> From: Stephen Hemminger [mailto:[email protected]] > Sent: Wednesday, 18 February 2026 18.13 > > On Wed, 18 Feb 2026 09:48:04 +0100 > Morten Brørup <[email protected]> wrote: > > > > + * > > > + * A return value equal to *nb_pkts* means that all packets have > been > > > + * consumed, and this is likely to signify that other output > packets > > > * could be immediately transmitted again. Applications that > implement > > > a > > > * "send as many packets to transmit as possible" policy can check > > > this > > > * specific case and keep invoking the rte_eth_tx_burst() function > > > until > > > * a value less than *nb_pkts* is returned. > > > * > > > + * If a packet cannot be transmitted due to an error (for example, > an > > > + * invalid offload flag), the driver must still consume it and > free > > > the > > > + * mbuf, rather than stopping at that point. Such packets should > be > > > + * counted in the *tx_errors* port statistic. > > > > The above paragraph is driver centric, it should be application > centric. > > Most of the applications are doing it right already since everybody > starts with l2fwd, or l3fwd. The problem I see is buggy drivers.
I agree. But this API is for applications, so its documentation should be written for application developers. Drivers are doing it wrong because driver APIs are largely undocumented, e.g. [2] and [3]. [2]: https://elixir.bootlin.com/dpdk/v25.11/source/lib/ethdev/rte_ethdev_core.h#L33 [3]: https://elixir.bootlin.com/dpdk/v25.11/source/lib/mempool/rte_mempool.h#L478 It would be an improvement if driver API documentation at least referred to the application APIs that wrap them. > > > Suggest rephrasing as: > > > > If a packet cannot be transmitted due to an error (for example, an > invalid offload flag), the rte_eth_tx_burst() function will still > consume it, rather than stopping at that point. > > Such packets are counted in the *oerrors* port statistic. > > > > NB: In struct rte_eth_stats [1], the error counter is named > "oerrors", not "tx_errors". > > > > [1]: > https://elixir.bootlin.com/dpdk/v25.11/source/lib/ethdev/rte_ethdev.h#L > 273 > > Good point, I was thinking of the per-queue stats and xstats. > > > While discussing details... > > Let's say a packet has 4 segments, and the driver only has 2 > descriptors remaining available. > > In that case, I think the driver should not consume the packet, but > leave it for the application to either drop it or retry transmitting it > later. > > Do we want to mention this case too, or is it a semi-obvious case of > the descriptor ring having no more room? > > There are also other cases of backpressure like when driver talks to > kernel and gets EAGAIN or EBUSY
