Bug 180893

Summary: [if_ethersubr] [patch] Packets received with own LLADDR confuse things.
Product: Base System Reporter: dave <dave>
Component: kernAssignee: freebsd-bugs (Nobody) <bugs>
Status: Open ---    
Severity: Affects Only Me CC: dgilbert, zlei
Priority: Normal Keywords: patch
Version: 9.2-BETA1   
Hardware: Any   
OS: Any   
Attachments:
Description Flags
file.diff none

Description dave 2013-07-27 18:50:00 UTC 
	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.

How-To-Repeat: 	Simply install FreeBSD-9.1 on VMWare and enable IPv6.  DAD will
fail.
Comment 1 Mark Linimon freebsd_committer freebsd_triage 2013-07-30 03:12:37 UTC 
Responsible Changed
From-To: freebsd-bugs->freebsd-net

Over to maintainer(s).
Comment 2 Eitan Adler freebsd_committer freebsd_triage 2017-12-31 08:00:29 UTC 
For bugs matching the following criteria:

Status: In Progress Changed: (is less than) 2014-06-01

Reset to default assignee and clear in-progress tags.

Mail being skipped
Comment 3 Graham Perrin freebsd_committer freebsd_triage 2022-10-17 12:39:43 UTC 
Keyword: 

    patch
or  patch-ready

– in lieu of summary line prefix: 

    [patch]

* bulk change for the keyword
* summary lines may be edited manually (not in bulk). 

Keyword descriptions and search interface: 

    <https://bugs.freebsd.org/bugzilla/describekeywords.cgi>
Comment 4 dgilbert 2022-10-17 13:20:57 UTC 
Can I ask here... did someone edit the portion of this PR attributed to me?  I don't disagree or anything ... I'm just pretty sure I didn't type what's there (a few things I wouldn't say or claim ... and, while it's 10 years ago almost, I not only don't remember saying it ... but I didn't write the patch or choose where to patch)...

... It is something I might have reported --- but as another example, I don't use vmware.
Comment 5 dgilbert 2022-10-17 13:21:46 UTC 
hrm.  If it's not clear dave@daveg.ca == me
Comment 6 Zhenlei Huang freebsd_committer freebsd_triage 2022-10-17 14:36:02 UTC 
IIRC, upper layer requires the bouncing back multicast packets sent out in some circumstances. So it is arbitrary to drop them unconditionally.

This is a quit old report and FreeBSD-9.1 is not supported any longer. Should repeat on recent release versions, 12.3 or 13.1 .