+static uint64_t
+tap_tx_offload_get_port_capa(void)
+{
+ /*
+ * No specific port Tx offload capabilities.
+ */
+ return 0;
+}
+
+static uint64_t
+tap_tx_offload_get_queue_capa(void)
+{
+ return DEV_TX_OFFLOAD_MULTI_SEGS |
+ DEV_TX_OFFLOAD_IPV4_CKSUM |
+ DEV_TX_OFFLOAD_UDP_CKSUM |
+ DEV_TX_OFFLOAD_TCP_CKSUM |
+ DEV_TX_OFFLOAD_TCP_TSO;
+}
+
+/* Finalize l4 checksum calculation */
+static void
+tap_tx_l4_cksum(uint16_t *l4_cksum, uint16_t l4_phdr_cksum,
+ uint32_t l4_raw_cksum)
+{
+ if (l4_cksum) {
+ uint32_t cksum;
+
+ cksum = __rte_raw_cksum_reduce(l4_raw_cksum);
+ cksum += l4_phdr_cksum;
+
+ cksum = ((cksum & 0xffff0000) >> 16) + (cksum & 0xffff);
+ cksum = (~cksum) & 0xffff;
+ if (cksum == 0)
+ cksum = 0xffff;
+ *l4_cksum = cksum;
+ }
+}
+
+/* Accumaulate L4 raw checksums */
+static void
+tap_tx_l4_add_rcksum(char *l4_data, unsigned int l4_len, uint16_t *l4_cksum,
+ uint32_t *l4_raw_cksum)
+{
+ if (l4_cksum == NULL)
+ return;
+
+ *l4_raw_cksum = __rte_raw_cksum(l4_data, l4_len, *l4_raw_cksum);
+}
+
+/* L3 and L4 pseudo headers checksum offloads */
+static void
+tap_tx_l3_cksum(char *packet, uint64_t ol_flags, unsigned int l2_len,
+ unsigned int l3_len, unsigned int l4_len, uint16_t **l4_cksum,
+ uint16_t *l4_phdr_cksum, uint32_t *l4_raw_cksum)
+{
+ void *l3_hdr = packet + l2_len;
+
+ if (ol_flags & (PKT_TX_IP_CKSUM | PKT_TX_IPV4)) {
+ struct rte_ipv4_hdr *iph = l3_hdr;
+ uint16_t cksum;
+
+ iph->hdr_checksum = 0;
+ cksum = rte_raw_cksum(iph, l3_len);
+ iph->hdr_checksum = (cksum == 0xffff) ? cksum : ~cksum;
+ }
+ if (ol_flags & PKT_TX_L4_MASK) {
+ void *l4_hdr;
+
+ l4_hdr = packet + l2_len + l3_len;
+ if ((ol_flags & PKT_TX_L4_MASK) == PKT_TX_UDP_CKSUM)
+ *l4_cksum = &((struct rte_udp_hdr *)l4_hdr)->dgram_cksum;
+ else if ((ol_flags & PKT_TX_L4_MASK) == PKT_TX_TCP_CKSUM)
+ *l4_cksum = &((struct rte_tcp_hdr *)l4_hdr)->cksum;
+ else
+ return;
+ **l4_cksum = 0;
+ if (ol_flags & PKT_TX_IPV4)
+ *l4_phdr_cksum = rte_ipv4_phdr_cksum(l3_hdr, 0);
+ else
+ *l4_phdr_cksum = rte_ipv6_phdr_cksum(l3_hdr, 0);
+ *l4_raw_cksum = __rte_raw_cksum(l4_hdr, l4_len, 0);
+ }
+}
+
+static inline void
+tap_write_mbufs(struct tx_queue *txq, uint16_t num_mbufs,
+ struct rte_mbuf **pmbufs,
+ uint16_t *num_packets, unsigned long *num_tx_bytes)
+{
+ int i;
+ uint16_t l234_hlen;
+ struct pmd_process_private *process_private;
+
+ process_private = rte_eth_devices[txq->out_port].process_private;
+
+ for (i = 0; i < num_mbufs; i++) {
+ struct rte_mbuf *mbuf = pmbufs[i];
+ struct iovec iovecs[mbuf->nb_segs + 2];
+ struct tun_pi pi = { .flags = 0, .proto = 0x00 };
+ struct rte_mbuf *seg = mbuf;
+ char m_copy[mbuf->data_len];
+ int proto;
+ int n;
+ int j;
+ int k; /* current index in iovecs for copying segments */
+ uint16_t seg_len; /* length of first segment */
+ uint16_t nb_segs;
+ uint16_t *l4_cksum; /* l4 checksum (pseudo header + payload) */
+ uint32_t l4_raw_cksum = 0; /* TCP/UDP payload raw checksum */
+ uint16_t l4_phdr_cksum = 0; /* TCP/UDP pseudo header checksum */
+ uint16_t is_cksum = 0; /* in case cksum should be offloaded */
+
+ l4_cksum = NULL;
+ if (txq->type == ETH_TUNTAP_TYPE_TUN) {
+ /*
+ * TUN and TAP are created with IFF_NO_PI disabled.
