[Qemu-devel] [PATCH 8/9] eepro100: Pad received short frames

[Stefan Weil <weil@mail.berlios.de>]

QEMU sends frames smaller than 60 bytes to ethernet nics.
This should be fixed in the networking code because normally
such frames are rejected by real NICs and their emulations.
To avoid this behaviour, other NIC emulations pad received
frames. This patch enables this workaround for eepro100, too.

All related code is marked with CONFIG_PAD_RECEIVED_FRAMES,
so emulation of the correct handling for short frames can
be restored as soon as QEMU's networking code is fixed.

Signed-off-by: Stefan Weil <weil@mail.berlios.de>
---
 hw/eepro100.c |   25 ++++++++++++++++++++++++-
 1 files changed, 24 insertions(+), 1 deletions(-)

diff --git a/hw/eepro100.c b/hw/eepro100.c
index 500a3af..a740d2e 100644
--- a/hw/eepro100.c
+++ b/hw/eepro100.c
@@ -47,6 +47,14 @@
 #include "eeprom93xx.h"
 #include "sysemu.h"
 
+/* QEMU sends frames smaller than 60 bytes to ethernet nics.
+ * This should be fixed in the networking code because normally
+ * such frames are rejected by real nics and their emulations.
+ * To avoid this behaviour, other nic emulations pad received
+ * frames. The following definition enables this workaround for
+ * eepro100, too. */
+#define CONFIG_PAD_RECEIVED_FRAMES
+
 #define KiB 1024
 
 /* Debug EEPRO100 card. */
@@ -1756,19 +1764,32 @@ static ssize_t nic_receive(VLANClientState *nc, const uint8_t * buf, size_t size
      */
     EEPRO100State *s = DO_UPCAST(NICState, nc, nc)->opaque;
     uint16_t rfd_status = 0xa000;
+#if defined(CONFIG_PAD_RECEIVED_FRAMES)
+    uint8_t min_buf[60];
+#endif
     static const uint8_t broadcast_macaddr[6] =
         { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
 
+#if defined(CONFIG_PAD_RECEIVED_FRAMES)
+    /* Pad to minimum Ethernet frame length */
+    if (size < sizeof(min_buf)) {
+        memcpy(min_buf, buf, size);
+        memset(&min_buf[size], 0, sizeof(min_buf) - size);
+        buf = min_buf;
+        size = sizeof(min_buf);
+    }
+#endif
+
     if (s->configuration[8] & 0x80) {
         /* CSMA is disabled. */
         logout("%p received while CSMA is disabled\n", s);
         return -1;
+#if !defined(CONFIG_PAD_RECEIVED_FRAMES)
     } else if (size < 64 && (s->configuration[7] & BIT(0))) {
         /* Short frame and configuration byte 7/0 (discard short receive) set:
          * Short frame is discarded */
         logout("%p received short frame (%zu byte)\n", s, size);
         s->statistics.rx_short_frame_errors++;
-#if 0
         return -1;
 #endif
     } else if ((size > MAX_ETH_FRAME_SIZE + 4) && !(s->configuration[18] & BIT(3))) {
@@ -1847,9 +1868,11 @@ static ssize_t nic_receive(VLANClientState *nc, const uint8_t * buf, size_t size
             "(%zu bytes); data truncated\n", rfd_size, size);
         size = rfd_size;
     }
+#if !defined(CONFIG_PAD_RECEIVED_FRAMES)
     if (size < 64) {
         rfd_status |= 0x0080;
     }
+#endif
     TRACE(OTHER, logout("command 0x%04x, link 0x%08x, addr 0x%08x, size %u\n",
           rfd_command, rx.link, rx.rx_buf_addr, rfd_size));
     stw_le_phys(s->ru_base + s->ru_offset + offsetof(eepro100_rx_t, status),
-- 
1.7.2.5