[Bug 221948] New: load of bind during boot fails if ip-up starts modify_resolvconf at the same time.

16 Nov 2006

      https://bugzilla.novell.com/show_bug.cgi?id=221948

           Summary: load of bind during boot fails if ip-up starts
                    modify_resolvconf at the same time.
           Product: SUSE Linux 10.1
           Version: Final
          Platform: Other
        OS/Version: SuSE Linux 10.1
            Status: NEW
          Severity: Normal
          Priority: P5 - None
         Component: Basesystem
        AssignedTo: bnc-team-screening@forge.provo.novell.com
        ReportedBy: ulrich@holeschak.de
         QAContact: qa@suse.de

Loading of bind (named) could fail during boot, if ip-up calls
/sbin/modify_resolvconf at the same time (when using a DSL connection and
modification of named.conf is enabled).
modify_resolvconf calls "/etc/init.d/named reload".
If this ist done EXACTLY at the same time when the boot process tries to start
bind the start of bind fails.
Normally this is happening very seldom, but on my machine this did happen very
often.
If have solved this by adding the following lock mechanism to the start section
of /etc/init.d/named:

---------------------------------------------
LOCKFILE="/var/lock/named.pid"

removefiles=()
declare -a  removefiles
function removeonexit()
{
    removefiles[${#removefiles[@]}]="$1"
}

function cleanup()
{
    local file
    for file in "${removefiles[@]}"; do
            rm -f "$file"
    done
}
trap cleanup EXIT

function lockMessage()
{
        tput bold
        echo -en "\nWarning: "
        tput sgr0
        echo -e "$1 "
}

function setlock()
{
    ### Locking mechanism
    LOCKED=0
    while [ $LOCKED -eq 0 ]; do
        set -o noclobber
        echo "$$" 2> /dev/null > $LOCKFILE 
        set +o noclobber
        read PID < $LOCKFILE
        if [ "$PID" != "$$" ]; then
            lockMessage "Another rcnamed with PID $PID found, waiting ..."
            i=0
            while [ -e "$LOCKFILE" -a "$i" -lt 15 ]; do
                sleep 1
                i=$(( i + 2 ))
            done
            if [ -e "$LOCKFILE" ]; then
                lockMessage "Lockfile is still there, ignoring it ..."
                kill -TERM $PID
                sleep 2
                kill -KILL $PID
                rm -f "$LOCKFILE"
            fi
        else
            LOCKED=1
            removeonexit "$LOCKFILE"
        fi
    done
}

setlock
---------------------------------------------

The code is basically taken from SueFirewall2, but is improved a bit.
I contrast to SuseFirewall2 i try to write the lockfile FIRST and then check if
this writing was possible. This prevents race conditions if multiple instances
of this code try to lock a the same time ...

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[Bug 221948] New: load of bind during boot fails if ip-up starts modify_resolvconf at the same time.

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