diff --git a/src/vnet/devices/virtio/node.c b/src/vnet/devices/virtio/node.c
index fc2317e..e9c72eb 100644
--- a/src/vnet/devices/virtio/node.c
+++ b/src/vnet/devices/virtio/node.c
@@ -145,6 +145,7 @@
 fill_gso_buffer_flags (vlib_buffer_t * b0, struct virtio_net_hdr_v1 *hdr)
 {
   u8 l4_proto = 0;
+  u8 l4_hdr_sz = 0;
   if (hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM)
 
     {
@@ -167,29 +168,50 @@
 	    }
 	}
 
+      vnet_buffer (b0)->l2_hdr_offset = 0;
+      vnet_buffer (b0)->l3_hdr_offset = l2hdr_sz;
       if (PREDICT_TRUE (ethertype == ETHERNET_TYPE_IP4))
 	{
 	  ip4_header_t *ip4 =
 	    (ip4_header_t *) (vlib_buffer_get_current (b0) + l2hdr_sz);
+	  vnet_buffer (b0)->l4_hdr_offset = l2hdr_sz + ip4_header_bytes (ip4);
 	  l4_proto = ip4->protocol;
 	  b0->flags |=
 	    (VNET_BUFFER_F_IS_IP4 | VNET_BUFFER_F_OFFLOAD_IP_CKSUM);
+	  b0->flags |=
+	    (VNET_BUFFER_F_L2_HDR_OFFSET_VALID
+	     | VNET_BUFFER_F_L3_HDR_OFFSET_VALID |
+	     VNET_BUFFER_F_L4_HDR_OFFSET_VALID);
 	}
       else if (PREDICT_TRUE (ethertype == ETHERNET_TYPE_IP6))
 	{
 	  ip6_header_t *ip6 =
 	    (ip6_header_t *) (vlib_buffer_get_current (b0) + l2hdr_sz);
+	  vnet_buffer (b0)->l4_hdr_offset = l2hdr_sz + sizeof (ip6_header_t);
 	  /* FIXME IPv6 EH traversal */
 	  l4_proto = ip6->protocol;
-	  b0->flags |= VNET_BUFFER_F_IS_IP6;
+	  b0->flags |= (VNET_BUFFER_F_IS_IP6 |
+			VNET_BUFFER_F_L2_HDR_OFFSET_VALID
+			| VNET_BUFFER_F_L3_HDR_OFFSET_VALID |
+			VNET_BUFFER_F_L4_HDR_OFFSET_VALID);
 	}
       if (l4_proto == IP_PROTOCOL_TCP)
 	{
 	  b0->flags |= VNET_BUFFER_F_OFFLOAD_TCP_CKSUM;
+	  tcp_header_t *tcp = (tcp_header_t *) (vlib_buffer_get_current (b0) +
+						vnet_buffer
+						(b0)->l4_hdr_offset);
+	  l4_hdr_sz = tcp_header_bytes (tcp);
+	  tcp->checksum = 0;
 	}
       else if (l4_proto == IP_PROTOCOL_UDP)
 	{
 	  b0->flags |= VNET_BUFFER_F_OFFLOAD_UDP_CKSUM;
+	  udp_header_t *udp = (udp_header_t *) (vlib_buffer_get_current (b0) +
+						vnet_buffer
+						(b0)->l4_hdr_offset);
+	  l4_hdr_sz = sizeof (*udp);
+	  udp->checksum = 0;
 	}
     }
 
