web sites through ipfw

# cf. Example ipfw ruleset, http://codesnippets.joyent.com/posts/show/1267

# choose appropriate numbers for num1 & num2 according to your ipfw ruleset

/usr/bin/sudo /sbin/ipfw list
/usr/sbin/sysctl -n net.inet.ip.fw.autoinc_step

function free_ipfw_rule_num() {
   declare -i num1=6701 num2=6799 lastipfwnum
   if [[ $(/usr/sbin/sysctl -n net.inet.ip.fw.autoinc_step) -ne 100 ]]; then 
      printf "%s\x21\n" "sysctl -n net.inet.ip.fw.autoinc_step is not set to 100"
      return 1
   fi
   lastipfwnum=$(/usr/bin/sudo /sbin/ipfw list | /usr/bin/tail -n 2 | /usr/bin/head -n 1 | /usr/bin/awk '{print $1}')
   if [[ $num2 -ge $lastipfwnum ]]; then 
      printf "%s\x21\n" "${num2} is greater than or equal to ${lastipfwnum}"
      return 1
   fi
   while $(/usr/bin/sudo /sbin/ipfw show ${num1} &>/dev/null) ; do
      let "num1 += 1"
      if [[ $num1 -gt $num2 ]]; then num1=; break; return 1; fi
   done
   printf "%s\n" "${num1}"
   return 0
}


function opensite() {
   declare ipnum ipfwnum
   if [[ $# -eq 0 ]] || [[ $# -gt 2 ]]; then printf "%s\n" "Wrong number of arguments: $#"; return 1; fi
   ipnum=$(/usr/bin/dig +short ${1} 2>/dev/null | /usr/bin/tail -n 1; exit ${PIPESTATUS[0]})
   if [[ $? -ne 0 ]] || [[ -z "${ipnum}" ]]; then 
      printf "%s\n%s\n" "Are you connected to the internet?" "man dig could not find the IP address of: ${1}"
      return 1
   fi
   ipfwnum=$(free_ipfw_rule_num)
   if [[ $# -eq 1 ]]; then
      /usr/bin/sudo /sbin/ipfw