tiny-cloud/bin/imds

#!/bin/sh
# vim:set filetype=sh:

# Tiny Cloud - Instance MetaData Service client

### configuration, common functions

: "${PREFIX:=/usr}"
: "${LIBDIR:=$PREFIX/lib}"
. "$LIBDIR/tiny-cloud/common"

if [ "$1" = "-h" ] || [ "$1" = "--help" ]; then
	cat <<-EOT
		Usage: imds [-h] { -e | +e | +n | +s | +t | @<alias> | <imds-path> } ...
		  -h           : help
		  -e / +e      : ignore / catch errors
		  -E / +E      : hide / show STDERR
		  +n / +s / +t : insert newline / space / tab
		  <alias> :-
		    hostname       : instance hostname
		    local-hostname : instance local hostname
		    ssh-keys       : instance SSH keys
		    userdata       : instance user data
		    nics           : instance NICs
		    nic:<iface>[,<nic-key> ...] : specific NIC interface
		      <iface>   : network interface (i.e. eth1)
		      <nic-key> :- { -e | +e | +n | +s | +t | @<nic-alias> | <nic-path> }
		        <nic-alias> :-
		          mac         : mac address
		          ipv4        : ipv4 address(es)
		          ipv6        : ipv6 address(es)
		          ipv4-net    : subnet ipv4 network(s)
		          ipv6-net    : subnet ipv6 network(s)
		          ipv4-prefix : delegated ipv4 CIDR(s)
		          ipv6-prefix : delegated ipv6 CIDR(s)
	EOT
	exit 0
fi

### cloud-specific variables/functions

unset \
	IMDS_HEADER \
	IMDS_QUERY
unset -f \
	_imds_token \
	_imds_header \
	_imds_nic_index \
		2>/dev/null || true

### default variables/functions

# Common to many clouds
# Can be overridden in /etc/tiny-cloud.conf
: "${IMDS_ENDPOINT:=169.254.169.254}"
: "${IMDS_ENDPOINTS:=$IMDS_ENDPOINT}"
: "${IMDS_ENDPOINT_CACHE:=$TINY_CLOUD_VAR/.imds-endpoint}"
: "${IMDS_ENDPOINT_WAIT_ATTEMPTS:=10}"

# Common to AWS and NoCloud(ish)
IMDS_HOSTNAME="meta-data/hostname"
IMDS_LOCAL_HOSTNAME="meta-data/local-hostname"
IMDS_SSH_KEYS="meta-data/public-keys"
IMDS_USERDATA="user-data"
IMDS_NICS="meta-data/network/interfaces/macs"
IMDS_MAC="mac"
IMDS_IPV4="local-ipv4s"
IMDS_IPV6="ipv6s"
IMDS_IPV4_NET="subnet-ipv4-cidr-block"
IMDS_IPV6_NET="subnet-ipv6-cidr-blocks"
IMDS_IPV4_PREFIX="ipv4-prefix"
IMDS_IPV6_PREFIX="ipv6-prefix"

_imds_endpoints() {
	local cached e
	cached="$(cat "$IMDS_ENDPOINT_CACHE" 2>/dev/null)" || :
	for e in $IMDS_ENDPOINTS; do
		[ "$e" = "$cached" ] && echo "$e"
	done
	for e in $IMDS_ENDPOINTS; do
		[ "$e" != "$cached" ] && echo "$e"
	done
}

_imds_host_port() {
	local host port
	case "$1" in
		\[*\]:*)
			host="${1#\[}"
			host="${host%%\]*}"
			port="${1##*\]:}"
			;;
		\[*\])
			host="${1#\[}"
			host="${host%\]}"
			port=80
			;;
		*:*)
			host="${1%:*}"
			port="${1##*:}"
			;;
		*)
			host="$1"
			port=80
			;;
	esac
	echo "$host"
	echo "$port"
}

_imds_has_route() {
	local host
	set -- $(_imds_host_port "$1")
	host="$1"
	case "$host" in
		*:*) ip -6 route get "$host" >/dev/null 2>&1 ;;
		[0-9]*.[0-9]*.[0-9]*.[0-9]*) ip route get "$host" >/dev/null 2>&1 ;;
		*) return 0 ;;
	esac
}

