net: determine if packets can be sent before net queue deliver packets

Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NZhi Yong Wu <wuzhy@linux.vnet.ibm.com>
Signed-off-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Reviewed-by: NLaszlo Ersek <lersek@redhat.com>

net/queue.c

@@ -176,8 +176,8 @@ ssize_t qemu_net_queue_send(NetQueue *queue,
 {
     ssize_t ret;
 
-    if (queue->delivering) {
-        return qemu_net_queue_append(queue, sender, flags, data, size, NULL);
+    if (queue->delivering || !qemu_can_send_packet(sender)) {
+        return qemu_net_queue_append(queue, sender, flags, data, size, sent_cb);
     }
 
     ret = qemu_net_queue_deliver(queue, sender, flags, data, size);
@@ -200,8 +200,9 @@ ssize_t qemu_net_queue_send_iov(NetQueue *queue,
 {
     ssize_t ret;
 
-    if (queue->delivering) {
-        return qemu_net_queue_append_iov(queue, sender, flags, iov, iovcnt, NULL);
+    if (queue->delivering || !qemu_can_send_packet(sender)) {
+        return qemu_net_queue_append_iov(queue, sender, flags,
+                                         iov, iovcnt, sent_cb);
     }
 
     ret = qemu_net_queue_deliver_iov(queue, sender, flags, iov, iovcnt);

net/slirp.c

@@ -97,13 +97,6 @@ static void slirp_smb_cleanup(SlirpState *s);
 static inline void slirp_smb_cleanup(SlirpState *s) { }
 #endif
 
-int slirp_can_output(void *opaque)
-{
-    SlirpState *s = opaque;
-
-    return qemu_can_send_packet(&s->nc);
-}
-
 void slirp_output(void *opaque, const uint8_t *pkt, int pkt_len)
 {
     SlirpState *s = opaque;

slirp/if.c

@@ -177,11 +177,6 @@ void if_start(Slirp *slirp)
     }
 
     while (ifm_next) {
-        /* check if we can really output */
-        if (!slirp_can_output(slirp->opaque)) {
-            break;
-        }
-
         ifm = ifm_next;
         from_batchq = next_from_batchq;
 

slirp/libslirp.h

@@ -25,7 +25,6 @@ void slirp_select_poll(fd_set *readfds, fd_set *writefds, fd_set *xfds,
 void slirp_input(Slirp *slirp, const uint8_t *pkt, int pkt_len);
 
 /* you must provide the following functions: */
-int slirp_can_output(void *opaque);
 void slirp_output(void *opaque, const uint8_t *pkt, int pkt_len);
 
 int slirp_add_hostfwd(Slirp *slirp, int is_udp,