[REVIEW]: add multicast NULL route

[John Merryweather Cooper]

Poul-Henning Kamp wrote:
> On a system without a default route, multicast simply doesn't work.
> 
> This patch adds a route into lo0 for the entire multicast space.
> 
> A similar route were created in /etc/netstart until version 1.32
> where it was moved to sysconfig (1.14) where the incorrect resolution
> to conf/1007 commented it out in (1.36) and subsequently it was
> lost in the conversion to new rc world ordering.
> 
> As a stylistic feature of this patch, we no longer encroach on the
> administrators namespace by prepending a couple of "__" on the
> internal magic routes.
> 
> Review and comments please.
> 
> Index: routing
> ===================================================================
> RCS file: /home/ncvs/src/etc/rc.d/routing,v
> retrieving revision 1.143
> diff -u -r1.143 routing
> --- routing	2 May 2007 15:49:30 -0000	1.143
> +++ routing	15 Jun 2007 22:03:59 -0000
> @@ -31,12 +31,17 @@
>  
>  static_start()
>  {
> +	# The multicast range must be covered by a route, one way or another
> +	# or multicast will simply not work.
> +	static_routes="__mcast ${static_routes}"
> +	route___mcast="-static -net 224.0.0.0/4 -interface lo0"
> +
>  	case ${defaultrouter} in
>  	[Nn][Oo] | '')
>  		;;
>  	*)
> -		static_routes="default ${static_routes}"
> -		route_default="default ${defaultrouter}"
> +		static_routes="__default ${static_routes}"
> +		route___default="__default ${defaultrouter}"
>  		;;
>  	esac
>  
Creating this default route for non-gateway machines might be useful for 
GNOME and KDE machines where some of the utility programs want multicast 
access.  Maybe put this in a startup script GNOME and KDE could share? 
I've got mine in rc.local.

I like using lo0 instead of my outside interface for the static route. 
However, it occurs to me that the uninitiated could be frustrated by 
default firewall settings.  In particular, the 224.0.0.0/4 isn't going 
to pass through anti-spoofing rules for lo0.

jmc