datapath-windows: Account for VLAN tag in tunnel Decap

Decap functions for tunneling protocols do not compute
the packet header offsets correctly when there is a VLAN
tag in the L2 header. This results in incorrect checksum
computation causing the packet to be dropped.

This patch adds support to account for the VLAN tag in the
packet if its present, and makes use of the OvsExtractLayers()
function to correctly compute the header offsets for different
layers.

Testing done:
- Tested Geneve, STT, Vxlan and Gre and verified that there
  are no regressions.
- Verified that packets with VLAN tags are correctly handled
  in the decap code of all tunneling protocols. Previously,
  this would result in packet drops due to invalid checksums
  being computed.
- Verified that non-VLAN tagged packets are handled correctly.

Signed-off-by: Shashank Ram <rams@vmware.com>
Acked-by: Anand Kumar <kumaranand@vmware.com>
Signed-off-by: Alin Gabriel Serdean <aserdean@ovn.org>

1 files changed, 10 insertions, 4 deletions

diff --git a/datapath-windows/ovsext/Geneve.c b/datapath-windows/ovsext/Geneve.c
index 6dca69bc7..210716d5a 100644
--- a/datapath-windows/ovsext/Geneve.c
+++ b/datapath-windows/ovsext/Geneve.c
@@ -262,10 +262,16 @@ NDIS_STATUS OvsDecapGeneve(POVS_SWITCH_CONTEXT switchContext,
     PUINT8 bufferStart;
     PVOID optStart;
     NDIS_STATUS status;
+    OVS_PACKET_HDR_INFO layers = { 0 };
+
+    status = OvsExtractLayers(curNbl, &layers);
+    if (status != NDIS_STATUS_SUCCESS) {
+        return status;
+    }
 
     /* Check the length of the UDP payload */
     curNb = NET_BUFFER_LIST_FIRST_NB(curNbl);
-    tunnelSize = OvsGetGeneveTunHdrMinSize();
+    tunnelSize = OvsGetGeneveTunHdrSizeFromLayers(&layers);
     packetLength = NET_BUFFER_DATA_LENGTH(curNb);
     if (packetLength <= tunnelSize) {
         return NDIS_STATUS_INVALID_LENGTH;
@@ -295,13 +301,13 @@ NDIS_STATUS OvsDecapGeneve(POVS_SWITCH_CONTEXT switchContext,
 
     ethHdr = (EthHdr *)bufferStart;
     /* XXX: Handle IP options. */
-    ipHdr = (IPHdr *)((PCHAR)ethHdr + sizeof *ethHdr);
+    ipHdr = (IPHdr *)(bufferStart + layers.l3Offset);
     tunKey->src = ipHdr->saddr;
     tunKey->dst = ipHdr->daddr;
     tunKey->tos = ipHdr->tos;
     tunKey->ttl = ipHdr->ttl;
     tunKey->pad = 0;
-    udpHdr = (UDPHdr *)((PCHAR)ipHdr + sizeof *ipHdr);
+    udpHdr = (UDPHdr *)(bufferStart + layers.l4Offset);
 
     /* Validate if NIC has indicated checksum failure. */
     status = OvsValidateUDPChecksum(curNbl, udpHdr->check == 0);
@@ -312,7 +318,7 @@ NDIS_STATUS OvsDecapGeneve(POVS_SWITCH_CONTEXT switchContext,
     /* Calculate and verify UDP checksum if NIC didn't do it. */
     if (udpHdr->check != 0) {
         status = OvsCalculateUDPChecksum(curNbl, curNb, ipHdr, udpHdr,
-                                         packetLength);
+                                         packetLength, &layers);
         tunKey->flags |= OVS_TNL_F_CSUM;
         if (status != NDIS_STATUS_SUCCESS) {
             goto dropNbl;