loopback routes pinned by commit r326012 for FreeBSD 10 cannot be deleted

[Rodney W. Grimes]

> 24.02.2018 19:37, Andreas Longwitz wrote:
> 
> >> Please test the follwoind patch for the kernel:
> >>
> >> --- sys/net/if.c.orig	2018-02-24 08:00:34.578670000 +0700
> >> +++ sys/net/if.c	2018-02-24 11:07:57.014318000 +0700
> >> @@ -1699,7 +1699,7 @@ ifa_del_loopback_route(struct ifaddr *if
> >>  	null_sdl.sdl_type = ifa->ifa_ifp->if_type;
> >>  	null_sdl.sdl_index = ifa->ifa_ifp->if_index;
> >>  	bzero(&info, sizeof(info));
> >> -	info.rti_flags = ifa->ifa_flags | RTF_HOST | RTF_STATIC;
> >> +	info.rti_flags = ifa->ifa_flags | RTF_HOST | RTF_STATIC | RTF_PINNED;
> >>  	info.rti_info[RTAX_DST] = ia;
> >>  	info.rti_info[RTAX_GATEWAY] = (struct sockaddr *)&null_sdl;
> >>  	error = rtrequest1_fib(RTM_DELETE, &info, NULL, ifa->ifa_ifp->if_fib);
> >>
> > 
> > This patch patch solves the problem for "ifconfig fxp0 delete": now the
> > kernel removes the loopback route, tested on FreeBSD 10 r328260.
> 
> Glad to know that.
> 
> > But deleting the loopback route manually does not work anymore, is this
> > intended behaviour ?
> > 
> > I would like to control the routing table as much as possible.
> 
> This is side effect of loopback routes being intentionally protected with RTF_PINNED flag
> in recent FreeBSD versions so that link routes can override ones installed by routing daemons.
> 
> Perhaps, ifconfig(8) utility should be extended to use RTF_PINNED to be able to modify such routes.

Perhaps it is a rather serious and undesired side effect to have such routes
without simple user ability to control them.

I am going to write a patch that wraps whis whole loopback_route
management in a kernel compile time option, which well leaves things
as they are now, but allow a user to remove this non-sensical route
policy code from there kernel.

It shall also have a sysctl that can turn these routes off so that
a GENERIC kernel can be used without this non-sense kernel routing
policy.  The default of this sysctl shall leave things as they
are now.


-- 
Rod Grimes                                                 rgrimes at freebsd.org