Openthread: on-mesh GUA unreachable when manually configured

[simonlingoogle]

Describe the bug
When an on-mesh GUA prefix is configured without SLAAC and DHCPv6, a node with manually configured GUA is not reachable from another node that is not configured with GUA of this prefix.

To Reproduce

1. Git commit id: 75a382d292b2271c0a6e202324550091753467f0
2. IEEE 802.15.4 hardware platform: OpenThread simulation
3. Build steps
4. Network topology
   Leader---Router

$ otns -bin ./cmake-build-debug/examples/apps/cli/
> node 1
Done
node 1> prefix add 2001::/64 pros med  # SLAAC not enabled
Done
node 1> netdataregister
Done
node 1> ipaddr
fdde:ad00:beef:0:0:ff:fe00:fc00
fdde:ad00:beef:0:0:ff:fe00:2000
fdde:ad00:beef:0:fd5d:286f:6cbb:7a39
fe80:0:0:0:b445:ce82:946a:1dea
node 1> node 2
Done
node 2> ipaddr add 2001::a:b:c:d  # manually config GUA on node 2
Done
node 2> ipaddr
2001:0:0:0:a:b:c:d
fdde:ad00:beef:0:0:ff:fe00:1400
fdde:ad00:beef:0:fa0b:36d5:6a8e:8db1
fe80:0:0:0:5c0e:5ba4:de3f:dcd9
Done
node 2> exit
Done
> ping 1 "2001::a:b:c:d" # `2001::a:b:c:d` unreachable from node 1
Done
> exit

Expected behavior
According to Spec. 5.15.7, node 1 should send address query for destination 2001::a:b:c:d, because the prefix is on-mesh, and then sends ping request successfully.
The source address for the ping request should be node 1's MLEID.

Console/log output
current.pcap.zip

However, if node 1 is also manually configured with a GUA of the same on-mesh prefix, it can do address query and send ping request successfully.

Thoughts on this issue?
@jwhui @librasungirl

[jwhui]

@simonlingoogle , thanks for raising this issue!

This is because we do not currently check IPv6 destination addresses against the set of on-mesh prefixes.
https://github.com/openthread/openthread/blob/46305be08269a3f1ec2a3364d565270e090b2dd7/src/core/net/ip6.cpp#L1469-L1483

I'll submit a proposed fix soon.

[jwhui]

@simonlingoogle , submitted #5024, please review.

[simonlingoogle]

Thanks @jwhui . I will verify the fix ASAP.

[simonlingoogle]

verified that this PR works: current.pcap.zip