RDMA/cma: Avoid GID lookups on iWARP devices

We would like to enable the use of siw on top of a VPN that is
constructed and managed via a tun device. That hasn't worked up
until now because ARPHRD_NONE devices (such as tun devices) have
no GID for the RDMA/core to look up.

But it turns out that the egress device has already been picked for
us -- no GID is necessary. addr_handler() just has to do the right
thing with it.

Link: https://lore.kernel.org/r/168960675257.3007.4737911174148394395.stgit@manet.1015granger.net
Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
index da54167..8bd6cb8 100644 (file)
--- a/drivers/infiniband/core/cma.c
+++ b/drivers/infiniband/core/cma.c
@@ -700,6 +700,27 @@ cma_validate_port(struct ib_device *device, u32 port,
        if ((dev_type != ARPHRD_INFINIBAND) && rdma_protocol_ib(device, port))
                goto out;
 
+       /*
+        * For drivers that do not associate more than one net device with
+        * their gid tables, such as iWARP drivers, it is sufficient to
+        * return the first table entry.
+        *
+        * Other driver classes might be included in the future.
+        */
+       if (rdma_protocol_iwarp(device, port)) {
+               sgid_attr = rdma_get_gid_attr(device, port, 0);
+               if (IS_ERR(sgid_attr))
+                       goto out;
+
+               rcu_read_lock();
+               ndev = rcu_dereference(sgid_attr->ndev);
+               if (!net_eq(dev_net(ndev), dev_addr->net) ||
+                   ndev->ifindex != bound_if_index)
+                       sgid_attr = ERR_PTR(-ENODEV);
+               rcu_read_unlock();
+               goto out;
+       }
+
        if (dev_type == ARPHRD_ETHER && rdma_protocol_roce(device, port)) {
                ndev = dev_get_by_index(dev_addr->net, bound_if_index);
                if (!ndev)