Re: [PATCH] net: ipv6: Disable forwarding per interface via sysctl

On 16.09.2016 15:39, Eric Dumazet wrote:

On Fri, 2016-09-16 at 13:47 +0100, Mike Manning wrote:

quoted

Disabling forwarding per interface via sysctl continues to allow
forwarding. This is contrary to the sysctl documentation stating that
the forwarding sysctl is per interface, whereas currently it is only
the sysctl for all interfaces that has an effect on forwarding. The
solution is to drop any received packets instead of forwarding them
if the ingress device has a per-device forwarding sysctl that is unset.

Some archaeological research might be needed because
Documentation/networking/ip-sysctl.txt states :

IPv4 and IPv6 work differently here; e.g. netfilter must be used
to control which interfaces may forward packets and which not.

If this netfilter requirement is obsolete, then your patch would need to
change the doc as well.

Hannes can probably comment on this ?

Yep, thanks.

This commit breaks a very common setup: people globally enabled
forwarding but disabled the forwarding knob on one special interface to
allow this interface to participate in auto configuration from their
provider while still forwarding packets over this interface.

I fear this is so common that this would be a uapi violation.

Thanks,
Hannes