Concurrency issues with the iptables userspace program andexitcodes
Jesper Dangaard Brouer
jdb at comx.dk
Thu Jun 1 11:15:49 CEST 2006
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
I propose that the exitcode of "Resource temporarily unavailable"
error is changed to something unique for this situation.
Med venlig hilsen / Best regards
ComX Networks A/S
Linux Network developer
Cand. Scient Datalog / MSc.
Author of http://adsl-optimizer.dk
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