_imds() {
	local endpoint endpoints routed attempts=1 cached
	if [ "$IMDS_ENDPOINT_WAIT_ATTEMPTS" -le 0 ]; then
		endpoints="$(_imds_endpoints)"
	fi
	while :; do
		[ -n "$endpoints" ] && break
		endpoints=
		routed=
		for endpoint in $(_imds_endpoints); do
			if _imds_has_route "$endpoint"; then
				endpoints="$endpoints $endpoint"
				routed=1
			fi
		done
		[ -n "$routed" ] && break
		[ "$attempts" -ge "$IMDS_ENDPOINT_WAIT_ATTEMPTS" ] && {
			endpoints="$(_imds_endpoints)"
			break
		}
		sleep 1
		attempts=$((attempts + 1))
	done
	for endpoint in $endpoints; do
		IMDS_ENDPOINT="$endpoint"
		IMDS_CURRENT_ENDPOINT="$endpoint"
		wget --quiet --timeout 1 --output-document - \
			--header "$(_imds_header)" \
			"http://$endpoint/$IMDS_URI/$1$IMDS_QUERY" && {
				cached="$(cat "$IMDS_ENDPOINT_CACHE" 2>/dev/null)" || :
				[ "$endpoint" = "$cached" ] || echo "$endpoint" 2>/dev/null > "$IMDS_ENDPOINT_CACHE" || :
				return 0
			}
	done
	return 1
}

_imds_userdata() { _imds "$IMDS_USERDATA"; }

_imds_ssh_keys() {
	local key
	for key in $(_imds "$IMDS_SSH_KEYS"); do
		_imds "$IMDS_SSH_KEYS/${key%=*}/openssh-key"
		echo
	done | sort -u
}

_imds_nic_index() { cat "$SYS/class/net/$1/address"; }

### load cloud-specific variables and functions

if [ "$CLOUD" = "auto" ]; then
	CLOUD=$(cat "$TINY_CLOUD_VAR/.autodetect")
fi

if [ ! -d "$LIBDIR/tiny-cloud/cloud/$CLOUD" ]; then
	echo "ERROR: Unknown Cloud '$CLOUD'" >&2
fi
. "$LIBDIR/tiny-cloud/cloud/$CLOUD/imds"

### non-overrideable functions

imds() {
	local cmd args key rv err=1 stderr=1
	while [ -n "$1" ]; do
		cmd=_imds
		args=
		key="$1"; shift
		case $key in
			# error handling/output
			-e) err=0; continue ;;	# ignore
			+e) err=1; continue ;;	# return
			-E) stderr=0; continue ;; # hide
			+E) stderr=1; continue ;; # show
			# TODO: retry/deadline
			# output control
			+n) printf "\n"; continue ;;	# insert newline
			+s) printf " "; continue ;;		# insert space
			+t) printf "\t"; continue ;;	# insert tab
			# key aliasing
			@hostname)			args="$IMDS_HOSTNAME" ;;
			@local-hostname)	args="$IMDS_LOCAL_HOSTNAME" ;;
			@ssh-keys)			cmd=_imds_ssh_keys ;;
			@userdata)			cmd=_imds_userdata ;;
			@nics)				args="$IMDS_NICS" ;;
			@nic:*)
				cmd=imds
				args=$(_imds_nic_args $(echo "${key#@nic:}" | tr , ' '))
				;;
			# use key verbatim
			*) args="$key" ;;
		esac
		# TODO: retry/deadline
		if [ $stderr = 1 ]; then
			"$cmd" $args
			rv=$?
		else
			"$cmd" $args 2>/dev/null
			rv=$?
		fi
		[ $err -eq 0 ] && continue
		[ $rv = "0" ] || return $rv
	done
}

_imds_nic_args() {
	local key nic
	nic=$(_imds_nic_index "$1") || return 1
	if [ -z "$2" ]; then
		echo "$IMDS_NICS/$nic"
		return
	fi
	while [ -n "$2" ]; do
		key="$2"
		shift
		case "$key" in
			@mac)		   key="$IMDS_MAC" ;;
			@ipv4)		  key="$IMDS_IPV4" ;;
			@ipv6)		  key="$IMDS_IPV6" ;;
			@ipv4-net)	  key="$IMDS_IPV4_NET" ;;
			@ipv6-net)	  key="$IMDS_IPV6_NET" ;;
			@ipv4-prefix)   key="$IMDS_IPV4_PREFIX" ;;
			@ipv6-prefix)   key="$IMDS_IPV6_PREFIX" ;;
			# error/output control passthrough
			-e|+[enst])	 printf "$key\n"; continue ;;
		esac
		printf "$IMDS_NICS/$nic/$key\n"
	done
}

imds "$@"