#!/usr/bin/env bash
set -e

# bits of this were adapted from lxc-checkconfig
# see also https://github.com/lxc/lxc/blob/lxc-1.0.2/src/lxc/lxc-checkconfig.in

possibleConfigs=(
    '/proc/config.gz'
    "/boot/config-$(uname -r)"
    "/usr/src/linux-$(uname -r)/.config"
    '/usr/src/linux/.config'
)

if [ $# -gt 0 ]; then
    CONFIG="$1"
else
    : ${CONFIG:="${possibleConfigs[0]}"}
fi

if ! command -v zgrep &> /dev/null; then
    zgrep() {
        zcat "$2" | grep "$1"
    }
fi

kernelVersion="$(uname -r)"
kernelMajor="${kernelVersion%%.*}"
kernelMinor="${kernelVersion#$kernelMajor.}"
kernelMinor="${kernelMinor%%.*}"

is_set() {
    zgrep "CONFIG_$1=[y|m]" "$CONFIG" > /dev/null
}
is_set_in_kernel() {
    zgrep "CONFIG_$1=y" "$CONFIG" > /dev/null
}
is_set_as_module() {
    zgrep "CONFIG_$1=m" "$CONFIG" > /dev/null
}

# see https://en.wikipedia.org/wiki/ANSI_escape_code#Colors
declare -A colors=(
    [black]=30
    [red]=31
    [green]=32
    [yellow]=33
    [blue]=34
    [magenta]=35
    [cyan]=36
    [white]=37
)
color() {
    color=()
    if [ "$1" = 'bold' ]; then
        color+=( '1' )
        shift
    fi
    if [ $# -gt 0 ] && [ "${colors[$1]}" ]; then
        color+=( "${colors[$1]}" )
    fi
    local IFS=';'
    echo -en '\033['"${color[*]}"m
}
wrap_color() {
    text="$1"
    shift
    color "$@"
    echo -n "$text"
    color reset
    echo
}

wrap_good() {
    echo "$(wrap_color "$1" white): $(wrap_color "$2" green)"
}
wrap_bad() {
    echo "$(wrap_color "$1" bold): $(wrap_color "$2" bold red)"
}
wrap_warning() {
    wrap_color >&2 "$*" red
}

check_flag() {
    if is_set_in_kernel "$1"; then
        wrap_good "CONFIG_$1" 'enabled'
    elif is_set_as_module "$1"; then
        wrap_good "CONFIG_$1" 'enabled (as module)'
    else
        wrap_bad "CONFIG_$1" 'missing'
    fi
}

check_flags() {
    for flag in "$@"; do
        echo "- $(check_flag "$flag")"
    done
}

check_command() {
    if command -v "$1" >/dev/null 2>&1; then
        wrap_good "$1 command" 'available'
    else
        wrap_bad "$1 command" 'missing'
    fi
}

check_device() {
    if [ -c "$1" ]; then
        wrap_good "$1" 'present'
    else
        wrap_bad "$1" 'missing'
    fi
}

if [ ! -e "$CONFIG" ]; then
    wrap_warning "warning: $CONFIG does not exist, searching other paths for kernel config..."
    for tryConfig in "${possibleConfigs[@]}"; do
        if [ -e "$tryConfig" ]; then
            CONFIG="$tryConfig"
            break
        fi
    done
    if [ ! -e "$CONFIG" ]; then
        wrap_warning "error: cannot find kernel config"
        wrap_warning "  try running this script again, specifying the kernel config:"
        wrap_warning "    CONFIG=/path/to/kernel/.config $0 or $0 /path/to/kernel/.config"
        exit 1
    fi
fi

wrap_color "info: reading kernel config from $CONFIG ..." white
echo

echo 'Generally Necessary:'

echo -n '- '
cgroupSubsystemDir="$(awk '/[, ](cpu|cpuacct|cpuset|devices|freezer|memory)[, ]/ && $3 == "cgroup" { print $2 }' /proc/mounts | head -n1)"
cgroupDir="$(dirname "$cgroupSubsystemDir")"
if [ -d "$cgroupDir/cpu" -o -d "$cgroupDir/cpuacct" -o -d "$cgroupDir/cpuset" -o -d "$cgroupDir/devices" -o -d "$cgroupDir/freezer" -o -d "$cgroupDir/memory" ]; then
    echo "$(wrap_good 'cgroup hierarchy' 'properly mounted') [$cgroupDir]"
else
    if [ "$cgroupSubsystemDir" ]; then
        echo "$(wrap_bad 'cgroup hierarchy' 'single mountpoint!') [$cgroupSubsystemDir]"
    else
        echo "$(wrap_bad 'cgroup hierarchy' 'nonexistent??')"
    fi
    echo "    $(wrap_color '(see https://github.com/tianon/cgroupfs-mount)' yellow)"
fi

