fix(ncm): Return invalid NTBs to free list

[tore-espressif]

In case we received invalid datagram, we silently fail and the buffer was not returned to empty list -> it was lost.

If this happened more than CFG_TUD_NCM_OUT_NTB_N times, we run out of NTBs and all OUT transfers are NACKed.

Closes espressif/esp-usb#107

[tore-espressif]

@HiFiPhile @rgrr Could you please have a look?

[rgrr]

@HiFiPhile @rgrr Could you please have a look?

Seems reasonable to me. My memory is getting darker there, but AFAIR the buffer had been fetched before via recv_get_free_ntb(). And either it should go then into the ready list or back into the free list.

What I find a little surprising is, that bad blocks are arriving at that point. Never had that.

[tore-espressif]

Thanks for the confirmation!

What I find a little surprising is, that bad blocks are arriving at that point. Never had that.

I did not investigate why the datagrams are invalid; this is only a hot-fix. During upload throughput test (that is, NCM device is receiving with OUT transfers) I got several invalid datagrams per second...

[rgrr]

:

I did not investigate why the datagrams are invalid; this is only a hot-fix. During upload throughput test (that is, NCM device is receiving with OUT transfers) I got several invalid datagrams per second...

Out of curiosity: what platform did you use for emitting the test datagrams?

[tore-espressif]

As I said, I did not dig too deep; this was my setup

| Host PC (Win10) | <- USB -> | ESP32-S3| <- WiFi -> | Local network with internet access |

When I run speed test at speedtest.net I got this error often

[HiFiPhile]

Thanks for fixing it !