[Qemu-devel] [PATCH RFC 01/14] vhost-user: Add ability to know vhost-user backend disconnection

[marcandre.lureau@redhat.com]

From: Tetsuya Mukawa <mukawa@igel.co.jp>

Current QEMU cannot detect vhost-user backend disconnection. The
patch adds ability to know it.
To know disconnection, add watcher to detect G_IO_HUP event. When
G_IO_HUP event is detected, the disconnected socket will be read
to cause a CHR_EVENT_CLOSED.

Signed-off-by: Tetsuya Mukawa <mukawa@igel.co.jp>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 net/vhost-user.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/net/vhost-user.c b/net/vhost-user.c
index 5657992..266b54d 100644
--- a/net/vhost-user.c
+++ b/net/vhost-user.c
@@ -20,6 +20,7 @@ typedef struct VhostUserState {
     NetClientState nc;
     CharDriverState *chr;
     VHostNetState *vhost_net;
+    int watch;
 } VhostUserState;
 
 typedef struct VhostUserChardevProps {
@@ -120,6 +121,20 @@ static void net_vhost_link_down(VhostUserState *s, bool link_down)
     }
 }
 
+static gboolean net_vhost_user_watch(GIOChannel *chan, GIOCondition cond,
+                                           void *opaque)
+{
+    VhostUserState *s = opaque;
+    uint8_t buf[1];
+
+    /* We don't actually want to read anything, but CHR_EVENT_CLOSED will be
+     * raised as a side-effect of the read.
+     */
+    qemu_chr_fe_read_all(s->chr, buf, sizeof(buf));
+
+    return FALSE;
+}
+
 static void net_vhost_user_event(void *opaque, int event)
 {
     VhostUserState *s = opaque;
@@ -128,12 +143,15 @@ static void net_vhost_user_event(void *opaque, int event)
 
     switch (event) {
     case CHR_EVENT_OPENED:
+        s->watch = qemu_chr_fe_add_watch(s->chr, G_IO_HUP, net_vhost_user_watch, s);
         vhost_user_start(s);
         net_vhost_link_down(s, false);
         break;
     case CHR_EVENT_CLOSED:
         net_vhost_link_down(s, true);
         vhost_user_stop(s);
+        g_source_remove(s->watch);
+        s->watch = 0;
         break;
     }
 }
-- 
2.4.3