Re: [expert] Detecting an Active Network Interface
On Tuesday 20 August 2002 11:04 pm, you wrote: > Randy, > > it is written: "thou shalt NOT use a GOTO...ever!" ;) The force fed us > that in assembler and COBOL classes till I thought it was gonna come > outa my ears. and especially with the label: HELL !!! -- /\ Dark> Want to buy your Pack or Services from MandrakeSoft? Go to http://www.mandrakestore.com
Re: [expert] Detecting an Active Network Interface
I use something similiar to this script to check connectivity across my network. With a mysql backend it has become a very useful tool. Only problem is when you try to ping firewalled hosts. If you are on the same lan segment arping can be very useful because it works on the mac layer instead of the tcp/ip layer, can ping through most firewalls unless it is a mac oriented iptables firewall. On Tuesday 20 August 2002 11:06 pm, Mark Weaver wrote: > Randy Kramer wrote: > > kwan, > > > > Thanks! I've got several choices now ;-) > > > > Randy Kramer > > > > [EMAIL PROTECTED] wrote: > >>Here's a script that I use to check connectivity: > >> > >> > >> #!/bin/bash > >> STATUS=`ping -c 2 -q 11.22.33.44 2>/dev/null` > >> CODE=$? > >> > >> if [ $CODE -gt 0 ]; then > >> echo Link is down. > >> else > >> echo Link is up. > >> fi > >> > >> > >>Replace the 11.22.33.44 with a host on the internet. I use the > >>nameserver of the ISP but you can use any reliable address. > >>This script segment is part of a larger one to reboot my DSL modem via > >>X10, but you can modify it for dialup. There are also other ways of > >>dialing on demand such as "diald" that may be more effective. > > Randy, > > The above was the accurate rendition of the correct syntax for the > earlier suggestion. -- Brandon Long [EMAIL PROTECTED] Want to buy your Pack or Services from MandrakeSoft? Go to http://www.mandrakestore.com
Re: [expert] Detecting an Active Network Interface
Todd Lyons wrote:
> Mark Weaver wrote on Tue, Aug 20, 2002 at 11:04:16PM -0400 :
>
>>>So ("thinking on paper"), something like:
>>
>
>
>>> if count <= maxtries (wow, do I forget valid syntax ;-) )
>>> then
>>>wait 30 (??) (give the modem a chance to connect)
>>>goto start
>>> else
>>>issue "Internet connection lost, could not restart"
>>>message (somewhere)
>>> fi
>>
>
>
>>>I'll need to brush up on bash syntax and so forth, and if I'm clever I
>>>might get rid of the goto.
>>
>>it is written: "thou shalt NOT use a GOTO...ever!" ;) The force fed us
>>that in assembler and COBOL classes till I thought it was gonna come
>>outa my ears.
>
>
> [root@fiji /usr/src/linux/kernel]# grep "goto.*\;$" * | wc -l
> 187
>
> Comments? :) Don't tell me Linus doesn't know anything about c now :)
>
> Blue skies... Todd
Todd,
don't know what goto's are like in C, but they suck in mainframe
Assembler and COBOL. looking at older code it gets so bad sometimes
depending on the author that it's easier just to rewrite the stinkin thing.
--
daRmaTTeR
Reg. Linux User #186492
"Stupidity has no moral high ground...it can't see that high!"
Want to buy your Pack or Services from MandrakeSoft?
Go to http://www.mandrakestore.com
Re: [expert] Detecting an Active Network Interface
Todd Lyons wrote:
>
> Mark Weaver wrote on Tue, Aug 20, 2002 at 11:04:16PM -0400 :
> > >So ("thinking on paper"), something like:
>
> > > if count <= maxtries (wow, do I forget valid syntax ;-) )
> > > then
> > > wait 30 (??) (give the modem a chance to connect)
> > > goto start
> > > else
> > > issue "Internet connection lost, could not restart"
> > >message (somewhere)
> > > fi
>
> > >I'll need to brush up on bash syntax and so forth, and if I'm clever I
> > >might get rid of the goto.
> > it is written: "thou shalt NOT use a GOTO...ever!" ;) The force fed us
> > that in assembler and COBOL classes till I thought it was gonna come
> > outa my ears.
>
> [root@fiji /usr/src/linux/kernel]# grep "goto.*\;$" * | wc -l
> 187
>
> Comments? :) Don't tell me Linus doesn't know anything about c now :)
>
201 on my system...
Ya, and who says you can't teach an old dog new tricks, even Linus is
forever into change...
drjung
--
J. Craig Woods
UNIX/NT Network/System Administration
http://www.trismegistus.net/resume.html
Character is built upon the debris of despair --Emerson
Want to buy your Pack or Services from MandrakeSoft?
Go to http://www.mandrakestore.com
Re: [expert] Detecting an Active Network Interface
Mark Weaver wrote on Tue, Aug 20, 2002 at 11:04:16PM -0400 :
> >So ("thinking on paper"), something like:
> > if count <= maxtries (wow, do I forget valid syntax ;-) )
> > then
> > wait 30 (??) (give the modem a chance to connect)
> > goto start
> > else
> > issue "Internet connection lost, could not restart"
> >message (somewhere)
> > fi
> >I'll need to brush up on bash syntax and so forth, and if I'm clever I
> >might get rid of the goto.
