2 files changed, 13 insertions, 0 deletions

diff --git a/lisp/net/tramp-sh.el b/lisp/net/tramp-sh.el
index f69859ddb10..3ed2cd324e8 100644
--- a/lisp/net/tramp-sh.el
+++ b/lisp/net/tramp-sh.el
@@ -4285,6 +4285,10 @@ Gateway hops are already opened."
           (or
            ;; There are multi-hops.
            (cdr target-alist)
+           ;; This method explicitly has an explicit allowability check.
+           (let ((checker (tramp-get-method-parameter
+                           method 'tramp-hostname-checker)))
+             (when checker (funcall checker v host method) t))
            ;; The host name is used for the remote shell command.
            (member
             '("%h") (tramp-get-method-parameter method 'tramp-login-args))
diff --git a/lisp/net/tramp.el b/lisp/net/tramp.el
index 2cbaf4a1636..f076f043c5f 100644
--- a/lisp/net/tramp.el
+++ b/lisp/net/tramp.el
@@ -265,6 +265,15 @@ pair of the form (KEY VALUE).  The following KEYs are defined:
     In general, the global default value shall be used, but for
     some methods, like \"su\" or \"sudo\", a shorter timeout
     might be desirable.
+  * `tramp-hostname-checker'
+    This is a function that tramp calls while setting
+    up a connection.  It is called with three arguments:
+    the target, the host, and the method description.  If
+    the hostname is unacceptable, this function should signal
+    using `tramp-error'.  If a method does not provide
+    a value here, then Tramp looks at whether the method's
+    login program uses a \"%h\" parameter.  If not, then Tramp
+    requires that the given hostname match `tramp-local-host-regexp'. 
 
 What does all this mean?  Well, you should specify `tramp-login-program'
 for all methods; this program is used to log in to the remote site.  Then,