Re: Concurrency issues with the iptables userspace program andexitcodes

[Patrick McHardy <kaber@trash.net>]

Jesper Dangaard Brouer wrote:
> I have experienced some concurrency issues with the iptables
> userspace program.  Executing an iptables (write) command while
> another (write command) is running causes a failure of the command.
> Well, this is the expected semantics of a non-blocking call, but the
> issue is how the error situation is reported back.
> 
> The iptables command detects the situation and reports:
>  "iptables: Resource temporarily unavailable"
> 
> With shell exitcode "1".  What annoys me is that the shell exitcode
> is "1", which is also used for "normal" errors.  This means that my
> code/scripts needs to parse output from stderr to distinguish it from
> normal/expected errors.
> 
> I propose that the exitcode of "Resource temporarily unavailable"
> error is changed to something unique for this situation.


Wouldn't it make more sense to just make sure you don't have iptables
commands running concurrently?