> > On Wed, Jun 07, 2017 at 10:47:50AM -0600, Jason Gunthorpe wrote: > > On Wed, Jun 07, 2017 at 07:43:44PM +0300, Leon Romanovsky wrote: > > > On Wed, Jun 7, 2017 at 7:37 PM, Jason Gunthorpe > > > <jguntho...@obsidianresearch.com> wrote: > > > > On Wed, Jun 07, 2017 at 07:19:01PM +0300, Leon Romanovsky wrote: > > > >> 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. > > There is special flag NLM_F_ACK for it and userspace will set > NLM_F_REQUEST | NLM_F_ACK once synchronization is needed. >
Reference? >From my understanding, NLM_F_REQUEST | NLM_F_ACK is simply requesting an ack >from the kernel on a request. In our case the message is a response to the >kernel request. Ira
