verifyCookie

bool verifyCookie(const(ubyte)[]  cookie,  const(ubyte)[]  serverSecret,
       DatagramEndpoint clientAddr,  const(ubyte)[]  clientRandom)

Verifies a cookie received from a client.

Regenerates the expected cookie from the client's address and random, then performs a constant-time comparison to prevent timing attacks.

`cookie`	The cookie received from the client.
`serverSecret`	The server's secret key.
`clientAddr`	The client's network address.
`clientRandom`	The 32-byte ClientHello random value.

true if the cookie is valid, false otherwise.