CURLOPT_TCP_NODELAY: now enabled by default

After a few wasted hours hunting down the reason for slowness during a
TLS handshake that turned out to be because of TCP_NODELAY not being
set, I think we have enough motivation to toggle the default for this
option. We now enable TCP_NODELAY by default and allow applications to
switch it off.

This also makes --tcp-nodelay unnecessary, but --no-tcp-nodelay can be
used to disable it.

Thanks-to: Tim Rühsen
Bug: https://curl.haxx.se/mail/lib-2016-06/0143.html

6 files changed, 13 insertions, 14 deletions

diff --git a/docs/libcurl/opts/CURLOPT_TCP_NODELAY.3 b/docs/libcurl/opts/CURLOPT_TCP_NODELAY.3
index efb258693..bd19fbaf0 100644
--- a/docs/libcurl/opts/CURLOPT_TCP_NODELAY.3
+++ b/docs/libcurl/opts/CURLOPT_TCP_NODELAY.3
@@ -5,7 +5,7 @@
 .\" *                            | (__| |_| |  _ <| |___
 .\" *                             \___|\___/|_| \_\_____|
 .\" *
-.\" * Copyright (C) 1998 - 2014, Daniel Stenberg, <daniel@haxx.se>, et al.
+.\" * Copyright (C) 1998 - 2016, Daniel Stenberg, <daniel@haxx.se>, et al.
 .\" *
 .\" * This software is licensed as described in the file COPYING, which
 .\" * you should have received as part of this distribution. The terms
@@ -20,7 +20,7 @@
 .\" *
 .\" **************************************************************************
 .\"
-.TH CURLOPT_TCP_NODELAY 3 "19 Jun 2014" "libcurl 7.37.0" "curl_easy_setopt options"
+.TH CURLOPT_TCP_NODELAY 3 "30 Jun 2016" "libcurl 7.50.0" "curl_easy_setopt options"
 .SH NAME
 CURLOPT_TCP_NODELAY \- set the TCP_NODELAY option
 .SH SYNOPSIS
@@ -29,8 +29,8 @@ CURLOPT_TCP_NODELAY \- set the TCP_NODELAY option
 CURLcode curl_easy_setopt(CURL *handle, CURLOPT_TCP_NODELAY, long nodelay);
 .SH DESCRIPTION
 Pass a long specifying whether the TCP_NODELAY option is to be set or cleared
-(1 = set, 0 = clear). The option is cleared by default. This will have no
-effect after the connection has been established.
+(1 = set, 0 = clear). The option is set by default. This will have no effect
+after the connection has been established.
 
 Setting this option will disable TCP's Nagle algorithm. The purpose of this
 algorithm is to try to minimize the number of small packets on the network
@@ -43,13 +43,13 @@ need to be sent without delay. This is less efficient than sending larger
 amounts of data at a time, and can contribute to congestion on the network if
 overdone.
 .SH DEFAULT
-0
+1
 .SH PROTOCOLS
 All
 .SH EXAMPLE
 TODO
 .SH AVAILABILITY
-Always
+Always. The default was changed to 1 from 0 in 7.50.2.
 .SH RETURN VALUE
 Returns CURLE_OK
 .SH "SEE ALSO"
diff --git a/lib/http2.c b/lib/http2.c
index 8e10c6601..5bed6fcdf 100644
--- a/lib/http2.c
+++ b/lib/http2.c
@@ -1849,10 +1849,6 @@ CURLcode Curl_http2_setup(struct connectdata *conn)
   infof(conn->data, "Connection state changed (HTTP/2 confirmed)\n");
   Curl_multi_connchanged(conn->data->multi);
 
-  /* switch on TCP_NODELAY as we need to send off packets without delay for
-     maximum throughput */
-  Curl_tcpnodelay(conn, conn->sock[FIRSTSOCKET]);
-
   return CURLE_OK;
 }
 
diff --git a/lib/url.c b/lib/url.c
index da48da6b9..bda3ccddb 100644
--- a/lib/url.c
+++ b/lib/url.c
@@ -602,6 +602,7 @@ CURLcode Curl_init_userdefined(struct UserDefined *set)
   set->tcp_keepintvl = 60;
   set->tcp_keepidle = 60;
   set->tcp_fastopen = FALSE;
+  set->tcp_nodelay = TRUE;
 
   set->ssl_enable_npn = TRUE;
   set->ssl_enable_alpn = TRUE;
diff --git a/src/tool_cfgable.c b/src/tool_cfgable.c
index 8b60a91b7..567123b82 100644
--- a/src/tool_cfgable.c
+++ b/src/tool_cfgable.c
@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2015, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2016, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -41,6 +41,7 @@ void config_init(struct OperationConfig* config)
                           CURLPROTO_SMBS);
   config->proto_redir_present = FALSE;
   config->proto_default = NULL;
+  config->tcp_nodelay = TRUE; /* enabled by default */
 }
 
 static void free_config_fields(struct OperationConfig *config)
diff --git a/src/tool_operate.c b/src/tool_operate.c
index 2b53c9a85..97bb87b3d 100644
--- a/src/tool_operate.c
+++ b/src/tool_operate.c
@@ -792,8 +792,8 @@ static CURLcode operate_do(struct GlobalConfig *global,
           set_binmode(stdout);
         }
 
-        if(config->tcp_nodelay)
-          my_setopt(curl, CURLOPT_TCP_NODELAY, 1L);
+        if(!config->tcp_nodelay)
+          my_setopt(curl, CURLOPT_TCP_NODELAY, 0L);
 
         if(config->tcp_fastopen)
           my_setopt(curl, CURLOPT_TCP_FASTOPEN, 1L);
diff --git a/src/tool_setopt.c b/src/tool_setopt.c
index 690ce14a6..c854225e4 100644
--- a/src/tool_setopt.c
+++ b/src/tool_setopt.c
@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2015, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2016, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -157,6 +157,7 @@ static const NameValue setopt_nv_CURLNONZERODEFAULTS[] = {
   NV1(CURLOPT_SSL_VERIFYHOST, 1),
   NV1(CURLOPT_SSL_ENABLE_NPN, 1),
   NV1(CURLOPT_SSL_ENABLE_ALPN, 1),
+  NV1(CURLOPT_TCP_NODELAY, 1),
   NVEND
 };