> it is written: "thou shalt NOT use a GOTO...ever!" ;) The force fed us
> that in assembler and COBOL classes till I thought it was gonna come
> outa my ears.
[root@fiji /usr/src/linux/kernel]# grep "goto.*\;$" * | wc -l
187
Comments? :) Don't tell me Linus doesn't know anything about c now :)
Blue skies... Todd
--
Todd Lyons -- MandrakeSoft, Inc. http://www.mandrakesoft.com/
UNIX was not designed to stop you from doing stupid things, because
that would also stop you from doing clever things. -- Doug Gwyn
Cooker Version mandrake-release-9.0-0.3mdk Kernel 2.4.19-4mdk
msg57149/pgp0.pgp
Description: PGP signature
Re: [expert] Detecting an Active Network Interface
Randy Kramer wrote: > kwan, > > Thanks! I've got several choices now ;-) > > Randy Kramer > > [EMAIL PROTECTED] wrote: > >>Here's a script that I use to check connectivity: >> >> >> #!/bin/bash >> STATUS=`ping -c 2 -q 11.22.33.44 2>/dev/null` >> CODE=$? >> >> if [ $CODE -gt 0 ]; then >> echo Link is down. >> else >> echo Link is up. >> fi >> >> >>Replace the 11.22.33.44 with a host on the internet. I use the >>nameserver of the ISP but you can use any reliable address. >>This script segment is part of a larger one to reboot my DSL modem via >>X10, but you can modify it for dialup. There are also other ways of >>dialing on demand such as "diald" that may be more effective. Randy, The above was the accurate rendition of the correct syntax for the earlier suggestion. -- daRmaTTeR Reg. Linux User #186492 "Stupidity has no moral high ground...it can't see that high!" Want to buy your Pack or Services from MandrakeSoft? Go to http://www.mandrakestore.com
Re: [expert] Detecting an Active Network Interface
Randy Kramer wrote:
> daRcmaTTeR wrote:
>
>>What if you just did something like this.
>>
>>1) ping ISP...
>> a) if icmp echo request == 'yes'
>>then
>>do the mail thing
>>else
>>run "ifup" command kick mailque
>> fi
>>
>>what-cha think?
>
>
> daRcmaTTeR,
>
> Thanks very much -- it's a good start if not more!
>
> I guess I'll find out for sure soon ;-) , but is that "if icmp echo
> request == 'yes'" pretty close to the right syntax? (I assume it's
> checking for success of the ping.) Hmm, I looked up man icmp and man
> echo -- looks like I'll have to dig a little deeper or do an experiment
> or two.
>
> (Just for the record, I don't need (and can't use) the ifup command
> (effectively) as the dial up modem is on another box (running under
> dos). The ping should "kick" the modem (except that, occasionally, the
> modem hangs up and "locks up" so it won't redial). I'll probably
> arrange the script to ping, check for success, on success kick the
> mailqueue, on failure wait, then retry the ping.)
>
> So ("thinking on paper"), something like:
>
>maxtries = 3 (??)
>count = 0
> start: ping ISP (with parameters to limit to say 4 pings instead of
> continuous)
>count = count + 1
> if icmp echo request == 'yes'
> then
>fetchmail
>sendmail -q
> else
>if count <= maxtries (wow, do I forget valid syntax ;-) )
> then
> wait 30 (??) (give the modem a chance to connect)
> goto start
> else
> issue "Internet connection lost, could not restart"
> message (somewhere)
>fi
> fi
>
> I'll need to brush up on bash syntax and so forth, and if I'm clever I
> might get rid of the goto.
>
> regards,
> Randy Kramer
Randy,
it is written: "thou shalt NOT use a GOTO...ever!" ;) The force fed us
that in assembler and COBOL classes till I thought it was gonna come
outa my ears.
--
daRmaTTeR
Reg. Linux User #186492
"Stupidity has no moral high ground...it can't see that high!"
Want to buy your Pack or Services from MandrakeSoft?
Go to http://www.mandrakestore.com
Re: [expert] Detecting an Active Network Interface
kwan, Thanks! I've got several choices now ;-) Randy Kramer [EMAIL PROTECTED] wrote: > Here's a script that I use to check connectivity: > > > #!/bin/bash > STATUS=`ping -c 2 -q 11.22.33.44 2>/dev/null` > CODE=$? > > if [ $CODE -gt 0 ]; then > echo Link is down. > else > echo Link is up. > fi > > > Replace the 11.22.33.44 with a host on the internet. I use the > nameserver of the ISP but you can use any reliable address. > This script segment is part of a larger one to reboot my DSL modem via > X10, but you can modify it for dialup. There are also other ways of > dialing on demand such as "diald" that may be more effective. Want to buy your Pack or Services from MandrakeSoft? Go to http://www.mandrakestore.com
Re: [expert] Detecting an Active Network Interface
daRcmaTTeR wrote:
> What if you just did something like this.
>
> 1) ping ISP...
