Initial commit

1 files changed, 56 insertions, 0 deletions

diff --git a/minecraft-protocol/src/resolver.rs b/minecraft-protocol/src/resolver.rs
new file mode 100644
index 00000000..5dc6df8b
--- /dev/null
+++ b/minecraft-protocol/src/resolver.rs
@@ -0,0 +1,56 @@
+use std::net::IpAddr;
+
+use crate::{ServerAddress, ServerIpAddress};
+use async_recursion::async_recursion;
+use trust_dns_resolver::{
+    config::{ResolverConfig, ResolverOpts},
+    TokioAsyncResolver,
+};
+
+/// Resolve a Minecraft server address into an IP address and port.
+/// If it's already an IP address, it's returned as-is.
+#[async_recursion]
+pub async fn resolve_address(address: &ServerAddress) -> Result<ServerIpAddress, String> {
+    // If the address.host is already in the format of an ip address, return it.
+    if let Ok(ip) = address.host.parse::<IpAddr>() {
+        return Ok(ServerIpAddress {
+            ip: ip,
+            port: address.port,
+        });
+    }
+
+    // we specify Cloudflare instead of the default resolver because trust_dns_resolver has an issue on Windows where it's really slow using the default resolver
+    let resolver =
+        TokioAsyncResolver::tokio(ResolverConfig::cloudflare(), ResolverOpts::default()).unwrap();
+
+    // first, we do a srv lookup for _minecraft._tcp.<host>
+    let srv_redirect_result = resolver
+        .srv_lookup(format!("_minecraft._tcp.{}", address.host).as_str())
+        .await;
+
+    // if it resolves that means it's a redirect so we call resolve_address again with the new host
+    if srv_redirect_result.is_ok() {
+        let redirect_result = srv_redirect_result.unwrap();
+        let redirect_srv = redirect_result
+            .iter()
+            .next()
+            .ok_or_else(|| "No SRV record found".to_string())?;
+        let redirect_address = ServerAddress {
+            host: redirect_srv.target().to_utf8(),
+            port: redirect_srv.port(),
+        };
+
+        println!("redirecting to {:?}", redirect_address);
+
+        return resolve_address(&redirect_address).await;
+    }
+
+    // there's no redirect, try to resolve this as an ip address
+    let lookup_ip_result = resolver.lookup_ip(address.host.clone()).await;
+    let lookup_ip = lookup_ip_result.map_err(|_| "No IP found".to_string())?;
+
+    Ok(ServerIpAddress {
+        ip: lookup_ip.iter().next().unwrap(),
+        port: address.port,
+    })
+}