netdev - Re: [PATCH v3 net-next 1/2] UDP tunnel encapsulation module for tunnelling different protocols like MPLS,IP,NSH etc.

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Date:   Thu, 2 Jan 2020 14:55:30 -0500
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Martin Varghese <martinvarghesenokia@...il.com>
Cc:     Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Network Development <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>, corbet@....net,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        scott.drennan@...ia.com, Jiri Benc <jbenc@...hat.com>,
        martin.varghese@...ia.com
Subject: Re: [PATCH v3 net-next 1/2] UDP tunnel encapsulation module for
 tunnelling different protocols like MPLS,IP,NSH etc.

On Tue, Dec 31, 2019 at 10:33 AM Martin Varghese
<martinvarghesenokia@...il.com> wrote:
>
> On Fri, Nov 29, 2019 at 01:18:36PM -0500, Willem de Bruijn wrote:
> > On Thu, Nov 28, 2019 at 11:25 AM Martin Varghese
> > <martinvarghesenokia@...il.com> wrote:
> > >
> > > On Mon, Nov 18, 2019 at 12:23:09PM -0500, Willem de Bruijn wrote:
> > > > On Sat, Nov 16, 2019 at 12:45 AM Martin Varghese
> > > > <martinvarghesenokia@...il.com> wrote:
> > > > >
> > > > > From: Martin Varghese <martin.varghese@...ia.com>
> > > > >
> > > > > The Bareudp tunnel module provides a generic L3 encapsulation
> > > > > tunnelling module for tunnelling different protocols like MPLS,
> > > > > IP,NSH etc inside a UDP tunnel.
> > > > >
> > > > > Signed-off-by: Martin Varghese <martin.varghese@...ia.com>
> >
> > > > > +static int bareudp_fill_metadata_dst(struct net_device *dev,
> > > > > +                                    struct sk_buff *skb)
> > > > > +{
> > > > > +       struct ip_tunnel_info *info = skb_tunnel_info(skb);
> > > > > +       struct bareudp_dev *bareudp = netdev_priv(dev);
> > > > > +       bool use_cache = ip_tunnel_dst_cache_usable(skb, info);
> > > > > +
> > > > > +       if (ip_tunnel_info_af(info) == AF_INET) {
> > > > > +               struct rtable *rt;
> > > > > +               struct flowi4 fl4;
> > > > > +
> > > > > +               rt = iptunnel_get_v4_rt(skb, dev, bareudp->net, &fl4, info,
> > > > > +                                       use_cache);
> > > > > +               if (IS_ERR(rt))
> > > > > +                       return PTR_ERR(rt);
> > > > > +
> > > > > +               ip_rt_put(rt);
> > > > > +               info->key.u.ipv4.src = fl4.saddr;
> > > > > +#if IS_ENABLED(CONFIG_IPV6)
> > > > > +       } else if (ip_tunnel_info_af(info) == AF_INET6) {
> > > > > +               struct dst_entry *dst;
> > > > > +               struct flowi6 fl6;
> > > > > +               struct bareudp_sock *bs6 = rcu_dereference(bareudp->sock);
> > > > > +
> > > > > +               dst = ip6tunnel_get_dst(skb, dev, bareudp->net, bs6->sock, &fl6,
> > > > > +                                       info, use_cache);
> > > > > +               if (IS_ERR(dst))
> > > > > +                       return PTR_ERR(dst);
> > > > > +
> > > > > +               dst_release(dst);
> > > > > +               info->key.u.ipv6.src = fl6.saddr;
> > > > > +#endif
> > > > > +       } else {
> > > > > +               return -EINVAL;
> > > > > +       }
> > > > > +
> > > > > +       info->key.tp_src = udp_flow_src_port(bareudp->net, skb,
> > > > > +                                            bareudp->sport_min,
> > > > > +                                            USHRT_MAX, true);
> > > > > +       info->key.tp_dst = bareudp->conf.port;
> > > > > +       return 0;
> > > > > +}
> > > >
> > > > This can probably all be deduplicated with geneve_fill_metadata_dst
> > > > once both use iptunnel_get_v4_rt.
> > > >
> > >
> > > Do you have any preference of file to keep the common function
> >
> > Perhaps net/ipv4/udp_tunnel.c
>
> I was trying this change and i found i dont have a lot of generic code here.
>
> Populating L4 ports is function of the protocol implementation
> and it is differnt for geneve and for bareudp

If geneve can use iptunnel_get_v4_rt, then it seems like the only
implementation specific logic is deriving net and sk. Would it help to
just pass those explicitly to the shared helper
(udptunnel_fill_metadata_dst)?

It is hard to say without seeing the geneve conversion to
iptunnel_get_v4_rt. Maybe that throws up a constraint I'm missing.
Lacking that, I'll trust your judgment.

> The one thing we could do is to write a generic API to derive the
> tunnel src address.
>
> But since it is a very small piece i dont see much value add by making it
> generic and i prefer to keep the way as it is now

In that case, that sounds sensible.


>
> But i am open for both the option. What you think ?
>
>
>