Re: Netlink messages without NLM_F_REQUEST flag

On Wed, Jun 07, 2017 at 07:43:44PM +0300, Leon Romanovsky wrote:

On Wed, Jun 7, 2017 at 7:37 PM, Jason Gunthorpe
[off-list ref] wrote:

quoted

On Wed, Jun 07, 2017 at 07:19:01PM +0300, Leon Romanovsky wrote:

quoted

It makes me wonder if it is expected behavior for
ibnl_rcv_reply_skb() to handle !NLM_F_REQUEST messages and do we
really need it? What are the scenarios?  In my use case, which is
for sure different from yours, I'm always setting NLM_F_REQUEST
while communicating with kernel.

If I recall the user space SA code issues REQUESTS from the kernel to
userspace, so userspace returns with the response format. This is
abnormal for netlink hence the special function.

In netlink semantics, kernel side is supposed to send netlink
notification message and userspace is supposed to send REQUEST.

That pattern is for async communications, the SA stuff needs a sync
protocol, unfortunately.

Jason
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