net: Strip previous p2p prefix before concatenating addresses (#11078)

This PR ensures that a `MultiaddrWithPeerId` will always remain valid
after a concatenating process.

The litep2p code will concatanate the provided multiaddr-with-peerID
regardless if the address already contains a `p2p/..` prefix:

https://github.com/paritytech/polkadot-sdk/blob/e85be1c07adedcc86554affa4f6af536c4a2efc1/substrate/client/network/src/litep2p/service.rs#L427-L434

This then can lead to addresses for reserved peers to never be dialed by
the network backend as they are considered invalid.

This has been discovered by running the networking benchmarks:

https://github.com/paritytech/polkadot-sdk/blob/e85be1c07adedcc86554affa4f6af536c4a2efc1/substrate/client/network/benches/notifications_protocol.rs#L143-L148

Part of the cleanups for:
- #10425

---------

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>
Co-authored-by: Bastian Köcher <git@kchr.de>
Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com>
(cherry picked from commit e30a412)

Author: 3 people

prdoc/pr_11078.prdoc

@@ -0,0 +1,21 @@
+title: 'net: Strip previous p2p prefix before concatenating addresses'
+doc:
+- audience: Node Dev
+  description: |-
+    This PR ensures that a `MultiaddrWithPeerId` will always remain valid after a concatenating process.
+
+    The litep2p code will concatanate the provided multiaddr-with-peerID regardless if the address already contains a `p2p/..` prefix:
+
+    https://github.com/paritytech/polkadot-sdk/blob/e85be1c07adedcc86554affa4f6af536c4a2efc1/substrate/client/network/src/litep2p/service.rs#L427-L434
+
+
+    This then can lead to addresses for reserved peers to never be dialed by the network backend as they are considered invalid.
+
+    This has been discovered by running the networking benchmarks:
+    https://github.com/paritytech/polkadot-sdk/blob/e85be1c07adedcc86554affa4f6af536c4a2efc1/substrate/client/network/benches/notifications_protocol.rs#L143-L148
+
+    Part of the cleanups for:
+    - https://github.com/paritytech/polkadot-sdk/issues/10425
+crates:
+- name: sc-network
+  bump: patch

substrate/client/network/src/config.rs

@@ -170,8 +170,12 @@ pub struct MultiaddrWithPeerId {
 impl MultiaddrWithPeerId {
 	/// Concatenates the multiaddress and peer ID into one multiaddress containing both.
 	pub fn concat(&self) -> Multiaddr {
-		let proto = multiaddr::Protocol::P2p(From::from(self.peer_id));
-		self.multiaddr.clone().with(proto)
+		let mut addr = self.multiaddr.clone();
+		// Ensure that the address not already contains the `p2p` protocol.
+		if matches!(addr.iter().last(), Some(multiaddr::Protocol::P2p(_))) {
+			addr.pop();
+		}
+		addr.with(multiaddr::Protocol::P2p(From::from(self.peer_id)))
 	}
 }