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

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Date:   Thu, 7 Nov 2019 11:35:07 -0500
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>, scott.drennan@...ia.com,
        Jiri Benc <jbenc@...hat.com>, martin.varghese@...ia.com
Subject: Re: [PATCH net-next 1/2] UDP tunnel encapsulation module for
 tunnelling different protocols like MPLS,IP,NSH etc.

On Thu, Nov 7, 2019 at 11:12 AM Martin Varghese
<martinvarghesenokia@...il.com> wrote:
>
> On Thu, Nov 07, 2019 at 10:53:47AM -0500, Willem de Bruijn wrote:
> > > > I do think that with close scrutiny there is a lot more room for code
> > > > deduplication. Just look at the lower half of geneve_rx and
> > > > bareudp_udp_encap_recv, for instance. This, too, is identical down to
> > > > the comments. Indeed, is it fair to say that geneve was taken as the
> > > > basis for this device?
> > > >
> > > > That said, even just avoiding duplicating those routing functions
> > > > would be a good start.
> > > >
> > > > I'm harping on this because in other examples in the past where a new
> > > > device was created by duplicating instead of factoring out code
> > > > implementations diverge over time in bad ways due to optimizations,
> > > > features and most importantly bugfixes being applied only to one
> > > > instance or the other. See for instance tun.c and tap.c.
> > > >
> > > > Unrelated, an ipv6 socket can receive both ipv4 and ipv6 traffic if
> > > > not setting the v6only bit, so does the device need to have separate
> > > > sock4 and sock6 members? Both sockets currently lead to the same
> > > > bareudp_udp_encap_recv callback function.
> > >
> > > I was checking this.AF_INET6 allows v6 and v4 mapped v6 address.
> > > And it doesnot allow both at the same time.So we need both
> > > sockets to support v4 and v6 at the same time.correct ?
> >
> > bareudp_create_sock currently creates an inet socket listening on
> > INADDR_ANY and an inet6 socket listening on in6addr_any with v6only.
> > If so, just the latter without v6only should offer the same.
>
> To receive and ipv4 packet in AF_INET6 packet we need to pass v4 address
> in v6 format( v4 mapped v6 address). Is it not ?

If the bareudp device binds to a specific port on all local addresses,
which I think it's doing judging from what it passes to udp_sock_create
(but I may very well be missing something), then in6addr_any alone will
suffice to receive both v6 and v4 packets.