[Qemu-devel] [PATCH 02/16] qemu-char: Allow a chardev to reconnect if disconnected

[Corey Minyard]

Allow a socket that connects to reconnect on a periodic basis if it
fails to connect at startup or if the connection drops while in use.

Signed-off-by: Corey Minyard <address@hidden>
---
 include/sysemu/char.h |  3 ++
 qemu-char.c           | 88 ++++++++++++++++++++++++++++++++++++++++++++-------
 qemu-options.hx       | 11 +++++--
 3 files changed, 87 insertions(+), 15 deletions(-)

diff --git a/include/sysemu/char.h b/include/sysemu/char.h
index 44baf0f..3d21b5a 100644
--- a/include/sysemu/char.h
+++ b/include/sysemu/char.h
@@ -81,6 +81,9 @@ struct CharDriverState {
     guint fd_in_tag;
     QemuOpts *opts;
     QTAILQ_ENTRY(CharDriverState) next;
+    GSList *backend;
+    QEMUTimer *recon_timer;
+    uint64_t recon_time;
 };
 
 /**
diff --git a/qemu-char.c b/qemu-char.c
index dd04cc0..23d7647 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -96,9 +96,22 @@ void qemu_chr_be_event(CharDriverState *s, int event)
     /* Keep track if the char device is open */
     switch (event) {
         case CHR_EVENT_OPENED:
+            if (s->recon_timer) {
+                timer_del(s->recon_timer);
+            }
             s->be_open = 1;
             break;
         case CHR_EVENT_CLOSED:
+            if (s->recon_timer) {
+                void (*chr_close)(struct CharDriverState *chr) = s->chr_close;
+                if (chr_close) {
+                    s->chr_close = NULL;
+                    chr_close(s);
+                }
+                timer_mod(s->recon_timer,
+                         (get_clock() +
+                          (s->recon_time * get_ticks_per_sec())));
+            }
             s->be_open = 0;
             break;
     }
@@ -2583,6 +2596,7 @@ static void tcp_chr_close(CharDriverState *chr)
         closesocket(s->listen_fd);
     }
     g_free(s);
+    chr->opaque = NULL;
     qemu_chr_be_event(chr, CHR_EVENT_CLOSED);
 }
 
@@ -2642,8 +2656,6 @@ static CharDriverState 
*qemu_chr_open_socket_fd(CharDriverState *chr,
     chr->get_msgfd = tcp_get_msgfd;
     chr->chr_add_client = tcp_chr_add_client;
     chr->chr_add_watch = tcp_chr_add_watch;
-    /* be isn't opened until we get a connection */
-    chr->explicit_be_open = true;
 
     if (is_listen) {
         s->listen_fd = fd;
@@ -2681,6 +2693,9 @@ static CharDriverState 
*qemu_chr_open_socket(CharDriverState *chr,
     bool do_nodelay     = !qemu_opt_get_bool(opts, "delay", true);
     bool is_unix        = qemu_opt_get(opts, "path") != NULL;
 
+    /* be isn't opened until we get a connection */
+    chr->explicit_be_open = true;
+
     if (is_unix) {
         if (is_listen) {
             fd = unix_listen_opts(opts, &local_err);
@@ -2717,8 +2732,9 @@ static CharDriverState 
*qemu_chr_open_socket(CharDriverState *chr,
     if (fd >= 0) {
         closesocket(fd);
     }
-    if (chr) {
+    if (chr && chr->opaque) {
         g_free(chr->opaque);
+        chr->opaque = NULL;
     }
     return NULL;
 }
@@ -3163,6 +3179,20 @@ void register_char_driver_qapi(const char *name, 
ChardevBackendKind kind,
     backends = g_slist_append(backends, s);
 }
 
+static void recon_timeout(void *opaque)
+{
+    CharDriverState *chr = opaque;
+    CharDriver *cd = chr->backend->data;
+
+    if (chr->be_open) {
+        return;
+    }
+
+    timer_mod(chr->recon_timer,
+             (get_clock() + (chr->recon_time * get_ticks_per_sec())));
+    cd->open(chr, chr->opts);
+}
+
 CharDriverState *qemu_chr_new_from_opts(QemuOpts *opts,
                                     void (*init)(struct CharDriverState *s),
                                     Error **errp)
@@ -3245,11 +3275,36 @@ CharDriverState *qemu_chr_new_from_opts(QemuOpts *opts,
     }
 
