When a `P_CONTROL_WKC_V1` is received, OpenVPN sets up tls-crypt-v2 keys. Due to a small oversight, we try to setup tls-crypt-v2 again if receive another `P_CONTROL_WKC_V1`. Typically this is not harmful if the `P_CONTROL_WKC_V1` is actually valid.

But in environments where the duplicated and mangled packets, the key setup via `P_CONTROL_WKC_V1` ends up in an unexpected state resulting the OpenVPN server process to `assert()` and stops running. In practice resulting in a remote DoS attack vector.

Release note: [«OpenVPN 2.6.14 released»](https://www.mail-archive.com/openvpn-announce@lists.sourceforge.net/msg00142.html)