protocols/mdns: Add IPv6 support (#2161)

Signed-off-by: Emil Majchrzak <majchrzakemil@gitlab.com>

Co-authored-by: Emil Majchrzak <majchrzakemil@gitlab.com>
Co-authored-by: Max Inden <mail@max-inden.de>

protocols/mdns/CHANGELOG.md

@@ -2,6 +2,12 @@
 
 - Update dependencies.
 
+- Add support for IPv6. To enable set the multicast address
+  in `MdnsConfig` to `IPV6_MDNS_MULTICAST_ADDRESS`.
+  See [PR 2161] for details.
+  
+[PR 2161]: https://github.com/libp2p/rust-libp2p/pull/2161/
+
 # 0.31.0 [2021-07-12]
 
 - Update dependencies.

protocols/mdns/Cargo.toml

@@ -25,6 +25,6 @@ socket2 = { version = "0.4.0", features = ["all"] }
 void = "1.0.2"
 
 [dev-dependencies]
-async-std = "1.9.0"
+async-std = { version = "1.9.0", features = ["attributes"] }
-if-addrs = "0.6.5"
+libp2p = { path = "../.." }
-tokio = { version = "1.2.0", default-features = false, features = ["rt", "rt-multi-thread"] }
+tokio = { version = "1.2.0", default-features = false, features = ["macros", "rt", "rt-multi-thread"] }

protocols/mdns/src/behaviour.rs

@@ -18,12 +18,12 @@
 // FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 // DEALINGS IN THE SOFTWARE.
 
+use crate::IPV4_MDNS_MULTICAST_ADDRESS;
 use crate::dns::{build_query, build_query_response, build_service_discovery_response};
 use crate::query::MdnsPacket;
 use async_io::{Async, Timer};
 use futures::prelude::*;
 use if_watch::{IfEvent, IfWatcher};
-use lazy_static::lazy_static;
 use libp2p_core::connection::ListenerId;
 use libp2p_core::{
     address_translation, multiaddr::Protocol, Multiaddr, PeerId,
@@ -38,18 +38,13 @@ use std::{
     cmp,
     collections::VecDeque,
     fmt, io, iter,
-    net::{IpAddr, Ipv4Addr, SocketAddr, UdpSocket},
+    net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr, UdpSocket},
     pin::Pin,
     task::Context,
     task::Poll,
     time::{Duration, Instant},
 };
 
-lazy_static! {
-    static ref IPV4_MDNS_MULTICAST_ADDRESS: SocketAddr =
-        SocketAddr::from((Ipv4Addr::new(224, 0, 0, 251), 5353));
-}
-
 /// Configuration for mDNS.
 #[derive(Clone, Debug)]
 pub struct MdnsConfig {
@@ -61,6 +56,8 @@ pub struct MdnsConfig {
     /// peer joins the network. Receiving an mdns packet resets the timer
     /// preventing unnecessary traffic.
     pub query_interval: Duration,
+    /// IP address for multicast.
+    pub multicast_addr: IpAddr,
 }
 
 impl Default for MdnsConfig {
@@ -68,6 +65,7 @@ impl Default for MdnsConfig {
         Self {
             ttl: Duration::from_secs(6 * 60),
             query_interval: Duration::from_secs(5 * 60),
+            multicast_addr: *IPV4_MDNS_MULTICAST_ADDRESS,
         }
     }
 }
@@ -118,24 +116,42 @@ pub struct Mdns {
 
     /// Discovery timer.
     timeout: Timer,
+
+    // Multicast address.
+    multicast_addr: IpAddr,
 }
 
 impl Mdns {
     /// Builds a new `Mdns` behaviour.
     pub async fn new(config: MdnsConfig) -> io::Result<Self> {
-        let recv_socket = {
+        let recv_socket = match config.multicast_addr {
-            let socket = Socket::new(Domain::IPV4, Type::DGRAM, Some(socket2::Protocol::UDP))?;
+            IpAddr::V4(_) => {
-            socket.set_reuse_address(true)?;
+                let socket = Socket::new(Domain::IPV4, Type::DGRAM, Some(socket2::Protocol::UDP))?;
-            #[cfg(unix)]
+                socket.set_reuse_address(true)?;
-            socket.set_reuse_port(true)?;
+                #[cfg(unix)]
-            socket.bind(&SocketAddr::new(Ipv4Addr::UNSPECIFIED.into(), 5353).into())?;
+                socket.set_reuse_port(true)?;
-            let socket = UdpSocket::from(socket);
+                socket.bind(&SocketAddr::new(Ipv4Addr::UNSPECIFIED.into(), 5353).into())?;
-            socket.set_multicast_loop_v4(true)?;
+                socket.set_multicast_loop_v4(true)?;
-            socket.set_multicast_ttl_v4(255)?;
+                socket.set_multicast_ttl_v4(255)?;
-            Async::new(socket)?
+                Async::new(UdpSocket::from(socket))?
+            }
+            IpAddr::V6(_) => {
+                let socket = Socket::new(Domain::IPV6, Type::DGRAM, Some(socket2::Protocol::UDP))?;
+                socket.set_reuse_address(true)?;
+                #[cfg(unix)]
+                socket.set_reuse_port(true)?;
+                socket.bind(&SocketAddr::new(Ipv6Addr::UNSPECIFIED.into(), 5353).into())?;
+                socket.set_multicast_loop_v6(true)?;
+                Async::new(UdpSocket::from(socket))?
+            }
         };
         let send_socket = {
-            let socket = UdpSocket::bind((Ipv4Addr::UNSPECIFIED, 0))?;
+            let addrs = [
+                SocketAddr::new(IpAddr::V4(Ipv4Addr::UNSPECIFIED), 0),
+                SocketAddr::new(IpAddr::V6(Ipv6Addr::UNSPECIFIED), 0),
+            ];
+
+            let socket = std::net::UdpSocket::bind(&addrs[..])?;
             Async::new(socket)?
         };
         let if_watch = if_watch::IfWatcher::new().await?;
@@ -151,6 +167,7 @@ impl Mdns {
             query_interval: config.query_interval,
             ttl: config.ttl,
             timeout: Timer::interval(config.query_interval),
+            multicast_addr: config.multicast_addr,
         })
     }
 