     chr = g_malloc0(sizeof(CharDriverState));
-    chr = cd->open(chr, opts);
-    if (!chr) {
-        error_setg(errp, "chardev: opening backend \"%s\" failed",
-                   qemu_opt_get(opts, "backend"));
-        goto err;
+
+    chr->backend = i;
+    chr->recon_time = qemu_opt_get_number(opts, "reconnect", 0);
+    if (chr->recon_time) {
+        if (strcmp(qemu_opt_get(opts, "backend"), "socket") != 0) {
+            g_free(chr);
+            fprintf(stderr, "chardev: reconnect only supported on sockets\n");
+            return NULL;
+        }
+        if (qemu_opt_get_bool(opts, "server", 0)) {
+            g_free(chr);
+            fprintf(stderr, "chardev: server device cannot reconnect\n");
+            return NULL;
+        }
+        chr->opts = opts;
+        chr->recon_timer = timer_new(QEMU_CLOCK_REALTIME, SCALE_NS,
+                                    recon_timeout, chr);
+
+        /* Make sure it connects in time. */
+        timer_mod(chr->recon_timer,
+                 (get_clock() + (chr->recon_time * get_ticks_per_sec())));
+    }
+
+    if (!cd->open(chr, opts)) {
+        if (!chr->recon_time) {
+            /* Reconnect is not enabled, give up */
+            fprintf(stderr, "chardev: opening backend \"%s\" failed\n",
+                    qemu_opt_get(opts, "backend"));
+            return NULL;
+        }
     }
 
     if (!chr->filename)
@@ -3268,7 +3323,8 @@ CharDriverState *qemu_chr_new_from_opts(QemuOpts *opts,
         int len = strlen(qemu_opts_id(opts)) + 6;
         base->label = g_malloc(len);
         snprintf(base->label, len, "%s-base", qemu_opts_id(opts));
-        chr = qemu_chr_open_mux(chr, base);
+        chr = g_malloc0(sizeof(CharDriverState));
+        qemu_chr_open_mux(chr, base);
         chr->filename = base->filename;
         chr->avail_connections = MAX_MUX;
         QTAILQ_INSERT_TAIL(&chardevs, chr, next);
@@ -3276,7 +3332,6 @@ CharDriverState *qemu_chr_new_from_opts(QemuOpts *opts,
         chr->avail_connections = 1;
     }
     chr->label = g_strdup(qemu_opts_id(opts));
-    chr->opts = opts;
     return chr;
 
 err:
@@ -3372,9 +3427,15 @@ void qemu_chr_fe_release(CharDriverState *s)
 
 void qemu_chr_delete(CharDriverState *chr)
 {
+    void (*chr_close)(struct CharDriverState *chr) = chr->chr_close;
+
     QTAILQ_REMOVE(&chardevs, chr, next);
-    if (chr->chr_close) {
-        chr->chr_close(chr);
+    if (chr_close) {
+        chr->chr_close = NULL;
+        chr_close(chr);
+    }
+    if (chr->recon_timer) {
+        timer_free(chr->recon_timer);
     }
     g_free(chr->filename);
     g_free(chr->label);
@@ -3490,6 +3551,9 @@ QemuOptsList qemu_chardev_opts = {
             .name = "mux",
             .type = QEMU_OPT_BOOL,
         },{
+            .name = "reconnect",
+            .type = QEMU_OPT_NUMBER,
+        },{
             .name = "signal",
             .type = QEMU_OPT_BOOL,
         },{
diff --git a/qemu-options.hx b/qemu-options.hx
index 5dc8b75..5bcfaa0 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -1780,8 +1780,9 @@ ETEXI
 DEF("chardev", HAS_ARG, QEMU_OPTION_chardev,
     "-chardev null,id=id[,mux=on|off]\n"
     "-chardev 
socket,id=id[,host=host],port=host[,to=to][,ipv4][,ipv6][,nodelay]\n"
-    "         [,server][,nowait][,telnet][,mux=on|off] (tcp)\n"
-    "-chardev socket,id=id,path=path[,server][,nowait][,telnet],[mux=on|off] 
(unix)\n"
+    "         [,server][,nowait][,telnet][,mux=on|off][,reconnect=seconds] 
(tcp)\n"
+    "-chardev socket,id=id,path=path[,server][,nowait][,telnet][,mux=on|off]\n"
+    "         [,reconnect=seconds] (unix)\n"
     "-chardev udp,id=id[,host=host],port=port[,localaddr=localaddr]\n"
     "         [,localport=localport][,ipv4][,ipv6][,mux=on|off]\n"
     "-chardev msmouse,id=id[,mux=on|off]\n"
@@ -1853,7 +1854,7 @@ Options to each backend are described below.
 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.
 
address@hidden -chardev socket ,address@hidden address@hidden options} or 
@var{unix options}] [,server] [,nowait] [,telnet]
address@hidden -chardev socket ,address@hidden address@hidden options} or 
@var{unix options}] [,server] [,nowait] [,telnet] [,address@hidden
 
 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
@@ -1867,6 +1868,10 @@ connect to a listening socket.
 @option{telnet} specifies that traffic on the socket should interpret telnet
 escape sequences.
 
address@hidden specifies that if the socket does not come up at startup,
+or if the socket is closed for some reason (like the other end exited),
+wait the given number of seconds and attempt to reconnect.
+
 TCP and unix socket options are given below:
 
 @table @option
-- 
1.8.3.1