[Qemu-devel] [PATCH] eepro100: pad to ensure minimum packet size

[Bruce Rogers]

Recent gpxe e100pro drivers will drop small packets because the emulated
nic will report an error for small frames. In the qemu model we should
instead have the e100pro pad out the received frames to be the minimum
size and not report this case as an error.

Signed-off-by: Bruce Rogers <address@hidden>
---
 hw/eepro100.c |   23 +++++++++++++----------
 1 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/hw/eepro100.c b/hw/eepro100.c
index edf48f6..03b6934 100644
--- a/hw/eepro100.c
+++ b/hw/eepro100.c
@@ -1645,6 +1645,8 @@ static int nic_can_receive(VLANClientState *nc)
 #endif
 }
 
+#define MIN_BUF_SIZE      60 /* Min. octets in an ethernet frame sans FCS */
+
 static ssize_t nic_receive(VLANClientState *nc, const uint8_t * buf, size_t 
size)
 {
     /* TODO:
@@ -1653,6 +1655,7 @@ 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;
+    uint8_t min_buf[MIN_BUF_SIZE];
     static const uint8_t broadcast_macaddr[6] =
         { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
 
@@ -1660,15 +1663,15 @@ static ssize_t nic_receive(VLANClientState *nc, const 
uint8_t * buf, size_t size
         /* CSMA is disabled. */
         logout("%p received while CSMA is disabled\n", s);
         return -1;
-    } 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))) {
+    }
+    /* 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);
+    }
+    if ((size > MAX_ETH_FRAME_SIZE + 4) && !(s->configuration[18] & BIT(3))) {
         /* Long frame and configuration byte 18/3 (long receive ok) not set:
          * Long frames are discarded. */
         logout("%p received long frame (%zu byte), ignored\n", s, size);
@@ -1744,7 +1747,7 @@ 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 (size < 64) {
+    if (size < MIN_BUF_SIZE) {
         rfd_status |= 0x0080;
     }
     TRACE(OTHER, logout("command 0x%04x, link 0x%08x, addr 0x%08x, size %u\n",
-- 
1.6.0.2