Ipv6 - problem with multicast addresses

[Brecht Vermeulen]

Hi all,

I did some further testing on the problem with IPv6 and multicast
addresses for sollicitation messages (see mail of Frederik Scholaert).

So the problem is further compressed to:

host 1 (eth1)  ----    host 2 (eth 2)

I have 3 scenarios (with a fresh reboot of both machines in between)

1) if we load on both hosts the ipv6 module, then it is possible to ping
from host 1 to the link scope address of host 2. (everything is
auto-magically configured, we do not nothing)
ping6 fe80::250:baff:feca:2cae -I eth1  

on host 1, we see
tcpdump: listening on eth1
04:42:52.504557 :: > ff02::1:ff07:acd4: icmp6: neighbor sol: who has
fe80::250:baff:fe07:acd4
04:42:56.504584 fe80::250:baff:fe07:acd4 > ip6-allrouters: icmp6: router
solicitation
04:43:00.504555 fe80::250:baff:fe07:acd4 > ip6-allrouters: icmp6: router
solicitation
04:43:01.045766 fe80::250:baff:fe07:acd4 > ff02::1:ffca:2cae: icmp6:
neighbor sol: who has fe80::250:baff:feca:2cae
04:43:01.045896 fe80::250:baff:feca:2cae > fe80::250:baff:fe07:acd4:
icmp6: neighbor adv: tgt is fe80::250:baff:feca:2cae
04:43:01.045934 fe80::250:baff:fe07:acd4 > fe80::250:baff:feca:2cae:
icmp6: echo request
04:43:01.046038 fe80::250:baff:feca:2cae > fe80::250:baff:fe07:acd4:
icmp6: echo reply
04:43:02.044621 fe80::250:baff:fe07:acd4 > fe80::250:baff:feca:2cae:
icmp6: echo request
04:43:02.044727 fe80::250:baff:feca:2cae > fe80::250:baff:fe07:acd4:
icmp6: echo reply
04:43:03.044605 fe80::250:baff:fe07:acd4 > fe80::250:baff:feca:2cae:
icmp6: echo request

So, this works.

2) on host 1, we load the ipv6 module, on host 2 we load click with the
following config:
echo "FromDevice(eth1,1)->Print(yes)->Discard;"> /proc/click/config

and we do the same ping from host 1 to host 2 : nothing is printed by
click (a tcpdump on host 1 shows 
tcpdump: listening on eth1
04:51:06.010989 fe80::250:baff:fe07:acd4 > ff02::1:ffca:2cae: icmp6:
neighbor sol: who has fe80::250:baff:feca:2cae
04:51:07.004349 fe80::250:baff:fe07:acd4 > ff02::1:ffca:2cae: icmp6:
neighbor sol: who has fe80::250:baff:feca:2cae
04:51:08.004341 fe80::250:baff:fe07:acd4 > ff02::1:ffca:2cae: icmp6:
neighbor sol: who has fe80::250:baff:feca:2cae

If we then however load ipv6 on host2, then the packets are printed in
the syslog (without stopping click).
We use the kernel level click module of Jan. 11th, 2002 with linux
2.2.19. The ethernet cards are DLINK DFE 530TX with via-rhine
(non-polling) driver. I haven't tried with other cards yet.

3) if we start on host 2 a tcpdump, load the ipv6 modules on both hosts
and do the ping from host1 to host2, then it is the same as in scenario
2, no packets at host2, but tcpdump on host 1 sees the packets. If we
stop tcpdump on host 2 and start tcpdump again, then we see the packets.
(tried with libpcap 0.4a6/tcpdump 3.7.1 and libpcap 0.6.2/tcpdump 3.6.2,
hope these are the correct version numbers).



If we look at the ethernet headers, we see
tcpdump: listening on eth1
04:51:20.932240 0:50:ba:7:ac:d4 33:33:ff:ca:2c:ae 86dd 86:
fe80::250:baff:fe07:acd4 > ff02::1:ffca:2cae: icmp6: neighbor sol: who
has fe80::250:baff:feca:2cae

so, the destination MAC address is 33:33:... which is an ethernet
multicast. 

So, scenario 2 seems very strange to me as I thought that click just
took over the networking from Linux, but how comes then that it doesn't
see any packet and that the loading of the ipv6 module makes that this
works.
Or could there be something broken with the multicast ethernet addresses
and the card (although click is in promiscuous mode) ?

Our system is debian 2.2 (potato), kernel 2.2.19 with Click patch. (for
all scenarios, Click is however not loaded in the 1st and 3rd scenario).

anyone any good idea (next possibilities I see is testing with other
cards, 2.4.x kernels) ?

regards,
Brecht








Hi,

I'm experimenting with IPv6 in click. It works pretty well except for
the
fact that i'm not able to receive all-nodes or all-router multicast
addresses in my click config.

My configuration is like this:

|HOST|-ETH1-fec0:0:0:1::65/64---ETH1-|CLICK
ROUTER|-ETH2---fec0:0:0:2::66/64-ETH1-|HOST|
                          [fec0:0:0:1::64/64]  [fec0:0:0:2::64/64]


The IPv6-addresses fec0:0:0:1::64 and fec0:0:0:2::64 are not really
assigned because IPv6 is not loaded on the click router.

When for instance the IPv6 Click config is loaded and i load IPv6 on the
left host, the all-routers sollicitation packets don't seem to arrive at
the click router. Or, when i do a ping fec0:0:0:2::66 on the left host,
i
see 'fec0:0:0:1::65 > ff02::1:ff00:64: icmp6: neighbor sol: who has
fec0:0:0:1::64' -packets (leaving?) on eth1 of the left host, but they
also do not seem to arrive at the click router. (I have a Print-element
there after a FromDevice(eth1,1)-element and see nothing).

But when i first load the IPv6-module on the click-router and actually
assign the fec0:0:0:1::64 and fec0:0:0:2::64 addresses, and then
afterwards load click, i can ping through the click router.

I don't think it should have to be this way. Shouldn't i be able to run
a
IPv6 click config completely indepedent of IPv6 in the Linux kernel?

I use a click-version from january (from cvs), and kernel 2.2.19.

Can somebody help me on this matter?

regards,
Frederik