BIP144: Handshake and relay (receiver side)

Service bit logic by Nicolas Dorier.

Only download blocks from witness peers after fork.

src/init.cpp

@@ -1377,6 +1377,18 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
         }
     }
 
+    if (Params().GetConsensus().vDeployments[Consensus::DEPLOYMENT_SEGWIT].nTimeout != 0) {
+        // Only advertize witness capabilities if they have a reasonable start time.
+        // This allows us to have the code merged without a defined softfork, by setting its
+        // end time to 0.
+        // Note that setting NODE_WITNESS is never required: the only downside from not
+        // doing so is that after activation, no upgraded nodes will fetch from you.
+        nLocalServices = ServiceFlags(nLocalServices | NODE_WITNESS);
+        // Only care about others providing witness capabilities if there is a softfork
+        // defined.
+        nRelevantServices = ServiceFlags(nRelevantServices | NODE_WITNESS);
+    }
+
     // ********************************************************* Step 10: import blocks
 
     if (mapArgs.count("-blocknotify"))