[PATCH vdagent-linux 2/4] vport: add @err to disconnect_callback

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This is necessary for the following GMainLoop integration:

vdagentd currently uses a while-loop in which
vdagent_virtio_port_handle_fds() is repeatedly called.
If an IO error occurs, the function sets virtio_port to NULL.
This way, we can detect when the virtio_port has been destroyed and
try to reconnect if desired. (see main_loop() in vdagentd.c)
The vdagent_virtio_port_disconnect_callback is not used.

In the following commit, the main_loop() is going to be removed and replaced
by a GMainLoop. In order to be able to detect when the virtio_port has been
destroyed, vdagent_virtio_port_disconnect_callback will have to be used.
The virtio_port should be reconnected only when an IO error happened.
However, the vdagent_virtio_port_disconnect_callback is always called,
even when the diconnect was initiated by vdagent_virtio_port_destroy().

To be able to distinguish these two cases, add @err parameter
to the vdagent_virtio_port_disconnect_callback:

1) disconnect was initiated by vdagent_virtio_port_destroy()
   --> @err is NULL
2) disconnect was caused by an IO error
   --> @err is set accordingly

Signed-off-by: Jakub Janků <jjanku@xxxxxxxxxx>
---
 src/vdagentd/virtio-port.c | 44 +++++++++++++++++++++++++-------------
 src/vdagentd/virtio-port.h |  8 +++----
 2 files changed, 32 insertions(+), 20 deletions(-)

diff --git a/src/vdagentd/virtio-port.c b/src/vdagentd/virtio-port.c
index e48d107..497811e 100644
--- a/src/vdagentd/virtio-port.c
+++ b/src/vdagentd/virtio-port.c
@@ -29,6 +29,7 @@
 #include <sys/socket.h>
 #include <sys/un.h>
 #include <glib.h>
+#include <gio/gio.h>
 
 #include "virtio-port.h"
 
@@ -120,7 +121,8 @@ error:
     return NULL;
 }
 
-void vdagent_virtio_port_destroy(struct vdagent_virtio_port **vportp)
+static void virtio_port_destroy(struct vdagent_virtio_port **vportp,
+                                GError *err)
 {
     struct vdagent_virtio_port_buf *wbuf, *next_wbuf;
     struct vdagent_virtio_port *vport = *vportp;
@@ -130,7 +132,9 @@ void vdagent_virtio_port_destroy(struct vdagent_virtio_port **vportp)
         return;
 
     if (vport->disconnect_callback)
-        vport->disconnect_callback(vport);
+        vport->disconnect_callback(vport, err);
+
+    g_clear_error(&err);
 
     wbuf = vport->write_buf;
     while (wbuf) {
@@ -148,6 +152,11 @@ void vdagent_virtio_port_destroy(struct vdagent_virtio_port **vportp)
     g_clear_pointer(vportp, g_free);
 }
 
+void vdagent_virtio_port_destroy(struct vdagent_virtio_port **vportp)
+{
+    virtio_port_destroy(vportp, NULL);
+}
+
 int vdagent_virtio_port_fill_fds(struct vdagent_virtio_port *vport,
         fd_set *readfds, fd_set *writefds)
 {
@@ -314,8 +323,9 @@ static void vdagent_virtio_port_do_chunk(struct vdagent_virtio_port **vportp)
         avail = vport->chunk_header.size - pos;
 
         if (avail > read) {
-            syslog(LOG_ERR, "chunk larger than message, lost sync?");
-            vdagent_virtio_port_destroy(vportp);
+            GError *err = g_error_new(G_IO_ERROR, G_IO_ERROR_FAILED,
+                                      "chunk larger than message, lost sync?");
+            virtio_port_destroy(vportp, err);
             return;
         }
 
