nbd_get_tls_negotiated3

Usage

 #include <libnbd.h>
 int nbd_get_tls_negotiated (
       struct nbd_handle *h
     );

Overview

After connecting you may call this to find out if the connection is using TLS.

This is normally useful only if you set the TLS request mode to "LIBNBD_TLS_ALLOW" (see nbd_set_tls(3)), because in this mode we try to use TLS but fall back to unencrypted if it was not available. This function will tell you if TLS was negotiated or not.

In "LIBNBD_TLS_REQUIRE" mode (the most secure) the connection would have failed if TLS could not be negotiated. With "LIBNBD_TLS_DISABLE" mode, TLS is not tried automatically; but if the NBD server uses the less-common "SELECTIVETLS" mode, this function reports whether a manual nbd_opt_starttls(3) enabled TLS or if the connection is still plaintext.

Return value

This call returns a boolean value.

Errors

On error -1 is returned.

Refer to "ERROR HANDLING" in libnbd(3) for how to get further details of the error.

The following parameters must not be NULL: "h". For more information see "Non-NULL parameters" in libnbd(3).

Handle state

nbd_get_tls_negotiated can be called when the handle is in the following states:

 ┌─────────────────────────────────────┬─────────────────────────┐
 │ Handle created, before connecting   │ ❌ error                │
 │ Connecting                          │ ❌ error                │
 │ Connecting & handshaking (opt_mode) │ ✅ allowed              │
 │ Connected to the server             │ ✅ allowed              │
 │ Connection shut down                │ ✅ allowed              │
 │ Handle dead                         │ ❌ error                │
 └─────────────────────────────────────┴─────────────────────────┘

Version

This function first appeared in libnbd 1.2.

If you need to test if this function is available at compile time check if the following macro is defined:

 #define LIBNBD_HAVE_NBD_GET_TLS_NEGOTIATED 1