An ULP is supposed to be able to replace a GSS rpc_auth object with
another GSS rpc_auth object using rpcauth_create(). However,
rpcauth_create() in 3.5 reliably fails with -EEXIST in this case.
This is because when gss_create() attempts to create the upcall pipes,
sometimes they are already there. For example if a pipe FS mount
event occurs, or a previous GSS flavor was in use for this rpc_clnt.
It turns out that's not the only problem here. While working on a
fix for the above problem, we noticed that replacing an rpc_clnt's
rpc_auth is not safe, since dereferencing the cl_auth field is not
protected in any way.
So we're deprecating the ability of rpcauth_create() to switch an
rpc_clnt's security flavor during normal operation. Instead, let's
add a fresh API that clones an rpc_clnt and gives the clone a new
flavor before it's used.
This makes immediate use of the new __rpc_clone_client() helper.
This can be used in a similar fashion to rpcauth_create() when a
client is hunting for the correct security flavor. Instead of
replacing an rpc_clnt's security flavor in a loop, the ULP replaces
the whole rpc_clnt.
To fix the -EEXIST problem, any ULP logic that relies on replacing
an rpc_clnt's rpc_auth with rpcauth_create() must be changed to use
this API instead.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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