Use ReusePort when starting

libp2p/transports/tcptransport.nim

@@ -49,6 +49,8 @@ type
     opened*: uint64
     closed*: uint64
 
+  TcpTransportError* = object of transport.TransportError
+
 proc setupTcpTransportTracker(): TcpTransportTracker {.gcsafe, raises: [Defect].}
 
 proc getTcpTransportTracker(): TcpTransportTracker {.gcsafe.} =
@@ -157,6 +159,17 @@ method start*(
     warn "TCP transport already running"
     return
 
+  proc getPort(ma: MultiAddress): seq[byte] =
+    return ma[1].get().protoArgument().get()
+
+  proc isNotZeroPort(port: seq[byte]): bool =
+    return port != @[0.byte, 0]
+
+  let supported = addrs.filterIt(self.handles(it))
+  let nonZeroPorts = supported.mapIt(getPort(it)).filterIt(isNotZeroPort(it))
+  if deduplicate(nonZeroPorts).len < nonZeroPorts.len:
+    raise newException(TcpTransportError, "Duplicate ports detected")
+
   await procCall Transport(self).start(addrs)
   trace "Starting TCP transport"
   inc getTcpTransportTracker().opened
@@ -166,8 +179,7 @@ method start*(
       trace "Invalid address detected, skipping!", address = ma
       continue
 
-    if self.networkReachability == NetworkReachability.NotReachable:
-      self.flags.incl(ServerFlags.ReusePort)
+    self.flags.incl(ServerFlags.ReusePort)
     let server = createStreamServer(
       ma = ma,
       flags = self.flags,

tests/testtcptransport.nim

@@ -125,6 +125,25 @@ suite "TCP transport":
     server.close()
     await server.join()
 
+  asyncTest "Starting with duplicate ports must fail":
+    # Starting with duplicate addresses must fail
+    let ma = @[MultiAddress.init("/ip4/0.0.0.0/tcp/8080").tryGet(),
+               MultiAddress.init("/ip4/0.0.0.0/tcp/8080").tryGet()]
+
+    let transport: TcpTransport = TcpTransport.new(upgrade = Upgrade())
+
+    expect TcpTransportError:
+      await transport.start(ma)
+
+  asyncTest "Starting with duplicate but zero ports addresses must NOT fail":
+    let ma = @[MultiAddress.init("/ip4/0.0.0.0/tcp/0").tryGet(),
+               MultiAddress.init("/ip4/0.0.0.0/tcp/0").tryGet()]
+
+    let transport: TcpTransport = TcpTransport.new(upgrade = Upgrade())
+
+    await transport.start(ma)
+    await transport.stop()
+
   proc transProvider(): Transport = TcpTransport.new(upgrade = Upgrade())
 
   commonTransportTest(