feat: allow DNS names in peers/seeds list and resolve them (#3125)

* feat: allow DNS names in peers/seeds list and resolve them

* tests: add mod for peer tests

* refactor: rename some variables

* chore: use Serde desrialize to resolve DNS names into PeerAddrs

* fix: compile

* fix: add back code to remove duplicate ip addresses from resolved DNS seeds

config/src/comments.rs

@@ -260,6 +260,7 @@ fn comments() -> HashMap<String, String> {
 	retval.insert(
 		"seeding_type".to_string(),
 		"
+#All seeds/peers can be either IP address or DNS names. Port number must always be specified
 #how to seed this server, can be None, List or DNSSeed
 "
 		.to_string(),

p2p/src/msg.rs

@@ -466,7 +466,7 @@ impl Readable for GetPeerAddrs {
 
 /// Peer addresses we know of that are fresh enough, in response to
 /// GetPeerAddrs.
-#[derive(Debug)]
+#[derive(Debug, Clone, Serialize, PartialEq)]
 pub struct PeerAddrs {
 	pub peers: Vec<PeerAddr>,
 }
@@ -493,7 +493,7 @@ impl Readable for PeerAddrs {
 		for _ in 0..peer_count {
 			peers.push(PeerAddr::read(reader)?);
 		}
-		Ok(PeerAddrs { peers: peers })
+		Ok(PeerAddrs { peers })
 	}
 }
 

p2p/src/peer.rs

@@ -152,7 +152,7 @@ impl Peer {
 
 	pub fn is_denied(config: &P2PConfig, peer_addr: PeerAddr) -> bool {
 		if let Some(ref denied) = config.peers_deny {
-			if denied.contains(&peer_addr) {
+			if denied.peers.contains(&peer_addr) {
 				debug!(
 					"checking peer allowed/denied: {:?} explicitly denied",
 					peer_addr
@@ -161,7 +161,7 @@ impl Peer {
 			}
 		}
 		if let Some(ref allowed) = config.peers_allow {
-			if allowed.contains(&peer_addr) {
+			if allowed.peers.contains(&peer_addr) {
 				debug!(
 					"checking peer allowed/denied: {:?} explicitly allowed",
 					peer_addr

p2p/src/types.rs

@@ -12,15 +12,20 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use crate::util::RwLock;
 use std::convert::From;
+use std::fmt;
 use std::fs::File;
 use std::io::{self, Read};
-use std::net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr, SocketAddrV4, SocketAddrV6};
+use std::net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr, SocketAddrV4, SocketAddrV6, ToSocketAddrs};
 use std::path::PathBuf;
+use std::str::FromStr;
 use std::sync::Arc;
 
 use chrono::prelude::*;
+use serde::de::{SeqAccess, Visitor};
+use serde::{Deserialize, Deserializer};
+
+use grin_store;
 
 use crate::chain;
 use crate::core::core;
@@ -28,7 +33,8 @@ use crate::core::core::hash::Hash;
 use crate::core::global;
 use crate::core::pow::Difficulty;
 use crate::core::ser::{self, ProtocolVersion, Readable, Reader, Writeable, Writer};
-use grin_store;
+use crate::msg::PeerAddrs;
+use crate::util::RwLock;
 
 /// Maximum number of block headers a peer should ever send
 pub const MAX_BLOCK_HEADERS: u32 = 512;
@@ -156,6 +162,45 @@ impl Readable for PeerAddr {
 	}
 }
 
+impl<'de> Visitor<'de> for PeerAddrs {
+	type Value = PeerAddrs;
+
+	fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+		formatter.write_str("an array of dns names or IP addresses")
+	}
+
+	fn visit_seq<M>(self, mut access: M) -> Result<Self::Value, M::Error>
+	where
+		M: SeqAccess<'de>,
+	{
+		let mut peers = Vec::with_capacity(access.size_hint().unwrap_or(0));
+
+		while let Some(entry) = access.next_element::<&str>()? {
+			match SocketAddr::from_str(entry) {
+				// Try to parse IP address first
+				Ok(ip) => peers.push(PeerAddr(ip)),
+				// If that fails it's probably a DNS record
+				Err(_) => {
+					let socket_addrs = entry
+						.to_socket_addrs()
+						.expect(format!("Unable to resolve DNS: {}", entry).as_str());
+					peers.append(&mut socket_addrs.map(|addr| PeerAddr(addr)).collect());
+				}
+			}
+		}
+		Ok(PeerAddrs { peers })
+	}
+}
+
+impl<'de> Deserialize<'de> for PeerAddrs {
+	fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+	where
+		D: Deserializer<'de>,
+	{
+		deserializer.deserialize_seq(PeerAddrs { peers: vec![] })
+	}
+}
+
 impl std::hash::Hash for PeerAddr {
 	/// If loopback address then we care about ip and port.
 	/// If regular address then we only care about the ip and ignore the port.
@@ -218,18 +263,18 @@ pub struct P2PConfig {
 	pub seeding_type: Seeding,
 
 	/// The list of seed nodes, if using Seeding as a seed type
-	pub seeds: Option<Vec<PeerAddr>>,
+	pub seeds: Option<PeerAddrs>,
 
 	/// Capabilities expose by this node, also conditions which other peers this
 	/// node will have an affinity toward when connection.
 	pub capabilities: Capabilities,
 
