TCP_DEFER_ACCEPT Allow a listener to be awakened only when data arrives on the socket. If TCP_DEFER_ACCEPT set on a server-side listening socket, the TCP/IP stack will not to wait for the final ACK packet and not to initiate the process until the first packet of real data has arrived. After sending the SYN/ACK, the server will then wait for a data packet from a client. Now, only three packets will be sent over the network, and the connection establishment delay will be significantly reduced. --- man/systemd.socket.xml | 16 ++++++++++++++++ src/core/dbus-socket.c | 1 + src/core/socket.c | 11 +++++++++++ src/core/socket.h | 1 + 4 files changed, 29 insertions(+)
diff --git a/man/systemd.socket.xml b/man/systemd.socket.xml index e6bbb2e..9ce94aa 100644 --- a/man/systemd.socket.xml +++ b/man/systemd.socket.xml @@ -539,6 +539,22 @@ </varlistentry> <varlistentry> + <term><varname>DeferAccept=</varname></term> + <listitem><para>Takes time (in seconds) as argument + Allow a listener to be awakened only when data arrives on the socket. + If TCP_DEFER_ACCEPT set on a server-side listening socket, + the TCP/IP stack will not to wait for the final ACK packet and not to + initiate the process until the first packet of real data has arrived. + After sending the SYN/ACK, the server will then wait for a data packet + from a client. Now, only three packets will be sent over the network, + and the connection establishment delay will be significantly reduced. + This controls the TCP_DEFER_ACCEPT socket option (see + <citerefentry><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry> + Defaults to + <option>disabled</option>.</para></listitem> + </varlistentry> + + <varlistentry> <term><varname>Priority=</varname></term> <listitem><para>Takes an integer argument controlling the priority for diff --git a/src/core/dbus-socket.c b/src/core/dbus-socket.c index f9ef7ef..1142ca5 100644 --- a/src/core/dbus-socket.c +++ b/src/core/dbus-socket.c @@ -101,6 +101,7 @@ const sd_bus_vtable bus_socket_vtable[] = { SD_BUS_PROPERTY("KeepAliveInterval", "t", bus_property_get_usec, offsetof(Socket, keep_alive_interval), SD_BUS_VTABLE_PROPERTY_CONST), SD_BUS_PROPERTY("KeepAliveProbes", "i", bus_property_get_int, offsetof(Socket, keep_alive_cnt), SD_BUS_VTABLE_PROPERTY_CONST), SD_BUS_PROPERTY("FastOpen" , "b", bus_property_get_bool, offsetof(Socket, fast_open), SD_BUS_VTABLE_PROPERTY_CONST), + SD_BUS_PROPERTY("DeferAccept" , "t", bus_property_get_usec, offsetof(Socket, defer_accept), SD_BUS_VTABLE_PROPERTY_CONST), SD_BUS_PROPERTY("Priority", "i", bus_property_get_int, offsetof(Socket, priority), SD_BUS_VTABLE_PROPERTY_CONST), SD_BUS_PROPERTY("ReceiveBuffer", "t", bus_property_get_size, offsetof(Socket, receive_buffer), SD_BUS_VTABLE_PROPERTY_CONST), SD_BUS_PROPERTY("SendBuffer", "t", bus_property_get_size, offsetof(Socket, send_buffer), SD_BUS_VTABLE_PROPERTY_CONST), diff --git a/src/core/socket.c b/src/core/socket.c index b798d4e..32cadf9 100644 --- a/src/core/socket.c +++ b/src/core/socket.c @@ -610,6 +610,11 @@ static void socket_dump(Unit *u, FILE *f, const char *prefix) { "%sKeepAliveProbes: %u\n", prefix, s->keep_alive_cnt); + if(s->defer_accept) + fprintf(f, + "%sDeferAccept: %lo\n", + prefix, s->defer_accept / USEC_PER_SEC); + LIST_FOREACH(port, p, s->ports) { if (p->type == SOCKET_SOCKET) { @@ -831,6 +836,12 @@ static void socket_apply_socket_options(Socket *s, int fd) { log_warning_unit(UNIT(s)->id, "TCP_FASTOPEN failed: %m"); } + if (s->defer_accept) { + int value = s->defer_accept / USEC_PER_SEC; + if (setsockopt(fd, SOL_TCP, TCP_DEFER_ACCEPT, &value, sizeof(value)) < 0) + log_warning_unit(UNIT(s)->id, "TCP_DEFER_ACCEPT failed: %m"); + } + if (s->broadcast) { int one = 1; if (setsockopt(fd, SOL_SOCKET, SO_BROADCAST, &one, sizeof(one)) < 0) diff --git a/src/core/socket.h b/src/core/socket.h index 9cb82fa..7452d27 100644 --- a/src/core/socket.h +++ b/src/core/socket.h @@ -104,6 +104,7 @@ struct Socket { usec_t timeout_usec; usec_t keep_alive_time; usec_t keep_alive_interval; + usec_t defer_accept; ExecCommand* exec_command[_SOCKET_EXEC_COMMAND_MAX]; ExecContext exec_context; -- 1.9.3 _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel