Date: Sat, 11 Jul 2009 09:14:29 +0100 From: Bruce Simpson <bms@incunabulum.net> To: iprebeg@freebsd.org Cc: jfv@FreeBSD.org, freebsd-net@freebsd.org Subject: Re: em driver doesn't set multicast ethernet address Message-ID: <4A5849E5.90909@incunabulum.net> In-Reply-To: <20090711073647.GA1824@valeria.zesoi.fer.hr> References: <20090711073647.GA1824@valeria.zesoi.fer.hr>
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iprebeg@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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