[Qemu-devel] [PATCH] pcnet: Do not receive external frames in loopback mode

[Jan Kiszka]

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 <address@hidden>
---
 hw/pcnet.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/hw/pcnet.c b/hw/pcnet.c
index 5e63eb5..5c94dd2 100644
--- 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
-- 
1.7.1