Re: checking ssh tunnels: best practices?

[Marcel Gschwandl <tautau@gmx.ch>]

Sorry, I replyed to the wrong topic.

MfG
Marcel
On Thu, 2003-05-22 at 06:32, Marcel Gschwandl wrote:
> Hallo,
> 
> I use an ATI Mobility M7 and had nearly the same problem. After the
> upgrade to XF4.2.1 I also had to disable the Option "UseFBDev" "true" in
> the device section. After that everything worked fine.
> 
> Greetings
> Marcel
> 
> On Thu, 2003-05-22 at 06:02, Tony Godshall wrote:
> > Hi, all.
> > 
> > I've got a laptop (yes, I'm on this list, duh).  I take it
> > to a jobsite with me, I take it home, I take it to the
> > office.  Some places I can connect to the mailserver
> > directly, but at other places I have to ssh through a leased
> > line back to the office.
> > 
> > I've got ssh set up with tunnels for one smtp port,
> > three POP ports, a VNC session, etc.  I set up exim 
> > to send its mail through the tunnel smtp, and set up 
> > fetchmail to fetch through the tunnel.
> > 
> > The problem is that sometimes these programs don't work
> > right and hassle ensues if I start them up without starting
> > up my ssh session first, or if the ssh session has dropped
> > someplace along the way.  A lot of the time I'm working
> > locally, so I might not notice that the tunnel went away,
> > and exim will tell me that the message couldn't be
> > delivered, etc.
> > 
> > The hack I've done is to make a little script,
> > port_is_connected, so I can have my mutt-starter script
> > abort with a line like this:
> > 
> >     port_is_connected $MAIL1SMTP localhost || exit 1
> > 
> > ...or less tersely...
> > 
> >     if ! port_is_connected $MAIL1SMTP localhost 
> >     then
> >       echo "check the ssh tunnel, dammit!"
> >       exit 1
> >     fi
> > 
> > Does this approach make sense, overall?
> > 
> > It took me a while to figure out how to do port_is_connected, but 
> > eventually I located nmap.  This does the job pretty well
> > and is pretty fast:
> > 
> >     nmap -p $MAIL1SMTP localhost | grep -q open
> > 
> > I had been using something like this...
> > 
> >     ps -ef | grep "ssh.*$MAIL1SMTP"
> > 
> > ... but I don't like that much for a variety of reasons.
> > 
> > So this is what I came up with for port_is_connected:
> > 
> >     #!/bin/sh
> >     
> >     port=""
> >     host=""
> >     err=""
> >     
> >     while [ -n "$1" ]
> >     do
> >     
> >       case "$1" in
> >     
> >       -*) 
> >         err="$err\nunexpected opt"
> >         ;;
> >     
> >       *)
> >         if [ -z "$port" ]
> >         then
> >           case "$1" in
> >           [0-9]*)
> >             port="$1"
> >             ;;
> >           *)
> >             err="$err\nhuh? [$1]"
> >             ;;
> >           esac
> >         elif [ -z "$host" ]
> >         then
> >           host="$1"
> >         else
> >           err="$err\ntoo many args [$1]"
> >         fi
> >         ;;
> >     
> >       esac
> >     
> >       shift
> >     
> >     done
> >     
> >     if [ -n "$err" ]; then printf "ERR$err\n"; exit 2; fi
> >     
> >     if [ -z "$port" ]; then err="$err\nno port specified"; fi
> >     
> >     if [ -n "$err" ]; then printf "ERR$err\n"; exit 2; fi
> >     
> >     if [ -z "$host" ]; then 
> >       host=localhost
> >       printf "no host given; assuming host[$host]\n" >&2
> >     fi
> >     
> >     if nmap -p $port $host | grep -q open 
> >     then
> >       printf "port $host:$port is open: exit 0\n" >&2
> >       exit 0
> >     else
> >       printf "port $host:$port is closed: exit 1\n" >&2
> >       exit 1
> >     fi
> >     
> > So, comments please.  Is this a good way to do it, or am I
> > missing a better, obvious way?  Comments on style are also
> > welcome.  
> > 
> > Tony 
> >  
-- 
Marcel Gschwandl <tautau@gmx.ch>

The day Microsoft invents something that doesn't suck
is the day they start making vacuum cleaners. -- Ernst Jan Plugge