[RFC PATCH v1 01/26] chardev: tcp: allow to change the reconnect timer

[Adalbert Lazăr]

When the introspected VM is paused/suspended/migrated, the introspection
tool removes its hooks from the guest and closes the connection.
This is detected by KVM, which in turn will clean the introspection
structures. Thanks to the reconnect parameter, the chardev will reconnect
with the introspection tool, which will try to hook the VM again,
assuming that the pause/suspend/migration operation has ended.

With this new feature, we can suspend the reconnection.

CC: "Marc-André Lureau" <address@hidden>
CC: Paolo Bonzini <address@hidden>
Signed-off-by: Adalbert Lazăr <address@hidden>
---
 chardev/char-fe.c         | 11 +++++++++++
 chardev/char-socket.c     | 14 ++++++++++++++
 include/chardev/char-fe.h |  7 +++++++
 include/chardev/char.h    |  1 +
 4 files changed, 33 insertions(+)

diff --git a/chardev/char-fe.c b/chardev/char-fe.c
index f3530a90e6..ac83528078 100644
--- a/chardev/char-fe.c
+++ b/chardev/char-fe.c
@@ -384,3 +384,14 @@ void qemu_chr_fe_disconnect(CharBackend *be)
         CHARDEV_GET_CLASS(chr)->chr_disconnect(chr);
     }
 }
+
+int qemu_chr_fe_reconnect_time(CharBackend *be, int secs)
+{
+    Chardev *chr = be->chr;
+
+    if (chr && CHARDEV_GET_CLASS(chr)->chr_reconnect_time) {
+        return CHARDEV_GET_CLASS(chr)->chr_reconnect_time(chr, secs);
+    }
+
+    return -1;
+}
diff --git a/chardev/char-socket.c b/chardev/char-socket.c
index 185fe38dda..bd966aace1 100644
--- a/chardev/char-socket.c
+++ b/chardev/char-socket.c
@@ -1471,6 +1471,19 @@ char_socket_get_connected(Object *obj, Error **errp)
     return s->state == TCP_CHARDEV_STATE_CONNECTED;
 }
 
+static int tcp_chr_reconnect_time(Chardev *chr, int secs)
+{
+    SocketChardev *s = SOCKET_CHARDEV(chr);
+
+    int old = s->reconnect_time;
+
+    if (secs >= 0) {
+        s->reconnect_time = secs;
+    }
+
+    return old;
+}
+
 static void char_socket_class_init(ObjectClass *oc, void *data)
 {
     ChardevClass *cc = CHARDEV_CLASS(oc);
@@ -1481,6 +1494,7 @@ static void char_socket_class_init(ObjectClass *oc, void 
*data)
     cc->chr_write = tcp_chr_write;
     cc->chr_sync_read = tcp_chr_sync_read;
     cc->chr_disconnect = tcp_chr_disconnect;
+    cc->chr_reconnect_time = tcp_chr_reconnect_time;
     cc->get_msgfds = tcp_get_msgfds;
     cc->set_msgfds = tcp_set_msgfds;
     cc->chr_add_client = tcp_chr_add_client;
diff --git a/include/chardev/char-fe.h b/include/chardev/char-fe.h
index a553843364..ff1897040a 100644
--- a/include/chardev/char-fe.h
+++ b/include/chardev/char-fe.h
@@ -135,6 +135,13 @@ void qemu_chr_fe_accept_input(CharBackend *be);
  */
 void qemu_chr_fe_disconnect(CharBackend *be);
 
+/**
+ * qemu_chr_fe_reconnect_time:
+ *
+ * Change the reconnect time and return the old value.
+ */
+int qemu_chr_fe_reconnect_time(CharBackend *be, int secs);
+
 /**
  * qemu_chr_fe_wait_connected:
  *
diff --git a/include/chardev/char.h b/include/chardev/char.h
index 00589a6025..80204d43ae 100644
--- a/include/chardev/char.h
+++ b/include/chardev/char.h
@@ -270,6 +270,7 @@ typedef struct ChardevClass {
     int (*chr_add_client)(Chardev *chr, int fd);
     int (*chr_wait_connected)(Chardev *chr, Error **errp);
     void (*chr_disconnect)(Chardev *chr);
+    int (*chr_reconnect_time)(Chardev *be, int secs);
     void (*chr_accept_input)(Chardev *chr);
     void (*chr_set_echo)(Chardev *chr, bool echo);
     void (*chr_set_fe_open)(Chardev *chr, int fe_open);