[Qemu-devel] [PATCH v2 for-4.0 1/7] chardev: Add disconnected option for chardev socket

[elohimes@gmail.com]

From: Xie Yongji <xieyongji@baidu.com>

New option "disconnected" is added to init the chardev socket
in disconnected state. Then we can use qemu_chr_fe_wait_connected()
to connect when necessary. Now it would be used for unix domain
socket of vhost-user-blk device to support reconnect.

Suggested-by: Yury Kotov <yury-kotov@yandex-team.ru>
Signed-off-by: Xie Yongji <xieyongji@baidu.com>
Signed-off-by: Zhang Yu <zhangyu31@baidu.com>
---
 chardev/char-socket.c | 10 ++++++++++
 chardev/char.c        |  3 +++
 qapi/char.json        |  3 +++
 qemu-options.hx       | 28 ++++++++++++++++------------
 4 files changed, 32 insertions(+), 12 deletions(-)

diff --git a/chardev/char-socket.c b/chardev/char-socket.c
index eaa8e8b68f..2464d7abad 100644
--- a/chardev/char-socket.c
+++ b/chardev/char-socket.c
@@ -70,6 +70,7 @@ typedef struct {
     TCPChardevTelnetInit *telnet_init;
 
     bool is_websock;
+    bool is_disconnected;
 
     GSource *reconnect_timer;
     int64_t reconnect_time;
@@ -1000,6 +1001,7 @@ static void qmp_chardev_open_socket(Chardev *chr,
     bool is_tn3270      = sock->has_tn3270  ? sock->tn3270  : false;
     bool is_waitconnect = sock->has_wait    ? sock->wait    : false;
     bool is_websock     = sock->has_websocket ? sock->websocket : false;
+    bool is_disconnected = sock->has_disconnected ? sock->disconnected : false;
     int64_t reconnect   = sock->has_reconnect ? sock->reconnect : 0;
     QIOChannelSocket *sioc = NULL;
     SocketAddress *addr;
@@ -1072,6 +1074,10 @@ static void qmp_chardev_open_socket(Chardev *chr,
         s->reconnect_time = reconnect;
     }
 
+    if (!s->is_listen && is_disconnected) {
+        return;
+    }
+
     if (s->reconnect_time) {
         tcp_chr_connect_async(chr);
     } else {
@@ -1125,6 +1131,8 @@ static void qemu_chr_parse_socket(QemuOpts *opts, ChardevBackend *backend,
     bool is_tn3270      = qemu_opt_get_bool(opts, "tn3270", false);
     bool is_websock     = qemu_opt_get_bool(opts, "websocket", false);
     bool do_nodelay     = !qemu_opt_get_bool(opts, "delay", true);
+    bool is_disconnected = !is_listen &&
+                           qemu_opt_get_bool(opts, "disconnected", false);
     int64_t reconnect   = qemu_opt_get_number(opts, "reconnect", 0);
     const char *path = qemu_opt_get(opts, "path");
     const char *host = qemu_opt_get(opts, "host");
@@ -1176,6 +1184,8 @@ static void qemu_chr_parse_socket(QemuOpts *opts, ChardevBackend *backend,
     sock->websocket = is_websock;
     sock->has_wait = true;
     sock->wait = is_waitconnect;
+    sock->has_disconnected = true;
+    sock->disconnected = is_disconnected;
     sock->has_reconnect = qemu_opt_find(opts, "reconnect");
     sock->reconnect = reconnect;
     sock->tls_creds = g_strdup(tls_creds);
diff --git a/chardev/char.c b/chardev/char.c
index ccba36bafb..fb916eb176 100644
--- a/chardev/char.c
+++ b/chardev/char.c
@@ -862,6 +862,9 @@ QemuOptsList qemu_chardev_opts = {
         },{
             .name = "delay",
             .type = QEMU_OPT_BOOL,
+        },{
+            .name = "disconnected",
+            .type = QEMU_OPT_BOOL,
         },{
             .name = "reconnect",
             .type = QEMU_OPT_NUMBER,
diff --git a/qapi/char.json b/qapi/char.json
index 77ed847972..b634442229 100644
--- a/qapi/char.json
+++ b/qapi/char.json
@@ -258,6 +258,8 @@
 #          sockets (default: false) (Since: 2.10)
 # @websocket: enable websocket protocol on server
 #           sockets (default: false) (Since: 3.1)
+# @disconnected: init a client socket in disconnected
+#                state (default: false) (Since: 4.0)
 # @reconnect: For a client socket, if a socket is disconnected,
 #          then attempt a reconnect after the given number of seconds.
 #          Setting this to zero disables this function. (default: 0)
@@ -274,6 +276,7 @@
             '*telnet': 'bool',
             '*tn3270': 'bool',
             '*websocket': 'bool',
+            '*disconnected': 'bool',
             '*reconnect': 'int' },
   'base': 'ChardevCommon' }
 
