I was going to deploy this today. But minutes before I would have tried, someone posted on the bird-users mailing list about add-paths causing sessions with IOS-XR 7.9.2 to shut down.
My current plan is to postpone this a week to see if there are
any replies on that thread. Unfortunately, I've found the bird
mailing lists to be pretty quiet. If nothing changes, then I will
attempt this. I was already planning to keep track of which
sessions were up before and compare after. Based on what happens,
I can revert if needed. It's only one route server, so if
someone's session goes down, it's not the end of the world.
If you are concerned about this (e.g. you run IOS-XR), another
option is that you could pre-emptively disable support for
add-paths on your end.
-- Richard