netdev - Re: selftest fib_nexthop_multiprefix failed due to route mismatch

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Message-ID: <01240884-fcc9-46d5-ae98-305151112ebc@kernel.org>
Date: Tue, 21 Nov 2023 09:40:02 -0800
From: David Ahern <dsahern@...nel.org>
To: Hangbin Liu <liuhangbin@...il.com>
Cc: netdev@...r.kernel.org
Subject: Re: selftest fib_nexthop_multiprefix failed due to route mismatch

On 11/20/23 10:40 PM, Hangbin Liu wrote:
> Hi David,
> 
> Recently when run fib_nexthop_multiprefix test I saw all IPv6 test failed.
> e.g.
> 
> # ./fib_nexthop_multiprefix.sh
> TEST: IPv4: host 0 to host 1, mtu 1300                              [ OK ]
> TEST: IPv6: host 0 to host 1, mtu 1300                              [FAIL]
> 
> With -v it shows
> 
> COMMAND: ip netns exec h0 /usr/sbin/ping6 -s 1350 -c5 -w5 2001:db8:101::1
> PING 2001:db8:101::1(2001:db8:101::1) 1350 data bytes
> From 2001:db8:100::64 icmp_seq=1 Packet too big: mtu=1300
> 
> --- 2001:db8:101::1 ping statistics ---
> 1 packets transmitted, 0 received, +1 errors, 100% packet loss, time 0ms
> 
> Route get
> 2001:db8:101::1 via 2001:db8:100::64 dev eth0 src 2001:db8:100::1 metric 1024 expires 599sec mtu 1300 pref medium
> Searching for:
>     2001:db8:101::1 from :: via 2001:db8:100::64 dev eth0 src 2001:db8:100::1 .* mtu 1300
> 
> TEST: IPv6: host 0 to host 1, mtu 1300                              [FAIL]
> 
> So we can get the Packet too big from 2001:db8:100::64 successfully. There
> is no "from ::" anymore. I plan to fix this issue. But I can't find which
> commit changed the behavior and the client could receive Packet too big
> message with correct src address.
> 
> Do you have any hints?
> 
> Thanks
> Hangbin

v6.3.12:

$ sudo /mnt/hostshare/fib_nexthop_multiprefix.sh
TEST: IPv4: host 0 to host 1, mtu 1300                          [ OK ]
TEST: IPv6: host 0 to host 1, mtu 1300                          [ OK ]

TEST: IPv4: host 0 to host 2, mtu 1350                          [ OK ]
TEST: IPv6: host 0 to host 2, mtu 1350                          [ OK ]

TEST: IPv4: host 0 to host 3, mtu 1400                          [ OK ]
TEST: IPv6: host 0 to host 3, mtu 1400                          [ OK ]

TEST: IPv4: host 0 to host 1, mtu 1300                          [ OK ]
TEST: IPv6: host 0 to host 1, mtu 1300                          [ OK ]

TEST: IPv4: host 0 to host 2, mtu 1350                          [ OK ]
TEST: IPv6: host 0 to host 2, mtu 1350                          [ OK ]

TEST: IPv4: host 0 to host 3, mtu 1400                          [ OK ]
TEST: IPv6: host 0 to host 3, mtu 1400                          [ OK ]

v6.4.13 all passed as well, so it is something recent. I do not have a
6.5 or 6.6 kernels compiled at the moment.