netdev - Re: [PATCH net-next] ipv6: Allow the l3mdev to be a loopback

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Message-ID: <bd5d267a-f419-4735-bdf1-eee2a1f7135d@gmail.com>
Date:   Wed, 19 Sep 2018 10:19:05 -0700
From:   David Ahern <dsahern@...il.com>
To:     Mike Manning <mmanning@...tta.att-mail.com>, netdev@...r.kernel.org
Cc:     Robert Shearman <rshearma@...tta.att-mail.com>
Subject: Re: [PATCH net-next] ipv6: Allow the l3mdev to be a loopback

On 9/19/18 5:56 AM, Mike Manning wrote:
> From: Robert Shearman <rshearma@...tta.att-mail.com>
> 
> There is no way currently for an IPv6 client connect using a loopback
> address in a VRF, whereas for IPv4 the loopback address can be added:
> 
>     $ sudo ip addr add dev vrfred 127.0.0.1/8
>     $ sudo ip -6 addr add ::1/128 dev vrfred
>     RTNETLINK answers: Cannot assign requested address
> 
> So allow ::1 to be configured on an L3 master device. In order for
> this to be usable ip_route_output_flags needs to not consider ::1 to
> be a link scope address (since oif == l3mdev and so it would be
> dropped), and ipv6_rcv needs to consider the l3mdev to be a loopback
> device so that it doesn't drop the packets.
> 
> Signed-off-by: Robert Shearman <rshearma@...tta.att-mail.com>
> Signed-off-by: Mike Manning <mmanning@...tta.att-mail.com>
> ---
>  net/ipv6/addrconf.c  | 1 +
>  net/ipv6/ip6_input.c | 3 ++-
>  net/ipv6/route.c     | 3 ++-
>  3 files changed, 5 insertions(+), 2 deletions(-)
> 

Reviewed-by: David Ahern <dsahern@...il.com>

Been on my to-do list for a while. Thanks for the patch. This resolves,
for example, a harmless error message from the 'host' command from
bind9-host-9.10.3 which probes for dscp support via the loopback
address. e.g.,

$ host www.google.com
../../../../lib/isc/unix/net.c:581: sendmsg() failed: Network is unreachable