kern/185395: IPv4 Multicast broken in 10.x

[Peter Jeremy]

>Number:         185395
>Category:       kern
>Synopsis:       IPv4 Multicast broken in 10.x
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Jan 01 19:40:00 UTC 2014
>Closed-Date:
>Last-Modified:
>Originator:     Peter Jeremy
>Release:        FreeBSD 10.0-PRERELEASE amd64
>Organization:
n/a
>Environment:
System: FreeBSD server.rulingia.com 10.0-PRERELEASE FreeBSD 10.0-PRERELEASE #22 r259613M: Sat Dec 21 09:49:27 EST 2013 root at server.rulingia.com:/var/obj/usr/src/sys/server amd64

Also verified on 10.0-ALPHA1 r255569 arm and r259613M i386.

>Description:
	IPv4 multicast ethernet frames use the IP address of the default
	route in the destination MAC address, instead of the IP address of
	the multicast destination.  This breaks multicast filtering at the
	receiver.

	This is a regression from FreeBSD 9.2.

>How-To-Repeat:

	Run (eg) 'tcpdump -e icmp' on one terminal and 'ping 224.18.52.86'
	in another window.  The tcpdump should show ICMP packets with a
	destination MAC address of 01:00:5E:12:34:56 but, in my case, they
	have a destination MAC address of 01:00:5E:28:7B:7B - which matches
	the IP address of my router.

>Fix:
	Unknown.  The cause isn't obvious from a cursory look at the 9.x
	and 10.x code.
>Release-Note:
>Audit-Trail:
>Unformatted: