lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Wed, 2 Dec 2020 10:37:47 +0100
From:   Steffen Klassert <>
To:     Eyal Birger <>
CC:     <>, David Miller <>,
        "Jakub Kicinski" <>,
        Linux Kernel Network Developers <>
Subject: Re: [PATCH ipsec-next] xfrm: interface: support collect metadata mode

On Fri, Nov 27, 2020 at 02:32:44PM +0200, Eyal Birger wrote:
> Hi Steffen,
> On Fri, Nov 27, 2020 at 11:44 AM Steffen Klassert
> <> wrote:
> >
> > On Sat, Nov 21, 2020 at 04:28:23PM +0200, Eyal Birger wrote:
> > > This commit adds support for 'collect_md' mode on xfrm interfaces.
> > >
> > > Each net can have one collect_md device, created by providing the
> > > IFLA_XFRM_COLLECT_METADATA flag at creation. This device cannot be
> > > altered and has no if_id or link device attributes.
> > >
> > > On transmit to this device, the if_id is fetched from the attached dst
> > > metadata on the skb. The dst metadata type used is METADATA_IP_TUNNEL
> > > since the only needed property is the if_id stored in the tun_id member
> > > of the ip_tunnel_info->key.
> >
> > Can we please have a separate metadata type for xfrm interfaces?
> >
> > Sharing such structures turned already out to be a bad idea
> > on vti interfaces, let's try to avoid that misstake with
> > xfrm interfaces.
> My initial thought was to do that, but it looks like most of the constructs
> surrounding this facility - tc, nft, ovs, ebpf, ip routing - are built around
> struct ip_tunnel_info and don't regard other possible metadata types.

That is likely because most objects that have a collect_md mode are
tunnels. We have already a second metadata type, and I don't see
why we can't have a third one. Maybe we can create something more
generic so that it can have other users too.

> For xfrm interfaces, the only metadata used is the if_id, which is stored
> in the metadata tun_id, so I think other than naming consideration, the use
> of struct ip_tunnel_info does not imply tunneling and does not limit the
> use of xfrmi to a specific mode of operation.

I agree that this can work, but it is a first step into a wrong direction.
Using a __be64 field of a completely unrelated structure as an u32 if_id
is bad style IMO.

> On the other hand, adding a new metadata type would require changing all
> other places to regard the new metadata type, with a large number of
> userspace visible changes.

I admit that this might have some disadvantages too, but I'm not convinced
that this justifies the 'ip_tunnel_info' hack.

Powered by blists - more mailing lists