> a) if icmp echo request == 'yes'
> then
> do the mail thing
> else
> run "ifup" command kick mailque
>fi
>
> what-cha think?
daRcmaTTeR,
Thanks very much -- it's a good start if not more!
I guess I'll find out for sure soon ;-) , but is that "if icmp echo
request == 'yes'" pretty close to the right syntax? (I assume it's
checking for success of the ping.) Hmm, I looked up man icmp and man
echo -- looks like I'll have to dig a little deeper or do an experiment
or two.
(Just for the record, I don't need (and can't use) the ifup command
(effectively) as the dial up modem is on another box (running under
dos). The ping should "kick" the modem (except that, occasionally, the
modem hangs up and "locks up" so it won't redial). I'll probably
arrange the script to ping, check for success, on success kick the
mailqueue, on failure wait, then retry the ping.)
So ("thinking on paper"), something like:
maxtries = 3 (??)
count = 0
start: ping ISP (with parameters to limit to say 4 pings instead of
continuous)
count = count + 1
if icmp echo request == 'yes'
then
fetchmail
sendmail -q
else
if count <= maxtries (wow, do I forget valid syntax ;-) )
then
wait 30 (??) (give the modem a chance to connect)
goto start
else
issue "Internet connection lost, could not restart"
message (somewhere)
fi
fi
I'll need to brush up on bash syntax and so forth, and if I'm clever I
might get rid of the goto.
regards,
Randy Kramer
Want to buy your Pack or Services from MandrakeSoft?
Go to http://www.mandrakestore.com
Re: [expert] Detecting an Active Network Interface
On Thu, 15 Aug 2002, Randy Kramer wrote: > I'm getting close on my email server (using fetchmail, postfix, > procmail, ipopd (and maybe later imapd) -- in fact, if you see this it > came from my Windows box via the Linux email server. ;-) > > But, I have some bugs to work out yet, and some questions: > > Questions: > > 1. Anybody know a good way to detect that a network link is active? > Background: > > My connection to the Internet is via a dial up on another box (Dos, as a > matter of fact.) I would like to set up a cron job (and script) to do > something like the following: >* Confirm the connection to my ISP is up (ping him, check for > success?) >* If no: wake it up (ping it), and after so many tries, quit and give > a message somewhere (and if it wakes up, proceed to the if yes) >* If yes: > * Run fetchmail to get mail > * Run sendmail -q to kick the queue and send any outgoing mail > (I've set defer_transports=SMTP) > > The reason I want to make sure the link is up before I kick the queue is > so that the "exponential backoff" doesn't go into effect and result in > outgoing messages sitting in the server for long periods of time (or > even getting "failure to deliver" "bounces" from my own server). > > Is that an unrealistic concern? Is there a better way to deal with it? > Here's a script that I use to check connectivity: #!/bin/bash STATUS=`ping -c 2 -q 11.22.33.44 2>/dev/null` CODE=$? if [ $CODE -gt 0 ]; then echo Link is down. else echo Link is up. fi Replace the 11.22.33.44 with a host on the internet. I use the nameserver of the ISP but you can use any reliable address. This script segment is part of a larger one to reboot my DSL modem via X10, but you can modify it for dialup. There are also other ways of dialing on demand such as "diald" that may be more effective. Want to buy your Pack or Services from MandrakeSoft? Go to http://www.mandrakestore.com
Re: [expert] Detecting an Active Network Interface
On Thu, 15 Aug 2002, Randy Kramer wrote: > I'm getting close on my email server (using fetchmail, postfix, > procmail, ipopd (and maybe later imapd) -- in fact, if you see this it > came from my Windows box via the Linux email server. ;-) > > But, I have some bugs to work out yet, and some questions: > > Questions: > > 1. Anybody know a good way to detect that a network link is active? > Background: > > My connection to the Internet is via a dial up on another box (Dos, as a > matter of fact.) I would like to set up a cron job (and script) to do > something like the following: >* Confirm the connection to my ISP is up (ping him, check for > success?) >* If no: wake it up (ping it), and after so many tries, quit and give > a message somewhere (and if it wakes up, proceed to the if yes) >* If yes: > * Run fetchmail to get mail > * Run sendmail -q to kick the queue and send any outgoing mail > (I've set defer_transports=SMTP) > > The reason I want to make sure the link is up before I kick the queue is > so that the "exponential backoff" doesn't go into effect and result in > outgoing messages sitting in the server for long periods of time (or > even getting "failure to deliver" "bounces" from my own server). > > Is that an unrealistic concern? Is there a better way to deal with it? > > Randy Kramer > > Aside: For a while, every time someone mentioned "ifup" it sounded like > just what I needed. I now realize that it is a command (bring the > interface up) rather than a test (if the interface is up, do ...) Hi Randy, What if you just did something like this. 1) ping ISP... a) if icmp echo request == 'yes' then do the mail thing else run "ifup" command kick mailque fi what-cha think? -- daRmaTTeR Reg. Linux User #186492 "Stupidity has no moral high ground...it can't see that high!" Want to buy your Pack or Services from MandrakeSoft? Go to http://www.mandrakestore.com
