Re: [RFC 2/4] test: add test for af_packet

[Stephen Hemminger <stephen@networkplumber.org>]

On Wed, 28 Jan 2026 12:36:41 -0800
Scott Mitchell <scott.k.mitch1@gmail.com> wrote:

> Awesome! Some suggestions below but could easily be done in a followup
> for incremental progress.
> 
> > +       /* TX burst */
> > +       nb_tx = rte_eth_tx_burst(port_id, 0, bufs, BURST_SIZE);
> > +
> > +       /* Free any unsent mbufs */
> > +       for (i = nb_tx; i < BURST_SIZE; i++)
> > +               rte_pktmbuf_free(bufs[i]);
> > +
> > +       /* Small delay to allow stats update */
> > +       rte_delay_us_block(1000);  
> 
> Consider polling rte_eth_stats_get at a more frequent interval, break
> when you see status update, and apply overall timeout/repeat limit ->
> can make test more reliable and take less time when data is usually
> available quickly
> 
> > +       /* Try to receive packets (non-blocking) */
> > +       nb_rx = rte_eth_rx_burst(port_id, 0, bufs, BURST_SIZE);
> > +
> > +       /* Free any received mbufs */
> > +       for (i = 0; i < nb_rx; i++)
> > +               rte_pktmbuf_free(bufs[i]);
> > +
> > +       /* RX from tap interface without external traffic will return 0 */
> > +       /* This test just verifies the RX path doesn't crash */  
> 
> Consider adding a test that round trips data (tx -> rx) to exercise
> the read loop.
> 
> > +       /* Get current MTU */
> > +       ret = rte_eth_dev_get_mtu(port_id, &mtu);
> > +       TEST_ASSERT(ret == 0, "Failed to get MTU");
> > +
> > +       /* Try to set a smaller MTU */
> > +       ret = rte_eth_dev_set_mtu(port_id, 1400);  
> 
> Consider getting the min/max supported MTU and setting it to verify it
> works. My patch fixed some issues related to MTU and overhead of
> frames that may have been caught by this.
> 
> > +
> > +       /* Reset stats */
> > +       ret = rte_eth_stats_reset(port_id);
> > +       TEST_ASSERT(ret == 0, "Failed to reset stats");  
> 
> Consider enhancing to introduce multiple threads (writer and reader)
> to replicate
> 
> > +static int
> > +test_af_packet_multi_queue(void)  
> 
> Consider sharing rx/tx logic in common functions for single/multi-queue cases.

Wow, AI could take that feedback and revise for a new version.