+ * For TUN PMD this mandatory as fields are used by
+ * Kernel tun.c to determine whether its IP or non IP
+ * packets.
+ *
+ * The logic fetches the first byte of data from mbuf
+ * then compares whether its v4 or v6. If first byte
+ * is 4 or 6, then protocol field is updated.
+ */
+ char *buff_data = rte_pktmbuf_mtod(seg, void *);
+ proto = (*buff_data & 0xf0);
+ pi.proto = (proto == 0x40) ?
+ rte_cpu_to_be_16(RTE_ETHER_TYPE_IPV4) :
+ ((proto == 0x60) ?
+ rte_cpu_to_be_16(RTE_ETHER_TYPE_IPV6) :
+ 0x00);
+ }
+
+ k = 0;
+ iovecs[k].iov_base = π
+ iovecs[k].iov_len = sizeof(pi);
+ k++;
+
+ nb_segs = mbuf->nb_segs;
+ if (txq->csum &&
+ ((mbuf->ol_flags & (PKT_TX_IP_CKSUM | PKT_TX_IPV4) ||
+ (mbuf->ol_flags & PKT_TX_L4_MASK) == PKT_TX_UDP_CKSUM ||
+ (mbuf->ol_flags & PKT_TX_L4_MASK) == PKT_TX_TCP_CKSUM))) {
+ is_cksum = 1;
+
+ /* Support only packets with at least layer 4
+ * header included in the first segment
+ */
+ seg_len = rte_pktmbuf_data_len(mbuf);
+ l234_hlen = mbuf->l2_len + mbuf->l3_len + mbuf->l4_len;
+ if (seg_len < l234_hlen)
+ break;
+
+ /* To change checksums, work on a * copy of l2, l3
+ * headers + l4 pseudo header
+ */
+ rte_memcpy(m_copy, rte_pktmbuf_mtod(mbuf, void *),
+ l234_hlen);
+ tap_tx_l3_cksum(m_copy, mbuf->ol_flags,
+ mbuf->l2_len, mbuf->l3_len, mbuf->l4_len,
+ &l4_cksum, &l4_phdr_cksum,
+ &l4_raw_cksum);
+ iovecs[k].iov_base = m_copy;
+ iovecs[k].iov_len = l234_hlen;
+ k++;
+
+ /* Update next iovecs[] beyond l2, l3, l4 headers */
+ if (seg_len > l234_hlen) {
+ iovecs[k].iov_len = seg_len - l234_hlen;
+ iovecs[k].iov_base =
+ rte_pktmbuf_mtod(seg, char *) +
+ l234_hlen;
+ tap_tx_l4_add_rcksum(iovecs[k].iov_base,
+ iovecs[k].iov_len, l4_cksum,
+ &l4_raw_cksum);
+ k++;
+ nb_segs++;
+ }
+ seg = seg->next;
+ }
+
+ for (j = k; j <= nb_segs; j++) {
+ iovecs[j].iov_len = rte_pktmbuf_data_len(seg);
+ iovecs[j].iov_base = rte_pktmbuf_mtod(seg, void *);
+ if (is_cksum)
+ tap_tx_l4_add_rcksum(iovecs[j].iov_base,
+ iovecs[j].iov_len, l4_cksum,
+ &l4_raw_cksum);
+ seg = seg->next;
+ }
+
+ if (is_cksum)
+ tap_tx_l4_cksum(l4_cksum, l4_phdr_cksum, l4_raw_cksum);
+
+ /* copy the tx frame data */
+ n = writev(process_private->txq_fds[txq->queue_id], iovecs, j);
+ if (n <= 0)
+ break;
+ (*num_packets)++;
+ (*num_tx_bytes) += rte_pktmbuf_pkt_len(mbuf);
+ }
+}
+