Fail2Ban

The fix with adding random sleeps is a workaround, but not the right long
term fix. It's a design flaw to have the action{start,stop} executing in
parallel IMO. Either they should be serialized, or a locking mechanism put
in place to ensure that multiline commands are treated atomicly.

For more details see http://bugs.debian.org/554162

This patch unfortunately breaks commands with multiline string arguments in
them (e.g. sending an email notifications).
Original problem is with concurrent execution of iptables commands by
separate threads (there is 1 thread per jail in fail2ban) upon jail
initiation. Possible solution is to sleep some random amount of time before
executing the command. It could be accomplished with adding smth like

sleep ${RANDOM:0:1}.${RANDOM: -1:1}

to the beginning of actionstart/actionstop if you use bash for your shell

Hi idl0r, thanks for your patch - I nearly got crazy with this bug ...