It's just a sha256_double, but importantly when we convert it to a
string (in type_to_string, which is used in logging) we use
bitcoin_txid_to_hex() so it's reversed as people expect.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
When gossipd sends a message, have a gossip_index. When it gets back a
peer, the current gossip_index is included, so it can know exactly where
it's up to.
Most of this is mechanical plumbing through openingd, channeld and closingd,
even though openingd and closingd don't (currently) read gossip, so their
gossip_index will be unchanged.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This change is really to allow us to have a --dev-fail-on-subdaemon-fail option
so we can handle failures from subdaemons generically.
It also neatens handling so we can have an explicit callback for "peer
did something wrong" (which matters if we want to close the channel in
that case).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>