ndb: make non-unique FDB index more unique

[pkulev]

I found out that brmsg_schema has unique index on (ifindex, lladdr, vlan), so that gives an answer to me what happend in the linked issue.

There can be multicast FDBs with single ifindex and no NDA_VLAN at all (that means NDA_VLAN = 0), but NDA_DST will be different.

We can clearly see that in the example from the issue:

~# bridge fdb show | grep 00:00:00:00:00:00
00:00:00:00:00:00 dev vxln7 dst 10.1.0.107 self extern_learn permanent
00:00:00:00:00:00 dev vxln7 dst 10.1.0.11 self extern_learn permanent

This change of index breaks backward compatibility for filters like this:

fdb = ndb.fdb.dump()
fdb.select_records(dst=lambda dst: dst is not None)
do_something_with(list(fdb))

Now it's more like identity check:

fdb.select_records(dst=lambda dst: dst)

Closes: #1091

[pkulev]

@svinota could you please review this PR and tell me what do you think about it?

[svinota]

Thanks, looking how to merge (a small change required, but I fix it)

[svinota]

Fixed, running CI locally. I will merge the the PR manually and update you here.

[svinota]

The PR uses NDA_DST which is empty in most cases, so I added a small fix that ignores empty NDA_DST when running IPRoute.fdb() and IPRoute.neigh().

[svinota]

Pls check if this will work for you.

[pkulev]

Thanks! I'll test changes tomorrow.

[pkulev]

@svinota, yep it worked well, thank you! Could you please make a new release version?

[svinota]

Sure thing, to be tagged tonight