From 96fd393d2934af2a6cdcbf6bf32b4377a3d55863 Mon Sep 17 00:00:00 2001
From: Viktor Dukhovni <viktor@twosigma.com>
Date: Sat, 21 Sep 2019 18:29:12 -0400
Subject: [PATCH] Disable Nagle in iprop master and slave

---
 configure.ac              |  1 +
 include/config.h.w32      |  3 +++
 lib/kadm5/ipropd_master.c | 14 ++++++++++++++
 lib/kadm5/ipropd_slave.c  |  9 +++++++++
 lib/kadm5/kadm5_locl.h    |  6 ++++++
 5 files changed, 33 insertions(+)

diff --git a/configure.ac b/configure.ac
index e7611d2de..d07fd8a01 100644
--- a/configure.ac
+++ b/configure.ac
@@ -355,6 +355,7 @@ AC_CHECK_HEADERS([\
 	maillock.h				\
 	netgroup.h				\
 	netinet/in6_machtypes.h			\
+	netinet/tcp.h				\
 	pthread.h				\
 	pty.h					\
 	sac.h					\
diff --git a/include/config.h.w32 b/include/config.h.w32
index 0d6e6a3ef..c6c71d537 100644
--- a/include/config.h.w32
+++ b/include/config.h.w32
@@ -653,6 +653,9 @@ static const char *const rcsid[] = { (const char *)rcsid, "@(#)" msg }
 /* Define to 1 if you have the <netinet/in.h> header file. */
 /* #define HAVE_NETINET_IN_H 1 */
 
+/* Define to 1 if you have the <netinet/tcp.h> header file. */
+/* #define HAVE_NETINET_TCP_H 1 */
+
 /* Define to 1 if you have the <netinet/in_systm.h> header file. */
 /* #define HAVE_NETINET_IN_SYSTM_H 1 */
 
diff --git a/lib/kadm5/ipropd_master.c b/lib/kadm5/ipropd_master.c
index 053d45754..8639af66e 100644
--- a/lib/kadm5/ipropd_master.c
+++ b/lib/kadm5/ipropd_master.c
@@ -319,6 +319,20 @@ add_slave (krb5_context context, krb5_keytab keytab, slave **root,
      * own krb5_recvauth().
      */
     socket_set_nonblocking(s->fd, 1);
+
+    /*
+     * We write message lengths separately from the payload, and may do
+     * back-to-back small writes when flushing pending input and then a new
+     * update.  Avoid Nagle delays.
+     */
+#if defined(IPPROTO_TCP) && defined(TCP_NODELAY)
+    {
+        int nodelay = 1;
+        (void) setsockopt(s->fd, IPPROTO_TCP, TCP_NODELAY,
+                          (void *)&nodelay, sizeof(nodelay));
+    }
+#endif
+
     krb5_free_principal (context, server);
     if (ret) {
 	krb5_warn (context, ret, "krb5_recvauth");
diff --git a/lib/kadm5/ipropd_slave.c b/lib/kadm5/ipropd_slave.c
index 9f0b38d0a..933ce32e3 100644
--- a/lib/kadm5/ipropd_slave.c
+++ b/lib/kadm5/ipropd_slave.c
@@ -99,6 +99,15 @@ connect_to_master (krb5_context context, const char *master,
     if (setsockopt(s, SOL_SOCKET, SO_KEEPALIVE, &one, sizeof(one)) < 0)
         krb5_warn(context, errno, "setsockopt(SO_KEEPALIVE) failed");
 
+    /*
+     * We write message lengths separately from the payload, avoid Nagle
+     * delays.
+     */
+#if defined(IPPROTO_TCP) && defined(TCP_NODELAY)
+    (void) setsockopt(s, IPPROTO_TCP, TCP_NODELAY,
+                      (void *)&one, sizeof(one));
+#endif
+
     return s;
 }
 
diff --git a/lib/kadm5/kadm5_locl.h b/lib/kadm5/kadm5_locl.h
index ef5b83ee4..cb0b1b4cb 100644
--- a/lib/kadm5/kadm5_locl.h
+++ b/lib/kadm5/kadm5_locl.h
@@ -67,6 +67,12 @@
 #ifdef HAVE_SYS_SOCKET_H
 #include <sys/socket.h>
 #endif
+#ifdef HAVE_NETINET_IN_H
+#include <netinet/in.h>
+#endif
+#ifdef HAVE_NETINET_TCP_H
+#include <netinet/tcp.h>
+#endif
 #ifdef HAVE_SYS_UN_H
 #include <sys/un.h>
 #endif