Add Yamux experimental support (#5080)

beacon_chain/conf.nim

@@ -305,6 +305,12 @@ type
         defaultValue: false
         name: "enr-auto-update" .}: bool
 
+      enableYamux* {.
+        hidden
+        desc: "Enable the Yamux multiplexer"
+        defaultValue: false
+        name: "enable-yamux" .}: bool
+
       weakSubjectivityCheckpoint* {.
         desc: "Weak subjectivity checkpoint in the format block_root:epoch_number"
         name: "weak-subjectivity-checkpoint" .}: Option[Checkpoint]

beacon_chain/conf_light_client.nim

@@ -102,6 +102,12 @@ type LightClientConf* = object
     defaultValue: false
     name: "enr-auto-update" .}: bool
 
+  enableYamux* {.
+    hidden
+    desc: "Enable the Yamux multiplexer"
+    defaultValue: false
+    name: "enable-yamux" .}: bool
+
   agentString* {.
     defaultValue: "nimbus",
     desc: "Node agent string which is used as identifier in network"

beacon_chain/networking/eth2_network.nim

@@ -2271,8 +2271,14 @@ func gossipId(
 proc newBeaconSwitch(config: BeaconNodeConf | LightClientConf,
                      seckey: PrivateKey, address: MultiAddress,
                      rng: ref HmacDrbgContext): Switch {.raises: [Defect, CatchableError].} =
-  SwitchBuilder
-    .new()
+  var sb =
+    if config.enableYamux:
+      SwitchBuilder.new().withYamux()
+    else:
+      SwitchBuilder.new()
+  # Order of multiplexers matters, the first will be default
+
+  sb
     .withPrivateKey(seckey)
     .withAddress(address)
     .withRng(rng)