RDMA/cma: Add multicast communication support

Extend rdma_cm to support multicast communication.  Multicast support
is added to the existing RDMA_PS_UDP port space, as well as a new
RDMA_PS_IPOIB port space.  The latter port space allows joining the
multicast groups used by IPoIB, which enables offloading IPoIB traffic
to a separate QP.  The port space determines the signature used in the
MGID when joining the group.  The newly added RDMA_PS_IPOIB also
allows for unicast operations, similar to RDMA_PS_UDP.

Supporting the RDMA_PS_IPOIB requires changing how UD QPs are initialized,
since we can no longer assume that the qkey is constant.  This requires
saving the Q_Key to use when attaching to a device, so that it is
available when creating the QP.  The Q_Key information is exported to
the user through the existing rdma_init_qp_attr() interface.

Multicast support is also exported to userspace through the rdma_ucm.

Signed-off-by: Roland Dreier <rolandd@cisco.com>

3 files changed, 33 insertions, 5 deletions

diff --git a/include/rdma/rdma_cm.h b/include/rdma/rdma_cm.h
index 36cd8a8526a0..2d6a7705eae7 100644
--- a/include/rdma/rdma_cm.h
+++ b/include/rdma/rdma_cm.h
@@ -52,10 +52,13 @@ enum rdma_cm_event_type {
         RDMA_CM_EVENT_ESTABLISHED,
         RDMA_CM_EVENT_DISCONNECTED,
         RDMA_CM_EVENT_DEVICE_REMOVAL,
+        RDMA_CM_EVENT_MULTICAST_JOIN,
+        RDMA_CM_EVENT_MULTICAST_ERROR
 };
 
 enum rdma_port_space {
         RDMA_PS_SDP  = 0x0001,
+        RDMA_PS_IPOIB= 0x0002,
         RDMA_PS_TCP  = 0x0106,
         RDMA_PS_UDP  = 0x0111,
         RDMA_PS_SCTP = 0x0183
@@ -294,5 +297,21 @@ int rdma_reject(struct rdma_cm_id *id, const void *private_data,
  */
 int rdma_disconnect(struct rdma_cm_id *id);
 
-#endif /* RDMA_CM_H */
+/**
+ * rdma_join_multicast - Join the multicast group specified by the given
+ *   address.
+ * @id: Communication identifier associated with the request.
+ * @addr: Multicast address identifying the group to join.
+ * @context: User-defined context associated with the join request, returned
+ * to the user through the private_data pointer in multicast events.
+ */
+int rdma_join_multicast(struct rdma_cm_id *id, struct sockaddr *addr,
+                        void *context);
 
+/**
+ * rdma_leave_multicast - Leave the multicast group specified by the given
+ *   address.
+ */
+void rdma_leave_multicast(struct rdma_cm_id *id, struct sockaddr *addr);
+
+#endif /* RDMA_CM_H */
diff --git a/include/rdma/rdma_cm_ib.h b/include/rdma/rdma_cm_ib.h
index 9b176df1d667..950424b38f16 100644
--- a/include/rdma/rdma_cm_ib.h
+++ b/include/rdma/rdma_cm_ib.h
@@ -44,7 +44,7 @@
 int rdma_set_ib_paths(struct rdma_cm_id *id,
                       struct ib_sa_path_rec *path_rec, int num_paths);
 
-/* Global qkey for UD QPs and multicast groups. */
-#define RDMA_UD_QKEY 0x01234567
+/* Global qkey for UDP QPs and multicast groups. */
+#define RDMA_UDP_QKEY 0x01234567
 
 #endif /* RDMA_CM_IB_H */
diff --git a/include/rdma/rdma_user_cm.h b/include/rdma/rdma_user_cm.h
index 9572ab8eeac1..f632b0c007c9 100644
--- a/include/rdma/rdma_user_cm.h
+++ b/include/rdma/rdma_user_cm.h
@@ -38,7 +38,7 @@
 #include <rdma/ib_user_verbs.h>
 #include <rdma/ib_user_sa.h>
 
-#define RDMA_USER_CM_ABI_VERSION        3
+#define RDMA_USER_CM_ABI_VERSION        4
 
 #define RDMA_MAX_PRIVATE_DATA           256
 
@@ -58,7 +58,9 @@ enum {
         RDMA_USER_CM_CMD_GET_EVENT,
         RDMA_USER_CM_CMD_GET_OPTION,
         RDMA_USER_CM_CMD_SET_OPTION,
-        RDMA_USER_CM_CMD_NOTIFY
+        RDMA_USER_CM_CMD_NOTIFY,
+        RDMA_USER_CM_CMD_JOIN_MCAST,
+        RDMA_USER_CM_CMD_LEAVE_MCAST
 };
 
 /*
@@ -188,6 +190,13 @@ struct rdma_ucm_notify {
         __u32 event;
 };
 
+struct rdma_ucm_join_mcast {
+        __u64 response;         /* rdma_ucm_create_id_resp */
+        __u64 uid;
+        struct sockaddr_in6 addr;
+        __u32 id;
+};
+
 struct rdma_ucm_get_event {
         __u64 response;
 };