use bigger socket buffers and optimizations on idle connections

main_linux.go

@@ -33,9 +33,16 @@ func setTCPParameters(_, _ string, c syscall.RawConn) error {
 
 		_ = unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_REUSEPORT, 1)
 
+		{
+			// Enable big buffers
+			_ = unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_SNDBUF, opts.SendBufSize)
+
+			_ = unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_RCVBUF, opts.RecvBufSize)
+		}
+
 		// Enable TCP open
-		// https://lwn.net/Articles/508865/ - 16k queue size.
-		_ = syscall.SetsockoptInt(fd, syscall.SOL_TCP, unix.TCP_FASTOPEN, 16*1024)
+		// https://lwn.net/Articles/508865/ - 32k queue size.
+		_ = syscall.SetsockoptInt(fd, syscall.SOL_TCP, unix.TCP_FASTOPEN, 32*1024)
 
 		// Enable TCP fast connect
 		// TCPFastOpenConnect sets the underlying socket to use
@@ -46,6 +53,26 @@ func setTCPParameters(_, _ string, c syscall.RawConn) error {
 		// Enable TCP quick ACK, John Nagle says
 		// "Set TCP_QUICKACK. If you find a case where that makes things worse, let me know."
 		_ = syscall.SetsockoptInt(fd, syscall.IPPROTO_TCP, unix.TCP_QUICKACK, 1)
+
+		// The time (in seconds) the connection needs to remain idle before
+		// TCP starts sending keepalive probes
+		_ = syscall.SetsockoptInt(fd, syscall.IPPROTO_TCP, syscall.TCP_KEEPIDLE, 15)
+
+		// Number of probes.
+		// ~ cat /proc/sys/net/ipv4/tcp_keepalive_probes (defaults to 9, we reduce it to 5)
+		_ = syscall.SetsockoptInt(fd, syscall.IPPROTO_TCP, syscall.TCP_KEEPCNT, 5)
+
+		// Wait time after successful probe in seconds.
+		// ~ cat /proc/sys/net/ipv4/tcp_keepalive_intvl (defaults to 75 secs, we reduce it to 15 secs)
+		_ = syscall.SetsockoptInt(fd, syscall.IPPROTO_TCP, syscall.TCP_KEEPINTVL, 15)
+
+		// Set tcp user timeout in addition to the keep-alive - tcp-keepalive is not enough to close a socket
+		// with dead end because tcp-keepalive is not fired when there is data in the socket buffer.
+		//    https://blog.cloudflare.com/when-tcp-sockets-refuse-to-die/
+		// This is a sensitive configuration, it is better to set it to high values, > 60 secs since it can
+		// affect clients reading data with a very slow pace  (disappropriate with socket buffer sizes)
+		_ = syscall.SetsockoptInt(fd, syscall.IPPROTO_TCP, unix.TCP_USER_TIMEOUT, 600000)
+
 	})
 	return nil
 }