@@ -279,20 +296,34 @@ impl NetworkBehaviour for Mdns {
         >,
     > {
         while let Poll::Ready(event) = Pin::new(&mut self.if_watch).poll(cx) {
-            let multicast = From::from([224, 0, 0, 251]);
             let socket = self.recv_socket.get_ref();
             match event {
                 Ok(IfEvent::Up(inet)) => {
                     if inet.addr().is_loopback() {
                         continue;
                     }
-                    if let IpAddr::V4(addr) = inet.addr() {
+                    match self.multicast_addr {
-                        log::trace!("joining multicast on iface {}", addr);
+                        IpAddr::V4(multicast) => {
-                        if let Err(err) = socket.join_multicast_v4(&multicast, &addr) {
+                            if let IpAddr::V4(addr) = inet.addr() {
-                            log::error!("join multicast failed: {}", err);
+                                log::trace!("joining multicast on iface {}", addr);
-                        } else {
+                                if let Err(err) = socket.join_multicast_v4(&multicast, &addr) {
-                            self.timeout
+                                    log::error!("join multicast failed: {}", err);
-                                .set_interval_at(Instant::now(), self.query_interval);
+                                } else {
+                                    self.timeout
+                                        .set_interval_at(Instant::now(), self.query_interval);
+                                }
+                            }
+                        }
+                        IpAddr::V6(multicast) => {
+                            if let IpAddr::V6(addr) = inet.addr() {
+                                log::trace!("joining multicast on iface {}", addr);
+                                if let Err(err) = socket.join_multicast_v6(&multicast, 0) {
+                                    log::error!("join multicast failed: {}", err);
+                                } else {
+                                    self.timeout
+                                        .set_interval_at(Instant::now(), self.query_interval);
+                                }
+                            }
                         }
                     }
                 }
@@ -300,10 +331,22 @@ impl NetworkBehaviour for Mdns {
                     if inet.addr().is_loopback() {
                         continue;
                     }
-                    if let IpAddr::V4(addr) = inet.addr() {
+                    match self.multicast_addr {
-                        log::trace!("leaving multicast on iface {}", addr);
+                        IpAddr::V4(multicast) => {
-                        if let Err(err) = socket.leave_multicast_v4(&multicast, &addr) {
+                            if let IpAddr::V4(addr) = inet.addr() {
-                            log::error!("leave multicast failed: {}", err);
+                                log::trace!("leaving multicast on iface {}", addr);
+                                if let Err(err) = socket.leave_multicast_v4(&multicast, &addr) {
+                                    log::error!("leave multicast failed: {}", err);
+                                }
+                            }
+                        }
+                        IpAddr::V6(multicast) => {
+                            if let IpAddr::V6(addr) = inet.addr() {
+                                log::trace!("leaving multicast on iface {}", addr);
+                                if let Err(err) = socket.leave_multicast_v6(&multicast, 0) {
+                                    log::error!("leave multicast failed: {}", err);
+                                }
+                            }
                         }
                     }
                 }
@@ -332,7 +375,7 @@ impl NetworkBehaviour for Mdns {
             if let Some(packet) = self.send_buffer.pop_front() {
                 match self
                     .send_socket
-                    .send_to(&packet, *IPV4_MDNS_MULTICAST_ADDRESS)
+                    .send_to(&packet, SocketAddr::new(self.multicast_addr, 5353))
                     .now_or_never()
                 {
                     Some(Ok(_)) => {}

protocols/mdns/src/dns.rs

@@ -417,9 +417,7 @@ mod tests {
 
     #[test]
     fn build_query_response_correct() {
-        let my_peer_id = identity::Keypair::generate_ed25519()
+        let my_peer_id = identity::Keypair::generate_ed25519().public().to_peer_id();
-            .public()
-            .to_peer_id();
         let addr1 = "/ip4/1.2.3.4/tcp/5000".parse().unwrap();
         let addr2 = "/ip6/::1/udp/10000".parse().unwrap();
         let packets = build_query_response(

protocols/mdns/src/lib.rs

@@ -29,12 +29,20 @@
 //! This crate provides the `Mdns` struct which implements the `NetworkBehaviour` trait. This
 //! struct will automatically discover other libp2p nodes on the local network.
 //!
+use lazy_static::lazy_static;
+use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
 
