tinc - May 2017 - What/why this event happens: Can't write to Linux tun/tap device (tun mode) /dev/net/tun: Input/output error

Hi, All

Due to some routing rotation purpose, I use crontab to add below info:

0 * * * * echo Subnet = 54.169.128.0/17 >> /etc/tinc/myvpn/hosts/aws_sgp
0 * * * * echo Subnet = 54.169.0.0/17 >> /etc/tinc/myvpn/hosts/aws_sgp
1 * * * * /usr/sbin/tincd -n myvpn -k
1 * * * * /usr/sbin/tincd -n myvpn --debug=3

30 * * * * sed -i '/54.169.128.0\/17/d' /etc/tinc/myvpn/hosts/aws_sgp
30 * * * * sed -i '/54.169.0.0\/17/d' /etc/tinc/myvpn/hosts/aws_sgp
31 * * * * /usr/sbin/tincd -n myvpn -k
31 * * * * /usr/sbin/tincd -n myvpn --debug=3


But after it get runs, the tinc log shows everything fine, but some how it get
below error message, is it an accidental error, or is there anything wrong?

Can't write to Linux tun/tap device (tun mode) /dev/net/tun: Input/output
error

Should I change to this in order to avoid the issue?

0 * * * * echo Subnet = 54.169.128.0/17 >> /etc/tinc/myvpn/hosts/aws_sgp
0 * * * * echo Subnet = 54.169.0.0/17 >> /etc/tinc/myvpn/hosts/aws_sgp
1 * * * * /usr/sbin/tincd -n myvpn -k
2 * * * * /usr/sbin/tincd -n myvpn --debug=3

30 * * * * sed -i '/54.169.128.0\/17/d' /etc/tinc/myvpn/hosts/aws_sgp
30 * * * * sed -i '/54.169.0.0\/17/d' /etc/tinc/myvpn/hosts/aws_sgp
31 * * * * /usr/sbin/tincd -n myvpn -k
32 * * * * /usr/sbin/tincd -n myvpn --debug=3

> On 26 May 2017, at 9:30 AM, Bright Zhao <startryst at gmail.com>
wrote:
> 
> Hi, All
> 
> Due to some routing rotation purpose, I use crontab to add below info:
> 
> 0 * * * * echo Subnet = 54.169.128.0/17 >>
/etc/tinc/myvpn/hosts/aws_sgp
> 0 * * * * echo Subnet = 54.169.0.0/17 >>
/etc/tinc/myvpn/hosts/aws_sgp
> 1 * * * * /usr/sbin/tincd -n myvpn -k
> 1 * * * * /usr/sbin/tincd -n myvpn --debug=3
> 
> 30 * * * * sed -i '/54.169.128.0\/17/d'
/etc/tinc/myvpn/hosts/aws_sgp
> 30 * * * * sed -i '/54.169.0.0\/17/d' /etc/tinc/myvpn/hosts/aws_sgp
> 31 * * * * /usr/sbin/tincd -n myvpn -k
> 31 * * * * /usr/sbin/tincd -n myvpn --debug=3
> 
> 
> But after it get runs, the tinc log shows everything fine, but some how it
get below error message, is it an accidental error, or is there anything wrong?
> 
> Can't write to Linux tun/tap device (tun mode) /dev/net/tun:
Input/output error
> 
> 
>

On Fri, May 26, 2017 at 09:30:44AM +0800, Bright Zhao wrote:
> Due to some routing rotation purpose, I use crontab to add below info:
> 
> 0 * * * * echo Subnet = 54.169.128.0/17 >>
/etc/tinc/myvpn/hosts/aws_sgp
> 0 * * * * echo Subnet = 54.169.0.0/17 >>
/etc/tinc/myvpn/hosts/aws_sgp
> 1 * * * * /usr/sbin/tincd -n myvpn -k
> 1 * * * * /usr/sbin/tincd -n myvpn --debug=3
> 
> 30 * * * * sed -i '/54.169.128.0\/17/d'
/etc/tinc/myvpn/hosts/aws_sgp
> 30 * * * * sed -i '/54.169.0.0\/17/d' /etc/tinc/myvpn/hosts/aws_sgp
> 31 * * * * /usr/sbin/tincd -n myvpn -k
> 31 * * * * /usr/sbin/tincd -n myvpn --debug=3
This is not the right way to do it. Cronjobs are being run in parallel.
So if you both stop and start tinc at the same time, there is no
guarantee that it will happen in the right order. The easiest way is to
create two scripts, one that adds the Subnets and the other that removes
them, and the other that adds them.

