10:37 a.m.
Since NBD makes several TCP connections (especially if using
multi-conn, as you should), it may benefit from using TFO on platforms
which support it. This commit simply adds new command line options
for enabling and disabling the flag, a way to fetch the default from
--dump-plugin, and updates the documentation.
It does not (yet) implement the feature.
I found these articles about TFO interesting:
https://blog.apnic.net/2021/07/05/tcp-fast-open-not-so-fast/
https://candrews.integralblue.com/2019/03/the-sad-story-of-tcp-fast-open/
---
docs/nbdkit.pod | 23 ++++++++++++++++++++
docs/synopsis.txt | 1 +
tests/Makefile.am | 2 ++
server/internal.h | 1 +
server/options.h | 4 ++++
server/main.c | 11 ++++++++++
tests/test-tfo-default.sh | 46 +++++++++++++++++++++++++++++++++++++++
7 files changed, 88 insertions(+)
diff --git a/docs/nbdkit.pod b/docs/nbdkit.pod
index b088d4ef19..5b7b87741d 100644
--- a/docs/nbdkit.pod
+++ b/docs/nbdkit.pod
@@ -476,6 +476,29 @@ may require additional permissions, such as starting the server as
root or raising the C<RLIMIT_MEMLOCK> (L<ulimit(1)> I<-l>) limit on
the process.
+=item B<--tfo>
+
+=item B<--no-tfo>
+
+Enable or disable TCP fastopen (TFO). When enabled, this allows
+faster connections over TCP by omitting part of the TCP 3-way handshake.
+
+It is not supported for non-IP sockets (like Unix domain sockets).
+The platform must also enable TFO. On Linux you must set
+sysctl C<net.ipv4.tcp_fastopen> = 1.
+
+Currently only libnbd E<ge> 1.22 implements client side support
+for TCP fastopen.
+
+The default is not specified and may depend on the platform and
+version of nbdkit. You can find the default for the current version
+of nbdkit using:
+
+ $ nbdkit --dump-config | grep ^tfo
+ tfo_default=1
+
+(or C<tfo_default=0>).
+
=item B<-t> THREADS
=item B<--threads=>THREADS
diff --git a/docs/synopsis.txt b/docs/synopsis.txt
index ecbc6d5c50..ad55dc108b 100644
--- a/docs/synopsis.txt
+++ b/docs/synopsis.txt
@@ -9,6 +9,7 @@ nbdkit [-4|--ipv4-only] [-6|--ipv6-only]
[-P|--pidfile PIDFILE] [-p|--port PORT] [--print-uri]
[-r|--readonly] [--run 'COMMAND ARGS ...']
[--selinux-label=LABEL] [-s|--single] [--swap]
+ [--tfo|--no-tfo]
[-t|--threads THREADS] [--timeout=TIMEOUT]
[--tls=off|on|require]
[--tls-certificates=/path/to/certificates]
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 29c762b636..4bf9a4568f 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -312,6 +312,7 @@ TESTS += \
test-timeout.sh \
test-timeout-cancel.sh \
test-keepalive.sh \
+ test-tfo-default.sh \
$(NULL)
if !IS_WINDOWS
TESTS += \
@@ -369,6 +370,7 @@ EXTRA_DIST += \
test-start.sh \
test-stdio.sh \
test-swap.sh \
+ test-tfo-default.sh \
test-timeout.sh \
test-timeout.py \
test-timeout-cancel.sh \
diff --git a/server/internal.h b/server/internal.h
index fb838c60d8..4413acecfb 100644
--- a/server/internal.h
+++ b/server/internal.h
@@ -125,6 +125,7 @@ extern const char *service_mode_string (enum service_mode);
extern int tcpip_sock_af;
extern struct debug_flag *debug_flags;
extern const char *export_name;
+extern bool fastopen;
extern bool foreground;
extern const char *ipaddr;
extern bool keepalive;
diff --git a/server/options.h b/server/options.h
