add links messages

Introduce two new wire messages, LINKS and LINKS_REPLY (swarm::links).
A member answers with its links: for each peer, the transport, whether
it’s relayed, the RTT, and whether it’s dormant.  It answers members
only, at most every 5 s.  This bumps wire::VERSION to 7.  Every build
answers, with or without the feature, so every node needs this patch
before the map shows anything beyond its own node.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/transport/traffic.rs b/src/transport/traffic.rs
index b237db2..f8ca586 100644
--- a/src/transport/traffic.rs
+++ b/src/transport/traffic.rs
@@ -45,6 +45,8 @@ pub(crate) struct ByKind {
     pub(crate) identity: Counter,
     /// PING and PONG (`transport::paths`), counted by the paths layer under the address.
     pub(crate) paths: Counter,
+    /// LINKS and LINKS_REPLY (`swarm::links`).
+    pub(crate) links: Counter,
 }
 
 impl ByKind {
@@ -58,6 +60,7 @@ impl ByKind {
             MessageKind::Blob => &mut self.blob,
             MessageKind::Who | MessageKind::Me => &mut self.identity,
             MessageKind::Ping | MessageKind::Pong => &mut self.paths,
+            MessageKind::Links | MessageKind::LinksReply => &mut self.links,
         }
     }
 }