#!/bin/bash
#
# Boot up subhost as if a vitual machine.
# Allow CONFIG given as environment
#

#set -x

: ${NAME=$1}
: ${NSNAME=$NAME}
: ${SUBHOST=/opt/subhost/$NAME}
: ${TARGET=$SUBHOST/live}
: ${CONFIG=$SUBHOST/config}

# sets DISKS=( ... ) and BRIDGES=( ... )
[ -r "$CONFIG" ] && . $CONFIG

if [ -z "$DISKS" ] ; then
    echo "Missing CONFIG" >&2
    exit 1
fi

# Generate a mac address for given arguments pass through 40-bit b2sum
# and with 02: prefix.
macaddr() {
    local V="$(b2sum -l 40 <<< "$*" )"
    V="$( sed 's/\(..\)/\1:/g' <<< "${V}aaaaaaaaaa")"
    echo "02:${V:0:14}"
}

# Setup the subhost network namespace and link up the host side
setup_cables() {
    E=0
    [ -e /var/run/netns/$NSNAME ] || ip netns add $NSNAME
    for BRIDGE in ${BRIDGES[@]} ; do
	IF=$NAME$E
	B=( ${BRIDGE/:/ } )
	BRIDGE="${B[0]}"
	MAC="${B[1]}"
	[ -z "$MAC" ] && MAC="$(macaddr "$(hostname)" "$NAME" "$IF")"
	brctl show $BRIDGE >& /dev/null || brctl addbr $BRIDGE
	ip link add $IF type veth peer name eth$E address $MAC netns $NSNAME 
	ip link set $IF up
	[ -n "$BRIDGE" ] && brctl addif $BRIDGE $IF
	E=$((E+1))
    done
}

# loopdev path -- Make a named device node for a loop device
copyloop() {
    local MKNOD="mknod $(basename $2) b $(stat -c "%t %T" $1)"
    if [ -e "$2" ] ; then
	rm -f $2
    else
	mkdir -p $(dirname $2)
    fi
    ( cd $(dirname $2) && $MKNOD )
}

# diskid image partition# -- set up parition device node
mkdevnode() {
    local LOOP="$(losetup -j "$3" | sed 's/:.*//')"
    [ -z "$LOOP" ] && LOOP="$(losetup -f --show "$3")"
    grep -q $TARGET /proc/mounts || \
	mount ${LOOP}p$2 $TARGET
    copyloop $LOOP $TARGET/dev/$1
    copyloop ${LOOP}p$2 $TARGET/dev/$1$2
}

# Setup device nodes for VM loopbacks according to $DISKS
setup_rootfs() {
    for DISK in ${DISKS[@]} ; do
	D=( $(echo $DISK | tr : ' ') )
	case "${D[0]}" in
	    vd*|sd*)
		mkdevnode "${D[@]}"
		;;
	    *)
		echo "Unknown disk type ${D[0]}" >&2
		exit 1
		;;
	esac
    done
}

# Change $TARGET/dev/console 
setup_console() {
    local SCRIPT=$$
    CONSOLE=$TARGET/dev/console
    rm -f $CONSOLE
    ln -s $(tty) $CONSOLE
}

####################
# Pretend boot

setup_cables
setup_rootfs
setup_console

######################################################################
# Run the subhost init
ip netns exec $NSNAME unshare --fork --pid --mount-proc --kill-child \
     --uts --ipc --mount --cgroup chroot $TARGET /sbin/init
######################################################################

# Cleanup on exit
umount $TARGET
ip netns del $NSNAME
true