[Xen-changelog] Fix bug that service os & vmx guest can't communicate with

[Xen patchbot -unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kaf24@xxxxxxxxxxxxxxxxxxxx
# Node ID 4b2c87242ad3a0963f1990acb6d8c15b1c017a5c
# Parent  5c49ed1145ccd3ec28f51a5f0f4cb33736852a63
Fix bug that service os & vmx guest can't communicate with
each other. The bug was physical packets smaller than
minimal packet size of 60 bytes were gettign thrown away.
Hence ARP traffic for example was dropped.

Signed-off-by: Edwin Zhai <edwin.zhai@xxxxxxxxx>
Signed-off-by: Xiaofeng Ling <xiaofeng.ling@xxxxxxxxx>

diff -r 5c49ed1145cc -r 4b2c87242ad3 tools/ioemu/hw/pcnet.c
--- a/tools/ioemu/hw/pcnet.c    Fri Sep  9 23:11:18 2005
+++ b/tools/ioemu/hw/pcnet.c    Sat Sep 10 14:17:02 2005
@@ -380,10 +380,13 @@
     return sizeof(s->buffer)-16;
 }
 
+#define MIN_BUF_SIZE 60
+
 static void pcnet_receive(void *opaque, const uint8_t *buf, int size)
 {
     PCNetState *s = opaque;
     int is_padr = 0, is_bcast = 0, is_ladr = 0;
+    uint8_t buf1[60];
 
     if (CSR_DRX(s) || CSR_STOP(s) || CSR_SPND(s) || !size)
         return;
@@ -391,6 +394,14 @@
 #ifdef PCNET_DEBUG
     printf("pcnet_receive size=%d\n", size);
 #endif
+
+    /* if too small buffer, then expand it */
+    if (size < MIN_BUF_SIZE) {
+        memcpy(buf1, buf, size);
+        memset(buf1 + size, 0, MIN_BUF_SIZE - size);
+        buf = buf1;
+        size = MIN_BUF_SIZE;
+    }
 
     if (CSR_PROM(s) 
         || (is_padr=padr_match(s, buf, size)) 

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