zeroconf-ssh-host

#!/bin/sh
#
# A utility to query multicast DNS for a named host or all hosts. This
# is used by zssh to find all hosts in the local domain that advertise
# ssh
#
if [[ "$1" = "-v" ]]; then
    VERBOSE=true
    shift
fi
if [[ -n "$1" ]]; then
    HOST="$1"
else
    HOST=ANYHOST
fi

# conditional printf
function vftrace() {
    if [[ -n "$VERBOSE" ]]; then
        printf "$@"
    fi
}

TIMEOUT1=5
TIMEOUT2=1
function initfile() {
    echo > $1
}


vftrace "Looking up %s\n" "\"${HOST}\""

# We use a couple of temporary files. Open them now so we can simply
# append all results
FILE=/tmp/zeroconf-hosts.txt
initfile $FILE
FILE2=/tmp/zeroconf-addresses.txt
initfile $FILE2

vftrace "Finding ssh advertisers..."
###############################################################################
# the following performs "browse Multicast DNS for hosts advertising
# ssh until $TIMEOUT1 piping results to a file, then quit and clean up"
( dns-sd -B _ssh._tcp . >> $FILE ) & pid=$!
( sleep $TIMEOUT1 && kill -HUP $pid ) 2>/dev/null & watcher=$!
wait $pid 2>/dev/null && pkill -HUP -P $watcher
###############################################################################
vftrace "done\n"

while read TIMESTAMP AR FLAGS IF DOMAIN SERVICE NAME; do
    if [[ "$DOMAIN" = "local." ]]; then
        shopt -s nocasematch

        # For Apple machines, the names Multicast DNS browsing
        # return are not suitable for lookup, we need to "crunch"
        # them the way apple does - replace spaces with hyphens
        # and removing apostrophes.
        # 
        # Note the apostrophe character Apple adds to mac names is
        # "single quote open" which you can type using Option-]
        ADJUSTED_NAME=`echo $NAME | tr ' ' '-' | tr -d "’"`
        vftrace "Compare to %30s ..." "\"${ADJUSTED_NAME}\""

        if [[ ${ADJUSTED_NAME} =~ ${HOST} || $HOST = ANYHOST ]] ; then
	        vftrace " found!\n"
            if [[ $SERVICE == *ssh* ]]; then
		        vftrace "ssh is exported by %s\n" "${NAME}"
				vftrace "ADJUSTED_NAME $ADJUSTED_NAME\n"
	        else
		        vftrace "ssh is NOT exported" ""
		        ADJUSTED_NAME=NONE
            fi

            if [[ ! $ADJUSTED_NAME = NONE ]]; then
		        vftrace "Looking up the IPV4 address of %s in ZeroConf..." "\"${ADJUSTED_NAME}\""
                ###############################################################
                # the following performs "lookup $ADJUSTED_NAME in
                # Multicast until $TIMEOUT2 then quit and clean up"
                ( dns-sd -G v4 "${ADJUSTED_NAME}.local" >> $FILE2 ) & pid=$!
                ( sleep $TIMEOUT2 && kill -HUP $pid ) 2>/dev/null & watcher=$!
                wait $pid 2>/dev/null && pkill -HUP -P $watcher
                ###############################################################
		        vftrace " done\n"
		        if [[ ! ${HOST} = ANYHOST ]]; then
		            break
		        fi
            fi
	    else
	        vftrace " no match\n" ""
        fi
    fi
done < $FILE
cat $FILE2 | grep .local. | sort -k6 -u