Re: [9front] [PITCH] ip/null

[Jacob Moody <moody@posixcafe.org>]

Indeed, but right now ipmux is the only tool we have for doing any
filtering more fine grained then routing tables as far as I know.

I would like our own pf-like but that would require going back to
the drawing board.

On 12/11/23 13:05, hiro wrote:
> it would be good if it wouldn't need to get all the way to userland
> before being dropped.
> 
> On 12/11/23, Jacob Moody <moody@posixcafe.org> wrote:
>> This as obsoleted by cinap's aux/dial(1).
>> It functionally works the same here except you would
>> need an explicit direction to /dev/null.
>>
>> ie.
>>
>> aux/dial
>> 'ipmux!ifc=my.external.ip;dst=192.168.0.0&255.255.0.0|10.0.0.0&255.0.0.0' >
>> /dev/null
>>
>> On 12/11/23 12:54, unobe@cpan.org wrote:
>>> FWIW, I haven't seen anyone else comment on this, but I like it.
>>>
>>> Quoth Jacob Moody <moody@mail.posixcafe.org>:
>>>> As I play around more with 9front as my router, I found myself reaching
>>>> for some
>>>> kind of 'firewall'. I find that we already have a pretty good interface
>>>> in the kernel
>>>> in the form of ipmux. But there isn't too many ways of making use of it
>>>> as is. I hacked up
>>>> something quick to just drop packets matching a filter on to the floor.
>>>> If others find it
>>>> useful I can make up a man page and present again with a bit more
>>>> polish.
>>>>
>>>> Some examples:
>>>> # Drop inbound private range
>>>> ip/null
>>>> 'ifc=my.external.ip;dst=192.168.0.0&255.255.0.0|10.0.0.0&255.0.0.0'
>>>>
>>>> # google verboden
>>>> ip/null 'ifc=my.internal.ip;dst=8.8.8.8;src=192.168.0.0&255.255.0.0'
>>>>
>>>> thanks,
>>>> moody
>>>>
>>>> --- /dev/null
>>>> +++ b//sys/src/cmd/ip/null.c
>>>> @@ -1,0 +1,36 @@
>>>> +#include <u.h>
>>>> +#include <libc.h>
>>>> +
>>>> +void
>>>> +usage(void)
>>>> +{
>>>> +	fprint(2, "usage: %s filter\n", argv0);
>>>> +	exits("usage");
>>>> +}
>>>> +
>>>> +void
>>>> +main(int argc, char **argv)
>>>> +{
>>>> +	char buf[64 * 1024];
>>>> +	int fd;
>>>> +
>>>> +	ARGBEGIN{
>>>> +	default:
>>>> +		usage();
>>>> +		break;
>>>> +	}ARGEND
>>>> +	if(argc < 1)
>>>> +		usage();
>>>> +
>>>> +	fd = dial(smprint("ipmux!%s", argv[0]), nil, nil, nil);
>>>> +	if(fd < 0)
>>>> +		sysfatal("dial: %r");
>>>> +
>>>> +	for(;;)
>>>> +		switch(read(fd, buf, sizeof buf)){
>>>> +		case -1:
>>>> +			sysfatal("read: %r");
>>>> +		case 0:
>>>> +			return;
>>>> +		}
>>>> +}
>>>
>>
>>