From 6a6cb07c22b2eddb3950b3efab0e9cb737c17b63 Mon Sep 17 00:00:00 2001
From: James Phillips <slackpad@gmail.com>
Date: Mon, 1 Aug 2016 10:25:15 -0700
Subject: [PATCH] Refactors to checkRPCHeader.

---
 raft.go | 33 ++++++++++++++++++---------------
 1 file changed, 18 insertions(+), 15 deletions(-)

diff --git a/raft.go b/raft.go
index 773dea5bb..06a40d849 100644
--- a/raft.go
+++ b/raft.go
@@ -29,14 +29,21 @@ func (r *Raft) getRPCHeader() RPCHeader {
 	}
 }
 
-// dispositionRPC houses logic about whether this instance of Raft can process
-// an RPC message with the given header.
-func (r *Raft) dispositionRPC(header RPCHeader) bool {
+// checkRPCHeader houses logic about whether this instance of Raft can process
+// the given RPC message.
+func (r *Raft) checkRPCHeader(rpc RPC) error {
+	// Get the header off the RPC message.
+	wh, ok := rpc.Command.(WithRPCHeader)
+	if !ok {
+		return fmt.Errorf("RPC does not have a header")
+	}
+	header := wh.GetRPCHeader()
+
 	// First check is to just make sure the code can understand the
 	// protocol at all.
 	if header.ProtocolVersion < ProtocolVersionMin ||
 		header.ProtocolVersion > ProtocolVersionMax {
-		return false
+		return ErrUnsupportedProtocol
 	}
 
 	// Second check is whether we should support this message, given the
@@ -45,7 +52,11 @@ func (r *Raft) dispositionRPC(header RPCHeader) bool {
 	// currently what we want, and in general support one version back. We
 	// may need to revisit this policy depending on how future protocol
 	// changes evolve.
-	return header.ProtocolVersion >= r.conf.ProtocolVersion-1
+	if header.ProtocolVersion < r.conf.ProtocolVersion-1 {
+		return ErrUnsupportedProtocol
+	}
+
+	return nil
 }
 
 // commitTuple is used to send an index that was committed,
@@ -798,16 +809,8 @@ func (r *Raft) processLog(l *Log, future *logFuture) {
 // processRPC is called to handle an incoming RPC request. This must only be
 // called from the main thread.
 func (r *Raft) processRPC(rpc RPC) {
-	if wh, ok := rpc.Command.(WithRPCHeader); ok {
-		if ok := r.dispositionRPC(wh.GetRPCHeader()); !ok {
-			r.logger.Printf("[ERR] raft: Ignoring unsupported RPC %#v for command: %#v", wh, rpc.Command)
-			rpc.Respond(nil, ErrUnsupportedProtocol)
-			return
-		}
-
-	} else {
-		r.logger.Printf("[ERR] raft: Ignoring un-versioned command: %#v", rpc.Command)
-		rpc.Respond(nil, fmt.Errorf("unversioned command"))
+	if err := r.checkRPCHeader(rpc); err != nil {
+		rpc.Respond(nil, err)
 		return
 	}