Refactors the fd optimization code to FdUtils class.

src/utils/ClientConnection.cxx

@@ -38,40 +38,18 @@
 #include "netinet/tcp.h"
 #include "nmranet_config.h"
 
-/** Callback from try_connect to donate the file descriptor. @param fd is
- * the file destriptor of the connection freshly opened.  */
+#include "utils/FdUtils.hxx"
+
+/// Callback from try_connect to donate the file descriptor.
+/// @param fd is the file destriptor of the connection freshly opened.
 void GCFdConnectionClient::connection_complete(int fd)
 {
-    struct stat statbuf;
-    fstat(fd, &statbuf);
-
     const bool use_select =
         (config_gridconnect_tcp_use_select() == CONSTANT_TRUE);
+
+    // Applies kernel parameters like socket options.
+    FdUtils::optimize_fd(fd);
+
     fd_ = fd;
-    const int rcvbuf = config_gridconnect_tcp_rcv_buffer_size();
-    if (rcvbuf > 1)
-    {
-        ::setsockopt(fd, SOL_SOCKET, SO_RCVBUF, &rcvbuf, sizeof(rcvbuf));
-    }
-    const int sndbuf = config_gridconnect_tcp_snd_buffer_size();
-    if (sndbuf > 1)
-    {
-        ::setsockopt(fd, SOL_SOCKET, SO_SNDBUF, &sndbuf, sizeof(sndbuf));
-        int ret = 0;
-        socklen_t retsize = sizeof(ret);
-        ::getsockopt(fd, SOL_SOCKET, SO_SNDBUF, &ret, &retsize);
-        LOG(ALWAYS, "fd %d sndbuf %d", fd, ret);
-    }
-    const int lowat = 4096;
-    if (lowat > 1 && S_ISSOCK(statbuf.st_mode))
-    {
-        ERRNOCHECK("tcp lowat",
-            ::setsockopt(
-                fd, IPPROTO_TCP, TCP_NOTSENT_LOWAT, &lowat, sizeof(lowat)));
-        int ret = 0;
-        socklen_t retsize = sizeof(ret);
-        ::getsockopt(fd, IPPROTO_TCP, TCP_NOTSENT_LOWAT, &ret, &retsize);
-        LOG(ALWAYS, "fd %d lowat %d", fd, ret);
-    }
     create_gc_port_for_can_hub(hub_, fd, &closedNotify_, use_select);
 }

src/utils/ClientConnection.hxx

@@ -36,11 +36,11 @@
 #define _UTILS_CLIENTCONNECTION_HXX_
 
 #include <stdio.h>
-#include <termios.h> /* tc* functions */
 #include <unistd.h>
 
 #include "utils/GridConnectHub.hxx"
 #include "utils/socket_listener.hxx"
+#include "utils/FdUtils.hxx"
 
 /// Abstract base class for the Hub's connections.
 class ConnectionClient
@@ -170,18 +170,9 @@ private:
         int fd = ::open(dev_.c_str(), O_RDWR);
         if (fd >= 0)
         {
-            // Sets up the terminal in raw mode. Otherwise linux might echo
-            // characters coming in from the device and that will make
-            // packets go back to where they came from.
-            HASSERT(!tcflush(fd, TCIOFLUSH));
-            struct termios settings;
-            HASSERT(!tcgetattr(fd, &settings));
-            cfmakeraw(&settings);
-            cfsetspeed(&settings, B115200);
-            HASSERT(!tcsetattr(fd, TCSANOW, &settings));
+            FdUtils::optimize_tty_fd(fd);
             LOG(INFO, "Opened device %s.\n", dev_.c_str());
             connection_complete(fd);
-            //
         }
         else
         {

