Please implement patch in PR180893

Mike Karels mike at
Sun Jul 28 04:45:39 UTC 2013

> Sure, but it would be nice to file bugs with VMware and such to ensure
> they fix their bugs.

fwiw, I use IPv6 with recent versions of ESXi and VMware Workstation,
and have not seen this problem.  I'm curious if the problem is in old
versions or with particular configurations.

> Anyone have any issue with this? The issue I have is the if_printf(),
> it should be rate limited at the very least. It would also be nice to
> have a different counter to reflect that kind of dropped packet..

Agreed to both; I'd rather reserve if_ierrors for NIC-reported errors.
I also think the message should say "from my MAC address" (vs IP).

> 2c,

2c more,


On 27 July 2013 13:49, Zaphod Beeblebrox <zbeeble at> wrote:
> I'd like to advocate implementing
> Quoting the PR:
> Some errant network equipment (including the simulation of a network
> by VMware, as an example) will reflect back multicast packets to the sender.
> This breaks protocols such as DAD and makes IPv6 nearly impossible to use
> on these networks.
> Now, the argument could be made to fix these network elements, but
> there is an elegant solution that improves the quality of FreeBSD: To refuse
> packets that have a source ethernet address of the receiving interface. If
> you consider this notion, you can quickly and easily accept that an
> interface
> should never "receive" a packet from it's own MAC address.
> This behaviour mirrors Linux behavior and I assume Windows behavior.
> I won't claim to be experienced in kernel matters, but I chose the
> location for this modification to allow BPF to "see" the packets (for
> network diagnosis). This test, however, could be moved within this function
> or even given a sysctl knob.
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