@@ -197,12 +219,14 @@
     {
       ASSERT (hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM);
       vnet_buffer2 (b0)->gso_size = hdr->gso_size;
+      vnet_buffer2 (b0)->gso_l4_hdr_sz = l4_hdr_sz;
       b0->flags |= VNET_BUFFER_F_GSO | VNET_BUFFER_F_IS_IP4;
     }
   if (hdr->gso_type == VIRTIO_NET_HDR_GSO_TCPV6)
     {
       ASSERT (hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM);
       vnet_buffer2 (b0)->gso_size = hdr->gso_size;
+      vnet_buffer2 (b0)->gso_l4_hdr_sz = l4_hdr_sz;
       b0->flags |= VNET_BUFFER_F_GSO | VNET_BUFFER_F_IS_IP6;
     }
 }
diff --git a/src/vnet/pg/input.c b/src/vnet/pg/input.c
index f4f6bd4..bbcd34e 100644
--- a/src/vnet/pg/input.c
+++ b/src/vnet/pg/input.c
@@ -1535,6 +1535,7 @@
     {
       vlib_buffer_t *b0 = vlib_get_buffer (vm, buffers[i]);
       u8 l4_proto = 0;
+      u8 l4_hdr_sz = 0;
 
       ethernet_header_t *eh =
 	(ethernet_header_t *) vlib_buffer_get_current (b0);
@@ -1555,30 +1556,52 @@
 	    }
 	}
 
+      vnet_buffer (b0)->l2_hdr_offset = 0;
+      vnet_buffer (b0)->l3_hdr_offset = l2hdr_sz;
+
       if (PREDICT_TRUE (ethertype == ETHERNET_TYPE_IP4))
 	{
 	  ip4_header_t *ip4 =
 	    (ip4_header_t *) (vlib_buffer_get_current (b0) + l2hdr_sz);
+	  vnet_buffer (b0)->l4_hdr_offset = l2hdr_sz + ip4_header_bytes (ip4);
 	  l4_proto = ip4->protocol;
 	  b0->flags |=
 	    (VNET_BUFFER_F_IS_IP4 | VNET_BUFFER_F_OFFLOAD_IP_CKSUM);
+	  b0->flags |= (VNET_BUFFER_F_L2_HDR_OFFSET_VALID
+			| VNET_BUFFER_F_L3_HDR_OFFSET_VALID |
+			VNET_BUFFER_F_L4_HDR_OFFSET_VALID);
 	}
       else if (PREDICT_TRUE (ethertype == ETHERNET_TYPE_IP6))
 	{
 	  ip6_header_t *ip6 =
 	    (ip6_header_t *) (vlib_buffer_get_current (b0) + l2hdr_sz);
+	  vnet_buffer (b0)->l4_hdr_offset = l2hdr_sz + sizeof (ip6_header_t);
 	  /* FIXME IPv6 EH traversal */
 	  l4_proto = ip6->protocol;
-	  b0->flags |= VNET_BUFFER_F_IS_IP6;
+	  b0->flags |=
+	    (VNET_BUFFER_F_IS_IP6 | VNET_BUFFER_F_L2_HDR_OFFSET_VALID |
+	     VNET_BUFFER_F_L3_HDR_OFFSET_VALID |
+	     VNET_BUFFER_F_L4_HDR_OFFSET_VALID);
 	}
       if (l4_proto == IP_PROTOCOL_TCP)
 	{
 	  b0->flags |= (VNET_BUFFER_F_OFFLOAD_TCP_CKSUM | VNET_BUFFER_F_GSO);
+	  tcp_header_t *tcp = (tcp_header_t *) (vlib_buffer_get_current (b0) +
+						vnet_buffer
+						(b0)->l4_hdr_offset);
+	  l4_hdr_sz = tcp_header_bytes (tcp);
+	  tcp->checksum = 0;
+	  vnet_buffer2 (b0)->gso_l4_hdr_sz = l4_hdr_sz;
 	  vnet_buffer2 (b0)->gso_size = packet_data_size;
 	}
       else if (l4_proto == IP_PROTOCOL_UDP)
 	{
 	  b0->flags |= VNET_BUFFER_F_OFFLOAD_UDP_CKSUM;
+	  udp_header_t *udp = (udp_header_t *) (vlib_buffer_get_current (b0) +
+						vnet_buffer
+						(b0)->l4_hdr_offset);
+	  vnet_buffer2 (b0)->gso_l4_hdr_sz = sizeof (*udp);
+	  udp->checksum = 0;
 	}
     }
 }