Re: [iproute PATCH] iproute: fix filter_nlmsg

[Phil Sutter <phil@nwl.cc>]

On Tue, Nov 03, 2015 at 04:33:59PM -0800, Stephen Hemminger wrote:
> On Thu, 29 Oct 2015 12:15:47 +0100
> Phil Sutter <phil@nwl.cc> wrote:
> 
> > This patch is based upon an old Fedora bug[1] regarding the routing
> > setup of PPP links. I'm not quite sure if it still applies today or how
> > to trigger it, but looking at the change introducing this, it's
> > obviously a bug.
> > 
> > [1] https://bugzilla.redhat.com/show_bug.cgi?id=622782
> > 
> > Fixes: 4479282 ("iproute2: filter routing entries based on clone flag")
> > Signed-off-by: Phil Sutter <phil@nwl.cc>
> > ---
> >  ip/iproute.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/ip/iproute.c b/ip/iproute.c
> > index eab512d..ea7e9aa 100644
> > --- a/ip/iproute.c
> > +++ b/ip/iproute.c
> > @@ -151,7 +151,7 @@ static int filter_nlmsg(struct nlmsghdr *n, struct rtattr **tb, int host_len)
> >  	if (r->rtm_family == AF_INET6 && table != RT_TABLE_MAIN)
> >  		ip6_multiple_tables = 1;
> >  
> > -	if (filter.cloned == !(r->rtm_flags&RTM_F_CLONED))
> > +	if (filter.cloned && !(r->rtm_flags&RTM_F_CLONED))
> >  		return 0;
> >  
> >  	if (r->rtm_family == AF_INET6 && !ip6_multiple_tables) {
> 
> Holding off on this, until there is an obvious reproduction.
> The patch looks right but this code has been around a long time and don't want
> any surprised users.

Looking more into this, I found commit c73f3e0 ("iproute2: dont filter
cached routes on iproute_get") which bases explicitly on the behaviour
as we have now (comparison instead of boolean AND).

The above change at least affects showing routes for IPv6. With it
applied, 'ip r s' prints the routing cache along with normal routing
table entries, without it one has to explicitly ask for cached entries
in order for them to show up ('ip r s cached'). What do you think which
is the correct behaviour?

Thanks, Phil