Messages in this thread | | | Date | Mon, 12 Mar 2012 22:09:20 +0100 | From | Helge Deller <> | Subject | Re: [PATCH] enhance usability of /proc/sys/net/ipv4/ip_local_reserved_ports |
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On 03/12/2012 04:42 AM, Cong Wang wrote: > On Sun, 2012-03-11 at 00:36 +0100, Helge Deller wrote: >> When writing to the ip_local_reserved_ports proc file it will currently clear >> all previously reserved ports and update the current list with the one given >> in the input. >> >> This behaviour makes it's usage quite hard, for example: >> a) The generic proc filesystem limitation of only handle up to PAGE_SIZE-1 >> characters at maximum may not be sufficient to provide all your wished-to- >> be-reserved ports at once. > > Yes, this should be extended IMHO.
Yes, known problem and not easy to fix.
>> b) There is no easy way to disable specific given ports, you always need to >> give the full port list at once. This makes shell scripting hard, since >> you need to parse everything yourself. >> c) There is no easy way to just add specific ports or port ranges. Again, >> this would be useful for shell scripts. >> > > These could be calculated in user-space, although it maybe not as easy > as you want.
Right.
>> The following patch solves this problem by simply extending the parser >> in proc_do_large_bitmap() to accept the keywords "add" and "release" in front >> of given ports or port ranges and to either add or drop the given ports >> from the already existing list. > > This looks a little odd, because we do "magic" things with a sysctl > file, which is supposed to be plain text file. Do we have existing > examples?
I don't think the networking sysctl has such tunables. Overall, ip_local_reserved_ports is the only user of the large_bitmap function and as such you can't compare the input/output of this file with other sysctl files which operate on a limited number of integers/booleans/strings only. Furthermore my patch does not remove the "plain text" behaviour of this file. You can still echo plain ports or port lists into it and a "cat" gives you the same output as before. It just extends the interface to add/remove ports more easily if you want.
One somewhat comparable proc file which comes to my mind in this regard is /proc/scsi/scsi where you can echo commands like "scsi report-devs 1" and which then reacts. A user of this interface is e.g. the known rescan-scsi-bus shell script: http://www.garloff.de/kurt/linux/rescan-scsi-bus.sh-1.25
> BTW, as David mentioned, please Cc netdev next time.
Sure. I'll send an updated patch tomorrow and will CC netdev.
Thanks, Helge
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