Re: [Qemu-trivial] [PATCH] vmxnet3: Pad short frames to minimum size (60 bytes)

[Ben Draper]

Interestingly this does not appear to affect Windows guests on the same host/bridge as the ESXi guest, as

Windows pads the frames before sending them out. However it does affect Linux guests on the same host/bridge

from communicating with the ESXi guest itself and the guests ESXi hosts.

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On 20 August 2014 13:27, Ben Draper <address@hidden> wrote:

When running VMware ESXi under qemu-kvm the guest discards frames
that are too short. Short ARP Requests will be dropped, this prevents
guests on the same bridge as VMware ESXi from communicating. This patch
simply adds the padding on the network device itself.

Signed-off-by: Ben Draper <address@hidden>
---
 hw/net/vmxnet3.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/hw/net/vmxnet3.c b/hw/net/vmxnet3.c
index 791321f..f246fa1 100644
--- a/hw/net/vmxnet3.c
+++ b/hw/net/vmxnet3.c
@@ -34,6 +34,7 @@

 #define PCI_DEVICE_ID_VMWARE_VMXNET3_REVISION 0x1
 #define VMXNET3_MSIX_BAR_SIZE 0x2000
+#define MIN_BUF_SIZE 60

 #define VMXNET3_BAR0_IDX      (0)
 #define VMXNET3_BAR1_IDX      (1)
@@ -1871,12 +1872,21 @@ vmxnet3_receive(NetClientState *nc, const uint8_t *buf, size_t size)
 {
     VMXNET3State *s = qemu_get_nic_opaque(nc);
     size_t bytes_indicated;
+    uint8_t min_buf[MIN_BUF_SIZE];

     if (!vmxnet3_can_receive(nc)) {
         VMW_PKPRN("Cannot receive now");
         return -1;
     }

+    /* 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 (s->peer_has_vhdr) {
         vmxnet_rx_pkt_set_vhdr(s->rx_pkt, (struct virtio_net_hdr *)buf);
         buf += sizeof(struct virtio_net_hdr);
--
1.7.10.4