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use async_trait::async_trait;
use std::{future::Future, net::Ipv4Addr};
use trust_dns_resolver::{error::ResolveErrorKind, AsyncResolver};
#[async_trait]
pub trait Lookup {
async fn lookup(&self, ip: Ipv4Addr) -> Option<String>;
}
pub struct Resolver(AsyncResolver);
impl Resolver {
pub fn new() -> Result<(Self, impl Future<Output = ()>), failure::Error> {
let (resolver, background) = AsyncResolver::from_system_conf()?;
Ok((Self(resolver), background))
}
}
#[async_trait]
impl Lookup for Resolver {
async fn lookup(&self, ip: Ipv4Addr) -> Option<String> {
let lookup_future = self.0.reverse_lookup(ip.into());
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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