> 2025-10-13T18:41:44.211218-03:00 adm-gw1 ctdbd[479406]: Node became HEALTHY. Ask recovery master to reallocate IPs
> 2025-10-13T18:41:44.732792-03:00 adm-gw1 ctdb-recoverd[479490]: Unassigned IP 192.168.45.235 can be served by this node
> 2025-10-13T18:41:44.732964-03:00 adm-gw1 ctdb-recoverd[479490]: IP 192.168.45.235 incorrectly on an interface    

The IP address isn't assigned to this node, but ctdbd uses bind(2) to check if the IP address is local (assuming ip_nonlocal_bind=0) and it can bind, so (considering the assumption) the address must be local.

> 2025-10-13T18:41:44.732987-03:00 adm-gw1 ctdb-recoverd[479490]: Trigger takeoverrun
> 2025-10-13T18:41:44.733160-03:00 adm-gw1 ctdb-recoverd[479490]: Takeover run starting
> 2025-10-13T18:41:44.769369-03:00 adm-gw1 ctdbd[479406]: ../../ctdb/server/ctdb_takeover.c:797 Doing updateip for IP 192.168.45.235 already on an interface
> 2025-10-13T18:41:44.769448-03:00 adm-gw1 ctdbd[479406]: Update of IP 192.168.45.235/16 from interface __none__ to ens18    

ctdbd decides that since the address is local, it has to do an "updateip" instead of a "takeip" to make the intended change.

> 2025-10-13T18:41:44.788619-03:00 adm-gw1 ctdb-eventd[479407]: 10.interface: ERROR: Unable to determine interface for IP 192.168.45.235
> 2025-10-13T18:41:44.788689-03:00 adm-gw1 ctdb-eventd[479407]: updateip event failed
> 2025-10-13T18:41:44.788847-03:00 adm-gw1 ctdbd[479406]: Failed update of IP 192.168.45.235 from interface __none__ to ens18    

However, the 10.interface event script can't find an interface with the IP address assigned, so it fails.

> 2025-10-13T18:41:44.788945-03:00 adm-gw1 ctdbd[479406]: ===============================================================
> 2025-10-13T18:41:44.788966-03:00 adm-gw1 ctdbd[479406]: INTERNAL ERROR: Signal 11: Segmentation fault in  () () pid 479406 (4.21.3)
> 2025-10-13T18:41:44.788985-03:00 adm-gw1 ctdbd[479406]: If you are running a recent Samba version, and if you think this problem is not yet 
> fixed in the latest versions, please consider reporting this bug, see 
> https://wiki.samba.org/index.php/Bug_Reporting
> 2025-10-13T18:41:44.789003-03:00 adm-gw1 ctdbd[479406]: ===============================================================
> 2025-10-13T18:41:44.789016-03:00 adm-gw1 ctdbd[479406]: PANIC (pid 479406): Signal 11: Segmentation fault in 4.21.3
> 2025-10-13T18:41:44.789489-03:00 adm-gw1 ctdbd[479406]: BACKTRACE: 21 stack frames:    

The stack trace isn't useful but, at a guess, it crashes here:

		/*
		 * All we can do is reset the old interface
		 * and let the next run fix it
		 */
		ctdb_vnn_unassign_iface(ctdb, state->vnn);
		state->vnn->iface = state->old;
		state->vnn->iface->references++;

This is because state->old is NULL.

That bug is still there in subsequent versions.  However, it should no longer happen on Linux (and possibly other platforms) in CTDB >= 4.22 because the check for an IP address no longer (only) depends on bind(2).

A fix is required in ctdb_do_updateip_callback().  However, this would almost certainly result in ctdbd repeatedly trying the failed updateip and banning the node involved.  So, a workaround should also be applied to 10.interface.script.