*** This bug is a duplicate of bug 1204579 ***
https://bugs.launchpad.net/bugs/1204579
Thank you for reporting a bug. I believe this is a duplicate of bug
#1204579.
** This bug has been marked a duplicate of bug 1204579
ufw doesn't support concurrent updates
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https://bugs.launchpad.net/bugs/1584293
Title:
if two or more ufw commands are run at exactly the same time, ufw can
break iptables
Status in ufw package in Ubuntu:
New
Bug description:
I was playing around with a script to allow a firewall entry in ufw,
but only for a certain amount of time. The way I was doing this is by
creating the rule and then automatically create an at job to delete it
and the user could select time in minutes
Everything is beautiful and wonderful with the script except for when
you schedule two ufw delete or more at the same time. If I do this
only one of them deletes, even worse, my iptables "broke" and I could
not delete rules even by resetting ufw, I kept getting this error:
ERROR: initcaps
[Errno 2] ip6tables: Chain already exists.
So I had to reset the iptables
Here is the code that creates the job in case it is any help to
replicate
at -f <(echo "ufw delete allow from $1 to any port $2") now + $3
minutes
While I don't expect people to be creating jobs left and right at the
exact same time, I have to account for that possibility and that it
doesn't break the firewall when it happens.
I believe this bug has been around for more than a year or so, as
stated here:
https://bugs.launchpad.net/ubuntu/+source/ufw/+bug/1377600
and here:
http://blog.cloud66.com/ufw-shenanigans/
I don't understand why this wasn't fixed yet, it seems like quite a
serious issue, you never know when two sysadmins may run the same
command at the same time, and if you have a lot of rules applied, the
last thing you want is corrupted iptables.
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