doc: clarify L4 Tx checksum prerequisite

Based on PKT_TX_[TCP|UDP|SCTP]_CKSUM definition the user needs
to fill l2_len and l3_len mbuf fields before issuing HW Tx
checksum request.

Fixes: dad1ec72a377 ("doc: document NIC features")
Cc: stable@dpdk.org
Signed-off-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
Acked-by: Andrew Rybchenko <arybchenko@solarflare.com>

diff --git a/doc/guides/nics/features.rst b/doc/guides/nics/features.rst
index a211466..6c37e79 100644 (file)
--- a/doc/guides/nics/features.rst
+++ b/doc/guides/nics/features.rst
@@ -583,6 +583,7 @@ Supports L4 checksum offload.
 * **[uses]     mbuf**: ``mbuf.ol_flags:PKT_TX_IPV4`` | ``PKT_TX_IPV6``,
   ``mbuf.ol_flags:PKT_TX_L4_NO_CKSUM`` | ``PKT_TX_TCP_CKSUM`` |
   ``PKT_TX_SCTP_CKSUM`` | ``PKT_TX_UDP_CKSUM``.
+* **[uses]     mbuf**: ``mbuf.l2_len``, ``mbuf.l3_len``.
 * **[provides] mbuf**: ``mbuf.ol_flags:PKT_RX_L4_CKSUM_UNKNOWN`` |
   ``PKT_RX_L4_CKSUM_BAD`` | ``PKT_RX_L4_CKSUM_GOOD`` |
   ``PKT_RX_L4_CKSUM_NONE``.