move all "admin_netcat" stuff to a new admin_netcat module in the gateway-bin, not in the gateway lib

signal-gateway-bin/src/admin_netcat/mod.rs

@@ -0,0 +1,78 @@
+//! Admin netcat TCP client for forwarding messages to a TCP server
+//!
+//! This module handles admin messages not handled by the gateway by opening a TCP connection,
+//! writing the message terminated with CRLF, and reading the response until CRLF.
+
+use conf::Conf;
+use signal_gateway::MessageHandlerResult;
+use std::time::Duration;
+use tokio::{
+    io::{AsyncBufReadExt, AsyncWriteExt, BufReader},
+    net::TcpStream,
+    time::timeout,
+};
+
+/// Configuration for the admin netcat TCP client
+#[derive(Clone, Conf, Debug)]
+pub struct AdminNetcatConfig {
+    /// TCP address to forward admin commands to
+    #[conf(long, env)]
+    pub tcp_addr: String,
+    /// Timeout for connecting, writing, and reading
+    #[conf(long, env, default_value = "5s", value_parser = conf_extra::parse_duration)]
+    pub timeout: Duration,
+}
+
+impl AdminNetcatConfig {
+    /// Create a message handler function from this config.
+    ///
+    /// The returned handler opens a TCP connection to the configured address,
+    /// writes the message terminated with CRLF, and reads the response until CRLF.
+    pub fn into_handler(
+        self,
+    ) -> Box<
+        dyn Fn(
+                String,
+            )
+                -> std::pin::Pin<Box<dyn std::future::Future<Output = MessageHandlerResult> + Send>>
+            + Send
+            + Sync,
+    > {
+        Box::new(move |message: String| {
+            let config = self.clone();
+            Box::pin(async move { handle_message(&config, message).await })
+        })
+    }
+}
+
+/// Handle a message by forwarding it to the configured TCP server
+async fn handle_message(config: &AdminNetcatConfig, message: String) -> MessageHandlerResult {
+    // Connect to server
+    let mut stream = timeout(config.timeout, TcpStream::connect(&config.tcp_addr))
+        .await
+        .map_err(|_| (504u16, "connecting: timeout".into()))?
+        .map_err(|err| (502u16, format!("connecting: {err}").into()))?;
+
+    // Write message with CRLF terminator
+    let message = format!("{message}\r\n");
+    timeout(config.timeout, stream.write_all(message.as_bytes()))
+        .await
+        .map_err(|_| (504u16, "writing: timeout".into()))?
+        .map_err(|err| (502u16, format!("writing: {err}").into()))?;
+
+    // Read response until CR
+    let mut reader = BufReader::new(stream);
+    let mut buf = Vec::new();
+    timeout(config.timeout, reader.read_until(b'\r', &mut buf))
+        .await
+        .map_err(|_| (504u16, "reading: timeout".into()))?
+        .map_err(|err| (502u16, format!("reading: {err}").into()))?;
+
+    // Convert to string and trim the trailing CR
+    let text = std::str::from_utf8(&buf)
+        .map_err(|err| (502u16, format!("utf8: {err}").into()))?
+        .trim_end_matches(['\r', '\n'])
+        .to_owned();
+
+    Ok((text, vec![]))
+}

signal-gateway-bin/src/main.rs

@@ -9,6 +9,9 @@ use tokio_util::sync::CancellationToken;
 use tracing::{error, info, warn};
 use tracing_subscriber::EnvFilter;
 
+mod admin_netcat;
+use admin_netcat::AdminNetcatConfig;
+
 mod syslog;
 use syslog::SyslogUdpConfig;
 
@@ -22,6 +25,8 @@ struct Config {
     http_listen_addr: SocketAddr,
     #[conf(flatten, prefix)]
     syslog_udp: Option<SyslogUdpConfig>,
+    #[conf(flatten, prefix)]
+    admin_netcat: Option<AdminNetcatConfig>,
     #[conf(flatten)]
     gateway: GatewayConfig,
 }
@@ -68,7 +73,8 @@ async fn main() {
 
     let token = CancellationToken::new();
 
-    let gateway = Arc::new(Gateway::new(config.gateway, token.clone()).await);
+    let message_handler = config.admin_netcat.map(|c| c.into_handler());
+    let gateway = Arc::new(Gateway::new(config.gateway, token.clone(), message_handler).await);
 
     let listener = TcpListener::bind(config.http_listen_addr).await.unwrap();
     info!("Listening for http on {}", config.http_listen_addr);