Re: [PATCH net-next 0/3] ipmr/ip6mr: add Netlink notifications on cache reports

On 15/06/17 14:33, Nikolay Aleksandrov wrote:

On 15/06/17 00:51, Julien Gomes wrote:

quoted

Hi Nikolay,

On 06/14/2017 05:04 AM, Nikolay Aleksandrov wrote:

quoted

This has been on our todo list and I'm definitely interested in the implementation.
A few things that need careful consideration from my POV. First are the security
implications - this sends rtnl multicast messages but the rtnl socket has
the NL_CFG_F_NONROOT_RECV flag thus allowing any user on the system to listen in.
This would allow them to see the full packets and all reports (granted they can see
the notifications even now), but the full packet is like giving them the opportunity
to tcpdump the PIM traffic.

I definitely see how this can be an issue.
From what I see, this means that either the packet should be
transmitted another way, or another Netlink family should be used.

NETLINK_ROUTE looks to be the logical family to choose though,
but then I do not see a proper other way to handle this.

Right, currently me neither, unless it provides a bind callback when registering
the kernel socket.

quoted

However I may just not be looking into the right direction,
maybe you currently have another approach in mind?

I haven't gotten around to make (or even try) them but I was thinking about 2 options
ending up with a similar result:

1) genetlink
 It also has the NONROOT_RECV flag, but it also allows for a callback - mcast_bind()
 which can be used to filter.

or

2) Providing a bind callback to the NETLINK_ROUTE socket.

Ah nevermind, these cannot be used for filtering currently, so it seems
the netlink interface would need to be extended too if going down this road.

I haven't checked in detail how feasible each option is. To me 2) seems like the
cleaner/proper way to do it but it requires extending the rtnetlink api.

It would be nice to get feedback and comments from more people on this.

quoted

quoted

My second (more fixable and minor) concern is about the packet itself, how do you
know that the packet is all linear so you can directly copy it ?

Indeed, I overlooked this possibility in this version.
I will improve that.

Thanks!