Another issue is that with tinc 1.0, the -k option sends a TERM signal
to the running tinc daemon, but it might take a little time before it
actually stops. So add a sleep command inbetween, or check for
/var/run/tinc.myvpn.pid to disappear.

-- 
Met vriendelijke groet / with kind regards,
     Guus Sliepen <guus at tinc-vpn.org>
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Hi, Guus

Thanks a lot for your suggestion, actually I did something else as below.

But one question here is if I don’t add "/sbin/ifconfig myvpn 10.0.0.1
netmask 255.255.255.0”, it seems the crontab wouldn’t trigger tinc-up, and then
the ip addr of myvpn wouldn’t be configured, then it will prompt the error of
"Can't write to Linux tun/tap device (tun mode) /dev/net/tun:
Input/output error”

So I have to manually add that ifconfig command, so how can I avoid to do that,
and let the tincd to invoke the tinc-up script?

crontab -e (under root):

0 * * * * /root/add.sh >> /tmp/out.log 2>&1
30 * * * * /root/remove.sh >> /tmp/out.log 2>&1



/root/add.sh:

#!/bin/sh
echo Subnet = 54.169.128.0/17 >> /etc/tinc/myvpn/hosts/aws_sgp
echo Subnet = 54.169.0.0/17 >> /etc/tinc/myvpn/hosts/aws_sgp
/usr/sbin/tincd -n myvpn -k
sleep 1s
/usr/sbin/tincd -n myvpn --debug=3
/sbin/ifconfig myvpn 10.0.0.1 netmask 255.255.255.0


/root/remove.sh:

#!/bin/sh
sed -i '/54.169.128.0\/17/d' /etc/tinc/myvpn/hosts/aws_sgp
sed -i '/54.169.0.0\/17/d' /etc/tinc/myvpn/hosts/aws_sgp
/usr/sbin/tincd -n myvpn -k
sleep 1s
/usr/sbin/tincd -n myvpn --debug=3
/sbin/ifconfig myvpn 10.0.0.1 netmask 255.255.255.0



> On 26 May 2017, at 6:03 PM, Guus Sliepen <guus at tinc-vpn.org>
wrote:
> 
> On Fri, May 26, 2017 at 09:30:44AM +0800, Bright Zhao wrote:
> 
>> Due to some routing rotation purpose, I use crontab to add below info:
>> 
>> 0 * * * * echo Subnet = 54.169.128.0/17 >>
/etc/tinc/myvpn/hosts/aws_sgp
>> 0 * * * * echo Subnet = 54.169.0.0/17 >>
/etc/tinc/myvpn/hosts/aws_sgp
>> 1 * * * * /usr/sbin/tincd -n myvpn -k
>> 1 * * * * /usr/sbin/tincd -n myvpn --debug=3
>> 
>> 30 * * * * sed -i '/54.169.128.0\/17/d'
/etc/tinc/myvpn/hosts/aws_sgp
>> 30 * * * * sed -i '/54.169.0.0\/17/d'
/etc/tinc/myvpn/hosts/aws_sgp
>> 31 * * * * /usr/sbin/tincd -n myvpn -k
>> 31 * * * * /usr/sbin/tincd -n myvpn --debug=3
> 
> This is not the right way to do it. Cronjobs are being run in parallel.
> So if you both stop and start tinc at the same time, there is no
> guarantee that it will happen in the right order. The easiest way is to
> create two scripts, one that adds the Subnets and the other that removes
> them, and the other that adds them.
> 
> Another issue is that with tinc 1.0, the -k option sends a TERM signal
> to the running tinc daemon, but it might take a little time before it
> actually stops. So add a sleep command inbetween, or check for
> /var/run/tinc.myvpn.pid to disappear.
> 
> -- 
> Met vriendelijke groet / with kind regards,
>     Guus Sliepen <guus at tinc-vpn.org>
> _______________________________________________
> tinc mailing list
> tinc at tinc-vpn.org
> https://www.tinc-vpn.org/cgi-bin/mailman/listinfo/tinc
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