From 262544a451c11c38e92c45047ec2adeaeb2a0a7e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Renaud=20M=C3=A9trich?= <rmetrich@redhat.com>
Date: Thu, 20 Aug 2020 13:00:37 +0200
Subject: [PATCH] socket: New option 'FlushPending' (boolean) to flush socket
before entering listening state
Disabled by default. When Enabled, before listening on the socket, flush the content.
Applies when Accept=no only.
(cherry picked from commit 3e5f04bf6468fcb79c080f02b0eab08f258bff0c)
Resolves: #1870638
---
doc/TRANSIENT-SETTINGS.md | 1 +
man/systemd.socket.xml | 12 ++++++++++++
src/core/dbus-socket.c | 4 ++++
src/core/load-fragment-gperf.gperf.m4 | 1 +
src/core/socket.c | 11 +++++++++++
src/core/socket.h | 1 +
src/shared/bus-unit-util.c | 3 ++-
7 files changed, 32 insertions(+), 1 deletion(-)
diff --git a/doc/TRANSIENT-SETTINGS.md b/doc/TRANSIENT-SETTINGS.md
index 1a4e79190a..995b8797ef 100644
--- a/doc/TRANSIENT-SETTINGS.md
+++ b/doc/TRANSIENT-SETTINGS.md
@@ -388,6 +388,7 @@ Most socket unit settings are available to transient units.
✓ SocketMode=
✓ DirectoryMode=
✓ Accept=
+✓ FlushPending=
✓ Writable=
✓ MaxConnections=
✓ MaxConnectionsPerSource=
diff --git a/man/systemd.socket.xml b/man/systemd.socket.xml
index 19c2ca9907..8676b4e03f 100644
--- a/man/systemd.socket.xml
+++ b/man/systemd.socket.xml
@@ -425,6 +425,18 @@
false, in read-only mode. Defaults to false.</para></listitem>
</varlistentry>
+ <varlistentry>
+ <term><varname>FlushPending=</varname></term>
+ <listitem><para>Takes a boolean argument. May only be used when
+ <option>Accept=no</option>. If yes, the socket's buffers are cleared after the
+ triggered service exited. This causes any pending data to be
+ flushed and any pending incoming connections to be rejected. If no, the
+ socket's buffers won't be cleared, permitting the service to handle any
+ pending connections after restart, which is the usually expected behaviour.
+ Defaults to <option>no</option>.
+ </para></listitem>
+ </varlistentry>
+
<varlistentry>
<term><varname>MaxConnections=</varname></term>
<listitem><para>The maximum number of connections to
diff --git a/src/core/dbus-socket.c b/src/core/dbus-socket.c
index 913cc74918..bb77539030 100644
--- a/src/core/dbus-socket.c
+++ b/src/core/dbus-socket.c
@@ -85,6 +85,7 @@ const sd_bus_vtable bus_socket_vtable[] = {
SD_BUS_PROPERTY("SocketMode", "u", bus_property_get_mode, offsetof(Socket, socket_mode), SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("DirectoryMode", "u", bus_property_get_mode, offsetof(Socket, directory_mode), SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("Accept", "b", bus_property_get_bool, offsetof(Socket, accept), SD_BUS_VTABLE_PROPERTY_CONST),
+ SD_BUS_PROPERTY("FlushPending", "b", bus_property_get_bool, offsetof(Socket, flush_pending), SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("Writable", "b", bus_property_get_bool, offsetof(Socket, writable), SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("KeepAlive", "b", bus_property_get_bool, offsetof(Socket, keep_alive), SD_BUS_VTABLE_PROPERTY_CONST),
SD_BUS_PROPERTY("KeepAliveTimeUSec", "t", bus_property_get_usec, offsetof(Socket, keep_alive_time), SD_BUS_VTABLE_PROPERTY_CONST),
