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Subject[PATCH RFC] RDMA/CMA: Allocate PS_TCP ports from the host TCP port space.
Networking experts,

I'd like input on the patch below, and help in solving this bug
properly. iWARP devices that support both native stack TCP and iWARP
(aka RDMA over TCP/IP/Ethernet) connections on the same interface need
the fix below or some similar fix to the RDMA connection manager.

This is a BUG in the Linux RDMA-CMA code as it stands today.

Here is the issue:

Consider an mpi cluster running mvapich2. And the cluster runs
MPI/Sockets jobs concurrently with MPI/RDMA jobs. It is possible,
without the patch below, for MPI/Sockets processes to mistakenly get
incoming RDMA connections and vice versa. The way mvapich2 works is
that the ranks all bind and listen to a random port (retrying new random
ports if the bind fails with "in use"). Once they get a free port and
bind/listen, they advertise that port number to the peers to do
connection setup. Currently, without the patch below, the mpi/rdma
processes can end up binding/listening to the _same_ port number as the
mpi/sockets processes running over the native tcp stack. This is due to
duplicate port spaces for native stack TCP and the rdma cm's RDMA_PS_TCP
port space. If this happens, then the connections can get screwed up.

The correct solution in my mind is to use the host stack's TCP port
space for _all_ RDMA_PS_TCP port allocations. The patch below is a
minimal delta to unify the port spaces by using the kernel stack to bind
ports. This is done by allocating a kernel socket and binding to the
appropriate local addr/port. It also allows the kernel stack to pick
ephemeral ports by virtue of just passing in port 0 on the kernel bind
operation.

There has been a discussion already on the RDMA list if anyone is
interested:

http://www.mail-archive.com/general@lists.openfabrics.org/msg05162.html


Thanks,

Steve.


---

RDMA/CMA: Allocate PS_TCP ports from the host TCP port space.

This is needed for iwarp providers that support native and rdma
connections over the same interface.

Signed-off-by: Steve Wise <swise@opengridcomputing.com>
---

drivers/infiniband/core/cma.c | 27 ++++++++++++++++++++++++++-
1 files changed, 26 insertions(+), 1 deletions(-)

diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
index 9e0ab04..e4d2d7f 100644
--- a/drivers/infiniband/core/cma.c
+++ b/drivers/infiniband/core/cma.c
@@ -111,6 +111,7 @@ struct rdma_id_private {
struct rdma_cm_id id;

struct rdma_bind_list *bind_list;
+ struct socket *sock;
struct hlist_node node;
struct list_head list;
struct list_head listen_list;
@@ -695,6 +696,8 @@ static void cma_release_port(struct rdma
kfree(bind_list);
}
mutex_unlock(&lock);
+ if (id_priv->sock)
+ sock_release(id_priv->sock);
}

void rdma_destroy_id(struct rdma_cm_id *id)
@@ -1790,6 +1793,25 @@ static int cma_use_port(struct idr *ps,
return 0;
}

+static int cma_get_tcp_port(struct rdma_id_private *id_priv)
+{
+ int ret;
+ struct socket *sock;
+
+ ret = sock_create_kern(AF_INET, SOCK_STREAM, IPPROTO_TCP, &sock);
+ if (ret)
+ return ret;
+ ret = sock->ops->bind(sock,
+ (struct socketaddr *)&id_priv->id.route.addr.src_addr,
+ ip_addr_size(&id_priv->id.route.addr.src_addr));
+ if (ret) {
+ sock_release(sock);
+ return ret;
+ }
+ id_priv->sock = sock;
+ return 0;
+}
+
static int cma_get_port(struct rdma_id_private *id_priv)
{
struct idr *ps;
@@ -1801,6 +1823,9 @@ static int cma_get_port(struct rdma_id_p
break;
case RDMA_PS_TCP:
ps = &tcp_ps;
+ ret = cma_get_tcp_port(id_priv); /* Synch with native stack */
+ if (ret)
+ goto out;
break;
case RDMA_PS_UDP:
ps = &udp_ps;
@@ -1815,7 +1840,7 @@ static int cma_get_port(struct rdma_id_p
else
ret = cma_use_port(ps, id_priv);
mutex_unlock(&lock);
-
+out:
return ret;
}

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