On 5/2/2024 10:31 PM, Stephen Hemminger wrote:
> If tap device in kernel returns EAGAIN that means it is full.
> That is not an error.
>
> Signed-off-by: Stephen Hemminger <step...@networkplumber.org>
> ---
> drivers/net/tap/rte_eth_tap.c | 13 ++++++++-----
> 1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/net/tap/rte_eth_tap.c b/drivers/net/tap/rte_eth_tap.c
> index 2484a82ccb..485bd35912 100644
> --- a/drivers/net/tap/rte_eth_tap.c
> +++ b/drivers/net/tap/rte_eth_tap.c
> @@ -542,7 +542,6 @@ tap_write_mbufs(struct tx_queue *txq, uint16_t num_mbufs,
> struct rte_mbuf *seg = mbuf;
> uint64_t l4_ol_flags;
> int proto;
> - int n;
> int j;
> int k; /* current index in iovecs for copying segments */
>
> @@ -647,14 +646,18 @@ tap_write_mbufs(struct tx_queue *txq, uint16_t
> num_mbufs,
> }
>
> /* copy the tx frame data */
> - n = writev(process_private->fds[txq->queue_id], iovecs, k);
> - if (n <= 0)
> - return -1;
> + if (unlikely(writev(process_private->fds[txq->queue_id],
> iovecs, k) < 0)) {
> + TAP_LOG(DEBUG, "writev (qid=%u fd=%d) %s",
> + txq->queue_id,
> process_private->fds[txq->queue_id],
> + strerror(errno));
>
Do we really want logging in datapath?
> + return (errno == EAGAIN) ? 0 : -1;
>
Nack.
Returning '0' will cause 'pmd_tx_burst()' to continue and increase
'num_tx', this will mislead as packet sent successfully.
We should have three return values from 'tap_write_mbufs()':
<0 -> Error, 'pmd_tx_burst()' should break, stats.errors updated.
0 -> 'pmd_tx_burst()' should break, valid num_tx returned
>0 -> 'pmd_tx_burst()' work as it is.
> + }
>
> (*num_packets)++;
> (*num_tx_bytes) += rte_pktmbuf_pkt_len(mbuf);
> }
> - return 0;
> +
> + return 1;
>
Why '1', wouldn't it be better to return number of packets written
successfully.
