netdev - Re: [PATCHv3 net-next] VXLAN: fix nonfunctional neigh

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Message-ID: <CAHA+R7N0-Ffb325JciRH3Y6MwcpymxWLEtsu45t5HoarAccR4g@mail.gmail.com>
Date:	Tue, 18 Mar 2014 10:36:01 -0700
From:	Cong Wang <cwang@...pensource.com>
To:	David L Stevens <dlstevens@...ibm.com>
Cc:	David Miller <davem@...emloft.net>,
	Stephen Hemminger <shemminger@...tta.com>,
	Cong Wang <amwang@...hat.com>, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCHv3 net-next] VXLAN: fix nonfunctional neigh_reduce

On Tue, Mar 18, 2014 at 9:20 AM, David L Stevens <dlstevens@...ibm.com> wrote:
>
>         The VXLAN neigh_reduce() code is completely non-functional since
> check-in. Specific errors:
>
> 1) The original code drops all packets with a multicast destination address,
>         even though neighbor solicitations are sent to the solicited-node
>         address, a multicast address. The code after this check was never run.
> 2) The neighbor table lookup used the IPv6 header destination, which is the
>         solicited node address, rather than the target address from the
>         neighbor solicitation. So neighbor lookups would always fail if it
>         got this far. Also for L3MISSes.
> 3) The code calls ndisc_send_na(), which does a send on the tunnel device.
>         The context for neigh_reduce() is the transmit path, vxlan_xmit(),
>         where the host or a bridge-attached neighbor is trying to transmit
>         a neighbor solicitation. To respond to it, the tunnel endpoint needs
>         to do a *receive* of the appropriate neighbor advertisement. Doing a
>         send, would only try to send the advertisement, encapsulated, to the
>         remote destinations in the fdb -- hosts that definitely did not do the
>         corresponding solicitation.
> 4) The code uses the tunnel endpoint IPv6 forwarding flag to determine the
>         isrouter flag in the advertisement. This has nothing to do with whether
>         or not the target is a router, and generally won't be set since the
>         tunnel endpoint is bridging, not routing, traffic.
>
>         The patch below creates a proxy neighbor advertisement to respond to
> neighbor solicitions as intended, providing proper IPv6 support for neighbor
> reduction.
>
> Changes since v2:
>
> - code cleanup suggested by Stephen Hemminger and Daniel Baluta
>
> Changes since v1:
>
> - reworked code to be structurally similar to arp_reduce() per Dave Miller
>
> Signed-Off-By: David L Stevens <dlstevens@...ibm.com>

I thought ipv6_stub->ndisc_send_na can be removed, but it is being
used by other driver. So your patch looks good to me:

Reviewed-by: Cong Wang <cwang@...pensource.com>
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