src/utils/FdUtils.cxx

@@ -0,0 +1,126 @@
+/** \copyright
+ * Copyright (c) 2023, Balazs Racz
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are  permitted provided that the following conditions are met:
+ *
+ *  - Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ *
+ *  - Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ * \file FdUtils.cxx
+ *
+ * Helper functions for dealing with posix fds.
+ *
+ * @author Balazs Racz
+ * @date 29 Dec 2023
+ */
+
+#include "FdUtils.hxx"
+
+#include <netinet/in.h>
+#include <netinet/tcp.h>
+#include <sys/stat.h>
+#include <termios.h> /* tc* functions */
+
+#include "nmranet_config.h"
+
+#define PCALL_LOGERR(where, callfn, fd, args...)                               \
+    do                                                                         \
+    {                                                                          \
+        int ret = callfn(fd, args);                                            \
+        if (ret < 0)                                                           \
+        {                                                                      \
+            char buf[256];                                                     \
+            strerror_r(errno, buf, sizeof(buf));                               \
+            LOG_ERROR("fd %d %s: %s", fd, where, buf);                         \
+        }                                                                      \
+    } while (0)
+
+/// Optimizes the kernel settings like socket and TCP options for an fd
+/// that is an outgoing TCP socket.
+/// @param fd socket file descriptor.
+void FdUtils::optimize_socket_fd(int fd)
+{
+#ifdef __linux__
+    const int rcvbuf = config_gridconnect_tcp_rcv_buffer_size();
+    if (rcvbuf > 1)
+    {
+        PCALL_LOGERR("setsockopt SO_RCVBUF", ::setsockopt, fd, SOL_SOCKET,
+            SO_RCVBUF, &rcvbuf, sizeof(rcvbuf));
+    }
+    const int sndbuf = config_gridconnect_tcp_snd_buffer_size();
+    if (sndbuf > 1)
+    {
+        PCALL_LOGERR("setsockopt SO_SNDBUF", ::setsockopt, fd, SOL_SOCKET,
+            SO_SNDBUF, &sndbuf, sizeof(sndbuf));
+        int ret = 0;
+        socklen_t retsize = sizeof(ret);
+        ::getsockopt(fd, SOL_SOCKET, SO_SNDBUF, &ret, &retsize);
+        LOG(ALWAYS, "fd %d sndbuf %d", fd, ret);
+    }
+    const int lowat = 4096;
+    if (lowat > 1)
+    {
+        PCALL_LOGERR("setsockopt tcp_notsent_lowat", ::setsockopt, fd,
+            IPPROTO_TCP, TCP_NOTSENT_LOWAT, &lowat, sizeof(lowat));
+        int ret = 0;
+        socklen_t retsize = sizeof(ret);
+        ::getsockopt(fd, IPPROTO_TCP, TCP_NOTSENT_LOWAT, &ret, &retsize);
+        LOG(ALWAYS, "fd %d lowat %d", fd, ret);
+    }
+#endif
+}
+
+/// Sets the kernel settings like queuing and terminal settings for an fd
+/// that is an outgoing tty.
+/// @param fd tty file descriptor.
+void FdUtils::optimize_tty_fd(int fd)
+{
+#ifdef __linux__
+    // Sets up the terminal in raw mode. Otherwise linux might echo
+    // characters coming in from the device and that will make
+    // packets go back to where they came from.
+    HASSERT(!tcflush(fd, TCIOFLUSH));
+    struct termios settings;
+    HASSERT(!tcgetattr(fd, &settings));
+    cfmakeraw(&settings);
+    cfsetspeed(&settings, B115200);
+    HASSERT(!tcsetattr(fd, TCSANOW, &settings));
+#endif
+}
+
+/// For an fd that is an outgoing link, detects what kind of file
+/// descriptor this is and calls the appropriate optimize call for it.
+void FdUtils::optimize_fd(int fd)
+{
+#ifdef __linux__
+    struct stat statbuf;
+    fstat(fd, &statbuf);
+
+    if (S_ISSOCK(statbuf.st_mode))
+    {
+        optimize_socket_fd(fd);
+    }
+    else if (isatty(fd))
+    {
+        optimize_tty_fd(fd);
+    }
+#endif
+}

src/utils/FdUtils.hxx

@@ -35,6 +35,8 @@
 #ifndef _UTILS_FD_UTILS_HXX_
 #define _UTILS_FD_UTILS_HXX_
 
+#include <unistd.h>
+
 #include "utils/logging.h"
 #include "utils/macros.h"
 
@@ -81,6 +83,20 @@ struct FdUtils
             dst += ret;
         }
     }
+
+    /// Optimizes the kernel settings like socket and TCP options for an fd
+    /// that is an outgoing TCP socket.
+    /// @param fd socket file descriptor.
+    static void optimize_socket_fd(int fd);
+
+    /// Sets the kernel settings like queuing and terminal settings for an fd
+    /// that is an outgoing tty.
+    /// @param fd tty file descriptor.
+    static void optimize_tty_fd(int fd);
+
+    /// For an fd that is an outgoing link, detects what kind of file
+    /// descriptor this is and calls the appropriate optimize call for it.
+    static void optimize_fd(int fd);
 };
 
 #endif // _UTILS_FD_UTILS_HXX_

src/utils/GcTcpHub.cxx

@@ -38,6 +38,7 @@
 
 #include "nmranet_config.h"
 #include "utils/GridConnectHub.hxx"
+#include "utils/FdUtils.hxx"
 
 void GcTcpHub::on_new_connection(int fd)
 {
@@ -47,16 +48,8 @@ void GcTcpHub::on_new_connection(int fd)
         AtomicHolder h(this);
         numClients_++;
     }
-    const int rcvbuf = config_gridconnect_tcp_rcv_buffer_size();
-    if (rcvbuf > 1)
-    {
-        ::setsockopt(fd, SOL_SOCKET, SO_RCVBUF, &rcvbuf, sizeof(rcvbuf));
-    }
-    const int sndbuf = config_gridconnect_tcp_snd_buffer_size();
-    if (sndbuf > 1)
-    {
-        ::setsockopt(fd, SOL_SOCKET, SO_SNDBUF, &sndbuf, sizeof(sndbuf));
-    }
+    // Applies kernel parameters like socket options.
+    FdUtils::optimize_socket_fd(fd);
     create_gc_port_for_can_hub(canHub_, fd, this, use_select);
 }
 

src/utils/sources

@@ -12,6 +12,7 @@ CXXSRCS += \
 	   StringPrintf.cxx \
            Buffer.cxx \
            ConfigUpdateListener.cxx \
+           FdUtils.cxx \
            FileUtils.cxx \
            ForwardAllocator.cxx \
            GcStreamParser.cxx \