Before this patch:
1. connectd says it's connected (peer_connected)
2. we tell connectd we want to talk about each channel (peer_make_active)
3. connectd gives us an fd for each channel, and we connect it to a subd (peer_active)
4. OR, connectd says it sent something about a channel we didn't tell it about, with an fd (peer_active)
Now:
1. connectd says it's connected (peer_connected)
2. we start all appropriate subds and tell connectd to what channels/fds (peer_connect_subd).
3. if connectd says it sent something about a channel we didn't tell it about, we either tell
it to hang up (peer_final_msg), or connect a new opening daemon (peer_connect_subd).
This is the minimal-size patch, which is why we create socket pairs in
so many places to use the existing functions. Many cleanups are
possible, since the new flow is so simple.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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