netdev - Re: [PATCH net-next v7 1/2] net: UDP tunnel encapsulation module for tunnelling different protocols like MPLS,IP,NSH etc.

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Date:   Sun, 16 Feb 2020 12:26:18 -0600
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Martin Varghese <martinvarghesenokia@...il.com>
Cc:     Network Development <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Jonathan Corbet <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 net-next v7 1/2] net: UDP tunnel encapsulation module for
 tunnelling different protocols like MPLS,IP,NSH etc.

On Sat, Feb 15, 2020 at 12:20 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>

> +struct net_device *bareudp_dev_create(struct net *net, const char *name,
> +                                     u8 name_assign_type,
> +                                     struct bareudp_conf *conf)
> +{
> +       struct nlattr *tb[IFLA_MAX + 1];
> +       struct net_device *dev;
> +       LIST_HEAD(list_kill);
> +       int err;
> +
> +       memset(tb, 0, sizeof(tb));
> +       dev = rtnl_create_link(net, name, name_assign_type,
> +                              &bareudp_link_ops, tb, NULL);
> +       if (IS_ERR(dev))
> +               return dev;
> +
> +       err = bareudp_configure(net, dev, conf);
> +       if (err) {
> +               free_netdev(dev);
> +               return ERR_PTR(err);
> +       }
> +       err = dev_set_mtu(dev, IP_MAX_MTU);

does this not exceed dev->max_mtu?

> diff --git a/include/net/ipv6.h b/include/net/ipv6.h
> index cec1a54..1bf8065 100644
> --- a/include/net/ipv6.h
> +++ b/include/net/ipv6.h
> @@ -1027,6 +1027,12 @@ struct dst_entry *ip6_dst_lookup_flow(struct net *net, const struct sock *sk, st
>  struct dst_entry *ip6_sk_dst_lookup_flow(struct sock *sk, struct flowi6 *fl6,
>                                          const struct in6_addr *final_dst,
>                                          bool connected);
> +struct dst_entry *ip6_dst_lookup_tunnel(struct sk_buff *skb,
> +                                       struct net_device *dev,
> +                                       struct net *net, struct socket *sock,
> +                                       struct in6_addr *saddr,
> +                                       const struct ip_tunnel_info *info,
> +                                       u8 protocol, bool use_cache);
>  struct dst_entry *ip6_blackhole_route(struct net *net,
>                                       struct dst_entry *orig_dst);
>
> diff --git a/include/net/route.h b/include/net/route.h
> index a9c60fc..81750ae 100644
> --- a/include/net/route.h
> +++ b/include/net/route.h
> @@ -128,6 +128,12 @@ static inline struct rtable *__ip_route_output_key(struct net *net,
>
>  struct rtable *ip_route_output_flow(struct net *, struct flowi4 *flp,
>                                     const struct sock *sk);
> +struct rtable *ip_route_output_tunnel(struct sk_buff *skb,
> +                                     struct net_device *dev,
> +                                     struct net *net, __be32 *saddr,
> +                                     const struct ip_tunnel_info *info,
> +                                     u8 protocol, bool use_cache);
> +
>  struct dst_entry *ipv4_blackhole_route(struct net *net,
>                                        struct dst_entry *dst_orig);
>

Ah, I now see where the difference between net/ipv4/route.c and
net/ipv6/ip6_output.c come from. It follows from existing locations of
 ip6_sk_dst_lookup_flow and ip_route_output_flow.

Looking for the ipv6 analog of ip_route_output_flow, I see that, e.g.,
ipvlan uses ip6_route_output from net/ipv6/route.c without a NULL sk.
But ping calls ip6_sk_dst_lookup_flow.

It might be a better fit behind ip6_route_output_flags, but it's
probably moot, really.