Another app is currently holding
the xtables lock. Perhaps you
want to use the -w option?
iptables command needs a
communication between user and
It need a lock to make sure the
iptables will exit if it can’t acquire the
lock by default.
Use the –w option to wait the lock.
The iptables system includes the
user-space tool and kernel-space
We focus on how user-space tools
iptables need a file lock to protect the
iptables use the library (libiptc) to
control the rules via system call.
You can extend the iptables by
implement the extension
For each iptables extension module,
you should both user-space and
Please make sure the kernel version
○ Implement the arguments and store the
data into pre-defined structure.
○ Implement the match function