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Date:      Fri, 13 Apr 2012 14:51:49 -0400
From:      Landon J Fuller <landonf@plausible.coop>
To:        freebsd-emulation@freebsd.org
Subject:   [PATCH] VLAN trunking support in VirtualBox vboxnetflt
Message-ID:  <6BCC0BDE-C9FD-47F0-96AE-88F797EFB074@plausible.coop>
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Howdy,

I was looking into trunking VLANs into a virtual machine via bridging, =
and noted that transmit of 802.1q tagged packets worked from the guest =
VM, but upon reception, the VLAN tag seemed to be stripped before the =
packets hit the guest's interface.

Taking a look at the netgraph-based bridging implementation, it looks =
like the VLAN tag is not being re-inserted at the head of the ethernet =
frame prior to handing off the to VirtualBox, and VBox doesn't seem to =
have an equivalent 'ether_vtag' field in its INTNETSG struct to handle =
this.

Thus, to preserve the VLAN tag, I modified vboxNetFltFreeBSDMBufToSG() =
to ether_vlanencap() to insert the VLAN tag before handing off to VBox. =
With this in place, I was able to successfully trunk VLANs to a virtual =
machine.=20

Some caveats:
	- If using virtio-kmod's if_vtnet, you must set vlanhwfilter (or =
promisc) flags on the guest interface before virtualbox will pass the =
VLAN tagged packets through. Otherwise, the VBox virtio-net device =
implementation will filter out the incoming packets before handing them =
to the VM hardware.
	- VBox's em(4) host implementation does not appear to support =
'hardware' VLAN tagging, but it does declare it. If using a em(4) =
virtualized NIC, you must set -vlanhwtag on the guest interface.

I welcome someone(s) with more experience than I eyeballing the (tiny) =
attached patch. I'm also especially concerned as to whether this should =
be considered supported functionality in VBox, or I'm just getting lucky =
with the virtio-net code path.

Thanks,
Landon


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	filename*0=patch-src-VBox-HostDrivers-VBoxNetFlt-freebsd-VBoxNetFlt-freebsd;
	filename*1=.c
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	name="patch-src-VBox-HostDrivers-VBoxNetFlt-freebsd-VBoxNetFlt-freebsd.c"
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--- src/VBox/./HostDrivers/VBoxNetFlt/freebsd/VBoxNetFlt-freebsd.c.orig	2012-04-12 17:27:56.035382846 -0400
+++ src/VBox/./HostDrivers/VBoxNetFlt/freebsd/VBoxNetFlt-freebsd.c	2012-04-12 17:30:13.038601065 -0400
@@ -439,6 +439,16 @@
         if (m == NULL)
             break;
 
+        /* Preprend a VLAN header for consumption by the virtual switch */
+        if (m->m_flags & M_VLANTAG) {
+            m = ether_vlanencap(m, m->m_pkthdr.ether_vtag);
+            if (m == NULL) {
+                printf("vboxflt: unable to prepend VLAN header\n");
+                break;
+            }
+            m->m_flags &= ~M_VLANTAG;
+        }
+
         for (m0 = m; m0 != NULL; m0 = m0->m_next)
             if (m0->m_len > 0)
                 cSegs++;

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