if [ "$(cat /sys/module/apparmor/parameters/enabled 2>/dev/null)" = 'Y' ]; then
    echo -n '- '
    if command -v apparmor_parser &> /dev/null; then
        echo "$(wrap_good 'apparmor' 'enabled and tools installed')"
    else
        echo "$(wrap_bad 'apparmor' 'enabled, but apparmor_parser missing')"
        echo -n '    '
        if command -v apt-get &> /dev/null; then
            echo "$(wrap_color '(use "apt-get install apparmor" to fix this)')"
        elif command -v yum &> /dev/null; then
            echo "$(wrap_color '(your best bet is "yum install apparmor-parser")')"
        else
            echo "$(wrap_color '(look for an "apparmor" package for your distribution)')"
        fi
    fi
fi

flags=(
    NAMESPACES {NET,PID,IPC,UTS}_NS
    DEVPTS_MULTIPLE_INSTANCES
    CGROUPS CGROUP_CPUACCT CGROUP_DEVICE CGROUP_FREEZER CGROUP_SCHED CPUSETS
    MACVLAN VETH BRIDGE BRIDGE_NETFILTER
    NF_NAT_IPV4 IP_NF_FILTER IP_NF_TARGET_MASQUERADE
    NETFILTER_XT_MATCH_{ADDRTYPE,CONNTRACK}
    NF_NAT NF_NAT_NEEDED

    # required for bind-mounting /dev/mqueue into containers
    POSIX_MQUEUE
)
check_flags "${flags[@]}"
echo

echo 'Optional Features:'
{
    check_flags MEMCG_SWAP 
    check_flags MEMCG_SWAP_ENABLED
    if  is_set MEMCG_SWAP && ! is_set MEMCG_SWAP_ENABLED; then
        echo "    $(wrap_color '(note that cgroup swap accounting is not enabled in your kernel config, you can enable it by setting boot option "swapaccount=1")' bold black)"
    fi
}

if [ "$kernelMajor" -lt 3 ] || [ "$kernelMajor" -eq 3 -a "$kernelMinor" -le 18 ]; then
    check_flags RESOURCE_COUNTERS
fi

flags=(
    BLK_CGROUP
    IOSCHED_CFQ
    CGROUP_PERF
    CFS_BANDWIDTH
)
check_flags "${flags[@]}"

echo '- Storage Drivers:'
{
    echo '- "'$(wrap_color 'aufs' blue)'":'
    check_flags AUFS_FS | sed 's/^/  /'
    if ! is_set AUFS_FS && grep -q aufs /proc/filesystems; then
        echo "    $(wrap_color '(note that some kernels include AUFS patches but not the AUFS_FS flag)' bold black)"
    fi
    check_flags EXT4_FS_POSIX_ACL EXT4_FS_SECURITY | sed 's/^/  /'

    echo '- "'$(wrap_color 'btrfs' blue)'":'
    check_flags BTRFS_FS | sed 's/^/  /'

    echo '- "'$(wrap_color 'devicemapper' blue)'":'
    check_flags BLK_DEV_DM DM_THIN_PROVISIONING EXT4_FS EXT4_FS_POSIX_ACL EXT4_FS_SECURITY | sed 's/^/  /'

    echo '- "'$(wrap_color 'overlay' blue)'":'
    check_flags OVERLAY_FS EXT4_FS_SECURITY EXT4_FS_POSIX_ACL | sed 's/^/  /'

    echo '- "'$(wrap_color 'zfs' blue)'":'
    echo "  - $(check_device /dev/zfs)"
    echo "  - $(check_command zfs)"
    echo "  - $(check_command zpool)"
} | sed 's/^/  /'
echo

#echo 'Potential Future Features:'
#check_flags USER_NS
#echo
