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use async_trait::async_trait;
use std::net::IpAddr;
use std::net::SocketAddr;
use std::net::{Ipv4Addr, SocketAddrV4};
use tokio::runtime::Handle;
use trust_dns_resolver::config::{NameServerConfig, Protocol, ResolverConfig, ResolverOpts};
use trust_dns_resolver::{error::ResolveErrorKind, TokioAsyncResolver};
#[async_trait]
pub trait Lookup {
async fn lookup(&self, ip: IpAddr) -> Option<String>;
}
pub struct Resolver(TokioAsyncResolver);
impl Resolver {
pub async fn new(
runtime: Handle,
dns_server: &Option<Ipv4Addr>,
) -> Result<Self, failure::Error> {
let resolver = match dns_server {
Some(dns_server_address) => {
let mut config = ResolverConfig::new();
let options = ResolverOpts::default();
let socket = SocketAddr::V4(SocketAddrV4::new(*dns_server_address, 53));
let nameserver_config = NameServerConfig {
socket_addr: socket,
protocol: Protocol::Udp,
tls_dns_name: None,
};
config.add_name_server(nameserver_config);
TokioAsyncResolver::new(config, options, runtime).await?
}
None => TokioAsyncResolver::from_system_conf(runtime).await?,
};
Ok(Self(resolver))
}
}
#[async_trait]
impl Lookup for Resolver {
async fn lookup(&self, ip: IpAddr) -> Option<String> {
let lookup_future = self.0.reverse_lookup(ip);
match lookup_future.await {
Ok(names) => {
// Take the first result and convert it to a string
names.into_iter().next().map(|name| name.to_string())
}
Err(e) => match e.kind() {
// If the IP is not associated with a hostname, store the IP
// so that we don't retry indefinitely
ResolveErrorKind::NoRecordsFound { .. } => Some(ip.to_string()),
_ => None,
},
}
}
}
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