Block transfer resend is ignored by client, halts transfer.

[pehrnord]

https://github.com/eclipse/wakaama/blob/c5c6d321d50ff0534a390acc2bd9db7de48da41d/coap/block.c#L181

Client side: When receiving a resend of a previously handled block, it is ignored. This halts the block transfer, since the server will keep re-sending the block and then give up. Triggered when client response to block transfer message is lost (?). Should instead return COAP_231_CONTINUE?

[sbernard31]

Is it possible to provide a wireshark capture to be sure that we understand the issue correctly.

[qleisan]

210323_555_recreation_attempt.pcapng.zip

Client side: When receiving a resend of a previously handled block, it is ignored. This halts the block transfer, since the server will keep re-sending the block and then give up. Triggered when client response to block transfer message is lost (?).

Attempted to recreate this issue without success, see attached wireshark log.

• client connects
• server writes data to client object, block transfer is triggered
• first client ACK (2.31) is dropped before it is processed by server (hack)
• server retransmits - everything works fine
• client disconnects

[qleisan]

210323_555_recreation_attempt_2.pcapng.zip

New attempt after code inspection, this time drop ACK from second (not first) block transfer packet. Problem recreated!