net/memif: fix chained mbuf determination
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Commit Message
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.
Signed-off-by: Junxiao Shi <git@mail1.yoursunny.com>
---
drivers/net/memif/rte_eth_memif.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
Comments
On 9/9/2021 3:42 PM, Junxiao Shi wrote:
> 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.
>
> Signed-off-by: Junxiao Shi <git@mail1.yoursunny.com>
+ memif maintainer, Jakub.
Jakub, can you please review the patch?
> > 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.
> >
> > Signed-off-by: Junxiao Shi <git@mail1.yoursunny.com>
Looks ok to me. Thanks for the patch!
Reviewed-by: Jakub Grajciar <jgrajcia@cisco.com>
On 9/22/2021 7:19 AM, Jakub Grajciar -X (jgrajcia - PANTHEON TECH SRO at Cisco)
wrote:
>>> 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.
>>>
>>> Signed-off-by: Junxiao Shi <git@mail1.yoursunny.com>
>
> Looks ok to me. Thanks for the patch!
>
> Reviewed-by: Jakub Grajciar <jgrajcia@cisco.com>
>
Fixes: 09c7e63a71f9 ("net/memif: introduce memory interface PMD")
Fixes: 43b815d88188 ("net/memif: support zero-copy slave")
Cc: stable@dpdk.org
Applied to dpdk-next-net/main, thanks.
@@ -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 @@ eth_memif_tx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
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 @@ memif_tx_one_zc(struct pmd_process_private *proc_private, struct memif_queue *mq
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 */