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From:   Eric Dumazet <edumazet@google.com>
Date:   Tue, 1 Sep 2020 09:56:28 +0200
Message-ID: <CANn89iKA5Ut4AcZfsZi3bVpE33_pqgO=E1RhBzePUeBDn6gznQ@mail.gmail.com>
Subject: Re: [PATCH] net: ipv6: fix __rt6_purge_dflt_routers when forwarding
 is not set on all ifaces
To:     Brian Vazquez <brianvv@google.com>
Cc:     Brian Vazquez <brianvv.kernel@gmail.com>,
        "David S . Miller" <davem@davemloft.net>,
        LKML <linux-kernel@vger.kernel.org>,
        netdev <netdev@vger.kernel.org>,
        David Ahern <dsa@cumulusnetworks.com>
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On Tue, Sep 1, 2020 at 8:58 AM Brian Vazquez <brianvv@google.com> wrote:
>
> The problem is exposed when the system has multiple ifaces and
> forwarding is enabled on a subset of them, __rt6_purge_dflt_routers will
> clean the default route on all the ifaces which is not desired.
>
> This patches fixes that by cleaning only the routes where the iface has
> forwarding enabled.
>
> Fixes: 830218c1add1 ("net: ipv6: Fix processing of RAs in presence of VRF")


> Cc: David Ahern <dsa@cumulusnetworks.com>
> Signed-off-by: Brian Vazquez <brianvv@google.com>
> ---
>  net/ipv6/route.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index 5e7e25e2523a..41181cd489ea 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -4283,6 +4283,7 @@ static void __rt6_purge_dflt_routers(struct net *net,
>                                      struct fib6_table *table)
>  {
>         struct fib6_info *rt;
> +       bool deleted = false;
>
>  restart:
>         rcu_read_lock();
> @@ -4291,16 +4292,19 @@ static void __rt6_purge_dflt_routers(struct net *net,
>                 struct inet6_dev *idev = dev ? __in6_dev_get(dev) : NULL;
>
>                 if (rt->fib6_flags & (RTF_DEFAULT | RTF_ADDRCONF) &&
> -                   (!idev || idev->cnf.accept_ra != 2) &&
> +                   (!idev || (idev->cnf.forwarding == 1 &&
> +                              idev->cnf.accept_ra != 2)) &&
>                     fib6_info_hold_safe(rt)) {
>                         rcu_read_unlock();
>                         ip6_del_rt(net, rt, false);
> +                       deleted = true;
>                         goto restart;
>                 }
>         }
>         rcu_read_unlock();
>
> -       table->flags &= ~RT6_TABLE_HAS_DFLT_ROUTER;
> +       if (deleted)
> +               table->flags &= ~RT6_TABLE_HAS_DFLT_ROUTER;


This seems wrong : We want to keep the flag set if at least one
candidate route has not been deleted,
so that next time rt6_purge_dflt_routers() is called, we can call
__rt6_purge_dflt_routers() ?