IB/cm: Share listening CM IDs

Enabling network namespaces for RDMA CM will allow processes on different
namespaces to listen on the same port. In order to leave namespace support
out of the CM layer, this requires that multiple RDMA CM IDs will be able
to share a single CM ID.

This patch adds infrastructure to retrieve an existing listening ib_cm_id,
based on its device and service ID, or create a new one if one does not
already exist. It also adds a reference count for such instances
(cm_id_private.listen_sharecount), and prevents cm_destroy_id from
destroying a CM if it is still shared. See the relevant discussion [1].

[1] Re: [PATCH v3 for-next 05/13] IB/cm: Reference count ib_cm_ids
    http://www.spinics.net/lists/netdev/msg328860.html

Reviewed-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: Haggai Eran <haggaie@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/rdma/ib_cm.h b/include/rdma/ib_cm.h
index 1b567bb..9cc496e 100644
--- a/include/rdma/ib_cm.h
+++ b/include/rdma/ib_cm.h
@@ -362,6 +362,10 @@ struct ib_cm_compare_data {
 int ib_cm_listen(struct ib_cm_id *cm_id, __be64 service_id, __be64 service_mask,
 		 struct ib_cm_compare_data *compare_data);
 
+struct ib_cm_id *ib_cm_insert_listen(struct ib_device *device,
+				     ib_cm_handler cm_handler,
+				     __be64 service_id);
+
 struct ib_cm_req_param {
 	struct ib_sa_path_rec	*primary_path;
 	struct ib_sa_path_rec	*alternate_path;