eepro100: Pad received short frames

QEMU sends frames smaller than 60 bytes to ethernet nics.
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 we can drop this in case QEMU's networking code is
ever changed.

Signed-off-by: Stefan Weil <weil@mail.berlios.de>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 25 insertions, 1 deletions

diff --git a/hw/eepro100.c b/hw/eepro100.c
index 848bf79461..ab5c699c9d 100644
--- a/hw/eepro100.c
+++ b/hw/eepro100.c
@@ -48,6 +48,15 @@
 #include "eeprom93xx.h"
 #include "sysemu.h"
 
+/* QEMU sends frames smaller than 60 bytes to ethernet nics.
+ * 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 padding for
+ * eepro100, too. We keep the define around in case it might
+ * become useful the future if the core networking is ever
+ * changed to pad short packets itself. */
+#define CONFIG_PAD_RECEIVED_FRAMES
+
 #define KiB 1024
 
 /* Debug EEPRO100 card. */
@@ -1640,19 +1649,32 @@ 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))) {
@@ -1731,9 +1753,11 @@ 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_phys(s->ru_base + s->ru_offset + offsetof(eepro100_rx_t, status),