gnrc/ipv6/nib: rejoin ipv6_addr_all_nodes_link_local on interface up#20259
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Contribution description
An interface should rejoin the
ipv6_addr_all_nodes_link_localwhen brought up.We had a very annoying problem that sometimes a global address could not be configured on an
atwinc15x0.This PR shows how to trigger the problem and what fixes it.
Testing procedure
make -C examples/gnrc_networking flash termConnect to some access point.
The interface gets a global address.
Disconnect from the AP.
Delete the global address.
Now reset the interface.
Try to connect again.
You will see that no global address is configured.
No global address could be configured even though I can see in Wireshark that the the exchange of RS and RA is happening.
You can see that the RA is sent to L2 multicast address
33:33:00:00:00:1, which is the L2 multicast group which is joined when the APIgnrc_netif_ipv6_group_join_internal(netif,&ipv6_addr_all_nodes_link_local)is called. But this is only called once for every interface ingnrc_ipv6_nib_init_iface.The
atwinc15x0driver has an internal API to join a L2 multicast groupm2m_wifi_enable_mac_mcast()which is called whenNETOPT_L2_GROUPorNETOPT_L2_GROUP_LEAVEare sent to the driver.TLDR: The
netifreset is calling the driversinit()function again and I strongly assume thatm2m_wifi_init()makes the WiFi chip leave the L2 multicast group, which is why no RA toff02::1is received anymore. The fix in my opinion is, as you can see in the PR, to leaveipv6_addr_all_nodes_link_localwhen the interface is brought down and rejoin the group when it is brought up.Repeat the testing procedure with this fix and an
atwinc15x0and you will see that the RA is received and a global address is configured successfully.Issues/PRs references