[Qemu-devel] [PATCH] net: do not report queued packets as sent

[Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>]

Net send functions have a return value where 0 means the packet has not
been sent and will be queued.  A non-zero value means the packet was
sent or an error caused the packet to be dropped.

This patch fixes two instances where packets are queued but we return
their size.  This causes callers to believe the packets were sent.  When
the caller uses the async send interface this creates a real problem
because the callback will be invoked for a packet that the caller
believed to be already sent.  This bug can cause double-frees in the
caller.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 net/queue.c |   35 ++++++++++++++++-------------------
 1 file changed, 16 insertions(+), 19 deletions(-)

diff --git a/net/queue.c b/net/queue.c
index e8030aa..308a455 100644
--- a/net/queue.c
+++ b/net/queue.c
@@ -83,12 +83,12 @@ void qemu_del_net_queue(NetQueue *queue)
     g_free(queue);
 }
 
-static ssize_t qemu_net_queue_append(NetQueue *queue,
-                                     NetClientState *sender,
-                                     unsigned flags,
-                                     const uint8_t *buf,
-                                     size_t size,
-                                     NetPacketSent *sent_cb)
+static void qemu_net_queue_append(NetQueue *queue,
+                                  NetClientState *sender,
+                                  unsigned flags,
+                                  const uint8_t *buf,
+                                  size_t size,
+                                  NetPacketSent *sent_cb)
 {
     NetPacket *packet;
 
@@ -100,16 +100,14 @@ static ssize_t qemu_net_queue_append(NetQueue *queue,
     memcpy(packet->data, buf, size);
 
     QTAILQ_INSERT_TAIL(&queue->packets, packet, entry);
-
-    return size;
 }
 
-static ssize_t qemu_net_queue_append_iov(NetQueue *queue,
-                                         NetClientState *sender,
-                                         unsigned flags,
-                                         const struct iovec *iov,
-                                         int iovcnt,
-                                         NetPacketSent *sent_cb)
+static void qemu_net_queue_append_iov(NetQueue *queue,
+                                      NetClientState *sender,
+                                      unsigned flags,
+                                      const struct iovec *iov,
+                                      int iovcnt,
+                                      NetPacketSent *sent_cb)
 {
     NetPacket *packet;
     size_t max_len = 0;
@@ -133,8 +131,6 @@ static ssize_t qemu_net_queue_append_iov(NetQueue *queue,
     }
 
     QTAILQ_INSERT_TAIL(&queue->packets, packet, entry);
-
-    return packet->size;
 }
 
 static ssize_t qemu_net_queue_deliver(NetQueue *queue,
@@ -177,7 +173,8 @@ ssize_t qemu_net_queue_send(NetQueue *queue,
     ssize_t ret;
 
     if (queue->delivering || !qemu_can_send_packet(sender)) {
-        return qemu_net_queue_append(queue, sender, flags, data, size, sent_cb);
+        qemu_net_queue_append(queue, sender, flags, data, size, sent_cb);
+        return 0;
     }
 
     ret = qemu_net_queue_deliver(queue, sender, flags, data, size);
@@ -201,8 +198,8 @@ ssize_t qemu_net_queue_send_iov(NetQueue *queue,
     ssize_t ret;
 
     if (queue->delivering || !qemu_can_send_packet(sender)) {
-        return qemu_net_queue_append_iov(queue, sender, flags,
-                                         iov, iovcnt, sent_cb);
+        qemu_net_queue_append_iov(queue, sender, flags, iov, iovcnt, sent_cb);
+        return 0;
     }
 
     ret = qemu_net_queue_deliver_iov(queue, sender, flags, iov, iovcnt);
-- 
1.7.10.4