Supports configuration of all TCP Keepalive parameters per https://en.wikipedia.org/wiki/Keepalive

src/server/server.rs

@@ -2,10 +2,12 @@ use std::error::Error as StdError;
 use std::fmt;
 #[cfg(feature = "tcp")]
 use std::net::{SocketAddr, TcpListener as StdTcpListener};
-#[cfg(any(feature = "tcp", feature = "http1"))]
+
+#[cfg(feature = "tcp")]
 use std::time::Duration;
 
 use pin_project_lite::pin_project;
+
 use tokio::io::{AsyncRead, AsyncWrite};
 use tracing::trace;
 
@@ -559,16 +561,27 @@ impl<I, E> Builder<I, E> {
     doc(cfg(all(feature = "tcp", any(feature = "http1", feature = "http2"))))
 )]
 impl<E> Builder<AddrIncoming, E> {
-    /// Set whether TCP keepalive messages are enabled on accepted connections.
+    /// Set the duration to remain idle before sending TCP keepalive probes.
     ///
-    /// If `None` is specified, keepalive is disabled, otherwise the duration
-    /// specified will be the time to remain idle before sending TCP keepalive
-    /// probes.
+    /// If `None` is specified, keepalive is disabled.
     pub fn tcp_keepalive(mut self, keepalive: Option<Duration>) -> Self {
         self.incoming.set_keepalive(keepalive);
         self
     }
 
+    /// Set the duration between two successive TCP keepalive retransmissions,
+    /// if acknowledgement to the previous keepalive transmission is not received.
+    pub fn tcp_keepalive_interval(mut self, interval: Option<Duration>) -> Self {
+        self.incoming.set_keepalive_interval(interval);
+        self
+    }
+
+    /// Set the number of retransmissions to be carried out before declaring that remote end is not available.
+    pub fn tcp_keepalive_retries(mut self, retries: Option<u32>) -> Self {
+        self.incoming.set_keepalive_retries(retries);
+        self
+    }
+
     /// Set the value of `TCP_NODELAY` option for accepted connections.
     pub fn tcp_nodelay(mut self, enabled: bool) -> Self {
         self.incoming.set_nodelay(enabled);

src/server/tcp.rs

@@ -2,6 +2,7 @@ use std::fmt;
 use std::io;
 use std::net::{SocketAddr, TcpListener as StdTcpListener};
 use std::time::Duration;
+use socket2::TcpKeepalive;
 
 use tokio::net::TcpListener;
 use tokio::time::Sleep;
@@ -13,13 +14,65 @@ use crate::common::{task, Future, Pin, Poll};
 pub use self::addr_stream::AddrStream;
 use super::accept::Accept;
 
+#[derive(Default, Debug, Clone, Copy)]
+struct TcpKeepaliveConfig {
+    time: Option<Duration>,
+    interval: Option<Duration>,
+    retries: Option<u32>,
+}
+
+impl TcpKeepaliveConfig {
+    /// Converts into a `socket2::TcpKeealive` if there is any keep alive configuration.
+    fn into_socket2(self) -> Option<TcpKeepalive> {
+        let mut dirty = false;
+        let mut ka = TcpKeepalive::new();
+        if let Some(time) = self.time {
+            ka = ka.with_time(time);
+            dirty = true
+        }
+        if let Some(interval) = self.interval {
+            ka = Self::ka_with_interval(ka, interval, &mut dirty)
+        };
+        if let Some(retries) = self.retries {
+            ka = Self::ka_with_retries(ka, retries, &mut dirty)
+        };
+        if dirty {
+            Some(ka)
+        } else {
+            None
+        }
+    }
+
+    #[cfg(not(any(target_os = "openbsd", target_os = "redox", target_os = "solaris")))]
+    fn ka_with_interval(ka: TcpKeepalive, interval: Duration, dirty: &mut bool) -> TcpKeepalive {
+        *dirty = true;
+        ka.with_interval(interval)
+    }
+
+    #[cfg(any(target_os = "openbsd", target_os = "redox", target_os = "solaris"))]
+    fn ka_with_interval(ka: TcpKeepalive, _: Duration, _: &mut bool) -> TcpKeepalive {
+        ka  // no-op as keepalive interval is not supported on this platform
+    }
+
+    #[cfg(not(any(target_os = "openbsd", target_os = "redox", target_os = "solaris", target_os = "windows")))]
+    fn ka_with_retries(ka: TcpKeepalive, retries: u32, dirty: &mut bool) -> TcpKeepalive {
+        *dirty = true;
+        ka.with_retries(retries)
+    }
+
+    #[cfg(any(target_os = "openbsd", target_os = "redox", target_os = "solaris", target_os = "windows"))]
+    fn ka_with_retries(ka: TcpKeepalive, _: u32, _: &mut bool) -> TcpKeepalive {
+        ka  // no-op as keepalive retries is not supported on this platform
+    }
+}
+
 /// A stream of connections from binding to an address.
 #[must_use = "streams do nothing unless polled"]
 pub struct AddrIncoming {
     addr: SocketAddr,
     listener: TcpListener,
     sleep_on_errors: bool,
-    tcp_keepalive_timeout: Option<Duration>,
+    tcp_keepalive_config: TcpKeepaliveConfig,
     tcp_nodelay: bool,
     timeout: Option<Pin<Box<Sleep>>>,
 }
@@ -52,7 +105,7 @@ impl AddrIncoming {
             listener,
             addr,
             sleep_on_errors: true,
-            tcp_keepalive_timeout: None,
+            tcp_keepalive_config: TcpKeepaliveConfig::default(),
             tcp_nodelay: false,
             timeout: None,
         })
@@ -63,13 +116,24 @@ impl AddrIncoming {
         self.addr
     }
 
