Servicing interfaces that are created ad-hoc (L2TP multitap)

[mweinelt]

With fastd's L2TP multitap feature (coming in Gluon 2022.1) we're seeing one interface per L2TP peer and I don't see a way for mesh-announce to work on links that are created in an ad-hoc fashion.

I think we need to brainstorm a way for mesh-announce to work on these kinds of links in multidomain setups.

[kaechele]

The way we deal with this when using Tunneldigger is to stick all the L2TP interfaces in a bridge (that has forwarding between bridge ports disabled using ebtables/nftables, so nodes don't think they are connected to each other directly) and put mesh-announce on that bridge. That bridge is then attached to the batman interface.

[kaechele]

Just switched some of our gateways to fastd with multitap and the same approach works there as well. It's pretty much a drop in replacement for Tunneldigger at that point.

[mweinelt]

I recommend using bridge set dev <brport> isolated on instead of using ebt/nft, should be more lightweight and this is what I used in our setup.

[kaechele]

Neat! I did not know this. Thanks!

[jplitza]

Since this seems to be resolved, I'm closing the issue. Feel free to re-open if you see the need for a solution inside mesh-announce.