-	pub peers_allow: Option<Vec<PeerAddr>>,
+	pub peers_allow: Option<PeerAddrs>,
 
-	pub peers_deny: Option<Vec<PeerAddr>>,
+	pub peers_deny: Option<PeerAddrs>,
 
 	/// The list of preferred peers that we will try to connect to
-	pub peers_preferred: Option<Vec<PeerAddr>>,
+	pub peers_preferred: Option<PeerAddrs>,
 
 	pub ban_window: Option<i64>,
 
@@ -316,7 +361,7 @@ impl P2PConfig {
 pub enum Seeding {
 	/// No seeding, mostly for tests that programmatically connect
 	None,
-	/// A list of seed addresses provided to the server
+	/// A list of seeds provided to the server (can be addresses or DNS names)
 	List,
 	/// Automatically get a list of seeds from multiple DNS
 	DNSSeed,

servers/src/grin/seed.rs

@@ -361,35 +361,47 @@ fn listen_for_addrs(
 	}
 }
 
-pub fn dns_seeds() -> Box<dyn Fn() -> Vec<PeerAddr> + Send> {
+pub fn default_dns_seeds() -> Box<dyn Fn() -> Vec<PeerAddr> + Send> {
 	Box::new(|| {
-		let mut addresses: Vec<PeerAddr> = vec![];
 		let net_seeds = if global::is_floonet() {
 			FLOONET_DNS_SEEDS
 		} else {
 			MAINNET_DNS_SEEDS
 		};
-		for dns_seed in net_seeds {
+		resolve_dns_to_addrs(
-			let temp_addresses = addresses.clone();
+			&net_seeds
-			debug!("Retrieving seed nodes from dns {}", dns_seed);
+				.iter()
-			match (dns_seed.to_owned(), 0).to_socket_addrs() {
+				.map(|s| {
-				Ok(addrs) => addresses.append(
+					s.to_string()
-					&mut (addrs
+						+ if global::is_floonet() {
-						.map(|mut addr| {
+							":13414"
-							addr.set_port(if global::is_floonet() { 13414 } else { 3414 });
+						} else {
-							PeerAddr(addr)
+							":3414"
-						})
+						}
-						.filter(|addr| !temp_addresses.contains(addr))
+				})
-						.collect()),
+				.collect(),
-				),
+		)
-				Err(e) => debug!("Failed to resolve seed {:?} got error {:?}", dns_seed, e),
-			}
-		}
-		debug!("Retrieved seed addresses: {:?}", addresses);
-		addresses
 	})
 }
 
+fn resolve_dns_to_addrs(dns_records: &Vec<String>) -> Vec<PeerAddr> {
+	let mut addresses: Vec<PeerAddr> = vec![];
+	for dns in dns_records {
+		debug!("Retrieving addresses from dns {}", dns);
+		match dns.to_socket_addrs() {
+			Ok(addrs) => addresses.append(
+				&mut addrs
+					.map(|addr| PeerAddr(addr))
+					.filter(|addr| !addresses.contains(addr))
+					.collect(),
+			),
+			Err(e) => debug!("Failed to resolve dns {:?} got error {:?}", dns, e),
+		};
+	}
+	debug!("Resolved addresses: {:?}", addresses);
+	addresses
+}
+
 /// Convenience function when the seed list is immediately known. Mostly used
 /// for tests.
 pub fn predefined_seeds(addrs: Vec<PeerAddr>) -> Box<dyn Fn() -> Vec<PeerAddr> + Send> {

servers/src/grin/server.rs

@@ -231,22 +231,24 @@ impl Server {
 					seed::predefined_seeds(vec![])
 				}
 				p2p::Seeding::List => match &config.p2p_config.seeds {
-					Some(seeds) => seed::predefined_seeds(seeds.clone()),
+					Some(seeds) => seed::predefined_seeds(seeds.peers.clone()),
 					None => {
 						return Err(Error::Configuration(
 							"Seeds must be configured for seeding type List".to_owned(),
 						));
 					}
 				},
-				p2p::Seeding::DNSSeed => seed::dns_seeds(),
+				p2p::Seeding::DNSSeed => seed::default_dns_seeds(),
 				_ => unreachable!(),
 			};
 
+			let preferred_peers = config.p2p_config.peers_preferred.clone().map(|p| p.peers);
+
 			connect_thread = Some(seed::connect_and_monitor(
 				p2p_server.clone(),
 				config.p2p_config.capabilities,
 				seeder,
-				config.p2p_config.peers_preferred.clone(),
+				preferred_peers,
 				stop_state.clone(),
 			)?);
 		}

src/bin/cmd/server.rs

@@ -24,9 +24,11 @@ use ctrlc;
 
 use crate::config::GlobalConfig;
 use crate::core::global;
-use crate::p2p::{PeerAddr, Seeding};
+use crate::p2p::Seeding;
 use crate::servers;
 use crate::tui::ui;
+use grin_p2p::msg::PeerAddrs;
+use grin_p2p::PeerAddr;
 use grin_util::logger::LogEntry;
 use std::sync::mpsc;
 
@@ -119,12 +121,12 @@ pub fn server_command(
 		}
 
 		if let Some(seeds) = a.values_of("seed") {
-			let seed_addrs = seeds
+			let peers = seeds
-				.filter_map(|x| x.parse().ok())
+				.filter_map(|s| s.parse().ok())
-				.map(|x| PeerAddr(x))
+				.map(|sa| PeerAddr(sa))
 				.collect();
 			server_config.p2p_config.seeding_type = Seeding::List;
-			server_config.p2p_config.seeds = Some(seed_addrs);
+			server_config.p2p_config.seeds = Some(PeerAddrs { peers });
 		}
 	}