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Implement IP netmask calculation to replace "ipcalc -m"

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Recently, dracut-network drops depedency on dhcp-client which requires
ipcalc. Thus the dependency chain
"kexec-tools -> dracut-network -> dhcp-client -> ipcalc"
is broken. When NIC is configured to a static IP, kexec-tools depended
on "ipcalc -m" to get netmask. This commit implements the shell
equivalent of "ipcalc -m".

The following test code shows cal_netmask_by_prefix is consistent with
"ipcalc -m",

    #!/bin/bash
    . dracut-module-setup.sh

    for i in {0..128}; do
        mask_expected=$(ipcalc -m fe::/$i| cut -d"=" -f2)
        mask_actual=$(cal_netmask_by_prefix $i "-6")
        if [[ "$mask_expected" != "$mask_actual" ]]; then
            echo "prefix="$i, "expected="$mask_expected, "acutal="$mask_actual
            exit
        fi
    done

    echo "IPv6 tests passed"

    for i in {0..32}; do
        mask_expected=$(ipcalc -m 8.8.8.8/$i| cut -d"=" -f2)
        mask_actual=$(cal_netmask_by_prefix $i "")
        if [[ "$mask_expected" != "$mask_actual" ]]; then
            echo "prefix="$i, "expected="$mask_expected, "acutal="$mask_actual
            exit
        fi
    done

    echo "IPv4 tests passed"

    i=-2
    res=$(cal_netmask_by_prefix "$i" "")
    if [[ $? -ne 1 ]]; then
        echo "cal_netmask_by_prefix should exit when prefix<0"
        exit
    fi

    res=$(cal_netmask_by_prefix "$i" "")
    if [[ $? -ne 1 ]]; then
        echo "cal_netmask_by_prefix should exit when prefix<0"
        exit
    fi

    i=33
    $(cal_netmask_by_prefix $i "")
    if [[ $? -ne 1 ]]; then
        echo "cal_netmask_by_prefix should exit when prefix>32 for IPv4"
        exit
    fi

    i=129
    $(cal_netmask_by_prefix $i "-6")
    if [[ $? -ne 1 ]]; then
        echo "cal_netmask_by_prefix should exit when prefix>128 for IPv4"
        exit
    fi

    echo "Bad prefixes tests passed"

    echo "All tests passed"

Reported-by: Jie Li <jieli@redhat.com>
Signed-off-by: Coiby Xu <coxu@redhat.com>
Acked-by: Kairui Song <kasong@redhat.com>
This commit is contained in:
Coiby Xu 2021-04-08 11:44:26 +08:00 committed by Kairui Song
parent 8b4b7bf808
commit 1ca1b71780
1 changed files with 117 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

119
dracut-module-setup.sh
View File

@ -121,12 +121,122 @@ kdump_setup_dns() {
done < "/etc/resolv.conf"
}
# $1: repeat times
# $2: string to be repeated
# $3: separator
repeatedly_join_str() {
local _count="$1"
local _str="$2"
local _separator="$3"
local i _res
if [[ "$_count" -le 0 ]]; then
echo -n ""
return
fi
i=0
_res="$_str"
((_count--))
while [[ "$i" -lt "$_count" ]]; do
((i++))
_res="${_res}${_separator}${_str}"
done
echo -n "$_res"
}
# $1: prefix
# $2: ipv6_flag="-6" indicates it's IPv6
# Given a prefix, calculate the netmask (equivalent of "ipcalc -m")
# by concatenating three parts,
# 1) the groups with all bits set 1
# 2) a group with partial bits set to 0
# 3) the groups with all bits set to 0
cal_netmask_by_prefix() {
local _prefix="$1"
local _ipv6_flag="$2" _ipv6
local _bits_per_octet=8
local _count _res _octets_per_group _octets_total _seperator _total_groups
local _max_group_value _max_group_value_repr _bits_per_group _tmp _zero_bits
if [[ "$_ipv6_flag" == "-6" ]]; then
_ipv6=1
else
_ipv6=0
fi
if [[ "$_prefix" -lt 0 || "$_prefix" -gt 128 ]] || \
( ((!_ipv6)) && [[ "$_prefix" -gt 32 ]] ); then
derror "Bad prefix:$_prefix for calculating netmask"
exit 1
fi
if ((_ipv6)); then
_octets_per_group=2
_octets_total=16
_seperator=":"
else
_octets_per_group=1
_octets_total=4
_seperator="."
fi
_total_groups=$((_octets_total/_octets_per_group))
_bits_per_group=$((_octets_per_group * _bits_per_octet))
_max_group_value=$(((1 << _bits_per_group) - 1))
if ((_ipv6)); then
_max_group_value_repr=$(printf "%x" $_max_group_value)
else
_max_group_value_repr="$_max_group_value"
fi
_count=$((_prefix/_octets_per_group/_bits_per_octet))
_first_part=$(repeatedly_join_str "$_count" "$_max_group_value_repr" "$_seperator")
_res="$_first_part"
_tmp=$((_octets_total*_bits_per_octet-_prefix))
_zero_bits=$(expr $_tmp % $_bits_per_group)
if [[ "$_zero_bits" -ne 0 ]]; then
_second_part=$((_max_group_value >> _zero_bits << _zero_bits))
if ((_ipv6)); then
_second_part=$(printf "%x" $_second_part)
fi
((_count++))
if [[ -z "$_first_part" ]]; then
_res="$_second_part"
else
_res="${_first_part}${_seperator}${_second_part}"
fi
fi
_count=$((_total_groups-_count))
if [[ "$_count" -eq 0 ]]; then
echo -n "$_res"
return
fi
if ((_ipv6)) && [[ "$_count" -gt 1 ]] ; then
# use condensed notion for IPv6
_third_part=":"
else
_third_part=$(repeatedly_join_str "$_count" "0" "$_seperator")
fi
if [[ -z "$_res" ]] && ((!_ipv6)) ; then
echo -n "${_third_part}"
else
echo -n "${_res}${_seperator}${_third_part}"
fi
}
#$1: netdev name
#$2: srcaddr
#if it use static ip echo it, or echo null
kdump_static_ip() {
local _netdev="$1" _srcaddr="$2" _ipv6_flag
local _netmask _gateway _ipaddr _target _nexthop
local _netmask _gateway _ipaddr _target _nexthop _prefix
_ipaddr=$(ip addr show dev $_netdev permanent | awk "/ $_srcaddr\/.* /{print \$2}")
@ -144,7 +254,12 @@ kdump_static_ip() {
_srcaddr="[$_srcaddr]"
_gateway="[$_gateway]"
else
_netmask=$(ipcalc -m $_ipaddr | cut -d'=' -f2)
_prefix=$(cut -d'/' -f2 <<< "$_ipaddr")
_netmask=$(cal_netmask_by_prefix "$_prefix" "$_ipv6_flag")
if [[ "$?" -ne 0 ]]; then
derror "Failed to calculate netmask for $_ipaddr"
exit 1
fi
fi
echo -n "${_srcaddr}::${_gateway}:${_netmask}::"
fi