Network address processing code snippet

format_subnet.sh

# format_subnet <destination variable> <subnet>
# <subnet> format: 192.168.1.1/24
format_subnet() {
[ "$#" -ge 2 ] || return 1

local insubnet="$2"
local address=${insubnet%/*}
local mlen=${insubnet#*/}
local FULL_MASK_INT=$((0xFFFFFFFF))
local MASK_LEN=$mlen
local LEFT_MOVE="$(( 32 - ${MASK_LEN} ))"
local N="$(( ${FULL_MASK_INT} << ${LEFT_MOVE} ))"
local M1="$(( ($N & 0xFF000000) >> 24 ))"
local M2="$(( ($N & 0x00FF0000) >> 16 ))"
local M3="$(( ($N & 0x0000FF00) >> 8 ))"
local M4="$((  $N & 0x000000FF ))"
#local mask="$M1.$M2.$M3.$M4"
local outsubnet="$(echo $(for i in $(seq 1 4); do eval "echo \$(( \$(echo $address|cut -f$i -d'.') & \$M$i ))"; done)|sed 's| |.|g')/$mlen"
eval "$1=\$outsubnet"
}

# need 64-bit system
# format_subnet6 <destination variable> <subnet6>
# <subnet6> format: fc02:2f31:3376::345/60
format_subnet6() {
[ "$#" -ge 2 ] || return 1

local insubnet="$2"
local address=${insubnet%/*}
local mlen=${insubnet#*/}
# ipv4 suffix format
local ipv4_suffix=$(echo ${address}|sed -En "s|.+:([0-9]+(\.[0-9]+){3})$|\1|p")
if [ -n "$ipv4_suffix" ]; then
address=\
$(echo $address|sed "s|$ipv4_suffix|\
$(printf %x $(( $(echo $ipv4_suffix|cut -f1 -d'.') & 0xFF )) | sed -E 's|^([0-9])$|0\1|')\
$(printf %x $(( $(echo $ipv4_suffix|cut -f2 -d'.') & 0xFF )) | sed -E 's|^([0-9])$|0\1|')\
:\
$(printf %x $(( $(echo $ipv4_suffix|cut -f3 -d'.') & 0xFF )) | sed -E 's|^([0-9])$|0\1|')\
$(printf %x $(( $(echo $ipv4_suffix|cut -f4 -d'.') & 0xFF )) | sed -E 's|^([0-9])$|0\1|')\
|")
fi
# double colon
if [ -n "$(echo $address|grep '::')" ]; then
local blocks=$(( 8 - $(echo $address|awk '{print gsub(/[[:xdigit:]]+/,"&")}') ))
address=\
$(echo $address|sed "s|::|:\
$(for i in $(seq 1 $blocks); do echo 0:; done|tr -d '\n')\
|")
address=${address#:}; address=${address%:}
fi
local HALF_MASK_INT=$((0xFFFFFFFFFFFFFFFF))
local MASK_LEN=$mlen
local H_MASK=$([ "$MASK_LEN" -lt  "64" ] && echo     $MASK_LEN                             || echo 64)
local L_MASK=$([ "$MASK_LEN" -lt "128" ] && echo $(( $MASK_LEN - 64 )) | sed '/-/ s|.*|0|' || echo 64)
local H_LEFT_MOVE=$(( 64 - $H_MASK ))
local L_LEFT_MOVE=$(( 64 - $L_MASK ))
local H_N L_N
[ "${H_LEFT_MOVE}" -eq "64" ] && H_N=0 || H_N="$(( ${HALF_MASK_INT} << ${H_LEFT_MOVE} ))"
[ "${L_LEFT_MOVE}" -eq "64" ] && L_N=0 || L_N="$(( ${HALF_MASK_INT} << ${L_LEFT_MOVE} ))"
local M1="$(( (($H_N & 0xFFFF000000000000) >> 48 ) & 0xFFFF ))"
local M2="$((  ($H_N & 0x0000FFFF00000000) >> 32 ))"
local M3="$((  ($H_N & 0x00000000FFFF0000) >> 16 ))"
local M4="$((   $H_N & 0x000000000000FFFF  ))"
local M5="$(( (($L_N & 0xFFFF000000000000) >> 48 ) & 0xFFFF ))"
local M6="$((  ($L_N & 0x0000FFFF00000000) >> 32 ))"
local M7="$((  ($L_N & 0x00000000FFFF0000) >> 16 ))"
local M8="$((   $L_N & 0x000000000000FFFF ))"
#local mask="$M1:$M2:$M3:$M4:$M5:$M6:$M7:$M8"
local outsubnet="$(echo $(for i in $(seq 1 8); do eval "printf %x \$(( 0x\$(echo $address|cut -f$i -d':') & \$M$i ))"; echo ''; done)|sed 's| |:|g')/$mlen"
eval "$1=\$(echo \$outsubnet|sed -E 's|:(0+:)+|::|;s|^0::|::|;s|::0/|::/|')"
}

ip_regexpr.md

IP Regular expression

ipv4: ((25[0-5]|2[0-4][0-9]|[01]?[0-9]{1,2})\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9]{1,2})
ipv4mask: (\/(3[0-2]|[12]?[0-9]))?

ipv6:

(\
([[:xdigit:]]{1,4}:){7}[[:xdigit:]]{1,4}|\
([[:xdigit:]]{1,4}:){1,7}:|\
([[:xdigit:]]{1,4}:){1,6}:[[:xdigit:]]{1,4}|\
([[:xdigit:]]{1,4}:){1,5}(:[[:xdigit:]]{1,4}){1,2}|\
([[:xdigit:]]{1,4}:){1,4}(:[[:xdigit:]]{1,4}){1,3}|\
([[:xdigit:]]{1,4}:){1,3}(:[[:xdigit:]]{1,4}){1,4}|\
([[:xdigit:]]{1,4}:){1,2}(:[[:xdigit:]]{1,4}){1,5}|\
[[:xdigit:]]{1,4}:(:[[:xdigit:]]{1,4}){1,6}|\
:((:[[:xdigit:]]{1,4}){1,7}|:)|\
fe80:(:[[:xdigit:]]{0,4}){0,4}%\w+|\
::(ffff(:0{1,4}){0,1}:){0,1}<ipv4>|\
([[:xdigit:]]{1,4}:){1,4}:<ipv4>\
)

ipv6mask: (\/(12[0-8]|1[01][0-9]|[1-9]?[0-9]))?

Reference

Regular expression that matches valid IPv6 addresses