pcnet: Do not receive external frames in loopback mode

While not explicitly stated in the spec, it was observed on real systems
that enabling loopback testing on the pcnet controller disables
reception of external frames. And some legacy software relies on it, so
provide this behavior.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

diff --git a/hw/pcnet.c b/hw/pcnet.c
index b52935a..f970bda 100644 (file)
--- a/hw/pcnet.c
+++ b/hw/pcnet.c
@@ -1048,9 +1048,10 @@ ssize_t pcnet_receive(VLANClientState *nc, const uint8_t *buf, size_t size_)
     int crc_err = 0;
     int size = size_;
 
-    if (CSR_DRX(s) || CSR_STOP(s) || CSR_SPND(s) || !size)
+    if (CSR_DRX(s) || CSR_STOP(s) || CSR_SPND(s) || !size ||
+        (CSR_LOOP(s) && !s->looptest)) {
         return -1;
-
+    }
 #ifdef PCNET_DEBUG
     printf("pcnet_receive size=%d\n", size);
 #endif