// Copyright 2018 Parity Technologies (UK) Ltd.
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//! Implementation of the libp2p-specific [mDNS](https://github.com/libp2p/specs/blob/master/discovery/mdns.md) protocol.
//!
//! mDNS is a protocol defined by [RFC 6762](https://tools.ietf.org/html/rfc6762) that allows
//! querying nodes that correspond to a certain domain name.
//!
//! In the context of libp2p, the mDNS protocol is used to discover other nodes on the local
//! network that support libp2p.
//!
//! # Usage
//!
//! This crate provides a `Mdns` and `TokioMdns`, depending on the enabled features, which
//! implements the `NetworkBehaviour` trait. This struct will automatically discover other
//! libp2p nodes on the local network.
//!

#![cfg_attr(docsrs, feature(doc_cfg, doc_auto_cfg))]

use std::net::{Ipv4Addr, Ipv6Addr};
use std::time::Duration;

mod behaviour;
pub use crate::behaviour::{GenMdns, MdnsEvent};

#[cfg(feature = "async-io")]
pub use crate::behaviour::Mdns;

#[cfg(feature = "tokio")]
pub use crate::behaviour::TokioMdns;

/// The DNS service name for all libp2p peers used to query for addresses.
const SERVICE_NAME: &[u8] = b"_p2p._udp.local";
/// `SERVICE_NAME` as a Fully Qualified Domain Name.
const SERVICE_NAME_FQDN: &str = "_p2p._udp.local.";
/// The meta query for looking up the `SERVICE_NAME`.
const META_QUERY_SERVICE: &[u8] = b"_services._dns-sd._udp.local";
/// `META_QUERY_SERVICE` as a Fully Qualified Domain Name.
const META_QUERY_SERVICE_FQDN: &str = "_services._dns-sd._udp.local.";

pub const IPV4_MDNS_MULTICAST_ADDRESS: Ipv4Addr = Ipv4Addr::new(224, 0, 0, 251);
pub const IPV6_MDNS_MULTICAST_ADDRESS: Ipv6Addr = Ipv6Addr::new(0xFF02, 0, 0, 0, 0, 0, 0, 0xFB);

/// Configuration for mDNS.
#[derive(Debug, Clone)]
pub struct MdnsConfig {
    /// TTL to use for mdns records.
    pub ttl: Duration,
    /// Interval at which to poll the network for new peers. This isn't
    /// necessary during normal operation but avoids the case that an
    /// initial packet was lost and not discovering any peers until a new
    /// peer joins the network. Receiving an mdns packet resets the timer
    /// preventing unnecessary traffic.
    pub query_interval: Duration,
    /// Use IPv6 instead of IPv4.
    pub enable_ipv6: bool,
}

impl Default for MdnsConfig {
    fn default() -> Self {
        Self {
            ttl: Duration::from_secs(6 * 60),
            query_interval: Duration::from_secs(5 * 60),
            enable_ipv6: false,
        }
    }
}