Hmm, that concern is not just limited to RDMA; any kind of shared memory communication across a trust boundary is vulnerable to info leaks in the padding of the struct. That does seem like a real issue.

Not sure what's the appropriate mitigation. Having to memset is a drag, and it's easy to forget to do it in some place or another. I'm tempted to say that you should only use packed structs for shared memory communication across trust boundaries.

Well, Infiniband is intended mainly for supercomputers. So security is of no real concern within the Imfiniband network as that is implicitly a trusted environment. Access comtrol to that network is the main security boundary.

Edit: Also, lots of simulation codes I am aware of tend to send flat arrays anyway. So I'd say that your concerns are mostly theoretical in nature.

RDMA, both roce and infiniband have some significant limitations, specifically at higher rates. But they're the best we have right now for direct dma.