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 > > <jgunthorpe@xxxxxxxxxxxxxxxxxxxx> 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. > > Jason
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