-    /// Set whether TCP keepalive messages are enabled on accepted connections.
+    /// Set the duration to remain idle before sending TCP keepalive probes.
     ///
-    /// If `None` is specified, keepalive is disabled, otherwise the duration
-    /// specified will be the time to remain idle before sending TCP keepalive
-    /// probes.
-    pub fn set_keepalive(&mut self, keepalive: Option<Duration>) -> &mut Self {
-        self.tcp_keepalive_timeout = keepalive;
+    /// If `None` is specified, keepalive is disabled.
+    pub fn set_keepalive(&mut self, time: Option<Duration>) -> &mut Self {
+        self.tcp_keepalive_config.time = time;
+        self
+    }
+
+    /// Set the duration between two successive TCP keepalive retransmissions,
+    /// if acknowledgement to the previous keepalive transmission is not received.
+    pub fn set_keepalive_interval(&mut self, interval: Option<Duration>) -> &mut Self {
+        self.tcp_keepalive_config.interval = interval;
+        self
+    }
+
+    /// Set the number of retransmissions to be carried out before declaring that remote end is not available.
+    pub fn set_keepalive_retries(&mut self, retries: Option<u32>) -> &mut Self {
+        self.tcp_keepalive_config.retries = retries;
         self
     }
 
@@ -108,10 +172,9 @@ impl AddrIncoming {
         loop {
             match ready!(self.listener.poll_accept(cx)) {
                 Ok((socket, remote_addr)) => {
-                    if let Some(dur) = self.tcp_keepalive_timeout {
-                        let socket = socket2::SockRef::from(&socket);
-                        let conf = socket2::TcpKeepalive::new().with_time(dur);
-                        if let Err(e) = socket.set_tcp_keepalive(&conf) {
+                    if let Some(tcp_keepalive) = &self.tcp_keepalive_config.into_socket2() {
+                        let sock_ref = socket2::SockRef::from(&socket);
+                        if let Err(e) = sock_ref.set_tcp_keepalive(tcp_keepalive) {
                             trace!("error trying to set TCP keepalive: {}", e);
                         }
                     }
@@ -188,7 +251,7 @@ impl fmt::Debug for AddrIncoming {
         f.debug_struct("AddrIncoming")
             .field("addr", &self.addr)
             .field("sleep_on_errors", &self.sleep_on_errors)
-            .field("tcp_keepalive_timeout", &self.tcp_keepalive_timeout)
+            .field("tcp_keepalive_config", &self.tcp_keepalive_config)
             .field("tcp_nodelay", &self.tcp_nodelay)
             .finish()
     }
@@ -316,3 +379,49 @@ mod addr_stream {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use std::time::Duration;
+    use crate::server::tcp::TcpKeepaliveConfig;
+
+    #[test]
+    fn no_tcp_keepalive_config() {
+        assert!(TcpKeepaliveConfig::default().into_socket2().is_none());
+    }
+
+    #[test]
+    fn tcp_keepalive_time_config() {
+        let mut kac = TcpKeepaliveConfig::default();
+        kac.time = Some(Duration::from_secs(60));
+        if let Some(tcp_keepalive) = kac.into_socket2() {
+            assert!(format!("{tcp_keepalive:?}").contains("time: Some(60s)"));
+        } else {
+            panic!("test failed");
+        }
+    }
+
+    #[cfg(not(any(target_os = "openbsd", target_os = "redox", target_os = "solaris")))]
+    #[test]
+    fn tcp_keepalive_interval_config() {
+        let mut kac = TcpKeepaliveConfig::default();
+        kac.interval = Some(Duration::from_secs(1));
+        if let Some(tcp_keepalive) = kac.into_socket2() {
+            assert!(format!("{tcp_keepalive:?}").contains("interval: Some(1s)"));
+        } else {
+            panic!("test failed");
+        }
+    }
+
+    #[cfg(not(any(target_os = "openbsd", target_os = "redox", target_os = "solaris", target_os = "windows")))]
+    #[test]
+    fn tcp_keepalive_retries_config() {
+        let mut kac = TcpKeepaliveConfig::default();
+        kac.retries = Some(3);
+        if let Some(tcp_keepalive) = kac.into_socket2() {
+            assert!(format!("{tcp_keepalive:?}").contains("retries: Some(3)"));
+        } else {
+            panic!("test failed");
+        }
+    }
+}