Discussion:
[Bug 233535] Machines lost ping6 after adding same IPv6 address
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b***@freebsd.org
2018-11-27 07:01:21 UTC
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=233535

Mark Linimon <***@FreeBSD.org> changed:

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b***@freebsd.org
2018-11-27 08:56:33 UTC
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=233535

--- Comment #4 from Slava Shwartsman <***@FreeBSD.org> ---
(In reply to Conrad Meyer from comment #1)
Same issue appeared when setting the prefix:
HOST A: ifconfig igb0 inet6 2002::1/64
HOST B: ifconfig igb0 inet6 2002::2/64

# ping6 2002::2
PING6(56=40+8+8 bytes) 2002::1 --> 2002::2
16 bytes from 2002::2, icmp_seq=0 hlim=64 time=0.266 ms
16 bytes from 2002::2, icmp_seq=1 hlim=64 time=0.087 ms
^C
--- 2002::2 ping6 statistics ---
2 packets transmitted, 2 packets received, 0.0% packet loss
round-trip min/avg/max/std-dev = 0.087/0.176/0.266/0.090 ms
# ifconfig igb0 inet6 2002::1/64
# ping6 2002::2
PING6(56=40+8+8 bytes) fe80::ec4:7aff:fea8:b7f6%igb0 --> 2002::2
^C
--- 2002::2 ping6 statistics ---
54 packets transmitted, 0 packets received, 100.0% packet loss

# netstat -rn
Routing tables

Internet:
Destination Gateway Flags Netif Expire
default 10.209.52.1 UGS igb0
10.209.52.0/22 link#1 U igb0
10.209.52.157 link#1 UHS lo0
127.0.0.1 link#3 UH lo0

Internet6:
Destination Gateway Flags Netif
Expire
::/96 ::1 UGRS lo0
::1 link#3 UH lo0
::ffff:0.0.0.0/96 ::1 UGRS lo0
2002::/64 link#1 U igb0
2002::1 link#1 UHS lo0
fe80::/10 ::1 UGRS lo0
fe80::%igb0/64 link#1 U igb0
fe80::ec4:7aff:fea8:b7f6%igb0 link#1 UHS lo0
fe80::%lo0/64 link#3 U lo0
fe80::1%lo0 link#3 UHS lo0
ff02::/16 ::1 UGRS lo0


(In reply to Andrey V. Elsukov from comment #3)
I would expect that ping will continue to work.
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b***@freebsd.org
2018-11-27 09:39:30 UTC
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=233535

--- Comment #5 from Andrey V. Elsukov <***@FreeBSD.org> ---
(In reply to Slava Shwartsman from comment #4)
Post by b***@freebsd.org
(In reply to Andrey V. Elsukov from comment #3)
I would expect that ping will continue to work.
I'll try to reproduce this. But can you also show the output of `ifconfig igb0`
command? Are both addresses has "duplicated" flag?
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b***@freebsd.org
2018-11-27 11:25:47 UTC
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=233535

--- Comment #6 from Slava Shwartsman <***@FreeBSD.org> ---
(In reply to Andrey V. Elsukov from comment #5)
This is the output after the issue reproduced:

# ifconfig igb0
igb0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500

options=e527bb<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,TSO4,TSO6,LRO,WOL_MAGIC,VLAN_HWFILTER,VLAN_HWTSO,RXCSUM_IPV6,TXCSUM_IPV6>
ether 0c:c4:7a:a8:b7:f6
inet6 fe80::ec4:7aff:fea8:b7f6%igb0 prefixlen 64 scopeid 0x1
inet6 2002::1 prefixlen 64
inet 10.209.52.157 netmask 0xfffffc00 broadcast 10.209.55.255
media: Ethernet autoselect (1000baseT <full-duplex>)
status: active
nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>


# ifconfig igb0
igb0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500

options=e527bb<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,TSO4,TSO6,LRO,WOL_MAGIC,VLAN_HWFILTER,VLAN_HWTSO,RXCSUM_IPV6,TXCSUM_IPV6>
ether 0c:c4:7a:a8:b7:76
inet6 fe80::ec4:7aff:fea8:b776%igb0 prefixlen 64 scopeid 0x1
inet6 2002::2 prefixlen 64
inet 10.209.52.158 netmask 0xfffffc00 broadcast 10.209.55.255
media: Ethernet autoselect (1000baseT <full-duplex>)
status: active
nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
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b***@freebsd.org
2018-12-06 13:06:03 UTC
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=233535

