[net/libp2p] Use raw Identify observed addresses to discover extern…

…al addresses (#7338)

Instead of using libp2p-provided external address candidates,
susceptible to address translation issues, use litep2p-backend approach
based on confirming addresses observed by multiple peers as external.

Fixes #7207.

---------

Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com>

prdoc/pr_7338.prdoc

@@ -0,0 +1,10 @@
+title: '[net/libp2p] Use raw `Identify` observed addresses to discover external addresses'
+doc:
+- audience: Node Dev
+  description: |-
+    Instead of using libp2p-provided external address candidates, susceptible to address translation issues, use litep2p-backend approach based on confirming addresses observed by multiple peers as external.
+
+    Fixes https://github.com/paritytech/polkadot-sdk/issues/7207.
+crates:
+- name: sc-network
+  bump: major

substrate/client/network/src/behaviour.rs

@@ -184,6 +184,7 @@ impl<B: BlockT> Behaviour<B> {
 		request_response_protocols: Vec<ProtocolConfig>,
 		peer_store_handle: Arc<dyn PeerStoreProvider>,
 		external_addresses: Arc<Mutex<HashSet<Multiaddr>>>,
+		public_addresses: Vec<Multiaddr>,
 		connection_limits: ConnectionLimits,
 	) -> Result<Self, request_responses::RegisterError> {
 		Ok(Self {
@@ -192,6 +193,7 @@ impl<B: BlockT> Behaviour<B> {
 				user_agent,
 				local_public_key,
 				external_addresses,
+				public_addresses,
 			),
 			discovery: disco_config.finish(),
 			request_responses: request_responses::RequestResponsesBehaviour::new(

substrate/client/network/src/lib.rs

@@ -291,6 +291,9 @@ pub use service::{
 };
 pub use types::ProtocolName;
 
+/// Log target for `sc-network`.
+const LOG_TARGET: &str = "sub-libp2p";
+
 /// The maximum allowed number of established connections per peer.
 ///
 /// Typically, and by design of the network behaviours in this crate,

substrate/client/network/src/litep2p/discovery.rs

@@ -50,6 +50,7 @@ use schnellru::{ByLength, LruMap};
 use std::{
 	cmp,
 	collections::{HashMap, HashSet, VecDeque},
+	iter,
 	num::NonZeroUsize,
 	pin::Pin,
 	sync::Arc,
@@ -72,11 +73,9 @@ const GET_RECORD_REDUNDANCY_FACTOR: usize = 4;
 /// The maximum number of tracked external addresses we allow.
 const MAX_EXTERNAL_ADDRESSES: u32 = 32;
 
-/// Minimum number of confirmations received before an address is verified.
-///
-/// Note: all addresses are confirmed by libp2p on the first encounter. This aims to make
-/// addresses a bit more robust.
-const MIN_ADDRESS_CONFIRMATIONS: usize = 2;
+/// Number of times observed address is received from different peers before it is confirmed as
+/// external.
+const MIN_ADDRESS_CONFIRMATIONS: usize = 3;
 
 /// Discovery events.
 #[derive(Debug)]
@@ -509,7 +508,7 @@ impl Discovery {
 					.flatten()
 					.flatten();
 
-				self.address_confirmations.insert(address.clone(), Default::default());
+				self.address_confirmations.insert(address.clone(), iter::once(peer).collect());
 
 				return (false, oldest)
 			},