@@ -333,7 +343,7 @@ static void vdagent_virtio_port_do_chunk(struct vdagent_virtio_port **vportp)
                 int r = vport->read_callback(vport, vport->chunk_header.port,
                                  &port->message_header, port->message_data);
                 if (r == -1) {
-                    vdagent_virtio_port_destroy(vportp);
+                    virtio_port_destroy(vportp, NULL);
                     return;
                 }
             }
@@ -372,7 +382,6 @@ static void vdagent_virtio_port_do_read(struct vdagent_virtio_port **vportp)
     if (n < 0) {
         if (errno == EINTR)
             return;
-        syslog(LOG_ERR, "reading from vdagent virtio port: %m");
     }
     if (n == 0 && vport->opening) {
         /* When we open the virtio serial port, the following happens:
@@ -399,7 +408,9 @@ static void vdagent_virtio_port_do_read(struct vdagent_virtio_port **vportp)
         return;
     }
     if (n <= 0) {
-        vdagent_virtio_port_destroy(vportp);
+        GError *err = g_error_new(G_IO_ERROR, G_IO_ERROR_FAILED,
+                                  "reading from vdagent virtio port: %m");
+        virtio_port_destroy(vportp, err);
         return;
     }
     vport->opening = 0;
@@ -410,15 +421,17 @@ static void vdagent_virtio_port_do_read(struct vdagent_virtio_port **vportp)
             vport->chunk_header.size = GUINT32_FROM_LE(vport->chunk_header.size);
             vport->chunk_header.port = GUINT32_FROM_LE(vport->chunk_header.port);
             if (vport->chunk_header.size > VD_AGENT_MAX_DATA_SIZE) {
-                syslog(LOG_ERR, "chunk size %u too large",
-                       vport->chunk_header.size);
-                vdagent_virtio_port_destroy(vportp);
+                GError *err = g_error_new(G_IO_ERROR, G_IO_ERROR_FAILED,
+                                          "chunk size %u too large",
+                                          vport->chunk_header.size);
+                virtio_port_destroy(vportp, err);
                 return;
             }
             if (vport->chunk_header.port >= VDP_END_PORT) {
-                syslog(LOG_ERR, "chunk port %u out of range",
-                       vport->chunk_header.port);
-                vdagent_virtio_port_destroy(vportp);
+                GError *err = g_error_new(G_IO_ERROR, G_IO_ERROR_FAILED,
+                                          "chunk port %u out of range",
+                                          vport->chunk_header.port);
+                virtio_port_destroy(vportp, err);
                 return;
             }
         }
@@ -465,8 +478,9 @@ static void vdagent_virtio_port_do_write(struct vdagent_virtio_port **vportp)
     if (n < 0) {
         if (errno == EINTR)
             return;
-        syslog(LOG_ERR, "writing to vdagent virtio port: %m");
-        vdagent_virtio_port_destroy(vportp);
+        GError *err = g_error_new(G_IO_ERROR, G_IO_ERROR_FAILED,
+                                  "writing to vdagent virtio port: %m");
+        virtio_port_destroy(vportp, err);
         return;
     }
     if (n > 0)
diff --git a/src/vdagentd/virtio-port.h b/src/vdagentd/virtio-port.h
index dffb410..dfbe27b 100644
--- a/src/vdagentd/virtio-port.h
+++ b/src/vdagentd/virtio-port.h
@@ -41,14 +41,12 @@ typedef int (*vdagent_virtio_port_read_callback)(
     uint8_t *data);
 
 /* Callbacks with this type will be called when the port is disconnected.
+   If the virtio port was disconnected due to an IO error, @err is set.
    Note:
    1) vdagent_virtio_port will destroy the port in question itself after
-      this callback has completed!
-   2) This callback is always called, even if the disconnect is initiated
-      by the vdagent_virtio_port user through returning -1 from a read
-      callback, or by explicitly calling vdagent_virtio_port_destroy */
+      this callback has completed! */
 typedef void (*vdagent_virtio_port_disconnect_callback)(
-    struct vdagent_virtio_port *conn);
+    struct vdagent_virtio_port *conn, GError *err);
 
 
 /* Create a vdagent virtio port object for port portname */
-- 
2.17.1

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