* ULONG BITCOUNT UNDERRUN bitfields add up to less than 32
* ULONG VALUE NEGATIVE attempt convert -ve integers to ulong
* ULONG VALUE OVERFLOW converted value does not fit in result
+ * TUNTAP IFNAME LENGTH tun/tap interface name too long
+ * TUNTAP MTU OVERRUN tun/tap mtu limited to 2^16 bytes
*
* Refs: HMAC: RFC2104
*/