diald

[ccb at kukla.tiac.net (Charles C. Bennett, Jr.)]

> Speaking of diald, I'd like to hear how people have elected to handle 
> DNS and SMTP mail delivery/collection?

I've been doing this kind of thing for several years so this
represents several years of slow evolution, initially on Slackware and
then moving to Red Hat.  If I were starting with Red Hat today the
approach may have been different.

I don't use DNS in the house.  There are 10 hosts in my hosts file
which is maintained at a single node.  The other UNIX-like machines
get a copy of the hosts file.  Windows machines get WINS service by
way of SAMBA.  I used the "nodns" version of sendmail.cf.

My ISP has MX records for my machine such that if my machine is down,
one of theirs will take delivery and work at its own pace to eventually
forward the mail to me.

I use pppd.  I have a separate options file for each of several
points-of-presence for my ISP.  Each options file calls out the use of
a separate chat script.  Each options/chatscript pair live in their
own subdirectory of /etc/ppp - so I have /etc/ppp/tiac-arlington,
/etc/ppp/tiac-cambridge, etc.

One of the options in my options file is "idle 1200" - turn off the
link after 20 minutes of inactivity.  There is no inactivity timer
on my ISP's side.

I have tweaked the mode on pppd to 4750, owner root, group uucp.  All
of the chat and options file are mode 750 or 640, owner root, group
uucp.  I can grant any of my users access to pppd by putting them in
group uucp.  If I were setting this up today, I might choose the
pppusers group provided on recent RHL distributions.

Anyone that wants to connect to any of my ISP's POPs can do it by
typing /usr/sbin/pppd -d ttyS2 234000 file /etc/ppp/<POPNAME>/options.
In practice I wrote a convenience script (/usr/local/bin/ppp) which
takes a POP name as a parameter and attempts to connect to that POP
and waits to see ppp0 come up before printing a success or failure
message.

For mail handling, I have a second script called "mailcheck".  It runs
out of cron several times a day.  It attempts to connect to a
preferred POP.  If it succeeds it runs sendmail -q and leaves the line
up to catch any mail inbound from my ISP.  Yes this is passive and
nondeterministic, but it works.  If mailcheck fails to get a
connection, it uses "at" to reschedule itself in another 5 minutes.

So in practice, everything is smooth.  Mailcheck runs at regular intervals
to drain the mail from the ISP.  If I create a mail message that's got
to get out NOW!, I can run mailcheck manually.  If one of us wants to
get online we can type "ppp tiac" and my ppp script dials my default
POP and exits only when it's sure that I have a connection.

Get a close look at fetchmail before getting all wound up in this kind
of hackery.

Scripts attached.

Hope this Helps,
ccb


-- [ /usr/local/bin/ppp ] -------- 8< --------------
#!/bin/bash -p
#
#  /usr/sbin/ppp - dial a host
#


:  -Main
#

Main()
{
  case "$1" in
  -k)
    kill `cat $_PIDFILE`
    exit $?
    ;;
  "")  1>&2 echo "Usage: $0 [-k] system"
    exit 1
    ;;
  esac

  SYSTEM=$1

  $_PPPD -d ttyS2 230400 file /etc/ppp/$SYSTEM/options

    for K in 1 2 3 4 5 6
    do
	for K in 1 2 3 4 5
	do
	    sleep 2
	    [ -f /etc/ppp/ppp0 ] && {
		echo "$SYSTEM is up"
		return 0
	    }
	done
    done
    echo Timed out waiting for $SYSTEM
    return 1
}

typeset -r _PIDFILE=/var/run/ppp0.pid
typeset -r _PPPDIR=/usr/local/lib/ppp
typeset -r _PPPD=/usr/sbin/pppd
typeset    _X=

case "$-" in
*x*)  # debug...
  _X=-px
  ;;
esac

[ "$CHECK_SYNTAX" ] || Main "$@"  # -- NO CODE BELOW THIS LINE --



-- [ /usr/local/bin/mailcheck ] --------------
#!/bin/sh
#

IsOnLine()
{
  [ -f $_LOCKFILE ]
}

Main()
{
  case "$1" in
  on)
    echo "Mail checking enabled"
    echo "Mail checking enabled" |
    Mail -s "mailcheck notification" kukla-users
    [ -f $_NOMAIL ] || return 0
    set -- $(wc -l $_NOMAIL)
    rm -f $_NOMAIL
    [ $1 -eq 0 ] && exit 0
    S=s
    [ $1 -eq 1 ] && S=
    echo "$1 mail check$S missed, launching one immediately"
    ;;

  off)
    > $_NOMAIL
    echo "Mail checking disabled"
    echo "Mail checking disabled" |
    Mail -s "mailcheck notification" kukla-users
    IsOnLine && {
      echo "currently online, use ppp -k as root to kill"
    }
    exit 0
    ;;

  -q)
    if IsOnLine
    then
      echo "Online, use ppp -k as root to kill"
    else
      echo "Offline"
    fi
    exit 0
    ;;
  -f)
    FORCE=1
    ;;
esac

  [ -f $_NOMAIL -a ! "$FORCE" ] && {
    echo "Mail scan deferred"
    echo >> $_NOMAIL
    exit 0
  }
  IsOnLine && {
    echo "Already online"
    exit 0
  }
  /usr/local/bin/ppp tiac ||
  {
    echo "connect to tiac failed"
    echo "scheduling retry for T+5 minutes"
    echo "/usr/local/bin/mailcheck" | at now + 5 minutes
    exit 1
  }

  /usr/sbin/sendmail -q
}

_NOMAIL=/var/local/mailcheck/disable
_LOCKFILE=/var/run/ppp0.pid

[ "$CHECK_SYNTAX" ] || Main "$@"	# -- NO CODE BELOW THIS LINE --

-
Subcription/unsubscription/info requests: send e-mail with
"subscribe", "unsubscribe", or "info" on the first line of the
message body to discuss-request at blu.org (Subject line is ignored).