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Subject: Intel i40e rx burst API non-conformance?
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Date: Wed, 9 Jul 2025 16:59:51 +0200
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Thread-Topic: Intel i40e rx burst API non-conformance?
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From: =?iso-8859-1?Q?Morten_Br=F8rup?= <mb@smartsharesystems.com>
To: "Bruce Richardson" <bruce.richardson@intel.com>
Cc: <dev@dpdk.org>
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Looking at the i40e driver source code, I think it doesn't conform to =
the API when requesting small bursts.

Let's say the hardware has received 31 packets.
rte_eth_rx_burst(...,16) will return 16 packets and leave 15 in the =
driver's staging buffer (which has capacity for 32 packets).

Time passes, and more packets are received.

Now, rte_eth_rx_burst(...,16) will only return the 15 packets from the =
staging buffer, and not proceed to check for more [1].
It thereby (according to my interpretation of the API description) =
informs the application that no more packets are ready to be received, =
which is incorrect.

[1]: =
https://elixir.bootlin.com/dpdk/v25.07-rc2/source/drivers/net/intel/i40e/=
i40e_rxtx.c#L640

PS: I stumbled across this while reviewing how the very old 32 packet =
limit bugs (where it truncated large rx/tx requests to 32 packets) had =
been fixed.