overlay-boot/functions

# This file implements common functions for all boot scripts

# Rerun with sudo if needed
[ $(id -u) = 0 ] || exec sudo $0 $@

# Function to write a message and exit with error code
die() {
    echo "$*" >&2
    exit 1
}

# Function to setup subhost name and log file
subhost_name() {
    CONFIG="$1"
    [ -r "$CONFIG" ] || die "Cannot use $CONFIG"
    config NAME "$(basename $CONFIG .conf)"
    config LOG /tmp/oly-$NAME.log
}

# Function to set up all subhost configuration
subhost_config() {

    config BASE
    BASE="$(cd $(dirname $CONFIG); realpath $BASE)"
    [ -z "$BASE" ] && die "BASE is unset; bogus $CONFIG ?"
    [ -d "$BASE" ] || die "$BASE is not a directory; bogus $CONFIG ?"
    cd "$BASE" || die "$BASE is inaccessible"

    config CABLES ""
    config LIVE "$BASE/live"
    config UPPER "$BASE/root"
    config WORK "$BASE/work"
    config LOWER "/"
    config START "!networking ssh"
    config PREMOUNT "$PROGRAMDIR/overlay-premount"
    config POSTMOUNT "$PROGRAMDIR/overlay-postmount"
    config INIT "$PROGRAMDIR/overlay-init"
    config RAM_SIZE 50M
}

# function to reverse the $* words
reverse() {
    local OUT=""
    for w in $* ; do OUT="$w $OUT" ; done
    echo "${OUT% }"
}

# grab and set a configuration variable
# $1 = variable, [ $2 = default .. error otherwise ]
config() {
    local V W
    read V <<EOF
$(sed "/^$1=.*/{s|^$1=||;s|^\\s*||;s|\\s*\$||;b};d" $CONFIG)
EOF
    if [ -z "$V" ] ; then
	[ $# -lt 2 ] && die "Missing $1=... in $CONFIG"
	V="$2" # use the given default
    elif [ -z "${V##!*}" ] ; then
	read W <<EOF
$(${V#!})
EOF
	[ -z "$W" ] && die "bad $1 config: $V"
	V="$W"
    fi
    eval $1="'$V'"
    eval echo "$1=$V" >&2
}

# Install a default $1/etc/network/interfaces on the subhost root $1
setup_networking() {
    [ -r $1/etc/network/interfaces ] && return 0
    mkdir -p $1/etc/network
    cat <<EOF >> $1/etc/network/interfaces
# Generated for $NAME subhost
auto lo
iface lo inet loopback
EOF
    for IF in $(ip netns exec $NAME ip link show | grep "^eth") ; do
	cat <<EOF >> $1/etc/network/interfaces

auto eth$i
iface eth$i inet manual
EOF
    done
}

# Setup the network namespace for the given $CABLES
# $1=netns ( $2="br=mac" .. )
setup_veth_cables() {
    local NETNS BR IF MAC C i ADD
    NETNS="$1"
    shift 1
    i=0
    for C in "$@" ; do
	IF=$NETNS$i
	MAC="${C#*=}"
	[ -z "$MAC" ] || MAC="address $MAC"
	ip link add $IF type veth peer name eth$i $MAC netns $NETNS
	ip link set $IF up
	BR="${C%=*}"
	if [ -z "$BR" ] ; then
	    ip link set $IF
	    ifup $IF
	else
	    brctl addif $BR $IF
	fi
	i=$((i+1))
    done
}

# Set up an overlay for $name on $live, with a new tmpfs on its /run,
# and "install" a "reaper" as the upcoming pid 1
setup_overlay() {
    local NAME="$1" LIVE="$2" LOWER="$3" UPPER="$4" WORK="$5"

    echo setup_overlay "$NAME" "$LIVE" "$LOWER" "$UPPER" "$WORK"

    if grep -qE "^[^ ]+ $LIVE " /proc/mounts ; then
	die "$LIVE already has a mount"
    fi

    [ -d "$UPPER" ] || die "UPPER=$UPPER is not a directory"
    [ -d "$LOWER" ] || die "LOWER=LOWPER is not a directory"
    [ -d "$LIVE" ] || die "LOWER=LOWPER is not a directory"
    [ -x "${PREMOUNT%% *}" ] || die "PREMOUNT=${PREMOUNT%% *} not executable"
    [ -f "${PREMOUNT%% *}" ] || die "PREMOUNT='$PREMOUNT' is not a command"
    [ -x "${POSTMOUNT%% *}" ] || \
	die "POSTMOUNT=${POSTMOUNT%% *} not executable"
    [ -f "${POSTMOUNT%% *}" ] || \
	die "POSTMOUNT='$POSTMOUNT' is not a command"

    # UPPER is the same as LOWER then skip the overlay mount
    if [ "$UPPER" != "$LOWER" ] ; then
	# sanity check
	[ -d "$WORK" ] || die "WORK=$WORK is not a directory"

	env CONFIG="$CONFIG" $PREMOUNT "$UPPER"

	OLY="-olowerdir=$3,upperdir=$UPPER,workdir=$5"
	if ! mount -t overlay "$OLY" $1 $2 ; then
	    umount -R "$UPPER/dev"
	    umount "$UPPER/run"
	    die "Cannot set up the overlay mount $2"
	fi
    elif [ "$LIVE" != "$UPPER" ] ; then
	# With UPPER = LOWER we rather make a bind mount to LIVE
	env CONFIG="$CONFIG" $PREMOUNT "$UPPER"
	mount --bind $UPPER $LOWER
    fi

    env CONFIG="$CONFIG" $POSTMOUNT "LIVE" "$UPPER" 
}

# Find the "unshare" process for $1 and echo the its pid and the pids
# of its child processes.
is_live() {
    local NAME=$1
    local USPID="$(pgrep -f "unshare.* $NAME ")"
    [ -z "$USPID" ] && return 1
    echo "$USPID $(ps -hopid --ppid=$USPID)"
}

# Find all overlay-boot processes and list their config files
list_running() {
    pgrep -a overlay-boot | awk '{print $4}'
}