use only ready peers as sync source

Sync messages now carries a ready flag, telling whether the sending peer
itself is joined or is itself still (re-)joining.  In the latter case,
the peer won't be used as sync source.

1 files changed, 4 insertions, 0 deletions

diff --git a/src/transport/mod.rs b/src/transport/mod.rs
index 69d9e70..eeba47f 100644
--- a/src/transport/mod.rs
+++ b/src/transport/mod.rs
@@ -62,6 +62,10 @@ pub struct SyncEnvelope {
     /// Epoch of the document the message was generated from.
     pub epoch: Epoch,
     pub message: Message,
+    /// The sender was ready when it generated the message: its document is the swarm's,
+    /// not one it is still filling (joining, rejoining). Only such a peer can tell a
+    /// catching-up node that it has everything; an empty document says nothing else.
+    pub ready: bool,
 }
 
 /// A message serialized for the wire. Cloning is cheap (shared buffer).