[Lib] remove feature built-in-dns

.github/workflows/example_0.13.yml

@@ -70,7 +70,7 @@ jobs:
 
     - name: UDP Socket Example
       run: |
-        cargo build --target wasm32-wasi --example=udp_socket --release --no-default-features --features=built-in-dns
+        cargo build --target wasm32-wasi --example=udp_socket --release
         wasmedge target/wasm32-wasi/release/examples/udp_socket.wasm
 
     - name: DNS Example

Cargo.toml

@@ -22,6 +22,5 @@ rand = "0.8.5"
 
 [features]
 default = []
-built-in-dns = []
 wasi_poll = []
 epoll = []

src/lib.rs

@@ -318,8 +318,16 @@ impl AsRawFd for UdpSocket {
     }
 }
 
-#[cfg(not(feature = "built-in-dns"))]
 pub fn nslookup(node: &str, service: &str) -> std::io::Result<Vec<SocketAddr>> {
+    let dns_server = std::env::var("DNS_SERVER");
+    if let Ok(dns_server) = dns_server {
+        nslookup_with_dns_server(&dns_server, node, service)
+    } else {
+        nslookup_with_host(node, service)
+    }
+}
+
+pub fn nslookup_with_host(node: &str, service: &str) -> std::io::Result<Vec<SocketAddr>> {
     use socket::WasiAddrinfo;
     let hints: WasiAddrinfo = WasiAddrinfo::default();
     let mut sockaddrs = Vec::new();
@@ -367,11 +375,13 @@ pub fn nslookup(node: &str, service: &str) -> std::io::Result<Vec<SocketAddr>> {
     Ok(r_addrs)
 }
 
-#[cfg(feature = "built-in-dns")]
-pub fn nslookup(node: &str, _service: &str) -> std::io::Result<Vec<SocketAddr>> {
-    let dns_server = std::env::var("DNS_SERVER").unwrap_or("8.8.8.8:53".into());
+pub fn nslookup_with_dns_server(
+    dns_server: &str,
+    node: &str,
+    _service: &str,
+) -> std::io::Result<Vec<SocketAddr>> {
     let mut conn = TcpStream::connect(dns_server)?;
-    let timeout = std::time::Duration::from_secs(1);
+    let timeout = std::time::Duration::from_secs(5);
     let _ignore = conn.as_mut().set_send_timeout(Some(timeout));
     let _ignore = conn.as_mut().set_recv_timeout(Some(timeout));
 

src/socket.rs

@@ -101,7 +101,6 @@ impl Default for WasiSockaddr {
     }
 }
 
-#[cfg(not(feature = "built-in-dns"))]
 #[derive(Debug, Clone)]
 #[repr(C, packed(4))]
 pub struct WasiAddrinfo {
@@ -116,7 +115,6 @@ pub struct WasiAddrinfo {
     pub ai_next: *mut WasiAddrinfo,
 }
 
-#[cfg(not(feature = "built-in-dns"))]
 impl WasiAddrinfo {
     pub fn default() -> WasiAddrinfo {
         WasiAddrinfo {