There are several reports of desynchronization with LND here; a simple
approach is to only have one feerate change in flight at any time.
Even if this turns out to be our fault, it's been a historic area of
confusion, so this restriction seems reasonable.
Changelog-Fixed: Protocol: Don't create more than one feerate change at a time, as this seems to desync with LND.
Fixes: #4152
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Previously we've used the term 'funder' to refer to the peer
paying the fees for a transaction; v2 of openchannel will make
this no longer true. Instead we rename this to 'opener', or the
peer sending the 'open_channel' message, since this will be universally
true in a dual-funding world.
This uses the same state machine as HTLCs, but they're only
ever added, not removed. Since we can only have one in each
state, we use a simple array; mostly NULL.
We could make this more space-efficient by folding everything into the
first 5 states, but that would be more complex than just using the
identical state machine.
One subtlety: we don't send uncommitted fee_states over the wire.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
