net/memif: fix chained mbuf determination

Previously, TX functions call rte_pktmbuf_is_contiguous to determine
whether an mbuf is chained. However, rte_pktmbuf_is_contiguous is
designed to work on the first mbuf of a packet only. In case a packet
contains three or more segment mbufs in a chain, it may cause truncated
packets or rte_mbuf_sanity_check panics.

This patch updates TX functions to determine chained mbufs using
mbuf_head->nb_segs field, which works in all cases. Moreover, it
maintains that the second cacheline is only accessed when chained mbuf
is actually present.

Fixes: 09c7e63a71f9 ("net/memif: introduce memory interface PMD")
Fixes: 43b815d88188 ("net/memif: support zero-copy slave")
Cc: stable@dpdk.org
Signed-off-by: Junxiao Shi <git@mail1.yoursunny.com>
Reviewed-by: Jakub Grajciar <jgrajcia@cisco.com>

diff --git a/drivers/net/memif/rte_eth_memif.c b/drivers/net/memif/rte_eth_memif.c
index de6becd..fd9e877 100644 (file)
--- a/drivers/net/memif/rte_eth_memif.c
+++ b/drivers/net/memif/rte_eth_memif.c
@@ -199,6 +199,7 @@ memif_dev_info(struct rte_eth_dev *dev __rte_unused, struct rte_eth_dev_info *de
        dev_info->max_rx_queues = ETH_MEMIF_MAX_NUM_Q_PAIRS;
        dev_info->max_tx_queues = ETH_MEMIF_MAX_NUM_Q_PAIRS;
        dev_info->min_rx_bufsize = 0;
+       dev_info->tx_offload_capa = DEV_TX_OFFLOAD_MULTI_SEGS;
 
        return 0;
 }
@@ -567,7 +568,7 @@ eth_memif_tx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
                rte_eth_devices[mq->in_port].process_private;
        memif_ring_t *ring = memif_get_ring_from_queue(proc_private, mq);
        uint16_t slot, saved_slot, n_free, ring_size, mask, n_tx_pkts = 0;
-       uint16_t src_len, src_off, dst_len, dst_off, cp_len;
+       uint16_t src_len, src_off, dst_len, dst_off, cp_len, nb_segs;
        memif_ring_type_t type = mq->type;
        memif_desc_t *d0;
        struct rte_mbuf *mbuf;
@@ -615,6 +616,7 @@ eth_memif_tx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
 
        while (n_tx_pkts < nb_pkts && n_free) {
                mbuf_head = *bufs++;
+               nb_segs = mbuf_head->nb_segs;
                mbuf = mbuf_head;
 
                saved_slot = slot;
@@ -659,7 +661,7 @@ next_in_chain:
                        d0->length = dst_off;
                }
 
-               if (rte_pktmbuf_is_contiguous(mbuf) == 0) {
+               if (--nb_segs > 0) {
                        mbuf = mbuf->next;
                        goto next_in_chain;
                }
@@ -696,6 +698,7 @@ memif_tx_one_zc(struct pmd_process_private *proc_private, struct memif_queue *mq
                uint16_t slot, uint16_t n_free)
 {
        memif_desc_t *d0;
+       uint16_t nb_segs = mbuf->nb_segs;
        int used_slots = 1;
 
 next_in_chain:
@@ -716,7 +719,7 @@ next_in_chain:
        d0->flags = 0;
 
        /* check if buffer is chained */
-       if (rte_pktmbuf_is_contiguous(mbuf) == 0) {
+       if (--nb_segs > 0) {
                if (n_free < 2)
                        return 0;
                /* mark buffer as chained */