SUNRPC: timeout and cancel TLS handshake with -ETIMEDOUT

JIRA: https://issues.redhat.com/browse/RHEL-67304

commit d7bdd84
Author: Benjamin Coddington <bcodding@redhat.com>
Date:   Fri Nov 15 08:59:36 2024 -0500

    SUNRPC: timeout and cancel TLS handshake with -ETIMEDOUT

    We've noticed a situation where an unstable TCP connection can cause the
    TLS handshake to timeout waiting for userspace to complete it.  When this
    happens, we don't want to return from xs_tls_handshake_sync() with zero, as
    this will cause the upper xprt to be set CONNECTED, and subsequent attempts
    to transmit will be returned with -EPIPE.  The sunrpc machine does not
    recover from this situation and will spin attempting to transmit.

    The return value of tls_handshake_cancel() can be used to detect a race
    with completion:

     * tls_handshake_cancel - cancel a pending handshake
     * Return values:
     *   %true - Uncompleted handshake request was canceled
     *   %false - Handshake request already completed or not found

    If true, we do not want the upper xprt to be connected, so return
    -ETIMEDOUT.  If false, its possible the handshake request was lost and
    that may be the reason for our timeout.  Again we do not want the upper
    xprt to be connected, so return -ETIMEDOUT.

    Ensure that we alway return an error from xs_tls_handshake_sync() if we
    call tls_handshake_cancel().

    Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
    Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
    Fixes: 75eb6af ("SUNRPC: Add a TCP-with-TLS RPC transport class")
    Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>

Author: bcodding-rh

net/sunrpc/xprtsock.c

@@ -2623,11 +2623,10 @@ static int xs_tls_handshake_sync(struct rpc_xprt *lower_xprt, struct xprtsec_par
 	rc = wait_for_completion_interruptible_timeout(&lower_transport->handshake_done,
 						       XS_TLS_HANDSHAKE_TO);
 	if (rc <= 0) {
-		if (!tls_handshake_cancel(sk)) {
-			if (rc == 0)
-				rc = -ETIMEDOUT;
-			goto out_put_xprt;
-		}
+		tls_handshake_cancel(sk);
+		if (rc == 0)
+			rc = -ETIMEDOUT;
+		goto out_put_xprt;
 	}
 
 	rc = lower_transport->xprt_err;