em driver doesn't set multicast ethernet address

Bruce Simpson bms at incunabulum.net
Sat Jul 11 13:01:14 UTC 2009


Thanks for the feedback.

iprebeg at freebsd.org wrote:
> Well, now, something really interesting happened. I changed default IGMP
> version via sysctl
> # sysctl net.inet.igmp.default_version=2
> but, then I tested it with mtest and generated packets were still IGMPv3
> Membership reports, but first two of them had proper mcast ethernet
> address. They generated sent by mtest.

Sorry, forgot to mention -- this sysctl won't take effect immediately.
It needs to be set before the interface's driver is loaded and IPv4 is 
attached to the interface.

Do you have any unusual ARP table entries or routing setup? That would 
be where to look next.

There haven't been any other reports of this issue as far as I know. The 
IGMP code does not fill out the Ethernet address field -- it leaves it 
up to ip_output() to do that.

Do you see this with other multicast traffic, or just IGMP reports?


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