Hi Petr,
On 10.09.2021 12:36, Petr Vorel wrote:

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On 09.09.2021 18:53, pvorel wrote:

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Hi Su, Alexey,

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On 2021-08-30 11:26, suy.fnst@fujitsu.com wrote:

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Hi,
? I found that it's indeed related to ipv6 DAD as you said.
Calling
`ip netns exec ltp_ns sysctl -n net.ipv6.conf.ltp_ns_veth1.accept_dad=0`
or tst_wait_ipv6_dad() at end of the setup both solves the problem.
However there is one super strange part that the tentative address is
the local link adress of the ltp_ns_veth1:

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5: ltp_ns_veth1@if4: <BROADCAST,UP,LOWER_UP> mtu 1500 qdisc noqueue
state UP group default qlen 1000
??? link/ether f2:8f:24:d4:ba:26 brd ff:ff:ff:ff:ff:ff link-netnsid 0
??? inet 10.0.0.1/24 scope global ltp_ns_veth1
?????? valid_lft forever preferred_lft forever
??? inet6 fd00:1:1:1::1/64 scope global nodad
?????? valid_lft forever preferred_lft forever
??? inet6 fe80::f08f:24ff:fed4:ba26/64 scope link tentative
<-------------------
?????? valid_lft forever preferred_lft forever

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However, there is no place using the address in mpls02 test.>> It makes me wonder how could it be possible to trigger the issue..

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Looks like the problem here in the neighbor discovery of fd00:1:1:1::2
using link-local address, and vice verse for the other side. mpls is
using the following route with the address:

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fd00:23::2  encap mpls  60 via fd00:1:1:1::2 dev ltp_ns_veth1 metric 1024 pref medium
so the address there should be in a reachable state...

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Thanks for info! I wonder if it's a bug in mpls or elsewhere. WDYT?

https://github.com/iputils/iputils/issues/300

Ah, thanks for pointing this.

So we should be careful with the flood option in ping, especially
if it is the first test to run after initial test interfaces setup.
For example, for mpls02, it is "icmp tcp udp".

Flooding is done with -f or -i 0. IMHO we don't do that in tst_ping(),
what am I missing? The bug is about flooding (-i 0) with zero packet size (-s 0,
but maybe our use -s 10 would trigger the bug as well).

Kind regards,
Petr

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Adding it manually in setup might fix the test as well:

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ROD ip neigh replace $(tst_ipaddr rhost) lladdr $(tst_hwaddr rhost) dev $(tst_iface) nud reachable
tst_rhost_run -s -c "ip neigh replace $(tst_ipaddr) lladdr $(tst_hwaddr) dev $(tst_iface rhost) nud reachable"

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I wonder if test still needs be fixed to work on all setups.

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I think we could set accept_dad to 0 in generic setup of the
test interfaces, in tst_net.sh/tst_init_iface().

Unless it's a bug we'd hide by setting it, I'd be for this general solution.

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It'd be nice to get it fixed before release.

OK