+ struct virtio_net_hdr_v1 *hdr = vlib_buffer_get_current (b) - hdr_sz;
+
+ clib_memset (hdr, 0, hdr_sz);
+
+ if (do_gso && (b->flags & VNET_BUFFER_F_GSO))
+ {
+ if (b->flags & VNET_BUFFER_F_IS_IP4)
+ {
+ ip4_header_t *ip4;
+ gso_header_offset_t gho = vnet_gso_header_offset_parser (b, 0);
+ hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
+ hdr->gso_size = vnet_buffer2 (b)->gso_size;
+ hdr->hdr_len = gho.l4_hdr_offset + gho.l4_hdr_sz;
+ hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
+ hdr->csum_start = gho.l4_hdr_offset; // 0x22;
+ hdr->csum_offset = STRUCT_OFFSET_OF (tcp_header_t, checksum);
+ ip4 =
+ (ip4_header_t *) (vlib_buffer_get_current (b) +
+ gho.l3_hdr_offset);
+ /*
+ * virtio devices do not support IP4 checksum offload. So driver takes care
+ * of it while doing tx.
+ */
+ if (b->flags & VNET_BUFFER_F_OFFLOAD_IP_CKSUM)
+ ip4->checksum = ip4_header_checksum (ip4);
+ }
+ else if (b->flags & VNET_BUFFER_F_IS_IP6)
+ {
+ gso_header_offset_t gho = vnet_gso_header_offset_parser (b, 1);
+ hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
+ hdr->gso_size = vnet_buffer2 (b)->gso_size;
+ hdr->hdr_len = gho.l4_hdr_offset + gho.l4_hdr_sz;
+ hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
+ hdr->csum_start = gho.l4_hdr_offset; // 0x36;
+ hdr->csum_offset = STRUCT_OFFSET_OF (tcp_header_t, checksum);
+ }
+ }
+ else if (csum_offload
+ && (b->flags & (VNET_BUFFER_F_OFFLOAD_TCP_CKSUM |
+ VNET_BUFFER_F_OFFLOAD_UDP_CKSUM)))
+ {
+ set_checksum_offsets (vm, vif, b, hdr);
+ }