[PATCH] igc: fix invalid length and corrupted multi-segment mbufs

[Martin Weiser <martin.weiser@allegro-packets.com>]

The issue only appeared with hardware-timestamping enabled
(RTE_ETH_RX_OFFLOAD_TIMESTAMP).

The length of the prepended hardware timestamp was not subtracted from
the data length so that received packets were 16 bytes longer than
expected.

In scatter-gather mode only the first mbuf has a timestamp but the
data offset of the follow-up mbufs was not adjusted accordingly.
This caused 16 bytes of packet data to be missing between
the segments.

Signed-off-by: Martin Weiser <martin.weiser@allegro-packets.com>
---
  drivers/net/igc/igc_txrx.c | 9 +++++++++
  1 file changed, 9 insertions(+)

diff --git a/drivers/net/igc/igc_txrx.c b/drivers/net/igc/igc_txrx.c
index d0cee1b016..2fafa91bd5 100644
--- a/drivers/net/igc/igc_txrx.c
+++ b/drivers/net/igc/igc_txrx.c
@@ -347,6 +347,8 @@ igc_recv_pkts(void *rx_queue, struct rte_mbuf 
**rx_pkts, uint16_t nb_pkts)

          rxm->data_off = RTE_PKTMBUF_HEADROOM;
          data_len = rte_le_to_cpu_16(rxd.wb.upper.length) - rxq->crc_len;
+        if (rxq->offloads & RTE_ETH_RX_OFFLOAD_TIMESTAMP)
+            data_len -= IGC_TS_HDR_LEN;
          rxm->data_len = data_len;
          rxm->pkt_len = data_len;
          rxm->nb_segs = 1;
@@ -509,6 +511,12 @@ igc_recv_scattered_pkts(void *rx_queue, struct 
rte_mbuf **rx_pkts,
           */
          rxm->data_off = RTE_PKTMBUF_HEADROOM;
          data_len = rte_le_to_cpu_16(rxd.wb.upper.length);
+        if (rxq->offloads & RTE_ETH_RX_OFFLOAD_TIMESTAMP) {
+            if (first_seg == NULL)
+                data_len -= IGC_TS_HDR_LEN;
+            else
+                rxm->data_off -= IGC_TS_HDR_LEN;
+        }
          rxm->data_len = data_len;

          /*
@@ -557,6 +565,7 @@ igc_recv_scattered_pkts(void *rx_queue, struct 
rte_mbuf **rx_pkts,
                  last_seg->data_len = last_seg->data_len -
                       (RTE_ETHER_CRC_LEN - data_len);
                  last_seg->next = NULL;
+                rxm = last_seg;
              } else {
                  rxm->data_len = (uint16_t)
                      (data_len - RTE_ETHER_CRC_LEN);
-- 
2.47.0