netdev - Re: VRF NS for lladdr sent on the wrong interface

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Date:   Mon, 30 Nov 2020 18:15:06 -0700
From:   David Ahern <dsahern@...il.com>
To:     Stephen Suryaputra <ssuryaextr@...il.com>, netdev@...r.kernel.org
Subject: Re: VRF NS for lladdr sent on the wrong interface

On 11/23/20 5:23 PM, Stephen Suryaputra wrote:
> Hi,
> 
> I'm running into a problem with lladdr pinging all-host mcast all nodes
> addr. The ping intially works but after cycling the interface that
> receives the ping, the echo request packet causes a neigh solicitation
> being sent on a different interface.
> 
> To repro, I included the attached namespace scripts. This is the
> topology and an output of my test.
> 
> # +-------+     +----------+   +-------+
> # | h0    |     |    r0    |   |    h1 |
> # |    v00+-----+v00    v01+---+v10    |
> # |       |     |          |   |       |
> # +-------+     +----------+   +-------+
> 



after setup,

ip netns exec h0 ping -c 1 ff02::1%h0_v00

works, but

 ip netns exec h1 ping -c 1 ff02::1%h1_v10

does not. No surprise then that cycling v00 in r0 causes the reverse.
The problem is the route order changes:

root@...ntu-c-2-4gib-sfo3-01:~# diff -U3 /tmp/1 /tmp/2
--- /tmp/1	2020-12-01 01:07:39.795361392 +0000
+++ /tmp/2	2020-12-01 01:07:51.991808848 +0000
@@ -1,6 +1,6 @@
 local fe80::8466:b3ff:fecc:3a4f dev r0_v01 table 10 proto kernel metric
0 pref medium
 local fe80::b4ec:a8ff:fec3:33d9 dev r0_v00 table 10 proto kernel metric
0 pref medium
-fe80::/64 dev r0_v00 table 10 proto kernel metric 256 pref medium
 fe80::/64 dev r0_v01 table 10 proto kernel metric 256 pref medium
-ff00::/8 dev r0_v00 table 10 metric 256 pref medium
+fe80::/64 dev r0_v00 table 10 proto kernel metric 256 pref medium
 ff00::/8 dev r0_v01 table 10 metric 256 pref medium
+ff00::/8 dev r0_v00 table 10 metric 256 pref medium

With your patch does ping from both hosts work?

What about all of the tests in
tools/testing/selftests/net/fcnal-test.sh? specifically curious about
the 'LLA to GUA' tests (link local to global). Perhaps those tests need
a second interface (e.g., a dummy) that is brought up first to cause the
ordering to be different.