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X-Bullshit: full-stack SOAP over SVG reduce/map-aware factory framework STM backend 
Subject: Re: [9front] [PITCH] ip/null
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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;
> +		}
> +}