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

[hiro <23hiro@gmail.com>]

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;
>>> +		}
>>> +}
>>
>
>