diff --git a/qemu-options.hx b/qemu-options.hx
index df42116ecc..f9d3495dc8 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -2418,10 +2418,10 @@ DEF("chardev", HAS_ARG, QEMU_OPTION_chardev,
     "-chardev help\n"
     "-chardev null,id=id[,mux=on|off][,logfile=PATH][,logappend=on|off]\n"
     "-chardev socket,id=id[,host=host],port=port[,to=to][,ipv4][,ipv6][,nodelay][,reconnect=seconds]\n"
-    "         [,server][,nowait][,telnet][,websocket][,reconnect=seconds][,mux=on|off]\n"
-    "         [,logfile=PATH][,logappend=on|off][,tls-creds=ID] (tcp)\n"
-    "-chardev socket,id=id,path=path[,server][,nowait][,telnet][,websocket][,reconnect=seconds]\n"
-    "         [,mux=on|off][,logfile=PATH][,logappend=on|off] (unix)\n"
+    "         [,server][,nowait][,telnet][,websocket][,disconnected][,reconnect=seconds]\n"
+    "         [,mux=on|off][,logfile=PATH][,logappend=on|off][,tls-creds=ID] (tcp)\n"
+    "-chardev socket,id=id,path=path[,server][,nowait][,telnet][,websocket][,disconnected]\n"
+    "         [,reconnect=seconds][,mux=on|off][,logfile=PATH][,logappend=on|off] (unix)\n"
     "-chardev udp,id=id[,host=host],port=port[,localaddr=localaddr]\n"
     "         [,localport=localport][,ipv4][,ipv6][,mux=on|off]\n"
     "         [,logfile=PATH][,logappend=on|off]\n"
@@ -2548,7 +2548,7 @@ The available backends are:
 A void device. This device will not emit any data, and will drop any data it
 receives. The null backend does not take any options.
 
-@item -chardev socket,id=@var{id}[,@var{TCP options} or @var{unix options}][,server][,nowait][,telnet][,websocket][,reconnect=@var{seconds}][,tls-creds=@var{id}]
+@item -chardev socket,id=@var{id}[,@var{TCP options} or @var{unix options}][,server][,nowait][,telnet][,websocket][,disconnected][,reconnect=@var{seconds}][,tls-creds=@var{id}]
 
 Create a two-way stream socket, which can be either a TCP or a unix socket. A
 unix socket will be created if @option{path} is specified. Behaviour is
@@ -2565,6 +2565,9 @@ escape sequences.
 @option{websocket} specifies that the socket uses WebSocket protocol for
 communication.
 
+@option{disconnected} specifies that the non-server socket should not try
+to connect the remote during initialization.
+
 @option{reconnect} sets the timeout for reconnecting on non-server sockets when
 the remote end goes away.  qemu will delay this many seconds and then attempt
 to reconnect.  Zero disables reconnecting, and is the default.
@@ -3087,18 +3090,19 @@ telnet on port 5555 to access the QEMU port.
 localhost 5555
 @end table
 
-@item tcp:[@var{host}]:@var{port}[,@var{server}][,nowait][,nodelay][,reconnect=@var{seconds}]
+@item tcp:[@var{host}]:@var{port}[,@var{server}][,nowait][,nodelay][,disconnected]
+[,reconnect=@var{seconds}]
 The TCP Net Console has two modes of operation.  It can send the serial
 I/O to a location or wait for a connection from a location.  By default
 the TCP Net Console is sent to @var{host} at the @var{port}.  If you use
 the @var{server} option QEMU will wait for a client socket application
 to connect to the port before continuing, unless the @code{nowait}
 option was specified.  The @code{nodelay} option disables the Nagle buffering
-algorithm.  The @code{reconnect} option only applies if @var{noserver} is
-set, if the connection goes down it will attempt to reconnect at the
-given interval.  If @var{host} is omitted, 0.0.0.0 is assumed. Only
-one TCP connection at a time is accepted. You can use @code{telnet} to
-connect to the corresponding character device.
+algorithm.  If @var{noserver} is specified, the @code{disconnected} will disallow
+QEMU to connect during initialization, and the @code{reconnect} will ask QEMU
+to reconnect at the given interval when the connection goes down.  If @var{host}
+is omitted, 0.0.0.0 is assumed. Only one TCP connection at a time is accepted.
+You can use @code{telnet} to connect to the corresponding character device.
 @table @code
 @item Example to send tcp console to 192.168.0.2 port 4444
 -serial tcp:192.168.0.2:4444
@@ -3121,7 +3125,7 @@ type "send break" followed by pressing the enter key.
 The WebSocket protocol is used instead of raw tcp socket. The port acts as
 a WebSocket server. Client mode is not supported.
 
-@item unix:@var{path}[,server][,nowait][,reconnect=@var{seconds}]
+@item unix:@var{path}[,server][,nowait][,disconnected][,reconnect=@var{seconds}]
 A unix domain socket is used instead of a tcp socket.  The option works the
 same as if you had specified @code{-serial tcp} except the unix domain socket
 @var{path} is used for connections.
-- 
2.17.1