On Wed, Dec 11, 2019 at 08:31:18PM +0100, Håkon Bugge wrote: > > > > On 11 Dec 2019, at 14:13, Håkon Bugge <haakon.bugge@xxxxxxxxxx> wrote: > > > > > > > >> On 11 Dec 2019, at 13:39, Leon Romanovsky <leon@xxxxxxxxxx> wrote: > >> > >> On Wed, Dec 11, 2019 at 11:34:00AM +0100, Håkon Bugge wrote: > >>> In rdma_nl_rcv_skb(), the local variable err is assigned the return > >>> value of the supplied callback function, which could be one of > >>> ib_nl_handle_resolve_resp(), ib_nl_handle_set_timeout(), or > >>> ib_nl_handle_ip_res_resp(). These three functions all return skb->len > >>> on success. > >>> > >>> rdma_nl_rcv_skb() is merely a copy of netlink_rcv_skb(). The callback > >>> functions used by the latter have the convention: "Returns 0 on > >>> success or a negative error code". > >>> > >>> In particular, the statement (equal for both functions): > >>> > >>> if (nlh->nlmsg_flags & NLM_F_ACK || err) > >>> > >>> implies that rdma_nl_rcv_skb() always will ack a message, independent > >>> of the NLM_F_ACK being set in nlmsg_flags or not. > >> > >> The more accurate description is that rdma_nl_rcv_skb() always generates > >> NLMSG_ERROR without relation to NLM_F_ACK flag. The NLM_F_ACK flag is > >> requested to get acknowledges for the success. > > > Yes. And when, lets say a legitimate path record response, containing N positive bytes, is sent back from ibacm to the kernel, rdma_nl_rcv_skb() think this is an error, due to "if (nlh->nlmsg_flags & NLM_F_ACK || err)" _and_ ib_nl_handle_resolve_resp() returning N. How did you test this patch? Do we have open-source applications which don't set NLM_F_ACK for ib_nl_*() calls? Thanks > > Thxs, Håkon > > > >> > >>> > >>> The fix could be to change the above statement, but it is better to > >>> keep the two *_rcv_skb() functions equal in this respect and instead > >>> change the callback functions in the rdma subsystem to the correct > >>> convention. > >> > >> AFAIR, RTNETLINK has the same implementation as RDMA netlink. > > > > With the exception of the callback functions, as noted above. > > > > > > Thxs, Håkon > > > >> > >> Thanks > > >
