Improve rtr client version negotiation.

src/rtr/client.rs

@@ -22,6 +22,13 @@
 
 const IO_TIMEOUT: Duration = Duration::from_secs(10);
 
+/// The protocol version we initially propose.
+///
+/// While the client technically supports version 2 as well, the format of the
+/// ASPA PDU has not yet been agreed upon. Rather than possibly deploying
+/// broken servers, we only start with version 1 for now.
+const INITIAL_VERSION: u8 = 1;
+
 
 //------------ PayloadTarget -------------------------------------------------
 
@@ -191,7 +198,7 @@
 
     /// Returns the protocol version to use.
     fn version(&self) -> u8 {
-        self.version.unwrap_or(1)
+        self.version.unwrap_or(INITIAL_VERSION)
     }
 }
 
@@ -426,6 +433,15 @@
                 Ok(())
             }
         }
+        else if version > INITIAL_VERSION {
+            Err(io::Error::new(
+                io::ErrorKind::InvalidData,
+                format!(
+                    "server requested unsupported protocol version {}",
+                    version
+                )
+            ))
+        }
         else {
             self.version = Some(version);
             Ok(())
@@ -442,7 +458,7 @@
     Response(pdu::CacheResponse),
 
     /// A reset response. We need to retry with a reset query.
     Reset(pdu::CacheReset),
 }
 
 impl FirstReply {

src/rtr/server.rs

@@ -25,7 +25,11 @@ use super::state::State;
 /// The maximum protocol version we support.
 ///
 /// We support all protocol versions from 0 up to and including this value.
-const MAX_VERSION: u8 = 2;
+///
+/// While the server technically supports version 2 as well, the format of the
+/// ASPA PDU has not yet been agreed upon. Rather than possibly deploying
+/// broken servers, we only announce support for version 0 or 1 for now.
+const MAX_VERSION: u8 = 1;
 
 //============ Traits ========================================================