#!/bin/sh
# this is a small automounter (and unmounter) for usb and other 
# removable devices for the kernel hotplug framework with busybox/mdev

# Author:              Alexander Zangerl (az)
# Licence:             GPL version 1 or version 2
# $Id: block.agent,v 1.23 2016/07/16 11:49:50 az Exp $

# this agent mounts at /media/LABEL, /media/UUID or /media/devname in 
# this order, if the config file says "do mount" for this fs label/uuid.
# the agent ignores non-removable devices.

# it removes the mount point dir on device remove and unmounts the defice, 
# if it was still mounted.
# the unmount/remove logic uses a statefile in /var/run to keep track
# of what is "ours" and should be cleaned up on demand.

# requirements: busybox and mdev, pmount, and either
# a mounted /usr (for pinky and pmount) or the mounted devices will 
# belong to root.

# terminal on stderr -> log to that and to syslog, otherwise syslog only
ME=$(busybox basename $0)"[$$]"
[ -t 2 ] && LOGARGS=-s
mesg () 
{
    busybox logger $LOGARGS -t "$ME" "$@"
}

debug_mesg () 
{
    [ -z "$DEBUG" ] && return
    mesg "$@"
}

[ -z "$BASE" ] && BASE=/media
STATEF=/var/run/block.agent.state
OPTIONFILE="/etc/mdev/block.settings"
cd /tmp

# finds a mountpoint for $1, the realdev
# sets $MOUNT to the full mount command, or empty if not to be mounted
# also sets $TARGET
findmount ()
{
    local RD=$1
    MOUNT=""

    debug_mesg "testing $RD for filesystem"
    eval `/sbin/blkid -o udev $RD`

    if [ "$?" != 0  -o -z "$ID_FS_TYPE" ]; then
	debug_mesg "$RD has no detectable filesystem"
	return
    fi

    if [ -n "$ID_FS_LABEL" ] ; then
	ID_FS_LABEL=$( echo "$ID_FS_LABEL" | tr '[A-Z]' '[a-z]' )
	TARGET=$BASE/$ID_FS_LABEL
	PREF=$ID_FS_LABEL
    elif [ -n "$ID_FS_UUID" ]; then
	TARGET=$BASE/$ID_FS_UUID
	PREF=$ID_FS_UUID
    else
	TARGET=$BASE/$(busybox basename $RD)
	PREF=$(busybox basename $RD)
    fi

    local MOUNTOPT="-"
    # determine where, how and if to mount this thing
    while read U L T O ; do
	ISCOMMENT=$(printf %.1s "$U")
	[ "$ISCOMMENT" = "#" -o -z "$U" ] && continue;
	debug_mesg "testing  $ID_FS_UUID $ID_FS_LABEL $ID_FS_TYPE against $U $L $T"

	if [ \( "$U" = "$ID_FS_UUID" -o "$U" = "*" \) \
	    -a \( "$L" = "$ID_FS_LABEL" -o "$L" = "*" \) \
	    -a \( "$T" = "$ID_FS_TYPE" -o "$T" = "*" \) ] ; then
	    debug_mesg "found entry $U $L $T $O for $RD";
	    MOUNTOPT="$O";
	    break;
	fi
    done < $OPTIONFILE

    if [ "$MOUNTOPT" = "-" ] ; then
	mesg "$RD: no automounting"
	return
    else
	mesg "$RD: $TARGET options $MOUNTOPT"
	if [ "$MOUNTOPT" = "+" ]; then
	    # pmount and use first logged in user
	    # x11 user first, console as fallback
	    MAINUSER=`pinky -fw 2>/dev/null| awk '{ if ($2 ~ /^\??:0/ || $(NF) ~ /^\??:0/ ) { print $1; exit; } }'`
	    if [ -z "$MAINUSER" ]; then
		MAINUSER=`pinky -fw 2>/dev/null|fgrep '*'|head -1 | cut -f 1 -d " "`
	    fi
	    if [ -n "$MAINUSER" ]; then
		MOUNT="su -c 'pmount $RD \"$PREF\"'  $MAINUSER"
	    else
		MOUNT="pmount $RD \"$PREF\""
	    fi
	else
	    if [ -n "$MOUNTOPT" ] ; then
		MOUNT="mount -o $MOUNTOPT $RD $TARGET"
	    else
		MOUNT="mount $RD $TARGET"
	    fi
	fi
    fi
    return
}

# what we get: 
# ACTION=add HOME=/ SEQNUM=2223 PWD=/dev 
# DEVNAME=sdd1 MAJOR=8 MINOR=49 DEVTYPE=partition
# that's from mdev: MDEV=sdd1 SUBSYSTEM=block
# DEVPATH=/devices/pci0000:00/0000:00:1d.7/usb1/1-7/1-7:1.0/host3/target3:0:0/3:0:0:0/block/sdd/sdd1

REALDEV=/dev/$MDEV
if [ "$ACTION" = "add" -o "$ACTION" = "change" ]; then
    REMF="/sys/$DEVPATH/removable"
    [ -f "$REMF" ] || REMF="/sys/$DEVPATH/../removable"

    if [ "`cat $REMF`" != 1 ]; then
	debug_mesg "device $REALDEV is not removable."
	exit 0
    fi

		# prime the cache
		/sbin/blkid >/dev/null 2>&1
		
    # sets $MOUNT, $TARGET
    findmount $REALDEV
    if [ -z "$MOUNT" ] ; then
	exit 0;
    else
	mesg "trying automount of $REALDEV at $TARGET"
	[ ! -d "$TARGET" ] && mkdir $TARGET
	debug_mesg "$MOUNT"
	eval $MOUNT		# necessary if we need to su and pmount
	RES=$?
	if [ $RES != 0 ] ; then
	    mesg "mounting $REALDEV failed with $RES"
	    exit 1
	fi
	echo $REALDEV $TARGET >> $STATEF
    fi
elif [ "$ACTION" = "remove" ] ; then
    MPT=$(egrep "^$REALDEV /" $STATEF|cut -f 2 -d " ")

    # ours? unmount if mounted, remove dir
    if [ -n "$MPT" ]; then

	egrep -v "^$REALDEV $MPT" $STATEF > $STATEF.x
	mv $STATEF.x $STATEF

	LOC=$(egrep "^$REALDEV $MPT" /proc/mounts)
	if [ -n "$LOC" ] ; then
	    mesg "attempting late unmount of $REALDEV from $MPT"
	    umount -f $REALDEV
	    RES=$?
	    if [ $RES != 0 ] ; then
		mesg "unmounting $REALDEV failed with $RES"
	    fi
	fi
	mesg "cleaning up mountpoint dir $MPT for $REALDEV"
	rmdir $MPT
    fi
else
    debug_mesg "ignoring action $ACTION with $MDEV"
    exit 1
fi
exit 0