How to prevent applications from passing IOvecs to a provider that doesn’t support it ?

[goudeaus]

Hi,
We are developing in libfabric (version 1.18) a provider that currently does not support IOvecs.
Hence, when negociating capabilities with applications, we set iov_limit=1 in relevant fields (rx, tx, ...) of fi_info structure.
With an application like Intel MPI 2021.9.0, the negociation sequence goes as follows:

1. The application calls fi_getinfo() with null hints
2. Our provider replies an fi_info structure with all iov_limit fields set to 1.
3. The application calls fi_getinfo() again with hints containing iov_limit fields set to 0 or 1, seemingly indicating
   that the application is able to deal with a provider not supporting IOVecs.
4. Our provider again replies an fi_info structure with all iov_limit fields set to 1.

However, we notice that the application (Intel MPI) will still call fi_send() interfaces with iov_count larger than 1, eg iov_count = 3,
which currently breaks our provider. Is there something we may have missed in the negociation process?