@@ -177,6 +178,9 @@ static int bus_socket_set_transient_property(
if (streq(name, "Accept"))
return bus_set_transient_bool(u, name, &s->accept, message, flags, error);
+ if (streq(name, "FlushPending"))
+ return bus_set_transient_bool(u, name, &s->flush_pending, message, flags, error);
+
if (streq(name, "Writable"))
return bus_set_transient_bool(u, name, &s->writable, message, flags, error);
diff --git a/src/core/load-fragment-gperf.gperf.m4 b/src/core/load-fragment-gperf.gperf.m4
index 6d21b2e433..24ee5ae6fe 100644
--- a/src/core/load-fragment-gperf.gperf.m4
+++ b/src/core/load-fragment-gperf.gperf.m4
@@ -359,6 +359,7 @@ Socket.SocketGroup, config_parse_user_group, 0,
Socket.SocketMode, config_parse_mode, 0, offsetof(Socket, socket_mode)
Socket.DirectoryMode, config_parse_mode, 0, offsetof(Socket, directory_mode)
Socket.Accept, config_parse_bool, 0, offsetof(Socket, accept)
+Socket.FlushPending, config_parse_bool, 0, offsetof(Socket, flush_pending)
Socket.Writable, config_parse_bool, 0, offsetof(Socket, writable)
Socket.MaxConnections, config_parse_unsigned, 0, offsetof(Socket, max_connections)
Socket.MaxConnectionsPerSource, config_parse_unsigned, 0, offsetof(Socket, max_connections_per_source)
diff --git a/src/core/socket.c b/src/core/socket.c
index fe061eb73b..97c3a7fc9a 100644
--- a/src/core/socket.c
+++ b/src/core/socket.c
@@ -70,6 +70,7 @@ static const UnitActiveState state_translation_table[_SOCKET_STATE_MAX] = {
static int socket_dispatch_io(sd_event_source *source, int fd, uint32_t revents, void *userdata);
static int socket_dispatch_timer(sd_event_source *source, usec_t usec, void *userdata);
+static void flush_ports(Socket *s);
static void socket_init(Unit *u) {
Socket *s = SOCKET(u);
@@ -703,6 +704,11 @@ static void socket_dump(Unit *u, FILE *f, const char *prefix) {
prefix, s->n_connections,
prefix, s->max_connections,
prefix, s->max_connections_per_source);
+ else
+ fprintf(f,
+ "%sFlushPending: %s\n",
+ prefix, yes_no(s->flush_pending));
+
if (s->priority >= 0)
fprintf(f,
@@ -2111,6 +2117,11 @@ static void socket_enter_listening(Socket *s) {
int r;
assert(s);
+ if (!s->accept && s->flush_pending) {
+ log_unit_debug(UNIT(s), "Flushing socket before listening.");
+ flush_ports(s);
+ }
+
r = socket_watch_fds(s);
if (r < 0) {
log_unit_warning_errno(UNIT(s), r, "Failed to watch sockets: %m");
diff --git a/src/core/socket.h b/src/core/socket.h
index c4e25db1fc..b7a25d91fd 100644
--- a/src/core/socket.h
+++ b/src/core/socket.h
@@ -109,6 +109,7 @@ struct Socket {
bool accept;
bool remove_on_stop;
bool writable;
+ bool flush_pending;
int socket_protocol;
diff --git a/src/shared/bus-unit-util.c b/src/shared/bus-unit-util.c
index 77788f0fe2..7029aa5615 100644
--- a/src/shared/bus-unit-util.c
+++ b/src/shared/bus-unit-util.c
@@ -1468,7 +1468,8 @@ static int bus_append_socket_property(sd_bus_message *m, const char *field, cons
if (STR_IN_SET(field,
"Accept", "Writable", "KeepAlive", "NoDelay", "FreeBind", "Transparent", "Broadcast",
- "PassCredentials", "PassSecurity", "ReusePort", "RemoveOnStop", "SELinuxContextFromNet"))
+ "PassCredentials", "PassSecurity", "ReusePort", "RemoveOnStop", "SELinuxContextFromNet",
+ "FlushPending"))
return bus_append_parse_boolean(m, field, eq);