 /// The DNS service name for all libp2p peers used to query for addresses.
 const SERVICE_NAME: &[u8] = b"_p2p._udp.local";
 /// The meta query for looking up the `SERVICE_NAME`.
 const META_QUERY_SERVICE: &[u8] = b"_services._dns-sd._udp.local";
 
+lazy_static! {
+    pub static ref IPV4_MDNS_MULTICAST_ADDRESS: IpAddr = IpAddr::V4(Ipv4Addr::new(224, 0, 0, 251));
+    pub static ref IPV6_MDNS_MULTICAST_ADDRESS: IpAddr =
+        IpAddr::V6(Ipv6Addr::new(0xFF02, 0, 0, 0, 0, 0, 0, 0xFB));
+}
+
 pub use crate::behaviour::{Mdns, MdnsConfig, MdnsEvent};
 
 mod behaviour;

protocols/mdns/tests/smoke.rs

@@ -0,0 +1,101 @@
+// Copyright 2018 Parity Technologies (UK) Ltd.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the "Software"),
+// to deal in the Software without restriction, including without limitation
+// the rights to use, copy, modify, merge, publish, distribute, sublicense,
+// and/or sell copies of the Software, and to permit persons to whom the
+// Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.use futures::StreamExt;
+
+use futures::StreamExt;
+use libp2p::{
+    identity,
+    mdns::{Mdns, MdnsConfig, MdnsEvent, IPV6_MDNS_MULTICAST_ADDRESS},
+    swarm::{Swarm, SwarmEvent},
+    PeerId,
+};
+use std::error::Error;
+
+async fn create_swarm(config: MdnsConfig) -> Result<Swarm<Mdns>, Box<dyn Error>> {
+    let id_keys = identity::Keypair::generate_ed25519();
+    let peer_id = PeerId::from(id_keys.public());
+    let transport = libp2p::development_transport(id_keys).await?;
+    let behaviour = Mdns::new(config).await?;
+    let mut swarm = Swarm::new(transport, behaviour, peer_id);
+    swarm.listen_on("/ip4/0.0.0.0/tcp/0".parse()?)?;
+    Ok(swarm)
+}
+
+async fn run_test(config: MdnsConfig) -> Result<(), Box<dyn Error>> {
+    let mut a = create_swarm(config.clone()).await?;
+    let mut b = create_swarm(config).await?;
+    let mut discovered_a = false;
+    let mut discovered_b = false;
+    loop {
+        futures::select! {
+            ev = a.select_next_some() => match ev {
+                SwarmEvent::Behaviour(MdnsEvent::Discovered(peers)) => {
+                    for (peer, _addr) in peers {
+                        if peer == *b.local_peer_id() {
+                            if discovered_a {
+                                return Ok(());
+                            } else {
+                                discovered_b = true;
+                            }
+                        }
+                    }
+                }
+                _ => {}
+            },
+            ev = b.select_next_some() => match ev {
+                SwarmEvent::Behaviour(MdnsEvent::Discovered(peers)) => {
+                    for (peer, _addr) in peers {
+                        if peer == *a.local_peer_id() {
+                            if discovered_b {
+                                return Ok(());
+                            } else {
+                                discovered_a = true;
+                            }
+                        }
+                    }
+                }
+                _ => {}
+            }
+        }
+    }
+}
+
+#[async_std::test]
+async fn test_discovery_async_std_ipv4() -> Result<(), Box<dyn Error>> {
+    run_test(MdnsConfig::default()).await
+}
+
+#[async_std::test]
+async fn test_discovery_async_std_ipv6() -> Result<(), Box<dyn Error>> {
+    let mut config = MdnsConfig::default();
+    config.multicast_addr = *IPV6_MDNS_MULTICAST_ADDRESS;
+    run_test(MdnsConfig::default()).await
+}
+
+#[tokio::test]
+async fn test_discovery_tokio_ipv4() -> Result<(), Box<dyn Error>> {
+    run_test(MdnsConfig::default()).await
+}
+
+#[tokio::test]
+async fn test_discovery_tokio_ipv6() -> Result<(), Box<dyn Error>> {
+    let mut config = MdnsConfig::default();
+    config.multicast_addr = *IPV6_MDNS_MULTICAST_ADDRESS;
+    run_test(MdnsConfig::default()).await
+}