--- Comment #7 from Slava Shwartsman <***@FreeBSD.org> ---
Any updates?
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b***@freebsd.org
2018-12-07 13:09:36 UTC
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Andrey V. Elsukov <***@FreeBSD.org> changed:

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--- Comment #8 from Andrey V. Elsukov <***@FreeBSD.org> ---
(In reply to Slava Shwartsman from comment #7)
Post by b***@freebsd.org
Any updates?
Sorry for long delay, I just tried your test scenario. And I'm able to
reproduce the problem. From a first look, it seems there is some race in
multicast/MLD code. I see that the host, that doesn't respond to ND6 NS, for
each NS packet increments the `ip6s_notmember` counter of ip6 statistics in
icmp6_input(). And ND6 code doesn't have a chance to send a reply.
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b***@freebsd.org
2018-12-08 11:16:41 UTC
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--- Comment #9 from Andrey V. Elsukov <***@FreeBSD.org> ---
It seems the problem is even worse. The system leaves multicast groups after
some time without any reconfiguration and stops to reply to ND6 NS.
1. ifmcstat before test:
em0:
inet 10.9.8.6
igmpv2
group 224.0.0.1 mode exclude
mcast-macaddr 01:00:5e:00:00:01
inet6 fe80::222:4dff:fe6a:5eb9%em0 scopeid 0x1
mldv1 flags=2<USEALLOW>
group ff01::1%em0 scopeid 0x1 mode exclude
mcast-macaddr 33:33:00:00:00:01
group ff02::1%em0 scopeid 0x1 mode exclude
mcast-macaddr 33:33:00:00:00:01
2. ifconfig em0 inet6 fc00::2
3. ifmcstat
em0:
inet6 fe80::222:4dff:fe6a:5eb9%em0 scopeid 0x1
mldv1 flags=2<USEALLOW>
group ff02::2:d4f1:c447%em0 scopeid 0x1 mode exclude
mcast-macaddr 33:33:d4:f1:c4:47
group ff02::2:ffd4:f1c4%em0 scopeid 0x1 mode exclude
mcast-macaddr 33:33:ff:d4:f1:c4
group ff02::1:ff00:2%em0 scopeid 0x1 mode exclude
mcast-macaddr 33:33:ff:00:00:02
inet 10.9.8.6
igmpv2
group 224.0.0.1 mode exclude
mcast-macaddr 01:00:5e:00:00:01
inet6 fe80::222:4dff:fe6a:5eb9%em0 scopeid 0x1
mldv1 flags=2<USEALLOW>
group ff01::1%em0 scopeid 0x1 mode exclude
mcast-macaddr 33:33:00:00:00:01
group ff02::1%em0 scopeid 0x1 mode exclude
mcast-macaddr 33:33:00:00:00:01
4. Wait about 1 minute
5. ifmcstat
em0:
inet 10.9.8.6
igmpv2
group 224.0.0.1 mode exclude
mcast-macaddr 01:00:5e:00:00:01
inet6 fe80::222:4dff:fe6a:5eb9%em0 scopeid 0x1
mldv1 flags=2<USEALLOW>
group ff01::1%em0 scopeid 0x1 mode exclude
mcast-macaddr 33:33:00:00:00:01
group ff02::1%em0 scopeid 0x1 mode exclude
mcast-macaddr 33:33:00:00:00:01
6. On the second host: ndp -c && ping6 fc00::2 => no reply
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b***@freebsd.org
2018-12-08 12:02:09 UTC
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=233535

Andrey V. Elsukov <***@FreeBSD.org> changed:

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--- Comment #10 from Andrey V. Elsukov <***@FreeBSD.org> ---
This looks like really bad problem for 12.0 release. Can somebody check and
confirm that the system leaves multicast groups? If it is not only my machine,
this can break IPv6 connectivity after upgrade.
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