sys/net/nanocoap: add and use coap_get_response_hdr_len() #20950
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Before, handlers writing blockwise transfer assumed that the response
header length will match the request header length. This is true for
UDP, but not for TCP: The CoAP over TCP header contains a Len field,
that gets extended for larger messages. Since the reply often is indeed
larger than the request, this is indeed often the case for CoAP over
TCP.
Note: Right now, no CoAP over TCP implementation is upstream. However,
getting rid of incorrect assumptions now will make life easier
later on.
maribu
added
Process: API change
github-actions
bot
added
Area: network
benpicco
approved these changes
Nov 5, 2024
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Thx :) |
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Contribution description
Before, handlers writing blockwise transfer assumed that the response header length will match the request header length. This is true for UDP, but not for TCP: The CoAP over TCP header contains a Len field, that gets extended for larger messages. Since the reply often is indeed larger than the request, this is indeed often the case for CoAP over TCP.
Note
Right now, no CoAP over TCP implementation is upstream. However, getting rid of incorrect assumptions now will make life easier later on.
Testing procedure
This will not change generated binaries, as right now the implementation just calls the same function that was used before. After all, for CoAP over UDP the assumption that request and response header match in size is valid.
Issues/PRs references
Relevant for #20900