ipre...@freebsd.org wrote:
While testing -CURRENT in VMWare environment, I discovered that em
driver doesn't properly set destination address in Ethernet header. In
the other words, when I start listening multicast session with mcastread
(mcast-tools), kernel triggers IGMPv3 packet. Its destionation IP is
224.0.0.22, but its destionation Ethernet address doesn't look like
01:00:5e:... Other machines that I run in same environment (like
FreeBSD-7) behave in good manner.
It seems that the introduction of IGMPv3 may have exposed some
driver/hardware issues, where certain network interfaces are not able to
transmit on groups which haven't been joined for receive. This is a bug,
and would likely break production use of IPv6, which makes heavier use
of link-scope groups than IPv4 does.
Can you provide the following information please, so that someone can
better help you:
1) the date of the -CURRENT code you are using;
2) tcpdump or wireshark capture output, containing the actual output
generated by em(4).
Does this issue occur if you use the 'mtest' tool to join 224.0.0.22
inside the guest? The kernel will *not* listen to 224.0.0.22, unless
you're running a multicast routing daemon -- as it doesn't have to; that
link-scope group is for reports only.
This issue doesn't appear with IGMPv2, because it only ever transmits
its reports on the group thus joined. This has the disadvantage that
multicast routers have to have functioning promiscuous multicast
receive, just to proxy or forward traffic.
Can you force the use of IGMPv2 using the sysctls as defined in the
igmp(4) man page as a workaround?
thanks,
BMS
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