Description

When requesting 16 byte block size, the server will respond with an invalid packet.

Steps to reproduce the issue

• run examples/gcoap_fileserver:

  make -C examples/gcoap_fileserver PORT=tap1 all term
  

• create a dummy file

  echo "Hello World!" > examples/gcoap_fileserver/native/me
  

• Try to access the file via e.g. ncget with a 16 byte block size

   CFLAGS=-DCONFIG_NANOCOAP_BLOCKSIZE_DEFAULT=COAP_BLOCKSIZE_16 make -C tests/net/nanocoap_cli all term
   > ncget coap://[fe80::d07c:7cff:fe6d:9441]/vfs/me -
  

Expected results

We get the response in a single block

Actual results

We get the response in a single block, but there is some garbage after the block2 option:

gcoap_fileserver.pcapng.gz

Versions

RIOT master