Re: [PATCH RFC iproute2-next 1/2] rdma: add 'link add/delete' commands

[Leon Romanovsky <leon@kernel.org>]

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On Wed, Nov 28, 2018 at 10:02:04PM +0200, Leon Romanovsky wrote:
> On Wed, Nov 28, 2018 at 01:34:14PM -0600, Steve Wise wrote:
> > ...
> >
> > >>> +	rd_prepare_msg(rd, RDMA_NLDEV_CMD_NEWLINK, &seq,
> > >>> +		       (NLM_F_REQUEST | NLM_F_ACK));
> > >>> +	mnl_attr_put_strz(rd->nlh, RDMA_NLDEV_ATTR_DEV_NAME, name);
> > >>> +	mnl_attr_put_strz(rd->nlh, RDMA_NLDEV_ATTR_LINK_TYPE, type);
> > >>> +	mnl_attr_put_strz(rd->nlh, RDMA_NLDEV_ATTR_NDEV_NAME, dev);
> > >>> +	ret = rd_send_msg(rd);
> > >>> +	if (ret)
> > >>> +		return ret;
> > >>> +
> > >>> +	ret = rd_recv_msg(rd, link_add_parse_cb, rd, seq);
> > >>> +	if (ret)
> > >>> +		perror(NULL);
> > >> Why do you need rd_recv_msg()? I think that it is not needed, at least
> > >> for rename, I didn't need it.
> > >> https://git.kernel.org/pub/scm/network/iproute2/iproute2-next.git/tree/rdma/dev.c#n244
> > > To get the response of if it was successfully added.  It provides the
> > > errno value.
> > If I don't do the rd_recv_msg, then adding the same name twice fails
> > without any error notification.  Ditto for deleting a non-existent
> > link.  So the rd_recv_msg() allows getting the failure reason (and
> > detecting the failure). 
> >
>
> Shouldn't extack provide such information as part of NLM_F_ACK flag?
>
> just shooting into the air, will take more close look tomorrow.

OK, it was easier than I thought.

You are right, need both send and receive to get the reason.

Can you prepare general function and update rename part too?
Something like send_receive(...) with dummy callback for receive path.

Thanks

>
> Thanks
>
> >



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