[PATCH v3 21/31] libxl_qmp_ev: Handle write to socket

[Anthony PERARD <anthony.perard@citrix.com>]

The libxl__ev_qmp_* will now send commands to QEMU when the socket is
ready for writes. Also stop pulling for POLLOUT events once the send
queue is empty.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
---
 tools/libxl/libxl_qmp.c | 48 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/tools/libxl/libxl_qmp.c b/tools/libxl/libxl_qmp.c
index 9b5eb8fd35..02eae1f5ce 100644
--- a/tools/libxl/libxl_qmp.c
+++ b/tools/libxl/libxl_qmp.c
@@ -1416,6 +1416,7 @@ static int ev_qmp_queue_command(libxl__gc *gc,
     out->len = len;
     out->efd = efd;
     LIBXL_TAILQ_INSERT_TAIL(&qmp->tx_buf, out, entry);
+    libxl__ev_fd_modify(gc, &qmp->efd, qmp->efd.events | POLLOUT);
 
     return 0;
 }
@@ -1568,6 +1569,46 @@ static int ev_qmp_callback_readable(libxl__egc *egc, libxl__ev_qmp_state *qmp,
     return 0;
 }
 
+static int ev_qmp_callback_writable(libxl__egc *egc,
+                                    libxl__ev_qmp_state *qmp,
+                                    int fd)
+{
+    EGC_GC;
+    libxl__qmp_tx_buf *buf;
+    int rc;
+
+    if (!qmp->ready) {
+        return 0;
+    }
+
+    if (LIBXL_TAILQ_EMPTY(&qmp->tx_buf))
+        return 0;
+
+    buf = LIBXL_TAILQ_FIRST(&qmp->tx_buf);
+
+    LOG_QMP("sending: '%.*s'", (int)buf->len, buf->buf);
+
+    if (buf->efd) {
+        int buf_fd = libxl__carefd_fd(buf->efd);
+        rc = libxl__sendmsg_fds(gc, fd, buf->buf, buf->len,
+                                1, &buf_fd, "QMP socket");
+        libxl__carefd_close(buf->efd);
+    } else {
+        rc = libxl_write_exactly(CTX, fd, buf->buf, buf->len,
+                                 "QMP command", "QMP socket");
+    }
+
+    if (rc)
+        goto out;
+
+    LIBXL_TAILQ_REMOVE(&qmp->tx_buf, buf, entry);
+    free(buf->buf);
+    free(buf);
+
+out:
+    return 1;
+}
+
 /* When the QMP client reach the conclusion that the QMP connection doesn't
  * work anymore, this function can be called to propagate the error to every
  * callback registered. And stop the client. */
@@ -1617,6 +1658,13 @@ static void ev_qmp_fd_callback(libxl__egc *egc, libxl__ev_fd *ev_fd,
             return;
         }
     }
+    if (revents & POLLOUT) {
+        int ret = ev_qmp_callback_writable(egc, qmp, fd);
+        if (ret == 0) {
+            /* nothing to write, disable it. */
+            libxl__ev_fd_modify(gc, &qmp->efd, events & ~POLLOUT);
+        }
+    }
 }
 
 static void libxl__ev_qmp_state_init(libxl__ev_qmp_state *qmp)
-- 
Anthony PERARD


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