index 0bc8207caf..48c37be880 100644
--- a/server/options.h
+++ b/server/options.h
@@ -43,11 +43,13 @@ enum {
DUMP_CONFIG_OPTION,
DUMP_PLUGIN_OPTION,
EXIT_WITH_PARENT_OPTION,
+ FASTOPEN_OPTION,
FILTER_OPTION,
KEEPALIVE_OPTION,
LOG_OPTION,
LONG_OPTIONS_OPTION,
MASK_HANDSHAKE_OPTION,
+ NO_FASTOPEN_OPTION,
NO_MC_OPTION,
NO_SR_OPTION,
PRINT_URI,
@@ -92,6 +94,7 @@ static const struct option long_options[] = {
{ "no-meta-contexts", no_argument, NULL, NO_MC_OPTION },
{ "no-sr", no_argument, NULL, NO_SR_OPTION },
{ "no-structured-replies", no_argument, NULL, NO_SR_OPTION },
+ { "no-tfo", no_argument, NULL, NO_FASTOPEN_OPTION },
{ "old-style", no_argument, NULL, 'o' },
{ "oldstyle", no_argument, NULL, 'o' },
{ "pid-file", required_argument, NULL, 'P' },
@@ -109,6 +112,7 @@ static const struct option long_options[] = {
{ "single", no_argument, NULL, 's' },
{ "stdin", no_argument, NULL, 's' },
{ "swap", no_argument, NULL, SWAP_OPTION },
+ { "tfo", no_argument, NULL, FASTOPEN_OPTION },
{ "threads", required_argument, NULL, 't' },
{ "timeout", required_argument, NULL, TIMEOUT_OPTION },
{ "time-out", required_argument, NULL, TIMEOUT_OPTION },
diff --git a/server/main.c b/server/main.c
index 0b558698cb..d6e93a67ff 100644
--- a/server/main.c
+++ b/server/main.c
@@ -80,6 +80,8 @@
#define main fuzzer_main
#endif
+#define FASTOPEN_DEFAULT 0
+
static char *make_random_fifo (void);
static struct backend *open_plugin_so (size_t i, const char *filename,
int short_name);
@@ -96,6 +98,7 @@ int tcpip_sock_af = AF_UNSPEC; /* -4, -6 */
struct debug_flag *debug_flags; /* -D */
bool exit_with_parent; /* --exit-with-parent */
const char *export_name; /* -e */
+bool fastopen = FASTOPEN_DEFAULT; /* --tfo, --no-tfo */
bool foreground; /* -f */
const char *ipaddr; /* -i */
bool keepalive; /* --keepalive */
@@ -224,6 +227,7 @@ dump_config (void)
#endif
printf ("%s=%s\n", "soext", SOEXT);
printf ("%s=%s\n", "sysconfdir", sysconfdir);
+ printf ("%s=%d\n", "tfo_default", FASTOPEN_DEFAULT);
#ifdef HAVE_GNUTLS
printf ("tls=yes\n");
#else
@@ -326,6 +330,13 @@ main (int argc, char *argv[])
}
break;
+ case FASTOPEN_OPTION:
+ fastopen = true;
+ break;
+ case NO_FASTOPEN_OPTION:
+ fastopen = false;
+ break;
+
case FILTER_OPTION:
{
struct filter_filename *t;
diff --git a/tests/test-tfo-default.sh b/tests/test-tfo-default.sh
new file mode 100755
index 0000000000..7ca35166fe
--- /dev/null
+++ b/tests/test-tfo-default.sh
@@ -0,0 +1,46 @@
+#!/usr/bin/env bash
+# nbdkit
+# Copyright Red Hat
+#
+# 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.
+#
+# * Neither the name of Red Hat nor the names of its contributors may be
+# used to endorse or promote products derived from this software without
+# specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY RED HAT 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 RED HAT 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.
+
+# Test the --dump-plugin / tfo_default setting.
+
+source ./functions.sh
+set -e
+set -x
+
+out=tfo-default.out
+rm -f $out
+cleanup_fn rm -f $out
+
+nbdkit --dump-config > $out
+# Check the key is present and the format is correct. We do
+# not know what the default will be.
+grep "^tfo_default=[01]$" $out
--
2.46.0