#!/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
 }

 
 color() {

 	local codes=()

 	if [ "$1" = 'bold' ]; then

 		codes=( "${codes[@]}" '1' )

 		shift
 	fi

 	if [ "$#" -gt 0 ]; then
 		local code=
 		case "$1" in
 			# see https://en.wikipedia.org/wiki/ANSI_escape_code#Colors
 			black) code=30 ;;
 			red) code=31 ;;
 			green) code=32 ;;
 			yellow) code=33 ;;
 			blue) code=34 ;;
 			magenta) code=35 ;;
 			cyan) code=36 ;;
 			white) code=37 ;;
 		esac
 		if [ "$code" ]; then
 			codes=( "${codes[@]}" "$code" )
 		fi

 	fi
 	local IFS=';'

 	echo -en '\033['"${codes[*]}"'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
 }
 

 check_distro_userns() {
 	source /etc/os-release 2>/dev/null || /bin/true
 	if [[ "${ID}" =~ ^(centos|rhel)$ && "${VERSION_ID}" =~ ^7 ]]; then
 		# this is a CentOS7 or RHEL7 system
 		grep -q "user_namespace.enable=1" /proc/cmdline || {
 			# no user namespace support enabled
 			wrap_bad "  (RHEL7/CentOS7" "User namespaces disabled; add 'user_namespace.enable=1' to boot command line)"
 		}
 	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 MEMCG

 	KEYS

 	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 USER_NS

 	check_distro_userns

 }
 {

 	check_flags SECCOMP
 }
 {

 	check_flags CGROUP_PIDS
 }
 {

 	check_flags MEMCG_KMEM MEMCG_SWAP 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
 

 if [ "$kernelMajor" -lt 3 ] || [ "$kernelMajor" -eq 3 -a "$kernelMinor" -le 13 ]; then
 	netprio=NETPRIO_CGROUP
 else
 	netprio=CGROUP_NET_PRIO
 fi
 

 flags=(

 	BLK_CGROUP IOSCHED_CFQ BLK_DEV_THROTTLING

 	CGROUP_PERF

 	CGROUP_HUGETLB

 	NET_CLS_CGROUP $netprio

 	CFS_BANDWIDTH FAIR_GROUP_SCHED RT_GROUP_SCHED

 )
 check_flags "${flags[@]}"
 

 check_flags EXT3_FS EXT3_FS_XATTR EXT3_FS_POSIX_ACL EXT3_FS_SECURITY
 if ! is_set EXT3_FS || ! is_set EXT3_FS_XATTR || ! is_set EXT3_FS_POSIX_ACL || ! is_set EXT3_FS_SECURITY; then
 	echo "    $(wrap_color '(enable these ext3 configs if you are using ext3 as backing filesystem)' bold black)"
 fi
 
 check_flags EXT4_FS EXT4_FS_POSIX_ACL EXT4_FS_SECURITY
 if ! is_set EXT4_FS || ! is_set EXT4_FS_POSIX_ACL || ! is_set EXT4_FS_SECURITY; then
 	echo "    $(wrap_color 'enable these ext4 configs if you are using ext4 as backing filesystem' bold black)"
 fi
 

 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
 

 	echo '- "'$(wrap_color 'btrfs' blue)'":'

 	check_flags BTRFS_FS | sed 's/^/  /'
 

 	echo '- "'$(wrap_color 'devicemapper' blue)'":'

 	check_flags BLK_DEV_DM DM_THIN_PROVISIONING | sed 's/^/  /'

 	echo '- "'$(wrap_color 'overlay' blue)'":'

 	check_flags OVERLAY_FS | sed 's/^/  /'

 
 	echo '- "'$(wrap_color 'zfs' blue)'":'
 	echo "  - $(check_device /dev/zfs)"
 	echo "  - $(check_command zfs)"
 	echo "  - $(check_command zpool)"

 } | sed 's/^/  /'
 echo