+/* When doing TSO, the IP length is not included in the pseudo header
+ * checksum of the packet given to the PMD, but for virtio it is
+ * expected.
+ */
+static void
+virtio_tso_fix_cksum(struct rte_mbuf *m)
+{
+ /* common case: header is not fragmented */
+ if (likely(rte_pktmbuf_data_len(m) >= m->l2_len + m->l3_len +
+ m->l4_len)) {
+ struct ipv4_hdr *iph;
+ struct ipv6_hdr *ip6h;
+ struct tcp_hdr *th;
+ uint16_t prev_cksum, new_cksum, ip_len, ip_paylen;
+ uint32_t tmp;
+
+ iph = rte_pktmbuf_mtod_offset(m, struct ipv4_hdr *, m->l2_len);
+ th = RTE_PTR_ADD(iph, m->l3_len);
+ if ((iph->version_ihl >> 4) == 4) {
+ iph->hdr_checksum = 0;
+ iph->hdr_checksum = rte_ipv4_cksum(iph);
+ ip_len = iph->total_length;
+ ip_paylen = rte_cpu_to_be_16(rte_be_to_cpu_16(ip_len) -
+ m->l3_len);
+ } else {
+ ip6h = (struct ipv6_hdr *)iph;
+ ip_paylen = ip6h->payload_len;
+ }
+
+ /* calculate the new phdr checksum not including ip_paylen */
+ prev_cksum = th->cksum;
+ tmp = prev_cksum;
+ tmp += ip_paylen;
+ tmp = (tmp & 0xffff) + (tmp >> 16);
+ new_cksum = tmp;
+
+ /* replace it in the packet */
+ th->cksum = new_cksum;
+ }
+}
+