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Pau Escrich, 24-10-2013 15:13

Mdns¶

This is an example of bmx6 SMS plugin utilization. It is a distributed DNS system where every node publish the domains it is managing.
The current implementation is done for working in OpenWRT with the Dnsmasq daemon.

Usage:

/etc/init.d/mdns start
/etc/init.d/mdns start
/etc/init.d/mdns reload

Files:

/etc/mdns/public contains the list of domains we wanto to announce in the network
/etc/mdns/hosts contains a list of "IP -> domain" which have been obtained from the network (dnsmasq looks on it)


#!/bin/sh
#    Copyright (C) 2013 Pau Escrich <p4u@dabax.net>
#
#    This program is free software; you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation; either version 2 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License along
#    with this program; if not, write to the Free Software Foundation, Inc.,
#    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
#
#    The full GNU General Public License is included in this distribution in
#    the file called "COPYING".

# Configuration variables                                     
MDNS_DIR="/etc/mdns"                                                
HOSTF="$MDNS_DIR/hosts"                                            
MY_DOMAINS="$MDNS_DIR/public"                                     
DOMAINS4="qmp" 
DOMAINS6="qm6" 
SMSF="/var/run/bmx6/sms/sendSms/mdns"                                       
SMSR="/var/run/bmx6/sms/rcvdSms"                                            
DNSMASQ="/etc/dnsmasq.conf"                                     
DNSMASQ_PID="/var/run/dnsmasq.pid" 

# Optional
IPV4="" 
IPV6="" 

start() {
    if ! cat /etc/crontabs/root | grep mdns > /dev/null; then
        echo "/10 * * * * /etc/init.d/mdns reload > /tmp/log/mdns.log" >> /etc/crontabs/root
        /etc/init.d/cron enable
        /etc/init.d/cron start
    fi
    /etc/init.d/mdns reload
    }

stop() {
    sed -i -e '/.*\/etc\/init\.d\/mdns reload > \/tmp\/log\/mdns\.log$/d' /etc/crontabs/root
    /etc/init.d/cron restart
    }

reload() {
    init
    publish_my_domains
    get_domains
    finish    
}

refresh() { 
    reload
}

# Code

error() {
    echo "ERROR: $@" 
    exit 1
}

log() {
    echo -e "-> $@" 
}

init() {
    log "preparing bmx6" 
    bmx6 -c --syncSms mdns
    [ $? -ne 0 ] && error "cannot configure bmx6 daemon" 

    cat $DNSMASQ | egrep "^addn-hosts=$HOSTF" -q || {
        log "adding addn-host entry to dnsmasq config file" 
        echo "addn-hosts=$HOSTF" >> $DNSMASQ
        log "restarting dnsmasq daemon" 
        /etc/init.d/dnsmasq restart
    }
    ps | grep dnsmasq -q || error "dnsmasq not running" 

    log "cleaning files" 
    [ -f $SMSF ] && rm -f $SMSF
    touch $SMSF

    [ -f $HOSTF ] && rm -f $HOSTF
    touch $HOSTF    

    [ ! -d $MDNS_DIR ] && mkdir -p $MDNS_DIR
    touch $MY_DOMAINS
}

check_domain() {
        local v="$1" 
        local d="$2" 
        local valid=1
        local domains="" 

        [ $v == "4" ] && domains="$DOMAINS4" 
        [ $v == "6" ] && domains="$DOMAINS6" 
        [ $v == "all" ] && domains="$DOMAINS4 $DOMAINS6" 

        for D in $domains; do
            echo "$d" | egrep "\.$D"$ -q && valid=0 && break
        done 

        return $valid
}

get_my_domains() {
    local v=${1:-4}
    local my_domains="" 
    local domains="" 
    local d

    for d in $(cat $MY_DOMAINS); do
        check_domain $v $d && my_domains="$d $my_domains" 
    done

    [ "$v" == "4" ] && domains="$DOMAINS4" 
    [ "$v" == "6" ] && domains="$DOMAINS6" 

    for d in $domains; do
        my_domains="$(cat /proc/sys/kernel/hostname).$d $my_domains" 
    done

    echo $my_domains
}

get_my_ip4() {
    [ -z $IPV4 ] && \
    bmx6 -cp | grep tun4Address | awk '{print $2}' | awk -F / '{print $1}' || \
    echo "$IPV4" 
}

get_my_ip6() {
    [ -z $IPV4 ] && \
    bmx6 -cp | grep tun6Address | awk '{print $2}' | awk -F / '{print $1}' || \
    echo "$IPV6" 
}

publish_my_domains() {
    local d domains

    local ip4="$(get_my_ip4)" 
    local ip6="$(get_my_ip6)" 

    [ -z "$ip4$ip6" ] && error "cannot get ip address" 

    [ -n "$ip4" ] && {
        domains="$(get_my_domains 4)" 
        log "publishing own IPv4 domains: $domains" 
        echo "$ip4 $domains" >> $SMSF
        echo "$ip4 $domains" >> $HOSTF
    }

    [ -n "$ip6" ] && {
        domains="$(get_my_domains 6)" 
        log "publishing own IPv6 domains: $domains" 
        echo "$ip6 $domains" >> $SMSF
        echo "$ip6 $domains" >> $HOSTF
    }
}

get_domains() {
    local f d domline ip line n i

    ls $SMSR/*:mdns 2>/dev/null >/dev/null && {

      # for each received file    
      for f in $SMSR/*:mdns; do
        n=$(cat $f | wc -l)

        # for each line inside the file
        for i in $(seq $n); do
            line=$(cat $f | awk "NR==$i")

            ip="$(echo $line | awk '{print $1}')" 
            [ -z $ip ] && continue

            domains="" 
            # for each domain (first is IP)
            for d in $(echo "$line" | awk '{$1=""; print $0}'); do
                check_domain all $d && domains="$d $domains" 
            done

            [ -n "$domains" ] && echo "$ip $domains" >> $HOSTF
            log "added remote domains $domains= $ip" 
      done
  done 

      } || log "not published domains found in the network" 
}

finish() {
    kill -SIGHUP $(cat $DNSMASQ_PID)
}

$@

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