[Pkg-utopia-maintainers] Bug#627343: Improved Workaround for DHCP lease NTP servers with NetworkManager

[ste-fan]

​​​Hi there,

since this issue really bugged me as well (why generate tons of public NTP
traffic if you have a server in-house?! [1]) I proudly present my
/etc/default/ntpdate:

https://gist.github.com/ste-fan/7b9b5bcf6656f59c280f   [2]

I tried to clean Jan's "one"-liner up a bit. Basically it still does the
same
wonderful thing, but here's a quick changelog:

* updated DHCP lease folder to /var/lib/NetworkManager
  + of course there we must consider *.lease files only

* rewrote the whole method as a function (hopefully easier to read)

* reduced the use of redirection and temporary variables using slightly more
  complex sed scripts and utilizing more of find's capabilites

* added debug output that responds to ntpdate's -d option and will also be
  logged to syslog if the -s option is given (which is provided by
  /etc/network/if-up.d/ntpdate)

* nevertheless there is no namespace pollution, thanks to
  + exclusively local function variables
  + unsetting function definitions after execution

* the upper (default) config part can be left as is!
  + if NTP servers are found in the latest lease, NTPSERVERS will get
updated
  + otherwise it won't be touched (keeping the above specified servers)
  + NTPDATE_USE_NTP_CONF can be left "yes" if you don't have any
ntp(d).conf*
    files that could be read by ntpdate-debian
    (namely: /var/lib/ntp/ntp.conf.dhcp /etc/ntp.conf
/etc/openntpd/ntpd.conf)

Well, now I hope someone finds this useful!

Cheers
~ste-fan



[1] OK, you could configure the in-house NTP server statically on each
client.
    But ntpdate was made for PCs that do not run 24/7 and even Laptops that
    move around, right? So we need a dynamic approach with fallback NTP
servers
    that are used if the current DHCP server does not supply NTP server
    information.


[2]

# The settings in this file are used by the program ntpdate-debian, but not
# by the upstream program ntpdate.

# Set to "yes" to take the server list from /etc/ntp.conf, from package ntp,
# so you only have to keep it in one place.
NTPDATE_USE_NTP_CONF=yes

# List of NTP servers to use  (Separate multiple servers with spaces.)
# Not used if NTPDATE_USE_NTP_CONF is yes.
NTPSERVERS="ntp.ubuntu.com"

# Additional options to pass to ntpdate
NTPOPTIONS=""

# extract NTP servers from latest DHCP lease (if option was given by server)
get_debug_opts() {
    local opt
    debug_opt=false
    debug_syslog=false
    for opt in "$@" $( xargs -0 < /proc/$$/cmdline ); do
        case "$opt" in
            -d) debug_opt=true ;;
            -s) debug_syslog=true ;;
        esac
    done
    return 0
}

dhcp_ntp_debug_msg() {
    if $debug_opt; then
        echo "$(LC_ALL=C date +'%_d %b %H:%M:%S')" "ntpdate[$$]:" \
             '(DCHP)' "$@"
        if $debug_syslog; then
            logger --tag "ntpdate[$$]" '(DCHP)' "$@"
        fi
    fi
    return 0
}

get_dhcp_ntp_servers() {
    local debug_opt debug_syslog leasefiledir recentleasefile ntpservers

    leasefiledir=/var/lib/NetworkManager

    # check whether we are in debug mode and logging to syslog
    get_debug_opts $NTPOPTIONS

    # get most recent lease file that is not older than 1 minute
    recentleasefile=$( find $leasefiledir ! -type d -iname '*.lease' \
                            ! -mmin +1 -printf '%T@ %p\n' 2>/dev/null \
                         | sort -k 1nr | sed 's/^\S\+ //; 1q' )

    if [ -n "$recentleasefile" ]; then
        dhcp_ntp_debug_msg 'Found a recent lease file:' \
                           $( basename $recentleasefile )
        # extract NTP servers, if any  (check only latest lease in file)
        ntpservers=$( sed '1,/lease\s\+{/d
                           /option ntp-servers/!d
                           s/^.*ntp-servers\s\+\(.\+\);$/\1/; s/,/ /g' \
                        $recentleasefile )
        if [ -n "$ntpservers" ]; then
            dhcp_ntp_debug_msg 'Found NTP server(s) in latest lease:' \
                               $ntpservers
            NTPSERVERS="$ntpservers"
        else
            dhcp_ntp_debug_msg 'Latest lease does not contain any NTP
servers.'
        fi
    else
        dhcp_ntp_debug_msg 'There is no recent lease file.'
    fi

    return 0
}

get_dhcp_ntp_servers

unset get_debug_opts dhcp_ntp_debug_msg get_dhcp_ntp_servers
​
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.alioth.debian.org/pipermail/pkg-utopia-maintainers/attachments/20141007/feb7fe90/attachment.html>