feat(tcp): expose socket2 set_linger

to allow for faster connection close time, see more on https://docs.rs/socket2/latest/socket2/struct.Socket.html#method.set_linger

Pull-Request: libp2p#6225.

Author: jxs

Cargo.lock

@@ -105,7 +105,7 @@ libp2p-stream = { version = "0.4.0-alpha", path = "protocols/stream" }
 libp2p-swarm = { version = "0.47.0", path = "swarm" }
 libp2p-swarm-derive = { version = "=0.35.1", path = "swarm-derive" } # `libp2p-swarm-derive` may not be compatible with different `libp2p-swarm` non-breaking releases. E.g. `libp2p-swarm` might introduce a new enum variant `FromSwarm` (which is `#[non-exhaustive]`) in a non-breaking release. Older versions of `libp2p-swarm-derive` would not forward this enum variant within the `NetworkBehaviour` hierarchy. Thus the version pinning is required.
 libp2p-swarm-test = { version = "0.6.0", path = "swarm-test" }
-libp2p-tcp = { version = "0.44.0", path = "transports/tcp" }
+libp2p-tcp = { version = "0.44.1", path = "transports/tcp" }
 libp2p-tls = { version = "0.6.2", path = "transports/tls" }
 libp2p-uds = { version = "0.43.1", path = "transports/uds" }
 libp2p-upnp = { version = "0.6.0", path = "protocols/upnp" }

Cargo.toml

@@ -1,3 +1,7 @@
+## 0.44.1
+- Expose `socket2`'s `set_linger` config option.
+  See [PR 6225](https://github.com/libp2p/rust-libp2p/pull/5955)
+
 ## 0.44.0
 
 - Remove `async-std` support.

transports/tcp/CHANGELOG.md

@@ -3,7 +3,7 @@ name = "libp2p-tcp"
 edition.workspace = true
 rust-version = { workspace = true }
 description = "TCP/IP transport protocol for libp2p"
-version = "0.44.0"
+version = "0.44.1"
 authors = ["Parity Technologies <admin@parity.io>"]
 license = "MIT"
 repository = "https://github.com/libp2p/rust-libp2p"

transports/tcp/Cargo.toml

@@ -59,6 +59,9 @@ pub struct Config {
     ttl: Option<u32>,
     /// `TCP_NODELAY` to set for opened sockets.
     nodelay: bool,
+    /// `SO_LINGER` to set for opened sockets,
+    /// by default is `None`.
+    linger: Option<Duration>,
     /// Size of the listen backlog for listen sockets.
     backlog: u32,
 }
@@ -137,6 +140,7 @@ impl Config {
         Self {
             ttl: None,
             nodelay: true, // Disable Nagle's algorithm by default.
+            linger: None,
             backlog: 1024,
         }
     }
@@ -159,6 +163,12 @@ impl Config {
         self
     }
 
+    /// Configures the `SO_LINGER` option for new sockets.
+    pub fn linger(mut self, duration: Option<Duration>) -> Self {
+        self.linger = duration;
+        self
+    }
+
     /// Configures port reuse for local sockets, which implies
     /// reuse of listening ports for outgoing connections to
     /// enhance NAT traversal capabilities.
@@ -196,6 +206,11 @@ impl Config {
         if let Some(ttl) = self.ttl {
             socket.set_ttl_v4(ttl)?;
         }
+
+        if self.linger.is_some() {
+            socket.set_linger(self.linger)?;
+        }
+
         socket.set_tcp_nodelay(self.nodelay)?;
         socket.set_reuse_address(true)?;
         #[cfg(all(unix, not(any(target_os = "solaris", target_os = "illumos"))))]