IPv6 Neighbor Discovery Problem with dc(4)

[Raymond Jimenez]

	On my network, several machines are having trouble recognizing an icmp6 
neighbor solicitation. This only happens to me when I use the dc driver, 
in combination with the ADMTek AN985 10/100BaseTX chipset. The machines 
are running a combination of 4.7 and -CURRENT. The network topology 
consists of 3 switches, 2 of Linksys make, and 1 of Gigafast make. The 
computers will not recognize each other even when on the same switch. 
Tcpdump on the sender of the packet shows that the other interface 
(should be) reciving the packets, but is sending out no reply. When two 
computers are using any other driver than dc(4), they can ping each 
other. However, when tcpdump is done on the system with dc, the other 
can ping it and send data packets back and forth. It continues working 
after tcpdump is stopped. I've searched, and found nothing.
	Is there something I should check?

Thanks in advance.

--

Below is the output of tcpdump -nlvvve ip6
(on the system that is ping6'ing the one with the dc(4) driver)

[raymond at shirayuki raymond]$ sudo tcpdump -nlevvv ip6 | tee
Password:
tcpdump: listening on ep0
20:57:37.306117 0:60:97:93:af:d0 33:33:ff:1a:49:c8 86dd 86: 
2001:470:1f00:256:260:97ff:fe93:afd0 > ff02::1:ff1a:49c8: icmp6: 
neighbor sol: who has 2001:470:1f00:256:203:6dff:fe1a:49c8(src lladdr: 
00:60:97:93:af:d0) (len 32, hlim 255)
20:57:38.306194 0:60:97:93:af:d0 33:33:ff:1a:49:c8 86dd 86: 
2001:470:1f00:256:260:97ff:fe93:afd0 > ff02::1:ff1a:49c8: icmp6: 
neighbor sol: who has 2001:470:1f00:256:203:6dff:fe1a:49c8(src lladdr: 
00:60:97:93:af:d0) (len 32, hlim 255)
20:57:39.306283 0:60:97:93:af:d0 33:33:ff:1a:49:c8 86dd 86: 
2001:470:1f00:256:260:97ff:fe93:afd0 > ff02::1:ff1a:49c8: icmp6: 
neighbor sol: who has 2001:470:1f00:256:203:6dff:fe1a:49c8(src lladdr: 
00:60:97:93:af:d0) (len 32, hlim 255)
20:57:41.306427 0:60:97:93:af:d0 33:33:ff:1a:49:c8 86dd 86: 
2001:470:1f00:256:260:97ff:fe93:afd0 > ff02::1:ff1a:49c8: icmp6: 
neighbor sol: who has 2001:470:1f00:256:203:6dff:fe1a:49c8(src lladdr: 
00:60:97:93:af:d0) (len 32, hlim 255)
20:57:42.306501 0:60:97:93:af:d0 33:33:ff:1a:49:c8 86dd 86: 
2001:470:1f00:256:260:97ff:fe93:afd0 > ff02::1:ff1a:49c8: icmp6: 
neighbor sol: who has 2001:470:1f00:256:203:6dff:fe1a:49c8(src lladdr: 
00:60:97:93:af:d0) (len 32, hlim 255)
20:57:43.306572 0:60:97:93:af:d0 33:33:ff:1a:49:c8 86dd 86: 
2001:470:1f00:256:260:97ff:fe93:afd0 > ff02::1:ff1a:49c8: icmp6: 
neighbor sol: who has 2001:470:1f00:256:203:6dff:fe1a:49c8(src lladdr: 
00:60:97:93:af:d0) (len 32, hlim 255)
20:57:45.306743 0:60:97:93:af:d0 33:33:ff:1a:49:c8 86dd 86: 
2001:470:1f00:256:260:97ff:fe93:afd0 > ff02::1:ff1a:49c8: icmp6: 
neighbor sol: who has 2001:470:1f00:256:203:6dff:fe1a:49c8(src lladdr: 
00:60:97:93:af:d0) (len 32, hlim 255)
20:57:46.306801 0:60:97:93:af:d0 33:33:ff:1a:49:c8 86dd 86: 
2001:470:1f00:256:260:97ff:fe93:afd0 > ff02::1:ff1a:49c8: icmp6: 
neighbor sol: who has 2001:470:1f00:256:203:6dff:fe1a:49c8(src lladdr: 
00:60:97:93:af:d0) (len 32, hlim 255)
^C
47 packets received by filter
0 packets dropped by kernel
[raymond at shirayuki raymond]$ ping6 sakura.wsyntax.com

PING6(56=40+8+8 bytes) 2001:470:1f00:256:260:97ff:fe93:afd0 --> 
2001:470:1f00:256:203:6dff:fe1a:49c8
^C
--- sakura.wsyntax.com ping6 statistics ---
56 packets transmitted, 0 packets received, 100% packet loss

-- 
Raymond Jimenez <raymond at chikage.wsyntax.com>
http://chikage.wsyntax.com <> cyanoacry at rakka.irc.wsyntax.com